1 //===-- llvm/Target/TargetLowering.h - Target Lowering Info -----*- C++ -*-===//
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 file describes how to lower LLVM code to machine code. This has two
13 // 1. Which ValueTypes are natively supported by the target.
14 // 2. Which operations are supported for supported ValueTypes.
15 // 3. Cost thresholds for alternative implementations of certain operations.
17 // In addition it has a few other components, like information about FP
20 //===----------------------------------------------------------------------===//
22 #ifndef LLVM_TARGET_TARGETLOWERING_H
23 #define LLVM_TARGET_TARGETLOWERING_H
25 #include "llvm/CallingConv.h"
26 #include "llvm/InlineAsm.h"
27 #include "llvm/CodeGen/SelectionDAGNodes.h"
28 #include "llvm/CodeGen/RuntimeLibcalls.h"
29 #include "llvm/ADT/APFloat.h"
30 #include "llvm/ADT/DenseMap.h"
31 #include "llvm/ADT/SmallSet.h"
32 #include "llvm/ADT/SmallVector.h"
33 #include "llvm/ADT/STLExtras.h"
34 #include "llvm/Support/DebugLoc.h"
35 #include "llvm/Target/TargetMachine.h"
45 class MachineBasicBlock;
46 class MachineFunction;
47 class MachineFrameInfo;
49 class MachineModuleInfo;
56 class TargetRegisterClass;
57 class TargetSubtarget;
58 class TargetLoweringObjectFile;
61 // FIXME: should this be here?
70 TLSModel::Model getTLSModel(const GlobalValue *GV, Reloc::Model reloc);
73 //===----------------------------------------------------------------------===//
74 /// TargetLowering - This class defines information used to lower LLVM code to
75 /// legal SelectionDAG operators that the target instruction selector can accept
78 /// This class also defines callbacks that targets must implement to lower
79 /// target-specific constructs to SelectionDAG operators.
81 class TargetLowering {
82 TargetLowering(const TargetLowering&); // DO NOT IMPLEMENT
83 void operator=(const TargetLowering&); // DO NOT IMPLEMENT
85 /// LegalizeAction - This enum indicates whether operations are valid for a
86 /// target, and if not, what action should be used to make them valid.
88 Legal, // The target natively supports this operation.
89 Promote, // This operation should be executed in a larger type.
90 Expand, // Try to expand this to other ops, otherwise use a libcall.
91 Custom // Use the LowerOperation hook to implement custom lowering.
94 enum BooleanContent { // How the target represents true/false values.
95 UndefinedBooleanContent, // Only bit 0 counts, the rest can hold garbage.
96 ZeroOrOneBooleanContent, // All bits zero except for bit 0.
97 ZeroOrNegativeOneBooleanContent // All bits equal to bit 0.
100 enum SchedPreference {
101 SchedulingForLatency, // Scheduling for shortest total latency.
102 SchedulingForRegPressure // Scheduling for lowest register pressure.
105 /// NOTE: The constructor takes ownership of TLOF.
106 explicit TargetLowering(TargetMachine &TM, TargetLoweringObjectFile *TLOF);
107 virtual ~TargetLowering();
109 TargetMachine &getTargetMachine() const { return TM; }
110 const TargetData *getTargetData() const { return TD; }
111 TargetLoweringObjectFile &getObjFileLowering() const { return TLOF; }
113 bool isBigEndian() const { return !IsLittleEndian; }
114 bool isLittleEndian() const { return IsLittleEndian; }
115 MVT getPointerTy() const { return PointerTy; }
116 MVT getShiftAmountTy() const { return ShiftAmountTy; }
118 /// usesGlobalOffsetTable - Return true if this target uses a GOT for PIC
120 bool usesGlobalOffsetTable() const { return UsesGlobalOffsetTable; }
122 /// isSelectExpensive - Return true if the select operation is expensive for
124 bool isSelectExpensive() const { return SelectIsExpensive; }
126 /// isIntDivCheap() - Return true if integer divide is usually cheaper than
127 /// a sequence of several shifts, adds, and multiplies for this target.
128 bool isIntDivCheap() const { return IntDivIsCheap; }
130 /// isPow2DivCheap() - Return true if pow2 div is cheaper than a chain of
132 bool isPow2DivCheap() const { return Pow2DivIsCheap; }
134 /// getSetCCResultType - Return the ValueType of the result of SETCC
135 /// operations. Also used to obtain the target's preferred type for
136 /// the condition operand of SELECT and BRCOND nodes. In the case of
137 /// BRCOND the argument passed is MVT::Other since there are no other
138 /// operands to get a type hint from.
140 MVT::SimpleValueType getSetCCResultType(EVT VT) const;
142 /// getCmpLibcallReturnType - Return the ValueType for comparison
143 /// libcalls. Comparions libcalls include floating point comparion calls,
144 /// and Ordered/Unordered check calls on floating point numbers.
146 MVT::SimpleValueType getCmpLibcallReturnType() const;
148 /// getBooleanContents - For targets without i1 registers, this gives the
149 /// nature of the high-bits of boolean values held in types wider than i1.
150 /// "Boolean values" are special true/false values produced by nodes like
151 /// SETCC and consumed (as the condition) by nodes like SELECT and BRCOND.
152 /// Not to be confused with general values promoted from i1.
153 BooleanContent getBooleanContents() const { return BooleanContents;}
155 /// getSchedulingPreference - Return target scheduling preference.
156 SchedPreference getSchedulingPreference() const {
157 return SchedPreferenceInfo;
160 /// getRegClassFor - Return the register class that should be used for the
161 /// specified value type. This may only be called on legal types.
162 TargetRegisterClass *getRegClassFor(EVT VT) const {
163 assert(VT.isSimple() && "getRegClassFor called on illegal type!");
164 TargetRegisterClass *RC = RegClassForVT[VT.getSimpleVT().SimpleTy];
165 assert(RC && "This value type is not natively supported!");
169 /// isTypeLegal - Return true if the target has native support for the
170 /// specified value type. This means that it has a register that directly
171 /// holds it without promotions or expansions.
172 bool isTypeLegal(EVT VT) const {
173 assert(!VT.isSimple() ||
174 (unsigned)VT.getSimpleVT().SimpleTy < array_lengthof(RegClassForVT));
175 return VT.isSimple() && RegClassForVT[VT.getSimpleVT().SimpleTy] != 0;
178 class ValueTypeActionImpl {
179 /// ValueTypeActions - This is a bitvector that contains two bits for each
180 /// value type, where the two bits correspond to the LegalizeAction enum.
181 /// This can be queried with "getTypeAction(VT)".
182 /// dimension by (MVT::MAX_ALLOWED_VALUETYPE/32) * 2
183 uint32_t ValueTypeActions[(MVT::MAX_ALLOWED_VALUETYPE/32)*2];
185 ValueTypeActionImpl() {
186 ValueTypeActions[0] = ValueTypeActions[1] = 0;
187 ValueTypeActions[2] = ValueTypeActions[3] = 0;
189 ValueTypeActionImpl(const ValueTypeActionImpl &RHS) {
190 ValueTypeActions[0] = RHS.ValueTypeActions[0];
191 ValueTypeActions[1] = RHS.ValueTypeActions[1];
192 ValueTypeActions[2] = RHS.ValueTypeActions[2];
193 ValueTypeActions[3] = RHS.ValueTypeActions[3];
196 LegalizeAction getTypeAction(LLVMContext &Context, EVT VT) const {
197 if (VT.isExtended()) {
199 return VT.isPow2VectorType() ? Expand : Promote;
202 // First promote to a power-of-two size, then expand if necessary.
203 return VT == VT.getRoundIntegerType(Context) ? Expand : Promote;
204 assert(0 && "Unsupported extended type!");
207 unsigned I = VT.getSimpleVT().SimpleTy;
208 assert(I<4*array_lengthof(ValueTypeActions)*sizeof(ValueTypeActions[0]));
209 return (LegalizeAction)((ValueTypeActions[I>>4] >> ((2*I) & 31)) & 3);
211 void setTypeAction(EVT VT, LegalizeAction Action) {
212 unsigned I = VT.getSimpleVT().SimpleTy;
213 assert(I<4*array_lengthof(ValueTypeActions)*sizeof(ValueTypeActions[0]));
214 ValueTypeActions[I>>4] |= Action << ((I*2) & 31);
218 const ValueTypeActionImpl &getValueTypeActions() const {
219 return ValueTypeActions;
222 /// getTypeAction - Return how we should legalize values of this type, either
223 /// it is already legal (return 'Legal') or we need to promote it to a larger
224 /// type (return 'Promote'), or we need to expand it into multiple registers
225 /// of smaller integer type (return 'Expand'). 'Custom' is not an option.
226 LegalizeAction getTypeAction(LLVMContext &Context, EVT VT) const {
227 return ValueTypeActions.getTypeAction(Context, VT);
230 /// getTypeToTransformTo - For types supported by the target, this is an
231 /// identity function. For types that must be promoted to larger types, this
232 /// returns the larger type to promote to. For integer types that are larger
233 /// than the largest integer register, this contains one step in the expansion
234 /// to get to the smaller register. For illegal floating point types, this
235 /// returns the integer type to transform to.
236 EVT getTypeToTransformTo(LLVMContext &Context, EVT VT) const {
238 assert((unsigned)VT.getSimpleVT().SimpleTy <
239 array_lengthof(TransformToType));
240 EVT NVT = TransformToType[VT.getSimpleVT().SimpleTy];
241 assert(getTypeAction(Context, NVT) != Promote &&
242 "Promote may not follow Expand or Promote");
247 EVT NVT = VT.getPow2VectorType(Context);
249 // Vector length is a power of 2 - split to half the size.
250 unsigned NumElts = VT.getVectorNumElements();
251 EVT EltVT = VT.getVectorElementType();
252 return (NumElts == 1) ?
253 EltVT : EVT::getVectorVT(Context, EltVT, NumElts / 2);
255 // Promote to a power of two size, avoiding multi-step promotion.
256 return getTypeAction(Context, NVT) == Promote ?
257 getTypeToTransformTo(Context, NVT) : NVT;
258 } else if (VT.isInteger()) {
259 EVT NVT = VT.getRoundIntegerType(Context);
261 // Size is a power of two - expand to half the size.
262 return EVT::getIntegerVT(Context, VT.getSizeInBits() / 2);
264 // Promote to a power of two size, avoiding multi-step promotion.
265 return getTypeAction(Context, NVT) == Promote ?
266 getTypeToTransformTo(Context, NVT) : NVT;
268 assert(0 && "Unsupported extended type!");
269 return MVT(MVT::Other); // Not reached
272 /// getTypeToExpandTo - For types supported by the target, this is an
273 /// identity function. For types that must be expanded (i.e. integer types
274 /// that are larger than the largest integer register or illegal floating
275 /// point types), this returns the largest legal type it will be expanded to.
276 EVT getTypeToExpandTo(LLVMContext &Context, EVT VT) const {
277 assert(!VT.isVector());
279 switch (getTypeAction(Context, VT)) {
283 VT = getTypeToTransformTo(Context, VT);
286 assert(false && "Type is not legal nor is it to be expanded!");
293 /// getVectorTypeBreakdown - Vector types are broken down into some number of
294 /// legal first class types. For example, EVT::v8f32 maps to 2 EVT::v4f32
295 /// with Altivec or SSE1, or 8 promoted EVT::f64 values with the X86 FP stack.
296 /// Similarly, EVT::v2i64 turns into 4 EVT::i32 values with both PPC and X86.
298 /// This method returns the number of registers needed, and the VT for each
299 /// register. It also returns the VT and quantity of the intermediate values
300 /// before they are promoted/expanded.
302 unsigned getVectorTypeBreakdown(LLVMContext &Context, EVT VT,
304 unsigned &NumIntermediates,
305 EVT &RegisterVT) const;
307 /// getTgtMemIntrinsic: Given an intrinsic, checks if on the target the
308 /// intrinsic will need to map to a MemIntrinsicNode (touches memory). If
309 /// this is the case, it returns true and store the intrinsic
310 /// information into the IntrinsicInfo that was passed to the function.
311 typedef struct IntrinsicInfo {
312 unsigned opc; // target opcode
313 EVT memVT; // memory VT
314 const Value* ptrVal; // value representing memory location
315 int offset; // offset off of ptrVal
316 unsigned align; // alignment
317 bool vol; // is volatile?
318 bool readMem; // reads memory?
319 bool writeMem; // writes memory?
322 virtual bool getTgtMemIntrinsic(IntrinsicInfo& Info,
323 CallInst &I, unsigned Intrinsic) {
327 /// getWidenVectorType: given a vector type, returns the type to widen to
328 /// (e.g., v7i8 to v8i8). If the vector type is legal, it returns itself.
329 /// If there is no vector type that we want to widen to, returns MVT::Other
330 /// When and were to widen is target dependent based on the cost of
331 /// scalarizing vs using the wider vector type.
332 virtual EVT getWidenVectorType(EVT VT) const;
334 /// isFPImmLegal - Returns true if the target can instruction select the
335 /// specified FP immediate natively. If false, the legalizer will materialize
336 /// the FP immediate as a load from a constant pool.
337 virtual bool isFPImmLegal(const APFloat &Imm, EVT VT) const {
341 /// isShuffleMaskLegal - Targets can use this to indicate that they only
342 /// support *some* VECTOR_SHUFFLE operations, those with specific masks.
343 /// By default, if a target supports the VECTOR_SHUFFLE node, all mask values
344 /// are assumed to be legal.
345 virtual bool isShuffleMaskLegal(const SmallVectorImpl<int> &Mask,
350 /// isVectorClearMaskLegal - Similar to isShuffleMaskLegal. This is
351 /// used by Targets can use this to indicate if there is a suitable
352 /// VECTOR_SHUFFLE that can be used to replace a VAND with a constant
354 virtual bool isVectorClearMaskLegal(const SmallVectorImpl<int> &Mask,
359 /// getOperationAction - Return how this operation should be treated: either
360 /// it is legal, needs to be promoted to a larger size, needs to be
361 /// expanded to some other code sequence, or the target has a custom expander
363 LegalizeAction getOperationAction(unsigned Op, EVT VT) const {
364 if (VT.isExtended()) return Expand;
365 assert(Op < array_lengthof(OpActions[0]) &&
366 (unsigned)VT.getSimpleVT().SimpleTy < sizeof(OpActions[0][0])*8 &&
367 "Table isn't big enough!");
368 unsigned I = (unsigned) VT.getSimpleVT().SimpleTy;
371 return (LegalizeAction)((OpActions[I][Op] >> (J*2) ) & 3);
374 /// isOperationLegalOrCustom - Return true if the specified operation is
375 /// legal on this target or can be made legal with custom lowering. This
376 /// is used to help guide high-level lowering decisions.
377 bool isOperationLegalOrCustom(unsigned Op, EVT VT) const {
378 return (VT == MVT::Other || isTypeLegal(VT)) &&
379 (getOperationAction(Op, VT) == Legal ||
380 getOperationAction(Op, VT) == Custom);
383 /// isOperationLegal - Return true if the specified operation is legal on this
385 bool isOperationLegal(unsigned Op, EVT VT) const {
386 return (VT == MVT::Other || isTypeLegal(VT)) &&
387 getOperationAction(Op, VT) == Legal;
390 /// getLoadExtAction - Return how this load with extension should be treated:
391 /// either it is legal, needs to be promoted to a larger size, needs to be
392 /// expanded to some other code sequence, or the target has a custom expander
394 LegalizeAction getLoadExtAction(unsigned LType, EVT VT) const {
395 assert(LType < array_lengthof(LoadExtActions) &&
396 (unsigned)VT.getSimpleVT().SimpleTy < sizeof(LoadExtActions[0])*4 &&
397 "Table isn't big enough!");
398 return (LegalizeAction)((LoadExtActions[LType] >>
399 (2*VT.getSimpleVT().SimpleTy)) & 3);
402 /// isLoadExtLegal - Return true if the specified load with extension is legal
404 bool isLoadExtLegal(unsigned LType, EVT VT) const {
405 return VT.isSimple() &&
406 (getLoadExtAction(LType, VT) == Legal ||
407 getLoadExtAction(LType, VT) == Custom);
410 /// getTruncStoreAction - Return how this store with truncation should be
411 /// treated: either it is legal, needs to be promoted to a larger size, needs
412 /// to be expanded to some other code sequence, or the target has a custom
414 LegalizeAction getTruncStoreAction(EVT ValVT,
416 assert((unsigned)ValVT.getSimpleVT().SimpleTy <
417 array_lengthof(TruncStoreActions) &&
418 (unsigned)MemVT.getSimpleVT().SimpleTy <
419 sizeof(TruncStoreActions[0])*4 &&
420 "Table isn't big enough!");
421 return (LegalizeAction)((TruncStoreActions[ValVT.getSimpleVT().SimpleTy] >>
422 (2*MemVT.getSimpleVT().SimpleTy)) & 3);
425 /// isTruncStoreLegal - Return true if the specified store with truncation is
426 /// legal on this target.
427 bool isTruncStoreLegal(EVT ValVT, EVT MemVT) const {
428 return isTypeLegal(ValVT) && MemVT.isSimple() &&
429 (getTruncStoreAction(ValVT, MemVT) == Legal ||
430 getTruncStoreAction(ValVT, MemVT) == Custom);
433 /// getIndexedLoadAction - Return how the indexed load should be treated:
434 /// either it is legal, needs to be promoted to a larger size, needs to be
435 /// expanded to some other code sequence, or the target has a custom expander
438 getIndexedLoadAction(unsigned IdxMode, EVT VT) const {
439 assert( IdxMode < array_lengthof(IndexedModeActions[0][0]) &&
440 ((unsigned)VT.getSimpleVT().SimpleTy) < MVT::LAST_VALUETYPE &&
441 "Table isn't big enough!");
442 return (LegalizeAction)((IndexedModeActions[
443 (unsigned)VT.getSimpleVT().SimpleTy][0][IdxMode]));
446 /// isIndexedLoadLegal - Return true if the specified indexed load is legal
448 bool isIndexedLoadLegal(unsigned IdxMode, EVT VT) const {
449 return VT.isSimple() &&
450 (getIndexedLoadAction(IdxMode, VT) == Legal ||
451 getIndexedLoadAction(IdxMode, VT) == Custom);
454 /// getIndexedStoreAction - Return how the indexed store should be treated:
455 /// either it is legal, needs to be promoted to a larger size, needs to be
456 /// expanded to some other code sequence, or the target has a custom expander
459 getIndexedStoreAction(unsigned IdxMode, EVT VT) const {
460 assert(IdxMode < array_lengthof(IndexedModeActions[0][1]) &&
461 (unsigned)VT.getSimpleVT().SimpleTy < MVT::LAST_VALUETYPE &&
462 "Table isn't big enough!");
463 return (LegalizeAction)((IndexedModeActions[
464 (unsigned)VT.getSimpleVT().SimpleTy][1][IdxMode]));
467 /// isIndexedStoreLegal - Return true if the specified indexed load is legal
469 bool isIndexedStoreLegal(unsigned IdxMode, EVT VT) const {
470 return VT.isSimple() &&
471 (getIndexedStoreAction(IdxMode, VT) == Legal ||
472 getIndexedStoreAction(IdxMode, VT) == Custom);
475 /// getConvertAction - Return how the conversion should be treated:
476 /// either it is legal, needs to be promoted to a larger size, needs to be
477 /// expanded to some other code sequence, or the target has a custom expander
480 getConvertAction(EVT FromVT, EVT ToVT) const {
481 assert((unsigned)FromVT.getSimpleVT().SimpleTy <
482 array_lengthof(ConvertActions) &&
483 (unsigned)ToVT.getSimpleVT().SimpleTy <
484 sizeof(ConvertActions[0])*4 &&
485 "Table isn't big enough!");
486 return (LegalizeAction)((ConvertActions[FromVT.getSimpleVT().SimpleTy] >>
487 (2*ToVT.getSimpleVT().SimpleTy)) & 3);
490 /// isConvertLegal - Return true if the specified conversion is legal
492 bool isConvertLegal(EVT FromVT, EVT ToVT) const {
493 return isTypeLegal(FromVT) && isTypeLegal(ToVT) &&
494 (getConvertAction(FromVT, ToVT) == Legal ||
495 getConvertAction(FromVT, ToVT) == Custom);
498 /// getCondCodeAction - Return how the condition code should be treated:
499 /// either it is legal, needs to be expanded to some other code sequence,
500 /// or the target has a custom expander for it.
502 getCondCodeAction(ISD::CondCode CC, EVT VT) const {
503 assert((unsigned)CC < array_lengthof(CondCodeActions) &&
504 (unsigned)VT.getSimpleVT().SimpleTy < sizeof(CondCodeActions[0])*4 &&
505 "Table isn't big enough!");
506 LegalizeAction Action = (LegalizeAction)
507 ((CondCodeActions[CC] >> (2*VT.getSimpleVT().SimpleTy)) & 3);
508 assert(Action != Promote && "Can't promote condition code!");
512 /// isCondCodeLegal - Return true if the specified condition code is legal
514 bool isCondCodeLegal(ISD::CondCode CC, EVT VT) const {
515 return getCondCodeAction(CC, VT) == Legal ||
516 getCondCodeAction(CC, VT) == Custom;
520 /// getTypeToPromoteTo - If the action for this operation is to promote, this
521 /// method returns the ValueType to promote to.
522 EVT getTypeToPromoteTo(unsigned Op, EVT VT) const {
523 assert(getOperationAction(Op, VT) == Promote &&
524 "This operation isn't promoted!");
526 // See if this has an explicit type specified.
527 std::map<std::pair<unsigned, MVT::SimpleValueType>,
528 MVT::SimpleValueType>::const_iterator PTTI =
529 PromoteToType.find(std::make_pair(Op, VT.getSimpleVT().SimpleTy));
530 if (PTTI != PromoteToType.end()) return PTTI->second;
532 assert((VT.isInteger() || VT.isFloatingPoint()) &&
533 "Cannot autopromote this type, add it with AddPromotedToType.");
537 NVT = (MVT::SimpleValueType)(NVT.getSimpleVT().SimpleTy+1);
538 assert(NVT.isInteger() == VT.isInteger() && NVT != MVT::isVoid &&
539 "Didn't find type to promote to!");
540 } while (!isTypeLegal(NVT) ||
541 getOperationAction(Op, NVT) == Promote);
545 /// getValueType - Return the EVT corresponding to this LLVM type.
546 /// This is fixed by the LLVM operations except for the pointer size. If
547 /// AllowUnknown is true, this will return MVT::Other for types with no EVT
548 /// counterpart (e.g. structs), otherwise it will assert.
549 EVT getValueType(const Type *Ty, bool AllowUnknown = false) const {
550 EVT VT = EVT::getEVT(Ty, AllowUnknown);
551 return VT == MVT:: iPTR ? PointerTy : VT;
554 /// getByValTypeAlignment - Return the desired alignment for ByVal aggregate
555 /// function arguments in the caller parameter area. This is the actual
556 /// alignment, not its logarithm.
557 virtual unsigned getByValTypeAlignment(const Type *Ty) const;
559 /// getRegisterType - Return the type of registers that this ValueType will
560 /// eventually require.
561 EVT getRegisterType(MVT VT) const {
562 assert((unsigned)VT.SimpleTy < array_lengthof(RegisterTypeForVT));
563 return RegisterTypeForVT[VT.SimpleTy];
566 /// getRegisterType - Return the type of registers that this ValueType will
567 /// eventually require.
568 EVT getRegisterType(LLVMContext &Context, EVT VT) const {
570 assert((unsigned)VT.getSimpleVT().SimpleTy <
571 array_lengthof(RegisterTypeForVT));
572 return RegisterTypeForVT[VT.getSimpleVT().SimpleTy];
576 unsigned NumIntermediates;
577 (void)getVectorTypeBreakdown(Context, VT, VT1,
578 NumIntermediates, RegisterVT);
581 if (VT.isInteger()) {
582 return getRegisterType(Context, getTypeToTransformTo(Context, VT));
584 assert(0 && "Unsupported extended type!");
585 return EVT(MVT::Other); // Not reached
588 /// getNumRegisters - Return the number of registers that this ValueType will
589 /// eventually require. This is one for any types promoted to live in larger
590 /// registers, but may be more than one for types (like i64) that are split
591 /// into pieces. For types like i140, which are first promoted then expanded,
592 /// it is the number of registers needed to hold all the bits of the original
593 /// type. For an i140 on a 32 bit machine this means 5 registers.
594 unsigned getNumRegisters(LLVMContext &Context, EVT VT) const {
596 assert((unsigned)VT.getSimpleVT().SimpleTy <
597 array_lengthof(NumRegistersForVT));
598 return NumRegistersForVT[VT.getSimpleVT().SimpleTy];
602 unsigned NumIntermediates;
603 return getVectorTypeBreakdown(Context, VT, VT1, NumIntermediates, VT2);
605 if (VT.isInteger()) {
606 unsigned BitWidth = VT.getSizeInBits();
607 unsigned RegWidth = getRegisterType(Context, VT).getSizeInBits();
608 return (BitWidth + RegWidth - 1) / RegWidth;
610 assert(0 && "Unsupported extended type!");
611 return 0; // Not reached
614 /// ShouldShrinkFPConstant - If true, then instruction selection should
615 /// seek to shrink the FP constant of the specified type to a smaller type
616 /// in order to save space and / or reduce runtime.
617 virtual bool ShouldShrinkFPConstant(EVT VT) const { return true; }
619 /// hasTargetDAGCombine - If true, the target has custom DAG combine
620 /// transformations that it can perform for the specified node.
621 bool hasTargetDAGCombine(ISD::NodeType NT) const {
622 assert(unsigned(NT >> 3) < array_lengthof(TargetDAGCombineArray));
623 return TargetDAGCombineArray[NT >> 3] & (1 << (NT&7));
626 /// This function returns the maximum number of store operations permitted
627 /// to replace a call to llvm.memset. The value is set by the target at the
628 /// performance threshold for such a replacement.
629 /// @brief Get maximum # of store operations permitted for llvm.memset
630 unsigned getMaxStoresPerMemset() const { return maxStoresPerMemset; }
632 /// This function returns the maximum number of store operations permitted
633 /// to replace a call to llvm.memcpy. The value is set by the target at the
634 /// performance threshold for such a replacement.
635 /// @brief Get maximum # of store operations permitted for llvm.memcpy
636 unsigned getMaxStoresPerMemcpy() const { return maxStoresPerMemcpy; }
638 /// This function returns the maximum number of store operations permitted
639 /// to replace a call to llvm.memmove. The value is set by the target at the
640 /// performance threshold for such a replacement.
641 /// @brief Get maximum # of store operations permitted for llvm.memmove
642 unsigned getMaxStoresPerMemmove() const { return maxStoresPerMemmove; }
644 /// This function returns true if the target allows unaligned memory accesses.
645 /// of the specified type. This is used, for example, in situations where an
646 /// array copy/move/set is converted to a sequence of store operations. It's
647 /// use helps to ensure that such replacements don't generate code that causes
648 /// an alignment error (trap) on the target machine.
649 /// @brief Determine if the target supports unaligned memory accesses.
650 virtual bool allowsUnalignedMemoryAccesses(EVT VT) const {
654 /// This function returns true if the target would benefit from code placement
656 /// @brief Determine if the target should perform code placement optimization.
657 bool shouldOptimizeCodePlacement() const {
658 return benefitFromCodePlacementOpt;
661 /// getOptimalMemOpType - Returns the target specific optimal type for load
662 /// and store operations as a result of memset, memcpy, and memmove lowering.
663 /// It returns EVT::iAny if SelectionDAG should be responsible for
665 virtual EVT getOptimalMemOpType(uint64_t Size, unsigned Align,
666 bool isSrcConst, bool isSrcStr,
667 SelectionDAG &DAG) const {
671 /// usesUnderscoreSetJmp - Determine if we should use _setjmp or setjmp
672 /// to implement llvm.setjmp.
673 bool usesUnderscoreSetJmp() const {
674 return UseUnderscoreSetJmp;
677 /// usesUnderscoreLongJmp - Determine if we should use _longjmp or longjmp
678 /// to implement llvm.longjmp.
679 bool usesUnderscoreLongJmp() const {
680 return UseUnderscoreLongJmp;
683 /// getStackPointerRegisterToSaveRestore - If a physical register, this
684 /// specifies the register that llvm.savestack/llvm.restorestack should save
686 unsigned getStackPointerRegisterToSaveRestore() const {
687 return StackPointerRegisterToSaveRestore;
690 /// getExceptionAddressRegister - If a physical register, this returns
691 /// the register that receives the exception address on entry to a landing
693 unsigned getExceptionAddressRegister() const {
694 return ExceptionPointerRegister;
697 /// getExceptionSelectorRegister - If a physical register, this returns
698 /// the register that receives the exception typeid on entry to a landing
700 unsigned getExceptionSelectorRegister() const {
701 return ExceptionSelectorRegister;
704 /// getJumpBufSize - returns the target's jmp_buf size in bytes (if never
705 /// set, the default is 200)
706 unsigned getJumpBufSize() const {
710 /// getJumpBufAlignment - returns the target's jmp_buf alignment in bytes
711 /// (if never set, the default is 0)
712 unsigned getJumpBufAlignment() const {
713 return JumpBufAlignment;
716 /// getIfCvtBlockLimit - returns the target specific if-conversion block size
717 /// limit. Any block whose size is greater should not be predicated.
718 unsigned getIfCvtBlockSizeLimit() const {
719 return IfCvtBlockSizeLimit;
722 /// getIfCvtDupBlockLimit - returns the target specific size limit for a
723 /// block to be considered for duplication. Any block whose size is greater
724 /// should not be duplicated to facilitate its predication.
725 unsigned getIfCvtDupBlockSizeLimit() const {
726 return IfCvtDupBlockSizeLimit;
729 /// getPrefLoopAlignment - return the preferred loop alignment.
731 unsigned getPrefLoopAlignment() const {
732 return PrefLoopAlignment;
735 /// getPreIndexedAddressParts - returns true by value, base pointer and
736 /// offset pointer and addressing mode by reference if the node's address
737 /// can be legally represented as pre-indexed load / store address.
738 virtual bool getPreIndexedAddressParts(SDNode *N, SDValue &Base,
740 ISD::MemIndexedMode &AM,
741 SelectionDAG &DAG) const {
745 /// getPostIndexedAddressParts - returns true by value, base pointer and
746 /// offset pointer and addressing mode by reference if this node can be
747 /// combined with a load / store to form a post-indexed load / store.
748 virtual bool getPostIndexedAddressParts(SDNode *N, SDNode *Op,
749 SDValue &Base, SDValue &Offset,
750 ISD::MemIndexedMode &AM,
751 SelectionDAG &DAG) const {
755 /// getJumpTableEncoding - Return the entry encoding for a jump table in the
756 /// current function. The returned value is a member of the
757 /// MachineJumpTableInfo::JTEntryKind enum.
758 virtual unsigned getJumpTableEncoding() const;
760 /// getPICJumpTableRelocaBase - Returns relocation base for the given PIC
762 virtual SDValue getPICJumpTableRelocBase(SDValue Table,
763 SelectionDAG &DAG) const;
765 /// isOffsetFoldingLegal - Return true if folding a constant offset
766 /// with the given GlobalAddress is legal. It is frequently not legal in
767 /// PIC relocation models.
768 virtual bool isOffsetFoldingLegal(const GlobalAddressSDNode *GA) const;
770 /// getFunctionAlignment - Return the Log2 alignment of this function.
771 virtual unsigned getFunctionAlignment(const Function *) const = 0;
773 //===--------------------------------------------------------------------===//
774 // TargetLowering Optimization Methods
777 /// TargetLoweringOpt - A convenience struct that encapsulates a DAG, and two
778 /// SDValues for returning information from TargetLowering to its clients
779 /// that want to combine
780 struct TargetLoweringOpt {
786 explicit TargetLoweringOpt(SelectionDAG &InDAG, bool Shrink = false) :
787 DAG(InDAG), ShrinkOps(Shrink) {}
789 bool CombineTo(SDValue O, SDValue N) {
795 /// ShrinkDemandedConstant - Check to see if the specified operand of the
796 /// specified instruction is a constant integer. If so, check to see if
797 /// there are any bits set in the constant that are not demanded. If so,
798 /// shrink the constant and return true.
799 bool ShrinkDemandedConstant(SDValue Op, const APInt &Demanded);
801 /// ShrinkDemandedOp - Convert x+y to (VT)((SmallVT)x+(SmallVT)y) if the
802 /// casts are free. This uses isZExtFree and ZERO_EXTEND for the widening
803 /// cast, but it could be generalized for targets with other types of
804 /// implicit widening casts.
805 bool ShrinkDemandedOp(SDValue Op, unsigned BitWidth, const APInt &Demanded,
809 /// SimplifyDemandedBits - Look at Op. At this point, we know that only the
810 /// DemandedMask bits of the result of Op are ever used downstream. If we can
811 /// use this information to simplify Op, create a new simplified DAG node and
812 /// return true, returning the original and new nodes in Old and New.
813 /// Otherwise, analyze the expression and return a mask of KnownOne and
814 /// KnownZero bits for the expression (used to simplify the caller).
815 /// The KnownZero/One bits may only be accurate for those bits in the
817 bool SimplifyDemandedBits(SDValue Op, const APInt &DemandedMask,
818 APInt &KnownZero, APInt &KnownOne,
819 TargetLoweringOpt &TLO, unsigned Depth = 0) const;
821 /// computeMaskedBitsForTargetNode - Determine which of the bits specified in
822 /// Mask are known to be either zero or one and return them in the
823 /// KnownZero/KnownOne bitsets.
824 virtual void computeMaskedBitsForTargetNode(const SDValue Op,
828 const SelectionDAG &DAG,
829 unsigned Depth = 0) const;
831 /// ComputeNumSignBitsForTargetNode - This method can be implemented by
832 /// targets that want to expose additional information about sign bits to the
834 virtual unsigned ComputeNumSignBitsForTargetNode(SDValue Op,
835 unsigned Depth = 0) const;
837 struct DAGCombinerInfo {
838 void *DC; // The DAG Combiner object.
840 bool BeforeLegalizeOps;
841 bool CalledByLegalizer;
845 DAGCombinerInfo(SelectionDAG &dag, bool bl, bool blo, bool cl, void *dc)
846 : DC(dc), BeforeLegalize(bl), BeforeLegalizeOps(blo),
847 CalledByLegalizer(cl), DAG(dag) {}
849 bool isBeforeLegalize() const { return BeforeLegalize; }
850 bool isBeforeLegalizeOps() const { return BeforeLegalizeOps; }
851 bool isCalledByLegalizer() const { return CalledByLegalizer; }
853 void AddToWorklist(SDNode *N);
854 SDValue CombineTo(SDNode *N, const std::vector<SDValue> &To,
856 SDValue CombineTo(SDNode *N, SDValue Res, bool AddTo = true);
857 SDValue CombineTo(SDNode *N, SDValue Res0, SDValue Res1, bool AddTo = true);
859 void CommitTargetLoweringOpt(const TargetLoweringOpt &TLO);
862 /// SimplifySetCC - Try to simplify a setcc built with the specified operands
863 /// and cc. If it is unable to simplify it, return a null SDValue.
864 SDValue SimplifySetCC(EVT VT, SDValue N0, SDValue N1,
865 ISD::CondCode Cond, bool foldBooleans,
866 DAGCombinerInfo &DCI, DebugLoc dl) const;
868 /// isGAPlusOffset - Returns true (and the GlobalValue and the offset) if the
869 /// node is a GlobalAddress + offset.
871 isGAPlusOffset(SDNode *N, GlobalValue* &GA, int64_t &Offset) const;
873 /// PerformDAGCombine - This method will be invoked for all target nodes and
874 /// for any target-independent nodes that the target has registered with
877 /// The semantics are as follows:
879 /// SDValue.Val == 0 - No change was made
880 /// SDValue.Val == N - N was replaced, is dead, and is already handled.
881 /// otherwise - N should be replaced by the returned Operand.
883 /// In addition, methods provided by DAGCombinerInfo may be used to perform
884 /// more complex transformations.
886 virtual SDValue PerformDAGCombine(SDNode *N, DAGCombinerInfo &DCI) const;
888 //===--------------------------------------------------------------------===//
889 // TargetLowering Configuration Methods - These methods should be invoked by
890 // the derived class constructor to configure this object for the target.
894 /// setUsesGlobalOffsetTable - Specify that this target does or doesn't use a
895 /// GOT for PC-relative code.
896 void setUsesGlobalOffsetTable(bool V) { UsesGlobalOffsetTable = V; }
898 /// setShiftAmountType - Describe the type that should be used for shift
899 /// amounts. This type defaults to the pointer type.
900 void setShiftAmountType(MVT VT) { ShiftAmountTy = VT; }
902 /// setBooleanContents - Specify how the target extends the result of a
903 /// boolean value from i1 to a wider type. See getBooleanContents.
904 void setBooleanContents(BooleanContent Ty) { BooleanContents = Ty; }
906 /// setSchedulingPreference - Specify the target scheduling preference.
907 void setSchedulingPreference(SchedPreference Pref) {
908 SchedPreferenceInfo = Pref;
911 /// setUseUnderscoreSetJmp - Indicate whether this target prefers to
912 /// use _setjmp to implement llvm.setjmp or the non _ version.
913 /// Defaults to false.
914 void setUseUnderscoreSetJmp(bool Val) {
915 UseUnderscoreSetJmp = Val;
918 /// setUseUnderscoreLongJmp - Indicate whether this target prefers to
919 /// use _longjmp to implement llvm.longjmp or the non _ version.
920 /// Defaults to false.
921 void setUseUnderscoreLongJmp(bool Val) {
922 UseUnderscoreLongJmp = Val;
925 /// setStackPointerRegisterToSaveRestore - If set to a physical register, this
926 /// specifies the register that llvm.savestack/llvm.restorestack should save
928 void setStackPointerRegisterToSaveRestore(unsigned R) {
929 StackPointerRegisterToSaveRestore = R;
932 /// setExceptionPointerRegister - If set to a physical register, this sets
933 /// the register that receives the exception address on entry to a landing
935 void setExceptionPointerRegister(unsigned R) {
936 ExceptionPointerRegister = R;
939 /// setExceptionSelectorRegister - If set to a physical register, this sets
940 /// the register that receives the exception typeid on entry to a landing
942 void setExceptionSelectorRegister(unsigned R) {
943 ExceptionSelectorRegister = R;
946 /// SelectIsExpensive - Tells the code generator not to expand operations
947 /// into sequences that use the select operations if possible.
948 void setSelectIsExpensive() { SelectIsExpensive = true; }
950 /// setIntDivIsCheap - Tells the code generator that integer divide is
951 /// expensive, and if possible, should be replaced by an alternate sequence
952 /// of instructions not containing an integer divide.
953 void setIntDivIsCheap(bool isCheap = true) { IntDivIsCheap = isCheap; }
955 /// setPow2DivIsCheap - Tells the code generator that it shouldn't generate
956 /// srl/add/sra for a signed divide by power of two, and let the target handle
958 void setPow2DivIsCheap(bool isCheap = true) { Pow2DivIsCheap = isCheap; }
960 /// addRegisterClass - Add the specified register class as an available
961 /// regclass for the specified value type. This indicates the selector can
962 /// handle values of that class natively.
963 void addRegisterClass(EVT VT, TargetRegisterClass *RC) {
964 assert((unsigned)VT.getSimpleVT().SimpleTy < array_lengthof(RegClassForVT));
965 AvailableRegClasses.push_back(std::make_pair(VT, RC));
966 RegClassForVT[VT.getSimpleVT().SimpleTy] = RC;
969 /// computeRegisterProperties - Once all of the register classes are added,
970 /// this allows us to compute derived properties we expose.
971 void computeRegisterProperties();
973 /// setOperationAction - Indicate that the specified operation does not work
974 /// with the specified type and indicate what to do about it.
975 void setOperationAction(unsigned Op, MVT VT,
976 LegalizeAction Action) {
977 unsigned I = (unsigned)VT.SimpleTy;
980 OpActions[I][Op] &= ~(uint64_t(3UL) << (J*2));
981 OpActions[I][Op] |= (uint64_t)Action << (J*2);
984 /// setLoadExtAction - Indicate that the specified load with extension does
985 /// not work with the with specified type and indicate what to do about it.
986 void setLoadExtAction(unsigned ExtType, MVT VT,
987 LegalizeAction Action) {
988 assert((unsigned)VT.SimpleTy*2 < 63 &&
989 ExtType < array_lengthof(LoadExtActions) &&
990 "Table isn't big enough!");
991 LoadExtActions[ExtType] &= ~(uint64_t(3UL) << VT.SimpleTy*2);
992 LoadExtActions[ExtType] |= (uint64_t)Action << VT.SimpleTy*2;
995 /// setTruncStoreAction - Indicate that the specified truncating store does
996 /// not work with the with specified type and indicate what to do about it.
997 void setTruncStoreAction(MVT ValVT, MVT MemVT,
998 LegalizeAction Action) {
999 assert((unsigned)ValVT.SimpleTy < array_lengthof(TruncStoreActions) &&
1000 (unsigned)MemVT.SimpleTy*2 < 63 &&
1001 "Table isn't big enough!");
1002 TruncStoreActions[ValVT.SimpleTy] &= ~(uint64_t(3UL) << MemVT.SimpleTy*2);
1003 TruncStoreActions[ValVT.SimpleTy] |= (uint64_t)Action << MemVT.SimpleTy*2;
1006 /// setIndexedLoadAction - Indicate that the specified indexed load does or
1007 /// does not work with the with specified type and indicate what to do abort
1008 /// it. NOTE: All indexed mode loads are initialized to Expand in
1009 /// TargetLowering.cpp
1010 void setIndexedLoadAction(unsigned IdxMode, MVT VT,
1011 LegalizeAction Action) {
1012 assert((unsigned)VT.SimpleTy < MVT::LAST_VALUETYPE &&
1013 IdxMode < array_lengthof(IndexedModeActions[0][0]) &&
1014 "Table isn't big enough!");
1015 IndexedModeActions[(unsigned)VT.SimpleTy][0][IdxMode] = (uint8_t)Action;
1018 /// setIndexedStoreAction - Indicate that the specified indexed store does or
1019 /// does not work with the with specified type and indicate what to do about
1020 /// it. NOTE: All indexed mode stores are initialized to Expand in
1021 /// TargetLowering.cpp
1022 void setIndexedStoreAction(unsigned IdxMode, MVT VT,
1023 LegalizeAction Action) {
1024 assert((unsigned)VT.SimpleTy < MVT::LAST_VALUETYPE &&
1025 IdxMode < array_lengthof(IndexedModeActions[0][1] ) &&
1026 "Table isn't big enough!");
1027 IndexedModeActions[(unsigned)VT.SimpleTy][1][IdxMode] = (uint8_t)Action;
1030 /// setConvertAction - Indicate that the specified conversion does or does
1031 /// not work with the with specified type and indicate what to do about it.
1032 void setConvertAction(MVT FromVT, MVT ToVT,
1033 LegalizeAction Action) {
1034 assert((unsigned)FromVT.SimpleTy < array_lengthof(ConvertActions) &&
1035 (unsigned)ToVT.SimpleTy < MVT::LAST_VALUETYPE &&
1036 "Table isn't big enough!");
1037 ConvertActions[FromVT.SimpleTy] &= ~(uint64_t(3UL) << ToVT.SimpleTy*2);
1038 ConvertActions[FromVT.SimpleTy] |= (uint64_t)Action << ToVT.SimpleTy*2;
1041 /// setCondCodeAction - Indicate that the specified condition code is or isn't
1042 /// supported on the target and indicate what to do about it.
1043 void setCondCodeAction(ISD::CondCode CC, MVT VT,
1044 LegalizeAction Action) {
1045 assert((unsigned)VT.SimpleTy < MVT::LAST_VALUETYPE &&
1046 (unsigned)CC < array_lengthof(CondCodeActions) &&
1047 "Table isn't big enough!");
1048 CondCodeActions[(unsigned)CC] &= ~(uint64_t(3UL) << VT.SimpleTy*2);
1049 CondCodeActions[(unsigned)CC] |= (uint64_t)Action << VT.SimpleTy*2;
1052 /// AddPromotedToType - If Opc/OrigVT is specified as being promoted, the
1053 /// promotion code defaults to trying a larger integer/fp until it can find
1054 /// one that works. If that default is insufficient, this method can be used
1055 /// by the target to override the default.
1056 void AddPromotedToType(unsigned Opc, MVT OrigVT, MVT DestVT) {
1057 PromoteToType[std::make_pair(Opc, OrigVT.SimpleTy)] = DestVT.SimpleTy;
1060 /// setTargetDAGCombine - Targets should invoke this method for each target
1061 /// independent node that they want to provide a custom DAG combiner for by
1062 /// implementing the PerformDAGCombine virtual method.
1063 void setTargetDAGCombine(ISD::NodeType NT) {
1064 assert(unsigned(NT >> 3) < array_lengthof(TargetDAGCombineArray));
1065 TargetDAGCombineArray[NT >> 3] |= 1 << (NT&7);
1068 /// setJumpBufSize - Set the target's required jmp_buf buffer size (in
1069 /// bytes); default is 200
1070 void setJumpBufSize(unsigned Size) {
1074 /// setJumpBufAlignment - Set the target's required jmp_buf buffer
1075 /// alignment (in bytes); default is 0
1076 void setJumpBufAlignment(unsigned Align) {
1077 JumpBufAlignment = Align;
1080 /// setIfCvtBlockSizeLimit - Set the target's if-conversion block size
1081 /// limit (in number of instructions); default is 2.
1082 void setIfCvtBlockSizeLimit(unsigned Limit) {
1083 IfCvtBlockSizeLimit = Limit;
1086 /// setIfCvtDupBlockSizeLimit - Set the target's block size limit (in number
1087 /// of instructions) to be considered for code duplication during
1088 /// if-conversion; default is 2.
1089 void setIfCvtDupBlockSizeLimit(unsigned Limit) {
1090 IfCvtDupBlockSizeLimit = Limit;
1093 /// setPrefLoopAlignment - Set the target's preferred loop alignment. Default
1094 /// alignment is zero, it means the target does not care about loop alignment.
1095 void setPrefLoopAlignment(unsigned Align) {
1096 PrefLoopAlignment = Align;
1101 virtual const TargetSubtarget *getSubtarget() {
1102 assert(0 && "Not Implemented");
1103 return NULL; // this is here to silence compiler errors
1106 //===--------------------------------------------------------------------===//
1107 // Lowering methods - These methods must be implemented by targets so that
1108 // the SelectionDAGLowering code knows how to lower these.
1111 /// LowerFormalArguments - This hook must be implemented to lower the
1112 /// incoming (formal) arguments, described by the Ins array, into the
1113 /// specified DAG. The implementation should fill in the InVals array
1114 /// with legal-type argument values, and return the resulting token
1118 LowerFormalArguments(SDValue Chain,
1119 CallingConv::ID CallConv, bool isVarArg,
1120 const SmallVectorImpl<ISD::InputArg> &Ins,
1121 DebugLoc dl, SelectionDAG &DAG,
1122 SmallVectorImpl<SDValue> &InVals) {
1123 assert(0 && "Not Implemented");
1124 return SDValue(); // this is here to silence compiler errors
1127 /// LowerCallTo - This function lowers an abstract call to a function into an
1128 /// actual call. This returns a pair of operands. The first element is the
1129 /// return value for the function (if RetTy is not VoidTy). The second
1130 /// element is the outgoing token chain. It calls LowerCall to do the actual
1132 struct ArgListEntry {
1143 ArgListEntry() : isSExt(false), isZExt(false), isInReg(false),
1144 isSRet(false), isNest(false), isByVal(false), Alignment(0) { }
1146 typedef std::vector<ArgListEntry> ArgListTy;
1147 std::pair<SDValue, SDValue>
1148 LowerCallTo(SDValue Chain, const Type *RetTy, bool RetSExt, bool RetZExt,
1149 bool isVarArg, bool isInreg, unsigned NumFixedArgs,
1150 CallingConv::ID CallConv, bool isTailCall,
1151 bool isReturnValueUsed, SDValue Callee, ArgListTy &Args,
1152 SelectionDAG &DAG, DebugLoc dl, unsigned Order);
1154 /// LowerCall - This hook must be implemented to lower calls into the
1155 /// the specified DAG. The outgoing arguments to the call are described
1156 /// by the Outs array, and the values to be returned by the call are
1157 /// described by the Ins array. The implementation should fill in the
1158 /// InVals array with legal-type return values from the call, and return
1159 /// the resulting token chain value.
1161 /// The isTailCall flag here is normative. If it is true, the
1162 /// implementation must emit a tail call. The
1163 /// IsEligibleForTailCallOptimization hook should be used to catch
1164 /// cases that cannot be handled.
1167 LowerCall(SDValue Chain, SDValue Callee,
1168 CallingConv::ID CallConv, bool isVarArg, bool isTailCall,
1169 const SmallVectorImpl<ISD::OutputArg> &Outs,
1170 const SmallVectorImpl<ISD::InputArg> &Ins,
1171 DebugLoc dl, SelectionDAG &DAG,
1172 SmallVectorImpl<SDValue> &InVals) {
1173 assert(0 && "Not Implemented");
1174 return SDValue(); // this is here to silence compiler errors
1177 /// CanLowerReturn - This hook should be implemented to check whether the
1178 /// return values described by the Outs array can fit into the return
1179 /// registers. If false is returned, an sret-demotion is performed.
1181 virtual bool CanLowerReturn(CallingConv::ID CallConv, bool isVarArg,
1182 const SmallVectorImpl<EVT> &OutTys,
1183 const SmallVectorImpl<ISD::ArgFlagsTy> &ArgsFlags,
1186 // Return true by default to get preexisting behavior.
1189 /// LowerReturn - This hook must be implemented to lower outgoing
1190 /// return values, described by the Outs array, into the specified
1191 /// DAG. The implementation should return the resulting token chain
1195 LowerReturn(SDValue Chain, CallingConv::ID CallConv, bool isVarArg,
1196 const SmallVectorImpl<ISD::OutputArg> &Outs,
1197 DebugLoc dl, SelectionDAG &DAG) {
1198 assert(0 && "Not Implemented");
1199 return SDValue(); // this is here to silence compiler errors
1202 /// EmitTargetCodeForMemcpy - Emit target-specific code that performs a
1203 /// memcpy. This can be used by targets to provide code sequences for cases
1204 /// that don't fit the target's parameters for simple loads/stores and can be
1205 /// more efficient than using a library call. This function can return a null
1206 /// SDValue if the target declines to use custom code and a different
1207 /// lowering strategy should be used.
1209 /// If AlwaysInline is true, the size is constant and the target should not
1210 /// emit any calls and is strongly encouraged to attempt to emit inline code
1211 /// even if it is beyond the usual threshold because this intrinsic is being
1212 /// expanded in a place where calls are not feasible (e.g. within the prologue
1213 /// for another call). If the target chooses to decline an AlwaysInline
1214 /// request here, legalize will resort to using simple loads and stores.
1216 EmitTargetCodeForMemcpy(SelectionDAG &DAG, DebugLoc dl,
1218 SDValue Op1, SDValue Op2,
1219 SDValue Op3, unsigned Align,
1221 const Value *DstSV, uint64_t DstOff,
1222 const Value *SrcSV, uint64_t SrcOff) {
1226 /// EmitTargetCodeForMemmove - Emit target-specific code that performs a
1227 /// memmove. This can be used by targets to provide code sequences for cases
1228 /// that don't fit the target's parameters for simple loads/stores and can be
1229 /// more efficient than using a library call. This function can return a null
1230 /// SDValue if the target declines to use custom code and a different
1231 /// lowering strategy should be used.
1233 EmitTargetCodeForMemmove(SelectionDAG &DAG, DebugLoc dl,
1235 SDValue Op1, SDValue Op2,
1236 SDValue Op3, unsigned Align,
1237 const Value *DstSV, uint64_t DstOff,
1238 const Value *SrcSV, uint64_t SrcOff) {
1242 /// EmitTargetCodeForMemset - Emit target-specific code that performs a
1243 /// memset. This can be used by targets to provide code sequences for cases
1244 /// that don't fit the target's parameters for simple stores and can be more
1245 /// efficient than using a library call. This function can return a null
1246 /// SDValue if the target declines to use custom code and a different
1247 /// lowering strategy should be used.
1249 EmitTargetCodeForMemset(SelectionDAG &DAG, DebugLoc dl,
1251 SDValue Op1, SDValue Op2,
1252 SDValue Op3, unsigned Align,
1253 const Value *DstSV, uint64_t DstOff) {
1257 /// LowerOperationWrapper - This callback is invoked by the type legalizer
1258 /// to legalize nodes with an illegal operand type but legal result types.
1259 /// It replaces the LowerOperation callback in the type Legalizer.
1260 /// The reason we can not do away with LowerOperation entirely is that
1261 /// LegalizeDAG isn't yet ready to use this callback.
1262 /// TODO: Consider merging with ReplaceNodeResults.
1264 /// The target places new result values for the node in Results (their number
1265 /// and types must exactly match those of the original return values of
1266 /// the node), or leaves Results empty, which indicates that the node is not
1267 /// to be custom lowered after all.
1268 /// The default implementation calls LowerOperation.
1269 virtual void LowerOperationWrapper(SDNode *N,
1270 SmallVectorImpl<SDValue> &Results,
1273 /// LowerOperation - This callback is invoked for operations that are
1274 /// unsupported by the target, which are registered to use 'custom' lowering,
1275 /// and whose defined values are all legal.
1276 /// If the target has no operations that require custom lowering, it need not
1277 /// implement this. The default implementation of this aborts.
1278 virtual SDValue LowerOperation(SDValue Op, SelectionDAG &DAG);
1280 /// ReplaceNodeResults - This callback is invoked when a node result type is
1281 /// illegal for the target, and the operation was registered to use 'custom'
1282 /// lowering for that result type. The target places new result values for
1283 /// the node in Results (their number and types must exactly match those of
1284 /// the original return values of the node), or leaves Results empty, which
1285 /// indicates that the node is not to be custom lowered after all.
1287 /// If the target has no operations that require custom lowering, it need not
1288 /// implement this. The default implementation aborts.
1289 virtual void ReplaceNodeResults(SDNode *N, SmallVectorImpl<SDValue> &Results,
1290 SelectionDAG &DAG) {
1291 assert(0 && "ReplaceNodeResults not implemented for this target!");
1294 /// IsEligibleForTailCallOptimization - Check whether the call is eligible for
1295 /// tail call optimization. Targets which want to do tail call optimization
1296 /// should override this function.
1298 IsEligibleForTailCallOptimization(SDValue Callee,
1299 CallingConv::ID CalleeCC,
1301 const SmallVectorImpl<ISD::InputArg> &Ins,
1302 SelectionDAG& DAG) const {
1303 // Conservative default: no calls are eligible.
1307 /// getTargetNodeName() - This method returns the name of a target specific
1309 virtual const char *getTargetNodeName(unsigned Opcode) const;
1311 /// createFastISel - This method returns a target specific FastISel object,
1312 /// or null if the target does not support "fast" ISel.
1314 createFastISel(MachineFunction &,
1315 MachineModuleInfo *, DwarfWriter *,
1316 DenseMap<const Value *, unsigned> &,
1317 DenseMap<const BasicBlock *, MachineBasicBlock *> &,
1318 DenseMap<const AllocaInst *, int> &
1320 , SmallSet<Instruction*, 8> &CatchInfoLost
1326 //===--------------------------------------------------------------------===//
1327 // Inline Asm Support hooks
1330 /// ExpandInlineAsm - This hook allows the target to expand an inline asm
1331 /// call to be explicit llvm code if it wants to. This is useful for
1332 /// turning simple inline asms into LLVM intrinsics, which gives the
1333 /// compiler more information about the behavior of the code.
1334 virtual bool ExpandInlineAsm(CallInst *CI) const {
1338 enum ConstraintType {
1339 C_Register, // Constraint represents specific register(s).
1340 C_RegisterClass, // Constraint represents any of register(s) in class.
1341 C_Memory, // Memory constraint.
1342 C_Other, // Something else.
1343 C_Unknown // Unsupported constraint.
1346 /// AsmOperandInfo - This contains information for each constraint that we are
1348 struct AsmOperandInfo : public InlineAsm::ConstraintInfo {
1349 /// ConstraintCode - This contains the actual string for the code, like "m".
1350 /// TargetLowering picks the 'best' code from ConstraintInfo::Codes that
1351 /// most closely matches the operand.
1352 std::string ConstraintCode;
1354 /// ConstraintType - Information about the constraint code, e.g. Register,
1355 /// RegisterClass, Memory, Other, Unknown.
1356 TargetLowering::ConstraintType ConstraintType;
1358 /// CallOperandval - If this is the result output operand or a
1359 /// clobber, this is null, otherwise it is the incoming operand to the
1360 /// CallInst. This gets modified as the asm is processed.
1361 Value *CallOperandVal;
1363 /// ConstraintVT - The ValueType for the operand value.
1366 /// isMatchingInputConstraint - Return true of this is an input operand that
1367 /// is a matching constraint like "4".
1368 bool isMatchingInputConstraint() const;
1370 /// getMatchedOperand - If this is an input matching constraint, this method
1371 /// returns the output operand it matches.
1372 unsigned getMatchedOperand() const;
1374 AsmOperandInfo(const InlineAsm::ConstraintInfo &info)
1375 : InlineAsm::ConstraintInfo(info),
1376 ConstraintType(TargetLowering::C_Unknown),
1377 CallOperandVal(0), ConstraintVT(MVT::Other) {
1381 /// ComputeConstraintToUse - Determines the constraint code and constraint
1382 /// type to use for the specific AsmOperandInfo, setting
1383 /// OpInfo.ConstraintCode and OpInfo.ConstraintType. If the actual operand
1384 /// being passed in is available, it can be passed in as Op, otherwise an
1385 /// empty SDValue can be passed. If hasMemory is true it means one of the asm
1386 /// constraint of the inline asm instruction being processed is 'm'.
1387 virtual void ComputeConstraintToUse(AsmOperandInfo &OpInfo,
1390 SelectionDAG *DAG = 0) const;
1392 /// getConstraintType - Given a constraint, return the type of constraint it
1393 /// is for this target.
1394 virtual ConstraintType getConstraintType(const std::string &Constraint) const;
1396 /// getRegClassForInlineAsmConstraint - Given a constraint letter (e.g. "r"),
1397 /// return a list of registers that can be used to satisfy the constraint.
1398 /// This should only be used for C_RegisterClass constraints.
1399 virtual std::vector<unsigned>
1400 getRegClassForInlineAsmConstraint(const std::string &Constraint,
1403 /// getRegForInlineAsmConstraint - Given a physical register constraint (e.g.
1404 /// {edx}), return the register number and the register class for the
1407 /// Given a register class constraint, like 'r', if this corresponds directly
1408 /// to an LLVM register class, return a register of 0 and the register class
1411 /// This should only be used for C_Register constraints. On error,
1412 /// this returns a register number of 0 and a null register class pointer..
1413 virtual std::pair<unsigned, const TargetRegisterClass*>
1414 getRegForInlineAsmConstraint(const std::string &Constraint,
1417 /// LowerXConstraint - try to replace an X constraint, which matches anything,
1418 /// with another that has more specific requirements based on the type of the
1419 /// corresponding operand. This returns null if there is no replacement to
1421 virtual const char *LowerXConstraint(EVT ConstraintVT) const;
1423 /// LowerAsmOperandForConstraint - Lower the specified operand into the Ops
1424 /// vector. If it is invalid, don't add anything to Ops. If hasMemory is true
1425 /// it means one of the asm constraint of the inline asm instruction being
1426 /// processed is 'm'.
1427 virtual void LowerAsmOperandForConstraint(SDValue Op, char ConstraintLetter,
1429 std::vector<SDValue> &Ops,
1430 SelectionDAG &DAG) const;
1432 //===--------------------------------------------------------------------===//
1433 // Instruction Emitting Hooks
1436 // EmitInstrWithCustomInserter - This method should be implemented by targets
1437 // that mark instructions with the 'usesCustomInserter' flag. These
1438 // instructions are special in various ways, which require special support to
1439 // insert. The specified MachineInstr is created but not inserted into any
1440 // basic blocks, and this method is called to expand it into a sequence of
1441 // instructions, potentially also creating new basic blocks and control flow.
1442 // When new basic blocks are inserted and the edges from MBB to its successors
1443 // are modified, the method should insert pairs of <OldSucc, NewSucc> into the
1445 virtual MachineBasicBlock *EmitInstrWithCustomInserter(MachineInstr *MI,
1446 MachineBasicBlock *MBB,
1447 DenseMap<MachineBasicBlock*, MachineBasicBlock*> *EM) const;
1449 //===--------------------------------------------------------------------===//
1450 // Addressing mode description hooks (used by LSR etc).
1453 /// AddrMode - This represents an addressing mode of:
1454 /// BaseGV + BaseOffs + BaseReg + Scale*ScaleReg
1455 /// If BaseGV is null, there is no BaseGV.
1456 /// If BaseOffs is zero, there is no base offset.
1457 /// If HasBaseReg is false, there is no base register.
1458 /// If Scale is zero, there is no ScaleReg. Scale of 1 indicates a reg with
1462 GlobalValue *BaseGV;
1466 AddrMode() : BaseGV(0), BaseOffs(0), HasBaseReg(false), Scale(0) {}
1469 /// isLegalAddressingMode - Return true if the addressing mode represented by
1470 /// AM is legal for this target, for a load/store of the specified type.
1471 /// The type may be VoidTy, in which case only return true if the addressing
1472 /// mode is legal for a load/store of any legal type.
1473 /// TODO: Handle pre/postinc as well.
1474 virtual bool isLegalAddressingMode(const AddrMode &AM, const Type *Ty) const;
1476 /// isTruncateFree - Return true if it's free to truncate a value of
1477 /// type Ty1 to type Ty2. e.g. On x86 it's free to truncate a i32 value in
1478 /// register EAX to i16 by referencing its sub-register AX.
1479 virtual bool isTruncateFree(const Type *Ty1, const Type *Ty2) const {
1483 virtual bool isTruncateFree(EVT VT1, EVT VT2) const {
1487 /// isZExtFree - Return true if any actual instruction that defines a
1488 /// value of type Ty1 implicitly zero-extends the value to Ty2 in the result
1489 /// register. This does not necessarily include registers defined in
1490 /// unknown ways, such as incoming arguments, or copies from unknown
1491 /// virtual registers. Also, if isTruncateFree(Ty2, Ty1) is true, this
1492 /// does not necessarily apply to truncate instructions. e.g. on x86-64,
1493 /// all instructions that define 32-bit values implicit zero-extend the
1494 /// result out to 64 bits.
1495 virtual bool isZExtFree(const Type *Ty1, const Type *Ty2) const {
1499 virtual bool isZExtFree(EVT VT1, EVT VT2) const {
1503 /// isNarrowingProfitable - Return true if it's profitable to narrow
1504 /// operations of type VT1 to VT2. e.g. on x86, it's profitable to narrow
1505 /// from i32 to i8 but not from i32 to i16.
1506 virtual bool isNarrowingProfitable(EVT VT1, EVT VT2) const {
1510 /// isLegalICmpImmediate - Return true if the specified immediate is legal
1511 /// icmp immediate, that is the target has icmp instructions which can compare
1512 /// a register against the immediate without having to materialize the
1513 /// immediate into a register.
1514 virtual bool isLegalICmpImmediate(int64_t Imm) const {
1518 //===--------------------------------------------------------------------===//
1519 // Div utility functions
1521 SDValue BuildSDIV(SDNode *N, SelectionDAG &DAG,
1522 std::vector<SDNode*>* Created) const;
1523 SDValue BuildUDIV(SDNode *N, SelectionDAG &DAG,
1524 std::vector<SDNode*>* Created) const;
1527 //===--------------------------------------------------------------------===//
1528 // Runtime Library hooks
1531 /// setLibcallName - Rename the default libcall routine name for the specified
1533 void setLibcallName(RTLIB::Libcall Call, const char *Name) {
1534 LibcallRoutineNames[Call] = Name;
1537 /// getLibcallName - Get the libcall routine name for the specified libcall.
1539 const char *getLibcallName(RTLIB::Libcall Call) const {
1540 return LibcallRoutineNames[Call];
1543 /// setCmpLibcallCC - Override the default CondCode to be used to test the
1544 /// result of the comparison libcall against zero.
1545 void setCmpLibcallCC(RTLIB::Libcall Call, ISD::CondCode CC) {
1546 CmpLibcallCCs[Call] = CC;
1549 /// getCmpLibcallCC - Get the CondCode that's to be used to test the result of
1550 /// the comparison libcall against zero.
1551 ISD::CondCode getCmpLibcallCC(RTLIB::Libcall Call) const {
1552 return CmpLibcallCCs[Call];
1555 /// setLibcallCallingConv - Set the CallingConv that should be used for the
1556 /// specified libcall.
1557 void setLibcallCallingConv(RTLIB::Libcall Call, CallingConv::ID CC) {
1558 LibcallCallingConvs[Call] = CC;
1561 /// getLibcallCallingConv - Get the CallingConv that should be used for the
1562 /// specified libcall.
1563 CallingConv::ID getLibcallCallingConv(RTLIB::Libcall Call) const {
1564 return LibcallCallingConvs[Call];
1569 const TargetData *TD;
1570 TargetLoweringObjectFile &TLOF;
1572 /// PointerTy - The type to use for pointers, usually i32 or i64.
1576 /// IsLittleEndian - True if this is a little endian target.
1578 bool IsLittleEndian;
1580 /// UsesGlobalOffsetTable - True if this target uses a GOT for PIC codegen.
1582 bool UsesGlobalOffsetTable;
1584 /// SelectIsExpensive - Tells the code generator not to expand operations
1585 /// into sequences that use the select operations if possible.
1586 bool SelectIsExpensive;
1588 /// IntDivIsCheap - Tells the code generator not to expand integer divides by
1589 /// constants into a sequence of muls, adds, and shifts. This is a hack until
1590 /// a real cost model is in place. If we ever optimize for size, this will be
1591 /// set to true unconditionally.
1594 /// Pow2DivIsCheap - Tells the code generator that it shouldn't generate
1595 /// srl/add/sra for a signed divide by power of two, and let the target handle
1597 bool Pow2DivIsCheap;
1599 /// UseUnderscoreSetJmp - This target prefers to use _setjmp to implement
1600 /// llvm.setjmp. Defaults to false.
1601 bool UseUnderscoreSetJmp;
1603 /// UseUnderscoreLongJmp - This target prefers to use _longjmp to implement
1604 /// llvm.longjmp. Defaults to false.
1605 bool UseUnderscoreLongJmp;
1607 /// ShiftAmountTy - The type to use for shift amounts, usually i8 or whatever
1611 /// BooleanContents - Information about the contents of the high-bits in
1612 /// boolean values held in a type wider than i1. See getBooleanContents.
1613 BooleanContent BooleanContents;
1615 /// SchedPreferenceInfo - The target scheduling preference: shortest possible
1616 /// total cycles or lowest register usage.
1617 SchedPreference SchedPreferenceInfo;
1619 /// JumpBufSize - The size, in bytes, of the target's jmp_buf buffers
1620 unsigned JumpBufSize;
1622 /// JumpBufAlignment - The alignment, in bytes, of the target's jmp_buf
1624 unsigned JumpBufAlignment;
1626 /// IfCvtBlockSizeLimit - The maximum allowed size for a block to be
1628 unsigned IfCvtBlockSizeLimit;
1630 /// IfCvtDupBlockSizeLimit - The maximum allowed size for a block to be
1631 /// duplicated during if-conversion.
1632 unsigned IfCvtDupBlockSizeLimit;
1634 /// PrefLoopAlignment - The perferred loop alignment.
1636 unsigned PrefLoopAlignment;
1638 /// StackPointerRegisterToSaveRestore - If set to a physical register, this
1639 /// specifies the register that llvm.savestack/llvm.restorestack should save
1641 unsigned StackPointerRegisterToSaveRestore;
1643 /// ExceptionPointerRegister - If set to a physical register, this specifies
1644 /// the register that receives the exception address on entry to a landing
1646 unsigned ExceptionPointerRegister;
1648 /// ExceptionSelectorRegister - If set to a physical register, this specifies
1649 /// the register that receives the exception typeid on entry to a landing
1651 unsigned ExceptionSelectorRegister;
1653 /// RegClassForVT - This indicates the default register class to use for
1654 /// each ValueType the target supports natively.
1655 TargetRegisterClass *RegClassForVT[MVT::LAST_VALUETYPE];
1656 unsigned char NumRegistersForVT[MVT::LAST_VALUETYPE];
1657 EVT RegisterTypeForVT[MVT::LAST_VALUETYPE];
1659 /// TransformToType - For any value types we are promoting or expanding, this
1660 /// contains the value type that we are changing to. For Expanded types, this
1661 /// contains one step of the expand (e.g. i64 -> i32), even if there are
1662 /// multiple steps required (e.g. i64 -> i16). For types natively supported
1663 /// by the system, this holds the same type (e.g. i32 -> i32).
1664 EVT TransformToType[MVT::LAST_VALUETYPE];
1666 /// OpActions - For each operation and each value type, keep a LegalizeAction
1667 /// that indicates how instruction selection should deal with the operation.
1668 /// Most operations are Legal (aka, supported natively by the target), but
1669 /// operations that are not should be described. Note that operations on
1670 /// non-legal value types are not described here.
1671 /// This array is accessed using VT.getSimpleVT(), so it is subject to
1672 /// the MVT::MAX_ALLOWED_VALUETYPE * 2 bits.
1673 uint64_t OpActions[MVT::MAX_ALLOWED_VALUETYPE/(sizeof(uint64_t)*4)][ISD::BUILTIN_OP_END];
1675 /// LoadExtActions - For each load of load extension type and each value type,
1676 /// keep a LegalizeAction that indicates how instruction selection should deal
1678 uint64_t LoadExtActions[ISD::LAST_LOADEXT_TYPE];
1680 /// TruncStoreActions - For each truncating store, keep a LegalizeAction that
1681 /// indicates how instruction selection should deal with the store.
1682 uint64_t TruncStoreActions[MVT::LAST_VALUETYPE];
1684 /// IndexedModeActions - For each indexed mode and each value type,
1685 /// keep a pair of LegalizeAction that indicates how instruction
1686 /// selection should deal with the load / store. The first
1687 /// dimension is now the value_type for the reference. The second
1688 /// dimension is the load [0] vs. store[1]. The third dimension
1689 /// represents the various modes for load store.
1690 uint8_t IndexedModeActions[MVT::LAST_VALUETYPE][2][ISD::LAST_INDEXED_MODE];
1692 /// ConvertActions - For each conversion from source type to destination type,
1693 /// keep a LegalizeAction that indicates how instruction selection should
1694 /// deal with the conversion.
1695 /// Currently, this is used only for floating->floating conversions
1696 /// (FP_EXTEND and FP_ROUND).
1697 uint64_t ConvertActions[MVT::LAST_VALUETYPE];
1699 /// CondCodeActions - For each condition code (ISD::CondCode) keep a
1700 /// LegalizeAction that indicates how instruction selection should
1701 /// deal with the condition code.
1702 uint64_t CondCodeActions[ISD::SETCC_INVALID];
1704 ValueTypeActionImpl ValueTypeActions;
1706 std::vector<std::pair<EVT, TargetRegisterClass*> > AvailableRegClasses;
1708 /// TargetDAGCombineArray - Targets can specify ISD nodes that they would
1709 /// like PerformDAGCombine callbacks for by calling setTargetDAGCombine(),
1710 /// which sets a bit in this array.
1712 TargetDAGCombineArray[(ISD::BUILTIN_OP_END+CHAR_BIT-1)/CHAR_BIT];
1714 /// PromoteToType - For operations that must be promoted to a specific type,
1715 /// this holds the destination type. This map should be sparse, so don't hold
1718 /// Targets add entries to this map with AddPromotedToType(..), clients access
1719 /// this with getTypeToPromoteTo(..).
1720 std::map<std::pair<unsigned, MVT::SimpleValueType>, MVT::SimpleValueType>
1723 /// LibcallRoutineNames - Stores the name each libcall.
1725 const char *LibcallRoutineNames[RTLIB::UNKNOWN_LIBCALL];
1727 /// CmpLibcallCCs - The ISD::CondCode that should be used to test the result
1728 /// of each of the comparison libcall against zero.
1729 ISD::CondCode CmpLibcallCCs[RTLIB::UNKNOWN_LIBCALL];
1731 /// LibcallCallingConvs - Stores the CallingConv that should be used for each
1733 CallingConv::ID LibcallCallingConvs[RTLIB::UNKNOWN_LIBCALL];
1736 /// When lowering \@llvm.memset this field specifies the maximum number of
1737 /// store operations that may be substituted for the call to memset. Targets
1738 /// must set this value based on the cost threshold for that target. Targets
1739 /// should assume that the memset will be done using as many of the largest
1740 /// store operations first, followed by smaller ones, if necessary, per
1741 /// alignment restrictions. For example, storing 9 bytes on a 32-bit machine
1742 /// with 16-bit alignment would result in four 2-byte stores and one 1-byte
1743 /// store. This only applies to setting a constant array of a constant size.
1744 /// @brief Specify maximum number of store instructions per memset call.
1745 unsigned maxStoresPerMemset;
1747 /// When lowering \@llvm.memcpy this field specifies the maximum number of
1748 /// store operations that may be substituted for a call to memcpy. Targets
1749 /// must set this value based on the cost threshold for that target. Targets
1750 /// should assume that the memcpy will be done using as many of the largest
1751 /// store operations first, followed by smaller ones, if necessary, per
1752 /// alignment restrictions. For example, storing 7 bytes on a 32-bit machine
1753 /// with 32-bit alignment would result in one 4-byte store, a one 2-byte store
1754 /// and one 1-byte store. This only applies to copying a constant array of
1756 /// @brief Specify maximum bytes of store instructions per memcpy call.
1757 unsigned maxStoresPerMemcpy;
1759 /// When lowering \@llvm.memmove this field specifies the maximum number of
1760 /// store instructions that may be substituted for a call to memmove. Targets
1761 /// must set this value based on the cost threshold for that target. Targets
1762 /// should assume that the memmove will be done using as many of the largest
1763 /// store operations first, followed by smaller ones, if necessary, per
1764 /// alignment restrictions. For example, moving 9 bytes on a 32-bit machine
1765 /// with 8-bit alignment would result in nine 1-byte stores. This only
1766 /// applies to copying a constant array of constant size.
1767 /// @brief Specify maximum bytes of store instructions per memmove call.
1768 unsigned maxStoresPerMemmove;
1770 /// This field specifies whether the target can benefit from code placement
1772 bool benefitFromCodePlacementOpt;
1774 } // end llvm namespace