1 //===- LoopVectorize.cpp - A Loop Vectorizer ------------------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This is the LLVM loop vectorizer. This pass modifies 'vectorizable' loops
11 // and generates target-independent LLVM-IR.
12 // The vectorizer uses the TargetTransformInfo analysis to estimate the costs
13 // of instructions in order to estimate the profitability of vectorization.
15 // The loop vectorizer combines consecutive loop iterations into a single
16 // 'wide' iteration. After this transformation the index is incremented
17 // by the SIMD vector width, and not by one.
19 // This pass has three parts:
20 // 1. The main loop pass that drives the different parts.
21 // 2. LoopVectorizationLegality - A unit that checks for the legality
22 // of the vectorization.
23 // 3. InnerLoopVectorizer - A unit that performs the actual
24 // widening of instructions.
25 // 4. LoopVectorizationCostModel - A unit that checks for the profitability
26 // of vectorization. It decides on the optimal vector width, which
27 // can be one, if vectorization is not profitable.
29 //===----------------------------------------------------------------------===//
31 // The reduction-variable vectorization is based on the paper:
32 // D. Nuzman and R. Henderson. Multi-platform Auto-vectorization.
34 // Variable uniformity checks are inspired by:
35 // Karrenberg, R. and Hack, S. Whole Function Vectorization.
37 // Other ideas/concepts are from:
38 // A. Zaks and D. Nuzman. Autovectorization in GCC-two years later.
40 // S. Maleki, Y. Gao, M. Garzaran, T. Wong and D. Padua. An Evaluation of
41 // Vectorizing Compilers.
43 //===----------------------------------------------------------------------===//
45 #define LV_NAME "loop-vectorize"
46 #define DEBUG_TYPE LV_NAME
48 #include "llvm/Transforms/Vectorize.h"
49 #include "llvm/ADT/DenseMap.h"
50 #include "llvm/ADT/EquivalenceClasses.h"
51 #include "llvm/ADT/MapVector.h"
52 #include "llvm/ADT/SetVector.h"
53 #include "llvm/ADT/SmallPtrSet.h"
54 #include "llvm/ADT/SmallSet.h"
55 #include "llvm/ADT/SmallVector.h"
56 #include "llvm/ADT/StringExtras.h"
57 #include "llvm/Analysis/AliasAnalysis.h"
58 #include "llvm/Analysis/Dominators.h"
59 #include "llvm/Analysis/LoopInfo.h"
60 #include "llvm/Analysis/LoopIterator.h"
61 #include "llvm/Analysis/LoopPass.h"
62 #include "llvm/Analysis/ScalarEvolution.h"
63 #include "llvm/Analysis/ScalarEvolutionExpander.h"
64 #include "llvm/Analysis/ScalarEvolutionExpressions.h"
65 #include "llvm/Analysis/TargetTransformInfo.h"
66 #include "llvm/Analysis/ValueTracking.h"
67 #include "llvm/Analysis/Verifier.h"
68 #include "llvm/IR/Constants.h"
69 #include "llvm/IR/DataLayout.h"
70 #include "llvm/IR/DerivedTypes.h"
71 #include "llvm/IR/Function.h"
72 #include "llvm/IR/IRBuilder.h"
73 #include "llvm/IR/Instructions.h"
74 #include "llvm/IR/IntrinsicInst.h"
75 #include "llvm/IR/LLVMContext.h"
76 #include "llvm/IR/Module.h"
77 #include "llvm/IR/Type.h"
78 #include "llvm/IR/Value.h"
79 #include "llvm/Pass.h"
80 #include "llvm/Support/CommandLine.h"
81 #include "llvm/Support/Debug.h"
82 #include "llvm/Support/PatternMatch.h"
83 #include "llvm/Support/raw_ostream.h"
84 #include "llvm/Support/ValueHandle.h"
85 #include "llvm/Target/TargetLibraryInfo.h"
86 #include "llvm/Transforms/Scalar.h"
87 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
88 #include "llvm/Transforms/Utils/Local.h"
93 using namespace llvm::PatternMatch;
95 static cl::opt<unsigned>
96 VectorizationFactor("force-vector-width", cl::init(0), cl::Hidden,
97 cl::desc("Sets the SIMD width. Zero is autoselect."));
99 static cl::opt<unsigned>
100 VectorizationUnroll("force-vector-unroll", cl::init(0), cl::Hidden,
101 cl::desc("Sets the vectorization unroll count. "
102 "Zero is autoselect."));
105 EnableIfConversion("enable-if-conversion", cl::init(true), cl::Hidden,
106 cl::desc("Enable if-conversion during vectorization."));
108 /// We don't vectorize loops with a known constant trip count below this number.
109 static cl::opt<unsigned>
110 TinyTripCountVectorThreshold("vectorizer-min-trip-count", cl::init(16),
112 cl::desc("Don't vectorize loops with a constant "
113 "trip count that is smaller than this "
116 /// We don't unroll loops with a known constant trip count below this number.
117 static const unsigned TinyTripCountUnrollThreshold = 128;
119 /// When performing memory disambiguation checks at runtime do not make more
120 /// than this number of comparisons.
121 static const unsigned RuntimeMemoryCheckThreshold = 8;
123 /// Maximum simd width.
124 static const unsigned MaxVectorWidth = 64;
126 /// Maximum vectorization unroll count.
127 static const unsigned MaxUnrollFactor = 16;
129 /// The cost of a loop that is considered 'small' by the unroller.
130 static const unsigned SmallLoopCost = 20;
134 // Forward declarations.
135 class LoopVectorizationLegality;
136 class LoopVectorizationCostModel;
138 /// InnerLoopVectorizer vectorizes loops which contain only one basic
139 /// block to a specified vectorization factor (VF).
140 /// This class performs the widening of scalars into vectors, or multiple
141 /// scalars. This class also implements the following features:
142 /// * It inserts an epilogue loop for handling loops that don't have iteration
143 /// counts that are known to be a multiple of the vectorization factor.
144 /// * It handles the code generation for reduction variables.
145 /// * Scalarization (implementation using scalars) of un-vectorizable
147 /// InnerLoopVectorizer does not perform any vectorization-legality
148 /// checks, and relies on the caller to check for the different legality
149 /// aspects. The InnerLoopVectorizer relies on the
150 /// LoopVectorizationLegality class to provide information about the induction
151 /// and reduction variables that were found to a given vectorization factor.
152 class InnerLoopVectorizer {
154 InnerLoopVectorizer(Loop *OrigLoop, ScalarEvolution *SE, LoopInfo *LI,
155 DominatorTree *DT, DataLayout *DL,
156 const TargetLibraryInfo *TLI, unsigned VecWidth,
157 unsigned UnrollFactor)
158 : OrigLoop(OrigLoop), SE(SE), LI(LI), DT(DT), DL(DL), TLI(TLI),
159 VF(VecWidth), UF(UnrollFactor), Builder(SE->getContext()), Induction(0),
160 OldInduction(0), WidenMap(UnrollFactor) {}
162 // Perform the actual loop widening (vectorization).
163 void vectorize(LoopVectorizationLegality *Legal) {
164 // Create a new empty loop. Unlink the old loop and connect the new one.
165 createEmptyLoop(Legal);
166 // Widen each instruction in the old loop to a new one in the new loop.
167 // Use the Legality module to find the induction and reduction variables.
168 vectorizeLoop(Legal);
169 // Register the new loop and update the analysis passes.
173 virtual ~InnerLoopVectorizer() {}
176 /// A small list of PHINodes.
177 typedef SmallVector<PHINode*, 4> PhiVector;
178 /// When we unroll loops we have multiple vector values for each scalar.
179 /// This data structure holds the unrolled and vectorized values that
180 /// originated from one scalar instruction.
181 typedef SmallVector<Value*, 2> VectorParts;
183 // When we if-convert we need create edge masks. We have to cache values so
184 // that we don't end up with exponential recursion/IR.
185 typedef DenseMap<std::pair<BasicBlock*, BasicBlock*>,
186 VectorParts> EdgeMaskCache;
188 /// Add code that checks at runtime if the accessed arrays overlap.
189 /// Returns the comparator value or NULL if no check is needed.
190 Instruction *addRuntimeCheck(LoopVectorizationLegality *Legal,
192 /// Create an empty loop, based on the loop ranges of the old loop.
193 void createEmptyLoop(LoopVectorizationLegality *Legal);
194 /// Copy and widen the instructions from the old loop.
195 virtual void vectorizeLoop(LoopVectorizationLegality *Legal);
197 /// \brief The Loop exit block may have single value PHI nodes where the
198 /// incoming value is 'Undef'. While vectorizing we only handled real values
199 /// that were defined inside the loop. Here we fix the 'undef case'.
203 /// A helper function that computes the predicate of the block BB, assuming
204 /// that the header block of the loop is set to True. It returns the *entry*
205 /// mask for the block BB.
206 VectorParts createBlockInMask(BasicBlock *BB);
207 /// A helper function that computes the predicate of the edge between SRC
209 VectorParts createEdgeMask(BasicBlock *Src, BasicBlock *Dst);
211 /// A helper function to vectorize a single BB within the innermost loop.
212 void vectorizeBlockInLoop(LoopVectorizationLegality *Legal, BasicBlock *BB,
215 /// Vectorize a single PHINode in a block. This method handles the induction
216 /// variable canonicalization. It supports both VF = 1 for unrolled loops and
217 /// arbitrary length vectors.
218 void widenPHIInstruction(Instruction *PN, VectorParts &Entry,
219 LoopVectorizationLegality *Legal,
220 unsigned UF, unsigned VF, PhiVector *PV);
222 /// Insert the new loop to the loop hierarchy and pass manager
223 /// and update the analysis passes.
224 void updateAnalysis();
226 /// This instruction is un-vectorizable. Implement it as a sequence
228 virtual void scalarizeInstruction(Instruction *Instr);
230 /// Vectorize Load and Store instructions,
231 virtual void vectorizeMemoryInstruction(Instruction *Instr,
232 LoopVectorizationLegality *Legal);
234 /// Create a broadcast instruction. This method generates a broadcast
235 /// instruction (shuffle) for loop invariant values and for the induction
236 /// value. If this is the induction variable then we extend it to N, N+1, ...
237 /// this is needed because each iteration in the loop corresponds to a SIMD
239 virtual Value *getBroadcastInstrs(Value *V);
241 /// This function adds 0, 1, 2 ... to each vector element, starting at zero.
242 /// If Negate is set then negative numbers are added e.g. (0, -1, -2, ...).
243 /// The sequence starts at StartIndex.
244 virtual Value *getConsecutiveVector(Value* Val, int StartIdx, bool Negate);
246 /// When we go over instructions in the basic block we rely on previous
247 /// values within the current basic block or on loop invariant values.
248 /// When we widen (vectorize) values we place them in the map. If the values
249 /// are not within the map, they have to be loop invariant, so we simply
250 /// broadcast them into a vector.
251 VectorParts &getVectorValue(Value *V);
253 /// Generate a shuffle sequence that will reverse the vector Vec.
254 virtual Value *reverseVector(Value *Vec);
256 /// This is a helper class that holds the vectorizer state. It maps scalar
257 /// instructions to vector instructions. When the code is 'unrolled' then
258 /// then a single scalar value is mapped to multiple vector parts. The parts
259 /// are stored in the VectorPart type.
261 /// C'tor. UnrollFactor controls the number of vectors ('parts') that
263 ValueMap(unsigned UnrollFactor) : UF(UnrollFactor) {}
265 /// \return True if 'Key' is saved in the Value Map.
266 bool has(Value *Key) const { return MapStorage.count(Key); }
268 /// Initializes a new entry in the map. Sets all of the vector parts to the
269 /// save value in 'Val'.
270 /// \return A reference to a vector with splat values.
271 VectorParts &splat(Value *Key, Value *Val) {
272 VectorParts &Entry = MapStorage[Key];
273 Entry.assign(UF, Val);
277 ///\return A reference to the value that is stored at 'Key'.
278 VectorParts &get(Value *Key) {
279 VectorParts &Entry = MapStorage[Key];
282 assert(Entry.size() == UF);
287 /// The unroll factor. Each entry in the map stores this number of vector
291 /// Map storage. We use std::map and not DenseMap because insertions to a
292 /// dense map invalidates its iterators.
293 std::map<Value *, VectorParts> MapStorage;
296 /// The original loop.
298 /// Scev analysis to use.
306 /// Target Library Info.
307 const TargetLibraryInfo *TLI;
309 /// The vectorization SIMD factor to use. Each vector will have this many
314 /// The vectorization unroll factor to use. Each scalar is vectorized to this
315 /// many different vector instructions.
318 /// The builder that we use
321 // --- Vectorization state ---
323 /// The vector-loop preheader.
324 BasicBlock *LoopVectorPreHeader;
325 /// The scalar-loop preheader.
326 BasicBlock *LoopScalarPreHeader;
327 /// Middle Block between the vector and the scalar.
328 BasicBlock *LoopMiddleBlock;
329 ///The ExitBlock of the scalar loop.
330 BasicBlock *LoopExitBlock;
331 ///The vector loop body.
332 BasicBlock *LoopVectorBody;
333 ///The scalar loop body.
334 BasicBlock *LoopScalarBody;
335 /// A list of all bypass blocks. The first block is the entry of the loop.
336 SmallVector<BasicBlock *, 4> LoopBypassBlocks;
338 /// The new Induction variable which was added to the new block.
340 /// The induction variable of the old basic block.
341 PHINode *OldInduction;
342 /// Holds the extended (to the widest induction type) start index.
344 /// Maps scalars to widened vectors.
346 EdgeMaskCache MaskCache;
349 class InnerLoopUnroller : public InnerLoopVectorizer {
351 InnerLoopUnroller(Loop *OrigLoop, ScalarEvolution *SE, LoopInfo *LI,
352 DominatorTree *DT, DataLayout *DL,
353 const TargetLibraryInfo *TLI, unsigned UnrollFactor) :
354 InnerLoopVectorizer(OrigLoop, SE, LI, DT, DL, TLI, 1, UnrollFactor) { }
357 virtual void scalarizeInstruction(Instruction *Instr);
358 virtual void vectorizeMemoryInstruction(Instruction *Instr,
359 LoopVectorizationLegality *Legal);
360 virtual Value *getBroadcastInstrs(Value *V);
361 virtual Value *getConsecutiveVector(Value* Val, int StartIdx, bool Negate);
362 virtual Value *reverseVector(Value *Vec);
365 /// \brief Look for a meaningful debug location on the instruction or it's
367 static Instruction *getDebugLocFromInstOrOperands(Instruction *I) {
372 if (I->getDebugLoc() != Empty)
375 for (User::op_iterator OI = I->op_begin(), OE = I->op_end(); OI != OE; ++OI) {
376 if (Instruction *OpInst = dyn_cast<Instruction>(*OI))
377 if (OpInst->getDebugLoc() != Empty)
384 /// \brief Set the debug location in the builder using the debug location in the
386 static void setDebugLocFromInst(IRBuilder<> &B, const Value *Ptr) {
387 if (const Instruction *Inst = dyn_cast_or_null<Instruction>(Ptr))
388 B.SetCurrentDebugLocation(Inst->getDebugLoc());
390 B.SetCurrentDebugLocation(DebugLoc());
393 /// LoopVectorizationLegality checks if it is legal to vectorize a loop, and
394 /// to what vectorization factor.
395 /// This class does not look at the profitability of vectorization, only the
396 /// legality. This class has two main kinds of checks:
397 /// * Memory checks - The code in canVectorizeMemory checks if vectorization
398 /// will change the order of memory accesses in a way that will change the
399 /// correctness of the program.
400 /// * Scalars checks - The code in canVectorizeInstrs and canVectorizeMemory
401 /// checks for a number of different conditions, such as the availability of a
402 /// single induction variable, that all types are supported and vectorize-able,
403 /// etc. This code reflects the capabilities of InnerLoopVectorizer.
404 /// This class is also used by InnerLoopVectorizer for identifying
405 /// induction variable and the different reduction variables.
406 class LoopVectorizationLegality {
408 LoopVectorizationLegality(Loop *L, ScalarEvolution *SE, DataLayout *DL,
409 DominatorTree *DT, TargetLibraryInfo *TLI)
410 : TheLoop(L), SE(SE), DL(DL), DT(DT), TLI(TLI),
411 Induction(0), WidestIndTy(0), HasFunNoNaNAttr(false),
412 MaxSafeDepDistBytes(-1U) {}
414 /// This enum represents the kinds of reductions that we support.
416 RK_NoReduction, ///< Not a reduction.
417 RK_IntegerAdd, ///< Sum of integers.
418 RK_IntegerMult, ///< Product of integers.
419 RK_IntegerOr, ///< Bitwise or logical OR of numbers.
420 RK_IntegerAnd, ///< Bitwise or logical AND of numbers.
421 RK_IntegerXor, ///< Bitwise or logical XOR of numbers.
422 RK_IntegerMinMax, ///< Min/max implemented in terms of select(cmp()).
423 RK_FloatAdd, ///< Sum of floats.
424 RK_FloatMult, ///< Product of floats.
425 RK_FloatMinMax ///< Min/max implemented in terms of select(cmp()).
428 /// This enum represents the kinds of inductions that we support.
430 IK_NoInduction, ///< Not an induction variable.
431 IK_IntInduction, ///< Integer induction variable. Step = 1.
432 IK_ReverseIntInduction, ///< Reverse int induction variable. Step = -1.
433 IK_PtrInduction, ///< Pointer induction var. Step = sizeof(elem).
434 IK_ReversePtrInduction ///< Reverse ptr indvar. Step = - sizeof(elem).
437 // This enum represents the kind of minmax reduction.
438 enum MinMaxReductionKind {
448 /// This POD struct holds information about reduction variables.
449 struct ReductionDescriptor {
450 ReductionDescriptor() : StartValue(0), LoopExitInstr(0),
451 Kind(RK_NoReduction), MinMaxKind(MRK_Invalid) {}
453 ReductionDescriptor(Value *Start, Instruction *Exit, ReductionKind K,
454 MinMaxReductionKind MK)
455 : StartValue(Start), LoopExitInstr(Exit), Kind(K), MinMaxKind(MK) {}
457 // The starting value of the reduction.
458 // It does not have to be zero!
459 TrackingVH<Value> StartValue;
460 // The instruction who's value is used outside the loop.
461 Instruction *LoopExitInstr;
462 // The kind of the reduction.
464 // If this a min/max reduction the kind of reduction.
465 MinMaxReductionKind MinMaxKind;
468 /// This POD struct holds information about a potential reduction operation.
469 struct ReductionInstDesc {
470 ReductionInstDesc(bool IsRedux, Instruction *I) :
471 IsReduction(IsRedux), PatternLastInst(I), MinMaxKind(MRK_Invalid) {}
473 ReductionInstDesc(Instruction *I, MinMaxReductionKind K) :
474 IsReduction(true), PatternLastInst(I), MinMaxKind(K) {}
476 // Is this instruction a reduction candidate.
478 // The last instruction in a min/max pattern (select of the select(icmp())
479 // pattern), or the current reduction instruction otherwise.
480 Instruction *PatternLastInst;
481 // If this is a min/max pattern the comparison predicate.
482 MinMaxReductionKind MinMaxKind;
485 // This POD struct holds information about the memory runtime legality
486 // check that a group of pointers do not overlap.
487 struct RuntimePointerCheck {
488 RuntimePointerCheck() : Need(false) {}
490 /// Reset the state of the pointer runtime information.
498 /// Insert a pointer and calculate the start and end SCEVs.
499 void insert(ScalarEvolution *SE, Loop *Lp, Value *Ptr, bool WritePtr,
502 /// This flag indicates if we need to add the runtime check.
504 /// Holds the pointers that we need to check.
505 SmallVector<TrackingVH<Value>, 2> Pointers;
506 /// Holds the pointer value at the beginning of the loop.
507 SmallVector<const SCEV*, 2> Starts;
508 /// Holds the pointer value at the end of the loop.
509 SmallVector<const SCEV*, 2> Ends;
510 /// Holds the information if this pointer is used for writing to memory.
511 SmallVector<bool, 2> IsWritePtr;
512 /// Holds the id of the set of pointers that could be dependent because of a
513 /// shared underlying object.
514 SmallVector<unsigned, 2> DependencySetId;
517 /// A POD for saving information about induction variables.
518 struct InductionInfo {
519 InductionInfo(Value *Start, InductionKind K) : StartValue(Start), IK(K) {}
520 InductionInfo() : StartValue(0), IK(IK_NoInduction) {}
522 TrackingVH<Value> StartValue;
527 /// ReductionList contains the reduction descriptors for all
528 /// of the reductions that were found in the loop.
529 typedef DenseMap<PHINode*, ReductionDescriptor> ReductionList;
531 /// InductionList saves induction variables and maps them to the
532 /// induction descriptor.
533 typedef MapVector<PHINode*, InductionInfo> InductionList;
535 /// Returns true if it is legal to vectorize this loop.
536 /// This does not mean that it is profitable to vectorize this
537 /// loop, only that it is legal to do so.
540 /// Returns the Induction variable.
541 PHINode *getInduction() { return Induction; }
543 /// Returns the reduction variables found in the loop.
544 ReductionList *getReductionVars() { return &Reductions; }
546 /// Returns the induction variables found in the loop.
547 InductionList *getInductionVars() { return &Inductions; }
549 /// Returns the widest induction type.
550 Type *getWidestInductionType() { return WidestIndTy; }
552 /// Returns True if V is an induction variable in this loop.
553 bool isInductionVariable(const Value *V);
555 /// Return true if the block BB needs to be predicated in order for the loop
556 /// to be vectorized.
557 bool blockNeedsPredication(BasicBlock *BB);
559 /// Check if this pointer is consecutive when vectorizing. This happens
560 /// when the last index of the GEP is the induction variable, or that the
561 /// pointer itself is an induction variable.
562 /// This check allows us to vectorize A[idx] into a wide load/store.
564 /// 0 - Stride is unknown or non consecutive.
565 /// 1 - Address is consecutive.
566 /// -1 - Address is consecutive, and decreasing.
567 int isConsecutivePtr(Value *Ptr);
569 /// Returns true if the value V is uniform within the loop.
570 bool isUniform(Value *V);
572 /// Returns true if this instruction will remain scalar after vectorization.
573 bool isUniformAfterVectorization(Instruction* I) { return Uniforms.count(I); }
575 /// Returns the information that we collected about runtime memory check.
576 RuntimePointerCheck *getRuntimePointerCheck() { return &PtrRtCheck; }
578 /// This function returns the identity element (or neutral element) for
580 static Constant *getReductionIdentity(ReductionKind K, Type *Tp);
582 unsigned getMaxSafeDepDistBytes() { return MaxSafeDepDistBytes; }
585 /// Check if a single basic block loop is vectorizable.
586 /// At this point we know that this is a loop with a constant trip count
587 /// and we only need to check individual instructions.
588 bool canVectorizeInstrs();
590 /// When we vectorize loops we may change the order in which
591 /// we read and write from memory. This method checks if it is
592 /// legal to vectorize the code, considering only memory constrains.
593 /// Returns true if the loop is vectorizable
594 bool canVectorizeMemory();
596 /// Return true if we can vectorize this loop using the IF-conversion
598 bool canVectorizeWithIfConvert();
600 /// Collect the variables that need to stay uniform after vectorization.
601 void collectLoopUniforms();
603 /// Return true if all of the instructions in the block can be speculatively
604 /// executed. \p SafePtrs is a list of addresses that are known to be legal
605 /// and we know that we can read from them without segfault.
606 bool blockCanBePredicated(BasicBlock *BB, SmallPtrSet<Value *, 8>& SafePtrs);
608 /// Returns True, if 'Phi' is the kind of reduction variable for type
609 /// 'Kind'. If this is a reduction variable, it adds it to ReductionList.
610 bool AddReductionVar(PHINode *Phi, ReductionKind Kind);
611 /// Returns a struct describing if the instruction 'I' can be a reduction
612 /// variable of type 'Kind'. If the reduction is a min/max pattern of
613 /// select(icmp()) this function advances the instruction pointer 'I' from the
614 /// compare instruction to the select instruction and stores this pointer in
615 /// 'PatternLastInst' member of the returned struct.
616 ReductionInstDesc isReductionInstr(Instruction *I, ReductionKind Kind,
617 ReductionInstDesc &Desc);
618 /// Returns true if the instruction is a Select(ICmp(X, Y), X, Y) instruction
619 /// pattern corresponding to a min(X, Y) or max(X, Y).
620 static ReductionInstDesc isMinMaxSelectCmpPattern(Instruction *I,
621 ReductionInstDesc &Prev);
622 /// Returns the induction kind of Phi. This function may return NoInduction
623 /// if the PHI is not an induction variable.
624 InductionKind isInductionVariable(PHINode *Phi);
626 /// The loop that we evaluate.
630 /// DataLayout analysis.
634 /// Target Library Info.
635 TargetLibraryInfo *TLI;
637 // --- vectorization state --- //
639 /// Holds the integer induction variable. This is the counter of the
642 /// Holds the reduction variables.
643 ReductionList Reductions;
644 /// Holds all of the induction variables that we found in the loop.
645 /// Notice that inductions don't need to start at zero and that induction
646 /// variables can be pointers.
647 InductionList Inductions;
648 /// Holds the widest induction type encountered.
651 /// Allowed outside users. This holds the reduction
652 /// vars which can be accessed from outside the loop.
653 SmallPtrSet<Value*, 4> AllowedExit;
654 /// This set holds the variables which are known to be uniform after
656 SmallPtrSet<Instruction*, 4> Uniforms;
657 /// We need to check that all of the pointers in this list are disjoint
659 RuntimePointerCheck PtrRtCheck;
660 /// Can we assume the absence of NaNs.
661 bool HasFunNoNaNAttr;
663 unsigned MaxSafeDepDistBytes;
666 /// LoopVectorizationCostModel - estimates the expected speedups due to
668 /// In many cases vectorization is not profitable. This can happen because of
669 /// a number of reasons. In this class we mainly attempt to predict the
670 /// expected speedup/slowdowns due to the supported instruction set. We use the
671 /// TargetTransformInfo to query the different backends for the cost of
672 /// different operations.
673 class LoopVectorizationCostModel {
675 LoopVectorizationCostModel(Loop *L, ScalarEvolution *SE, LoopInfo *LI,
676 LoopVectorizationLegality *Legal,
677 const TargetTransformInfo &TTI,
678 DataLayout *DL, const TargetLibraryInfo *TLI)
679 : TheLoop(L), SE(SE), LI(LI), Legal(Legal), TTI(TTI), DL(DL), TLI(TLI) {}
681 /// Information about vectorization costs
682 struct VectorizationFactor {
683 unsigned Width; // Vector width with best cost
684 unsigned Cost; // Cost of the loop with that width
686 /// \return The most profitable vectorization factor and the cost of that VF.
687 /// This method checks every power of two up to VF. If UserVF is not ZERO
688 /// then this vectorization factor will be selected if vectorization is
690 VectorizationFactor selectVectorizationFactor(bool OptForSize,
693 /// \return The size (in bits) of the widest type in the code that
694 /// needs to be vectorized. We ignore values that remain scalar such as
695 /// 64 bit loop indices.
696 unsigned getWidestType();
698 /// \return The most profitable unroll factor.
699 /// If UserUF is non-zero then this method finds the best unroll-factor
700 /// based on register pressure and other parameters.
701 /// VF and LoopCost are the selected vectorization factor and the cost of the
703 unsigned selectUnrollFactor(bool OptForSize, unsigned UserUF, unsigned VF,
706 /// \brief A struct that represents some properties of the register usage
708 struct RegisterUsage {
709 /// Holds the number of loop invariant values that are used in the loop.
710 unsigned LoopInvariantRegs;
711 /// Holds the maximum number of concurrent live intervals in the loop.
712 unsigned MaxLocalUsers;
713 /// Holds the number of instructions in the loop.
714 unsigned NumInstructions;
717 /// \return information about the register usage of the loop.
718 RegisterUsage calculateRegisterUsage();
721 /// Returns the expected execution cost. The unit of the cost does
722 /// not matter because we use the 'cost' units to compare different
723 /// vector widths. The cost that is returned is *not* normalized by
724 /// the factor width.
725 unsigned expectedCost(unsigned VF);
727 /// Returns the execution time cost of an instruction for a given vector
728 /// width. Vector width of one means scalar.
729 unsigned getInstructionCost(Instruction *I, unsigned VF);
731 /// A helper function for converting Scalar types to vector types.
732 /// If the incoming type is void, we return void. If the VF is 1, we return
734 static Type* ToVectorTy(Type *Scalar, unsigned VF);
736 /// Returns whether the instruction is a load or store and will be a emitted
737 /// as a vector operation.
738 bool isConsecutiveLoadOrStore(Instruction *I);
740 /// The loop that we evaluate.
744 /// Loop Info analysis.
746 /// Vectorization legality.
747 LoopVectorizationLegality *Legal;
748 /// Vector target information.
749 const TargetTransformInfo &TTI;
750 /// Target data layout information.
752 /// Target Library Info.
753 const TargetLibraryInfo *TLI;
756 /// Utility class for getting and setting loop vectorizer hints in the form
757 /// of loop metadata.
758 struct LoopVectorizeHints {
759 /// Vectorization width.
761 /// Vectorization unroll factor.
764 LoopVectorizeHints(const Loop *L, bool DisableUnrolling)
765 : Width(VectorizationFactor)
766 , Unroll(DisableUnrolling ? 1 : VectorizationUnroll)
767 , LoopID(L->getLoopID()) {
769 // The command line options override any loop metadata except for when
770 // width == 1 which is used to indicate the loop is already vectorized.
771 if (VectorizationFactor.getNumOccurrences() > 0 && Width != 1)
772 Width = VectorizationFactor;
773 if (VectorizationUnroll.getNumOccurrences() > 0)
774 Unroll = VectorizationUnroll;
776 DEBUG(if (DisableUnrolling && Unroll == 1)
777 dbgs() << "LV: Unrolling disabled by the pass manager\n");
780 /// Return the loop vectorizer metadata prefix.
781 static StringRef Prefix() { return "llvm.vectorizer."; }
783 MDNode *createHint(LLVMContext &Context, StringRef Name, unsigned V) {
784 SmallVector<Value*, 2> Vals;
785 Vals.push_back(MDString::get(Context, Name));
786 Vals.push_back(ConstantInt::get(Type::getInt32Ty(Context), V));
787 return MDNode::get(Context, Vals);
790 /// Mark the loop L as already vectorized by setting the width to 1.
791 void setAlreadyVectorized(Loop *L) {
792 LLVMContext &Context = L->getHeader()->getContext();
796 // Create a new loop id with one more operand for the already_vectorized
797 // hint. If the loop already has a loop id then copy the existing operands.
798 SmallVector<Value*, 4> Vals(1);
800 for (unsigned i = 1, ie = LoopID->getNumOperands(); i < ie; ++i)
801 Vals.push_back(LoopID->getOperand(i));
803 Vals.push_back(createHint(Context, Twine(Prefix(), "width").str(), Width));
805 MDNode *NewLoopID = MDNode::get(Context, Vals);
806 // Set operand 0 to refer to the loop id itself.
807 NewLoopID->replaceOperandWith(0, NewLoopID);
809 L->setLoopID(NewLoopID);
811 LoopID->replaceAllUsesWith(NewLoopID);
819 /// Find hints specified in the loop metadata.
820 void getHints(const Loop *L) {
824 // First operand should refer to the loop id itself.
825 assert(LoopID->getNumOperands() > 0 && "requires at least one operand");
826 assert(LoopID->getOperand(0) == LoopID && "invalid loop id");
828 for (unsigned i = 1, ie = LoopID->getNumOperands(); i < ie; ++i) {
829 const MDString *S = 0;
830 SmallVector<Value*, 4> Args;
832 // The expected hint is either a MDString or a MDNode with the first
833 // operand a MDString.
834 if (const MDNode *MD = dyn_cast<MDNode>(LoopID->getOperand(i))) {
835 if (!MD || MD->getNumOperands() == 0)
837 S = dyn_cast<MDString>(MD->getOperand(0));
838 for (unsigned i = 1, ie = MD->getNumOperands(); i < ie; ++i)
839 Args.push_back(MD->getOperand(i));
841 S = dyn_cast<MDString>(LoopID->getOperand(i));
842 assert(Args.size() == 0 && "too many arguments for MDString");
848 // Check if the hint starts with the vectorizer prefix.
849 StringRef Hint = S->getString();
850 if (!Hint.startswith(Prefix()))
852 // Remove the prefix.
853 Hint = Hint.substr(Prefix().size(), StringRef::npos);
855 if (Args.size() == 1)
856 getHint(Hint, Args[0]);
860 // Check string hint with one operand.
861 void getHint(StringRef Hint, Value *Arg) {
862 const ConstantInt *C = dyn_cast<ConstantInt>(Arg);
864 unsigned Val = C->getZExtValue();
866 if (Hint == "width") {
867 assert(isPowerOf2_32(Val) && Val <= MaxVectorWidth &&
868 "Invalid width metadata");
870 } else if (Hint == "unroll") {
871 assert(isPowerOf2_32(Val) && Val <= MaxUnrollFactor &&
872 "Invalid unroll metadata");
875 DEBUG(dbgs() << "LV: ignoring unknown hint " << Hint);
879 /// The LoopVectorize Pass.
880 struct LoopVectorize : public LoopPass {
881 /// Pass identification, replacement for typeid
884 explicit LoopVectorize(bool NoUnrolling = false)
885 : LoopPass(ID), DisableUnrolling(NoUnrolling) {
886 initializeLoopVectorizePass(*PassRegistry::getPassRegistry());
892 TargetTransformInfo *TTI;
894 TargetLibraryInfo *TLI;
895 bool DisableUnrolling;
897 virtual bool runOnLoop(Loop *L, LPPassManager &LPM) {
898 // We only vectorize innermost loops.
902 SE = &getAnalysis<ScalarEvolution>();
903 DL = getAnalysisIfAvailable<DataLayout>();
904 LI = &getAnalysis<LoopInfo>();
905 TTI = &getAnalysis<TargetTransformInfo>();
906 DT = &getAnalysis<DominatorTree>();
907 TLI = getAnalysisIfAvailable<TargetLibraryInfo>();
910 DEBUG(dbgs() << "LV: Not vectorizing because of missing data layout");
914 DEBUG(dbgs() << "LV: Checking a loop in \"" <<
915 L->getHeader()->getParent()->getName() << "\"\n");
917 LoopVectorizeHints Hints(L, DisableUnrolling);
919 if (Hints.Width == 1 && Hints.Unroll == 1) {
920 DEBUG(dbgs() << "LV: Not vectorizing.\n");
924 // Check if it is legal to vectorize the loop.
925 LoopVectorizationLegality LVL(L, SE, DL, DT, TLI);
926 if (!LVL.canVectorize()) {
927 DEBUG(dbgs() << "LV: Not vectorizing.\n");
931 // Use the cost model.
932 LoopVectorizationCostModel CM(L, SE, LI, &LVL, *TTI, DL, TLI);
934 // Check the function attributes to find out if this function should be
935 // optimized for size.
936 Function *F = L->getHeader()->getParent();
937 Attribute::AttrKind SzAttr = Attribute::OptimizeForSize;
938 Attribute::AttrKind FlAttr = Attribute::NoImplicitFloat;
939 unsigned FnIndex = AttributeSet::FunctionIndex;
940 bool OptForSize = F->getAttributes().hasAttribute(FnIndex, SzAttr);
941 bool NoFloat = F->getAttributes().hasAttribute(FnIndex, FlAttr);
944 DEBUG(dbgs() << "LV: Can't vectorize when the NoImplicitFloat"
945 "attribute is used.\n");
949 // Select the optimal vectorization factor.
950 LoopVectorizationCostModel::VectorizationFactor VF;
951 VF = CM.selectVectorizationFactor(OptForSize, Hints.Width);
952 // Select the unroll factor.
953 unsigned UF = CM.selectUnrollFactor(OptForSize, Hints.Unroll, VF.Width,
957 DEBUG(dbgs() << "LV: Vectorization is possible but not beneficial.\n");
960 DEBUG(dbgs() << "LV: Found a vectorizable loop ("<< VF.Width << ") in "<<
961 F->getParent()->getModuleIdentifier()<<"\n");
962 DEBUG(dbgs() << "LV: Unroll Factor is " << UF << "\n");
967 // We decided not to vectorize, but we may want to unroll.
968 InnerLoopUnroller Unroller(L, SE, LI, DT, DL, TLI, UF);
969 Unroller.vectorize(&LVL);
971 // If we decided that it is *legal* to vectorize the loop then do it.
972 InnerLoopVectorizer LB(L, SE, LI, DT, DL, TLI, VF.Width, UF);
976 // Mark the loop as already vectorized to avoid vectorizing again.
977 Hints.setAlreadyVectorized(L);
979 DEBUG(verifyFunction(*L->getHeader()->getParent()));
983 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
984 LoopPass::getAnalysisUsage(AU);
985 AU.addRequiredID(LoopSimplifyID);
986 AU.addRequiredID(LCSSAID);
987 AU.addRequired<DominatorTree>();
988 AU.addRequired<LoopInfo>();
989 AU.addRequired<ScalarEvolution>();
990 AU.addRequired<TargetTransformInfo>();
991 AU.addPreserved<LoopInfo>();
992 AU.addPreserved<DominatorTree>();
997 } // end anonymous namespace
999 //===----------------------------------------------------------------------===//
1000 // Implementation of LoopVectorizationLegality, InnerLoopVectorizer and
1001 // LoopVectorizationCostModel.
1002 //===----------------------------------------------------------------------===//
1005 LoopVectorizationLegality::RuntimePointerCheck::insert(ScalarEvolution *SE,
1006 Loop *Lp, Value *Ptr,
1008 unsigned DepSetId) {
1009 const SCEV *Sc = SE->getSCEV(Ptr);
1010 const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Sc);
1011 assert(AR && "Invalid addrec expression");
1012 const SCEV *Ex = SE->getBackedgeTakenCount(Lp);
1013 const SCEV *ScEnd = AR->evaluateAtIteration(Ex, *SE);
1014 Pointers.push_back(Ptr);
1015 Starts.push_back(AR->getStart());
1016 Ends.push_back(ScEnd);
1017 IsWritePtr.push_back(WritePtr);
1018 DependencySetId.push_back(DepSetId);
1021 Value *InnerLoopVectorizer::getBroadcastInstrs(Value *V) {
1022 // Save the current insertion location.
1023 Instruction *Loc = Builder.GetInsertPoint();
1025 // We need to place the broadcast of invariant variables outside the loop.
1026 Instruction *Instr = dyn_cast<Instruction>(V);
1027 bool NewInstr = (Instr && Instr->getParent() == LoopVectorBody);
1028 bool Invariant = OrigLoop->isLoopInvariant(V) && !NewInstr;
1030 // Place the code for broadcasting invariant variables in the new preheader.
1032 Builder.SetInsertPoint(LoopVectorPreHeader->getTerminator());
1034 // Broadcast the scalar into all locations in the vector.
1035 Value *Shuf = Builder.CreateVectorSplat(VF, V, "broadcast");
1037 // Restore the builder insertion point.
1039 Builder.SetInsertPoint(Loc);
1044 Value *InnerLoopVectorizer::getConsecutiveVector(Value* Val, int StartIdx,
1046 assert(Val->getType()->isVectorTy() && "Must be a vector");
1047 assert(Val->getType()->getScalarType()->isIntegerTy() &&
1048 "Elem must be an integer");
1049 // Create the types.
1050 Type *ITy = Val->getType()->getScalarType();
1051 VectorType *Ty = cast<VectorType>(Val->getType());
1052 int VLen = Ty->getNumElements();
1053 SmallVector<Constant*, 8> Indices;
1055 // Create a vector of consecutive numbers from zero to VF.
1056 for (int i = 0; i < VLen; ++i) {
1057 int64_t Idx = Negate ? (-i) : i;
1058 Indices.push_back(ConstantInt::get(ITy, StartIdx + Idx, Negate));
1061 // Add the consecutive indices to the vector value.
1062 Constant *Cv = ConstantVector::get(Indices);
1063 assert(Cv->getType() == Val->getType() && "Invalid consecutive vec");
1064 return Builder.CreateAdd(Val, Cv, "induction");
1067 int LoopVectorizationLegality::isConsecutivePtr(Value *Ptr) {
1068 assert(Ptr->getType()->isPointerTy() && "Unexpected non ptr");
1069 // Make sure that the pointer does not point to structs.
1070 if (cast<PointerType>(Ptr->getType())->getElementType()->isAggregateType())
1073 // If this value is a pointer induction variable we know it is consecutive.
1074 PHINode *Phi = dyn_cast_or_null<PHINode>(Ptr);
1075 if (Phi && Inductions.count(Phi)) {
1076 InductionInfo II = Inductions[Phi];
1077 if (IK_PtrInduction == II.IK)
1079 else if (IK_ReversePtrInduction == II.IK)
1083 GetElementPtrInst *Gep = dyn_cast_or_null<GetElementPtrInst>(Ptr);
1087 unsigned NumOperands = Gep->getNumOperands();
1088 Value *LastIndex = Gep->getOperand(NumOperands - 1);
1090 Value *GpPtr = Gep->getPointerOperand();
1091 // If this GEP value is a consecutive pointer induction variable and all of
1092 // the indices are constant then we know it is consecutive. We can
1093 Phi = dyn_cast<PHINode>(GpPtr);
1094 if (Phi && Inductions.count(Phi)) {
1096 // Make sure that the pointer does not point to structs.
1097 PointerType *GepPtrType = cast<PointerType>(GpPtr->getType());
1098 if (GepPtrType->getElementType()->isAggregateType())
1101 // Make sure that all of the index operands are loop invariant.
1102 for (unsigned i = 1; i < NumOperands; ++i)
1103 if (!SE->isLoopInvariant(SE->getSCEV(Gep->getOperand(i)), TheLoop))
1106 InductionInfo II = Inductions[Phi];
1107 if (IK_PtrInduction == II.IK)
1109 else if (IK_ReversePtrInduction == II.IK)
1113 // Check that all of the gep indices are uniform except for the last.
1114 for (unsigned i = 0; i < NumOperands - 1; ++i)
1115 if (!SE->isLoopInvariant(SE->getSCEV(Gep->getOperand(i)), TheLoop))
1118 // We can emit wide load/stores only if the last index is the induction
1120 const SCEV *Last = SE->getSCEV(LastIndex);
1121 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Last)) {
1122 const SCEV *Step = AR->getStepRecurrence(*SE);
1124 // The memory is consecutive because the last index is consecutive
1125 // and all other indices are loop invariant.
1128 if (Step->isAllOnesValue())
1135 bool LoopVectorizationLegality::isUniform(Value *V) {
1136 return (SE->isLoopInvariant(SE->getSCEV(V), TheLoop));
1139 InnerLoopVectorizer::VectorParts&
1140 InnerLoopVectorizer::getVectorValue(Value *V) {
1141 assert(V != Induction && "The new induction variable should not be used.");
1142 assert(!V->getType()->isVectorTy() && "Can't widen a vector");
1144 // If we have this scalar in the map, return it.
1145 if (WidenMap.has(V))
1146 return WidenMap.get(V);
1148 // If this scalar is unknown, assume that it is a constant or that it is
1149 // loop invariant. Broadcast V and save the value for future uses.
1150 Value *B = getBroadcastInstrs(V);
1151 return WidenMap.splat(V, B);
1154 Value *InnerLoopVectorizer::reverseVector(Value *Vec) {
1155 assert(Vec->getType()->isVectorTy() && "Invalid type");
1156 SmallVector<Constant*, 8> ShuffleMask;
1157 for (unsigned i = 0; i < VF; ++i)
1158 ShuffleMask.push_back(Builder.getInt32(VF - i - 1));
1160 return Builder.CreateShuffleVector(Vec, UndefValue::get(Vec->getType()),
1161 ConstantVector::get(ShuffleMask),
1166 void InnerLoopVectorizer::vectorizeMemoryInstruction(Instruction *Instr,
1167 LoopVectorizationLegality *Legal) {
1168 // Attempt to issue a wide load.
1169 LoadInst *LI = dyn_cast<LoadInst>(Instr);
1170 StoreInst *SI = dyn_cast<StoreInst>(Instr);
1172 assert((LI || SI) && "Invalid Load/Store instruction");
1174 Type *ScalarDataTy = LI ? LI->getType() : SI->getValueOperand()->getType();
1175 Type *DataTy = VectorType::get(ScalarDataTy, VF);
1176 Value *Ptr = LI ? LI->getPointerOperand() : SI->getPointerOperand();
1177 unsigned Alignment = LI ? LI->getAlignment() : SI->getAlignment();
1178 unsigned AddressSpace = Ptr->getType()->getPointerAddressSpace();
1179 unsigned ScalarAllocatedSize = DL->getTypeAllocSize(ScalarDataTy);
1180 unsigned VectorElementSize = DL->getTypeStoreSize(DataTy)/VF;
1182 if (ScalarAllocatedSize != VectorElementSize)
1183 return scalarizeInstruction(Instr);
1185 // If the pointer is loop invariant or if it is non consecutive,
1186 // scalarize the load.
1187 int ConsecutiveStride = Legal->isConsecutivePtr(Ptr);
1188 bool Reverse = ConsecutiveStride < 0;
1189 bool UniformLoad = LI && Legal->isUniform(Ptr);
1190 if (!ConsecutiveStride || UniformLoad)
1191 return scalarizeInstruction(Instr);
1193 Constant *Zero = Builder.getInt32(0);
1194 VectorParts &Entry = WidenMap.get(Instr);
1196 // Handle consecutive loads/stores.
1197 GetElementPtrInst *Gep = dyn_cast<GetElementPtrInst>(Ptr);
1198 if (Gep && Legal->isInductionVariable(Gep->getPointerOperand())) {
1199 setDebugLocFromInst(Builder, Gep);
1200 Value *PtrOperand = Gep->getPointerOperand();
1201 Value *FirstBasePtr = getVectorValue(PtrOperand)[0];
1202 FirstBasePtr = Builder.CreateExtractElement(FirstBasePtr, Zero);
1204 // Create the new GEP with the new induction variable.
1205 GetElementPtrInst *Gep2 = cast<GetElementPtrInst>(Gep->clone());
1206 Gep2->setOperand(0, FirstBasePtr);
1207 Gep2->setName("gep.indvar.base");
1208 Ptr = Builder.Insert(Gep2);
1210 setDebugLocFromInst(Builder, Gep);
1211 assert(SE->isLoopInvariant(SE->getSCEV(Gep->getPointerOperand()),
1212 OrigLoop) && "Base ptr must be invariant");
1214 // The last index does not have to be the induction. It can be
1215 // consecutive and be a function of the index. For example A[I+1];
1216 unsigned NumOperands = Gep->getNumOperands();
1217 unsigned LastOperand = NumOperands - 1;
1218 // Create the new GEP with the new induction variable.
1219 GetElementPtrInst *Gep2 = cast<GetElementPtrInst>(Gep->clone());
1221 for (unsigned i = 0; i < NumOperands; ++i) {
1222 Value *GepOperand = Gep->getOperand(i);
1223 Instruction *GepOperandInst = dyn_cast<Instruction>(GepOperand);
1225 // Update last index or loop invariant instruction anchored in loop.
1226 if (i == LastOperand ||
1227 (GepOperandInst && OrigLoop->contains(GepOperandInst))) {
1228 assert((i == LastOperand ||
1229 SE->isLoopInvariant(SE->getSCEV(GepOperandInst), OrigLoop)) &&
1230 "Must be last index or loop invariant");
1232 VectorParts &GEPParts = getVectorValue(GepOperand);
1233 Value *Index = GEPParts[0];
1234 Index = Builder.CreateExtractElement(Index, Zero);
1235 Gep2->setOperand(i, Index);
1236 Gep2->setName("gep.indvar.idx");
1239 Ptr = Builder.Insert(Gep2);
1241 // Use the induction element ptr.
1242 assert(isa<PHINode>(Ptr) && "Invalid induction ptr");
1243 setDebugLocFromInst(Builder, Ptr);
1244 VectorParts &PtrVal = getVectorValue(Ptr);
1245 Ptr = Builder.CreateExtractElement(PtrVal[0], Zero);
1250 assert(!Legal->isUniform(SI->getPointerOperand()) &&
1251 "We do not allow storing to uniform addresses");
1252 setDebugLocFromInst(Builder, SI);
1253 // We don't want to update the value in the map as it might be used in
1254 // another expression. So don't use a reference type for "StoredVal".
1255 VectorParts StoredVal = getVectorValue(SI->getValueOperand());
1257 for (unsigned Part = 0; Part < UF; ++Part) {
1258 // Calculate the pointer for the specific unroll-part.
1259 Value *PartPtr = Builder.CreateGEP(Ptr, Builder.getInt32(Part * VF));
1262 // If we store to reverse consecutive memory locations then we need
1263 // to reverse the order of elements in the stored value.
1264 StoredVal[Part] = reverseVector(StoredVal[Part]);
1265 // If the address is consecutive but reversed, then the
1266 // wide store needs to start at the last vector element.
1267 PartPtr = Builder.CreateGEP(Ptr, Builder.getInt32(-Part * VF));
1268 PartPtr = Builder.CreateGEP(PartPtr, Builder.getInt32(1 - VF));
1271 Value *VecPtr = Builder.CreateBitCast(PartPtr,
1272 DataTy->getPointerTo(AddressSpace));
1273 Builder.CreateStore(StoredVal[Part], VecPtr)->setAlignment(Alignment);
1279 assert(LI && "Must have a load instruction");
1280 setDebugLocFromInst(Builder, LI);
1281 for (unsigned Part = 0; Part < UF; ++Part) {
1282 // Calculate the pointer for the specific unroll-part.
1283 Value *PartPtr = Builder.CreateGEP(Ptr, Builder.getInt32(Part * VF));
1286 // If the address is consecutive but reversed, then the
1287 // wide store needs to start at the last vector element.
1288 PartPtr = Builder.CreateGEP(Ptr, Builder.getInt32(-Part * VF));
1289 PartPtr = Builder.CreateGEP(PartPtr, Builder.getInt32(1 - VF));
1292 Value *VecPtr = Builder.CreateBitCast(PartPtr,
1293 DataTy->getPointerTo(AddressSpace));
1294 Value *LI = Builder.CreateLoad(VecPtr, "wide.load");
1295 cast<LoadInst>(LI)->setAlignment(Alignment);
1296 Entry[Part] = Reverse ? reverseVector(LI) : LI;
1300 void InnerLoopVectorizer::scalarizeInstruction(Instruction *Instr) {
1301 assert(!Instr->getType()->isAggregateType() && "Can't handle vectors");
1302 // Holds vector parameters or scalars, in case of uniform vals.
1303 SmallVector<VectorParts, 4> Params;
1305 setDebugLocFromInst(Builder, Instr);
1307 // Find all of the vectorized parameters.
1308 for (unsigned op = 0, e = Instr->getNumOperands(); op != e; ++op) {
1309 Value *SrcOp = Instr->getOperand(op);
1311 // If we are accessing the old induction variable, use the new one.
1312 if (SrcOp == OldInduction) {
1313 Params.push_back(getVectorValue(SrcOp));
1317 // Try using previously calculated values.
1318 Instruction *SrcInst = dyn_cast<Instruction>(SrcOp);
1320 // If the src is an instruction that appeared earlier in the basic block
1321 // then it should already be vectorized.
1322 if (SrcInst && OrigLoop->contains(SrcInst)) {
1323 assert(WidenMap.has(SrcInst) && "Source operand is unavailable");
1324 // The parameter is a vector value from earlier.
1325 Params.push_back(WidenMap.get(SrcInst));
1327 // The parameter is a scalar from outside the loop. Maybe even a constant.
1328 VectorParts Scalars;
1329 Scalars.append(UF, SrcOp);
1330 Params.push_back(Scalars);
1334 assert(Params.size() == Instr->getNumOperands() &&
1335 "Invalid number of operands");
1337 // Does this instruction return a value ?
1338 bool IsVoidRetTy = Instr->getType()->isVoidTy();
1340 Value *UndefVec = IsVoidRetTy ? 0 :
1341 UndefValue::get(VectorType::get(Instr->getType(), VF));
1342 // Create a new entry in the WidenMap and initialize it to Undef or Null.
1343 VectorParts &VecResults = WidenMap.splat(Instr, UndefVec);
1345 // For each vector unroll 'part':
1346 for (unsigned Part = 0; Part < UF; ++Part) {
1347 // For each scalar that we create:
1348 for (unsigned Width = 0; Width < VF; ++Width) {
1349 Instruction *Cloned = Instr->clone();
1351 Cloned->setName(Instr->getName() + ".cloned");
1352 // Replace the operands of the cloned instrucions with extracted scalars.
1353 for (unsigned op = 0, e = Instr->getNumOperands(); op != e; ++op) {
1354 Value *Op = Params[op][Part];
1355 // Param is a vector. Need to extract the right lane.
1356 if (Op->getType()->isVectorTy())
1357 Op = Builder.CreateExtractElement(Op, Builder.getInt32(Width));
1358 Cloned->setOperand(op, Op);
1361 // Place the cloned scalar in the new loop.
1362 Builder.Insert(Cloned);
1364 // If the original scalar returns a value we need to place it in a vector
1365 // so that future users will be able to use it.
1367 VecResults[Part] = Builder.CreateInsertElement(VecResults[Part], Cloned,
1368 Builder.getInt32(Width));
1374 InnerLoopVectorizer::addRuntimeCheck(LoopVectorizationLegality *Legal,
1376 LoopVectorizationLegality::RuntimePointerCheck *PtrRtCheck =
1377 Legal->getRuntimePointerCheck();
1379 if (!PtrRtCheck->Need)
1382 unsigned NumPointers = PtrRtCheck->Pointers.size();
1383 SmallVector<TrackingVH<Value> , 2> Starts;
1384 SmallVector<TrackingVH<Value> , 2> Ends;
1386 SCEVExpander Exp(*SE, "induction");
1388 // Use this type for pointer arithmetic.
1389 Type* PtrArithTy = Type::getInt8PtrTy(Loc->getContext(), 0);
1391 for (unsigned i = 0; i < NumPointers; ++i) {
1392 Value *Ptr = PtrRtCheck->Pointers[i];
1393 const SCEV *Sc = SE->getSCEV(Ptr);
1395 if (SE->isLoopInvariant(Sc, OrigLoop)) {
1396 DEBUG(dbgs() << "LV: Adding RT check for a loop invariant ptr:" <<
1398 Starts.push_back(Ptr);
1399 Ends.push_back(Ptr);
1401 DEBUG(dbgs() << "LV: Adding RT check for range:" << *Ptr <<"\n");
1403 Value *Start = Exp.expandCodeFor(PtrRtCheck->Starts[i], PtrArithTy, Loc);
1404 Value *End = Exp.expandCodeFor(PtrRtCheck->Ends[i], PtrArithTy, Loc);
1405 Starts.push_back(Start);
1406 Ends.push_back(End);
1410 IRBuilder<> ChkBuilder(Loc);
1411 // Our instructions might fold to a constant.
1412 Value *MemoryRuntimeCheck = 0;
1413 for (unsigned i = 0; i < NumPointers; ++i) {
1414 for (unsigned j = i+1; j < NumPointers; ++j) {
1415 // No need to check if two readonly pointers intersect.
1416 if (!PtrRtCheck->IsWritePtr[i] && !PtrRtCheck->IsWritePtr[j])
1419 // Only need to check pointers between two different dependency sets.
1420 if (PtrRtCheck->DependencySetId[i] == PtrRtCheck->DependencySetId[j])
1423 Value *Start0 = ChkBuilder.CreateBitCast(Starts[i], PtrArithTy, "bc");
1424 Value *Start1 = ChkBuilder.CreateBitCast(Starts[j], PtrArithTy, "bc");
1425 Value *End0 = ChkBuilder.CreateBitCast(Ends[i], PtrArithTy, "bc");
1426 Value *End1 = ChkBuilder.CreateBitCast(Ends[j], PtrArithTy, "bc");
1428 Value *Cmp0 = ChkBuilder.CreateICmpULE(Start0, End1, "bound0");
1429 Value *Cmp1 = ChkBuilder.CreateICmpULE(Start1, End0, "bound1");
1430 Value *IsConflict = ChkBuilder.CreateAnd(Cmp0, Cmp1, "found.conflict");
1431 if (MemoryRuntimeCheck)
1432 IsConflict = ChkBuilder.CreateOr(MemoryRuntimeCheck, IsConflict,
1434 MemoryRuntimeCheck = IsConflict;
1438 // We have to do this trickery because the IRBuilder might fold the check to a
1439 // constant expression in which case there is no Instruction anchored in a
1441 LLVMContext &Ctx = Loc->getContext();
1442 Instruction * Check = BinaryOperator::CreateAnd(MemoryRuntimeCheck,
1443 ConstantInt::getTrue(Ctx));
1444 ChkBuilder.Insert(Check, "memcheck.conflict");
1449 InnerLoopVectorizer::createEmptyLoop(LoopVectorizationLegality *Legal) {
1451 In this function we generate a new loop. The new loop will contain
1452 the vectorized instructions while the old loop will continue to run the
1455 [ ] <-- vector loop bypass (may consist of multiple blocks).
1458 | [ ] <-- vector pre header.
1462 | [ ]_| <-- vector loop.
1465 >[ ] <--- middle-block.
1468 | [ ] <--- new preheader.
1472 | [ ]_| <-- old scalar loop to handle remainder.
1475 >[ ] <-- exit block.
1479 BasicBlock *OldBasicBlock = OrigLoop->getHeader();
1480 BasicBlock *BypassBlock = OrigLoop->getLoopPreheader();
1481 BasicBlock *ExitBlock = OrigLoop->getExitBlock();
1482 assert(ExitBlock && "Must have an exit block");
1484 // Some loops have a single integer induction variable, while other loops
1485 // don't. One example is c++ iterators that often have multiple pointer
1486 // induction variables. In the code below we also support a case where we
1487 // don't have a single induction variable.
1488 OldInduction = Legal->getInduction();
1489 Type *IdxTy = Legal->getWidestInductionType();
1491 // Find the loop boundaries.
1492 const SCEV *ExitCount = SE->getBackedgeTakenCount(OrigLoop);
1493 assert(ExitCount != SE->getCouldNotCompute() && "Invalid loop count");
1495 // Get the total trip count from the count by adding 1.
1496 ExitCount = SE->getAddExpr(ExitCount,
1497 SE->getConstant(ExitCount->getType(), 1));
1499 // Expand the trip count and place the new instructions in the preheader.
1500 // Notice that the pre-header does not change, only the loop body.
1501 SCEVExpander Exp(*SE, "induction");
1503 // Count holds the overall loop count (N).
1504 Value *Count = Exp.expandCodeFor(ExitCount, ExitCount->getType(),
1505 BypassBlock->getTerminator());
1507 // The loop index does not have to start at Zero. Find the original start
1508 // value from the induction PHI node. If we don't have an induction variable
1509 // then we know that it starts at zero.
1510 Builder.SetInsertPoint(BypassBlock->getTerminator());
1511 Value *StartIdx = ExtendedIdx = OldInduction ?
1512 Builder.CreateZExt(OldInduction->getIncomingValueForBlock(BypassBlock),
1514 ConstantInt::get(IdxTy, 0);
1516 assert(BypassBlock && "Invalid loop structure");
1517 LoopBypassBlocks.push_back(BypassBlock);
1519 // Split the single block loop into the two loop structure described above.
1520 BasicBlock *VectorPH =
1521 BypassBlock->splitBasicBlock(BypassBlock->getTerminator(), "vector.ph");
1522 BasicBlock *VecBody =
1523 VectorPH->splitBasicBlock(VectorPH->getTerminator(), "vector.body");
1524 BasicBlock *MiddleBlock =
1525 VecBody->splitBasicBlock(VecBody->getTerminator(), "middle.block");
1526 BasicBlock *ScalarPH =
1527 MiddleBlock->splitBasicBlock(MiddleBlock->getTerminator(), "scalar.ph");
1529 // Create and register the new vector loop.
1530 Loop* Lp = new Loop();
1531 Loop *ParentLoop = OrigLoop->getParentLoop();
1533 // Insert the new loop into the loop nest and register the new basic blocks
1534 // before calling any utilities such as SCEV that require valid LoopInfo.
1536 ParentLoop->addChildLoop(Lp);
1537 ParentLoop->addBasicBlockToLoop(ScalarPH, LI->getBase());
1538 ParentLoop->addBasicBlockToLoop(VectorPH, LI->getBase());
1539 ParentLoop->addBasicBlockToLoop(MiddleBlock, LI->getBase());
1541 LI->addTopLevelLoop(Lp);
1543 Lp->addBasicBlockToLoop(VecBody, LI->getBase());
1545 // Use this IR builder to create the loop instructions (Phi, Br, Cmp)
1547 Builder.SetInsertPoint(VecBody->getFirstInsertionPt());
1549 // Generate the induction variable.
1550 setDebugLocFromInst(Builder, getDebugLocFromInstOrOperands(OldInduction));
1551 Induction = Builder.CreatePHI(IdxTy, 2, "index");
1552 // The loop step is equal to the vectorization factor (num of SIMD elements)
1553 // times the unroll factor (num of SIMD instructions).
1554 Constant *Step = ConstantInt::get(IdxTy, VF * UF);
1556 // This is the IR builder that we use to add all of the logic for bypassing
1557 // the new vector loop.
1558 IRBuilder<> BypassBuilder(BypassBlock->getTerminator());
1559 setDebugLocFromInst(BypassBuilder,
1560 getDebugLocFromInstOrOperands(OldInduction));
1562 // We may need to extend the index in case there is a type mismatch.
1563 // We know that the count starts at zero and does not overflow.
1564 if (Count->getType() != IdxTy) {
1565 // The exit count can be of pointer type. Convert it to the correct
1567 if (ExitCount->getType()->isPointerTy())
1568 Count = BypassBuilder.CreatePointerCast(Count, IdxTy, "ptrcnt.to.int");
1570 Count = BypassBuilder.CreateZExtOrTrunc(Count, IdxTy, "cnt.cast");
1573 // Add the start index to the loop count to get the new end index.
1574 Value *IdxEnd = BypassBuilder.CreateAdd(Count, StartIdx, "end.idx");
1576 // Now we need to generate the expression for N - (N % VF), which is
1577 // the part that the vectorized body will execute.
1578 Value *R = BypassBuilder.CreateURem(Count, Step, "n.mod.vf");
1579 Value *CountRoundDown = BypassBuilder.CreateSub(Count, R, "n.vec");
1580 Value *IdxEndRoundDown = BypassBuilder.CreateAdd(CountRoundDown, StartIdx,
1581 "end.idx.rnd.down");
1583 // Now, compare the new count to zero. If it is zero skip the vector loop and
1584 // jump to the scalar loop.
1585 Value *Cmp = BypassBuilder.CreateICmpEQ(IdxEndRoundDown, StartIdx,
1588 BasicBlock *LastBypassBlock = BypassBlock;
1590 // Generate the code that checks in runtime if arrays overlap. We put the
1591 // checks into a separate block to make the more common case of few elements
1593 Instruction *MemRuntimeCheck = addRuntimeCheck(Legal,
1594 BypassBlock->getTerminator());
1595 if (MemRuntimeCheck) {
1596 // Create a new block containing the memory check.
1597 BasicBlock *CheckBlock = BypassBlock->splitBasicBlock(MemRuntimeCheck,
1600 ParentLoop->addBasicBlockToLoop(CheckBlock, LI->getBase());
1601 LoopBypassBlocks.push_back(CheckBlock);
1603 // Replace the branch into the memory check block with a conditional branch
1604 // for the "few elements case".
1605 Instruction *OldTerm = BypassBlock->getTerminator();
1606 BranchInst::Create(MiddleBlock, CheckBlock, Cmp, OldTerm);
1607 OldTerm->eraseFromParent();
1609 Cmp = MemRuntimeCheck;
1610 LastBypassBlock = CheckBlock;
1613 LastBypassBlock->getTerminator()->eraseFromParent();
1614 BranchInst::Create(MiddleBlock, VectorPH, Cmp,
1617 // We are going to resume the execution of the scalar loop.
1618 // Go over all of the induction variables that we found and fix the
1619 // PHIs that are left in the scalar version of the loop.
1620 // The starting values of PHI nodes depend on the counter of the last
1621 // iteration in the vectorized loop.
1622 // If we come from a bypass edge then we need to start from the original
1625 // This variable saves the new starting index for the scalar loop.
1626 PHINode *ResumeIndex = 0;
1627 LoopVectorizationLegality::InductionList::iterator I, E;
1628 LoopVectorizationLegality::InductionList *List = Legal->getInductionVars();
1629 // Set builder to point to last bypass block.
1630 BypassBuilder.SetInsertPoint(LoopBypassBlocks.back()->getTerminator());
1631 for (I = List->begin(), E = List->end(); I != E; ++I) {
1632 PHINode *OrigPhi = I->first;
1633 LoopVectorizationLegality::InductionInfo II = I->second;
1635 Type *ResumeValTy = (OrigPhi == OldInduction) ? IdxTy : OrigPhi->getType();
1636 PHINode *ResumeVal = PHINode::Create(ResumeValTy, 2, "resume.val",
1637 MiddleBlock->getTerminator());
1638 // We might have extended the type of the induction variable but we need a
1639 // truncated version for the scalar loop.
1640 PHINode *TruncResumeVal = (OrigPhi == OldInduction) ?
1641 PHINode::Create(OrigPhi->getType(), 2, "trunc.resume.val",
1642 MiddleBlock->getTerminator()) : 0;
1644 Value *EndValue = 0;
1646 case LoopVectorizationLegality::IK_NoInduction:
1647 llvm_unreachable("Unknown induction");
1648 case LoopVectorizationLegality::IK_IntInduction: {
1649 // Handle the integer induction counter.
1650 assert(OrigPhi->getType()->isIntegerTy() && "Invalid type");
1652 // We have the canonical induction variable.
1653 if (OrigPhi == OldInduction) {
1654 // Create a truncated version of the resume value for the scalar loop,
1655 // we might have promoted the type to a larger width.
1657 BypassBuilder.CreateTrunc(IdxEndRoundDown, OrigPhi->getType());
1658 // The new PHI merges the original incoming value, in case of a bypass,
1659 // or the value at the end of the vectorized loop.
1660 for (unsigned I = 0, E = LoopBypassBlocks.size(); I != E; ++I)
1661 TruncResumeVal->addIncoming(II.StartValue, LoopBypassBlocks[I]);
1662 TruncResumeVal->addIncoming(EndValue, VecBody);
1664 // We know what the end value is.
1665 EndValue = IdxEndRoundDown;
1666 // We also know which PHI node holds it.
1667 ResumeIndex = ResumeVal;
1671 // Not the canonical induction variable - add the vector loop count to the
1673 Value *CRD = BypassBuilder.CreateSExtOrTrunc(CountRoundDown,
1674 II.StartValue->getType(),
1676 EndValue = BypassBuilder.CreateAdd(CRD, II.StartValue , "ind.end");
1679 case LoopVectorizationLegality::IK_ReverseIntInduction: {
1680 // Convert the CountRoundDown variable to the PHI size.
1681 Value *CRD = BypassBuilder.CreateSExtOrTrunc(CountRoundDown,
1682 II.StartValue->getType(),
1684 // Handle reverse integer induction counter.
1685 EndValue = BypassBuilder.CreateSub(II.StartValue, CRD, "rev.ind.end");
1688 case LoopVectorizationLegality::IK_PtrInduction: {
1689 // For pointer induction variables, calculate the offset using
1691 EndValue = BypassBuilder.CreateGEP(II.StartValue, CountRoundDown,
1695 case LoopVectorizationLegality::IK_ReversePtrInduction: {
1696 // The value at the end of the loop for the reverse pointer is calculated
1697 // by creating a GEP with a negative index starting from the start value.
1698 Value *Zero = ConstantInt::get(CountRoundDown->getType(), 0);
1699 Value *NegIdx = BypassBuilder.CreateSub(Zero, CountRoundDown,
1701 EndValue = BypassBuilder.CreateGEP(II.StartValue, NegIdx,
1707 // The new PHI merges the original incoming value, in case of a bypass,
1708 // or the value at the end of the vectorized loop.
1709 for (unsigned I = 0, E = LoopBypassBlocks.size(); I != E; ++I) {
1710 if (OrigPhi == OldInduction)
1711 ResumeVal->addIncoming(StartIdx, LoopBypassBlocks[I]);
1713 ResumeVal->addIncoming(II.StartValue, LoopBypassBlocks[I]);
1715 ResumeVal->addIncoming(EndValue, VecBody);
1717 // Fix the scalar body counter (PHI node).
1718 unsigned BlockIdx = OrigPhi->getBasicBlockIndex(ScalarPH);
1719 // The old inductions phi node in the scalar body needs the truncated value.
1720 if (OrigPhi == OldInduction)
1721 OrigPhi->setIncomingValue(BlockIdx, TruncResumeVal);
1723 OrigPhi->setIncomingValue(BlockIdx, ResumeVal);
1726 // If we are generating a new induction variable then we also need to
1727 // generate the code that calculates the exit value. This value is not
1728 // simply the end of the counter because we may skip the vectorized body
1729 // in case of a runtime check.
1731 assert(!ResumeIndex && "Unexpected resume value found");
1732 ResumeIndex = PHINode::Create(IdxTy, 2, "new.indc.resume.val",
1733 MiddleBlock->getTerminator());
1734 for (unsigned I = 0, E = LoopBypassBlocks.size(); I != E; ++I)
1735 ResumeIndex->addIncoming(StartIdx, LoopBypassBlocks[I]);
1736 ResumeIndex->addIncoming(IdxEndRoundDown, VecBody);
1739 // Make sure that we found the index where scalar loop needs to continue.
1740 assert(ResumeIndex && ResumeIndex->getType()->isIntegerTy() &&
1741 "Invalid resume Index");
1743 // Add a check in the middle block to see if we have completed
1744 // all of the iterations in the first vector loop.
1745 // If (N - N%VF) == N, then we *don't* need to run the remainder.
1746 Value *CmpN = CmpInst::Create(Instruction::ICmp, CmpInst::ICMP_EQ, IdxEnd,
1747 ResumeIndex, "cmp.n",
1748 MiddleBlock->getTerminator());
1750 BranchInst::Create(ExitBlock, ScalarPH, CmpN, MiddleBlock->getTerminator());
1751 // Remove the old terminator.
1752 MiddleBlock->getTerminator()->eraseFromParent();
1754 // Create i+1 and fill the PHINode.
1755 Value *NextIdx = Builder.CreateAdd(Induction, Step, "index.next");
1756 Induction->addIncoming(StartIdx, VectorPH);
1757 Induction->addIncoming(NextIdx, VecBody);
1758 // Create the compare.
1759 Value *ICmp = Builder.CreateICmpEQ(NextIdx, IdxEndRoundDown);
1760 Builder.CreateCondBr(ICmp, MiddleBlock, VecBody);
1762 // Now we have two terminators. Remove the old one from the block.
1763 VecBody->getTerminator()->eraseFromParent();
1765 // Get ready to start creating new instructions into the vectorized body.
1766 Builder.SetInsertPoint(VecBody->getFirstInsertionPt());
1769 LoopVectorPreHeader = VectorPH;
1770 LoopScalarPreHeader = ScalarPH;
1771 LoopMiddleBlock = MiddleBlock;
1772 LoopExitBlock = ExitBlock;
1773 LoopVectorBody = VecBody;
1774 LoopScalarBody = OldBasicBlock;
1777 /// This function returns the identity element (or neutral element) for
1778 /// the operation K.
1780 LoopVectorizationLegality::getReductionIdentity(ReductionKind K, Type *Tp) {
1785 // Adding, Xoring, Oring zero to a number does not change it.
1786 return ConstantInt::get(Tp, 0);
1787 case RK_IntegerMult:
1788 // Multiplying a number by 1 does not change it.
1789 return ConstantInt::get(Tp, 1);
1791 // AND-ing a number with an all-1 value does not change it.
1792 return ConstantInt::get(Tp, -1, true);
1794 // Multiplying a number by 1 does not change it.
1795 return ConstantFP::get(Tp, 1.0L);
1797 // Adding zero to a number does not change it.
1798 return ConstantFP::get(Tp, 0.0L);
1800 llvm_unreachable("Unknown reduction kind");
1804 static Intrinsic::ID
1805 getIntrinsicIDForCall(CallInst *CI, const TargetLibraryInfo *TLI) {
1806 // If we have an intrinsic call, check if it is trivially vectorizable.
1807 if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(CI)) {
1808 switch (II->getIntrinsicID()) {
1809 case Intrinsic::sqrt:
1810 case Intrinsic::sin:
1811 case Intrinsic::cos:
1812 case Intrinsic::exp:
1813 case Intrinsic::exp2:
1814 case Intrinsic::log:
1815 case Intrinsic::log10:
1816 case Intrinsic::log2:
1817 case Intrinsic::fabs:
1818 case Intrinsic::copysign:
1819 case Intrinsic::floor:
1820 case Intrinsic::ceil:
1821 case Intrinsic::trunc:
1822 case Intrinsic::rint:
1823 case Intrinsic::nearbyint:
1824 case Intrinsic::round:
1825 case Intrinsic::pow:
1826 case Intrinsic::fma:
1827 case Intrinsic::fmuladd:
1828 case Intrinsic::lifetime_start:
1829 case Intrinsic::lifetime_end:
1830 return II->getIntrinsicID();
1832 return Intrinsic::not_intrinsic;
1837 return Intrinsic::not_intrinsic;
1840 Function *F = CI->getCalledFunction();
1841 // We're going to make assumptions on the semantics of the functions, check
1842 // that the target knows that it's available in this environment.
1843 if (!F || !TLI->getLibFunc(F->getName(), Func))
1844 return Intrinsic::not_intrinsic;
1846 // Otherwise check if we have a call to a function that can be turned into a
1847 // vector intrinsic.
1854 return Intrinsic::sin;
1858 return Intrinsic::cos;
1862 return Intrinsic::exp;
1864 case LibFunc::exp2f:
1865 case LibFunc::exp2l:
1866 return Intrinsic::exp2;
1870 return Intrinsic::log;
1871 case LibFunc::log10:
1872 case LibFunc::log10f:
1873 case LibFunc::log10l:
1874 return Intrinsic::log10;
1876 case LibFunc::log2f:
1877 case LibFunc::log2l:
1878 return Intrinsic::log2;
1880 case LibFunc::fabsf:
1881 case LibFunc::fabsl:
1882 return Intrinsic::fabs;
1883 case LibFunc::copysign:
1884 case LibFunc::copysignf:
1885 case LibFunc::copysignl:
1886 return Intrinsic::copysign;
1887 case LibFunc::floor:
1888 case LibFunc::floorf:
1889 case LibFunc::floorl:
1890 return Intrinsic::floor;
1892 case LibFunc::ceilf:
1893 case LibFunc::ceill:
1894 return Intrinsic::ceil;
1895 case LibFunc::trunc:
1896 case LibFunc::truncf:
1897 case LibFunc::truncl:
1898 return Intrinsic::trunc;
1900 case LibFunc::rintf:
1901 case LibFunc::rintl:
1902 return Intrinsic::rint;
1903 case LibFunc::nearbyint:
1904 case LibFunc::nearbyintf:
1905 case LibFunc::nearbyintl:
1906 return Intrinsic::nearbyint;
1907 case LibFunc::round:
1908 case LibFunc::roundf:
1909 case LibFunc::roundl:
1910 return Intrinsic::round;
1914 return Intrinsic::pow;
1917 return Intrinsic::not_intrinsic;
1920 /// This function translates the reduction kind to an LLVM binary operator.
1922 getReductionBinOp(LoopVectorizationLegality::ReductionKind Kind) {
1924 case LoopVectorizationLegality::RK_IntegerAdd:
1925 return Instruction::Add;
1926 case LoopVectorizationLegality::RK_IntegerMult:
1927 return Instruction::Mul;
1928 case LoopVectorizationLegality::RK_IntegerOr:
1929 return Instruction::Or;
1930 case LoopVectorizationLegality::RK_IntegerAnd:
1931 return Instruction::And;
1932 case LoopVectorizationLegality::RK_IntegerXor:
1933 return Instruction::Xor;
1934 case LoopVectorizationLegality::RK_FloatMult:
1935 return Instruction::FMul;
1936 case LoopVectorizationLegality::RK_FloatAdd:
1937 return Instruction::FAdd;
1938 case LoopVectorizationLegality::RK_IntegerMinMax:
1939 return Instruction::ICmp;
1940 case LoopVectorizationLegality::RK_FloatMinMax:
1941 return Instruction::FCmp;
1943 llvm_unreachable("Unknown reduction operation");
1947 Value *createMinMaxOp(IRBuilder<> &Builder,
1948 LoopVectorizationLegality::MinMaxReductionKind RK,
1951 CmpInst::Predicate P = CmpInst::ICMP_NE;
1954 llvm_unreachable("Unknown min/max reduction kind");
1955 case LoopVectorizationLegality::MRK_UIntMin:
1956 P = CmpInst::ICMP_ULT;
1958 case LoopVectorizationLegality::MRK_UIntMax:
1959 P = CmpInst::ICMP_UGT;
1961 case LoopVectorizationLegality::MRK_SIntMin:
1962 P = CmpInst::ICMP_SLT;
1964 case LoopVectorizationLegality::MRK_SIntMax:
1965 P = CmpInst::ICMP_SGT;
1967 case LoopVectorizationLegality::MRK_FloatMin:
1968 P = CmpInst::FCMP_OLT;
1970 case LoopVectorizationLegality::MRK_FloatMax:
1971 P = CmpInst::FCMP_OGT;
1976 if (RK == LoopVectorizationLegality::MRK_FloatMin ||
1977 RK == LoopVectorizationLegality::MRK_FloatMax)
1978 Cmp = Builder.CreateFCmp(P, Left, Right, "rdx.minmax.cmp");
1980 Cmp = Builder.CreateICmp(P, Left, Right, "rdx.minmax.cmp");
1982 Value *Select = Builder.CreateSelect(Cmp, Left, Right, "rdx.minmax.select");
1987 InnerLoopVectorizer::vectorizeLoop(LoopVectorizationLegality *Legal) {
1988 //===------------------------------------------------===//
1990 // Notice: any optimization or new instruction that go
1991 // into the code below should be also be implemented in
1994 //===------------------------------------------------===//
1995 Constant *Zero = Builder.getInt32(0);
1997 // In order to support reduction variables we need to be able to vectorize
1998 // Phi nodes. Phi nodes have cycles, so we need to vectorize them in two
1999 // stages. First, we create a new vector PHI node with no incoming edges.
2000 // We use this value when we vectorize all of the instructions that use the
2001 // PHI. Next, after all of the instructions in the block are complete we
2002 // add the new incoming edges to the PHI. At this point all of the
2003 // instructions in the basic block are vectorized, so we can use them to
2004 // construct the PHI.
2005 PhiVector RdxPHIsToFix;
2007 // Scan the loop in a topological order to ensure that defs are vectorized
2009 LoopBlocksDFS DFS(OrigLoop);
2012 // Vectorize all of the blocks in the original loop.
2013 for (LoopBlocksDFS::RPOIterator bb = DFS.beginRPO(),
2014 be = DFS.endRPO(); bb != be; ++bb)
2015 vectorizeBlockInLoop(Legal, *bb, &RdxPHIsToFix);
2017 // At this point every instruction in the original loop is widened to
2018 // a vector form. We are almost done. Now, we need to fix the PHI nodes
2019 // that we vectorized. The PHI nodes are currently empty because we did
2020 // not want to introduce cycles. Notice that the remaining PHI nodes
2021 // that we need to fix are reduction variables.
2023 // Create the 'reduced' values for each of the induction vars.
2024 // The reduced values are the vector values that we scalarize and combine
2025 // after the loop is finished.
2026 for (PhiVector::iterator it = RdxPHIsToFix.begin(), e = RdxPHIsToFix.end();
2028 PHINode *RdxPhi = *it;
2029 assert(RdxPhi && "Unable to recover vectorized PHI");
2031 // Find the reduction variable descriptor.
2032 assert(Legal->getReductionVars()->count(RdxPhi) &&
2033 "Unable to find the reduction variable");
2034 LoopVectorizationLegality::ReductionDescriptor RdxDesc =
2035 (*Legal->getReductionVars())[RdxPhi];
2037 setDebugLocFromInst(Builder, RdxDesc.StartValue);
2039 // We need to generate a reduction vector from the incoming scalar.
2040 // To do so, we need to generate the 'identity' vector and overide
2041 // one of the elements with the incoming scalar reduction. We need
2042 // to do it in the vector-loop preheader.
2043 Builder.SetInsertPoint(LoopBypassBlocks.front()->getTerminator());
2045 // This is the vector-clone of the value that leaves the loop.
2046 VectorParts &VectorExit = getVectorValue(RdxDesc.LoopExitInstr);
2047 Type *VecTy = VectorExit[0]->getType();
2049 // Find the reduction identity variable. Zero for addition, or, xor,
2050 // one for multiplication, -1 for And.
2053 if (RdxDesc.Kind == LoopVectorizationLegality::RK_IntegerMinMax ||
2054 RdxDesc.Kind == LoopVectorizationLegality::RK_FloatMinMax) {
2055 // MinMax reduction have the start value as their identify.
2057 VectorStart = Identity = RdxDesc.StartValue;
2059 VectorStart = Identity = Builder.CreateVectorSplat(VF,
2064 // Handle other reduction kinds:
2066 LoopVectorizationLegality::getReductionIdentity(RdxDesc.Kind,
2067 VecTy->getScalarType());
2070 // This vector is the Identity vector where the first element is the
2071 // incoming scalar reduction.
2072 VectorStart = RdxDesc.StartValue;
2074 Identity = ConstantVector::getSplat(VF, Iden);
2076 // This vector is the Identity vector where the first element is the
2077 // incoming scalar reduction.
2078 VectorStart = Builder.CreateInsertElement(Identity,
2079 RdxDesc.StartValue, Zero);
2083 // Fix the vector-loop phi.
2084 // We created the induction variable so we know that the
2085 // preheader is the first entry.
2086 BasicBlock *VecPreheader = Induction->getIncomingBlock(0);
2088 // Reductions do not have to start at zero. They can start with
2089 // any loop invariant values.
2090 VectorParts &VecRdxPhi = WidenMap.get(RdxPhi);
2091 BasicBlock *Latch = OrigLoop->getLoopLatch();
2092 Value *LoopVal = RdxPhi->getIncomingValueForBlock(Latch);
2093 VectorParts &Val = getVectorValue(LoopVal);
2094 for (unsigned part = 0; part < UF; ++part) {
2095 // Make sure to add the reduction stat value only to the
2096 // first unroll part.
2097 Value *StartVal = (part == 0) ? VectorStart : Identity;
2098 cast<PHINode>(VecRdxPhi[part])->addIncoming(StartVal, VecPreheader);
2099 cast<PHINode>(VecRdxPhi[part])->addIncoming(Val[part], LoopVectorBody);
2102 // Before each round, move the insertion point right between
2103 // the PHIs and the values we are going to write.
2104 // This allows us to write both PHINodes and the extractelement
2106 Builder.SetInsertPoint(LoopMiddleBlock->getFirstInsertionPt());
2108 VectorParts RdxParts;
2109 setDebugLocFromInst(Builder, RdxDesc.LoopExitInstr);
2110 for (unsigned part = 0; part < UF; ++part) {
2111 // This PHINode contains the vectorized reduction variable, or
2112 // the initial value vector, if we bypass the vector loop.
2113 VectorParts &RdxExitVal = getVectorValue(RdxDesc.LoopExitInstr);
2114 PHINode *NewPhi = Builder.CreatePHI(VecTy, 2, "rdx.vec.exit.phi");
2115 Value *StartVal = (part == 0) ? VectorStart : Identity;
2116 for (unsigned I = 0, E = LoopBypassBlocks.size(); I != E; ++I)
2117 NewPhi->addIncoming(StartVal, LoopBypassBlocks[I]);
2118 NewPhi->addIncoming(RdxExitVal[part], LoopVectorBody);
2119 RdxParts.push_back(NewPhi);
2122 // Reduce all of the unrolled parts into a single vector.
2123 Value *ReducedPartRdx = RdxParts[0];
2124 unsigned Op = getReductionBinOp(RdxDesc.Kind);
2125 setDebugLocFromInst(Builder, ReducedPartRdx);
2126 for (unsigned part = 1; part < UF; ++part) {
2127 if (Op != Instruction::ICmp && Op != Instruction::FCmp)
2128 ReducedPartRdx = Builder.CreateBinOp((Instruction::BinaryOps)Op,
2129 RdxParts[part], ReducedPartRdx,
2132 ReducedPartRdx = createMinMaxOp(Builder, RdxDesc.MinMaxKind,
2133 ReducedPartRdx, RdxParts[part]);
2137 // VF is a power of 2 so we can emit the reduction using log2(VF) shuffles
2138 // and vector ops, reducing the set of values being computed by half each
2140 assert(isPowerOf2_32(VF) &&
2141 "Reduction emission only supported for pow2 vectors!");
2142 Value *TmpVec = ReducedPartRdx;
2143 SmallVector<Constant*, 32> ShuffleMask(VF, 0);
2144 for (unsigned i = VF; i != 1; i >>= 1) {
2145 // Move the upper half of the vector to the lower half.
2146 for (unsigned j = 0; j != i/2; ++j)
2147 ShuffleMask[j] = Builder.getInt32(i/2 + j);
2149 // Fill the rest of the mask with undef.
2150 std::fill(&ShuffleMask[i/2], ShuffleMask.end(),
2151 UndefValue::get(Builder.getInt32Ty()));
2154 Builder.CreateShuffleVector(TmpVec,
2155 UndefValue::get(TmpVec->getType()),
2156 ConstantVector::get(ShuffleMask),
2159 if (Op != Instruction::ICmp && Op != Instruction::FCmp)
2160 TmpVec = Builder.CreateBinOp((Instruction::BinaryOps)Op, TmpVec, Shuf,
2163 TmpVec = createMinMaxOp(Builder, RdxDesc.MinMaxKind, TmpVec, Shuf);
2166 // The result is in the first element of the vector.
2167 ReducedPartRdx = Builder.CreateExtractElement(TmpVec,
2168 Builder.getInt32(0));
2171 // Now, we need to fix the users of the reduction variable
2172 // inside and outside of the scalar remainder loop.
2173 // We know that the loop is in LCSSA form. We need to update the
2174 // PHI nodes in the exit blocks.
2175 for (BasicBlock::iterator LEI = LoopExitBlock->begin(),
2176 LEE = LoopExitBlock->end(); LEI != LEE; ++LEI) {
2177 PHINode *LCSSAPhi = dyn_cast<PHINode>(LEI);
2178 if (!LCSSAPhi) continue;
2180 // All PHINodes need to have a single entry edge, or two if
2181 // we already fixed them.
2182 assert(LCSSAPhi->getNumIncomingValues() < 3 && "Invalid LCSSA PHI");
2184 // We found our reduction value exit-PHI. Update it with the
2185 // incoming bypass edge.
2186 if (LCSSAPhi->getIncomingValue(0) == RdxDesc.LoopExitInstr) {
2187 // Add an edge coming from the bypass.
2188 LCSSAPhi->addIncoming(ReducedPartRdx, LoopMiddleBlock);
2191 }// end of the LCSSA phi scan.
2193 // Fix the scalar loop reduction variable with the incoming reduction sum
2194 // from the vector body and from the backedge value.
2195 int IncomingEdgeBlockIdx =
2196 (RdxPhi)->getBasicBlockIndex(OrigLoop->getLoopLatch());
2197 assert(IncomingEdgeBlockIdx >= 0 && "Invalid block index");
2198 // Pick the other block.
2199 int SelfEdgeBlockIdx = (IncomingEdgeBlockIdx ? 0 : 1);
2200 (RdxPhi)->setIncomingValue(SelfEdgeBlockIdx, ReducedPartRdx);
2201 (RdxPhi)->setIncomingValue(IncomingEdgeBlockIdx, RdxDesc.LoopExitInstr);
2202 }// end of for each redux variable.
2207 void InnerLoopVectorizer::fixLCSSAPHIs() {
2208 for (BasicBlock::iterator LEI = LoopExitBlock->begin(),
2209 LEE = LoopExitBlock->end(); LEI != LEE; ++LEI) {
2210 PHINode *LCSSAPhi = dyn_cast<PHINode>(LEI);
2211 if (!LCSSAPhi) continue;
2212 if (LCSSAPhi->getNumIncomingValues() == 1)
2213 LCSSAPhi->addIncoming(UndefValue::get(LCSSAPhi->getType()),
2218 InnerLoopVectorizer::VectorParts
2219 InnerLoopVectorizer::createEdgeMask(BasicBlock *Src, BasicBlock *Dst) {
2220 assert(std::find(pred_begin(Dst), pred_end(Dst), Src) != pred_end(Dst) &&
2223 // Look for cached value.
2224 std::pair<BasicBlock*, BasicBlock*> Edge(Src, Dst);
2225 EdgeMaskCache::iterator ECEntryIt = MaskCache.find(Edge);
2226 if (ECEntryIt != MaskCache.end())
2227 return ECEntryIt->second;
2229 VectorParts SrcMask = createBlockInMask(Src);
2231 // The terminator has to be a branch inst!
2232 BranchInst *BI = dyn_cast<BranchInst>(Src->getTerminator());
2233 assert(BI && "Unexpected terminator found");
2235 if (BI->isConditional()) {
2236 VectorParts EdgeMask = getVectorValue(BI->getCondition());
2238 if (BI->getSuccessor(0) != Dst)
2239 for (unsigned part = 0; part < UF; ++part)
2240 EdgeMask[part] = Builder.CreateNot(EdgeMask[part]);
2242 for (unsigned part = 0; part < UF; ++part)
2243 EdgeMask[part] = Builder.CreateAnd(EdgeMask[part], SrcMask[part]);
2245 MaskCache[Edge] = EdgeMask;
2249 MaskCache[Edge] = SrcMask;
2253 InnerLoopVectorizer::VectorParts
2254 InnerLoopVectorizer::createBlockInMask(BasicBlock *BB) {
2255 assert(OrigLoop->contains(BB) && "Block is not a part of a loop");
2257 // Loop incoming mask is all-one.
2258 if (OrigLoop->getHeader() == BB) {
2259 Value *C = ConstantInt::get(IntegerType::getInt1Ty(BB->getContext()), 1);
2260 return getVectorValue(C);
2263 // This is the block mask. We OR all incoming edges, and with zero.
2264 Value *Zero = ConstantInt::get(IntegerType::getInt1Ty(BB->getContext()), 0);
2265 VectorParts BlockMask = getVectorValue(Zero);
2268 for (pred_iterator it = pred_begin(BB), e = pred_end(BB); it != e; ++it) {
2269 VectorParts EM = createEdgeMask(*it, BB);
2270 for (unsigned part = 0; part < UF; ++part)
2271 BlockMask[part] = Builder.CreateOr(BlockMask[part], EM[part]);
2277 void InnerLoopVectorizer::widenPHIInstruction(Instruction *PN,
2278 InnerLoopVectorizer::VectorParts &Entry,
2279 LoopVectorizationLegality *Legal,
2280 unsigned UF, unsigned VF, PhiVector *PV) {
2281 PHINode* P = cast<PHINode>(PN);
2282 // Handle reduction variables:
2283 if (Legal->getReductionVars()->count(P)) {
2284 for (unsigned part = 0; part < UF; ++part) {
2285 // This is phase one of vectorizing PHIs.
2286 Type *VecTy = (VF == 1) ? PN->getType() :
2287 VectorType::get(PN->getType(), VF);
2288 Entry[part] = PHINode::Create(VecTy, 2, "vec.phi",
2289 LoopVectorBody-> getFirstInsertionPt());
2295 setDebugLocFromInst(Builder, P);
2296 // Check for PHI nodes that are lowered to vector selects.
2297 if (P->getParent() != OrigLoop->getHeader()) {
2298 // We know that all PHIs in non header blocks are converted into
2299 // selects, so we don't have to worry about the insertion order and we
2300 // can just use the builder.
2301 // At this point we generate the predication tree. There may be
2302 // duplications since this is a simple recursive scan, but future
2303 // optimizations will clean it up.
2305 unsigned NumIncoming = P->getNumIncomingValues();
2307 // Generate a sequence of selects of the form:
2308 // SELECT(Mask3, In3,
2309 // SELECT(Mask2, In2,
2311 for (unsigned In = 0; In < NumIncoming; In++) {
2312 VectorParts Cond = createEdgeMask(P->getIncomingBlock(In),
2314 VectorParts &In0 = getVectorValue(P->getIncomingValue(In));
2316 for (unsigned part = 0; part < UF; ++part) {
2317 // We might have single edge PHIs (blocks) - use an identity
2318 // 'select' for the first PHI operand.
2320 Entry[part] = Builder.CreateSelect(Cond[part], In0[part],
2323 // Select between the current value and the previous incoming edge
2324 // based on the incoming mask.
2325 Entry[part] = Builder.CreateSelect(Cond[part], In0[part],
2326 Entry[part], "predphi");
2332 // This PHINode must be an induction variable.
2333 // Make sure that we know about it.
2334 assert(Legal->getInductionVars()->count(P) &&
2335 "Not an induction variable");
2337 LoopVectorizationLegality::InductionInfo II =
2338 Legal->getInductionVars()->lookup(P);
2341 case LoopVectorizationLegality::IK_NoInduction:
2342 llvm_unreachable("Unknown induction");
2343 case LoopVectorizationLegality::IK_IntInduction: {
2344 assert(P->getType() == II.StartValue->getType() && "Types must match");
2345 Type *PhiTy = P->getType();
2347 if (P == OldInduction) {
2348 // Handle the canonical induction variable. We might have had to
2350 Broadcasted = Builder.CreateTrunc(Induction, PhiTy);
2352 // Handle other induction variables that are now based on the
2354 Value *NormalizedIdx = Builder.CreateSub(Induction, ExtendedIdx,
2356 NormalizedIdx = Builder.CreateSExtOrTrunc(NormalizedIdx, PhiTy);
2357 Broadcasted = Builder.CreateAdd(II.StartValue, NormalizedIdx,
2360 Broadcasted = getBroadcastInstrs(Broadcasted);
2361 // After broadcasting the induction variable we need to make the vector
2362 // consecutive by adding 0, 1, 2, etc.
2363 for (unsigned part = 0; part < UF; ++part)
2364 Entry[part] = getConsecutiveVector(Broadcasted, VF * part, false);
2367 case LoopVectorizationLegality::IK_ReverseIntInduction:
2368 case LoopVectorizationLegality::IK_PtrInduction:
2369 case LoopVectorizationLegality::IK_ReversePtrInduction:
2370 // Handle reverse integer and pointer inductions.
2371 Value *StartIdx = ExtendedIdx;
2372 // This is the normalized GEP that starts counting at zero.
2373 Value *NormalizedIdx = Builder.CreateSub(Induction, StartIdx,
2376 // Handle the reverse integer induction variable case.
2377 if (LoopVectorizationLegality::IK_ReverseIntInduction == II.IK) {
2378 IntegerType *DstTy = cast<IntegerType>(II.StartValue->getType());
2379 Value *CNI = Builder.CreateSExtOrTrunc(NormalizedIdx, DstTy,
2381 Value *ReverseInd = Builder.CreateSub(II.StartValue, CNI,
2384 // This is a new value so do not hoist it out.
2385 Value *Broadcasted = getBroadcastInstrs(ReverseInd);
2386 // After broadcasting the induction variable we need to make the
2387 // vector consecutive by adding ... -3, -2, -1, 0.
2388 for (unsigned part = 0; part < UF; ++part)
2389 Entry[part] = getConsecutiveVector(Broadcasted, -(int)VF * part,
2394 // Handle the pointer induction variable case.
2395 assert(P->getType()->isPointerTy() && "Unexpected type.");
2397 // Is this a reverse induction ptr or a consecutive induction ptr.
2398 bool Reverse = (LoopVectorizationLegality::IK_ReversePtrInduction ==
2401 // This is the vector of results. Notice that we don't generate
2402 // vector geps because scalar geps result in better code.
2403 for (unsigned part = 0; part < UF; ++part) {
2405 int EltIndex = (part) * (Reverse ? -1 : 1);
2406 Constant *Idx = ConstantInt::get(Induction->getType(), EltIndex);
2409 GlobalIdx = Builder.CreateSub(Idx, NormalizedIdx, "gep.ridx");
2411 GlobalIdx = Builder.CreateAdd(NormalizedIdx, Idx, "gep.idx");
2413 Value *SclrGep = Builder.CreateGEP(II.StartValue, GlobalIdx,
2415 Entry[part] = SclrGep;
2419 Value *VecVal = UndefValue::get(VectorType::get(P->getType(), VF));
2420 for (unsigned int i = 0; i < VF; ++i) {
2421 int EltIndex = (i + part * VF) * (Reverse ? -1 : 1);
2422 Constant *Idx = ConstantInt::get(Induction->getType(), EltIndex);
2425 GlobalIdx = Builder.CreateAdd(NormalizedIdx, Idx, "gep.idx");
2427 GlobalIdx = Builder.CreateSub(Idx, NormalizedIdx, "gep.ridx");
2429 Value *SclrGep = Builder.CreateGEP(II.StartValue, GlobalIdx,
2431 VecVal = Builder.CreateInsertElement(VecVal, SclrGep,
2432 Builder.getInt32(i),
2435 Entry[part] = VecVal;
2442 InnerLoopVectorizer::vectorizeBlockInLoop(LoopVectorizationLegality *Legal,
2443 BasicBlock *BB, PhiVector *PV) {
2444 // For each instruction in the old loop.
2445 for (BasicBlock::iterator it = BB->begin(), e = BB->end(); it != e; ++it) {
2446 VectorParts &Entry = WidenMap.get(it);
2447 switch (it->getOpcode()) {
2448 case Instruction::Br:
2449 // Nothing to do for PHIs and BR, since we already took care of the
2450 // loop control flow instructions.
2452 case Instruction::PHI:{
2453 // Vectorize PHINodes.
2454 widenPHIInstruction(it, Entry, Legal, UF, VF, PV);
2458 case Instruction::Add:
2459 case Instruction::FAdd:
2460 case Instruction::Sub:
2461 case Instruction::FSub:
2462 case Instruction::Mul:
2463 case Instruction::FMul:
2464 case Instruction::UDiv:
2465 case Instruction::SDiv:
2466 case Instruction::FDiv:
2467 case Instruction::URem:
2468 case Instruction::SRem:
2469 case Instruction::FRem:
2470 case Instruction::Shl:
2471 case Instruction::LShr:
2472 case Instruction::AShr:
2473 case Instruction::And:
2474 case Instruction::Or:
2475 case Instruction::Xor: {
2476 // Just widen binops.
2477 BinaryOperator *BinOp = dyn_cast<BinaryOperator>(it);
2478 setDebugLocFromInst(Builder, BinOp);
2479 VectorParts &A = getVectorValue(it->getOperand(0));
2480 VectorParts &B = getVectorValue(it->getOperand(1));
2482 // Use this vector value for all users of the original instruction.
2483 for (unsigned Part = 0; Part < UF; ++Part) {
2484 Value *V = Builder.CreateBinOp(BinOp->getOpcode(), A[Part], B[Part]);
2486 // Update the NSW, NUW and Exact flags. Notice: V can be an Undef.
2487 BinaryOperator *VecOp = dyn_cast<BinaryOperator>(V);
2488 if (VecOp && isa<OverflowingBinaryOperator>(BinOp)) {
2489 VecOp->setHasNoSignedWrap(BinOp->hasNoSignedWrap());
2490 VecOp->setHasNoUnsignedWrap(BinOp->hasNoUnsignedWrap());
2492 if (VecOp && isa<PossiblyExactOperator>(VecOp))
2493 VecOp->setIsExact(BinOp->isExact());
2499 case Instruction::Select: {
2501 // If the selector is loop invariant we can create a select
2502 // instruction with a scalar condition. Otherwise, use vector-select.
2503 bool InvariantCond = SE->isLoopInvariant(SE->getSCEV(it->getOperand(0)),
2505 setDebugLocFromInst(Builder, it);
2507 // The condition can be loop invariant but still defined inside the
2508 // loop. This means that we can't just use the original 'cond' value.
2509 // We have to take the 'vectorized' value and pick the first lane.
2510 // Instcombine will make this a no-op.
2511 VectorParts &Cond = getVectorValue(it->getOperand(0));
2512 VectorParts &Op0 = getVectorValue(it->getOperand(1));
2513 VectorParts &Op1 = getVectorValue(it->getOperand(2));
2515 Value *ScalarCond = (VF == 1) ? Cond[0] :
2516 Builder.CreateExtractElement(Cond[0], Builder.getInt32(0));
2518 for (unsigned Part = 0; Part < UF; ++Part) {
2519 Entry[Part] = Builder.CreateSelect(
2520 InvariantCond ? ScalarCond : Cond[Part],
2527 case Instruction::ICmp:
2528 case Instruction::FCmp: {
2529 // Widen compares. Generate vector compares.
2530 bool FCmp = (it->getOpcode() == Instruction::FCmp);
2531 CmpInst *Cmp = dyn_cast<CmpInst>(it);
2532 setDebugLocFromInst(Builder, it);
2533 VectorParts &A = getVectorValue(it->getOperand(0));
2534 VectorParts &B = getVectorValue(it->getOperand(1));
2535 for (unsigned Part = 0; Part < UF; ++Part) {
2538 C = Builder.CreateFCmp(Cmp->getPredicate(), A[Part], B[Part]);
2540 C = Builder.CreateICmp(Cmp->getPredicate(), A[Part], B[Part]);
2546 case Instruction::Store:
2547 case Instruction::Load:
2548 vectorizeMemoryInstruction(it, Legal);
2550 case Instruction::ZExt:
2551 case Instruction::SExt:
2552 case Instruction::FPToUI:
2553 case Instruction::FPToSI:
2554 case Instruction::FPExt:
2555 case Instruction::PtrToInt:
2556 case Instruction::IntToPtr:
2557 case Instruction::SIToFP:
2558 case Instruction::UIToFP:
2559 case Instruction::Trunc:
2560 case Instruction::FPTrunc:
2561 case Instruction::BitCast: {
2562 CastInst *CI = dyn_cast<CastInst>(it);
2563 setDebugLocFromInst(Builder, it);
2564 /// Optimize the special case where the source is the induction
2565 /// variable. Notice that we can only optimize the 'trunc' case
2566 /// because: a. FP conversions lose precision, b. sext/zext may wrap,
2567 /// c. other casts depend on pointer size.
2568 if (CI->getOperand(0) == OldInduction &&
2569 it->getOpcode() == Instruction::Trunc) {
2570 Value *ScalarCast = Builder.CreateCast(CI->getOpcode(), Induction,
2572 Value *Broadcasted = getBroadcastInstrs(ScalarCast);
2573 for (unsigned Part = 0; Part < UF; ++Part)
2574 Entry[Part] = getConsecutiveVector(Broadcasted, VF * Part, false);
2577 /// Vectorize casts.
2578 Type *DestTy = (VF == 1) ? CI->getType() :
2579 VectorType::get(CI->getType(), VF);
2581 VectorParts &A = getVectorValue(it->getOperand(0));
2582 for (unsigned Part = 0; Part < UF; ++Part)
2583 Entry[Part] = Builder.CreateCast(CI->getOpcode(), A[Part], DestTy);
2587 case Instruction::Call: {
2588 // Ignore dbg intrinsics.
2589 if (isa<DbgInfoIntrinsic>(it))
2591 setDebugLocFromInst(Builder, it);
2593 Module *M = BB->getParent()->getParent();
2594 CallInst *CI = cast<CallInst>(it);
2595 Intrinsic::ID ID = getIntrinsicIDForCall(CI, TLI);
2596 assert(ID && "Not an intrinsic call!");
2598 case Intrinsic::lifetime_end:
2599 case Intrinsic::lifetime_start:
2600 scalarizeInstruction(it);
2603 for (unsigned Part = 0; Part < UF; ++Part) {
2604 SmallVector<Value *, 4> Args;
2605 for (unsigned i = 0, ie = CI->getNumArgOperands(); i != ie; ++i) {
2606 VectorParts &Arg = getVectorValue(CI->getArgOperand(i));
2607 Args.push_back(Arg[Part]);
2609 Type *Tys[] = {CI->getType()};
2611 Tys[0] = VectorType::get(CI->getType()->getScalarType(), VF);
2613 Function *F = Intrinsic::getDeclaration(M, ID, Tys);
2614 Entry[Part] = Builder.CreateCall(F, Args);
2622 // All other instructions are unsupported. Scalarize them.
2623 scalarizeInstruction(it);
2626 }// end of for_each instr.
2629 void InnerLoopVectorizer::updateAnalysis() {
2630 // Forget the original basic block.
2631 SE->forgetLoop(OrigLoop);
2633 // Update the dominator tree information.
2634 assert(DT->properlyDominates(LoopBypassBlocks.front(), LoopExitBlock) &&
2635 "Entry does not dominate exit.");
2637 for (unsigned I = 1, E = LoopBypassBlocks.size(); I != E; ++I)
2638 DT->addNewBlock(LoopBypassBlocks[I], LoopBypassBlocks[I-1]);
2639 DT->addNewBlock(LoopVectorPreHeader, LoopBypassBlocks.back());
2640 DT->addNewBlock(LoopVectorBody, LoopVectorPreHeader);
2641 DT->addNewBlock(LoopMiddleBlock, LoopBypassBlocks.front());
2642 DT->addNewBlock(LoopScalarPreHeader, LoopMiddleBlock);
2643 DT->changeImmediateDominator(LoopScalarBody, LoopScalarPreHeader);
2644 DT->changeImmediateDominator(LoopExitBlock, LoopMiddleBlock);
2646 DEBUG(DT->verifyAnalysis());
2649 bool LoopVectorizationLegality::canVectorizeWithIfConvert() {
2650 if (!EnableIfConversion)
2653 assert(TheLoop->getNumBlocks() > 1 && "Single block loops are vectorizable");
2654 std::vector<BasicBlock*> &LoopBlocks = TheLoop->getBlocksVector();
2656 // A list of pointers that we can safely read and write to.
2657 SmallPtrSet<Value *, 8> SafePointes;
2659 // Collect safe addresses.
2660 for (unsigned i = 0, e = LoopBlocks.size(); i < e; ++i) {
2661 BasicBlock *BB = LoopBlocks[i];
2663 if (blockNeedsPredication(BB))
2666 for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) {
2667 if (LoadInst *LI = dyn_cast<LoadInst>(I))
2668 SafePointes.insert(LI->getPointerOperand());
2669 else if (StoreInst *SI = dyn_cast<StoreInst>(I))
2670 SafePointes.insert(SI->getPointerOperand());
2674 // Collect the blocks that need predication.
2675 for (unsigned i = 0, e = LoopBlocks.size(); i < e; ++i) {
2676 BasicBlock *BB = LoopBlocks[i];
2678 // We don't support switch statements inside loops.
2679 if (!isa<BranchInst>(BB->getTerminator()))
2682 // We must be able to predicate all blocks that need to be predicated.
2683 if (blockNeedsPredication(BB) && !blockCanBePredicated(BB, SafePointes))
2687 // We can if-convert this loop.
2691 bool LoopVectorizationLegality::canVectorize() {
2692 // We must have a loop in canonical form. Loops with indirectbr in them cannot
2693 // be canonicalized.
2694 if (!TheLoop->getLoopPreheader())
2697 // We can only vectorize innermost loops.
2698 if (TheLoop->getSubLoopsVector().size())
2701 // We must have a single backedge.
2702 if (TheLoop->getNumBackEdges() != 1)
2705 // We must have a single exiting block.
2706 if (!TheLoop->getExitingBlock())
2709 unsigned NumBlocks = TheLoop->getNumBlocks();
2711 // Check if we can if-convert non single-bb loops.
2712 if (NumBlocks != 1 && !canVectorizeWithIfConvert()) {
2713 DEBUG(dbgs() << "LV: Can't if-convert the loop.\n");
2717 // We need to have a loop header.
2718 BasicBlock *Latch = TheLoop->getLoopLatch();
2719 DEBUG(dbgs() << "LV: Found a loop: " <<
2720 TheLoop->getHeader()->getName() << "\n");
2722 // ScalarEvolution needs to be able to find the exit count.
2723 const SCEV *ExitCount = SE->getBackedgeTakenCount(TheLoop);
2724 if (ExitCount == SE->getCouldNotCompute()) {
2725 DEBUG(dbgs() << "LV: SCEV could not compute the loop exit count.\n");
2729 // Do not loop-vectorize loops with a tiny trip count.
2730 unsigned TC = SE->getSmallConstantTripCount(TheLoop, Latch);
2731 if (TC > 0u && TC < TinyTripCountVectorThreshold) {
2732 DEBUG(dbgs() << "LV: Found a loop with a very small trip count. " <<
2733 "This loop is not worth vectorizing.\n");
2737 // Check if we can vectorize the instructions and CFG in this loop.
2738 if (!canVectorizeInstrs()) {
2739 DEBUG(dbgs() << "LV: Can't vectorize the instructions or CFG\n");
2743 // Go over each instruction and look at memory deps.
2744 if (!canVectorizeMemory()) {
2745 DEBUG(dbgs() << "LV: Can't vectorize due to memory conflicts\n");
2749 // Collect all of the variables that remain uniform after vectorization.
2750 collectLoopUniforms();
2752 DEBUG(dbgs() << "LV: We can vectorize this loop" <<
2753 (PtrRtCheck.Need ? " (with a runtime bound check)" : "")
2756 // Okay! We can vectorize. At this point we don't have any other mem analysis
2757 // which may limit our maximum vectorization factor, so just return true with
2762 static Type *convertPointerToIntegerType(DataLayout &DL, Type *Ty) {
2763 if (Ty->isPointerTy())
2764 return DL.getIntPtrType(Ty);
2769 static Type* getWiderType(DataLayout &DL, Type *Ty0, Type *Ty1) {
2770 Ty0 = convertPointerToIntegerType(DL, Ty0);
2771 Ty1 = convertPointerToIntegerType(DL, Ty1);
2772 if (Ty0->getScalarSizeInBits() > Ty1->getScalarSizeInBits())
2777 /// \brief Check that the instruction has outside loop users and is not an
2778 /// identified reduction variable.
2779 static bool hasOutsideLoopUser(const Loop *TheLoop, Instruction *Inst,
2780 SmallPtrSet<Value *, 4> &Reductions) {
2781 // Reduction instructions are allowed to have exit users. All other
2782 // instructions must not have external users.
2783 if (!Reductions.count(Inst))
2784 //Check that all of the users of the loop are inside the BB.
2785 for (Value::use_iterator I = Inst->use_begin(), E = Inst->use_end();
2787 Instruction *U = cast<Instruction>(*I);
2788 // This user may be a reduction exit value.
2789 if (!TheLoop->contains(U)) {
2790 DEBUG(dbgs() << "LV: Found an outside user for : "<< *U << "\n");
2797 bool LoopVectorizationLegality::canVectorizeInstrs() {
2798 BasicBlock *PreHeader = TheLoop->getLoopPreheader();
2799 BasicBlock *Header = TheLoop->getHeader();
2801 // Look for the attribute signaling the absence of NaNs.
2802 Function &F = *Header->getParent();
2803 if (F.hasFnAttribute("no-nans-fp-math"))
2804 HasFunNoNaNAttr = F.getAttributes().getAttribute(
2805 AttributeSet::FunctionIndex,
2806 "no-nans-fp-math").getValueAsString() == "true";
2808 // For each block in the loop.
2809 for (Loop::block_iterator bb = TheLoop->block_begin(),
2810 be = TheLoop->block_end(); bb != be; ++bb) {
2812 // Scan the instructions in the block and look for hazards.
2813 for (BasicBlock::iterator it = (*bb)->begin(), e = (*bb)->end(); it != e;
2816 if (PHINode *Phi = dyn_cast<PHINode>(it)) {
2817 Type *PhiTy = Phi->getType();
2818 // Check that this PHI type is allowed.
2819 if (!PhiTy->isIntegerTy() &&
2820 !PhiTy->isFloatingPointTy() &&
2821 !PhiTy->isPointerTy()) {
2822 DEBUG(dbgs() << "LV: Found an non-int non-pointer PHI.\n");
2826 // If this PHINode is not in the header block, then we know that we
2827 // can convert it to select during if-conversion. No need to check if
2828 // the PHIs in this block are induction or reduction variables.
2829 if (*bb != Header) {
2830 // Check that this instruction has no outside users or is an
2831 // identified reduction value with an outside user.
2832 if(!hasOutsideLoopUser(TheLoop, it, AllowedExit))
2837 // We only allow if-converted PHIs with more than two incoming values.
2838 if (Phi->getNumIncomingValues() != 2) {
2839 DEBUG(dbgs() << "LV: Found an invalid PHI.\n");
2843 // This is the value coming from the preheader.
2844 Value *StartValue = Phi->getIncomingValueForBlock(PreHeader);
2845 // Check if this is an induction variable.
2846 InductionKind IK = isInductionVariable(Phi);
2848 if (IK_NoInduction != IK) {
2849 // Get the widest type.
2851 WidestIndTy = convertPointerToIntegerType(*DL, PhiTy);
2853 WidestIndTy = getWiderType(*DL, PhiTy, WidestIndTy);
2855 // Int inductions are special because we only allow one IV.
2856 if (IK == IK_IntInduction) {
2857 // Use the phi node with the widest type as induction. Use the last
2858 // one if there are multiple (no good reason for doing this other
2859 // than it is expedient).
2860 if (!Induction || PhiTy == WidestIndTy)
2864 DEBUG(dbgs() << "LV: Found an induction variable.\n");
2865 Inductions[Phi] = InductionInfo(StartValue, IK);
2869 if (AddReductionVar(Phi, RK_IntegerAdd)) {
2870 DEBUG(dbgs() << "LV: Found an ADD reduction PHI."<< *Phi <<"\n");
2873 if (AddReductionVar(Phi, RK_IntegerMult)) {
2874 DEBUG(dbgs() << "LV: Found a MUL reduction PHI."<< *Phi <<"\n");
2877 if (AddReductionVar(Phi, RK_IntegerOr)) {
2878 DEBUG(dbgs() << "LV: Found an OR reduction PHI."<< *Phi <<"\n");
2881 if (AddReductionVar(Phi, RK_IntegerAnd)) {
2882 DEBUG(dbgs() << "LV: Found an AND reduction PHI."<< *Phi <<"\n");
2885 if (AddReductionVar(Phi, RK_IntegerXor)) {
2886 DEBUG(dbgs() << "LV: Found a XOR reduction PHI."<< *Phi <<"\n");
2889 if (AddReductionVar(Phi, RK_IntegerMinMax)) {
2890 DEBUG(dbgs() << "LV: Found a MINMAX reduction PHI."<< *Phi <<"\n");
2893 if (AddReductionVar(Phi, RK_FloatMult)) {
2894 DEBUG(dbgs() << "LV: Found an FMult reduction PHI."<< *Phi <<"\n");
2897 if (AddReductionVar(Phi, RK_FloatAdd)) {
2898 DEBUG(dbgs() << "LV: Found an FAdd reduction PHI."<< *Phi <<"\n");
2901 if (AddReductionVar(Phi, RK_FloatMinMax)) {
2902 DEBUG(dbgs() << "LV: Found an float MINMAX reduction PHI."<< *Phi <<
2907 DEBUG(dbgs() << "LV: Found an unidentified PHI."<< *Phi <<"\n");
2909 }// end of PHI handling
2911 // We still don't handle functions. However, we can ignore dbg intrinsic
2912 // calls and we do handle certain intrinsic and libm functions.
2913 CallInst *CI = dyn_cast<CallInst>(it);
2914 if (CI && !getIntrinsicIDForCall(CI, TLI) && !isa<DbgInfoIntrinsic>(CI)) {
2915 DEBUG(dbgs() << "LV: Found a call site.\n");
2919 // Check that the instruction return type is vectorizable.
2920 if (!VectorType::isValidElementType(it->getType()) &&
2921 !it->getType()->isVoidTy()) {
2922 DEBUG(dbgs() << "LV: Found unvectorizable type." << "\n");
2926 // Check that the stored type is vectorizable.
2927 if (StoreInst *ST = dyn_cast<StoreInst>(it)) {
2928 Type *T = ST->getValueOperand()->getType();
2929 if (!VectorType::isValidElementType(T))
2933 // Reduction instructions are allowed to have exit users.
2934 // All other instructions must not have external users.
2935 if (hasOutsideLoopUser(TheLoop, it, AllowedExit))
2943 DEBUG(dbgs() << "LV: Did not find one integer induction var.\n");
2944 if (Inductions.empty())
2951 void LoopVectorizationLegality::collectLoopUniforms() {
2952 // We now know that the loop is vectorizable!
2953 // Collect variables that will remain uniform after vectorization.
2954 std::vector<Value*> Worklist;
2955 BasicBlock *Latch = TheLoop->getLoopLatch();
2957 // Start with the conditional branch and walk up the block.
2958 Worklist.push_back(Latch->getTerminator()->getOperand(0));
2960 while (Worklist.size()) {
2961 Instruction *I = dyn_cast<Instruction>(Worklist.back());
2962 Worklist.pop_back();
2964 // Look at instructions inside this loop.
2965 // Stop when reaching PHI nodes.
2966 // TODO: we need to follow values all over the loop, not only in this block.
2967 if (!I || !TheLoop->contains(I) || isa<PHINode>(I))
2970 // This is a known uniform.
2973 // Insert all operands.
2974 Worklist.insert(Worklist.end(), I->op_begin(), I->op_end());
2979 /// \brief Analyses memory accesses in a loop.
2981 /// Checks whether run time pointer checks are needed and builds sets for data
2982 /// dependence checking.
2983 class AccessAnalysis {
2985 /// \brief Read or write access location.
2986 typedef PointerIntPair<Value *, 1, bool> MemAccessInfo;
2987 typedef SmallPtrSet<MemAccessInfo, 8> MemAccessInfoSet;
2989 /// \brief Set of potential dependent memory accesses.
2990 typedef EquivalenceClasses<MemAccessInfo> DepCandidates;
2992 AccessAnalysis(DataLayout *Dl, DepCandidates &DA) :
2993 DL(Dl), DepCands(DA), AreAllWritesIdentified(true),
2994 AreAllReadsIdentified(true), IsRTCheckNeeded(false) {}
2996 /// \brief Register a load and whether it is only read from.
2997 void addLoad(Value *Ptr, bool IsReadOnly) {
2998 Accesses.insert(MemAccessInfo(Ptr, false));
3000 ReadOnlyPtr.insert(Ptr);
3003 /// \brief Register a store.
3004 void addStore(Value *Ptr) {
3005 Accesses.insert(MemAccessInfo(Ptr, true));
3008 /// \brief Check whether we can check the pointers at runtime for
3009 /// non-intersection.
3010 bool canCheckPtrAtRT(LoopVectorizationLegality::RuntimePointerCheck &RtCheck,
3011 unsigned &NumComparisons, ScalarEvolution *SE,
3014 /// \brief Goes over all memory accesses, checks whether a RT check is needed
3015 /// and builds sets of dependent accesses.
3016 void buildDependenceSets() {
3017 // Process read-write pointers first.
3018 processMemAccesses(false);
3019 // Next, process read pointers.
3020 processMemAccesses(true);
3023 bool isRTCheckNeeded() { return IsRTCheckNeeded; }
3025 bool isDependencyCheckNeeded() { return !CheckDeps.empty(); }
3027 MemAccessInfoSet &getDependenciesToCheck() { return CheckDeps; }
3030 typedef SetVector<MemAccessInfo> PtrAccessSet;
3031 typedef DenseMap<Value*, MemAccessInfo> UnderlyingObjToAccessMap;
3033 /// \brief Go over all memory access or only the deferred ones if
3034 /// \p UseDeferred is true and check whether runtime pointer checks are needed
3035 /// and build sets of dependency check candidates.
3036 void processMemAccesses(bool UseDeferred);
3038 /// Set of all accesses.
3039 PtrAccessSet Accesses;
3041 /// Set of access to check after all writes have been processed.
3042 PtrAccessSet DeferredAccesses;
3044 /// Map of pointers to last access encountered.
3045 UnderlyingObjToAccessMap ObjToLastAccess;
3047 /// Set of accesses that need a further dependence check.
3048 MemAccessInfoSet CheckDeps;
3050 /// Set of pointers that are read only.
3051 SmallPtrSet<Value*, 16> ReadOnlyPtr;
3053 /// Set of underlying objects already written to.
3054 SmallPtrSet<Value*, 16> WriteObjects;
3058 /// Sets of potentially dependent accesses - members of one set share an
3059 /// underlying pointer. The set "CheckDeps" identfies which sets really need a
3060 /// dependence check.
3061 DepCandidates &DepCands;
3063 bool AreAllWritesIdentified;
3064 bool AreAllReadsIdentified;
3065 bool IsRTCheckNeeded;
3068 } // end anonymous namespace
3070 /// \brief Check whether a pointer can participate in a runtime bounds check.
3071 static bool hasComputableBounds(ScalarEvolution *SE, Value *Ptr) {
3072 const SCEV *PtrScev = SE->getSCEV(Ptr);
3073 const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(PtrScev);
3077 return AR->isAffine();
3080 bool AccessAnalysis::canCheckPtrAtRT(
3081 LoopVectorizationLegality::RuntimePointerCheck &RtCheck,
3082 unsigned &NumComparisons, ScalarEvolution *SE,
3084 // Find pointers with computable bounds. We are going to use this information
3085 // to place a runtime bound check.
3086 unsigned NumReadPtrChecks = 0;
3087 unsigned NumWritePtrChecks = 0;
3088 bool CanDoRT = true;
3090 bool IsDepCheckNeeded = isDependencyCheckNeeded();
3091 // We assign consecutive id to access from different dependence sets.
3092 // Accesses within the same set don't need a runtime check.
3093 unsigned RunningDepId = 1;
3094 DenseMap<Value *, unsigned> DepSetId;
3096 for (PtrAccessSet::iterator AI = Accesses.begin(), AE = Accesses.end();
3098 const MemAccessInfo &Access = *AI;
3099 Value *Ptr = Access.getPointer();
3100 bool IsWrite = Access.getInt();
3102 // Just add write checks if we have both.
3103 if (!IsWrite && Accesses.count(MemAccessInfo(Ptr, true)))
3107 ++NumWritePtrChecks;
3111 if (hasComputableBounds(SE, Ptr)) {
3112 // The id of the dependence set.
3115 if (IsDepCheckNeeded) {
3116 Value *Leader = DepCands.getLeaderValue(Access).getPointer();
3117 unsigned &LeaderId = DepSetId[Leader];
3119 LeaderId = RunningDepId++;
3122 // Each access has its own dependence set.
3123 DepId = RunningDepId++;
3125 RtCheck.insert(SE, TheLoop, Ptr, IsWrite, DepId);
3127 DEBUG(dbgs() << "LV: Found a runtime check ptr:" << *Ptr <<"\n");
3133 if (IsDepCheckNeeded && CanDoRT && RunningDepId == 2)
3134 NumComparisons = 0; // Only one dependence set.
3136 NumComparisons = (NumWritePtrChecks * (NumReadPtrChecks +
3137 NumWritePtrChecks - 1));
3141 static bool isFunctionScopeIdentifiedObject(Value *Ptr) {
3142 return isNoAliasArgument(Ptr) || isNoAliasCall(Ptr) || isa<AllocaInst>(Ptr);
3145 void AccessAnalysis::processMemAccesses(bool UseDeferred) {
3146 // We process the set twice: first we process read-write pointers, last we
3147 // process read-only pointers. This allows us to skip dependence tests for
3148 // read-only pointers.
3150 PtrAccessSet &S = UseDeferred ? DeferredAccesses : Accesses;
3151 for (PtrAccessSet::iterator AI = S.begin(), AE = S.end(); AI != AE; ++AI) {
3152 const MemAccessInfo &Access = *AI;
3153 Value *Ptr = Access.getPointer();
3154 bool IsWrite = Access.getInt();
3156 DepCands.insert(Access);
3158 // Memorize read-only pointers for later processing and skip them in the
3159 // first round (they need to be checked after we have seen all write
3160 // pointers). Note: we also mark pointer that are not consecutive as
3161 // "read-only" pointers (so that we check "a[b[i]] +="). Hence, we need the
3162 // second check for "!IsWrite".
3163 bool IsReadOnlyPtr = ReadOnlyPtr.count(Ptr) && !IsWrite;
3164 if (!UseDeferred && IsReadOnlyPtr) {
3165 DeferredAccesses.insert(Access);
3169 bool NeedDepCheck = false;
3170 // Check whether there is the possiblity of dependency because of underlying
3171 // objects being the same.
3172 typedef SmallVector<Value*, 16> ValueVector;
3173 ValueVector TempObjects;
3174 GetUnderlyingObjects(Ptr, TempObjects, DL);
3175 for (ValueVector::iterator UI = TempObjects.begin(), UE = TempObjects.end();
3177 Value *UnderlyingObj = *UI;
3179 // If this is a write then it needs to be an identified object. If this a
3180 // read and all writes (so far) are identified function scope objects we
3181 // don't need an identified underlying object but only an Argument (the
3182 // next write is going to invalidate this assumption if it is
3184 // This is a micro-optimization for the case where all writes are
3185 // identified and we have one argument pointer.
3186 // Otherwise, we do need a runtime check.
3187 if ((IsWrite && !isFunctionScopeIdentifiedObject(UnderlyingObj)) ||
3188 (!IsWrite && (!AreAllWritesIdentified ||
3189 !isa<Argument>(UnderlyingObj)) &&
3190 !isIdentifiedObject(UnderlyingObj))) {
3191 DEBUG(dbgs() << "LV: Found an unidentified " <<
3192 (IsWrite ? "write" : "read" ) << " ptr:" << *UnderlyingObj <<
3194 IsRTCheckNeeded = (IsRTCheckNeeded ||
3195 !isIdentifiedObject(UnderlyingObj) ||
3196 !AreAllReadsIdentified);
3199 AreAllWritesIdentified = false;
3201 AreAllReadsIdentified = false;
3204 // If this is a write - check other reads and writes for conflicts. If
3205 // this is a read only check other writes for conflicts (but only if there
3206 // is no other write to the ptr - this is an optimization to catch "a[i] =
3207 // a[i] + " without having to do a dependence check).
3208 if ((IsWrite || IsReadOnlyPtr) && WriteObjects.count(UnderlyingObj))
3209 NeedDepCheck = true;
3212 WriteObjects.insert(UnderlyingObj);
3214 // Create sets of pointers connected by shared underlying objects.
3215 UnderlyingObjToAccessMap::iterator Prev =
3216 ObjToLastAccess.find(UnderlyingObj);
3217 if (Prev != ObjToLastAccess.end())
3218 DepCands.unionSets(Access, Prev->second);
3220 ObjToLastAccess[UnderlyingObj] = Access;
3224 CheckDeps.insert(Access);
3229 /// \brief Checks memory dependences among accesses to the same underlying
3230 /// object to determine whether there vectorization is legal or not (and at
3231 /// which vectorization factor).
3233 /// This class works under the assumption that we already checked that memory
3234 /// locations with different underlying pointers are "must-not alias".
3235 /// We use the ScalarEvolution framework to symbolically evalutate access
3236 /// functions pairs. Since we currently don't restructure the loop we can rely
3237 /// on the program order of memory accesses to determine their safety.
3238 /// At the moment we will only deem accesses as safe for:
3239 /// * A negative constant distance assuming program order.
3241 /// Safe: tmp = a[i + 1]; OR a[i + 1] = x;
3242 /// a[i] = tmp; y = a[i];
3244 /// The latter case is safe because later checks guarantuee that there can't
3245 /// be a cycle through a phi node (that is, we check that "x" and "y" is not
3246 /// the same variable: a header phi can only be an induction or a reduction, a
3247 /// reduction can't have a memory sink, an induction can't have a memory
3248 /// source). This is important and must not be violated (or we have to
3249 /// resort to checking for cycles through memory).
3251 /// * A positive constant distance assuming program order that is bigger
3252 /// than the biggest memory access.
3254 /// tmp = a[i] OR b[i] = x
3255 /// a[i+2] = tmp y = b[i+2];
3257 /// Safe distance: 2 x sizeof(a[0]), and 2 x sizeof(b[0]), respectively.
3259 /// * Zero distances and all accesses have the same size.
3261 class MemoryDepChecker {
3263 typedef PointerIntPair<Value *, 1, bool> MemAccessInfo;
3264 typedef SmallPtrSet<MemAccessInfo, 8> MemAccessInfoSet;
3266 MemoryDepChecker(ScalarEvolution *Se, DataLayout *Dl, const Loop *L) :
3267 SE(Se), DL(Dl), InnermostLoop(L), AccessIdx(0) {}
3269 /// \brief Register the location (instructions are given increasing numbers)
3270 /// of a write access.
3271 void addAccess(StoreInst *SI) {
3272 Value *Ptr = SI->getPointerOperand();
3273 Accesses[MemAccessInfo(Ptr, true)].push_back(AccessIdx);
3274 InstMap.push_back(SI);
3278 /// \brief Register the location (instructions are given increasing numbers)
3279 /// of a write access.
3280 void addAccess(LoadInst *LI) {
3281 Value *Ptr = LI->getPointerOperand();
3282 Accesses[MemAccessInfo(Ptr, false)].push_back(AccessIdx);
3283 InstMap.push_back(LI);
3287 /// \brief Check whether the dependencies between the accesses are safe.
3289 /// Only checks sets with elements in \p CheckDeps.
3290 bool areDepsSafe(AccessAnalysis::DepCandidates &AccessSets,
3291 MemAccessInfoSet &CheckDeps);
3293 /// \brief The maximum number of bytes of a vector register we can vectorize
3294 /// the accesses safely with.
3295 unsigned getMaxSafeDepDistBytes() { return MaxSafeDepDistBytes; }
3298 ScalarEvolution *SE;
3300 const Loop *InnermostLoop;
3302 /// \brief Maps access locations (ptr, read/write) to program order.
3303 DenseMap<MemAccessInfo, std::vector<unsigned> > Accesses;
3305 /// \brief Memory access instructions in program order.
3306 SmallVector<Instruction *, 16> InstMap;
3308 /// \brief The program order index to be used for the next instruction.
3311 // We can access this many bytes in parallel safely.
3312 unsigned MaxSafeDepDistBytes;
3314 /// \brief Check whether there is a plausible dependence between the two
3317 /// Access \p A must happen before \p B in program order. The two indices
3318 /// identify the index into the program order map.
3320 /// This function checks whether there is a plausible dependence (or the
3321 /// absence of such can't be proved) between the two accesses. If there is a
3322 /// plausible dependence but the dependence distance is bigger than one
3323 /// element access it records this distance in \p MaxSafeDepDistBytes (if this
3324 /// distance is smaller than any other distance encountered so far).
3325 /// Otherwise, this function returns true signaling a possible dependence.
3326 bool isDependent(const MemAccessInfo &A, unsigned AIdx,
3327 const MemAccessInfo &B, unsigned BIdx);
3329 /// \brief Check whether the data dependence could prevent store-load
3331 bool couldPreventStoreLoadForward(unsigned Distance, unsigned TypeByteSize);
3334 } // end anonymous namespace
3336 static bool isInBoundsGep(Value *Ptr) {
3337 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Ptr))
3338 return GEP->isInBounds();
3342 /// \brief Check whether the access through \p Ptr has a constant stride.
3343 static int isStridedPtr(ScalarEvolution *SE, DataLayout *DL, Value *Ptr,
3345 const Type *Ty = Ptr->getType();
3346 assert(Ty->isPointerTy() && "Unexpected non ptr");
3348 // Make sure that the pointer does not point to aggregate types.
3349 const PointerType *PtrTy = cast<PointerType>(Ty);
3350 if (PtrTy->getElementType()->isAggregateType()) {
3351 DEBUG(dbgs() << "LV: Bad stride - Not a pointer to a scalar type" << *Ptr <<
3356 const SCEV *PtrScev = SE->getSCEV(Ptr);
3357 const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(PtrScev);
3359 DEBUG(dbgs() << "LV: Bad stride - Not an AddRecExpr pointer "
3360 << *Ptr << " SCEV: " << *PtrScev << "\n");
3364 // The accesss function must stride over the innermost loop.
3365 if (Lp != AR->getLoop()) {
3366 DEBUG(dbgs() << "LV: Bad stride - Not striding over innermost loop " <<
3367 *Ptr << " SCEV: " << *PtrScev << "\n");
3370 // The address calculation must not wrap. Otherwise, a dependence could be
3372 // An inbounds getelementptr that is a AddRec with a unit stride
3373 // cannot wrap per definition. The unit stride requirement is checked later.
3374 // An getelementptr without an inbounds attribute and unit stride would have
3375 // to access the pointer value "0" which is undefined behavior in address
3376 // space 0, therefore we can also vectorize this case.
3377 bool IsInBoundsGEP = isInBoundsGep(Ptr);
3378 bool IsNoWrapAddRec = AR->getNoWrapFlags(SCEV::NoWrapMask);
3379 bool IsInAddressSpaceZero = PtrTy->getAddressSpace() == 0;
3380 if (!IsNoWrapAddRec && !IsInBoundsGEP && !IsInAddressSpaceZero) {
3381 DEBUG(dbgs() << "LV: Bad stride - Pointer may wrap in the address space "
3382 << *Ptr << " SCEV: " << *PtrScev << "\n");
3386 // Check the step is constant.
3387 const SCEV *Step = AR->getStepRecurrence(*SE);
3389 // Calculate the pointer stride and check if it is consecutive.
3390 const SCEVConstant *C = dyn_cast<SCEVConstant>(Step);
3392 DEBUG(dbgs() << "LV: Bad stride - Not a constant strided " << *Ptr <<
3393 " SCEV: " << *PtrScev << "\n");
3397 int64_t Size = DL->getTypeAllocSize(PtrTy->getElementType());
3398 const APInt &APStepVal = C->getValue()->getValue();
3400 // Huge step value - give up.
3401 if (APStepVal.getBitWidth() > 64)
3404 int64_t StepVal = APStepVal.getSExtValue();
3407 int64_t Stride = StepVal / Size;
3408 int64_t Rem = StepVal % Size;
3412 // If the SCEV could wrap but we have an inbounds gep with a unit stride we
3413 // know we can't "wrap around the address space". In case of address space
3414 // zero we know that this won't happen without triggering undefined behavior.
3415 if (!IsNoWrapAddRec && (IsInBoundsGEP || IsInAddressSpaceZero) &&
3416 Stride != 1 && Stride != -1)
3422 bool MemoryDepChecker::couldPreventStoreLoadForward(unsigned Distance,
3423 unsigned TypeByteSize) {
3424 // If loads occur at a distance that is not a multiple of a feasible vector
3425 // factor store-load forwarding does not take place.
3426 // Positive dependences might cause troubles because vectorizing them might
3427 // prevent store-load forwarding making vectorized code run a lot slower.
3428 // a[i] = a[i-3] ^ a[i-8];
3429 // The stores to a[i:i+1] don't align with the stores to a[i-3:i-2] and
3430 // hence on your typical architecture store-load forwarding does not take
3431 // place. Vectorizing in such cases does not make sense.
3432 // Store-load forwarding distance.
3433 const unsigned NumCyclesForStoreLoadThroughMemory = 8*TypeByteSize;
3434 // Maximum vector factor.
3435 unsigned MaxVFWithoutSLForwardIssues = MaxVectorWidth*TypeByteSize;
3436 if(MaxSafeDepDistBytes < MaxVFWithoutSLForwardIssues)
3437 MaxVFWithoutSLForwardIssues = MaxSafeDepDistBytes;
3439 for (unsigned vf = 2*TypeByteSize; vf <= MaxVFWithoutSLForwardIssues;
3441 if (Distance % vf && Distance / vf < NumCyclesForStoreLoadThroughMemory) {
3442 MaxVFWithoutSLForwardIssues = (vf >>=1);
3447 if (MaxVFWithoutSLForwardIssues< 2*TypeByteSize) {
3448 DEBUG(dbgs() << "LV: Distance " << Distance <<
3449 " that could cause a store-load forwarding conflict\n");
3453 if (MaxVFWithoutSLForwardIssues < MaxSafeDepDistBytes &&
3454 MaxVFWithoutSLForwardIssues != MaxVectorWidth*TypeByteSize)
3455 MaxSafeDepDistBytes = MaxVFWithoutSLForwardIssues;
3459 bool MemoryDepChecker::isDependent(const MemAccessInfo &A, unsigned AIdx,
3460 const MemAccessInfo &B, unsigned BIdx) {
3461 assert (AIdx < BIdx && "Must pass arguments in program order");
3463 Value *APtr = A.getPointer();
3464 Value *BPtr = B.getPointer();
3465 bool AIsWrite = A.getInt();
3466 bool BIsWrite = B.getInt();
3468 // Two reads are independent.
3469 if (!AIsWrite && !BIsWrite)
3472 const SCEV *AScev = SE->getSCEV(APtr);
3473 const SCEV *BScev = SE->getSCEV(BPtr);
3475 int StrideAPtr = isStridedPtr(SE, DL, APtr, InnermostLoop);
3476 int StrideBPtr = isStridedPtr(SE, DL, BPtr, InnermostLoop);
3478 const SCEV *Src = AScev;
3479 const SCEV *Sink = BScev;
3481 // If the induction step is negative we have to invert source and sink of the
3483 if (StrideAPtr < 0) {
3486 std::swap(APtr, BPtr);
3487 std::swap(Src, Sink);
3488 std::swap(AIsWrite, BIsWrite);
3489 std::swap(AIdx, BIdx);
3490 std::swap(StrideAPtr, StrideBPtr);
3493 const SCEV *Dist = SE->getMinusSCEV(Sink, Src);
3495 DEBUG(dbgs() << "LV: Src Scev: " << *Src << "Sink Scev: " << *Sink
3496 << "(Induction step: " << StrideAPtr << ")\n");
3497 DEBUG(dbgs() << "LV: Distance for " << *InstMap[AIdx] << " to "
3498 << *InstMap[BIdx] << ": " << *Dist << "\n");
3500 // Need consecutive accesses. We don't want to vectorize
3501 // "A[B[i]] += ..." and similar code or pointer arithmetic that could wrap in
3502 // the address space.
3503 if (!StrideAPtr || !StrideBPtr || StrideAPtr != StrideBPtr){
3504 DEBUG(dbgs() << "Non-consecutive pointer access\n");
3508 const SCEVConstant *C = dyn_cast<SCEVConstant>(Dist);
3510 DEBUG(dbgs() << "LV: Dependence because of non constant distance\n");
3514 Type *ATy = APtr->getType()->getPointerElementType();
3515 Type *BTy = BPtr->getType()->getPointerElementType();
3516 unsigned TypeByteSize = DL->getTypeAllocSize(ATy);
3518 // Negative distances are not plausible dependencies.
3519 const APInt &Val = C->getValue()->getValue();
3520 if (Val.isNegative()) {
3521 bool IsTrueDataDependence = (AIsWrite && !BIsWrite);
3522 if (IsTrueDataDependence &&
3523 (couldPreventStoreLoadForward(Val.abs().getZExtValue(), TypeByteSize) ||
3527 DEBUG(dbgs() << "LV: Dependence is negative: NoDep\n");
3531 // Write to the same location with the same size.
3532 // Could be improved to assert type sizes are the same (i32 == float, etc).
3536 DEBUG(dbgs() << "LV: Zero dependence difference but different types");
3540 assert(Val.isStrictlyPositive() && "Expect a positive value");
3542 // Positive distance bigger than max vectorization factor.
3545 "LV: ReadWrite-Write positive dependency with different types");
3549 unsigned Distance = (unsigned) Val.getZExtValue();
3551 // Bail out early if passed-in parameters make vectorization not feasible.
3552 unsigned ForcedFactor = VectorizationFactor ? VectorizationFactor : 1;
3553 unsigned ForcedUnroll = VectorizationUnroll ? VectorizationUnroll : 1;
3555 // The distance must be bigger than the size needed for a vectorized version
3556 // of the operation and the size of the vectorized operation must not be
3557 // bigger than the currrent maximum size.
3558 if (Distance < 2*TypeByteSize ||
3559 2*TypeByteSize > MaxSafeDepDistBytes ||
3560 Distance < TypeByteSize * ForcedUnroll * ForcedFactor) {
3561 DEBUG(dbgs() << "LV: Failure because of Positive distance "
3562 << Val.getSExtValue() << "\n");
3566 MaxSafeDepDistBytes = Distance < MaxSafeDepDistBytes ?
3567 Distance : MaxSafeDepDistBytes;
3569 bool IsTrueDataDependence = (!AIsWrite && BIsWrite);
3570 if (IsTrueDataDependence &&
3571 couldPreventStoreLoadForward(Distance, TypeByteSize))
3574 DEBUG(dbgs() << "LV: Positive distance " << Val.getSExtValue() <<
3575 " with max VF=" << MaxSafeDepDistBytes/TypeByteSize << "\n");
3581 MemoryDepChecker::areDepsSafe(AccessAnalysis::DepCandidates &AccessSets,
3582 MemAccessInfoSet &CheckDeps) {
3584 MaxSafeDepDistBytes = -1U;
3585 while (!CheckDeps.empty()) {
3586 MemAccessInfo CurAccess = *CheckDeps.begin();
3588 // Get the relevant memory access set.
3589 EquivalenceClasses<MemAccessInfo>::iterator I =
3590 AccessSets.findValue(AccessSets.getLeaderValue(CurAccess));
3592 // Check accesses within this set.
3593 EquivalenceClasses<MemAccessInfo>::member_iterator AI, AE;
3594 AI = AccessSets.member_begin(I), AE = AccessSets.member_end();
3596 // Check every access pair.
3598 CheckDeps.erase(*AI);
3599 EquivalenceClasses<MemAccessInfo>::member_iterator OI = llvm::next(AI);
3601 // Check every accessing instruction pair in program order.
3602 for (std::vector<unsigned>::iterator I1 = Accesses[*AI].begin(),
3603 I1E = Accesses[*AI].end(); I1 != I1E; ++I1)
3604 for (std::vector<unsigned>::iterator I2 = Accesses[*OI].begin(),
3605 I2E = Accesses[*OI].end(); I2 != I2E; ++I2) {
3606 if (*I1 < *I2 && isDependent(*AI, *I1, *OI, *I2))
3608 if (*I2 < *I1 && isDependent(*OI, *I2, *AI, *I1))
3619 bool LoopVectorizationLegality::canVectorizeMemory() {
3621 typedef SmallVector<Value*, 16> ValueVector;
3622 typedef SmallPtrSet<Value*, 16> ValueSet;
3624 // Holds the Load and Store *instructions*.
3628 // Holds all the different accesses in the loop.
3629 unsigned NumReads = 0;
3630 unsigned NumReadWrites = 0;
3632 PtrRtCheck.Pointers.clear();
3633 PtrRtCheck.Need = false;
3635 const bool IsAnnotatedParallel = TheLoop->isAnnotatedParallel();
3636 MemoryDepChecker DepChecker(SE, DL, TheLoop);
3639 for (Loop::block_iterator bb = TheLoop->block_begin(),
3640 be = TheLoop->block_end(); bb != be; ++bb) {
3642 // Scan the BB and collect legal loads and stores.
3643 for (BasicBlock::iterator it = (*bb)->begin(), e = (*bb)->end(); it != e;
3646 // If this is a load, save it. If this instruction can read from memory
3647 // but is not a load, then we quit. Notice that we don't handle function
3648 // calls that read or write.
3649 if (it->mayReadFromMemory()) {
3650 // Many math library functions read the rounding mode. We will only
3651 // vectorize a loop if it contains known function calls that don't set
3652 // the flag. Therefore, it is safe to ignore this read from memory.
3653 CallInst *Call = dyn_cast<CallInst>(it);
3654 if (Call && getIntrinsicIDForCall(Call, TLI))
3657 LoadInst *Ld = dyn_cast<LoadInst>(it);
3658 if (!Ld) return false;
3659 if (!Ld->isSimple() && !IsAnnotatedParallel) {
3660 DEBUG(dbgs() << "LV: Found a non-simple load.\n");
3663 Loads.push_back(Ld);
3664 DepChecker.addAccess(Ld);
3668 // Save 'store' instructions. Abort if other instructions write to memory.
3669 if (it->mayWriteToMemory()) {
3670 StoreInst *St = dyn_cast<StoreInst>(it);
3671 if (!St) return false;
3672 if (!St->isSimple() && !IsAnnotatedParallel) {
3673 DEBUG(dbgs() << "LV: Found a non-simple store.\n");
3676 Stores.push_back(St);
3677 DepChecker.addAccess(St);
3682 // Now we have two lists that hold the loads and the stores.
3683 // Next, we find the pointers that they use.
3685 // Check if we see any stores. If there are no stores, then we don't
3686 // care if the pointers are *restrict*.
3687 if (!Stores.size()) {
3688 DEBUG(dbgs() << "LV: Found a read-only loop!\n");
3692 AccessAnalysis::DepCandidates DependentAccesses;
3693 AccessAnalysis Accesses(DL, DependentAccesses);
3695 // Holds the analyzed pointers. We don't want to call GetUnderlyingObjects
3696 // multiple times on the same object. If the ptr is accessed twice, once
3697 // for read and once for write, it will only appear once (on the write
3698 // list). This is okay, since we are going to check for conflicts between
3699 // writes and between reads and writes, but not between reads and reads.
3702 ValueVector::iterator I, IE;
3703 for (I = Stores.begin(), IE = Stores.end(); I != IE; ++I) {
3704 StoreInst *ST = cast<StoreInst>(*I);
3705 Value* Ptr = ST->getPointerOperand();
3707 if (isUniform(Ptr)) {
3708 DEBUG(dbgs() << "LV: We don't allow storing to uniform addresses\n");
3712 // If we did *not* see this pointer before, insert it to the read-write
3713 // list. At this phase it is only a 'write' list.
3714 if (Seen.insert(Ptr)) {
3716 Accesses.addStore(Ptr);
3720 if (IsAnnotatedParallel) {
3722 << "LV: A loop annotated parallel, ignore memory dependency "
3727 SmallPtrSet<Value *, 16> ReadOnlyPtr;
3728 for (I = Loads.begin(), IE = Loads.end(); I != IE; ++I) {
3729 LoadInst *LD = cast<LoadInst>(*I);
3730 Value* Ptr = LD->getPointerOperand();
3731 // If we did *not* see this pointer before, insert it to the
3732 // read list. If we *did* see it before, then it is already in
3733 // the read-write list. This allows us to vectorize expressions
3734 // such as A[i] += x; Because the address of A[i] is a read-write
3735 // pointer. This only works if the index of A[i] is consecutive.
3736 // If the address of i is unknown (for example A[B[i]]) then we may
3737 // read a few words, modify, and write a few words, and some of the
3738 // words may be written to the same address.
3739 bool IsReadOnlyPtr = false;
3740 if (Seen.insert(Ptr) || !isStridedPtr(SE, DL, Ptr, TheLoop)) {
3742 IsReadOnlyPtr = true;
3744 Accesses.addLoad(Ptr, IsReadOnlyPtr);
3747 // If we write (or read-write) to a single destination and there are no
3748 // other reads in this loop then is it safe to vectorize.
3749 if (NumReadWrites == 1 && NumReads == 0) {
3750 DEBUG(dbgs() << "LV: Found a write-only loop!\n");
3754 // Build dependence sets and check whether we need a runtime pointer bounds
3756 Accesses.buildDependenceSets();
3757 bool NeedRTCheck = Accesses.isRTCheckNeeded();
3759 // Find pointers with computable bounds. We are going to use this information
3760 // to place a runtime bound check.
3761 unsigned NumComparisons = 0;
3762 bool CanDoRT = false;
3764 CanDoRT = Accesses.canCheckPtrAtRT(PtrRtCheck, NumComparisons, SE, TheLoop);
3767 DEBUG(dbgs() << "LV: We need to do " << NumComparisons <<
3768 " pointer comparisons.\n");
3770 // If we only have one set of dependences to check pointers among we don't
3771 // need a runtime check.
3772 if (NumComparisons == 0 && NeedRTCheck)
3773 NeedRTCheck = false;
3775 // Check that we did not collect too many pointers or found a unsizeable
3777 if (!CanDoRT || NumComparisons > RuntimeMemoryCheckThreshold) {
3783 DEBUG(dbgs() << "LV: We can perform a memory runtime check if needed.\n");
3786 if (NeedRTCheck && !CanDoRT) {
3787 DEBUG(dbgs() << "LV: We can't vectorize because we can't find " <<
3788 "the array bounds.\n");
3793 PtrRtCheck.Need = NeedRTCheck;
3795 bool CanVecMem = true;
3796 if (Accesses.isDependencyCheckNeeded()) {
3797 DEBUG(dbgs() << "LV: Checking memory dependencies\n");
3798 CanVecMem = DepChecker.areDepsSafe(DependentAccesses,
3799 Accesses.getDependenciesToCheck());
3800 MaxSafeDepDistBytes = DepChecker.getMaxSafeDepDistBytes();
3803 DEBUG(dbgs() << "LV: We "<< (NeedRTCheck ? "" : "don't") <<
3804 " need a runtime memory check.\n");
3809 static bool hasMultipleUsesOf(Instruction *I,
3810 SmallPtrSet<Instruction *, 8> &Insts) {
3811 unsigned NumUses = 0;
3812 for(User::op_iterator Use = I->op_begin(), E = I->op_end(); Use != E; ++Use) {
3813 if (Insts.count(dyn_cast<Instruction>(*Use)))
3822 static bool areAllUsesIn(Instruction *I, SmallPtrSet<Instruction *, 8> &Set) {
3823 for(User::op_iterator Use = I->op_begin(), E = I->op_end(); Use != E; ++Use)
3824 if (!Set.count(dyn_cast<Instruction>(*Use)))
3829 bool LoopVectorizationLegality::AddReductionVar(PHINode *Phi,
3830 ReductionKind Kind) {
3831 if (Phi->getNumIncomingValues() != 2)
3834 // Reduction variables are only found in the loop header block.
3835 if (Phi->getParent() != TheLoop->getHeader())
3838 // Obtain the reduction start value from the value that comes from the loop
3840 Value *RdxStart = Phi->getIncomingValueForBlock(TheLoop->getLoopPreheader());
3842 // ExitInstruction is the single value which is used outside the loop.
3843 // We only allow for a single reduction value to be used outside the loop.
3844 // This includes users of the reduction, variables (which form a cycle
3845 // which ends in the phi node).
3846 Instruction *ExitInstruction = 0;
3847 // Indicates that we found a reduction operation in our scan.
3848 bool FoundReduxOp = false;
3850 // We start with the PHI node and scan for all of the users of this
3851 // instruction. All users must be instructions that can be used as reduction
3852 // variables (such as ADD). We must have a single out-of-block user. The cycle
3853 // must include the original PHI.
3854 bool FoundStartPHI = false;
3856 // To recognize min/max patterns formed by a icmp select sequence, we store
3857 // the number of instruction we saw from the recognized min/max pattern,
3858 // to make sure we only see exactly the two instructions.
3859 unsigned NumCmpSelectPatternInst = 0;
3860 ReductionInstDesc ReduxDesc(false, 0);
3862 SmallPtrSet<Instruction *, 8> VisitedInsts;
3863 SmallVector<Instruction *, 8> Worklist;
3864 Worklist.push_back(Phi);
3865 VisitedInsts.insert(Phi);
3867 // A value in the reduction can be used:
3868 // - By the reduction:
3869 // - Reduction operation:
3870 // - One use of reduction value (safe).
3871 // - Multiple use of reduction value (not safe).
3873 // - All uses of the PHI must be the reduction (safe).
3874 // - Otherwise, not safe.
3875 // - By one instruction outside of the loop (safe).
3876 // - By further instructions outside of the loop (not safe).
3877 // - By an instruction that is not part of the reduction (not safe).
3879 // * An instruction type other than PHI or the reduction operation.
3880 // * A PHI in the header other than the initial PHI.
3881 while (!Worklist.empty()) {
3882 Instruction *Cur = Worklist.back();
3883 Worklist.pop_back();
3886 // If the instruction has no users then this is a broken chain and can't be
3887 // a reduction variable.
3888 if (Cur->use_empty())
3891 bool IsAPhi = isa<PHINode>(Cur);
3893 // A header PHI use other than the original PHI.
3894 if (Cur != Phi && IsAPhi && Cur->getParent() == Phi->getParent())
3897 // Reductions of instructions such as Div, and Sub is only possible if the
3898 // LHS is the reduction variable.
3899 if (!Cur->isCommutative() && !IsAPhi && !isa<SelectInst>(Cur) &&
3900 !isa<ICmpInst>(Cur) && !isa<FCmpInst>(Cur) &&
3901 !VisitedInsts.count(dyn_cast<Instruction>(Cur->getOperand(0))))
3904 // Any reduction instruction must be of one of the allowed kinds.
3905 ReduxDesc = isReductionInstr(Cur, Kind, ReduxDesc);
3906 if (!ReduxDesc.IsReduction)
3909 // A reduction operation must only have one use of the reduction value.
3910 if (!IsAPhi && Kind != RK_IntegerMinMax && Kind != RK_FloatMinMax &&
3911 hasMultipleUsesOf(Cur, VisitedInsts))
3914 // All inputs to a PHI node must be a reduction value.
3915 if(IsAPhi && Cur != Phi && !areAllUsesIn(Cur, VisitedInsts))
3918 if (Kind == RK_IntegerMinMax && (isa<ICmpInst>(Cur) ||
3919 isa<SelectInst>(Cur)))
3920 ++NumCmpSelectPatternInst;
3921 if (Kind == RK_FloatMinMax && (isa<FCmpInst>(Cur) ||
3922 isa<SelectInst>(Cur)))
3923 ++NumCmpSelectPatternInst;
3925 // Check whether we found a reduction operator.
3926 FoundReduxOp |= !IsAPhi;
3928 // Process users of current instruction. Push non PHI nodes after PHI nodes
3929 // onto the stack. This way we are going to have seen all inputs to PHI
3930 // nodes once we get to them.
3931 SmallVector<Instruction *, 8> NonPHIs;
3932 SmallVector<Instruction *, 8> PHIs;
3933 for (Value::use_iterator UI = Cur->use_begin(), E = Cur->use_end(); UI != E;
3935 Instruction *Usr = cast<Instruction>(*UI);
3937 // Check if we found the exit user.
3938 BasicBlock *Parent = Usr->getParent();
3939 if (!TheLoop->contains(Parent)) {
3940 // Exit if you find multiple outside users or if the header phi node is
3941 // being used. In this case the user uses the value of the previous
3942 // iteration, in which case we would loose "VF-1" iterations of the
3943 // reduction operation if we vectorize.
3944 if (ExitInstruction != 0 || Cur == Phi)
3947 ExitInstruction = Cur;
3951 // Process instructions only once (termination).
3952 if (VisitedInsts.insert(Usr)) {
3953 if (isa<PHINode>(Usr))
3954 PHIs.push_back(Usr);
3956 NonPHIs.push_back(Usr);
3958 // Remember that we completed the cycle.
3960 FoundStartPHI = true;
3962 Worklist.append(PHIs.begin(), PHIs.end());
3963 Worklist.append(NonPHIs.begin(), NonPHIs.end());
3966 // This means we have seen one but not the other instruction of the
3967 // pattern or more than just a select and cmp.
3968 if ((Kind == RK_IntegerMinMax || Kind == RK_FloatMinMax) &&
3969 NumCmpSelectPatternInst != 2)
3972 if (!FoundStartPHI || !FoundReduxOp || !ExitInstruction)
3975 // We found a reduction var if we have reached the original phi node and we
3976 // only have a single instruction with out-of-loop users.
3978 // This instruction is allowed to have out-of-loop users.
3979 AllowedExit.insert(ExitInstruction);
3981 // Save the description of this reduction variable.
3982 ReductionDescriptor RD(RdxStart, ExitInstruction, Kind,
3983 ReduxDesc.MinMaxKind);
3984 Reductions[Phi] = RD;
3985 // We've ended the cycle. This is a reduction variable if we have an
3986 // outside user and it has a binary op.
3991 /// Returns true if the instruction is a Select(ICmp(X, Y), X, Y) instruction
3992 /// pattern corresponding to a min(X, Y) or max(X, Y).
3993 LoopVectorizationLegality::ReductionInstDesc
3994 LoopVectorizationLegality::isMinMaxSelectCmpPattern(Instruction *I,
3995 ReductionInstDesc &Prev) {
3997 assert((isa<ICmpInst>(I) || isa<FCmpInst>(I) || isa<SelectInst>(I)) &&
3998 "Expect a select instruction");
3999 Instruction *Cmp = 0;
4000 SelectInst *Select = 0;
4002 // We must handle the select(cmp()) as a single instruction. Advance to the
4004 if ((Cmp = dyn_cast<ICmpInst>(I)) || (Cmp = dyn_cast<FCmpInst>(I))) {
4005 if (!Cmp->hasOneUse() || !(Select = dyn_cast<SelectInst>(*I->use_begin())))
4006 return ReductionInstDesc(false, I);
4007 return ReductionInstDesc(Select, Prev.MinMaxKind);
4010 // Only handle single use cases for now.
4011 if (!(Select = dyn_cast<SelectInst>(I)))
4012 return ReductionInstDesc(false, I);
4013 if (!(Cmp = dyn_cast<ICmpInst>(I->getOperand(0))) &&
4014 !(Cmp = dyn_cast<FCmpInst>(I->getOperand(0))))
4015 return ReductionInstDesc(false, I);
4016 if (!Cmp->hasOneUse())
4017 return ReductionInstDesc(false, I);
4022 // Look for a min/max pattern.
4023 if (m_UMin(m_Value(CmpLeft), m_Value(CmpRight)).match(Select))
4024 return ReductionInstDesc(Select, MRK_UIntMin);
4025 else if (m_UMax(m_Value(CmpLeft), m_Value(CmpRight)).match(Select))
4026 return ReductionInstDesc(Select, MRK_UIntMax);
4027 else if (m_SMax(m_Value(CmpLeft), m_Value(CmpRight)).match(Select))
4028 return ReductionInstDesc(Select, MRK_SIntMax);
4029 else if (m_SMin(m_Value(CmpLeft), m_Value(CmpRight)).match(Select))
4030 return ReductionInstDesc(Select, MRK_SIntMin);
4031 else if (m_OrdFMin(m_Value(CmpLeft), m_Value(CmpRight)).match(Select))
4032 return ReductionInstDesc(Select, MRK_FloatMin);
4033 else if (m_OrdFMax(m_Value(CmpLeft), m_Value(CmpRight)).match(Select))
4034 return ReductionInstDesc(Select, MRK_FloatMax);
4035 else if (m_UnordFMin(m_Value(CmpLeft), m_Value(CmpRight)).match(Select))
4036 return ReductionInstDesc(Select, MRK_FloatMin);
4037 else if (m_UnordFMax(m_Value(CmpLeft), m_Value(CmpRight)).match(Select))
4038 return ReductionInstDesc(Select, MRK_FloatMax);
4040 return ReductionInstDesc(false, I);
4043 LoopVectorizationLegality::ReductionInstDesc
4044 LoopVectorizationLegality::isReductionInstr(Instruction *I,
4046 ReductionInstDesc &Prev) {
4047 bool FP = I->getType()->isFloatingPointTy();
4048 bool FastMath = (FP && I->isCommutative() && I->isAssociative());
4049 switch (I->getOpcode()) {
4051 return ReductionInstDesc(false, I);
4052 case Instruction::PHI:
4053 if (FP && (Kind != RK_FloatMult && Kind != RK_FloatAdd &&
4054 Kind != RK_FloatMinMax))
4055 return ReductionInstDesc(false, I);
4056 return ReductionInstDesc(I, Prev.MinMaxKind);
4057 case Instruction::Sub:
4058 case Instruction::Add:
4059 return ReductionInstDesc(Kind == RK_IntegerAdd, I);
4060 case Instruction::Mul:
4061 return ReductionInstDesc(Kind == RK_IntegerMult, I);
4062 case Instruction::And:
4063 return ReductionInstDesc(Kind == RK_IntegerAnd, I);
4064 case Instruction::Or:
4065 return ReductionInstDesc(Kind == RK_IntegerOr, I);
4066 case Instruction::Xor:
4067 return ReductionInstDesc(Kind == RK_IntegerXor, I);
4068 case Instruction::FMul:
4069 return ReductionInstDesc(Kind == RK_FloatMult && FastMath, I);
4070 case Instruction::FAdd:
4071 return ReductionInstDesc(Kind == RK_FloatAdd && FastMath, I);
4072 case Instruction::FCmp:
4073 case Instruction::ICmp:
4074 case Instruction::Select:
4075 if (Kind != RK_IntegerMinMax &&
4076 (!HasFunNoNaNAttr || Kind != RK_FloatMinMax))
4077 return ReductionInstDesc(false, I);
4078 return isMinMaxSelectCmpPattern(I, Prev);
4082 LoopVectorizationLegality::InductionKind
4083 LoopVectorizationLegality::isInductionVariable(PHINode *Phi) {
4084 Type *PhiTy = Phi->getType();
4085 // We only handle integer and pointer inductions variables.
4086 if (!PhiTy->isIntegerTy() && !PhiTy->isPointerTy())
4087 return IK_NoInduction;
4089 // Check that the PHI is consecutive.
4090 const SCEV *PhiScev = SE->getSCEV(Phi);
4091 const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(PhiScev);
4093 DEBUG(dbgs() << "LV: PHI is not a poly recurrence.\n");
4094 return IK_NoInduction;
4096 const SCEV *Step = AR->getStepRecurrence(*SE);
4098 // Integer inductions need to have a stride of one.
4099 if (PhiTy->isIntegerTy()) {
4101 return IK_IntInduction;
4102 if (Step->isAllOnesValue())
4103 return IK_ReverseIntInduction;
4104 return IK_NoInduction;
4107 // Calculate the pointer stride and check if it is consecutive.
4108 const SCEVConstant *C = dyn_cast<SCEVConstant>(Step);
4110 return IK_NoInduction;
4112 assert(PhiTy->isPointerTy() && "The PHI must be a pointer");
4113 uint64_t Size = DL->getTypeAllocSize(PhiTy->getPointerElementType());
4114 if (C->getValue()->equalsInt(Size))
4115 return IK_PtrInduction;
4116 else if (C->getValue()->equalsInt(0 - Size))
4117 return IK_ReversePtrInduction;
4119 return IK_NoInduction;
4122 bool LoopVectorizationLegality::isInductionVariable(const Value *V) {
4123 Value *In0 = const_cast<Value*>(V);
4124 PHINode *PN = dyn_cast_or_null<PHINode>(In0);
4128 return Inductions.count(PN);
4131 bool LoopVectorizationLegality::blockNeedsPredication(BasicBlock *BB) {
4132 assert(TheLoop->contains(BB) && "Unknown block used");
4134 // Blocks that do not dominate the latch need predication.
4135 BasicBlock* Latch = TheLoop->getLoopLatch();
4136 return !DT->dominates(BB, Latch);
4139 bool LoopVectorizationLegality::blockCanBePredicated(BasicBlock *BB,
4140 SmallPtrSet<Value *, 8>& SafePtrs) {
4141 for (BasicBlock::iterator it = BB->begin(), e = BB->end(); it != e; ++it) {
4142 // We might be able to hoist the load.
4143 if (it->mayReadFromMemory()) {
4144 LoadInst *LI = dyn_cast<LoadInst>(it);
4145 if (!LI || !SafePtrs.count(LI->getPointerOperand()))
4149 // We don't predicate stores at the moment.
4150 if (it->mayWriteToMemory() || it->mayThrow())
4153 // The instructions below can trap.
4154 switch (it->getOpcode()) {
4156 case Instruction::UDiv:
4157 case Instruction::SDiv:
4158 case Instruction::URem:
4159 case Instruction::SRem:
4167 LoopVectorizationCostModel::VectorizationFactor
4168 LoopVectorizationCostModel::selectVectorizationFactor(bool OptForSize,
4170 // Width 1 means no vectorize
4171 VectorizationFactor Factor = { 1U, 0U };
4172 if (OptForSize && Legal->getRuntimePointerCheck()->Need) {
4173 DEBUG(dbgs() << "LV: Aborting. Runtime ptr check is required in Os.\n");
4177 // Find the trip count.
4178 unsigned TC = SE->getSmallConstantTripCount(TheLoop, TheLoop->getLoopLatch());
4179 DEBUG(dbgs() << "LV: Found trip count:"<<TC<<"\n");
4181 unsigned WidestType = getWidestType();
4182 unsigned WidestRegister = TTI.getRegisterBitWidth(true);
4183 unsigned MaxSafeDepDist = -1U;
4184 if (Legal->getMaxSafeDepDistBytes() != -1U)
4185 MaxSafeDepDist = Legal->getMaxSafeDepDistBytes() * 8;
4186 WidestRegister = ((WidestRegister < MaxSafeDepDist) ?
4187 WidestRegister : MaxSafeDepDist);
4188 unsigned MaxVectorSize = WidestRegister / WidestType;
4189 DEBUG(dbgs() << "LV: The Widest type: " << WidestType << " bits.\n");
4190 DEBUG(dbgs() << "LV: The Widest register is:" << WidestRegister << "bits.\n");
4192 if (MaxVectorSize == 0) {
4193 DEBUG(dbgs() << "LV: The target has no vector registers.\n");
4197 assert(MaxVectorSize <= 32 && "Did not expect to pack so many elements"
4198 " into one vector!");
4200 unsigned VF = MaxVectorSize;
4202 // If we optimize the program for size, avoid creating the tail loop.
4204 // If we are unable to calculate the trip count then don't try to vectorize.
4206 DEBUG(dbgs() << "LV: Aborting. A tail loop is required in Os.\n");
4210 // Find the maximum SIMD width that can fit within the trip count.
4211 VF = TC % MaxVectorSize;
4216 // If the trip count that we found modulo the vectorization factor is not
4217 // zero then we require a tail.
4219 DEBUG(dbgs() << "LV: Aborting. A tail loop is required in Os.\n");
4225 assert(isPowerOf2_32(UserVF) && "VF needs to be a power of two");
4226 DEBUG(dbgs() << "LV: Using user VF "<<UserVF<<".\n");
4228 Factor.Width = UserVF;
4232 float Cost = expectedCost(1);
4234 DEBUG(dbgs() << "LV: Scalar loop costs: "<< (int)Cost << ".\n");
4235 for (unsigned i=2; i <= VF; i*=2) {
4236 // Notice that the vector loop needs to be executed less times, so
4237 // we need to divide the cost of the vector loops by the width of
4238 // the vector elements.
4239 float VectorCost = expectedCost(i) / (float)i;
4240 DEBUG(dbgs() << "LV: Vector loop of width "<< i << " costs: " <<
4241 (int)VectorCost << ".\n");
4242 if (VectorCost < Cost) {
4248 DEBUG(dbgs() << "LV: Selecting VF = : "<< Width << ".\n");
4249 Factor.Width = Width;
4250 Factor.Cost = Width * Cost;
4254 unsigned LoopVectorizationCostModel::getWidestType() {
4255 unsigned MaxWidth = 8;
4258 for (Loop::block_iterator bb = TheLoop->block_begin(),
4259 be = TheLoop->block_end(); bb != be; ++bb) {
4260 BasicBlock *BB = *bb;
4262 // For each instruction in the loop.
4263 for (BasicBlock::iterator it = BB->begin(), e = BB->end(); it != e; ++it) {
4264 Type *T = it->getType();
4266 // Only examine Loads, Stores and PHINodes.
4267 if (!isa<LoadInst>(it) && !isa<StoreInst>(it) && !isa<PHINode>(it))
4270 // Examine PHI nodes that are reduction variables.
4271 if (PHINode *PN = dyn_cast<PHINode>(it))
4272 if (!Legal->getReductionVars()->count(PN))
4275 // Examine the stored values.
4276 if (StoreInst *ST = dyn_cast<StoreInst>(it))
4277 T = ST->getValueOperand()->getType();
4279 // Ignore loaded pointer types and stored pointer types that are not
4280 // consecutive. However, we do want to take consecutive stores/loads of
4281 // pointer vectors into account.
4282 if (T->isPointerTy() && !isConsecutiveLoadOrStore(it))
4285 MaxWidth = std::max(MaxWidth,
4286 (unsigned)DL->getTypeSizeInBits(T->getScalarType()));
4294 LoopVectorizationCostModel::selectUnrollFactor(bool OptForSize,
4297 unsigned LoopCost) {
4299 // -- The unroll heuristics --
4300 // We unroll the loop in order to expose ILP and reduce the loop overhead.
4301 // There are many micro-architectural considerations that we can't predict
4302 // at this level. For example frontend pressure (on decode or fetch) due to
4303 // code size, or the number and capabilities of the execution ports.
4305 // We use the following heuristics to select the unroll factor:
4306 // 1. If the code has reductions the we unroll in order to break the cross
4307 // iteration dependency.
4308 // 2. If the loop is really small then we unroll in order to reduce the loop
4310 // 3. We don't unroll if we think that we will spill registers to memory due
4311 // to the increased register pressure.
4313 // Use the user preference, unless 'auto' is selected.
4317 // When we optimize for size we don't unroll.
4321 // We used the distance for the unroll factor.
4322 if (Legal->getMaxSafeDepDistBytes() != -1U)
4325 // Do not unroll loops with a relatively small trip count.
4326 unsigned TC = SE->getSmallConstantTripCount(TheLoop,
4327 TheLoop->getLoopLatch());
4328 if (TC > 1 && TC < TinyTripCountUnrollThreshold)
4331 unsigned TargetVectorRegisters = TTI.getNumberOfRegisters(true);
4332 DEBUG(dbgs() << "LV: The target has " << TargetVectorRegisters <<
4333 " vector registers\n");
4335 LoopVectorizationCostModel::RegisterUsage R = calculateRegisterUsage();
4336 // We divide by these constants so assume that we have at least one
4337 // instruction that uses at least one register.
4338 R.MaxLocalUsers = std::max(R.MaxLocalUsers, 1U);
4339 R.NumInstructions = std::max(R.NumInstructions, 1U);
4341 // We calculate the unroll factor using the following formula.
4342 // Subtract the number of loop invariants from the number of available
4343 // registers. These registers are used by all of the unrolled instances.
4344 // Next, divide the remaining registers by the number of registers that is
4345 // required by the loop, in order to estimate how many parallel instances
4346 // fit without causing spills.
4347 unsigned UF = (TargetVectorRegisters - R.LoopInvariantRegs) / R.MaxLocalUsers;
4349 // Clamp the unroll factor ranges to reasonable factors.
4350 unsigned MaxUnrollSize = TTI.getMaximumUnrollFactor();
4352 // If we did not calculate the cost for VF (because the user selected the VF)
4353 // then we calculate the cost of VF here.
4355 LoopCost = expectedCost(VF);
4357 // Clamp the calculated UF to be between the 1 and the max unroll factor
4358 // that the target allows.
4359 if (UF > MaxUnrollSize)
4364 bool HasReductions = Legal->getReductionVars()->size();
4366 // Decide if we want to unroll if we decided that it is legal to vectorize
4367 // but not profitable.
4369 if (TheLoop->getNumBlocks() > 1 || !HasReductions ||
4370 LoopCost > SmallLoopCost)
4376 if (HasReductions) {
4377 DEBUG(dbgs() << "LV: Unrolling because of reductions. \n");
4381 // We want to unroll tiny loops in order to reduce the loop overhead.
4382 // We assume that the cost overhead is 1 and we use the cost model
4383 // to estimate the cost of the loop and unroll until the cost of the
4384 // loop overhead is about 5% of the cost of the loop.
4385 DEBUG(dbgs() << "LV: Loop cost is "<< LoopCost <<" \n");
4386 if (LoopCost < SmallLoopCost) {
4387 DEBUG(dbgs() << "LV: Unrolling to reduce branch cost. \n");
4388 unsigned NewUF = SmallLoopCost / (LoopCost + 1);
4389 return std::min(NewUF, UF);
4392 DEBUG(dbgs() << "LV: Not Unrolling. \n");
4396 LoopVectorizationCostModel::RegisterUsage
4397 LoopVectorizationCostModel::calculateRegisterUsage() {
4398 // This function calculates the register usage by measuring the highest number
4399 // of values that are alive at a single location. Obviously, this is a very
4400 // rough estimation. We scan the loop in a topological order in order and
4401 // assign a number to each instruction. We use RPO to ensure that defs are
4402 // met before their users. We assume that each instruction that has in-loop
4403 // users starts an interval. We record every time that an in-loop value is
4404 // used, so we have a list of the first and last occurrences of each
4405 // instruction. Next, we transpose this data structure into a multi map that
4406 // holds the list of intervals that *end* at a specific location. This multi
4407 // map allows us to perform a linear search. We scan the instructions linearly
4408 // and record each time that a new interval starts, by placing it in a set.
4409 // If we find this value in the multi-map then we remove it from the set.
4410 // The max register usage is the maximum size of the set.
4411 // We also search for instructions that are defined outside the loop, but are
4412 // used inside the loop. We need this number separately from the max-interval
4413 // usage number because when we unroll, loop-invariant values do not take
4415 LoopBlocksDFS DFS(TheLoop);
4419 R.NumInstructions = 0;
4421 // Each 'key' in the map opens a new interval. The values
4422 // of the map are the index of the 'last seen' usage of the
4423 // instruction that is the key.
4424 typedef DenseMap<Instruction*, unsigned> IntervalMap;
4425 // Maps instruction to its index.
4426 DenseMap<unsigned, Instruction*> IdxToInstr;
4427 // Marks the end of each interval.
4428 IntervalMap EndPoint;
4429 // Saves the list of instruction indices that are used in the loop.
4430 SmallSet<Instruction*, 8> Ends;
4431 // Saves the list of values that are used in the loop but are
4432 // defined outside the loop, such as arguments and constants.
4433 SmallPtrSet<Value*, 8> LoopInvariants;
4436 for (LoopBlocksDFS::RPOIterator bb = DFS.beginRPO(),
4437 be = DFS.endRPO(); bb != be; ++bb) {
4438 R.NumInstructions += (*bb)->size();
4439 for (BasicBlock::iterator it = (*bb)->begin(), e = (*bb)->end(); it != e;
4441 Instruction *I = it;
4442 IdxToInstr[Index++] = I;
4444 // Save the end location of each USE.
4445 for (unsigned i = 0; i < I->getNumOperands(); ++i) {
4446 Value *U = I->getOperand(i);
4447 Instruction *Instr = dyn_cast<Instruction>(U);
4449 // Ignore non-instruction values such as arguments, constants, etc.
4450 if (!Instr) continue;
4452 // If this instruction is outside the loop then record it and continue.
4453 if (!TheLoop->contains(Instr)) {
4454 LoopInvariants.insert(Instr);
4458 // Overwrite previous end points.
4459 EndPoint[Instr] = Index;
4465 // Saves the list of intervals that end with the index in 'key'.
4466 typedef SmallVector<Instruction*, 2> InstrList;
4467 DenseMap<unsigned, InstrList> TransposeEnds;
4469 // Transpose the EndPoints to a list of values that end at each index.
4470 for (IntervalMap::iterator it = EndPoint.begin(), e = EndPoint.end();
4472 TransposeEnds[it->second].push_back(it->first);
4474 SmallSet<Instruction*, 8> OpenIntervals;
4475 unsigned MaxUsage = 0;
4478 DEBUG(dbgs() << "LV(REG): Calculating max register usage:\n");
4479 for (unsigned int i = 0; i < Index; ++i) {
4480 Instruction *I = IdxToInstr[i];
4481 // Ignore instructions that are never used within the loop.
4482 if (!Ends.count(I)) continue;
4484 // Remove all of the instructions that end at this location.
4485 InstrList &List = TransposeEnds[i];
4486 for (unsigned int j=0, e = List.size(); j < e; ++j)
4487 OpenIntervals.erase(List[j]);
4489 // Count the number of live interals.
4490 MaxUsage = std::max(MaxUsage, OpenIntervals.size());
4492 DEBUG(dbgs() << "LV(REG): At #" << i << " Interval # " <<
4493 OpenIntervals.size() <<"\n");
4495 // Add the current instruction to the list of open intervals.
4496 OpenIntervals.insert(I);
4499 unsigned Invariant = LoopInvariants.size();
4500 DEBUG(dbgs() << "LV(REG): Found max usage: " << MaxUsage << " \n");
4501 DEBUG(dbgs() << "LV(REG): Found invariant usage: " << Invariant << " \n");
4502 DEBUG(dbgs() << "LV(REG): LoopSize: " << R.NumInstructions << " \n");
4504 R.LoopInvariantRegs = Invariant;
4505 R.MaxLocalUsers = MaxUsage;
4509 unsigned LoopVectorizationCostModel::expectedCost(unsigned VF) {
4513 for (Loop::block_iterator bb = TheLoop->block_begin(),
4514 be = TheLoop->block_end(); bb != be; ++bb) {
4515 unsigned BlockCost = 0;
4516 BasicBlock *BB = *bb;
4518 // For each instruction in the old loop.
4519 for (BasicBlock::iterator it = BB->begin(), e = BB->end(); it != e; ++it) {
4520 // Skip dbg intrinsics.
4521 if (isa<DbgInfoIntrinsic>(it))
4524 unsigned C = getInstructionCost(it, VF);
4526 DEBUG(dbgs() << "LV: Found an estimated cost of "<< C <<" for VF " <<
4527 VF << " For instruction: "<< *it << "\n");
4530 // We assume that if-converted blocks have a 50% chance of being executed.
4531 // When the code is scalar then some of the blocks are avoided due to CF.
4532 // When the code is vectorized we execute all code paths.
4533 if (VF == 1 && Legal->blockNeedsPredication(*bb))
4542 /// \brief Check whether the address computation for a non-consecutive memory
4543 /// access looks like an unlikely candidate for being merged into the indexing
4546 /// We look for a GEP which has one index that is an induction variable and all
4547 /// other indices are loop invariant. If the stride of this access is also
4548 /// within a small bound we decide that this address computation can likely be
4549 /// merged into the addressing mode.
4550 /// In all other cases, we identify the address computation as complex.
4551 static bool isLikelyComplexAddressComputation(Value *Ptr,
4552 LoopVectorizationLegality *Legal,
4553 ScalarEvolution *SE,
4554 const Loop *TheLoop) {
4555 GetElementPtrInst *Gep = dyn_cast<GetElementPtrInst>(Ptr);
4559 // We are looking for a gep with all loop invariant indices except for one
4560 // which should be an induction variable.
4561 unsigned NumOperands = Gep->getNumOperands();
4562 for (unsigned i = 1; i < NumOperands; ++i) {
4563 Value *Opd = Gep->getOperand(i);
4564 if (!SE->isLoopInvariant(SE->getSCEV(Opd), TheLoop) &&
4565 !Legal->isInductionVariable(Opd))
4569 // Now we know we have a GEP ptr, %inv, %ind, %inv. Make sure that the step
4570 // can likely be merged into the address computation.
4571 unsigned MaxMergeDistance = 64;
4573 const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(SE->getSCEV(Ptr));
4577 // Check the step is constant.
4578 const SCEV *Step = AddRec->getStepRecurrence(*SE);
4579 // Calculate the pointer stride and check if it is consecutive.
4580 const SCEVConstant *C = dyn_cast<SCEVConstant>(Step);
4584 const APInt &APStepVal = C->getValue()->getValue();
4586 // Huge step value - give up.
4587 if (APStepVal.getBitWidth() > 64)
4590 int64_t StepVal = APStepVal.getSExtValue();
4592 return StepVal > MaxMergeDistance;
4596 LoopVectorizationCostModel::getInstructionCost(Instruction *I, unsigned VF) {
4597 // If we know that this instruction will remain uniform, check the cost of
4598 // the scalar version.
4599 if (Legal->isUniformAfterVectorization(I))
4602 Type *RetTy = I->getType();
4603 Type *VectorTy = ToVectorTy(RetTy, VF);
4605 // TODO: We need to estimate the cost of intrinsic calls.
4606 switch (I->getOpcode()) {
4607 case Instruction::GetElementPtr:
4608 // We mark this instruction as zero-cost because the cost of GEPs in
4609 // vectorized code depends on whether the corresponding memory instruction
4610 // is scalarized or not. Therefore, we handle GEPs with the memory
4611 // instruction cost.
4613 case Instruction::Br: {
4614 return TTI.getCFInstrCost(I->getOpcode());
4616 case Instruction::PHI:
4617 //TODO: IF-converted IFs become selects.
4619 case Instruction::Add:
4620 case Instruction::FAdd:
4621 case Instruction::Sub:
4622 case Instruction::FSub:
4623 case Instruction::Mul:
4624 case Instruction::FMul:
4625 case Instruction::UDiv:
4626 case Instruction::SDiv:
4627 case Instruction::FDiv:
4628 case Instruction::URem:
4629 case Instruction::SRem:
4630 case Instruction::FRem:
4631 case Instruction::Shl:
4632 case Instruction::LShr:
4633 case Instruction::AShr:
4634 case Instruction::And:
4635 case Instruction::Or:
4636 case Instruction::Xor: {
4637 // Certain instructions can be cheaper to vectorize if they have a constant
4638 // second vector operand. One example of this are shifts on x86.
4639 TargetTransformInfo::OperandValueKind Op1VK =
4640 TargetTransformInfo::OK_AnyValue;
4641 TargetTransformInfo::OperandValueKind Op2VK =
4642 TargetTransformInfo::OK_AnyValue;
4644 if (isa<ConstantInt>(I->getOperand(1)))
4645 Op2VK = TargetTransformInfo::OK_UniformConstantValue;
4647 return TTI.getArithmeticInstrCost(I->getOpcode(), VectorTy, Op1VK, Op2VK);
4649 case Instruction::Select: {
4650 SelectInst *SI = cast<SelectInst>(I);
4651 const SCEV *CondSCEV = SE->getSCEV(SI->getCondition());
4652 bool ScalarCond = (SE->isLoopInvariant(CondSCEV, TheLoop));
4653 Type *CondTy = SI->getCondition()->getType();
4655 CondTy = VectorType::get(CondTy, VF);
4657 return TTI.getCmpSelInstrCost(I->getOpcode(), VectorTy, CondTy);
4659 case Instruction::ICmp:
4660 case Instruction::FCmp: {
4661 Type *ValTy = I->getOperand(0)->getType();
4662 VectorTy = ToVectorTy(ValTy, VF);
4663 return TTI.getCmpSelInstrCost(I->getOpcode(), VectorTy);
4665 case Instruction::Store:
4666 case Instruction::Load: {
4667 StoreInst *SI = dyn_cast<StoreInst>(I);
4668 LoadInst *LI = dyn_cast<LoadInst>(I);
4669 Type *ValTy = (SI ? SI->getValueOperand()->getType() :
4671 VectorTy = ToVectorTy(ValTy, VF);
4673 unsigned Alignment = SI ? SI->getAlignment() : LI->getAlignment();
4674 unsigned AS = SI ? SI->getPointerAddressSpace() :
4675 LI->getPointerAddressSpace();
4676 Value *Ptr = SI ? SI->getPointerOperand() : LI->getPointerOperand();
4677 // We add the cost of address computation here instead of with the gep
4678 // instruction because only here we know whether the operation is
4681 return TTI.getAddressComputationCost(VectorTy) +
4682 TTI.getMemoryOpCost(I->getOpcode(), VectorTy, Alignment, AS);
4684 // Scalarized loads/stores.
4685 int ConsecutiveStride = Legal->isConsecutivePtr(Ptr);
4686 bool Reverse = ConsecutiveStride < 0;
4687 unsigned ScalarAllocatedSize = DL->getTypeAllocSize(ValTy);
4688 unsigned VectorElementSize = DL->getTypeStoreSize(VectorTy)/VF;
4689 if (!ConsecutiveStride || ScalarAllocatedSize != VectorElementSize) {
4690 bool IsComplexComputation =
4691 isLikelyComplexAddressComputation(Ptr, Legal, SE, TheLoop);
4693 // The cost of extracting from the value vector and pointer vector.
4694 Type *PtrTy = ToVectorTy(Ptr->getType(), VF);
4695 for (unsigned i = 0; i < VF; ++i) {
4696 // The cost of extracting the pointer operand.
4697 Cost += TTI.getVectorInstrCost(Instruction::ExtractElement, PtrTy, i);
4698 // In case of STORE, the cost of ExtractElement from the vector.
4699 // In case of LOAD, the cost of InsertElement into the returned
4701 Cost += TTI.getVectorInstrCost(SI ? Instruction::ExtractElement :
4702 Instruction::InsertElement,
4706 // The cost of the scalar loads/stores.
4707 Cost += VF * TTI.getAddressComputationCost(PtrTy, IsComplexComputation);
4708 Cost += VF * TTI.getMemoryOpCost(I->getOpcode(), ValTy->getScalarType(),
4713 // Wide load/stores.
4714 unsigned Cost = TTI.getAddressComputationCost(VectorTy);
4715 Cost += TTI.getMemoryOpCost(I->getOpcode(), VectorTy, Alignment, AS);
4718 Cost += TTI.getShuffleCost(TargetTransformInfo::SK_Reverse,
4722 case Instruction::ZExt:
4723 case Instruction::SExt:
4724 case Instruction::FPToUI:
4725 case Instruction::FPToSI:
4726 case Instruction::FPExt:
4727 case Instruction::PtrToInt:
4728 case Instruction::IntToPtr:
4729 case Instruction::SIToFP:
4730 case Instruction::UIToFP:
4731 case Instruction::Trunc:
4732 case Instruction::FPTrunc:
4733 case Instruction::BitCast: {
4734 // We optimize the truncation of induction variable.
4735 // The cost of these is the same as the scalar operation.
4736 if (I->getOpcode() == Instruction::Trunc &&
4737 Legal->isInductionVariable(I->getOperand(0)))
4738 return TTI.getCastInstrCost(I->getOpcode(), I->getType(),
4739 I->getOperand(0)->getType());
4741 Type *SrcVecTy = ToVectorTy(I->getOperand(0)->getType(), VF);
4742 return TTI.getCastInstrCost(I->getOpcode(), VectorTy, SrcVecTy);
4744 case Instruction::Call: {
4745 CallInst *CI = cast<CallInst>(I);
4746 Intrinsic::ID ID = getIntrinsicIDForCall(CI, TLI);
4747 assert(ID && "Not an intrinsic call!");
4748 Type *RetTy = ToVectorTy(CI->getType(), VF);
4749 SmallVector<Type*, 4> Tys;
4750 for (unsigned i = 0, ie = CI->getNumArgOperands(); i != ie; ++i)
4751 Tys.push_back(ToVectorTy(CI->getArgOperand(i)->getType(), VF));
4752 return TTI.getIntrinsicInstrCost(ID, RetTy, Tys);
4755 // We are scalarizing the instruction. Return the cost of the scalar
4756 // instruction, plus the cost of insert and extract into vector
4757 // elements, times the vector width.
4760 if (!RetTy->isVoidTy() && VF != 1) {
4761 unsigned InsCost = TTI.getVectorInstrCost(Instruction::InsertElement,
4763 unsigned ExtCost = TTI.getVectorInstrCost(Instruction::ExtractElement,
4766 // The cost of inserting the results plus extracting each one of the
4768 Cost += VF * (InsCost + ExtCost * I->getNumOperands());
4771 // The cost of executing VF copies of the scalar instruction. This opcode
4772 // is unknown. Assume that it is the same as 'mul'.
4773 Cost += VF * TTI.getArithmeticInstrCost(Instruction::Mul, VectorTy);
4779 Type* LoopVectorizationCostModel::ToVectorTy(Type *Scalar, unsigned VF) {
4780 if (Scalar->isVoidTy() || VF == 1)
4782 return VectorType::get(Scalar, VF);
4785 char LoopVectorize::ID = 0;
4786 static const char lv_name[] = "Loop Vectorization";
4787 INITIALIZE_PASS_BEGIN(LoopVectorize, LV_NAME, lv_name, false, false)
4788 INITIALIZE_AG_DEPENDENCY(TargetTransformInfo)
4789 INITIALIZE_PASS_DEPENDENCY(ScalarEvolution)
4790 INITIALIZE_PASS_DEPENDENCY(LoopSimplify)
4791 INITIALIZE_PASS_END(LoopVectorize, LV_NAME, lv_name, false, false)
4794 Pass *createLoopVectorizePass(bool NoUnrolling) {
4795 return new LoopVectorize(NoUnrolling);
4799 bool LoopVectorizationCostModel::isConsecutiveLoadOrStore(Instruction *Inst) {
4800 // Check for a store.
4801 if (StoreInst *ST = dyn_cast<StoreInst>(Inst))
4802 return Legal->isConsecutivePtr(ST->getPointerOperand()) != 0;
4804 // Check for a load.
4805 if (LoadInst *LI = dyn_cast<LoadInst>(Inst))
4806 return Legal->isConsecutivePtr(LI->getPointerOperand()) != 0;
4812 void InnerLoopUnroller::scalarizeInstruction(Instruction *Instr) {
4813 assert(!Instr->getType()->isAggregateType() && "Can't handle vectors");
4814 // Holds vector parameters or scalars, in case of uniform vals.
4815 SmallVector<VectorParts, 4> Params;
4817 setDebugLocFromInst(Builder, Instr);
4819 // Find all of the vectorized parameters.
4820 for (unsigned op = 0, e = Instr->getNumOperands(); op != e; ++op) {
4821 Value *SrcOp = Instr->getOperand(op);
4823 // If we are accessing the old induction variable, use the new one.
4824 if (SrcOp == OldInduction) {
4825 Params.push_back(getVectorValue(SrcOp));
4829 // Try using previously calculated values.
4830 Instruction *SrcInst = dyn_cast<Instruction>(SrcOp);
4832 // If the src is an instruction that appeared earlier in the basic block
4833 // then it should already be vectorized.
4834 if (SrcInst && OrigLoop->contains(SrcInst)) {
4835 assert(WidenMap.has(SrcInst) && "Source operand is unavailable");
4836 // The parameter is a vector value from earlier.
4837 Params.push_back(WidenMap.get(SrcInst));
4839 // The parameter is a scalar from outside the loop. Maybe even a constant.
4840 VectorParts Scalars;
4841 Scalars.append(UF, SrcOp);
4842 Params.push_back(Scalars);
4846 assert(Params.size() == Instr->getNumOperands() &&
4847 "Invalid number of operands");
4849 // Does this instruction return a value ?
4850 bool IsVoidRetTy = Instr->getType()->isVoidTy();
4852 Value *UndefVec = IsVoidRetTy ? 0 :
4853 UndefValue::get(Instr->getType());
4854 // Create a new entry in the WidenMap and initialize it to Undef or Null.
4855 VectorParts &VecResults = WidenMap.splat(Instr, UndefVec);
4857 // For each vector unroll 'part':
4858 for (unsigned Part = 0; Part < UF; ++Part) {
4859 // For each scalar that we create:
4861 Instruction *Cloned = Instr->clone();
4863 Cloned->setName(Instr->getName() + ".cloned");
4864 // Replace the operands of the cloned instrucions with extracted scalars.
4865 for (unsigned op = 0, e = Instr->getNumOperands(); op != e; ++op) {
4866 Value *Op = Params[op][Part];
4867 Cloned->setOperand(op, Op);
4870 // Place the cloned scalar in the new loop.
4871 Builder.Insert(Cloned);
4873 // If the original scalar returns a value we need to place it in a vector
4874 // so that future users will be able to use it.
4876 VecResults[Part] = Cloned;
4881 InnerLoopUnroller::vectorizeMemoryInstruction(Instruction *Instr,
4882 LoopVectorizationLegality*) {
4883 return scalarizeInstruction(Instr);
4886 Value *InnerLoopUnroller::reverseVector(Value *Vec) {
4890 Value *InnerLoopUnroller::getBroadcastInstrs(Value *V) {
4894 Value *InnerLoopUnroller::getConsecutiveVector(Value* Val, int StartIdx,
4896 // When unrolling and the VF is 1, we only need to add a simple scalar.
4897 Type *ITy = Val->getType();
4898 assert(!ITy->isVectorTy() && "Val must be a scalar");
4899 Constant *C = ConstantInt::get(ITy, StartIdx, Negate);
4900 return Builder.CreateAdd(Val, C, "induction");