1 //===-- llvm/Target/TargetLowering.h - Target Lowering Info -----*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file was developed by the LLVM research group and is distributed under
6 // the University of Illinois Open Source 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/CodeGen/SelectionDAGNodes.h"
26 #include "llvm/CodeGen/RuntimeLibcalls.h"
27 #include "llvm/ADT/APFloat.h"
28 #include "llvm/ADT/STLExtras.h"
37 class TargetRegisterClass;
41 class MachineBasicBlock;
44 class TargetSubtarget;
46 //===----------------------------------------------------------------------===//
47 /// TargetLowering - This class defines information used to lower LLVM code to
48 /// legal SelectionDAG operators that the target instruction selector can accept
51 /// This class also defines callbacks that targets must implement to lower
52 /// target-specific constructs to SelectionDAG operators.
54 class TargetLowering {
56 /// LegalizeAction - This enum indicates whether operations are valid for a
57 /// target, and if not, what action should be used to make them valid.
59 Legal, // The target natively supports this operation.
60 Promote, // This operation should be executed in a larger type.
61 Expand, // Try to expand this to other ops, otherwise use a libcall.
62 Custom // Use the LowerOperation hook to implement custom lowering.
65 enum OutOfRangeShiftAmount {
66 Undefined, // Oversized shift amounts are undefined (default).
67 Mask, // Shift amounts are auto masked (anded) to value size.
68 Extend // Oversized shift pulls in zeros or sign bits.
71 enum SetCCResultValue {
72 UndefinedSetCCResult, // SetCC returns a garbage/unknown extend.
73 ZeroOrOneSetCCResult, // SetCC returns a zero extended result.
74 ZeroOrNegativeOneSetCCResult // SetCC returns a sign extended result.
77 enum SchedPreference {
78 SchedulingForLatency, // Scheduling for shortest total latency.
79 SchedulingForRegPressure // Scheduling for lowest register pressure.
82 explicit TargetLowering(TargetMachine &TM);
83 virtual ~TargetLowering();
85 TargetMachine &getTargetMachine() const { return TM; }
86 const TargetData *getTargetData() const { return TD; }
88 bool isLittleEndian() const { return IsLittleEndian; }
89 MVT::ValueType getPointerTy() const { return PointerTy; }
90 MVT::ValueType getShiftAmountTy() const { return ShiftAmountTy; }
91 OutOfRangeShiftAmount getShiftAmountFlavor() const {return ShiftAmtHandling; }
93 /// usesGlobalOffsetTable - Return true if this target uses a GOT for PIC
95 bool usesGlobalOffsetTable() const { return UsesGlobalOffsetTable; }
97 /// isSelectExpensive - Return true if the select operation is expensive for
99 bool isSelectExpensive() const { return SelectIsExpensive; }
101 /// isIntDivCheap() - Return true if integer divide is usually cheaper than
102 /// a sequence of several shifts, adds, and multiplies for this target.
103 bool isIntDivCheap() const { return IntDivIsCheap; }
105 /// isPow2DivCheap() - Return true if pow2 div is cheaper than a chain of
107 bool isPow2DivCheap() const { return Pow2DivIsCheap; }
109 /// getSetCCResultTy - Return the ValueType of the result of setcc operations.
111 MVT::ValueType getSetCCResultTy() const { return SetCCResultTy; }
113 /// getSetCCResultContents - For targets without boolean registers, this flag
114 /// returns information about the contents of the high-bits in the setcc
116 SetCCResultValue getSetCCResultContents() const { return SetCCResultContents;}
118 /// getSchedulingPreference - Return target scheduling preference.
119 SchedPreference getSchedulingPreference() const {
120 return SchedPreferenceInfo;
123 /// getRegClassFor - Return the register class that should be used for the
124 /// specified value type. This may only be called on legal types.
125 TargetRegisterClass *getRegClassFor(MVT::ValueType VT) const {
126 assert(!MVT::isExtendedVT(VT));
127 TargetRegisterClass *RC = RegClassForVT[VT];
128 assert(RC && "This value type is not natively supported!");
132 /// isTypeLegal - Return true if the target has native support for the
133 /// specified value type. This means that it has a register that directly
134 /// holds it without promotions or expansions.
135 bool isTypeLegal(MVT::ValueType VT) const {
136 return !MVT::isExtendedVT(VT) && RegClassForVT[VT] != 0;
139 class ValueTypeActionImpl {
140 /// ValueTypeActions - This is a bitvector that contains two bits for each
141 /// value type, where the two bits correspond to the LegalizeAction enum.
142 /// This can be queried with "getTypeAction(VT)".
143 uint32_t ValueTypeActions[2];
145 ValueTypeActionImpl() {
146 ValueTypeActions[0] = ValueTypeActions[1] = 0;
148 ValueTypeActionImpl(const ValueTypeActionImpl &RHS) {
149 ValueTypeActions[0] = RHS.ValueTypeActions[0];
150 ValueTypeActions[1] = RHS.ValueTypeActions[1];
153 LegalizeAction getTypeAction(MVT::ValueType VT) const {
154 if (MVT::isExtendedVT(VT)) {
155 if (MVT::isVector(VT)) return Expand;
156 if (MVT::isInteger(VT))
157 // First promote to a power-of-two size, then expand if necessary.
158 return VT == MVT::RoundIntegerType(VT) ? Expand : Promote;
159 assert(0 && "Unsupported extended type!");
161 return (LegalizeAction)((ValueTypeActions[VT>>4] >> ((2*VT) & 31)) & 3);
163 void setTypeAction(MVT::ValueType VT, LegalizeAction Action) {
164 assert(!MVT::isExtendedVT(VT));
165 assert(unsigned(VT >> 4) < array_lengthof(ValueTypeActions));
166 ValueTypeActions[VT>>4] |= Action << ((VT*2) & 31);
170 const ValueTypeActionImpl &getValueTypeActions() const {
171 return ValueTypeActions;
174 /// getTypeAction - Return how we should legalize values of this type, either
175 /// it is already legal (return 'Legal') or we need to promote it to a larger
176 /// type (return 'Promote'), or we need to expand it into multiple registers
177 /// of smaller integer type (return 'Expand'). 'Custom' is not an option.
178 LegalizeAction getTypeAction(MVT::ValueType VT) const {
179 return ValueTypeActions.getTypeAction(VT);
182 /// getTypeToTransformTo - For types supported by the target, this is an
183 /// identity function. For types that must be promoted to larger types, this
184 /// returns the larger type to promote to. For integer types that are larger
185 /// than the largest integer register, this contains one step in the expansion
186 /// to get to the smaller register. For illegal floating point types, this
187 /// returns the integer type to transform to.
188 MVT::ValueType getTypeToTransformTo(MVT::ValueType VT) const {
189 if (!MVT::isExtendedVT(VT)) {
190 MVT::ValueType NVT = TransformToType[VT];
191 assert(getTypeAction(NVT) != Promote &&
192 "Promote may not follow Expand or Promote");
196 if (MVT::isVector(VT))
197 return MVT::getVectorType(MVT::getVectorElementType(VT),
198 MVT::getVectorNumElements(VT) / 2);
199 if (MVT::isInteger(VT)) {
200 MVT::ValueType NVT = MVT::RoundIntegerType(VT);
202 // Size is a power of two - expand to half the size.
203 return MVT::getIntegerType(MVT::getSizeInBits(VT) / 2);
205 // Promote to a power of two size, avoiding multi-step promotion.
206 return getTypeAction(NVT) == Promote ? getTypeToTransformTo(NVT) : NVT;
208 assert(0 && "Unsupported extended type!");
211 /// getTypeToExpandTo - For types supported by the target, this is an
212 /// identity function. For types that must be expanded (i.e. integer types
213 /// that are larger than the largest integer register or illegal floating
214 /// point types), this returns the largest legal type it will be expanded to.
215 MVT::ValueType getTypeToExpandTo(MVT::ValueType VT) const {
216 assert(!MVT::isVector(VT));
218 switch (getTypeAction(VT)) {
222 VT = getTypeToTransformTo(VT);
225 assert(false && "Type is not legal nor is it to be expanded!");
232 /// getVectorTypeBreakdown - Vector types are broken down into some number of
233 /// legal first class types. For example, MVT::v8f32 maps to 2 MVT::v4f32
234 /// with Altivec or SSE1, or 8 promoted MVT::f64 values with the X86 FP stack.
235 /// Similarly, MVT::v2i64 turns into 4 MVT::i32 values with both PPC and X86.
237 /// This method returns the number of registers needed, and the VT for each
238 /// register. It also returns the VT and quantity of the intermediate values
239 /// before they are promoted/expanded.
241 unsigned getVectorTypeBreakdown(MVT::ValueType VT,
242 MVT::ValueType &IntermediateVT,
243 unsigned &NumIntermediates,
244 MVT::ValueType &RegisterVT) const;
246 typedef std::vector<APFloat>::const_iterator legal_fpimm_iterator;
247 legal_fpimm_iterator legal_fpimm_begin() const {
248 return LegalFPImmediates.begin();
250 legal_fpimm_iterator legal_fpimm_end() const {
251 return LegalFPImmediates.end();
254 /// isShuffleMaskLegal - Targets can use this to indicate that they only
255 /// support *some* VECTOR_SHUFFLE operations, those with specific masks.
256 /// By default, if a target supports the VECTOR_SHUFFLE node, all mask values
257 /// are assumed to be legal.
258 virtual bool isShuffleMaskLegal(SDOperand Mask, MVT::ValueType VT) const {
262 /// isVectorClearMaskLegal - Similar to isShuffleMaskLegal. This is
263 /// used by Targets can use this to indicate if there is a suitable
264 /// VECTOR_SHUFFLE that can be used to replace a VAND with a constant
266 virtual bool isVectorClearMaskLegal(std::vector<SDOperand> &BVOps,
268 SelectionDAG &DAG) const {
272 /// getOperationAction - Return how this operation should be treated: either
273 /// it is legal, needs to be promoted to a larger size, needs to be
274 /// expanded to some other code sequence, or the target has a custom expander
276 LegalizeAction getOperationAction(unsigned Op, MVT::ValueType VT) const {
277 if (MVT::isExtendedVT(VT)) return Expand;
278 return (LegalizeAction)((OpActions[Op] >> (2*VT)) & 3);
281 /// isOperationLegal - Return true if the specified operation is legal on this
283 bool isOperationLegal(unsigned Op, MVT::ValueType VT) const {
284 return getOperationAction(Op, VT) == Legal ||
285 getOperationAction(Op, VT) == Custom;
288 /// getLoadXAction - Return how this load with extension should be treated:
289 /// either it is legal, needs to be promoted to a larger size, needs to be
290 /// expanded to some other code sequence, or the target has a custom expander
292 LegalizeAction getLoadXAction(unsigned LType, MVT::ValueType VT) const {
293 if (MVT::isExtendedVT(VT)) return getTypeAction(VT);
294 return (LegalizeAction)((LoadXActions[LType] >> (2*VT)) & 3);
297 /// isLoadXLegal - Return true if the specified load with extension is legal
299 bool isLoadXLegal(unsigned LType, MVT::ValueType VT) const {
300 return getLoadXAction(LType, VT) == Legal ||
301 getLoadXAction(LType, VT) == Custom;
304 /// getStoreXAction - Return how this store with truncation should be treated:
305 /// either it is legal, needs to be promoted to a larger size, needs to be
306 /// expanded to some other code sequence, or the target has a custom expander
308 LegalizeAction getStoreXAction(MVT::ValueType VT) const {
309 if (MVT::isExtendedVT(VT)) return getTypeAction(VT);
310 return (LegalizeAction)((StoreXActions >> (2*VT)) & 3);
313 /// isStoreXLegal - Return true if the specified store with truncation is
314 /// legal on this target.
315 bool isStoreXLegal(MVT::ValueType VT) const {
316 return getStoreXAction(VT) == Legal || getStoreXAction(VT) == Custom;
319 /// getIndexedLoadAction - Return how the indexed load should be treated:
320 /// either it is legal, needs to be promoted to a larger size, needs to be
321 /// expanded to some other code sequence, or the target has a custom expander
324 getIndexedLoadAction(unsigned IdxMode, MVT::ValueType VT) const {
325 if (MVT::isExtendedVT(VT)) return getTypeAction(VT);
326 return (LegalizeAction)((IndexedModeActions[0][IdxMode] >> (2*VT)) & 3);
329 /// isIndexedLoadLegal - Return true if the specified indexed load is legal
331 bool isIndexedLoadLegal(unsigned IdxMode, MVT::ValueType VT) const {
332 return getIndexedLoadAction(IdxMode, VT) == Legal ||
333 getIndexedLoadAction(IdxMode, VT) == Custom;
336 /// getIndexedStoreAction - Return how the indexed store should be treated:
337 /// either it is legal, needs to be promoted to a larger size, needs to be
338 /// expanded to some other code sequence, or the target has a custom expander
341 getIndexedStoreAction(unsigned IdxMode, MVT::ValueType VT) const {
342 if (MVT::isExtendedVT(VT)) return getTypeAction(VT);
343 return (LegalizeAction)((IndexedModeActions[1][IdxMode] >> (2*VT)) & 3);
346 /// isIndexedStoreLegal - Return true if the specified indexed load is legal
348 bool isIndexedStoreLegal(unsigned IdxMode, MVT::ValueType VT) const {
349 return getIndexedStoreAction(IdxMode, VT) == Legal ||
350 getIndexedStoreAction(IdxMode, VT) == Custom;
353 /// getConvertAction - Return how the conversion should be treated:
354 /// either it is legal, needs to be promoted to a larger size, needs to be
355 /// expanded to some other code sequence, or the target has a custom expander
358 getConvertAction(MVT::ValueType FromVT, MVT::ValueType ToVT) const {
359 assert(FromVT < MVT::LAST_VALUETYPE && ToVT < 32 &&
360 "Table isn't big enough!");
361 return (LegalizeAction)((ConvertActions[FromVT] >> (2*ToVT)) & 3);
364 /// isConvertLegal - Return true if the specified conversion is legal
366 bool isConvertLegal(MVT::ValueType FromVT, MVT::ValueType ToVT) const {
367 return getConvertAction(FromVT, ToVT) == Legal ||
368 getConvertAction(FromVT, ToVT) == Custom;
371 /// getTypeToPromoteTo - If the action for this operation is to promote, this
372 /// method returns the ValueType to promote to.
373 MVT::ValueType getTypeToPromoteTo(unsigned Op, MVT::ValueType VT) const {
374 assert(getOperationAction(Op, VT) == Promote &&
375 "This operation isn't promoted!");
377 // See if this has an explicit type specified.
378 std::map<std::pair<unsigned, MVT::ValueType>,
379 MVT::ValueType>::const_iterator PTTI =
380 PromoteToType.find(std::make_pair(Op, VT));
381 if (PTTI != PromoteToType.end()) return PTTI->second;
383 assert((MVT::isInteger(VT) || MVT::isFloatingPoint(VT)) &&
384 "Cannot autopromote this type, add it with AddPromotedToType.");
386 MVT::ValueType NVT = VT;
388 NVT = (MVT::ValueType)(NVT+1);
389 assert(MVT::isInteger(NVT) == MVT::isInteger(VT) && NVT != MVT::isVoid &&
390 "Didn't find type to promote to!");
391 } while (!isTypeLegal(NVT) ||
392 getOperationAction(Op, NVT) == Promote);
396 /// getValueType - Return the MVT::ValueType corresponding to this LLVM type.
397 /// This is fixed by the LLVM operations except for the pointer size. If
398 /// AllowUnknown is true, this will return MVT::Other for types with no MVT
399 /// counterpart (e.g. structs), otherwise it will assert.
400 MVT::ValueType getValueType(const Type *Ty, bool AllowUnknown = false) const {
401 MVT::ValueType VT = MVT::getValueType(Ty, AllowUnknown);
402 return VT == MVT::iPTR ? PointerTy : VT;
405 /// getRegisterType - Return the type of registers that this ValueType will
406 /// eventually require.
407 MVT::ValueType getRegisterType(MVT::ValueType VT) const {
408 if (!MVT::isExtendedVT(VT))
409 return RegisterTypeForVT[VT];
410 if (MVT::isVector(VT)) {
411 MVT::ValueType VT1, RegisterVT;
412 unsigned NumIntermediates;
413 (void)getVectorTypeBreakdown(VT, VT1, NumIntermediates, RegisterVT);
416 assert(0 && "Unsupported extended type!");
419 /// getNumRegisters - Return the number of registers that this ValueType will
420 /// eventually require. This is one for any types promoted to live in larger
421 /// registers, but may be more than one for types (like i64) that are split
423 unsigned getNumRegisters(MVT::ValueType VT) const {
424 if (!MVT::isExtendedVT(VT))
425 return NumRegistersForVT[VT];
426 if (MVT::isVector(VT)) {
427 MVT::ValueType VT1, VT2;
428 unsigned NumIntermediates;
429 return getVectorTypeBreakdown(VT, VT1, NumIntermediates, VT2);
431 assert(0 && "Unsupported extended type!");
434 /// hasTargetDAGCombine - If true, the target has custom DAG combine
435 /// transformations that it can perform for the specified node.
436 bool hasTargetDAGCombine(ISD::NodeType NT) const {
437 return TargetDAGCombineArray[NT >> 3] & (1 << (NT&7));
440 /// This function returns the maximum number of store operations permitted
441 /// to replace a call to llvm.memset. The value is set by the target at the
442 /// performance threshold for such a replacement.
443 /// @brief Get maximum # of store operations permitted for llvm.memset
444 unsigned getMaxStoresPerMemset() const { return maxStoresPerMemset; }
446 /// This function returns the maximum number of store operations permitted
447 /// to replace a call to llvm.memcpy. The value is set by the target at the
448 /// performance threshold for such a replacement.
449 /// @brief Get maximum # of store operations permitted for llvm.memcpy
450 unsigned getMaxStoresPerMemcpy() const { return maxStoresPerMemcpy; }
452 /// This function returns the maximum number of store operations permitted
453 /// to replace a call to llvm.memmove. The value is set by the target at the
454 /// performance threshold for such a replacement.
455 /// @brief Get maximum # of store operations permitted for llvm.memmove
456 unsigned getMaxStoresPerMemmove() const { return maxStoresPerMemmove; }
458 /// This function returns true if the target allows unaligned memory accesses.
459 /// This is used, for example, in situations where an array copy/move/set is
460 /// converted to a sequence of store operations. It's use helps to ensure that
461 /// such replacements don't generate code that causes an alignment error
462 /// (trap) on the target machine.
463 /// @brief Determine if the target supports unaligned memory accesses.
464 bool allowsUnalignedMemoryAccesses() const {
465 return allowUnalignedMemoryAccesses;
468 /// usesUnderscoreSetJmp - Determine if we should use _setjmp or setjmp
469 /// to implement llvm.setjmp.
470 bool usesUnderscoreSetJmp() const {
471 return UseUnderscoreSetJmp;
474 /// usesUnderscoreLongJmp - Determine if we should use _longjmp or longjmp
475 /// to implement llvm.longjmp.
476 bool usesUnderscoreLongJmp() const {
477 return UseUnderscoreLongJmp;
480 /// getStackPointerRegisterToSaveRestore - If a physical register, this
481 /// specifies the register that llvm.savestack/llvm.restorestack should save
483 unsigned getStackPointerRegisterToSaveRestore() const {
484 return StackPointerRegisterToSaveRestore;
487 /// getExceptionAddressRegister - If a physical register, this returns
488 /// the register that receives the exception address on entry to a landing
490 unsigned getExceptionAddressRegister() const {
491 return ExceptionPointerRegister;
494 /// getExceptionSelectorRegister - If a physical register, this returns
495 /// the register that receives the exception typeid on entry to a landing
497 unsigned getExceptionSelectorRegister() const {
498 return ExceptionSelectorRegister;
501 /// getJumpBufSize - returns the target's jmp_buf size in bytes (if never
502 /// set, the default is 200)
503 unsigned getJumpBufSize() const {
507 /// getJumpBufAlignment - returns the target's jmp_buf alignment in bytes
508 /// (if never set, the default is 0)
509 unsigned getJumpBufAlignment() const {
510 return JumpBufAlignment;
513 /// getIfCvtBlockLimit - returns the target specific if-conversion block size
514 /// limit. Any block whose size is greater should not be predicated.
515 virtual unsigned getIfCvtBlockSizeLimit() const {
516 return IfCvtBlockSizeLimit;
519 /// getIfCvtDupBlockLimit - returns the target specific size limit for a
520 /// block to be considered for duplication. Any block whose size is greater
521 /// should not be duplicated to facilitate its predication.
522 virtual unsigned getIfCvtDupBlockSizeLimit() const {
523 return IfCvtDupBlockSizeLimit;
526 /// getPreIndexedAddressParts - returns true by value, base pointer and
527 /// offset pointer and addressing mode by reference if the node's address
528 /// can be legally represented as pre-indexed load / store address.
529 virtual bool getPreIndexedAddressParts(SDNode *N, SDOperand &Base,
531 ISD::MemIndexedMode &AM,
536 /// getPostIndexedAddressParts - returns true by value, base pointer and
537 /// offset pointer and addressing mode by reference if this node can be
538 /// combined with a load / store to form a post-indexed load / store.
539 virtual bool getPostIndexedAddressParts(SDNode *N, SDNode *Op,
540 SDOperand &Base, SDOperand &Offset,
541 ISD::MemIndexedMode &AM,
546 //===--------------------------------------------------------------------===//
547 // TargetLowering Optimization Methods
550 /// TargetLoweringOpt - A convenience struct that encapsulates a DAG, and two
551 /// SDOperands for returning information from TargetLowering to its clients
552 /// that want to combine
553 struct TargetLoweringOpt {
558 explicit TargetLoweringOpt(SelectionDAG &InDAG) : DAG(InDAG) {}
560 bool CombineTo(SDOperand O, SDOperand N) {
566 /// ShrinkDemandedConstant - Check to see if the specified operand of the
567 /// specified instruction is a constant integer. If so, check to see if
568 /// there are any bits set in the constant that are not demanded. If so,
569 /// shrink the constant and return true.
570 bool ShrinkDemandedConstant(SDOperand Op, uint64_t Demanded);
573 /// SimplifyDemandedBits - Look at Op. At this point, we know that only the
574 /// DemandedMask bits of the result of Op are ever used downstream. If we can
575 /// use this information to simplify Op, create a new simplified DAG node and
576 /// return true, returning the original and new nodes in Old and New.
577 /// Otherwise, analyze the expression and return a mask of KnownOne and
578 /// KnownZero bits for the expression (used to simplify the caller).
579 /// The KnownZero/One bits may only be accurate for those bits in the
581 bool SimplifyDemandedBits(SDOperand Op, uint64_t DemandedMask,
582 uint64_t &KnownZero, uint64_t &KnownOne,
583 TargetLoweringOpt &TLO, unsigned Depth = 0) const;
585 /// computeMaskedBitsForTargetNode - Determine which of the bits specified in
586 /// Mask are known to be either zero or one and return them in the
587 /// KnownZero/KnownOne bitsets.
588 virtual void computeMaskedBitsForTargetNode(const SDOperand Op,
592 const SelectionDAG &DAG,
593 unsigned Depth = 0) const;
595 /// ComputeNumSignBitsForTargetNode - This method can be implemented by
596 /// targets that want to expose additional information about sign bits to the
598 virtual unsigned ComputeNumSignBitsForTargetNode(SDOperand Op,
599 unsigned Depth = 0) const;
601 struct DAGCombinerInfo {
602 void *DC; // The DAG Combiner object.
604 bool CalledByLegalizer;
608 DAGCombinerInfo(SelectionDAG &dag, bool bl, bool cl, void *dc)
609 : DC(dc), BeforeLegalize(bl), CalledByLegalizer(cl), DAG(dag) {}
611 bool isBeforeLegalize() const { return BeforeLegalize; }
612 bool isCalledByLegalizer() const { return CalledByLegalizer; }
614 void AddToWorklist(SDNode *N);
615 SDOperand CombineTo(SDNode *N, const std::vector<SDOperand> &To);
616 SDOperand CombineTo(SDNode *N, SDOperand Res);
617 SDOperand CombineTo(SDNode *N, SDOperand Res0, SDOperand Res1);
620 /// SimplifySetCC - Try to simplify a setcc built with the specified operands
621 /// and cc. If it is unable to simplify it, return a null SDOperand.
622 SDOperand SimplifySetCC(MVT::ValueType VT, SDOperand N0, SDOperand N1,
623 ISD::CondCode Cond, bool foldBooleans,
624 DAGCombinerInfo &DCI) const;
626 /// PerformDAGCombine - This method will be invoked for all target nodes and
627 /// for any target-independent nodes that the target has registered with
630 /// The semantics are as follows:
632 /// SDOperand.Val == 0 - No change was made
633 /// SDOperand.Val == N - N was replaced, is dead, and is already handled.
634 /// otherwise - N should be replaced by the returned Operand.
636 /// In addition, methods provided by DAGCombinerInfo may be used to perform
637 /// more complex transformations.
639 virtual SDOperand PerformDAGCombine(SDNode *N, DAGCombinerInfo &DCI) const;
641 //===--------------------------------------------------------------------===//
642 // TargetLowering Configuration Methods - These methods should be invoked by
643 // the derived class constructor to configure this object for the target.
647 /// setUsesGlobalOffsetTable - Specify that this target does or doesn't use a
648 /// GOT for PC-relative code.
649 void setUsesGlobalOffsetTable(bool V) { UsesGlobalOffsetTable = V; }
651 /// setShiftAmountType - Describe the type that should be used for shift
652 /// amounts. This type defaults to the pointer type.
653 void setShiftAmountType(MVT::ValueType VT) { ShiftAmountTy = VT; }
655 /// setSetCCResultType - Describe the type that shoudl be used as the result
656 /// of a setcc operation. This defaults to the pointer type.
657 void setSetCCResultType(MVT::ValueType VT) { SetCCResultTy = VT; }
659 /// setSetCCResultContents - Specify how the target extends the result of a
660 /// setcc operation in a register.
661 void setSetCCResultContents(SetCCResultValue Ty) { SetCCResultContents = Ty; }
663 /// setSchedulingPreference - Specify the target scheduling preference.
664 void setSchedulingPreference(SchedPreference Pref) {
665 SchedPreferenceInfo = Pref;
668 /// setShiftAmountFlavor - Describe how the target handles out of range shift
670 void setShiftAmountFlavor(OutOfRangeShiftAmount OORSA) {
671 ShiftAmtHandling = OORSA;
674 /// setUseUnderscoreSetJmp - Indicate whether this target prefers to
675 /// use _setjmp to implement llvm.setjmp or the non _ version.
676 /// Defaults to false.
677 void setUseUnderscoreSetJmp(bool Val) {
678 UseUnderscoreSetJmp = Val;
681 /// setUseUnderscoreLongJmp - Indicate whether this target prefers to
682 /// use _longjmp to implement llvm.longjmp or the non _ version.
683 /// Defaults to false.
684 void setUseUnderscoreLongJmp(bool Val) {
685 UseUnderscoreLongJmp = Val;
688 /// setStackPointerRegisterToSaveRestore - If set to a physical register, this
689 /// specifies the register that llvm.savestack/llvm.restorestack should save
691 void setStackPointerRegisterToSaveRestore(unsigned R) {
692 StackPointerRegisterToSaveRestore = R;
695 /// setExceptionPointerRegister - If set to a physical register, this sets
696 /// the register that receives the exception address on entry to a landing
698 void setExceptionPointerRegister(unsigned R) {
699 ExceptionPointerRegister = R;
702 /// setExceptionSelectorRegister - If set to a physical register, this sets
703 /// the register that receives the exception typeid on entry to a landing
705 void setExceptionSelectorRegister(unsigned R) {
706 ExceptionSelectorRegister = R;
709 /// SelectIsExpensive - Tells the code generator not to expand operations
710 /// into sequences that use the select operations if possible.
711 void setSelectIsExpensive() { SelectIsExpensive = true; }
713 /// setIntDivIsCheap - Tells the code generator that integer divide is
714 /// expensive, and if possible, should be replaced by an alternate sequence
715 /// of instructions not containing an integer divide.
716 void setIntDivIsCheap(bool isCheap = true) { IntDivIsCheap = isCheap; }
718 /// setPow2DivIsCheap - Tells the code generator that it shouldn't generate
719 /// srl/add/sra for a signed divide by power of two, and let the target handle
721 void setPow2DivIsCheap(bool isCheap = true) { Pow2DivIsCheap = isCheap; }
723 /// addRegisterClass - Add the specified register class as an available
724 /// regclass for the specified value type. This indicates the selector can
725 /// handle values of that class natively.
726 void addRegisterClass(MVT::ValueType VT, TargetRegisterClass *RC) {
727 assert(!MVT::isExtendedVT(VT));
728 AvailableRegClasses.push_back(std::make_pair(VT, RC));
729 RegClassForVT[VT] = RC;
732 /// computeRegisterProperties - Once all of the register classes are added,
733 /// this allows us to compute derived properties we expose.
734 void computeRegisterProperties();
736 /// setOperationAction - Indicate that the specified operation does not work
737 /// with the specified type and indicate what to do about it.
738 void setOperationAction(unsigned Op, MVT::ValueType VT,
739 LegalizeAction Action) {
740 assert(VT < 32 && Op < array_lengthof(OpActions) &&
741 "Table isn't big enough!");
742 OpActions[Op] &= ~(uint64_t(3UL) << VT*2);
743 OpActions[Op] |= (uint64_t)Action << VT*2;
746 /// setLoadXAction - Indicate that the specified load with extension does not
747 /// work with the with specified type and indicate what to do about it.
748 void setLoadXAction(unsigned ExtType, MVT::ValueType VT,
749 LegalizeAction Action) {
750 assert(VT < 32 && ExtType < array_lengthof(LoadXActions) &&
751 "Table isn't big enough!");
752 LoadXActions[ExtType] &= ~(uint64_t(3UL) << VT*2);
753 LoadXActions[ExtType] |= (uint64_t)Action << VT*2;
756 /// setStoreXAction - Indicate that the specified store with truncation does
757 /// not work with the with specified type and indicate what to do about it.
758 void setStoreXAction(MVT::ValueType VT, LegalizeAction Action) {
759 assert(VT < 32 && "Table isn't big enough!");
760 StoreXActions &= ~(uint64_t(3UL) << VT*2);
761 StoreXActions |= (uint64_t)Action << VT*2;
764 /// setIndexedLoadAction - Indicate that the specified indexed load does or
765 /// does not work with the with specified type and indicate what to do abort
766 /// it. NOTE: All indexed mode loads are initialized to Expand in
767 /// TargetLowering.cpp
768 void setIndexedLoadAction(unsigned IdxMode, MVT::ValueType VT,
769 LegalizeAction Action) {
770 assert(VT < 32 && IdxMode <
771 array_lengthof(IndexedModeActions[0]) &&
772 "Table isn't big enough!");
773 IndexedModeActions[0][IdxMode] &= ~(uint64_t(3UL) << VT*2);
774 IndexedModeActions[0][IdxMode] |= (uint64_t)Action << VT*2;
777 /// setIndexedStoreAction - Indicate that the specified indexed store does or
778 /// does not work with the with specified type and indicate what to do about
779 /// it. NOTE: All indexed mode stores are initialized to Expand in
780 /// TargetLowering.cpp
781 void setIndexedStoreAction(unsigned IdxMode, MVT::ValueType VT,
782 LegalizeAction Action) {
783 assert(VT < 32 && IdxMode <
784 array_lengthof(IndexedModeActions[1]) &&
785 "Table isn't big enough!");
786 IndexedModeActions[1][IdxMode] &= ~(uint64_t(3UL) << VT*2);
787 IndexedModeActions[1][IdxMode] |= (uint64_t)Action << VT*2;
790 /// setConvertAction - Indicate that the specified conversion does or does
791 /// not work with the with specified type and indicate what to do about it.
792 void setConvertAction(MVT::ValueType FromVT, MVT::ValueType ToVT,
793 LegalizeAction Action) {
794 assert(FromVT < MVT::LAST_VALUETYPE && ToVT < 32 &&
795 "Table isn't big enough!");
796 ConvertActions[FromVT] &= ~(uint64_t(3UL) << ToVT*2);
797 ConvertActions[FromVT] |= (uint64_t)Action << ToVT*2;
800 /// AddPromotedToType - If Opc/OrigVT is specified as being promoted, the
801 /// promotion code defaults to trying a larger integer/fp until it can find
802 /// one that works. If that default is insufficient, this method can be used
803 /// by the target to override the default.
804 void AddPromotedToType(unsigned Opc, MVT::ValueType OrigVT,
805 MVT::ValueType DestVT) {
806 PromoteToType[std::make_pair(Opc, OrigVT)] = DestVT;
809 /// addLegalFPImmediate - Indicate that this target can instruction select
810 /// the specified FP immediate natively.
811 void addLegalFPImmediate(const APFloat& Imm) {
812 LegalFPImmediates.push_back(Imm);
815 /// setTargetDAGCombine - Targets should invoke this method for each target
816 /// independent node that they want to provide a custom DAG combiner for by
817 /// implementing the PerformDAGCombine virtual method.
818 void setTargetDAGCombine(ISD::NodeType NT) {
819 TargetDAGCombineArray[NT >> 3] |= 1 << (NT&7);
822 /// setJumpBufSize - Set the target's required jmp_buf buffer size (in
823 /// bytes); default is 200
824 void setJumpBufSize(unsigned Size) {
828 /// setJumpBufAlignment - Set the target's required jmp_buf buffer
829 /// alignment (in bytes); default is 0
830 void setJumpBufAlignment(unsigned Align) {
831 JumpBufAlignment = Align;
834 /// setIfCvtBlockSizeLimit - Set the target's if-conversion block size
835 /// limit (in number of instructions); default is 2.
836 void setIfCvtBlockSizeLimit(unsigned Limit) {
837 IfCvtBlockSizeLimit = Limit;
840 /// setIfCvtDupBlockSizeLimit - Set the target's block size limit (in number
841 /// of instructions) to be considered for code duplication during
842 /// if-conversion; default is 2.
843 void setIfCvtDupBlockSizeLimit(unsigned Limit) {
844 IfCvtDupBlockSizeLimit = Limit;
849 virtual const TargetSubtarget *getSubtarget() {
850 assert(0 && "Not Implemented");
852 //===--------------------------------------------------------------------===//
853 // Lowering methods - These methods must be implemented by targets so that
854 // the SelectionDAGLowering code knows how to lower these.
857 /// LowerArguments - This hook must be implemented to indicate how we should
858 /// lower the arguments for the specified function, into the specified DAG.
859 virtual std::vector<SDOperand>
860 LowerArguments(Function &F, SelectionDAG &DAG);
862 /// LowerCallTo - This hook lowers an abstract call to a function into an
863 /// actual call. This returns a pair of operands. The first element is the
864 /// return value for the function (if RetTy is not VoidTy). The second
865 /// element is the outgoing token chain.
866 struct ArgListEntry {
876 ArgListEntry() : isSExt(false), isZExt(false), isInReg(false),
877 isSRet(false), isNest(false), isByVal(false) { }
879 typedef std::vector<ArgListEntry> ArgListTy;
880 virtual std::pair<SDOperand, SDOperand>
881 LowerCallTo(SDOperand Chain, const Type *RetTy, bool RetTyIsSigned,
882 bool isVarArg, unsigned CallingConv, bool isTailCall,
883 SDOperand Callee, ArgListTy &Args, SelectionDAG &DAG);
886 virtual SDOperand LowerMEMCPY(SDOperand Op, SelectionDAG &DAG);
887 virtual SDOperand LowerMEMCPYCall(SDOperand Chain, SDOperand Dest,
888 SDOperand Source, SDOperand Count,
890 virtual SDOperand LowerMEMCPYInline(SDOperand Chain, SDOperand Dest,
891 SDOperand Source, unsigned Size,
892 unsigned Align, SelectionDAG &DAG) {
893 assert(0 && "Not Implemented");
897 /// LowerOperation - This callback is invoked for operations that are
898 /// unsupported by the target, which are registered to use 'custom' lowering,
899 /// and whose defined values are all legal.
900 /// If the target has no operations that require custom lowering, it need not
901 /// implement this. The default implementation of this aborts.
902 virtual SDOperand LowerOperation(SDOperand Op, SelectionDAG &DAG);
904 /// ExpandOperationResult - This callback is invoked for operations that are
905 /// unsupported by the target, which are registered to use 'custom' lowering,
906 /// and whose result type needs to be expanded.
908 /// If the target has no operations that require custom lowering, it need not
909 /// implement this. The default implementation of this aborts.
910 virtual std::pair<SDOperand,SDOperand>
911 ExpandOperationResult(SDNode *N, SelectionDAG &DAG);
913 /// IsEligibleForTailCallOptimization - Check whether the call is eligible for
914 /// tail call optimization. Targets which want to do tail call optimization
915 /// should override this function.
916 virtual bool IsEligibleForTailCallOptimization(SDOperand Call,
918 SelectionDAG &DAG) const {
922 /// CustomPromoteOperation - This callback is invoked for operations that are
923 /// unsupported by the target, are registered to use 'custom' lowering, and
924 /// whose type needs to be promoted.
925 virtual SDOperand CustomPromoteOperation(SDOperand Op, SelectionDAG &DAG);
927 /// getTargetNodeName() - This method returns the name of a target specific
929 virtual const char *getTargetNodeName(unsigned Opcode) const;
931 //===--------------------------------------------------------------------===//
932 // Inline Asm Support hooks
935 enum ConstraintType {
936 C_Register, // Constraint represents a single register.
937 C_RegisterClass, // Constraint represents one or more registers.
938 C_Memory, // Memory constraint.
939 C_Other, // Something else.
940 C_Unknown // Unsupported constraint.
943 /// getConstraintType - Given a constraint, return the type of constraint it
944 /// is for this target.
945 virtual ConstraintType getConstraintType(const std::string &Constraint) const;
948 /// getRegClassForInlineAsmConstraint - Given a constraint letter (e.g. "r"),
949 /// return a list of registers that can be used to satisfy the constraint.
950 /// This should only be used for C_RegisterClass constraints.
951 virtual std::vector<unsigned>
952 getRegClassForInlineAsmConstraint(const std::string &Constraint,
953 MVT::ValueType VT) const;
955 /// getRegForInlineAsmConstraint - Given a physical register constraint (e.g.
956 /// {edx}), return the register number and the register class for the
959 /// Given a register class constraint, like 'r', if this corresponds directly
960 /// to an LLVM register class, return a register of 0 and the register class
963 /// This should only be used for C_Register constraints. On error,
964 /// this returns a register number of 0 and a null register class pointer..
965 virtual std::pair<unsigned, const TargetRegisterClass*>
966 getRegForInlineAsmConstraint(const std::string &Constraint,
967 MVT::ValueType VT) const;
970 /// LowerAsmOperandForConstraint - Lower the specified operand into the Ops
971 /// vector. If it is invalid, don't add anything to Ops.
972 virtual void LowerAsmOperandForConstraint(SDOperand Op, char ConstraintLetter,
973 std::vector<SDOperand> &Ops,
976 //===--------------------------------------------------------------------===//
980 // InsertAtEndOfBasicBlock - This method should be implemented by targets that
981 // mark instructions with the 'usesCustomDAGSchedInserter' flag. These
982 // instructions are special in various ways, which require special support to
983 // insert. The specified MachineInstr is created but not inserted into any
984 // basic blocks, and the scheduler passes ownership of it to this method.
985 virtual MachineBasicBlock *InsertAtEndOfBasicBlock(MachineInstr *MI,
986 MachineBasicBlock *MBB);
988 //===--------------------------------------------------------------------===//
989 // Addressing mode description hooks (used by LSR etc).
992 /// AddrMode - This represents an addressing mode of:
993 /// BaseGV + BaseOffs + BaseReg + Scale*ScaleReg
994 /// If BaseGV is null, there is no BaseGV.
995 /// If BaseOffs is zero, there is no base offset.
996 /// If HasBaseReg is false, there is no base register.
997 /// If Scale is zero, there is no ScaleReg. Scale of 1 indicates a reg with
1001 GlobalValue *BaseGV;
1005 AddrMode() : BaseGV(0), BaseOffs(0), HasBaseReg(false), Scale(0) {}
1008 /// isLegalAddressingMode - Return true if the addressing mode represented by
1009 /// AM is legal for this target, for a load/store of the specified type.
1010 /// TODO: Handle pre/postinc as well.
1011 virtual bool isLegalAddressingMode(const AddrMode &AM, const Type *Ty) const;
1013 /// isTruncateFree - Return true if it's free to truncate a value of
1014 /// type Ty1 to type Ty2. e.g. On x86 it's free to truncate a i32 value in
1015 /// register EAX to i16 by referencing its sub-register AX.
1016 virtual bool isTruncateFree(const Type *Ty1, const Type *Ty2) const {
1020 virtual bool isTruncateFree(MVT::ValueType VT1, MVT::ValueType VT2) const {
1024 //===--------------------------------------------------------------------===//
1025 // Div utility functions
1027 SDOperand BuildSDIV(SDNode *N, SelectionDAG &DAG,
1028 std::vector<SDNode*>* Created) const;
1029 SDOperand BuildUDIV(SDNode *N, SelectionDAG &DAG,
1030 std::vector<SDNode*>* Created) const;
1033 //===--------------------------------------------------------------------===//
1034 // Runtime Library hooks
1037 /// setLibcallName - Rename the default libcall routine name for the specified
1039 void setLibcallName(RTLIB::Libcall Call, const char *Name) {
1040 LibcallRoutineNames[Call] = Name;
1043 /// getLibcallName - Get the libcall routine name for the specified libcall.
1045 const char *getLibcallName(RTLIB::Libcall Call) const {
1046 return LibcallRoutineNames[Call];
1049 /// setCmpLibcallCC - Override the default CondCode to be used to test the
1050 /// result of the comparison libcall against zero.
1051 void setCmpLibcallCC(RTLIB::Libcall Call, ISD::CondCode CC) {
1052 CmpLibcallCCs[Call] = CC;
1055 /// getCmpLibcallCC - Get the CondCode that's to be used to test the result of
1056 /// the comparison libcall against zero.
1057 ISD::CondCode getCmpLibcallCC(RTLIB::Libcall Call) const {
1058 return CmpLibcallCCs[Call];
1063 const TargetData *TD;
1065 /// IsLittleEndian - True if this is a little endian target.
1067 bool IsLittleEndian;
1069 /// PointerTy - The type to use for pointers, usually i32 or i64.
1071 MVT::ValueType PointerTy;
1073 /// UsesGlobalOffsetTable - True if this target uses a GOT for PIC codegen.
1075 bool UsesGlobalOffsetTable;
1077 /// ShiftAmountTy - The type to use for shift amounts, usually i8 or whatever
1079 MVT::ValueType ShiftAmountTy;
1081 OutOfRangeShiftAmount ShiftAmtHandling;
1083 /// SelectIsExpensive - Tells the code generator not to expand operations
1084 /// into sequences that use the select operations if possible.
1085 bool SelectIsExpensive;
1087 /// IntDivIsCheap - Tells the code generator not to expand integer divides by
1088 /// constants into a sequence of muls, adds, and shifts. This is a hack until
1089 /// a real cost model is in place. If we ever optimize for size, this will be
1090 /// set to true unconditionally.
1093 /// Pow2DivIsCheap - Tells the code generator that it shouldn't generate
1094 /// srl/add/sra for a signed divide by power of two, and let the target handle
1096 bool Pow2DivIsCheap;
1098 /// SetCCResultTy - The type that SetCC operations use. This defaults to the
1100 MVT::ValueType SetCCResultTy;
1102 /// SetCCResultContents - Information about the contents of the high-bits in
1103 /// the result of a setcc comparison operation.
1104 SetCCResultValue SetCCResultContents;
1106 /// SchedPreferenceInfo - The target scheduling preference: shortest possible
1107 /// total cycles or lowest register usage.
1108 SchedPreference SchedPreferenceInfo;
1110 /// UseUnderscoreSetJmp - This target prefers to use _setjmp to implement
1111 /// llvm.setjmp. Defaults to false.
1112 bool UseUnderscoreSetJmp;
1114 /// UseUnderscoreLongJmp - This target prefers to use _longjmp to implement
1115 /// llvm.longjmp. Defaults to false.
1116 bool UseUnderscoreLongJmp;
1118 /// JumpBufSize - The size, in bytes, of the target's jmp_buf buffers
1119 unsigned JumpBufSize;
1121 /// JumpBufAlignment - The alignment, in bytes, of the target's jmp_buf
1123 unsigned JumpBufAlignment;
1125 /// IfCvtBlockSizeLimit - The maximum allowed size for a block to be
1127 unsigned IfCvtBlockSizeLimit;
1129 /// IfCvtDupBlockSizeLimit - The maximum allowed size for a block to be
1130 /// duplicated during if-conversion.
1131 unsigned IfCvtDupBlockSizeLimit;
1133 /// StackPointerRegisterToSaveRestore - If set to a physical register, this
1134 /// specifies the register that llvm.savestack/llvm.restorestack should save
1136 unsigned StackPointerRegisterToSaveRestore;
1138 /// ExceptionPointerRegister - If set to a physical register, this specifies
1139 /// the register that receives the exception address on entry to a landing
1141 unsigned ExceptionPointerRegister;
1143 /// ExceptionSelectorRegister - If set to a physical register, this specifies
1144 /// the register that receives the exception typeid on entry to a landing
1146 unsigned ExceptionSelectorRegister;
1148 /// RegClassForVT - This indicates the default register class to use for
1149 /// each ValueType the target supports natively.
1150 TargetRegisterClass *RegClassForVT[MVT::LAST_VALUETYPE];
1151 unsigned char NumRegistersForVT[MVT::LAST_VALUETYPE];
1152 MVT::ValueType RegisterTypeForVT[MVT::LAST_VALUETYPE];
1154 /// TransformToType - For any value types we are promoting or expanding, this
1155 /// contains the value type that we are changing to. For Expanded types, this
1156 /// contains one step of the expand (e.g. i64 -> i32), even if there are
1157 /// multiple steps required (e.g. i64 -> i16). For types natively supported
1158 /// by the system, this holds the same type (e.g. i32 -> i32).
1159 MVT::ValueType TransformToType[MVT::LAST_VALUETYPE];
1161 /// OpActions - For each operation and each value type, keep a LegalizeAction
1162 /// that indicates how instruction selection should deal with the operation.
1163 /// Most operations are Legal (aka, supported natively by the target), but
1164 /// operations that are not should be described. Note that operations on
1165 /// non-legal value types are not described here.
1166 uint64_t OpActions[156];
1168 /// LoadXActions - For each load of load extension type and each value type,
1169 /// keep a LegalizeAction that indicates how instruction selection should deal
1171 uint64_t LoadXActions[ISD::LAST_LOADX_TYPE];
1173 /// StoreXActions - For each store with truncation of each value type, keep a
1174 /// LegalizeAction that indicates how instruction selection should deal with
1176 uint64_t StoreXActions;
1178 /// IndexedModeActions - For each indexed mode and each value type, keep a
1179 /// pair of LegalizeAction that indicates how instruction selection should
1180 /// deal with the load / store.
1181 uint64_t IndexedModeActions[2][ISD::LAST_INDEXED_MODE];
1183 /// ConvertActions - For each conversion from source type to destination type,
1184 /// keep a LegalizeAction that indicates how instruction selection should
1185 /// deal with the conversion.
1186 /// Currently, this is used only for floating->floating conversions
1187 /// (FP_EXTEND and FP_ROUND).
1188 uint64_t ConvertActions[MVT::LAST_VALUETYPE];
1190 ValueTypeActionImpl ValueTypeActions;
1192 std::vector<APFloat> LegalFPImmediates;
1194 std::vector<std::pair<MVT::ValueType,
1195 TargetRegisterClass*> > AvailableRegClasses;
1197 /// TargetDAGCombineArray - Targets can specify ISD nodes that they would
1198 /// like PerformDAGCombine callbacks for by calling setTargetDAGCombine(),
1199 /// which sets a bit in this array.
1200 unsigned char TargetDAGCombineArray[156/(sizeof(unsigned char)*8)];
1202 /// PromoteToType - For operations that must be promoted to a specific type,
1203 /// this holds the destination type. This map should be sparse, so don't hold
1206 /// Targets add entries to this map with AddPromotedToType(..), clients access
1207 /// this with getTypeToPromoteTo(..).
1208 std::map<std::pair<unsigned, MVT::ValueType>, MVT::ValueType> PromoteToType;
1210 /// LibcallRoutineNames - Stores the name each libcall.
1212 const char *LibcallRoutineNames[RTLIB::UNKNOWN_LIBCALL];
1214 /// CmpLibcallCCs - The ISD::CondCode that should be used to test the result
1215 /// of each of the comparison libcall against zero.
1216 ISD::CondCode CmpLibcallCCs[RTLIB::UNKNOWN_LIBCALL];
1219 /// When lowering %llvm.memset this field specifies the maximum number of
1220 /// store operations that may be substituted for the call to memset. Targets
1221 /// must set this value based on the cost threshold for that target. Targets
1222 /// should assume that the memset will be done using as many of the largest
1223 /// store operations first, followed by smaller ones, if necessary, per
1224 /// alignment restrictions. For example, storing 9 bytes on a 32-bit machine
1225 /// with 16-bit alignment would result in four 2-byte stores and one 1-byte
1226 /// store. This only applies to setting a constant array of a constant size.
1227 /// @brief Specify maximum number of store instructions per memset call.
1228 unsigned maxStoresPerMemset;
1230 /// When lowering %llvm.memcpy this field specifies the maximum number of
1231 /// store operations that may be substituted for a call to memcpy. Targets
1232 /// must set this value based on the cost threshold for that target. Targets
1233 /// should assume that the memcpy will be done using as many of the largest
1234 /// store operations first, followed by smaller ones, if necessary, per
1235 /// alignment restrictions. For example, storing 7 bytes on a 32-bit machine
1236 /// with 32-bit alignment would result in one 4-byte store, a one 2-byte store
1237 /// and one 1-byte store. This only applies to copying a constant array of
1239 /// @brief Specify maximum bytes of store instructions per memcpy call.
1240 unsigned maxStoresPerMemcpy;
1242 /// When lowering %llvm.memmove this field specifies the maximum number of
1243 /// store instructions that may be substituted for a call to memmove. Targets
1244 /// must set this value based on the cost threshold for that target. Targets
1245 /// should assume that the memmove will be done using as many of the largest
1246 /// store operations first, followed by smaller ones, if necessary, per
1247 /// alignment restrictions. For example, moving 9 bytes on a 32-bit machine
1248 /// with 8-bit alignment would result in nine 1-byte stores. This only
1249 /// applies to copying a constant array of constant size.
1250 /// @brief Specify maximum bytes of store instructions per memmove call.
1251 unsigned maxStoresPerMemmove;
1253 /// This field specifies whether the target machine permits unaligned memory
1254 /// accesses. This is used, for example, to determine the size of store
1255 /// operations when copying small arrays and other similar tasks.
1256 /// @brief Indicate whether the target permits unaligned memory accesses.
1257 bool allowUnalignedMemoryAccesses;
1259 } // end llvm namespace