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. Legalization of the IR is done
12 // in the codegen. However, the vectorizer uses (will use) the codegen
13 // interfaces to generate IR that is likely to result in an optimal binary.
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/MapVector.h"
51 #include "llvm/ADT/SmallPtrSet.h"
52 #include "llvm/ADT/SmallSet.h"
53 #include "llvm/ADT/SmallVector.h"
54 #include "llvm/ADT/StringExtras.h"
55 #include "llvm/Analysis/AliasAnalysis.h"
56 #include "llvm/Analysis/AliasSetTracker.h"
57 #include "llvm/Analysis/Dominators.h"
58 #include "llvm/Analysis/LoopInfo.h"
59 #include "llvm/Analysis/LoopIterator.h"
60 #include "llvm/Analysis/LoopPass.h"
61 #include "llvm/Analysis/ScalarEvolution.h"
62 #include "llvm/Analysis/ScalarEvolutionExpander.h"
63 #include "llvm/Analysis/ScalarEvolutionExpressions.h"
64 #include "llvm/Analysis/TargetTransformInfo.h"
65 #include "llvm/Analysis/ValueTracking.h"
66 #include "llvm/Analysis/Verifier.h"
67 #include "llvm/IR/Constants.h"
68 #include "llvm/IR/DataLayout.h"
69 #include "llvm/IR/DerivedTypes.h"
70 #include "llvm/IR/Function.h"
71 #include "llvm/IR/IRBuilder.h"
72 #include "llvm/IR/Instructions.h"
73 #include "llvm/IR/IntrinsicInst.h"
74 #include "llvm/IR/LLVMContext.h"
75 #include "llvm/IR/Module.h"
76 #include "llvm/IR/Type.h"
77 #include "llvm/IR/Value.h"
78 #include "llvm/Pass.h"
79 #include "llvm/Support/CommandLine.h"
80 #include "llvm/Support/Debug.h"
81 #include "llvm/Support/PatternMatch.h"
82 #include "llvm/Support/raw_ostream.h"
83 #include "llvm/Target/TargetLibraryInfo.h"
84 #include "llvm/Transforms/Scalar.h"
85 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
86 #include "llvm/Transforms/Utils/Local.h"
91 using namespace llvm::PatternMatch;
93 static cl::opt<unsigned>
94 VectorizationFactor("force-vector-width", cl::init(0), cl::Hidden,
95 cl::desc("Sets the SIMD width. Zero is autoselect."));
97 static cl::opt<unsigned>
98 VectorizationUnroll("force-vector-unroll", cl::init(0), cl::Hidden,
99 cl::desc("Sets the vectorization unroll count. "
100 "Zero is autoselect."));
103 EnableIfConversion("enable-if-conversion", cl::init(true), cl::Hidden,
104 cl::desc("Enable if-conversion during vectorization."));
106 /// We don't vectorize loops with a known constant trip count below this number.
107 static cl::opt<unsigned>
108 TinyTripCountVectorThreshold("vectorizer-min-trip-count", cl::init(16),
110 cl::desc("Don't vectorize loops with a constant "
111 "trip count that is smaller than this "
114 /// We don't unroll loops with a known constant trip count below this number.
115 static const unsigned TinyTripCountUnrollThreshold = 128;
117 /// When performing memory disambiguation checks at runtime do not make more
118 /// than this number of comparisons.
119 static const unsigned RuntimeMemoryCheckThreshold = 8;
121 /// We use a metadata with this name to indicate that a scalar loop was
122 /// vectorized and that we don't need to re-vectorize it if we run into it
125 AlreadyVectorizedMDName = "llvm.vectorizer.already_vectorized";
129 // Forward declarations.
130 class LoopVectorizationLegality;
131 class LoopVectorizationCostModel;
133 /// InnerLoopVectorizer vectorizes loops which contain only one basic
134 /// block to a specified vectorization factor (VF).
135 /// This class performs the widening of scalars into vectors, or multiple
136 /// scalars. This class also implements the following features:
137 /// * It inserts an epilogue loop for handling loops that don't have iteration
138 /// counts that are known to be a multiple of the vectorization factor.
139 /// * It handles the code generation for reduction variables.
140 /// * Scalarization (implementation using scalars) of un-vectorizable
142 /// InnerLoopVectorizer does not perform any vectorization-legality
143 /// checks, and relies on the caller to check for the different legality
144 /// aspects. The InnerLoopVectorizer relies on the
145 /// LoopVectorizationLegality class to provide information about the induction
146 /// and reduction variables that were found to a given vectorization factor.
147 class InnerLoopVectorizer {
149 InnerLoopVectorizer(Loop *OrigLoop, ScalarEvolution *SE, LoopInfo *LI,
150 DominatorTree *DT, DataLayout *DL,
151 const TargetLibraryInfo *TLI, unsigned VecWidth,
152 unsigned UnrollFactor)
153 : OrigLoop(OrigLoop), SE(SE), LI(LI), DT(DT), DL(DL), TLI(TLI),
154 VF(VecWidth), UF(UnrollFactor), Builder(SE->getContext()), Induction(0),
155 OldInduction(0), WidenMap(UnrollFactor) {}
157 // Perform the actual loop widening (vectorization).
158 void vectorize(LoopVectorizationLegality *Legal) {
159 // Create a new empty loop. Unlink the old loop and connect the new one.
160 createEmptyLoop(Legal);
161 // Widen each instruction in the old loop to a new one in the new loop.
162 // Use the Legality module to find the induction and reduction variables.
163 vectorizeLoop(Legal);
164 // Register the new loop and update the analysis passes.
169 /// A small list of PHINodes.
170 typedef SmallVector<PHINode*, 4> PhiVector;
171 /// When we unroll loops we have multiple vector values for each scalar.
172 /// This data structure holds the unrolled and vectorized values that
173 /// originated from one scalar instruction.
174 typedef SmallVector<Value*, 2> VectorParts;
176 /// Add code that checks at runtime if the accessed arrays overlap.
177 /// Returns the comparator value or NULL if no check is needed.
178 Instruction *addRuntimeCheck(LoopVectorizationLegality *Legal,
180 /// Create an empty loop, based on the loop ranges of the old loop.
181 void createEmptyLoop(LoopVectorizationLegality *Legal);
182 /// Copy and widen the instructions from the old loop.
183 void vectorizeLoop(LoopVectorizationLegality *Legal);
185 /// A helper function that computes the predicate of the block BB, assuming
186 /// that the header block of the loop is set to True. It returns the *entry*
187 /// mask for the block BB.
188 VectorParts createBlockInMask(BasicBlock *BB);
189 /// A helper function that computes the predicate of the edge between SRC
191 VectorParts createEdgeMask(BasicBlock *Src, BasicBlock *Dst);
193 /// A helper function to vectorize a single BB within the innermost loop.
194 void vectorizeBlockInLoop(LoopVectorizationLegality *Legal, BasicBlock *BB,
197 /// Insert the new loop to the loop hierarchy and pass manager
198 /// and update the analysis passes.
199 void updateAnalysis();
201 /// This instruction is un-vectorizable. Implement it as a sequence
203 void scalarizeInstruction(Instruction *Instr);
205 /// Vectorize Load and Store instructions,
206 void vectorizeMemoryInstruction(Instruction *Instr,
207 LoopVectorizationLegality *Legal);
209 /// Create a broadcast instruction. This method generates a broadcast
210 /// instruction (shuffle) for loop invariant values and for the induction
211 /// value. If this is the induction variable then we extend it to N, N+1, ...
212 /// this is needed because each iteration in the loop corresponds to a SIMD
214 Value *getBroadcastInstrs(Value *V);
216 /// This function adds 0, 1, 2 ... to each vector element, starting at zero.
217 /// If Negate is set then negative numbers are added e.g. (0, -1, -2, ...).
218 /// The sequence starts at StartIndex.
219 Value *getConsecutiveVector(Value* Val, unsigned StartIdx, bool Negate);
221 /// When we go over instructions in the basic block we rely on previous
222 /// values within the current basic block or on loop invariant values.
223 /// When we widen (vectorize) values we place them in the map. If the values
224 /// are not within the map, they have to be loop invariant, so we simply
225 /// broadcast them into a vector.
226 VectorParts &getVectorValue(Value *V);
228 /// Generate a shuffle sequence that will reverse the vector Vec.
229 Value *reverseVector(Value *Vec);
231 /// This is a helper class that holds the vectorizer state. It maps scalar
232 /// instructions to vector instructions. When the code is 'unrolled' then
233 /// then a single scalar value is mapped to multiple vector parts. The parts
234 /// are stored in the VectorPart type.
236 /// C'tor. UnrollFactor controls the number of vectors ('parts') that
238 ValueMap(unsigned UnrollFactor) : UF(UnrollFactor) {}
240 /// \return True if 'Key' is saved in the Value Map.
241 bool has(Value *Key) const { return MapStorage.count(Key); }
243 /// Initializes a new entry in the map. Sets all of the vector parts to the
244 /// save value in 'Val'.
245 /// \return A reference to a vector with splat values.
246 VectorParts &splat(Value *Key, Value *Val) {
247 VectorParts &Entry = MapStorage[Key];
248 Entry.assign(UF, Val);
252 ///\return A reference to the value that is stored at 'Key'.
253 VectorParts &get(Value *Key) {
254 VectorParts &Entry = MapStorage[Key];
257 assert(Entry.size() == UF);
262 /// The unroll factor. Each entry in the map stores this number of vector
266 /// Map storage. We use std::map and not DenseMap because insertions to a
267 /// dense map invalidates its iterators.
268 std::map<Value *, VectorParts> MapStorage;
271 /// The original loop.
273 /// Scev analysis to use.
281 /// Target Library Info.
282 const TargetLibraryInfo *TLI;
284 /// The vectorization SIMD factor to use. Each vector will have this many
287 /// The vectorization unroll factor to use. Each scalar is vectorized to this
288 /// many different vector instructions.
291 /// The builder that we use
294 // --- Vectorization state ---
296 /// The vector-loop preheader.
297 BasicBlock *LoopVectorPreHeader;
298 /// The scalar-loop preheader.
299 BasicBlock *LoopScalarPreHeader;
300 /// Middle Block between the vector and the scalar.
301 BasicBlock *LoopMiddleBlock;
302 ///The ExitBlock of the scalar loop.
303 BasicBlock *LoopExitBlock;
304 ///The vector loop body.
305 BasicBlock *LoopVectorBody;
306 ///The scalar loop body.
307 BasicBlock *LoopScalarBody;
308 /// A list of all bypass blocks. The first block is the entry of the loop.
309 SmallVector<BasicBlock *, 4> LoopBypassBlocks;
311 /// The new Induction variable which was added to the new block.
313 /// The induction variable of the old basic block.
314 PHINode *OldInduction;
315 /// Maps scalars to widened vectors.
319 /// LoopVectorizationLegality checks if it is legal to vectorize a loop, and
320 /// to what vectorization factor.
321 /// This class does not look at the profitability of vectorization, only the
322 /// legality. This class has two main kinds of checks:
323 /// * Memory checks - The code in canVectorizeMemory checks if vectorization
324 /// will change the order of memory accesses in a way that will change the
325 /// correctness of the program.
326 /// * Scalars checks - The code in canVectorizeInstrs and canVectorizeMemory
327 /// checks for a number of different conditions, such as the availability of a
328 /// single induction variable, that all types are supported and vectorize-able,
329 /// etc. This code reflects the capabilities of InnerLoopVectorizer.
330 /// This class is also used by InnerLoopVectorizer for identifying
331 /// induction variable and the different reduction variables.
332 class LoopVectorizationLegality {
334 LoopVectorizationLegality(Loop *L, ScalarEvolution *SE, DataLayout *DL,
335 DominatorTree *DT, TargetTransformInfo* TTI,
336 AliasAnalysis *AA, TargetLibraryInfo *TLI)
337 : TheLoop(L), SE(SE), DL(DL), DT(DT), TTI(TTI), AA(AA), TLI(TLI),
340 /// This enum represents the kinds of reductions that we support.
342 RK_NoReduction, ///< Not a reduction.
343 RK_IntegerAdd, ///< Sum of integers.
344 RK_IntegerMult, ///< Product of integers.
345 RK_IntegerOr, ///< Bitwise or logical OR of numbers.
346 RK_IntegerAnd, ///< Bitwise or logical AND of numbers.
347 RK_IntegerXor, ///< Bitwise or logical XOR of numbers.
348 RK_IntegerMinMax, ///< Min/max implemented in terms of select(cmp()).
349 RK_FloatAdd, ///< Sum of floats.
350 RK_FloatMult ///< Product of floats.
353 /// This enum represents the kinds of inductions that we support.
355 IK_NoInduction, ///< Not an induction variable.
356 IK_IntInduction, ///< Integer induction variable. Step = 1.
357 IK_ReverseIntInduction, ///< Reverse int induction variable. Step = -1.
358 IK_PtrInduction, ///< Pointer induction var. Step = sizeof(elem).
359 IK_ReversePtrInduction ///< Reverse ptr indvar. Step = - sizeof(elem).
362 // This enum represents the kind of minmax reduction.
363 enum MinMaxReductionKind {
371 /// This POD struct holds information about reduction variables.
372 struct ReductionDescriptor {
373 ReductionDescriptor() : StartValue(0), LoopExitInstr(0),
374 Kind(RK_NoReduction), MinMaxKind(MRK_Invalid) {}
376 ReductionDescriptor(Value *Start, Instruction *Exit, ReductionKind K,
377 MinMaxReductionKind MK)
378 : StartValue(Start), LoopExitInstr(Exit), Kind(K), MinMaxKind(MK) {}
380 // The starting value of the reduction.
381 // It does not have to be zero!
383 // The instruction who's value is used outside the loop.
384 Instruction *LoopExitInstr;
385 // The kind of the reduction.
387 // If this a min/max reduction the kind of reduction.
388 MinMaxReductionKind MinMaxKind;
391 /// This POD struct holds information about a potential reduction operation.
392 struct ReductionInstDesc {
393 ReductionInstDesc(bool IsRedux, Instruction *I) :
394 IsReduction(IsRedux), PatternLastInst(I), MinMaxKind(MRK_Invalid) {}
396 ReductionInstDesc(Instruction *I, MinMaxReductionKind K) :
397 IsReduction(true), PatternLastInst(I), MinMaxKind(K) {}
399 // Is this instruction a reduction candidate.
401 // The last instruction in a min/max pattern (select of the select(icmp())
402 // pattern), or the current reduction instruction otherwise.
403 Instruction *PatternLastInst;
404 // If this is a min/max pattern the comparison predicate.
405 MinMaxReductionKind MinMaxKind;
408 // This POD struct holds information about the memory runtime legality
409 // check that a group of pointers do not overlap.
410 struct RuntimePointerCheck {
411 RuntimePointerCheck() : Need(false) {}
413 /// Reset the state of the pointer runtime information.
421 /// Insert a pointer and calculate the start and end SCEVs.
422 void insert(ScalarEvolution *SE, Loop *Lp, Value *Ptr, bool WritePtr);
424 /// This flag indicates if we need to add the runtime check.
426 /// Holds the pointers that we need to check.
427 SmallVector<Value*, 2> Pointers;
428 /// Holds the pointer value at the beginning of the loop.
429 SmallVector<const SCEV*, 2> Starts;
430 /// Holds the pointer value at the end of the loop.
431 SmallVector<const SCEV*, 2> Ends;
432 /// Holds the information if this pointer is used for writing to memory.
433 SmallVector<bool, 2> IsWritePtr;
436 /// A POD for saving information about induction variables.
437 struct InductionInfo {
438 InductionInfo(Value *Start, InductionKind K) : StartValue(Start), IK(K) {}
439 InductionInfo() : StartValue(0), IK(IK_NoInduction) {}
446 /// ReductionList contains the reduction descriptors for all
447 /// of the reductions that were found in the loop.
448 typedef DenseMap<PHINode*, ReductionDescriptor> ReductionList;
450 /// InductionList saves induction variables and maps them to the
451 /// induction descriptor.
452 typedef MapVector<PHINode*, InductionInfo> InductionList;
454 /// Alias(Multi)Map stores the values (GEPs or underlying objects and their
455 /// respective Store/Load instruction(s) to calculate aliasing.
456 typedef MapVector<Value*, Instruction* > AliasMap;
457 typedef DenseMap<Value*, std::vector<Instruction*> > AliasMultiMap;
459 /// Returns true if it is legal to vectorize this loop.
460 /// This does not mean that it is profitable to vectorize this
461 /// loop, only that it is legal to do so.
464 /// Returns the Induction variable.
465 PHINode *getInduction() { return Induction; }
467 /// Returns the reduction variables found in the loop.
468 ReductionList *getReductionVars() { return &Reductions; }
470 /// Returns the induction variables found in the loop.
471 InductionList *getInductionVars() { return &Inductions; }
473 /// Returns True if V is an induction variable in this loop.
474 bool isInductionVariable(const Value *V);
476 /// Return true if the block BB needs to be predicated in order for the loop
477 /// to be vectorized.
478 bool blockNeedsPredication(BasicBlock *BB);
480 /// Check if this pointer is consecutive when vectorizing. This happens
481 /// when the last index of the GEP is the induction variable, or that the
482 /// pointer itself is an induction variable.
483 /// This check allows us to vectorize A[idx] into a wide load/store.
485 /// 0 - Stride is unknown or non consecutive.
486 /// 1 - Address is consecutive.
487 /// -1 - Address is consecutive, and decreasing.
488 int isConsecutivePtr(Value *Ptr);
490 /// Returns true if the value V is uniform within the loop.
491 bool isUniform(Value *V);
493 /// Returns true if this instruction will remain scalar after vectorization.
494 bool isUniformAfterVectorization(Instruction* I) { return Uniforms.count(I); }
496 /// Returns the information that we collected about runtime memory check.
497 RuntimePointerCheck *getRuntimePointerCheck() { return &PtrRtCheck; }
499 /// This function returns the identity element (or neutral element) for
501 static Constant *getReductionIdentity(ReductionKind K, Type *Tp,
502 MinMaxReductionKind MinMaxK);
504 /// Check if a single basic block loop is vectorizable.
505 /// At this point we know that this is a loop with a constant trip count
506 /// and we only need to check individual instructions.
507 bool canVectorizeInstrs();
509 /// When we vectorize loops we may change the order in which
510 /// we read and write from memory. This method checks if it is
511 /// legal to vectorize the code, considering only memory constrains.
512 /// Returns true if the loop is vectorizable
513 bool canVectorizeMemory();
515 /// Return true if we can vectorize this loop using the IF-conversion
517 bool canVectorizeWithIfConvert();
519 /// Collect the variables that need to stay uniform after vectorization.
520 void collectLoopUniforms();
522 /// Return true if all of the instructions in the block can be speculatively
524 bool blockCanBePredicated(BasicBlock *BB);
526 /// Returns True, if 'Phi' is the kind of reduction variable for type
527 /// 'Kind'. If this is a reduction variable, it adds it to ReductionList.
528 bool AddReductionVar(PHINode *Phi, ReductionKind Kind);
529 /// Returns a struct describing if the instruction 'I' can be a reduction
530 /// variable of type 'Kind'. If the reduction is a min/max pattern of
531 /// select(icmp()) this function advances the instruction pointer 'I' from the
532 /// compare instruction to the select instruction and stores this pointer in
533 /// 'PatternLastInst' member of the returned struct.
534 ReductionInstDesc isReductionInstr(Instruction *I, ReductionKind Kind,
535 ReductionInstDesc &Desc);
536 /// Returns true if the instruction is a Select(ICmp(X, Y), X, Y) instruction
537 /// pattern corresponding to a min(X, Y) or max(X, Y).
538 static ReductionInstDesc isMinMaxSelectCmpPattern(Instruction *I,
539 ReductionInstDesc &Prev);
540 /// Returns the induction kind of Phi. This function may return NoInduction
541 /// if the PHI is not an induction variable.
542 InductionKind isInductionVariable(PHINode *Phi);
543 /// Return true if can compute the address bounds of Ptr within the loop.
544 bool hasComputableBounds(Value *Ptr);
545 /// Return true if there is the chance of write reorder.
546 bool hasPossibleGlobalWriteReorder(Value *Object,
548 AliasMultiMap &WriteObjects,
549 unsigned MaxByteWidth);
550 /// Return the AA location for a load or a store.
551 AliasAnalysis::Location getLoadStoreLocation(Instruction *Inst);
554 /// The loop that we evaluate.
558 /// DataLayout analysis.
563 TargetTransformInfo *TTI;
566 /// Target Library Info.
567 TargetLibraryInfo *TLI;
569 // --- vectorization state --- //
571 /// Holds the integer induction variable. This is the counter of the
574 /// Holds the reduction variables.
575 ReductionList Reductions;
576 /// Holds all of the induction variables that we found in the loop.
577 /// Notice that inductions don't need to start at zero and that induction
578 /// variables can be pointers.
579 InductionList Inductions;
581 /// Allowed outside users. This holds the reduction
582 /// vars which can be accessed from outside the loop.
583 SmallPtrSet<Value*, 4> AllowedExit;
584 /// This set holds the variables which are known to be uniform after
586 SmallPtrSet<Instruction*, 4> Uniforms;
587 /// We need to check that all of the pointers in this list are disjoint
589 RuntimePointerCheck PtrRtCheck;
592 /// LoopVectorizationCostModel - estimates the expected speedups due to
594 /// In many cases vectorization is not profitable. This can happen because of
595 /// a number of reasons. In this class we mainly attempt to predict the
596 /// expected speedup/slowdowns due to the supported instruction set. We use the
597 /// TargetTransformInfo to query the different backends for the cost of
598 /// different operations.
599 class LoopVectorizationCostModel {
601 LoopVectorizationCostModel(Loop *L, ScalarEvolution *SE, LoopInfo *LI,
602 LoopVectorizationLegality *Legal,
603 const TargetTransformInfo &TTI,
604 DataLayout *DL, const TargetLibraryInfo *TLI)
605 : TheLoop(L), SE(SE), LI(LI), Legal(Legal), TTI(TTI), DL(DL), TLI(TLI) {}
607 /// Information about vectorization costs
608 struct VectorizationFactor {
609 unsigned Width; // Vector width with best cost
610 unsigned Cost; // Cost of the loop with that width
612 /// \return The most profitable vectorization factor and the cost of that VF.
613 /// This method checks every power of two up to VF. If UserVF is not ZERO
614 /// then this vectorization factor will be selected if vectorization is
616 VectorizationFactor selectVectorizationFactor(bool OptForSize,
619 /// \return The size (in bits) of the widest type in the code that
620 /// needs to be vectorized. We ignore values that remain scalar such as
621 /// 64 bit loop indices.
622 unsigned getWidestType();
624 /// \return The most profitable unroll factor.
625 /// If UserUF is non-zero then this method finds the best unroll-factor
626 /// based on register pressure and other parameters.
627 /// VF and LoopCost are the selected vectorization factor and the cost of the
629 unsigned selectUnrollFactor(bool OptForSize, unsigned UserUF, unsigned VF,
632 /// \brief A struct that represents some properties of the register usage
634 struct RegisterUsage {
635 /// Holds the number of loop invariant values that are used in the loop.
636 unsigned LoopInvariantRegs;
637 /// Holds the maximum number of concurrent live intervals in the loop.
638 unsigned MaxLocalUsers;
639 /// Holds the number of instructions in the loop.
640 unsigned NumInstructions;
643 /// \return information about the register usage of the loop.
644 RegisterUsage calculateRegisterUsage();
647 /// Returns the expected execution cost. The unit of the cost does
648 /// not matter because we use the 'cost' units to compare different
649 /// vector widths. The cost that is returned is *not* normalized by
650 /// the factor width.
651 unsigned expectedCost(unsigned VF);
653 /// Returns the execution time cost of an instruction for a given vector
654 /// width. Vector width of one means scalar.
655 unsigned getInstructionCost(Instruction *I, unsigned VF);
657 /// A helper function for converting Scalar types to vector types.
658 /// If the incoming type is void, we return void. If the VF is 1, we return
660 static Type* ToVectorTy(Type *Scalar, unsigned VF);
662 /// Returns whether the instruction is a load or store and will be a emitted
663 /// as a vector operation.
664 bool isConsecutiveLoadOrStore(Instruction *I);
666 /// The loop that we evaluate.
670 /// Loop Info analysis.
672 /// Vectorization legality.
673 LoopVectorizationLegality *Legal;
674 /// Vector target information.
675 const TargetTransformInfo &TTI;
676 /// Target data layout information.
678 /// Target Library Info.
679 const TargetLibraryInfo *TLI;
682 /// The LoopVectorize Pass.
683 struct LoopVectorize : public LoopPass {
684 /// Pass identification, replacement for typeid
687 explicit LoopVectorize() : LoopPass(ID) {
688 initializeLoopVectorizePass(*PassRegistry::getPassRegistry());
694 TargetTransformInfo *TTI;
697 TargetLibraryInfo *TLI;
699 virtual bool runOnLoop(Loop *L, LPPassManager &LPM) {
700 // We only vectorize innermost loops.
704 SE = &getAnalysis<ScalarEvolution>();
705 DL = getAnalysisIfAvailable<DataLayout>();
706 LI = &getAnalysis<LoopInfo>();
707 TTI = &getAnalysis<TargetTransformInfo>();
708 DT = &getAnalysis<DominatorTree>();
709 AA = getAnalysisIfAvailable<AliasAnalysis>();
710 TLI = getAnalysisIfAvailable<TargetLibraryInfo>();
713 DEBUG(dbgs() << "LV: Not vectorizing because of missing data layout");
717 DEBUG(dbgs() << "LV: Checking a loop in \"" <<
718 L->getHeader()->getParent()->getName() << "\"\n");
720 // Check if it is legal to vectorize the loop.
721 LoopVectorizationLegality LVL(L, SE, DL, DT, TTI, AA, TLI);
722 if (!LVL.canVectorize()) {
723 DEBUG(dbgs() << "LV: Not vectorizing.\n");
727 // Use the cost model.
728 LoopVectorizationCostModel CM(L, SE, LI, &LVL, *TTI, DL, TLI);
730 // Check the function attributes to find out if this function should be
731 // optimized for size.
732 Function *F = L->getHeader()->getParent();
733 Attribute::AttrKind SzAttr = Attribute::OptimizeForSize;
734 Attribute::AttrKind FlAttr = Attribute::NoImplicitFloat;
735 unsigned FnIndex = AttributeSet::FunctionIndex;
736 bool OptForSize = F->getAttributes().hasAttribute(FnIndex, SzAttr);
737 bool NoFloat = F->getAttributes().hasAttribute(FnIndex, FlAttr);
740 DEBUG(dbgs() << "LV: Can't vectorize when the NoImplicitFloat"
741 "attribute is used.\n");
745 // Select the optimal vectorization factor.
746 LoopVectorizationCostModel::VectorizationFactor VF;
747 VF = CM.selectVectorizationFactor(OptForSize, VectorizationFactor);
748 // Select the unroll factor.
749 unsigned UF = CM.selectUnrollFactor(OptForSize, VectorizationUnroll,
753 DEBUG(dbgs() << "LV: Vectorization is possible but not beneficial.\n");
757 DEBUG(dbgs() << "LV: Found a vectorizable loop ("<< VF.Width << ") in "<<
758 F->getParent()->getModuleIdentifier()<<"\n");
759 DEBUG(dbgs() << "LV: Unroll Factor is " << UF << "\n");
761 // If we decided that it is *legal* to vectorize the loop then do it.
762 InnerLoopVectorizer LB(L, SE, LI, DT, DL, TLI, VF.Width, UF);
765 DEBUG(verifyFunction(*L->getHeader()->getParent()));
769 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
770 LoopPass::getAnalysisUsage(AU);
771 AU.addRequiredID(LoopSimplifyID);
772 AU.addRequiredID(LCSSAID);
773 AU.addRequired<DominatorTree>();
774 AU.addRequired<LoopInfo>();
775 AU.addRequired<ScalarEvolution>();
776 AU.addRequired<TargetTransformInfo>();
777 AU.addPreserved<LoopInfo>();
778 AU.addPreserved<DominatorTree>();
783 } // end anonymous namespace
785 //===----------------------------------------------------------------------===//
786 // Implementation of LoopVectorizationLegality, InnerLoopVectorizer and
787 // LoopVectorizationCostModel.
788 //===----------------------------------------------------------------------===//
791 LoopVectorizationLegality::RuntimePointerCheck::insert(ScalarEvolution *SE,
792 Loop *Lp, Value *Ptr,
794 const SCEV *Sc = SE->getSCEV(Ptr);
795 const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Sc);
796 assert(AR && "Invalid addrec expression");
797 const SCEV *Ex = SE->getExitCount(Lp, Lp->getLoopLatch());
798 const SCEV *ScEnd = AR->evaluateAtIteration(Ex, *SE);
799 Pointers.push_back(Ptr);
800 Starts.push_back(AR->getStart());
801 Ends.push_back(ScEnd);
802 IsWritePtr.push_back(WritePtr);
805 Value *InnerLoopVectorizer::getBroadcastInstrs(Value *V) {
806 // Save the current insertion location.
807 Instruction *Loc = Builder.GetInsertPoint();
809 // We need to place the broadcast of invariant variables outside the loop.
810 Instruction *Instr = dyn_cast<Instruction>(V);
811 bool NewInstr = (Instr && Instr->getParent() == LoopVectorBody);
812 bool Invariant = OrigLoop->isLoopInvariant(V) && !NewInstr;
814 // Place the code for broadcasting invariant variables in the new preheader.
816 Builder.SetInsertPoint(LoopVectorPreHeader->getTerminator());
818 // Broadcast the scalar into all locations in the vector.
819 Value *Shuf = Builder.CreateVectorSplat(VF, V, "broadcast");
821 // Restore the builder insertion point.
823 Builder.SetInsertPoint(Loc);
828 Value *InnerLoopVectorizer::getConsecutiveVector(Value* Val, unsigned StartIdx,
830 assert(Val->getType()->isVectorTy() && "Must be a vector");
831 assert(Val->getType()->getScalarType()->isIntegerTy() &&
832 "Elem must be an integer");
834 Type *ITy = Val->getType()->getScalarType();
835 VectorType *Ty = cast<VectorType>(Val->getType());
836 int VLen = Ty->getNumElements();
837 SmallVector<Constant*, 8> Indices;
839 // Create a vector of consecutive numbers from zero to VF.
840 for (int i = 0; i < VLen; ++i) {
841 int Idx = Negate ? (-i): i;
842 Indices.push_back(ConstantInt::get(ITy, StartIdx + Idx));
845 // Add the consecutive indices to the vector value.
846 Constant *Cv = ConstantVector::get(Indices);
847 assert(Cv->getType() == Val->getType() && "Invalid consecutive vec");
848 return Builder.CreateAdd(Val, Cv, "induction");
851 int LoopVectorizationLegality::isConsecutivePtr(Value *Ptr) {
852 assert(Ptr->getType()->isPointerTy() && "Unexpected non ptr");
853 // Make sure that the pointer does not point to structs.
854 if (cast<PointerType>(Ptr->getType())->getElementType()->isAggregateType())
857 // If this value is a pointer induction variable we know it is consecutive.
858 PHINode *Phi = dyn_cast_or_null<PHINode>(Ptr);
859 if (Phi && Inductions.count(Phi)) {
860 InductionInfo II = Inductions[Phi];
861 if (IK_PtrInduction == II.IK)
863 else if (IK_ReversePtrInduction == II.IK)
867 GetElementPtrInst *Gep = dyn_cast_or_null<GetElementPtrInst>(Ptr);
871 unsigned NumOperands = Gep->getNumOperands();
872 Value *LastIndex = Gep->getOperand(NumOperands - 1);
874 Value *GpPtr = Gep->getPointerOperand();
875 // If this GEP value is a consecutive pointer induction variable and all of
876 // the indices are constant then we know it is consecutive. We can
877 Phi = dyn_cast<PHINode>(GpPtr);
878 if (Phi && Inductions.count(Phi)) {
880 // Make sure that the pointer does not point to structs.
881 PointerType *GepPtrType = cast<PointerType>(GpPtr->getType());
882 if (GepPtrType->getElementType()->isAggregateType())
885 // Make sure that all of the index operands are loop invariant.
886 for (unsigned i = 1; i < NumOperands; ++i)
887 if (!SE->isLoopInvariant(SE->getSCEV(Gep->getOperand(i)), TheLoop))
890 InductionInfo II = Inductions[Phi];
891 if (IK_PtrInduction == II.IK)
893 else if (IK_ReversePtrInduction == II.IK)
897 // Check that all of the gep indices are uniform except for the last.
898 for (unsigned i = 0; i < NumOperands - 1; ++i)
899 if (!SE->isLoopInvariant(SE->getSCEV(Gep->getOperand(i)), TheLoop))
902 // We can emit wide load/stores only if the last index is the induction
904 const SCEV *Last = SE->getSCEV(LastIndex);
905 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Last)) {
906 const SCEV *Step = AR->getStepRecurrence(*SE);
908 // The memory is consecutive because the last index is consecutive
909 // and all other indices are loop invariant.
912 if (Step->isAllOnesValue())
919 bool LoopVectorizationLegality::isUniform(Value *V) {
920 return (SE->isLoopInvariant(SE->getSCEV(V), TheLoop));
923 InnerLoopVectorizer::VectorParts&
924 InnerLoopVectorizer::getVectorValue(Value *V) {
925 assert(V != Induction && "The new induction variable should not be used.");
926 assert(!V->getType()->isVectorTy() && "Can't widen a vector");
928 // If we have this scalar in the map, return it.
930 return WidenMap.get(V);
932 // If this scalar is unknown, assume that it is a constant or that it is
933 // loop invariant. Broadcast V and save the value for future uses.
934 Value *B = getBroadcastInstrs(V);
935 return WidenMap.splat(V, B);
938 Value *InnerLoopVectorizer::reverseVector(Value *Vec) {
939 assert(Vec->getType()->isVectorTy() && "Invalid type");
940 SmallVector<Constant*, 8> ShuffleMask;
941 for (unsigned i = 0; i < VF; ++i)
942 ShuffleMask.push_back(Builder.getInt32(VF - i - 1));
944 return Builder.CreateShuffleVector(Vec, UndefValue::get(Vec->getType()),
945 ConstantVector::get(ShuffleMask),
950 void InnerLoopVectorizer::vectorizeMemoryInstruction(Instruction *Instr,
951 LoopVectorizationLegality *Legal) {
952 // Attempt to issue a wide load.
953 LoadInst *LI = dyn_cast<LoadInst>(Instr);
954 StoreInst *SI = dyn_cast<StoreInst>(Instr);
956 assert((LI || SI) && "Invalid Load/Store instruction");
958 Type *ScalarDataTy = LI ? LI->getType() : SI->getValueOperand()->getType();
959 Type *DataTy = VectorType::get(ScalarDataTy, VF);
960 Value *Ptr = LI ? LI->getPointerOperand() : SI->getPointerOperand();
961 unsigned Alignment = LI ? LI->getAlignment() : SI->getAlignment();
963 unsigned ScalarAllocatedSize = DL->getTypeAllocSize(ScalarDataTy);
964 unsigned VectorElementSize = DL->getTypeStoreSize(DataTy)/VF;
966 if (ScalarAllocatedSize != VectorElementSize)
967 return scalarizeInstruction(Instr);
969 // If the pointer is loop invariant or if it is non consecutive,
970 // scalarize the load.
971 int ConsecutiveStride = Legal->isConsecutivePtr(Ptr);
972 bool Reverse = ConsecutiveStride < 0;
973 bool UniformLoad = LI && Legal->isUniform(Ptr);
974 if (!ConsecutiveStride || UniformLoad)
975 return scalarizeInstruction(Instr);
977 Constant *Zero = Builder.getInt32(0);
978 VectorParts &Entry = WidenMap.get(Instr);
980 // Handle consecutive loads/stores.
981 GetElementPtrInst *Gep = dyn_cast<GetElementPtrInst>(Ptr);
982 if (Gep && Legal->isInductionVariable(Gep->getPointerOperand())) {
983 Value *PtrOperand = Gep->getPointerOperand();
984 Value *FirstBasePtr = getVectorValue(PtrOperand)[0];
985 FirstBasePtr = Builder.CreateExtractElement(FirstBasePtr, Zero);
987 // Create the new GEP with the new induction variable.
988 GetElementPtrInst *Gep2 = cast<GetElementPtrInst>(Gep->clone());
989 Gep2->setOperand(0, FirstBasePtr);
990 Gep2->setName("gep.indvar.base");
991 Ptr = Builder.Insert(Gep2);
993 assert(SE->isLoopInvariant(SE->getSCEV(Gep->getPointerOperand()),
994 OrigLoop) && "Base ptr must be invariant");
996 // The last index does not have to be the induction. It can be
997 // consecutive and be a function of the index. For example A[I+1];
998 unsigned NumOperands = Gep->getNumOperands();
1000 Value *LastGepOperand = Gep->getOperand(NumOperands - 1);
1001 VectorParts &GEPParts = getVectorValue(LastGepOperand);
1002 Value *LastIndex = GEPParts[0];
1003 LastIndex = Builder.CreateExtractElement(LastIndex, Zero);
1005 // Create the new GEP with the new induction variable.
1006 GetElementPtrInst *Gep2 = cast<GetElementPtrInst>(Gep->clone());
1007 Gep2->setOperand(NumOperands - 1, LastIndex);
1008 Gep2->setName("gep.indvar.idx");
1009 Ptr = Builder.Insert(Gep2);
1011 // Use the induction element ptr.
1012 assert(isa<PHINode>(Ptr) && "Invalid induction ptr");
1013 VectorParts &PtrVal = getVectorValue(Ptr);
1014 Ptr = Builder.CreateExtractElement(PtrVal[0], Zero);
1019 assert(!Legal->isUniform(SI->getPointerOperand()) &&
1020 "We do not allow storing to uniform addresses");
1022 VectorParts &StoredVal = getVectorValue(SI->getValueOperand());
1023 for (unsigned Part = 0; Part < UF; ++Part) {
1024 // Calculate the pointer for the specific unroll-part.
1025 Value *PartPtr = Builder.CreateGEP(Ptr, Builder.getInt32(Part * VF));
1028 // If we store to reverse consecutive memory locations then we need
1029 // to reverse the order of elements in the stored value.
1030 StoredVal[Part] = reverseVector(StoredVal[Part]);
1031 // If the address is consecutive but reversed, then the
1032 // wide store needs to start at the last vector element.
1033 PartPtr = Builder.CreateGEP(Ptr, Builder.getInt32(-Part * VF));
1034 PartPtr = Builder.CreateGEP(PartPtr, Builder.getInt32(1 - VF));
1037 Value *VecPtr = Builder.CreateBitCast(PartPtr, DataTy->getPointerTo());
1038 Builder.CreateStore(StoredVal[Part], VecPtr)->setAlignment(Alignment);
1042 for (unsigned Part = 0; Part < UF; ++Part) {
1043 // Calculate the pointer for the specific unroll-part.
1044 Value *PartPtr = Builder.CreateGEP(Ptr, Builder.getInt32(Part * VF));
1047 // If the address is consecutive but reversed, then the
1048 // wide store needs to start at the last vector element.
1049 PartPtr = Builder.CreateGEP(Ptr, Builder.getInt32(-Part * VF));
1050 PartPtr = Builder.CreateGEP(PartPtr, Builder.getInt32(1 - VF));
1053 Value *VecPtr = Builder.CreateBitCast(PartPtr, DataTy->getPointerTo());
1054 Value *LI = Builder.CreateLoad(VecPtr, "wide.load");
1055 cast<LoadInst>(LI)->setAlignment(Alignment);
1056 Entry[Part] = Reverse ? reverseVector(LI) : LI;
1060 void InnerLoopVectorizer::scalarizeInstruction(Instruction *Instr) {
1061 assert(!Instr->getType()->isAggregateType() && "Can't handle vectors");
1062 // Holds vector parameters or scalars, in case of uniform vals.
1063 SmallVector<VectorParts, 4> Params;
1065 // Find all of the vectorized parameters.
1066 for (unsigned op = 0, e = Instr->getNumOperands(); op != e; ++op) {
1067 Value *SrcOp = Instr->getOperand(op);
1069 // If we are accessing the old induction variable, use the new one.
1070 if (SrcOp == OldInduction) {
1071 Params.push_back(getVectorValue(SrcOp));
1075 // Try using previously calculated values.
1076 Instruction *SrcInst = dyn_cast<Instruction>(SrcOp);
1078 // If the src is an instruction that appeared earlier in the basic block
1079 // then it should already be vectorized.
1080 if (SrcInst && OrigLoop->contains(SrcInst)) {
1081 assert(WidenMap.has(SrcInst) && "Source operand is unavailable");
1082 // The parameter is a vector value from earlier.
1083 Params.push_back(WidenMap.get(SrcInst));
1085 // The parameter is a scalar from outside the loop. Maybe even a constant.
1086 VectorParts Scalars;
1087 Scalars.append(UF, SrcOp);
1088 Params.push_back(Scalars);
1092 assert(Params.size() == Instr->getNumOperands() &&
1093 "Invalid number of operands");
1095 // Does this instruction return a value ?
1096 bool IsVoidRetTy = Instr->getType()->isVoidTy();
1098 Value *UndefVec = IsVoidRetTy ? 0 :
1099 UndefValue::get(VectorType::get(Instr->getType(), VF));
1100 // Create a new entry in the WidenMap and initialize it to Undef or Null.
1101 VectorParts &VecResults = WidenMap.splat(Instr, UndefVec);
1103 // For each vector unroll 'part':
1104 for (unsigned Part = 0; Part < UF; ++Part) {
1105 // For each scalar that we create:
1106 for (unsigned Width = 0; Width < VF; ++Width) {
1107 Instruction *Cloned = Instr->clone();
1109 Cloned->setName(Instr->getName() + ".cloned");
1110 // Replace the operands of the cloned instrucions with extracted scalars.
1111 for (unsigned op = 0, e = Instr->getNumOperands(); op != e; ++op) {
1112 Value *Op = Params[op][Part];
1113 // Param is a vector. Need to extract the right lane.
1114 if (Op->getType()->isVectorTy())
1115 Op = Builder.CreateExtractElement(Op, Builder.getInt32(Width));
1116 Cloned->setOperand(op, Op);
1119 // Place the cloned scalar in the new loop.
1120 Builder.Insert(Cloned);
1122 // If the original scalar returns a value we need to place it in a vector
1123 // so that future users will be able to use it.
1125 VecResults[Part] = Builder.CreateInsertElement(VecResults[Part], Cloned,
1126 Builder.getInt32(Width));
1132 InnerLoopVectorizer::addRuntimeCheck(LoopVectorizationLegality *Legal,
1134 LoopVectorizationLegality::RuntimePointerCheck *PtrRtCheck =
1135 Legal->getRuntimePointerCheck();
1137 if (!PtrRtCheck->Need)
1140 Instruction *MemoryRuntimeCheck = 0;
1141 unsigned NumPointers = PtrRtCheck->Pointers.size();
1142 SmallVector<Value* , 2> Starts;
1143 SmallVector<Value* , 2> Ends;
1145 SCEVExpander Exp(*SE, "induction");
1147 // Use this type for pointer arithmetic.
1148 Type* PtrArithTy = Type::getInt8PtrTy(Loc->getContext(), 0);
1150 for (unsigned i = 0; i < NumPointers; ++i) {
1151 Value *Ptr = PtrRtCheck->Pointers[i];
1152 const SCEV *Sc = SE->getSCEV(Ptr);
1154 if (SE->isLoopInvariant(Sc, OrigLoop)) {
1155 DEBUG(dbgs() << "LV: Adding RT check for a loop invariant ptr:" <<
1157 Starts.push_back(Ptr);
1158 Ends.push_back(Ptr);
1160 DEBUG(dbgs() << "LV: Adding RT check for range:" << *Ptr <<"\n");
1162 Value *Start = Exp.expandCodeFor(PtrRtCheck->Starts[i], PtrArithTy, Loc);
1163 Value *End = Exp.expandCodeFor(PtrRtCheck->Ends[i], PtrArithTy, Loc);
1164 Starts.push_back(Start);
1165 Ends.push_back(End);
1169 IRBuilder<> ChkBuilder(Loc);
1171 for (unsigned i = 0; i < NumPointers; ++i) {
1172 for (unsigned j = i+1; j < NumPointers; ++j) {
1173 // No need to check if two readonly pointers intersect.
1174 if (!PtrRtCheck->IsWritePtr[i] && !PtrRtCheck->IsWritePtr[j])
1177 Value *Start0 = ChkBuilder.CreateBitCast(Starts[i], PtrArithTy, "bc");
1178 Value *Start1 = ChkBuilder.CreateBitCast(Starts[j], PtrArithTy, "bc");
1179 Value *End0 = ChkBuilder.CreateBitCast(Ends[i], PtrArithTy, "bc");
1180 Value *End1 = ChkBuilder.CreateBitCast(Ends[j], PtrArithTy, "bc");
1182 Value *Cmp0 = ChkBuilder.CreateICmpULE(Start0, End1, "bound0");
1183 Value *Cmp1 = ChkBuilder.CreateICmpULE(Start1, End0, "bound1");
1184 Value *IsConflict = ChkBuilder.CreateAnd(Cmp0, Cmp1, "found.conflict");
1185 if (MemoryRuntimeCheck)
1186 IsConflict = ChkBuilder.CreateOr(MemoryRuntimeCheck, IsConflict,
1189 MemoryRuntimeCheck = cast<Instruction>(IsConflict);
1193 return MemoryRuntimeCheck;
1197 InnerLoopVectorizer::createEmptyLoop(LoopVectorizationLegality *Legal) {
1199 In this function we generate a new loop. The new loop will contain
1200 the vectorized instructions while the old loop will continue to run the
1203 [ ] <-- vector loop bypass (may consist of multiple blocks).
1206 | [ ] <-- vector pre header.
1210 | [ ]_| <-- vector loop.
1213 >[ ] <--- middle-block.
1216 | [ ] <--- new preheader.
1220 | [ ]_| <-- old scalar loop to handle remainder.
1223 >[ ] <-- exit block.
1227 BasicBlock *OldBasicBlock = OrigLoop->getHeader();
1228 BasicBlock *BypassBlock = OrigLoop->getLoopPreheader();
1229 BasicBlock *ExitBlock = OrigLoop->getExitBlock();
1230 assert(ExitBlock && "Must have an exit block");
1232 // Mark the old scalar loop with metadata that tells us not to vectorize this
1233 // loop again if we run into it.
1234 MDNode *MD = MDNode::get(OldBasicBlock->getContext(), ArrayRef<Value*>());
1235 OldBasicBlock->getTerminator()->setMetadata(AlreadyVectorizedMDName, MD);
1237 // Some loops have a single integer induction variable, while other loops
1238 // don't. One example is c++ iterators that often have multiple pointer
1239 // induction variables. In the code below we also support a case where we
1240 // don't have a single induction variable.
1241 OldInduction = Legal->getInduction();
1242 Type *IdxTy = OldInduction ? OldInduction->getType() :
1243 DL->getIntPtrType(SE->getContext());
1245 // Find the loop boundaries.
1246 const SCEV *ExitCount = SE->getExitCount(OrigLoop, OrigLoop->getLoopLatch());
1247 assert(ExitCount != SE->getCouldNotCompute() && "Invalid loop count");
1249 // Get the total trip count from the count by adding 1.
1250 ExitCount = SE->getAddExpr(ExitCount,
1251 SE->getConstant(ExitCount->getType(), 1));
1253 // Expand the trip count and place the new instructions in the preheader.
1254 // Notice that the pre-header does not change, only the loop body.
1255 SCEVExpander Exp(*SE, "induction");
1257 // Count holds the overall loop count (N).
1258 Value *Count = Exp.expandCodeFor(ExitCount, ExitCount->getType(),
1259 BypassBlock->getTerminator());
1261 // The loop index does not have to start at Zero. Find the original start
1262 // value from the induction PHI node. If we don't have an induction variable
1263 // then we know that it starts at zero.
1264 Value *StartIdx = OldInduction ?
1265 OldInduction->getIncomingValueForBlock(BypassBlock):
1266 ConstantInt::get(IdxTy, 0);
1268 assert(BypassBlock && "Invalid loop structure");
1269 LoopBypassBlocks.push_back(BypassBlock);
1271 // Split the single block loop into the two loop structure described above.
1272 BasicBlock *VectorPH =
1273 BypassBlock->splitBasicBlock(BypassBlock->getTerminator(), "vector.ph");
1274 BasicBlock *VecBody =
1275 VectorPH->splitBasicBlock(VectorPH->getTerminator(), "vector.body");
1276 BasicBlock *MiddleBlock =
1277 VecBody->splitBasicBlock(VecBody->getTerminator(), "middle.block");
1278 BasicBlock *ScalarPH =
1279 MiddleBlock->splitBasicBlock(MiddleBlock->getTerminator(), "scalar.ph");
1281 // Use this IR builder to create the loop instructions (Phi, Br, Cmp)
1283 Builder.SetInsertPoint(VecBody->getFirstInsertionPt());
1285 // Generate the induction variable.
1286 Induction = Builder.CreatePHI(IdxTy, 2, "index");
1287 // The loop step is equal to the vectorization factor (num of SIMD elements)
1288 // times the unroll factor (num of SIMD instructions).
1289 Constant *Step = ConstantInt::get(IdxTy, VF * UF);
1291 // This is the IR builder that we use to add all of the logic for bypassing
1292 // the new vector loop.
1293 IRBuilder<> BypassBuilder(BypassBlock->getTerminator());
1295 // We may need to extend the index in case there is a type mismatch.
1296 // We know that the count starts at zero and does not overflow.
1297 if (Count->getType() != IdxTy) {
1298 // The exit count can be of pointer type. Convert it to the correct
1300 if (ExitCount->getType()->isPointerTy())
1301 Count = BypassBuilder.CreatePointerCast(Count, IdxTy, "ptrcnt.to.int");
1303 Count = BypassBuilder.CreateZExtOrTrunc(Count, IdxTy, "cnt.cast");
1306 // Add the start index to the loop count to get the new end index.
1307 Value *IdxEnd = BypassBuilder.CreateAdd(Count, StartIdx, "end.idx");
1309 // Now we need to generate the expression for N - (N % VF), which is
1310 // the part that the vectorized body will execute.
1311 Value *R = BypassBuilder.CreateURem(Count, Step, "n.mod.vf");
1312 Value *CountRoundDown = BypassBuilder.CreateSub(Count, R, "n.vec");
1313 Value *IdxEndRoundDown = BypassBuilder.CreateAdd(CountRoundDown, StartIdx,
1314 "end.idx.rnd.down");
1316 // Now, compare the new count to zero. If it is zero skip the vector loop and
1317 // jump to the scalar loop.
1318 Value *Cmp = BypassBuilder.CreateICmpEQ(IdxEndRoundDown, StartIdx,
1321 BasicBlock *LastBypassBlock = BypassBlock;
1323 // Generate the code that checks in runtime if arrays overlap. We put the
1324 // checks into a separate block to make the more common case of few elements
1326 Instruction *MemRuntimeCheck = addRuntimeCheck(Legal,
1327 BypassBlock->getTerminator());
1328 if (MemRuntimeCheck) {
1329 // Create a new block containing the memory check.
1330 BasicBlock *CheckBlock = BypassBlock->splitBasicBlock(MemRuntimeCheck,
1332 LoopBypassBlocks.push_back(CheckBlock);
1334 // Replace the branch into the memory check block with a conditional branch
1335 // for the "few elements case".
1336 Instruction *OldTerm = BypassBlock->getTerminator();
1337 BranchInst::Create(MiddleBlock, CheckBlock, Cmp, OldTerm);
1338 OldTerm->eraseFromParent();
1340 Cmp = MemRuntimeCheck;
1341 LastBypassBlock = CheckBlock;
1344 LastBypassBlock->getTerminator()->eraseFromParent();
1345 BranchInst::Create(MiddleBlock, VectorPH, Cmp,
1348 // We are going to resume the execution of the scalar loop.
1349 // Go over all of the induction variables that we found and fix the
1350 // PHIs that are left in the scalar version of the loop.
1351 // The starting values of PHI nodes depend on the counter of the last
1352 // iteration in the vectorized loop.
1353 // If we come from a bypass edge then we need to start from the original
1356 // This variable saves the new starting index for the scalar loop.
1357 PHINode *ResumeIndex = 0;
1358 LoopVectorizationLegality::InductionList::iterator I, E;
1359 LoopVectorizationLegality::InductionList *List = Legal->getInductionVars();
1360 for (I = List->begin(), E = List->end(); I != E; ++I) {
1361 PHINode *OrigPhi = I->first;
1362 LoopVectorizationLegality::InductionInfo II = I->second;
1363 PHINode *ResumeVal = PHINode::Create(OrigPhi->getType(), 2, "resume.val",
1364 MiddleBlock->getTerminator());
1365 Value *EndValue = 0;
1367 case LoopVectorizationLegality::IK_NoInduction:
1368 llvm_unreachable("Unknown induction");
1369 case LoopVectorizationLegality::IK_IntInduction: {
1370 // Handle the integer induction counter:
1371 assert(OrigPhi->getType()->isIntegerTy() && "Invalid type");
1372 assert(OrigPhi == OldInduction && "Unknown integer PHI");
1373 // We know what the end value is.
1374 EndValue = IdxEndRoundDown;
1375 // We also know which PHI node holds it.
1376 ResumeIndex = ResumeVal;
1379 case LoopVectorizationLegality::IK_ReverseIntInduction: {
1380 // Convert the CountRoundDown variable to the PHI size.
1381 unsigned CRDSize = CountRoundDown->getType()->getScalarSizeInBits();
1382 unsigned IISize = II.StartValue->getType()->getScalarSizeInBits();
1383 Value *CRD = CountRoundDown;
1384 if (CRDSize > IISize)
1385 CRD = CastInst::Create(Instruction::Trunc, CountRoundDown,
1386 II.StartValue->getType(), "tr.crd",
1387 LoopBypassBlocks.back()->getTerminator());
1388 else if (CRDSize < IISize)
1389 CRD = CastInst::Create(Instruction::SExt, CountRoundDown,
1390 II.StartValue->getType(),
1392 LoopBypassBlocks.back()->getTerminator());
1393 // Handle reverse integer induction counter:
1395 BinaryOperator::CreateSub(II.StartValue, CRD, "rev.ind.end",
1396 LoopBypassBlocks.back()->getTerminator());
1399 case LoopVectorizationLegality::IK_PtrInduction: {
1400 // For pointer induction variables, calculate the offset using
1403 GetElementPtrInst::Create(II.StartValue, CountRoundDown, "ptr.ind.end",
1404 LoopBypassBlocks.back()->getTerminator());
1407 case LoopVectorizationLegality::IK_ReversePtrInduction: {
1408 // The value at the end of the loop for the reverse pointer is calculated
1409 // by creating a GEP with a negative index starting from the start value.
1410 Value *Zero = ConstantInt::get(CountRoundDown->getType(), 0);
1411 Value *NegIdx = BinaryOperator::CreateSub(Zero, CountRoundDown,
1413 LoopBypassBlocks.back()->getTerminator());
1414 EndValue = GetElementPtrInst::Create(II.StartValue, NegIdx,
1416 LoopBypassBlocks.back()->getTerminator());
1421 // The new PHI merges the original incoming value, in case of a bypass,
1422 // or the value at the end of the vectorized loop.
1423 for (unsigned I = 0, E = LoopBypassBlocks.size(); I != E; ++I)
1424 ResumeVal->addIncoming(II.StartValue, LoopBypassBlocks[I]);
1425 ResumeVal->addIncoming(EndValue, VecBody);
1427 // Fix the scalar body counter (PHI node).
1428 unsigned BlockIdx = OrigPhi->getBasicBlockIndex(ScalarPH);
1429 OrigPhi->setIncomingValue(BlockIdx, ResumeVal);
1432 // If we are generating a new induction variable then we also need to
1433 // generate the code that calculates the exit value. This value is not
1434 // simply the end of the counter because we may skip the vectorized body
1435 // in case of a runtime check.
1437 assert(!ResumeIndex && "Unexpected resume value found");
1438 ResumeIndex = PHINode::Create(IdxTy, 2, "new.indc.resume.val",
1439 MiddleBlock->getTerminator());
1440 for (unsigned I = 0, E = LoopBypassBlocks.size(); I != E; ++I)
1441 ResumeIndex->addIncoming(StartIdx, LoopBypassBlocks[I]);
1442 ResumeIndex->addIncoming(IdxEndRoundDown, VecBody);
1445 // Make sure that we found the index where scalar loop needs to continue.
1446 assert(ResumeIndex && ResumeIndex->getType()->isIntegerTy() &&
1447 "Invalid resume Index");
1449 // Add a check in the middle block to see if we have completed
1450 // all of the iterations in the first vector loop.
1451 // If (N - N%VF) == N, then we *don't* need to run the remainder.
1452 Value *CmpN = CmpInst::Create(Instruction::ICmp, CmpInst::ICMP_EQ, IdxEnd,
1453 ResumeIndex, "cmp.n",
1454 MiddleBlock->getTerminator());
1456 BranchInst::Create(ExitBlock, ScalarPH, CmpN, MiddleBlock->getTerminator());
1457 // Remove the old terminator.
1458 MiddleBlock->getTerminator()->eraseFromParent();
1460 // Create i+1 and fill the PHINode.
1461 Value *NextIdx = Builder.CreateAdd(Induction, Step, "index.next");
1462 Induction->addIncoming(StartIdx, VectorPH);
1463 Induction->addIncoming(NextIdx, VecBody);
1464 // Create the compare.
1465 Value *ICmp = Builder.CreateICmpEQ(NextIdx, IdxEndRoundDown);
1466 Builder.CreateCondBr(ICmp, MiddleBlock, VecBody);
1468 // Now we have two terminators. Remove the old one from the block.
1469 VecBody->getTerminator()->eraseFromParent();
1471 // Get ready to start creating new instructions into the vectorized body.
1472 Builder.SetInsertPoint(VecBody->getFirstInsertionPt());
1474 // Create and register the new vector loop.
1475 Loop* Lp = new Loop();
1476 Loop *ParentLoop = OrigLoop->getParentLoop();
1478 // Insert the new loop into the loop nest and register the new basic blocks.
1480 ParentLoop->addChildLoop(Lp);
1481 for (unsigned I = 1, E = LoopBypassBlocks.size(); I != E; ++I)
1482 ParentLoop->addBasicBlockToLoop(LoopBypassBlocks[I], LI->getBase());
1483 ParentLoop->addBasicBlockToLoop(ScalarPH, LI->getBase());
1484 ParentLoop->addBasicBlockToLoop(VectorPH, LI->getBase());
1485 ParentLoop->addBasicBlockToLoop(MiddleBlock, LI->getBase());
1487 LI->addTopLevelLoop(Lp);
1490 Lp->addBasicBlockToLoop(VecBody, LI->getBase());
1493 LoopVectorPreHeader = VectorPH;
1494 LoopScalarPreHeader = ScalarPH;
1495 LoopMiddleBlock = MiddleBlock;
1496 LoopExitBlock = ExitBlock;
1497 LoopVectorBody = VecBody;
1498 LoopScalarBody = OldBasicBlock;
1501 /// This function returns the identity element (or neutral element) for
1502 /// the operation K.
1504 LoopVectorizationLegality::getReductionIdentity(ReductionKind K, Type *Tp,
1505 MinMaxReductionKind MinMaxK) {
1510 // Adding, Xoring, Oring zero to a number does not change it.
1511 return ConstantInt::get(Tp, 0);
1512 case RK_IntegerMult:
1513 // Multiplying a number by 1 does not change it.
1514 return ConstantInt::get(Tp, 1);
1516 // AND-ing a number with an all-1 value does not change it.
1517 return ConstantInt::get(Tp, -1, true);
1519 // Multiplying a number by 1 does not change it.
1520 return ConstantFP::get(Tp, 1.0L);
1522 // Adding zero to a number does not change it.
1523 return ConstantFP::get(Tp, 0.0L);
1524 case RK_IntegerMinMax:
1526 default: llvm_unreachable("Unknown min/max predicate");
1528 return ConstantInt::getAllOnesValue(Tp);
1530 return ConstantInt::get(Tp, 0);
1532 unsigned BitWidth = Tp->getPrimitiveSizeInBits();
1533 return ConstantInt::get(Tp->getContext(),
1534 APInt::getSignedMaxValue(BitWidth));
1536 case LoopVectorizationLegality::MRK_SIntMax: {
1537 unsigned BitWidth = Tp->getPrimitiveSizeInBits();
1538 return ConstantInt::get(Tp->getContext(),
1539 APInt::getSignedMinValue(BitWidth));
1543 llvm_unreachable("Unknown reduction kind");
1547 static Intrinsic::ID
1548 getIntrinsicIDForCall(CallInst *CI, const TargetLibraryInfo *TLI) {
1549 // If we have an intrinsic call, check if it is trivially vectorizable.
1550 if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(CI)) {
1551 switch (II->getIntrinsicID()) {
1552 case Intrinsic::sqrt:
1553 case Intrinsic::sin:
1554 case Intrinsic::cos:
1555 case Intrinsic::exp:
1556 case Intrinsic::exp2:
1557 case Intrinsic::log:
1558 case Intrinsic::log10:
1559 case Intrinsic::log2:
1560 case Intrinsic::fabs:
1561 case Intrinsic::floor:
1562 case Intrinsic::ceil:
1563 case Intrinsic::trunc:
1564 case Intrinsic::rint:
1565 case Intrinsic::nearbyint:
1566 case Intrinsic::pow:
1567 case Intrinsic::fma:
1568 case Intrinsic::fmuladd:
1569 return II->getIntrinsicID();
1571 return Intrinsic::not_intrinsic;
1576 return Intrinsic::not_intrinsic;
1579 Function *F = CI->getCalledFunction();
1580 // We're going to make assumptions on the semantics of the functions, check
1581 // that the target knows that it's available in this environment.
1582 if (!F || !TLI->getLibFunc(F->getName(), Func))
1583 return Intrinsic::not_intrinsic;
1585 // Otherwise check if we have a call to a function that can be turned into a
1586 // vector intrinsic.
1593 return Intrinsic::sin;
1597 return Intrinsic::cos;
1601 return Intrinsic::exp;
1603 case LibFunc::exp2f:
1604 case LibFunc::exp2l:
1605 return Intrinsic::exp2;
1609 return Intrinsic::log;
1610 case LibFunc::log10:
1611 case LibFunc::log10f:
1612 case LibFunc::log10l:
1613 return Intrinsic::log10;
1615 case LibFunc::log2f:
1616 case LibFunc::log2l:
1617 return Intrinsic::log2;
1619 case LibFunc::fabsf:
1620 case LibFunc::fabsl:
1621 return Intrinsic::fabs;
1622 case LibFunc::floor:
1623 case LibFunc::floorf:
1624 case LibFunc::floorl:
1625 return Intrinsic::floor;
1627 case LibFunc::ceilf:
1628 case LibFunc::ceill:
1629 return Intrinsic::ceil;
1630 case LibFunc::trunc:
1631 case LibFunc::truncf:
1632 case LibFunc::truncl:
1633 return Intrinsic::trunc;
1635 case LibFunc::rintf:
1636 case LibFunc::rintl:
1637 return Intrinsic::rint;
1638 case LibFunc::nearbyint:
1639 case LibFunc::nearbyintf:
1640 case LibFunc::nearbyintl:
1641 return Intrinsic::nearbyint;
1645 return Intrinsic::pow;
1648 return Intrinsic::not_intrinsic;
1651 /// This function translates the reduction kind to an LLVM binary operator.
1653 getReductionBinOp(LoopVectorizationLegality::ReductionKind Kind) {
1655 case LoopVectorizationLegality::RK_IntegerAdd:
1656 return Instruction::Add;
1657 case LoopVectorizationLegality::RK_IntegerMult:
1658 return Instruction::Mul;
1659 case LoopVectorizationLegality::RK_IntegerOr:
1660 return Instruction::Or;
1661 case LoopVectorizationLegality::RK_IntegerAnd:
1662 return Instruction::And;
1663 case LoopVectorizationLegality::RK_IntegerXor:
1664 return Instruction::Xor;
1665 case LoopVectorizationLegality::RK_FloatMult:
1666 return Instruction::FMul;
1667 case LoopVectorizationLegality::RK_FloatAdd:
1668 return Instruction::FAdd;
1669 case LoopVectorizationLegality::RK_IntegerMinMax:
1670 return Instruction::ICmp;
1672 llvm_unreachable("Unknown reduction operation");
1676 Value *createMinMaxOp(IRBuilder<> &Builder,
1677 LoopVectorizationLegality::MinMaxReductionKind RK,
1680 CmpInst::Predicate P = CmpInst::ICMP_NE;
1683 llvm_unreachable("Unknown min/max reduction kind");
1684 case LoopVectorizationLegality::MRK_UIntMin:
1685 P = CmpInst::ICMP_ULT;
1687 case LoopVectorizationLegality::MRK_UIntMax:
1688 P = CmpInst::ICMP_UGT;
1690 case LoopVectorizationLegality::MRK_SIntMin:
1691 P = CmpInst::ICMP_SLT;
1693 case LoopVectorizationLegality::MRK_SIntMax:
1694 P = CmpInst::ICMP_SGT;
1696 Value *Cmp = Builder.CreateICmp(P, Left, Right, "rdx.minmax.cmp");
1697 Value *Select = Builder.CreateSelect(Cmp, Left, Right, "rdx.minmax.select");
1702 InnerLoopVectorizer::vectorizeLoop(LoopVectorizationLegality *Legal) {
1703 //===------------------------------------------------===//
1705 // Notice: any optimization or new instruction that go
1706 // into the code below should be also be implemented in
1709 //===------------------------------------------------===//
1710 Constant *Zero = Builder.getInt32(0);
1712 // In order to support reduction variables we need to be able to vectorize
1713 // Phi nodes. Phi nodes have cycles, so we need to vectorize them in two
1714 // stages. First, we create a new vector PHI node with no incoming edges.
1715 // We use this value when we vectorize all of the instructions that use the
1716 // PHI. Next, after all of the instructions in the block are complete we
1717 // add the new incoming edges to the PHI. At this point all of the
1718 // instructions in the basic block are vectorized, so we can use them to
1719 // construct the PHI.
1720 PhiVector RdxPHIsToFix;
1722 // Scan the loop in a topological order to ensure that defs are vectorized
1724 LoopBlocksDFS DFS(OrigLoop);
1727 // Vectorize all of the blocks in the original loop.
1728 for (LoopBlocksDFS::RPOIterator bb = DFS.beginRPO(),
1729 be = DFS.endRPO(); bb != be; ++bb)
1730 vectorizeBlockInLoop(Legal, *bb, &RdxPHIsToFix);
1732 // At this point every instruction in the original loop is widened to
1733 // a vector form. We are almost done. Now, we need to fix the PHI nodes
1734 // that we vectorized. The PHI nodes are currently empty because we did
1735 // not want to introduce cycles. Notice that the remaining PHI nodes
1736 // that we need to fix are reduction variables.
1738 // Create the 'reduced' values for each of the induction vars.
1739 // The reduced values are the vector values that we scalarize and combine
1740 // after the loop is finished.
1741 for (PhiVector::iterator it = RdxPHIsToFix.begin(), e = RdxPHIsToFix.end();
1743 PHINode *RdxPhi = *it;
1744 assert(RdxPhi && "Unable to recover vectorized PHI");
1746 // Find the reduction variable descriptor.
1747 assert(Legal->getReductionVars()->count(RdxPhi) &&
1748 "Unable to find the reduction variable");
1749 LoopVectorizationLegality::ReductionDescriptor RdxDesc =
1750 (*Legal->getReductionVars())[RdxPhi];
1752 // We need to generate a reduction vector from the incoming scalar.
1753 // To do so, we need to generate the 'identity' vector and overide
1754 // one of the elements with the incoming scalar reduction. We need
1755 // to do it in the vector-loop preheader.
1756 Builder.SetInsertPoint(LoopBypassBlocks.front()->getTerminator());
1758 // This is the vector-clone of the value that leaves the loop.
1759 VectorParts &VectorExit = getVectorValue(RdxDesc.LoopExitInstr);
1760 Type *VecTy = VectorExit[0]->getType();
1762 // Find the reduction identity variable. Zero for addition, or, xor,
1763 // one for multiplication, -1 for And.
1765 LoopVectorizationLegality::getReductionIdentity(RdxDesc.Kind,
1766 VecTy->getScalarType(),
1767 RdxDesc.MinMaxKind);
1768 Constant *Identity = ConstantVector::getSplat(VF, Iden);
1770 // This vector is the Identity vector where the first element is the
1771 // incoming scalar reduction.
1772 Value *VectorStart = Builder.CreateInsertElement(Identity,
1773 RdxDesc.StartValue, Zero);
1775 // Fix the vector-loop phi.
1776 // We created the induction variable so we know that the
1777 // preheader is the first entry.
1778 BasicBlock *VecPreheader = Induction->getIncomingBlock(0);
1780 // Reductions do not have to start at zero. They can start with
1781 // any loop invariant values.
1782 VectorParts &VecRdxPhi = WidenMap.get(RdxPhi);
1783 BasicBlock *Latch = OrigLoop->getLoopLatch();
1784 Value *LoopVal = RdxPhi->getIncomingValueForBlock(Latch);
1785 VectorParts &Val = getVectorValue(LoopVal);
1786 for (unsigned part = 0; part < UF; ++part) {
1787 // Make sure to add the reduction stat value only to the
1788 // first unroll part.
1789 Value *StartVal = (part == 0) ? VectorStart : Identity;
1790 cast<PHINode>(VecRdxPhi[part])->addIncoming(StartVal, VecPreheader);
1791 cast<PHINode>(VecRdxPhi[part])->addIncoming(Val[part], LoopVectorBody);
1794 // Before each round, move the insertion point right between
1795 // the PHIs and the values we are going to write.
1796 // This allows us to write both PHINodes and the extractelement
1798 Builder.SetInsertPoint(LoopMiddleBlock->getFirstInsertionPt());
1800 VectorParts RdxParts;
1801 for (unsigned part = 0; part < UF; ++part) {
1802 // This PHINode contains the vectorized reduction variable, or
1803 // the initial value vector, if we bypass the vector loop.
1804 VectorParts &RdxExitVal = getVectorValue(RdxDesc.LoopExitInstr);
1805 PHINode *NewPhi = Builder.CreatePHI(VecTy, 2, "rdx.vec.exit.phi");
1806 Value *StartVal = (part == 0) ? VectorStart : Identity;
1807 for (unsigned I = 0, E = LoopBypassBlocks.size(); I != E; ++I)
1808 NewPhi->addIncoming(StartVal, LoopBypassBlocks[I]);
1809 NewPhi->addIncoming(RdxExitVal[part], LoopVectorBody);
1810 RdxParts.push_back(NewPhi);
1813 // Reduce all of the unrolled parts into a single vector.
1814 Value *ReducedPartRdx = RdxParts[0];
1815 unsigned Op = getReductionBinOp(RdxDesc.Kind);
1816 for (unsigned part = 1; part < UF; ++part) {
1817 if (Op != Instruction::ICmp)
1818 ReducedPartRdx = Builder.CreateBinOp((Instruction::BinaryOps)Op,
1819 RdxParts[part], ReducedPartRdx,
1822 ReducedPartRdx = createMinMaxOp(Builder, RdxDesc.MinMaxKind,
1823 ReducedPartRdx, RdxParts[part]);
1826 // VF is a power of 2 so we can emit the reduction using log2(VF) shuffles
1827 // and vector ops, reducing the set of values being computed by half each
1829 assert(isPowerOf2_32(VF) &&
1830 "Reduction emission only supported for pow2 vectors!");
1831 Value *TmpVec = ReducedPartRdx;
1832 SmallVector<Constant*, 32> ShuffleMask(VF, 0);
1833 for (unsigned i = VF; i != 1; i >>= 1) {
1834 // Move the upper half of the vector to the lower half.
1835 for (unsigned j = 0; j != i/2; ++j)
1836 ShuffleMask[j] = Builder.getInt32(i/2 + j);
1838 // Fill the rest of the mask with undef.
1839 std::fill(&ShuffleMask[i/2], ShuffleMask.end(),
1840 UndefValue::get(Builder.getInt32Ty()));
1843 Builder.CreateShuffleVector(TmpVec,
1844 UndefValue::get(TmpVec->getType()),
1845 ConstantVector::get(ShuffleMask),
1848 if (Op != Instruction::ICmp)
1849 TmpVec = Builder.CreateBinOp((Instruction::BinaryOps)Op, TmpVec, Shuf,
1852 TmpVec = createMinMaxOp(Builder, RdxDesc.MinMaxKind, TmpVec, Shuf);
1855 // The result is in the first element of the vector.
1856 Value *Scalar0 = Builder.CreateExtractElement(TmpVec, Builder.getInt32(0));
1858 // Now, we need to fix the users of the reduction variable
1859 // inside and outside of the scalar remainder loop.
1860 // We know that the loop is in LCSSA form. We need to update the
1861 // PHI nodes in the exit blocks.
1862 for (BasicBlock::iterator LEI = LoopExitBlock->begin(),
1863 LEE = LoopExitBlock->end(); LEI != LEE; ++LEI) {
1864 PHINode *LCSSAPhi = dyn_cast<PHINode>(LEI);
1865 if (!LCSSAPhi) continue;
1867 // All PHINodes need to have a single entry edge, or two if
1868 // we already fixed them.
1869 assert(LCSSAPhi->getNumIncomingValues() < 3 && "Invalid LCSSA PHI");
1871 // We found our reduction value exit-PHI. Update it with the
1872 // incoming bypass edge.
1873 if (LCSSAPhi->getIncomingValue(0) == RdxDesc.LoopExitInstr) {
1874 // Add an edge coming from the bypass.
1875 LCSSAPhi->addIncoming(Scalar0, LoopMiddleBlock);
1878 }// end of the LCSSA phi scan.
1880 // Fix the scalar loop reduction variable with the incoming reduction sum
1881 // from the vector body and from the backedge value.
1882 int IncomingEdgeBlockIdx =
1883 (RdxPhi)->getBasicBlockIndex(OrigLoop->getLoopLatch());
1884 assert(IncomingEdgeBlockIdx >= 0 && "Invalid block index");
1885 // Pick the other block.
1886 int SelfEdgeBlockIdx = (IncomingEdgeBlockIdx ? 0 : 1);
1887 (RdxPhi)->setIncomingValue(SelfEdgeBlockIdx, Scalar0);
1888 (RdxPhi)->setIncomingValue(IncomingEdgeBlockIdx, RdxDesc.LoopExitInstr);
1889 }// end of for each redux variable.
1891 // The Loop exit block may have single value PHI nodes where the incoming
1892 // value is 'undef'. While vectorizing we only handled real values that
1893 // were defined inside the loop. Here we handle the 'undef case'.
1895 for (BasicBlock::iterator LEI = LoopExitBlock->begin(),
1896 LEE = LoopExitBlock->end(); LEI != LEE; ++LEI) {
1897 PHINode *LCSSAPhi = dyn_cast<PHINode>(LEI);
1898 if (!LCSSAPhi) continue;
1899 if (LCSSAPhi->getNumIncomingValues() == 1)
1900 LCSSAPhi->addIncoming(UndefValue::get(LCSSAPhi->getType()),
1905 InnerLoopVectorizer::VectorParts
1906 InnerLoopVectorizer::createEdgeMask(BasicBlock *Src, BasicBlock *Dst) {
1907 assert(std::find(pred_begin(Dst), pred_end(Dst), Src) != pred_end(Dst) &&
1910 VectorParts SrcMask = createBlockInMask(Src);
1912 // The terminator has to be a branch inst!
1913 BranchInst *BI = dyn_cast<BranchInst>(Src->getTerminator());
1914 assert(BI && "Unexpected terminator found");
1916 if (BI->isConditional()) {
1917 VectorParts EdgeMask = getVectorValue(BI->getCondition());
1919 if (BI->getSuccessor(0) != Dst)
1920 for (unsigned part = 0; part < UF; ++part)
1921 EdgeMask[part] = Builder.CreateNot(EdgeMask[part]);
1923 for (unsigned part = 0; part < UF; ++part)
1924 EdgeMask[part] = Builder.CreateAnd(EdgeMask[part], SrcMask[part]);
1931 InnerLoopVectorizer::VectorParts
1932 InnerLoopVectorizer::createBlockInMask(BasicBlock *BB) {
1933 assert(OrigLoop->contains(BB) && "Block is not a part of a loop");
1935 // Loop incoming mask is all-one.
1936 if (OrigLoop->getHeader() == BB) {
1937 Value *C = ConstantInt::get(IntegerType::getInt1Ty(BB->getContext()), 1);
1938 return getVectorValue(C);
1941 // This is the block mask. We OR all incoming edges, and with zero.
1942 Value *Zero = ConstantInt::get(IntegerType::getInt1Ty(BB->getContext()), 0);
1943 VectorParts BlockMask = getVectorValue(Zero);
1946 for (pred_iterator it = pred_begin(BB), e = pred_end(BB); it != e; ++it) {
1947 VectorParts EM = createEdgeMask(*it, BB);
1948 for (unsigned part = 0; part < UF; ++part)
1949 BlockMask[part] = Builder.CreateOr(BlockMask[part], EM[part]);
1956 InnerLoopVectorizer::vectorizeBlockInLoop(LoopVectorizationLegality *Legal,
1957 BasicBlock *BB, PhiVector *PV) {
1958 // For each instruction in the old loop.
1959 for (BasicBlock::iterator it = BB->begin(), e = BB->end(); it != e; ++it) {
1960 VectorParts &Entry = WidenMap.get(it);
1961 switch (it->getOpcode()) {
1962 case Instruction::Br:
1963 // Nothing to do for PHIs and BR, since we already took care of the
1964 // loop control flow instructions.
1966 case Instruction::PHI:{
1967 PHINode* P = cast<PHINode>(it);
1968 // Handle reduction variables:
1969 if (Legal->getReductionVars()->count(P)) {
1970 for (unsigned part = 0; part < UF; ++part) {
1971 // This is phase one of vectorizing PHIs.
1972 Type *VecTy = VectorType::get(it->getType(), VF);
1973 Entry[part] = PHINode::Create(VecTy, 2, "vec.phi",
1974 LoopVectorBody-> getFirstInsertionPt());
1980 // Check for PHI nodes that are lowered to vector selects.
1981 if (P->getParent() != OrigLoop->getHeader()) {
1982 // We know that all PHIs in non header blocks are converted into
1983 // selects, so we don't have to worry about the insertion order and we
1984 // can just use the builder.
1985 // At this point we generate the predication tree. There may be
1986 // duplications since this is a simple recursive scan, but future
1987 // optimizations will clean it up.
1989 unsigned NumIncoming = P->getNumIncomingValues();
1990 assert(NumIncoming > 1 && "Invalid PHI");
1992 // Generate a sequence of selects of the form:
1993 // SELECT(Mask3, In3,
1994 // SELECT(Mask2, In2,
1996 for (unsigned In = 0; In < NumIncoming; In++) {
1997 VectorParts Cond = createEdgeMask(P->getIncomingBlock(In),
1999 VectorParts &In0 = getVectorValue(P->getIncomingValue(In));
2001 for (unsigned part = 0; part < UF; ++part) {
2002 // We don't need to 'select' the first PHI operand because it is
2003 // the default value if all of the other masks don't match.
2005 Entry[part] = In0[part];
2007 // Select between the current value and the previous incoming edge
2008 // based on the incoming mask.
2009 Entry[part] = Builder.CreateSelect(Cond[part], In0[part],
2010 Entry[part], "predphi");
2016 // This PHINode must be an induction variable.
2017 // Make sure that we know about it.
2018 assert(Legal->getInductionVars()->count(P) &&
2019 "Not an induction variable");
2021 LoopVectorizationLegality::InductionInfo II =
2022 Legal->getInductionVars()->lookup(P);
2025 case LoopVectorizationLegality::IK_NoInduction:
2026 llvm_unreachable("Unknown induction");
2027 case LoopVectorizationLegality::IK_IntInduction: {
2028 assert(P == OldInduction && "Unexpected PHI");
2029 Value *Broadcasted = getBroadcastInstrs(Induction);
2030 // After broadcasting the induction variable we need to make the
2031 // vector consecutive by adding 0, 1, 2 ...
2032 for (unsigned part = 0; part < UF; ++part)
2033 Entry[part] = getConsecutiveVector(Broadcasted, VF * part, false);
2036 case LoopVectorizationLegality::IK_ReverseIntInduction:
2037 case LoopVectorizationLegality::IK_PtrInduction:
2038 case LoopVectorizationLegality::IK_ReversePtrInduction:
2039 // Handle reverse integer and pointer inductions.
2040 Value *StartIdx = 0;
2041 // If we have a single integer induction variable then use it.
2042 // Otherwise, start counting at zero.
2044 LoopVectorizationLegality::InductionInfo OldII =
2045 Legal->getInductionVars()->lookup(OldInduction);
2046 StartIdx = OldII.StartValue;
2048 StartIdx = ConstantInt::get(Induction->getType(), 0);
2050 // This is the normalized GEP that starts counting at zero.
2051 Value *NormalizedIdx = Builder.CreateSub(Induction, StartIdx,
2054 // Handle the reverse integer induction variable case.
2055 if (LoopVectorizationLegality::IK_ReverseIntInduction == II.IK) {
2056 IntegerType *DstTy = cast<IntegerType>(II.StartValue->getType());
2057 Value *CNI = Builder.CreateSExtOrTrunc(NormalizedIdx, DstTy,
2059 Value *ReverseInd = Builder.CreateSub(II.StartValue, CNI,
2062 // This is a new value so do not hoist it out.
2063 Value *Broadcasted = getBroadcastInstrs(ReverseInd);
2064 // After broadcasting the induction variable we need to make the
2065 // vector consecutive by adding ... -3, -2, -1, 0.
2066 for (unsigned part = 0; part < UF; ++part)
2067 Entry[part] = getConsecutiveVector(Broadcasted, -VF * part, true);
2071 // Handle the pointer induction variable case.
2072 assert(P->getType()->isPointerTy() && "Unexpected type.");
2074 // Is this a reverse induction ptr or a consecutive induction ptr.
2075 bool Reverse = (LoopVectorizationLegality::IK_ReversePtrInduction ==
2078 // This is the vector of results. Notice that we don't generate
2079 // vector geps because scalar geps result in better code.
2080 for (unsigned part = 0; part < UF; ++part) {
2081 Value *VecVal = UndefValue::get(VectorType::get(P->getType(), VF));
2082 for (unsigned int i = 0; i < VF; ++i) {
2083 int EltIndex = (i + part * VF) * (Reverse ? -1 : 1);
2084 Constant *Idx = ConstantInt::get(Induction->getType(), EltIndex);
2087 GlobalIdx = Builder.CreateAdd(NormalizedIdx, Idx, "gep.idx");
2089 GlobalIdx = Builder.CreateSub(Idx, NormalizedIdx, "gep.ridx");
2091 Value *SclrGep = Builder.CreateGEP(II.StartValue, GlobalIdx,
2093 VecVal = Builder.CreateInsertElement(VecVal, SclrGep,
2094 Builder.getInt32(i),
2097 Entry[part] = VecVal;
2104 case Instruction::Add:
2105 case Instruction::FAdd:
2106 case Instruction::Sub:
2107 case Instruction::FSub:
2108 case Instruction::Mul:
2109 case Instruction::FMul:
2110 case Instruction::UDiv:
2111 case Instruction::SDiv:
2112 case Instruction::FDiv:
2113 case Instruction::URem:
2114 case Instruction::SRem:
2115 case Instruction::FRem:
2116 case Instruction::Shl:
2117 case Instruction::LShr:
2118 case Instruction::AShr:
2119 case Instruction::And:
2120 case Instruction::Or:
2121 case Instruction::Xor: {
2122 // Just widen binops.
2123 BinaryOperator *BinOp = dyn_cast<BinaryOperator>(it);
2124 VectorParts &A = getVectorValue(it->getOperand(0));
2125 VectorParts &B = getVectorValue(it->getOperand(1));
2127 // Use this vector value for all users of the original instruction.
2128 for (unsigned Part = 0; Part < UF; ++Part) {
2129 Value *V = Builder.CreateBinOp(BinOp->getOpcode(), A[Part], B[Part]);
2131 // Update the NSW, NUW and Exact flags. Notice: V can be an Undef.
2132 BinaryOperator *VecOp = dyn_cast<BinaryOperator>(V);
2133 if (VecOp && isa<OverflowingBinaryOperator>(BinOp)) {
2134 VecOp->setHasNoSignedWrap(BinOp->hasNoSignedWrap());
2135 VecOp->setHasNoUnsignedWrap(BinOp->hasNoUnsignedWrap());
2137 if (VecOp && isa<PossiblyExactOperator>(VecOp))
2138 VecOp->setIsExact(BinOp->isExact());
2144 case Instruction::Select: {
2146 // If the selector is loop invariant we can create a select
2147 // instruction with a scalar condition. Otherwise, use vector-select.
2148 bool InvariantCond = SE->isLoopInvariant(SE->getSCEV(it->getOperand(0)),
2151 // The condition can be loop invariant but still defined inside the
2152 // loop. This means that we can't just use the original 'cond' value.
2153 // We have to take the 'vectorized' value and pick the first lane.
2154 // Instcombine will make this a no-op.
2155 VectorParts &Cond = getVectorValue(it->getOperand(0));
2156 VectorParts &Op0 = getVectorValue(it->getOperand(1));
2157 VectorParts &Op1 = getVectorValue(it->getOperand(2));
2158 Value *ScalarCond = Builder.CreateExtractElement(Cond[0],
2159 Builder.getInt32(0));
2160 for (unsigned Part = 0; Part < UF; ++Part) {
2161 Entry[Part] = Builder.CreateSelect(
2162 InvariantCond ? ScalarCond : Cond[Part],
2169 case Instruction::ICmp:
2170 case Instruction::FCmp: {
2171 // Widen compares. Generate vector compares.
2172 bool FCmp = (it->getOpcode() == Instruction::FCmp);
2173 CmpInst *Cmp = dyn_cast<CmpInst>(it);
2174 VectorParts &A = getVectorValue(it->getOperand(0));
2175 VectorParts &B = getVectorValue(it->getOperand(1));
2176 for (unsigned Part = 0; Part < UF; ++Part) {
2179 C = Builder.CreateFCmp(Cmp->getPredicate(), A[Part], B[Part]);
2181 C = Builder.CreateICmp(Cmp->getPredicate(), A[Part], B[Part]);
2187 case Instruction::Store:
2188 case Instruction::Load:
2189 vectorizeMemoryInstruction(it, Legal);
2191 case Instruction::ZExt:
2192 case Instruction::SExt:
2193 case Instruction::FPToUI:
2194 case Instruction::FPToSI:
2195 case Instruction::FPExt:
2196 case Instruction::PtrToInt:
2197 case Instruction::IntToPtr:
2198 case Instruction::SIToFP:
2199 case Instruction::UIToFP:
2200 case Instruction::Trunc:
2201 case Instruction::FPTrunc:
2202 case Instruction::BitCast: {
2203 CastInst *CI = dyn_cast<CastInst>(it);
2204 /// Optimize the special case where the source is the induction
2205 /// variable. Notice that we can only optimize the 'trunc' case
2206 /// because: a. FP conversions lose precision, b. sext/zext may wrap,
2207 /// c. other casts depend on pointer size.
2208 if (CI->getOperand(0) == OldInduction &&
2209 it->getOpcode() == Instruction::Trunc) {
2210 Value *ScalarCast = Builder.CreateCast(CI->getOpcode(), Induction,
2212 Value *Broadcasted = getBroadcastInstrs(ScalarCast);
2213 for (unsigned Part = 0; Part < UF; ++Part)
2214 Entry[Part] = getConsecutiveVector(Broadcasted, VF * Part, false);
2217 /// Vectorize casts.
2218 Type *DestTy = VectorType::get(CI->getType()->getScalarType(), VF);
2220 VectorParts &A = getVectorValue(it->getOperand(0));
2221 for (unsigned Part = 0; Part < UF; ++Part)
2222 Entry[Part] = Builder.CreateCast(CI->getOpcode(), A[Part], DestTy);
2226 case Instruction::Call: {
2227 // Ignore dbg intrinsics.
2228 if (isa<DbgInfoIntrinsic>(it))
2231 Module *M = BB->getParent()->getParent();
2232 CallInst *CI = cast<CallInst>(it);
2233 Intrinsic::ID ID = getIntrinsicIDForCall(CI, TLI);
2234 assert(ID && "Not an intrinsic call!");
2235 for (unsigned Part = 0; Part < UF; ++Part) {
2236 SmallVector<Value*, 4> Args;
2237 for (unsigned i = 0, ie = CI->getNumArgOperands(); i != ie; ++i) {
2238 VectorParts &Arg = getVectorValue(CI->getArgOperand(i));
2239 Args.push_back(Arg[Part]);
2241 Type *Tys[] = { VectorType::get(CI->getType()->getScalarType(), VF) };
2242 Function *F = Intrinsic::getDeclaration(M, ID, Tys);
2243 Entry[Part] = Builder.CreateCall(F, Args);
2249 // All other instructions are unsupported. Scalarize them.
2250 scalarizeInstruction(it);
2253 }// end of for_each instr.
2256 void InnerLoopVectorizer::updateAnalysis() {
2257 // Forget the original basic block.
2258 SE->forgetLoop(OrigLoop);
2260 // Update the dominator tree information.
2261 assert(DT->properlyDominates(LoopBypassBlocks.front(), LoopExitBlock) &&
2262 "Entry does not dominate exit.");
2264 for (unsigned I = 1, E = LoopBypassBlocks.size(); I != E; ++I)
2265 DT->addNewBlock(LoopBypassBlocks[I], LoopBypassBlocks[I-1]);
2266 DT->addNewBlock(LoopVectorPreHeader, LoopBypassBlocks.back());
2267 DT->addNewBlock(LoopVectorBody, LoopVectorPreHeader);
2268 DT->addNewBlock(LoopMiddleBlock, LoopBypassBlocks.front());
2269 DT->addNewBlock(LoopScalarPreHeader, LoopMiddleBlock);
2270 DT->changeImmediateDominator(LoopScalarBody, LoopScalarPreHeader);
2271 DT->changeImmediateDominator(LoopExitBlock, LoopMiddleBlock);
2273 DEBUG(DT->verifyAnalysis());
2276 bool LoopVectorizationLegality::canVectorizeWithIfConvert() {
2277 if (!EnableIfConversion)
2280 assert(TheLoop->getNumBlocks() > 1 && "Single block loops are vectorizable");
2281 std::vector<BasicBlock*> &LoopBlocks = TheLoop->getBlocksVector();
2283 // Collect the blocks that need predication.
2284 for (unsigned i = 0, e = LoopBlocks.size(); i < e; ++i) {
2285 BasicBlock *BB = LoopBlocks[i];
2287 // We don't support switch statements inside loops.
2288 if (!isa<BranchInst>(BB->getTerminator()))
2291 // We must be able to predicate all blocks that need to be predicated.
2292 if (blockNeedsPredication(BB) && !blockCanBePredicated(BB))
2296 // We can if-convert this loop.
2300 bool LoopVectorizationLegality::canVectorize() {
2301 assert(TheLoop->getLoopPreheader() && "No preheader!!");
2303 // We can only vectorize innermost loops.
2304 if (TheLoop->getSubLoopsVector().size())
2307 // We must have a single backedge.
2308 if (TheLoop->getNumBackEdges() != 1)
2311 // We must have a single exiting block.
2312 if (!TheLoop->getExitingBlock())
2315 unsigned NumBlocks = TheLoop->getNumBlocks();
2317 // Check if we can if-convert non single-bb loops.
2318 if (NumBlocks != 1 && !canVectorizeWithIfConvert()) {
2319 DEBUG(dbgs() << "LV: Can't if-convert the loop.\n");
2323 // We need to have a loop header.
2324 BasicBlock *Latch = TheLoop->getLoopLatch();
2325 DEBUG(dbgs() << "LV: Found a loop: " <<
2326 TheLoop->getHeader()->getName() << "\n");
2328 // ScalarEvolution needs to be able to find the exit count.
2329 const SCEV *ExitCount = SE->getExitCount(TheLoop, Latch);
2330 if (ExitCount == SE->getCouldNotCompute()) {
2331 DEBUG(dbgs() << "LV: SCEV could not compute the loop exit count.\n");
2335 // Do not loop-vectorize loops with a tiny trip count.
2336 unsigned TC = SE->getSmallConstantTripCount(TheLoop, Latch);
2337 if (TC > 0u && TC < TinyTripCountVectorThreshold) {
2338 DEBUG(dbgs() << "LV: Found a loop with a very small trip count. " <<
2339 "This loop is not worth vectorizing.\n");
2343 // Check if we can vectorize the instructions and CFG in this loop.
2344 if (!canVectorizeInstrs()) {
2345 DEBUG(dbgs() << "LV: Can't vectorize the instructions or CFG\n");
2349 // Go over each instruction and look at memory deps.
2350 if (!canVectorizeMemory()) {
2351 DEBUG(dbgs() << "LV: Can't vectorize due to memory conflicts\n");
2355 // Collect all of the variables that remain uniform after vectorization.
2356 collectLoopUniforms();
2358 DEBUG(dbgs() << "LV: We can vectorize this loop" <<
2359 (PtrRtCheck.Need ? " (with a runtime bound check)" : "")
2362 // Okay! We can vectorize. At this point we don't have any other mem analysis
2363 // which may limit our maximum vectorization factor, so just return true with
2368 bool LoopVectorizationLegality::canVectorizeInstrs() {
2369 BasicBlock *PreHeader = TheLoop->getLoopPreheader();
2370 BasicBlock *Header = TheLoop->getHeader();
2372 // If we marked the scalar loop as "already vectorized" then no need
2373 // to vectorize it again.
2374 if (Header->getTerminator()->getMetadata(AlreadyVectorizedMDName)) {
2375 DEBUG(dbgs() << "LV: This loop was vectorized before\n");
2379 // For each block in the loop.
2380 for (Loop::block_iterator bb = TheLoop->block_begin(),
2381 be = TheLoop->block_end(); bb != be; ++bb) {
2383 // Scan the instructions in the block and look for hazards.
2384 for (BasicBlock::iterator it = (*bb)->begin(), e = (*bb)->end(); it != e;
2387 if (PHINode *Phi = dyn_cast<PHINode>(it)) {
2388 // Check that this PHI type is allowed.
2389 if (!Phi->getType()->isIntegerTy() &&
2390 !Phi->getType()->isFloatingPointTy() &&
2391 !Phi->getType()->isPointerTy()) {
2392 DEBUG(dbgs() << "LV: Found an non-int non-pointer PHI.\n");
2396 // If this PHINode is not in the header block, then we know that we
2397 // can convert it to select during if-conversion. No need to check if
2398 // the PHIs in this block are induction or reduction variables.
2402 // We only allow if-converted PHIs with more than two incoming values.
2403 if (Phi->getNumIncomingValues() != 2) {
2404 DEBUG(dbgs() << "LV: Found an invalid PHI.\n");
2408 // This is the value coming from the preheader.
2409 Value *StartValue = Phi->getIncomingValueForBlock(PreHeader);
2410 // Check if this is an induction variable.
2411 InductionKind IK = isInductionVariable(Phi);
2413 if (IK_NoInduction != IK) {
2414 // Int inductions are special because we only allow one IV.
2415 if (IK == IK_IntInduction) {
2417 DEBUG(dbgs() << "LV: Found too many inductions."<< *Phi <<"\n");
2423 DEBUG(dbgs() << "LV: Found an induction variable.\n");
2424 Inductions[Phi] = InductionInfo(StartValue, IK);
2428 if (AddReductionVar(Phi, RK_IntegerAdd)) {
2429 DEBUG(dbgs() << "LV: Found an ADD reduction PHI."<< *Phi <<"\n");
2432 if (AddReductionVar(Phi, RK_IntegerMult)) {
2433 DEBUG(dbgs() << "LV: Found a MUL reduction PHI."<< *Phi <<"\n");
2436 if (AddReductionVar(Phi, RK_IntegerOr)) {
2437 DEBUG(dbgs() << "LV: Found an OR reduction PHI."<< *Phi <<"\n");
2440 if (AddReductionVar(Phi, RK_IntegerAnd)) {
2441 DEBUG(dbgs() << "LV: Found an AND reduction PHI."<< *Phi <<"\n");
2444 if (AddReductionVar(Phi, RK_IntegerXor)) {
2445 DEBUG(dbgs() << "LV: Found a XOR reduction PHI."<< *Phi <<"\n");
2448 if (AddReductionVar(Phi, RK_IntegerMinMax)) {
2449 DEBUG(dbgs() << "LV: Found a MINMAX reduction PHI."<< *Phi <<"\n");
2452 if (AddReductionVar(Phi, RK_FloatMult)) {
2453 DEBUG(dbgs() << "LV: Found an FMult reduction PHI."<< *Phi <<"\n");
2456 if (AddReductionVar(Phi, RK_FloatAdd)) {
2457 DEBUG(dbgs() << "LV: Found an FAdd reduction PHI."<< *Phi <<"\n");
2461 DEBUG(dbgs() << "LV: Found an unidentified PHI."<< *Phi <<"\n");
2463 }// end of PHI handling
2465 // We still don't handle functions. However, we can ignore dbg intrinsic
2466 // calls and we do handle certain intrinsic and libm functions.
2467 CallInst *CI = dyn_cast<CallInst>(it);
2468 if (CI && !getIntrinsicIDForCall(CI, TLI) && !isa<DbgInfoIntrinsic>(CI)) {
2469 DEBUG(dbgs() << "LV: Found a call site.\n");
2473 // Check that the instruction return type is vectorizable.
2474 if (!VectorType::isValidElementType(it->getType()) &&
2475 !it->getType()->isVoidTy()) {
2476 DEBUG(dbgs() << "LV: Found unvectorizable type." << "\n");
2480 // Check that the stored type is vectorizable.
2481 if (StoreInst *ST = dyn_cast<StoreInst>(it)) {
2482 Type *T = ST->getValueOperand()->getType();
2483 if (!VectorType::isValidElementType(T))
2487 // Reduction instructions are allowed to have exit users.
2488 // All other instructions must not have external users.
2489 if (!AllowedExit.count(it))
2490 //Check that all of the users of the loop are inside the BB.
2491 for (Value::use_iterator I = it->use_begin(), E = it->use_end();
2493 Instruction *U = cast<Instruction>(*I);
2494 // This user may be a reduction exit value.
2495 if (!TheLoop->contains(U)) {
2496 DEBUG(dbgs() << "LV: Found an outside user for : "<< *U << "\n");
2505 DEBUG(dbgs() << "LV: Did not find one integer induction var.\n");
2506 assert(getInductionVars()->size() && "No induction variables");
2512 void LoopVectorizationLegality::collectLoopUniforms() {
2513 // We now know that the loop is vectorizable!
2514 // Collect variables that will remain uniform after vectorization.
2515 std::vector<Value*> Worklist;
2516 BasicBlock *Latch = TheLoop->getLoopLatch();
2518 // Start with the conditional branch and walk up the block.
2519 Worklist.push_back(Latch->getTerminator()->getOperand(0));
2521 while (Worklist.size()) {
2522 Instruction *I = dyn_cast<Instruction>(Worklist.back());
2523 Worklist.pop_back();
2525 // Look at instructions inside this loop.
2526 // Stop when reaching PHI nodes.
2527 // TODO: we need to follow values all over the loop, not only in this block.
2528 if (!I || !TheLoop->contains(I) || isa<PHINode>(I))
2531 // This is a known uniform.
2534 // Insert all operands.
2535 for (int i = 0, Op = I->getNumOperands(); i < Op; ++i) {
2536 Worklist.push_back(I->getOperand(i));
2541 AliasAnalysis::Location
2542 LoopVectorizationLegality::getLoadStoreLocation(Instruction *Inst) {
2543 if (StoreInst *Store = dyn_cast<StoreInst>(Inst))
2544 return AA->getLocation(Store);
2545 else if (LoadInst *Load = dyn_cast<LoadInst>(Inst))
2546 return AA->getLocation(Load);
2548 llvm_unreachable("Should be either load or store instruction");
2552 LoopVectorizationLegality::hasPossibleGlobalWriteReorder(
2555 AliasMultiMap& WriteObjects,
2556 unsigned MaxByteWidth) {
2558 AliasAnalysis::Location ThisLoc = getLoadStoreLocation(Inst);
2560 std::vector<Instruction*>::iterator
2561 it = WriteObjects[Object].begin(),
2562 end = WriteObjects[Object].end();
2564 for (; it != end; ++it) {
2565 Instruction* I = *it;
2569 AliasAnalysis::Location ThatLoc = getLoadStoreLocation(I);
2570 if (AA->alias(ThisLoc.getWithNewSize(MaxByteWidth),
2571 ThatLoc.getWithNewSize(MaxByteWidth)))
2577 bool LoopVectorizationLegality::canVectorizeMemory() {
2579 typedef SmallVector<Value*, 16> ValueVector;
2580 typedef SmallPtrSet<Value*, 16> ValueSet;
2581 // Holds the Load and Store *instructions*.
2584 PtrRtCheck.Pointers.clear();
2585 PtrRtCheck.Need = false;
2587 const bool IsAnnotatedParallel = TheLoop->isAnnotatedParallel();
2590 for (Loop::block_iterator bb = TheLoop->block_begin(),
2591 be = TheLoop->block_end(); bb != be; ++bb) {
2593 // Scan the BB and collect legal loads and stores.
2594 for (BasicBlock::iterator it = (*bb)->begin(), e = (*bb)->end(); it != e;
2597 // If this is a load, save it. If this instruction can read from memory
2598 // but is not a load, then we quit. Notice that we don't handle function
2599 // calls that read or write.
2600 if (it->mayReadFromMemory()) {
2601 LoadInst *Ld = dyn_cast<LoadInst>(it);
2602 if (!Ld) return false;
2603 if (!Ld->isSimple() && !IsAnnotatedParallel) {
2604 DEBUG(dbgs() << "LV: Found a non-simple load.\n");
2607 Loads.push_back(Ld);
2611 // Save 'store' instructions. Abort if other instructions write to memory.
2612 if (it->mayWriteToMemory()) {
2613 StoreInst *St = dyn_cast<StoreInst>(it);
2614 if (!St) return false;
2615 if (!St->isSimple() && !IsAnnotatedParallel) {
2616 DEBUG(dbgs() << "LV: Found a non-simple store.\n");
2619 Stores.push_back(St);
2624 // Now we have two lists that hold the loads and the stores.
2625 // Next, we find the pointers that they use.
2627 // Check if we see any stores. If there are no stores, then we don't
2628 // care if the pointers are *restrict*.
2629 if (!Stores.size()) {
2630 DEBUG(dbgs() << "LV: Found a read-only loop!\n");
2634 // Holds the read and read-write *pointers* that we find. These maps hold
2635 // unique values for pointers (so no need for multi-map).
2637 AliasMap ReadWrites;
2639 // Holds the analyzed pointers. We don't want to call GetUnderlyingObjects
2640 // multiple times on the same object. If the ptr is accessed twice, once
2641 // for read and once for write, it will only appear once (on the write
2642 // list). This is okay, since we are going to check for conflicts between
2643 // writes and between reads and writes, but not between reads and reads.
2646 ValueVector::iterator I, IE;
2647 for (I = Stores.begin(), IE = Stores.end(); I != IE; ++I) {
2648 StoreInst *ST = cast<StoreInst>(*I);
2649 Value* Ptr = ST->getPointerOperand();
2651 if (isUniform(Ptr)) {
2652 DEBUG(dbgs() << "LV: We don't allow storing to uniform addresses\n");
2656 // If we did *not* see this pointer before, insert it to
2657 // the read-write list. At this phase it is only a 'write' list.
2658 if (Seen.insert(Ptr))
2659 ReadWrites.insert(std::make_pair(Ptr, ST));
2662 if (IsAnnotatedParallel) {
2664 << "LV: A loop annotated parallel, ignore memory dependency "
2669 for (I = Loads.begin(), IE = Loads.end(); I != IE; ++I) {
2670 LoadInst *LD = cast<LoadInst>(*I);
2671 Value* Ptr = LD->getPointerOperand();
2672 // If we did *not* see this pointer before, insert it to the
2673 // read list. If we *did* see it before, then it is already in
2674 // the read-write list. This allows us to vectorize expressions
2675 // such as A[i] += x; Because the address of A[i] is a read-write
2676 // pointer. This only works if the index of A[i] is consecutive.
2677 // If the address of i is unknown (for example A[B[i]]) then we may
2678 // read a few words, modify, and write a few words, and some of the
2679 // words may be written to the same address.
2680 if (Seen.insert(Ptr) || 0 == isConsecutivePtr(Ptr))
2681 Reads.insert(std::make_pair(Ptr, LD));
2684 // If we write (or read-write) to a single destination and there are no
2685 // other reads in this loop then is it safe to vectorize.
2686 if (ReadWrites.size() == 1 && Reads.size() == 0) {
2687 DEBUG(dbgs() << "LV: Found a write-only loop!\n");
2691 unsigned NumReadPtrs = 0;
2692 unsigned NumWritePtrs = 0;
2694 // Find pointers with computable bounds. We are going to use this information
2695 // to place a runtime bound check.
2696 bool CanDoRT = true;
2697 AliasMap::iterator MI, ME;
2698 for (MI = ReadWrites.begin(), ME = ReadWrites.end(); MI != ME; ++MI) {
2699 Value *V = (*MI).first;
2700 if (hasComputableBounds(V)) {
2701 PtrRtCheck.insert(SE, TheLoop, V, true);
2703 DEBUG(dbgs() << "LV: Found a runtime check ptr:" << *V <<"\n");
2709 for (MI = Reads.begin(), ME = Reads.end(); MI != ME; ++MI) {
2710 Value *V = (*MI).first;
2711 if (hasComputableBounds(V)) {
2712 PtrRtCheck.insert(SE, TheLoop, V, false);
2714 DEBUG(dbgs() << "LV: Found a runtime check ptr:" << *V <<"\n");
2721 // Check that we did not collect too many pointers or found a
2722 // unsizeable pointer.
2723 unsigned NumComparisons = (NumWritePtrs * (NumReadPtrs + NumWritePtrs - 1));
2724 DEBUG(dbgs() << "LV: We need to compare " << NumComparisons << " ptrs.\n");
2725 if (!CanDoRT || NumComparisons > RuntimeMemoryCheckThreshold) {
2731 DEBUG(dbgs() << "LV: We can perform a memory runtime check if needed.\n");
2734 bool NeedRTCheck = false;
2736 // Biggest vectorized access possible, vector width * unroll factor.
2737 // TODO: We're being very pessimistic here, find a way to know the
2738 // real access width before getting here.
2739 unsigned MaxByteWidth = (TTI->getRegisterBitWidth(true) / 8) *
2740 TTI->getMaximumUnrollFactor();
2741 // Now that the pointers are in two lists (Reads and ReadWrites), we
2742 // can check that there are no conflicts between each of the writes and
2743 // between the writes to the reads.
2744 // Note that WriteObjects duplicates the stores (indexed now by underlying
2745 // objects) to avoid pointing to elements inside ReadWrites.
2746 // TODO: Maybe create a new type where they can interact without duplication.
2747 AliasMultiMap WriteObjects;
2748 ValueVector TempObjects;
2750 // Check that the read-writes do not conflict with other read-write
2752 bool AllWritesIdentified = true;
2753 for (MI = ReadWrites.begin(), ME = ReadWrites.end(); MI != ME; ++MI) {
2754 Value *Val = (*MI).first;
2755 Instruction *Inst = (*MI).second;
2757 GetUnderlyingObjects(Val, TempObjects, DL);
2758 for (ValueVector::iterator UI=TempObjects.begin(), UE=TempObjects.end();
2760 if (!isIdentifiedObject(*UI)) {
2761 DEBUG(dbgs() << "LV: Found an unidentified write ptr:"<< **UI <<"\n");
2763 AllWritesIdentified = false;
2766 // Never seen it before, can't alias.
2767 if (WriteObjects[*UI].empty()) {
2768 DEBUG(dbgs() << "LV: Adding Underlying value:" << **UI <<"\n");
2769 WriteObjects[*UI].push_back(Inst);
2772 // Direct alias found.
2773 if (!AA || dyn_cast<GlobalValue>(*UI) == NULL) {
2774 DEBUG(dbgs() << "LV: Found a possible write-write reorder:"
2778 DEBUG(dbgs() << "LV: Found a conflicting global value:"
2780 DEBUG(dbgs() << "LV: While examining store:" << *Inst <<"\n");
2781 DEBUG(dbgs() << "LV: On value:" << *Val <<"\n");
2783 // If global alias, make sure they do alias.
2784 if (hasPossibleGlobalWriteReorder(*UI,
2788 DEBUG(dbgs() << "LV: Found a possible write-write reorder:"
2793 // Didn't alias, insert into map for further reference.
2794 WriteObjects[*UI].push_back(Inst);
2796 TempObjects.clear();
2799 /// Check that the reads don't conflict with the read-writes.
2800 for (MI = Reads.begin(), ME = Reads.end(); MI != ME; ++MI) {
2801 Value *Val = (*MI).first;
2802 GetUnderlyingObjects(Val, TempObjects, DL);
2803 for (ValueVector::iterator UI=TempObjects.begin(), UE=TempObjects.end();
2805 // If all of the writes are identified then we don't care if the read
2806 // pointer is identified or not.
2807 if (!AllWritesIdentified && !isIdentifiedObject(*UI)) {
2808 DEBUG(dbgs() << "LV: Found an unidentified read ptr:"<< **UI <<"\n");
2812 // Never seen it before, can't alias.
2813 if (WriteObjects[*UI].empty())
2815 // Direct alias found.
2816 if (!AA || dyn_cast<GlobalValue>(*UI) == NULL) {
2817 DEBUG(dbgs() << "LV: Found a possible write-write reorder:"
2821 DEBUG(dbgs() << "LV: Found a global value: "
2823 Instruction *Inst = (*MI).second;
2824 DEBUG(dbgs() << "LV: While examining load:" << *Inst <<"\n");
2825 DEBUG(dbgs() << "LV: On value:" << *Val <<"\n");
2827 // If global alias, make sure they do alias.
2828 if (hasPossibleGlobalWriteReorder(*UI,
2832 DEBUG(dbgs() << "LV: Found a possible read-write reorder:"
2837 TempObjects.clear();
2840 PtrRtCheck.Need = NeedRTCheck;
2841 if (NeedRTCheck && !CanDoRT) {
2842 DEBUG(dbgs() << "LV: We can't vectorize because we can't find " <<
2843 "the array bounds.\n");
2848 DEBUG(dbgs() << "LV: We "<< (NeedRTCheck ? "" : "don't") <<
2849 " need a runtime memory check.\n");
2853 bool LoopVectorizationLegality::AddReductionVar(PHINode *Phi,
2854 ReductionKind Kind) {
2855 if (Phi->getNumIncomingValues() != 2)
2858 // Reduction variables are only found in the loop header block.
2859 if (Phi->getParent() != TheLoop->getHeader())
2862 // Obtain the reduction start value from the value that comes from the loop
2864 Value *RdxStart = Phi->getIncomingValueForBlock(TheLoop->getLoopPreheader());
2866 // ExitInstruction is the single value which is used outside the loop.
2867 // We only allow for a single reduction value to be used outside the loop.
2868 // This includes users of the reduction, variables (which form a cycle
2869 // which ends in the phi node).
2870 Instruction *ExitInstruction = 0;
2871 // Indicates that we found a binary operation in our scan.
2872 bool FoundBinOp = false;
2874 // Iter is our iterator. We start with the PHI node and scan for all of the
2875 // users of this instruction. All users must be instructions that can be
2876 // used as reduction variables (such as ADD). We may have a single
2877 // out-of-block user. The cycle must end with the original PHI.
2878 Instruction *Iter = Phi;
2880 // To recognize min/max patterns formed by a icmp select sequence, we store
2881 // the number of instruction we saw from the recognized min/max pattern,
2882 // such that we don't stop when we see the phi has two uses (one by the select
2883 // and one by the icmp) and to make sure we only see exactly the two
2885 unsigned NumICmpSelectPatternInst = 0;
2886 ReductionInstDesc ReduxDesc(false, 0);
2888 // Avoid cycles in the chain.
2889 SmallPtrSet<Instruction *, 8> VisitedInsts;
2890 while (VisitedInsts.insert(Iter)) {
2891 // If the instruction has no users then this is a broken
2892 // chain and can't be a reduction variable.
2893 if (Iter->use_empty())
2896 // Did we find a user inside this loop already ?
2897 bool FoundInBlockUser = false;
2898 // Did we reach the initial PHI node already ?
2899 bool FoundStartPHI = false;
2901 // Is this a bin op ?
2902 FoundBinOp |= !isa<PHINode>(Iter);
2904 // For each of the *users* of iter.
2905 for (Value::use_iterator it = Iter->use_begin(), e = Iter->use_end();
2907 Instruction *U = cast<Instruction>(*it);
2908 // We already know that the PHI is a user.
2910 FoundStartPHI = true;
2914 // Check if we found the exit user.
2915 BasicBlock *Parent = U->getParent();
2916 if (!TheLoop->contains(Parent)) {
2917 // Exit if you find multiple outside users.
2918 if (ExitInstruction != 0)
2920 ExitInstruction = Iter;
2923 // We allow in-loop PHINodes which are not the original reduction PHI
2924 // node. If this PHI is the only user of Iter (happens in IF w/ no ELSE
2925 // structure) then don't skip this PHI.
2926 if (isa<PHINode>(Iter) && isa<PHINode>(U) &&
2927 U->getParent() != TheLoop->getHeader() &&
2928 TheLoop->contains(U) &&
2929 Iter->hasNUsesOrMore(2))
2932 // We can't have multiple inside users except for a combination of
2933 // icmp/select both using the phi.
2934 if (FoundInBlockUser && !NumICmpSelectPatternInst)
2936 FoundInBlockUser = true;
2938 // Any reduction instr must be of one of the allowed kinds.
2939 ReduxDesc = isReductionInstr(U, Kind, ReduxDesc);
2940 if (!ReduxDesc.IsReduction)
2943 if (Kind == RK_IntegerMinMax && (isa<ICmpInst>(U) ||
2944 isa<SelectInst>(U)))
2945 ++NumICmpSelectPatternInst;
2947 // Reductions of instructions such as Div, and Sub is only
2948 // possible if the LHS is the reduction variable.
2949 if (!U->isCommutative() && !isa<PHINode>(U) && !isa<SelectInst>(U) &&
2950 !isa<ICmpInst>(U) && U->getOperand(0) != Iter)
2953 Iter = ReduxDesc.PatternLastInst;
2956 // This means we have seen one but not the other instruction of the
2957 // pattern or more than just a select and cmp.
2958 if (Kind == RK_IntegerMinMax && NumICmpSelectPatternInst != 2)
2961 // We found a reduction var if we have reached the original
2962 // phi node and we only have a single instruction with out-of-loop
2964 if (FoundStartPHI) {
2965 // This instruction is allowed to have out-of-loop users.
2966 AllowedExit.insert(ExitInstruction);
2968 // Save the description of this reduction variable.
2969 ReductionDescriptor RD(RdxStart, ExitInstruction, Kind,
2970 ReduxDesc.MinMaxKind);
2971 Reductions[Phi] = RD;
2972 // We've ended the cycle. This is a reduction variable if we have an
2973 // outside user and it has a binary op.
2974 return FoundBinOp && ExitInstruction;
2981 /// Returns true if the instruction is a Select(ICmp(X, Y), X, Y) instruction
2982 /// pattern corresponding to a min(X, Y) or max(X, Y).
2983 LoopVectorizationLegality::ReductionInstDesc
2984 LoopVectorizationLegality::isMinMaxSelectCmpPattern(Instruction *I, ReductionInstDesc &Prev) {
2986 assert((isa<ICmpInst>(I) || isa<SelectInst>(I)) &&
2987 "Expect a select instruction");
2989 SelectInst *Select = 0;
2991 // We must handle the select(cmp()) as a single instruction. Advance to the
2993 if ((Cmp = dyn_cast<ICmpInst>(I))) {
2994 if (!Cmp->hasOneUse() || !(Select = dyn_cast<SelectInst>(*I->use_begin())))
2995 return ReductionInstDesc(false, I);
2996 return ReductionInstDesc(Select, Prev.MinMaxKind);
2999 // Only handle single use cases for now.
3000 if (!(Select = dyn_cast<SelectInst>(I)))
3001 return ReductionInstDesc(false, I);
3002 if (!(Cmp = dyn_cast<ICmpInst>(I->getOperand(0))))
3003 return ReductionInstDesc(false, I);
3004 if (!Cmp->hasOneUse())
3005 return ReductionInstDesc(false, I);
3007 Value *CmpLeft = Cmp->getOperand(0);
3008 Value *CmpRight = Cmp->getOperand(1);
3010 // Look for a min/max pattern.
3011 if (m_UMin(m_Value(CmpLeft), m_Value(CmpRight)).match(Select))
3012 return ReductionInstDesc(Select, MRK_UIntMin);
3013 else if (m_UMax(m_Value(CmpLeft), m_Value(CmpRight)).match(Select))
3014 return ReductionInstDesc(Select, MRK_UIntMax);
3015 else if (m_SMax(m_Value(CmpLeft), m_Value(CmpRight)).match(Select))
3016 return ReductionInstDesc(Select, MRK_SIntMax);
3017 else if (m_SMin(m_Value(CmpLeft), m_Value(CmpRight)).match(Select))
3018 return ReductionInstDesc(Select, MRK_SIntMin);
3020 return ReductionInstDesc(false, I);
3023 LoopVectorizationLegality::ReductionInstDesc
3024 LoopVectorizationLegality::isReductionInstr(Instruction *I,
3026 ReductionInstDesc &Prev) {
3027 bool FP = I->getType()->isFloatingPointTy();
3028 bool FastMath = (FP && I->isCommutative() && I->isAssociative());
3029 switch (I->getOpcode()) {
3031 return ReductionInstDesc(false, I);
3032 case Instruction::PHI:
3033 if (FP && (Kind != RK_FloatMult && Kind != RK_FloatAdd))
3034 return ReductionInstDesc(false, I);
3035 return ReductionInstDesc(I, Prev.MinMaxKind);
3036 case Instruction::Sub:
3037 case Instruction::Add:
3038 return ReductionInstDesc(Kind == RK_IntegerAdd, I);
3039 case Instruction::Mul:
3040 return ReductionInstDesc(Kind == RK_IntegerMult, I);
3041 case Instruction::And:
3042 return ReductionInstDesc(Kind == RK_IntegerAnd, I);
3043 case Instruction::Or:
3044 return ReductionInstDesc(Kind == RK_IntegerOr, I);
3045 case Instruction::Xor:
3046 return ReductionInstDesc(Kind == RK_IntegerXor, I);
3047 case Instruction::FMul:
3048 return ReductionInstDesc(Kind == RK_FloatMult && FastMath, I);
3049 case Instruction::FAdd:
3050 return ReductionInstDesc(Kind == RK_FloatAdd && FastMath, I);
3051 case Instruction::ICmp:
3052 case Instruction::Select:
3053 if (Kind != RK_IntegerMinMax)
3054 return ReductionInstDesc(false, I);
3055 return isMinMaxSelectCmpPattern(I, Prev);
3059 LoopVectorizationLegality::InductionKind
3060 LoopVectorizationLegality::isInductionVariable(PHINode *Phi) {
3061 Type *PhiTy = Phi->getType();
3062 // We only handle integer and pointer inductions variables.
3063 if (!PhiTy->isIntegerTy() && !PhiTy->isPointerTy())
3064 return IK_NoInduction;
3066 // Check that the PHI is consecutive.
3067 const SCEV *PhiScev = SE->getSCEV(Phi);
3068 const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(PhiScev);
3070 DEBUG(dbgs() << "LV: PHI is not a poly recurrence.\n");
3071 return IK_NoInduction;
3073 const SCEV *Step = AR->getStepRecurrence(*SE);
3075 // Integer inductions need to have a stride of one.
3076 if (PhiTy->isIntegerTy()) {
3078 return IK_IntInduction;
3079 if (Step->isAllOnesValue())
3080 return IK_ReverseIntInduction;
3081 return IK_NoInduction;
3084 // Calculate the pointer stride and check if it is consecutive.
3085 const SCEVConstant *C = dyn_cast<SCEVConstant>(Step);
3087 return IK_NoInduction;
3089 assert(PhiTy->isPointerTy() && "The PHI must be a pointer");
3090 uint64_t Size = DL->getTypeAllocSize(PhiTy->getPointerElementType());
3091 if (C->getValue()->equalsInt(Size))
3092 return IK_PtrInduction;
3093 else if (C->getValue()->equalsInt(0 - Size))
3094 return IK_ReversePtrInduction;
3096 return IK_NoInduction;
3099 bool LoopVectorizationLegality::isInductionVariable(const Value *V) {
3100 Value *In0 = const_cast<Value*>(V);
3101 PHINode *PN = dyn_cast_or_null<PHINode>(In0);
3105 return Inductions.count(PN);
3108 bool LoopVectorizationLegality::blockNeedsPredication(BasicBlock *BB) {
3109 assert(TheLoop->contains(BB) && "Unknown block used");
3111 // Blocks that do not dominate the latch need predication.
3112 BasicBlock* Latch = TheLoop->getLoopLatch();
3113 return !DT->dominates(BB, Latch);
3116 bool LoopVectorizationLegality::blockCanBePredicated(BasicBlock *BB) {
3117 for (BasicBlock::iterator it = BB->begin(), e = BB->end(); it != e; ++it) {
3118 // We don't predicate loads/stores at the moment.
3119 if (it->mayReadFromMemory() || it->mayWriteToMemory() || it->mayThrow())
3122 // The instructions below can trap.
3123 switch (it->getOpcode()) {
3125 case Instruction::UDiv:
3126 case Instruction::SDiv:
3127 case Instruction::URem:
3128 case Instruction::SRem:
3136 bool LoopVectorizationLegality::hasComputableBounds(Value *Ptr) {
3137 const SCEV *PhiScev = SE->getSCEV(Ptr);
3138 const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(PhiScev);
3142 return AR->isAffine();
3145 LoopVectorizationCostModel::VectorizationFactor
3146 LoopVectorizationCostModel::selectVectorizationFactor(bool OptForSize,
3148 // Width 1 means no vectorize
3149 VectorizationFactor Factor = { 1U, 0U };
3150 if (OptForSize && Legal->getRuntimePointerCheck()->Need) {
3151 DEBUG(dbgs() << "LV: Aborting. Runtime ptr check is required in Os.\n");
3155 // Find the trip count.
3156 unsigned TC = SE->getSmallConstantTripCount(TheLoop, TheLoop->getLoopLatch());
3157 DEBUG(dbgs() << "LV: Found trip count:"<<TC<<"\n");
3159 unsigned WidestType = getWidestType();
3160 unsigned WidestRegister = TTI.getRegisterBitWidth(true);
3161 unsigned MaxVectorSize = WidestRegister / WidestType;
3162 DEBUG(dbgs() << "LV: The Widest type: " << WidestType << " bits.\n");
3163 DEBUG(dbgs() << "LV: The Widest register is:" << WidestRegister << "bits.\n");
3165 if (MaxVectorSize == 0) {
3166 DEBUG(dbgs() << "LV: The target has no vector registers.\n");
3170 assert(MaxVectorSize <= 32 && "Did not expect to pack so many elements"
3171 " into one vector!");
3173 unsigned VF = MaxVectorSize;
3175 // If we optimize the program for size, avoid creating the tail loop.
3177 // If we are unable to calculate the trip count then don't try to vectorize.
3179 DEBUG(dbgs() << "LV: Aborting. A tail loop is required in Os.\n");
3183 // Find the maximum SIMD width that can fit within the trip count.
3184 VF = TC % MaxVectorSize;
3189 // If the trip count that we found modulo the vectorization factor is not
3190 // zero then we require a tail.
3192 DEBUG(dbgs() << "LV: Aborting. A tail loop is required in Os.\n");
3198 assert(isPowerOf2_32(UserVF) && "VF needs to be a power of two");
3199 DEBUG(dbgs() << "LV: Using user VF "<<UserVF<<".\n");
3201 Factor.Width = UserVF;
3205 float Cost = expectedCost(1);
3207 DEBUG(dbgs() << "LV: Scalar loop costs: "<< (int)Cost << ".\n");
3208 for (unsigned i=2; i <= VF; i*=2) {
3209 // Notice that the vector loop needs to be executed less times, so
3210 // we need to divide the cost of the vector loops by the width of
3211 // the vector elements.
3212 float VectorCost = expectedCost(i) / (float)i;
3213 DEBUG(dbgs() << "LV: Vector loop of width "<< i << " costs: " <<
3214 (int)VectorCost << ".\n");
3215 if (VectorCost < Cost) {
3221 DEBUG(dbgs() << "LV: Selecting VF = : "<< Width << ".\n");
3222 Factor.Width = Width;
3223 Factor.Cost = Width * Cost;
3227 unsigned LoopVectorizationCostModel::getWidestType() {
3228 unsigned MaxWidth = 8;
3231 for (Loop::block_iterator bb = TheLoop->block_begin(),
3232 be = TheLoop->block_end(); bb != be; ++bb) {
3233 BasicBlock *BB = *bb;
3235 // For each instruction in the loop.
3236 for (BasicBlock::iterator it = BB->begin(), e = BB->end(); it != e; ++it) {
3237 Type *T = it->getType();
3239 // Only examine Loads, Stores and PHINodes.
3240 if (!isa<LoadInst>(it) && !isa<StoreInst>(it) && !isa<PHINode>(it))
3243 // Examine PHI nodes that are reduction variables.
3244 if (PHINode *PN = dyn_cast<PHINode>(it))
3245 if (!Legal->getReductionVars()->count(PN))
3248 // Examine the stored values.
3249 if (StoreInst *ST = dyn_cast<StoreInst>(it))
3250 T = ST->getValueOperand()->getType();
3252 // Ignore loaded pointer types and stored pointer types that are not
3253 // consecutive. However, we do want to take consecutive stores/loads of
3254 // pointer vectors into account.
3255 if (T->isPointerTy() && !isConsecutiveLoadOrStore(it))
3258 MaxWidth = std::max(MaxWidth,
3259 (unsigned)DL->getTypeSizeInBits(T->getScalarType()));
3267 LoopVectorizationCostModel::selectUnrollFactor(bool OptForSize,
3270 unsigned LoopCost) {
3272 // -- The unroll heuristics --
3273 // We unroll the loop in order to expose ILP and reduce the loop overhead.
3274 // There are many micro-architectural considerations that we can't predict
3275 // at this level. For example frontend pressure (on decode or fetch) due to
3276 // code size, or the number and capabilities of the execution ports.
3278 // We use the following heuristics to select the unroll factor:
3279 // 1. If the code has reductions the we unroll in order to break the cross
3280 // iteration dependency.
3281 // 2. If the loop is really small then we unroll in order to reduce the loop
3283 // 3. We don't unroll if we think that we will spill registers to memory due
3284 // to the increased register pressure.
3286 // Use the user preference, unless 'auto' is selected.
3290 // When we optimize for size we don't unroll.
3294 // Do not unroll loops with a relatively small trip count.
3295 unsigned TC = SE->getSmallConstantTripCount(TheLoop,
3296 TheLoop->getLoopLatch());
3297 if (TC > 1 && TC < TinyTripCountUnrollThreshold)
3300 unsigned TargetVectorRegisters = TTI.getNumberOfRegisters(true);
3301 DEBUG(dbgs() << "LV: The target has " << TargetVectorRegisters <<
3302 " vector registers\n");
3304 LoopVectorizationCostModel::RegisterUsage R = calculateRegisterUsage();
3305 // We divide by these constants so assume that we have at least one
3306 // instruction that uses at least one register.
3307 R.MaxLocalUsers = std::max(R.MaxLocalUsers, 1U);
3308 R.NumInstructions = std::max(R.NumInstructions, 1U);
3310 // We calculate the unroll factor using the following formula.
3311 // Subtract the number of loop invariants from the number of available
3312 // registers. These registers are used by all of the unrolled instances.
3313 // Next, divide the remaining registers by the number of registers that is
3314 // required by the loop, in order to estimate how many parallel instances
3315 // fit without causing spills.
3316 unsigned UF = (TargetVectorRegisters - R.LoopInvariantRegs) / R.MaxLocalUsers;
3318 // Clamp the unroll factor ranges to reasonable factors.
3319 unsigned MaxUnrollSize = TTI.getMaximumUnrollFactor();
3321 // If we did not calculate the cost for VF (because the user selected the VF)
3322 // then we calculate the cost of VF here.
3324 LoopCost = expectedCost(VF);
3326 // Clamp the calculated UF to be between the 1 and the max unroll factor
3327 // that the target allows.
3328 if (UF > MaxUnrollSize)
3333 if (Legal->getReductionVars()->size()) {
3334 DEBUG(dbgs() << "LV: Unrolling because of reductions. \n");
3338 // We want to unroll tiny loops in order to reduce the loop overhead.
3339 // We assume that the cost overhead is 1 and we use the cost model
3340 // to estimate the cost of the loop and unroll until the cost of the
3341 // loop overhead is about 5% of the cost of the loop.
3342 DEBUG(dbgs() << "LV: Loop cost is "<< LoopCost <<" \n");
3343 if (LoopCost < 20) {
3344 DEBUG(dbgs() << "LV: Unrolling to reduce branch cost. \n");
3345 unsigned NewUF = 20/LoopCost + 1;
3346 return std::min(NewUF, UF);
3349 DEBUG(dbgs() << "LV: Not Unrolling. \n");
3353 LoopVectorizationCostModel::RegisterUsage
3354 LoopVectorizationCostModel::calculateRegisterUsage() {
3355 // This function calculates the register usage by measuring the highest number
3356 // of values that are alive at a single location. Obviously, this is a very
3357 // rough estimation. We scan the loop in a topological order in order and
3358 // assign a number to each instruction. We use RPO to ensure that defs are
3359 // met before their users. We assume that each instruction that has in-loop
3360 // users starts an interval. We record every time that an in-loop value is
3361 // used, so we have a list of the first and last occurrences of each
3362 // instruction. Next, we transpose this data structure into a multi map that
3363 // holds the list of intervals that *end* at a specific location. This multi
3364 // map allows us to perform a linear search. We scan the instructions linearly
3365 // and record each time that a new interval starts, by placing it in a set.
3366 // If we find this value in the multi-map then we remove it from the set.
3367 // The max register usage is the maximum size of the set.
3368 // We also search for instructions that are defined outside the loop, but are
3369 // used inside the loop. We need this number separately from the max-interval
3370 // usage number because when we unroll, loop-invariant values do not take
3372 LoopBlocksDFS DFS(TheLoop);
3376 R.NumInstructions = 0;
3378 // Each 'key' in the map opens a new interval. The values
3379 // of the map are the index of the 'last seen' usage of the
3380 // instruction that is the key.
3381 typedef DenseMap<Instruction*, unsigned> IntervalMap;
3382 // Maps instruction to its index.
3383 DenseMap<unsigned, Instruction*> IdxToInstr;
3384 // Marks the end of each interval.
3385 IntervalMap EndPoint;
3386 // Saves the list of instruction indices that are used in the loop.
3387 SmallSet<Instruction*, 8> Ends;
3388 // Saves the list of values that are used in the loop but are
3389 // defined outside the loop, such as arguments and constants.
3390 SmallPtrSet<Value*, 8> LoopInvariants;
3393 for (LoopBlocksDFS::RPOIterator bb = DFS.beginRPO(),
3394 be = DFS.endRPO(); bb != be; ++bb) {
3395 R.NumInstructions += (*bb)->size();
3396 for (BasicBlock::iterator it = (*bb)->begin(), e = (*bb)->end(); it != e;
3398 Instruction *I = it;
3399 IdxToInstr[Index++] = I;
3401 // Save the end location of each USE.
3402 for (unsigned i = 0; i < I->getNumOperands(); ++i) {
3403 Value *U = I->getOperand(i);
3404 Instruction *Instr = dyn_cast<Instruction>(U);
3406 // Ignore non-instruction values such as arguments, constants, etc.
3407 if (!Instr) continue;
3409 // If this instruction is outside the loop then record it and continue.
3410 if (!TheLoop->contains(Instr)) {
3411 LoopInvariants.insert(Instr);
3415 // Overwrite previous end points.
3416 EndPoint[Instr] = Index;
3422 // Saves the list of intervals that end with the index in 'key'.
3423 typedef SmallVector<Instruction*, 2> InstrList;
3424 DenseMap<unsigned, InstrList> TransposeEnds;
3426 // Transpose the EndPoints to a list of values that end at each index.
3427 for (IntervalMap::iterator it = EndPoint.begin(), e = EndPoint.end();
3429 TransposeEnds[it->second].push_back(it->first);
3431 SmallSet<Instruction*, 8> OpenIntervals;
3432 unsigned MaxUsage = 0;
3435 DEBUG(dbgs() << "LV(REG): Calculating max register usage:\n");
3436 for (unsigned int i = 0; i < Index; ++i) {
3437 Instruction *I = IdxToInstr[i];
3438 // Ignore instructions that are never used within the loop.
3439 if (!Ends.count(I)) continue;
3441 // Remove all of the instructions that end at this location.
3442 InstrList &List = TransposeEnds[i];
3443 for (unsigned int j=0, e = List.size(); j < e; ++j)
3444 OpenIntervals.erase(List[j]);
3446 // Count the number of live interals.
3447 MaxUsage = std::max(MaxUsage, OpenIntervals.size());
3449 DEBUG(dbgs() << "LV(REG): At #" << i << " Interval # " <<
3450 OpenIntervals.size() <<"\n");
3452 // Add the current instruction to the list of open intervals.
3453 OpenIntervals.insert(I);
3456 unsigned Invariant = LoopInvariants.size();
3457 DEBUG(dbgs() << "LV(REG): Found max usage: " << MaxUsage << " \n");
3458 DEBUG(dbgs() << "LV(REG): Found invariant usage: " << Invariant << " \n");
3459 DEBUG(dbgs() << "LV(REG): LoopSize: " << R.NumInstructions << " \n");
3461 R.LoopInvariantRegs = Invariant;
3462 R.MaxLocalUsers = MaxUsage;
3466 unsigned LoopVectorizationCostModel::expectedCost(unsigned VF) {
3470 for (Loop::block_iterator bb = TheLoop->block_begin(),
3471 be = TheLoop->block_end(); bb != be; ++bb) {
3472 unsigned BlockCost = 0;
3473 BasicBlock *BB = *bb;
3475 // For each instruction in the old loop.
3476 for (BasicBlock::iterator it = BB->begin(), e = BB->end(); it != e; ++it) {
3477 // Skip dbg intrinsics.
3478 if (isa<DbgInfoIntrinsic>(it))
3481 unsigned C = getInstructionCost(it, VF);
3483 DEBUG(dbgs() << "LV: Found an estimated cost of "<< C <<" for VF " <<
3484 VF << " For instruction: "<< *it << "\n");
3487 // We assume that if-converted blocks have a 50% chance of being executed.
3488 // When the code is scalar then some of the blocks are avoided due to CF.
3489 // When the code is vectorized we execute all code paths.
3490 if (Legal->blockNeedsPredication(*bb) && VF == 1)
3500 LoopVectorizationCostModel::getInstructionCost(Instruction *I, unsigned VF) {
3501 // If we know that this instruction will remain uniform, check the cost of
3502 // the scalar version.
3503 if (Legal->isUniformAfterVectorization(I))
3506 Type *RetTy = I->getType();
3507 Type *VectorTy = ToVectorTy(RetTy, VF);
3509 // TODO: We need to estimate the cost of intrinsic calls.
3510 switch (I->getOpcode()) {
3511 case Instruction::GetElementPtr:
3512 // We mark this instruction as zero-cost because the cost of GEPs in
3513 // vectorized code depends on whether the corresponding memory instruction
3514 // is scalarized or not. Therefore, we handle GEPs with the memory
3515 // instruction cost.
3517 case Instruction::Br: {
3518 return TTI.getCFInstrCost(I->getOpcode());
3520 case Instruction::PHI:
3521 //TODO: IF-converted IFs become selects.
3523 case Instruction::Add:
3524 case Instruction::FAdd:
3525 case Instruction::Sub:
3526 case Instruction::FSub:
3527 case Instruction::Mul:
3528 case Instruction::FMul:
3529 case Instruction::UDiv:
3530 case Instruction::SDiv:
3531 case Instruction::FDiv:
3532 case Instruction::URem:
3533 case Instruction::SRem:
3534 case Instruction::FRem:
3535 case Instruction::Shl:
3536 case Instruction::LShr:
3537 case Instruction::AShr:
3538 case Instruction::And:
3539 case Instruction::Or:
3540 case Instruction::Xor: {
3541 // Certain instructions can be cheaper to vectorize if they have a constant
3542 // second vector operand. One example of this are shifts on x86.
3543 TargetTransformInfo::OperandValueKind Op1VK =
3544 TargetTransformInfo::OK_AnyValue;
3545 TargetTransformInfo::OperandValueKind Op2VK =
3546 TargetTransformInfo::OK_AnyValue;
3548 if (isa<ConstantInt>(I->getOperand(1)))
3549 Op2VK = TargetTransformInfo::OK_UniformConstantValue;
3551 return TTI.getArithmeticInstrCost(I->getOpcode(), VectorTy, Op1VK, Op2VK);
3553 case Instruction::Select: {
3554 SelectInst *SI = cast<SelectInst>(I);
3555 const SCEV *CondSCEV = SE->getSCEV(SI->getCondition());
3556 bool ScalarCond = (SE->isLoopInvariant(CondSCEV, TheLoop));
3557 Type *CondTy = SI->getCondition()->getType();
3559 CondTy = VectorType::get(CondTy, VF);
3561 return TTI.getCmpSelInstrCost(I->getOpcode(), VectorTy, CondTy);
3563 case Instruction::ICmp:
3564 case Instruction::FCmp: {
3565 Type *ValTy = I->getOperand(0)->getType();
3566 VectorTy = ToVectorTy(ValTy, VF);
3567 return TTI.getCmpSelInstrCost(I->getOpcode(), VectorTy);
3569 case Instruction::Store:
3570 case Instruction::Load: {
3571 StoreInst *SI = dyn_cast<StoreInst>(I);
3572 LoadInst *LI = dyn_cast<LoadInst>(I);
3573 Type *ValTy = (SI ? SI->getValueOperand()->getType() :
3575 VectorTy = ToVectorTy(ValTy, VF);
3577 unsigned Alignment = SI ? SI->getAlignment() : LI->getAlignment();
3578 unsigned AS = SI ? SI->getPointerAddressSpace() :
3579 LI->getPointerAddressSpace();
3580 Value *Ptr = SI ? SI->getPointerOperand() : LI->getPointerOperand();
3581 // We add the cost of address computation here instead of with the gep
3582 // instruction because only here we know whether the operation is
3585 return TTI.getAddressComputationCost(VectorTy) +
3586 TTI.getMemoryOpCost(I->getOpcode(), VectorTy, Alignment, AS);
3588 // Scalarized loads/stores.
3589 int ConsecutiveStride = Legal->isConsecutivePtr(Ptr);
3590 bool Reverse = ConsecutiveStride < 0;
3591 unsigned ScalarAllocatedSize = DL->getTypeAllocSize(ValTy);
3592 unsigned VectorElementSize = DL->getTypeStoreSize(VectorTy)/VF;
3593 if (!ConsecutiveStride || ScalarAllocatedSize != VectorElementSize) {
3595 // The cost of extracting from the value vector and pointer vector.
3596 Type *PtrTy = ToVectorTy(Ptr->getType(), VF);
3597 for (unsigned i = 0; i < VF; ++i) {
3598 // The cost of extracting the pointer operand.
3599 Cost += TTI.getVectorInstrCost(Instruction::ExtractElement, PtrTy, i);
3600 // In case of STORE, the cost of ExtractElement from the vector.
3601 // In case of LOAD, the cost of InsertElement into the returned
3603 Cost += TTI.getVectorInstrCost(SI ? Instruction::ExtractElement :
3604 Instruction::InsertElement,
3608 // The cost of the scalar loads/stores.
3609 Cost += VF * TTI.getAddressComputationCost(ValTy->getScalarType());
3610 Cost += VF * TTI.getMemoryOpCost(I->getOpcode(), ValTy->getScalarType(),
3615 // Wide load/stores.
3616 unsigned Cost = TTI.getAddressComputationCost(VectorTy);
3617 Cost += TTI.getMemoryOpCost(I->getOpcode(), VectorTy, Alignment, AS);
3620 Cost += TTI.getShuffleCost(TargetTransformInfo::SK_Reverse,
3624 case Instruction::ZExt:
3625 case Instruction::SExt:
3626 case Instruction::FPToUI:
3627 case Instruction::FPToSI:
3628 case Instruction::FPExt:
3629 case Instruction::PtrToInt:
3630 case Instruction::IntToPtr:
3631 case Instruction::SIToFP:
3632 case Instruction::UIToFP:
3633 case Instruction::Trunc:
3634 case Instruction::FPTrunc:
3635 case Instruction::BitCast: {
3636 // We optimize the truncation of induction variable.
3637 // The cost of these is the same as the scalar operation.
3638 if (I->getOpcode() == Instruction::Trunc &&
3639 Legal->isInductionVariable(I->getOperand(0)))
3640 return TTI.getCastInstrCost(I->getOpcode(), I->getType(),
3641 I->getOperand(0)->getType());
3643 Type *SrcVecTy = ToVectorTy(I->getOperand(0)->getType(), VF);
3644 return TTI.getCastInstrCost(I->getOpcode(), VectorTy, SrcVecTy);
3646 case Instruction::Call: {
3647 CallInst *CI = cast<CallInst>(I);
3648 Intrinsic::ID ID = getIntrinsicIDForCall(CI, TLI);
3649 assert(ID && "Not an intrinsic call!");
3650 Type *RetTy = ToVectorTy(CI->getType(), VF);
3651 SmallVector<Type*, 4> Tys;
3652 for (unsigned i = 0, ie = CI->getNumArgOperands(); i != ie; ++i)
3653 Tys.push_back(ToVectorTy(CI->getArgOperand(i)->getType(), VF));
3654 return TTI.getIntrinsicInstrCost(ID, RetTy, Tys);
3657 // We are scalarizing the instruction. Return the cost of the scalar
3658 // instruction, plus the cost of insert and extract into vector
3659 // elements, times the vector width.
3662 if (!RetTy->isVoidTy() && VF != 1) {
3663 unsigned InsCost = TTI.getVectorInstrCost(Instruction::InsertElement,
3665 unsigned ExtCost = TTI.getVectorInstrCost(Instruction::ExtractElement,
3668 // The cost of inserting the results plus extracting each one of the
3670 Cost += VF * (InsCost + ExtCost * I->getNumOperands());
3673 // The cost of executing VF copies of the scalar instruction. This opcode
3674 // is unknown. Assume that it is the same as 'mul'.
3675 Cost += VF * TTI.getArithmeticInstrCost(Instruction::Mul, VectorTy);
3681 Type* LoopVectorizationCostModel::ToVectorTy(Type *Scalar, unsigned VF) {
3682 if (Scalar->isVoidTy() || VF == 1)
3684 return VectorType::get(Scalar, VF);
3687 char LoopVectorize::ID = 0;
3688 static const char lv_name[] = "Loop Vectorization";
3689 INITIALIZE_PASS_BEGIN(LoopVectorize, LV_NAME, lv_name, false, false)
3690 INITIALIZE_AG_DEPENDENCY(AliasAnalysis)
3691 INITIALIZE_AG_DEPENDENCY(TargetTransformInfo)
3692 INITIALIZE_PASS_DEPENDENCY(ScalarEvolution)
3693 INITIALIZE_PASS_DEPENDENCY(LoopSimplify)
3694 INITIALIZE_PASS_END(LoopVectorize, LV_NAME, lv_name, false, false)
3697 Pass *createLoopVectorizePass() {
3698 return new LoopVectorize();
3702 bool LoopVectorizationCostModel::isConsecutiveLoadOrStore(Instruction *Inst) {
3703 // Check for a store.
3704 if (StoreInst *ST = dyn_cast<StoreInst>(Inst))
3705 return Legal->isConsecutivePtr(ST->getPointerOperand()) != 0;
3707 // Check for a load.
3708 if (LoadInst *LI = dyn_cast<LoadInst>(Inst))
3709 return Legal->isConsecutivePtr(LI->getPointerOperand()) != 0;