1 //===- llvm/CodeGen/TargetInstrInfo.h - Instruction 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 the target machine instruction set to the code generator.
12 //===----------------------------------------------------------------------===//
14 #ifndef LLVM_TARGET_TARGETINSTRINFO_H
15 #define LLVM_TARGET_TARGETINSTRINFO_H
17 #include "llvm/ADT/ArrayRef.h"
18 #include "llvm/ADT/DenseMap.h"
19 #include "llvm/ADT/DenseMapInfo.h"
20 #include "llvm/ADT/None.h"
21 #include "llvm/CodeGen/MachineBasicBlock.h"
22 #include "llvm/CodeGen/MachineCombinerPattern.h"
23 #include "llvm/CodeGen/MachineFunction.h"
24 #include "llvm/CodeGen/MachineInstr.h"
25 #include "llvm/CodeGen/MachineLoopInfo.h"
26 #include "llvm/CodeGen/MachineOperand.h"
27 #include "llvm/CodeGen/PseudoSourceValue.h"
28 #include "llvm/MC/MCInstrInfo.h"
29 #include "llvm/Support/BranchProbability.h"
30 #include "llvm/Support/ErrorHandling.h"
40 class InstrItineraryData;
43 class MachineMemOperand;
44 class MachineRegisterInfo;
50 class ScheduleHazardRecognizer;
54 class TargetRegisterClass;
55 class TargetRegisterInfo;
56 class TargetSchedModel;
57 class TargetSubtargetInfo;
59 template <class T> class SmallVectorImpl;
61 //---------------------------------------------------------------------------
63 /// TargetInstrInfo - Interface to description of machine instruction set
65 class TargetInstrInfo : public MCInstrInfo {
67 TargetInstrInfo(unsigned CFSetupOpcode = ~0u, unsigned CFDestroyOpcode = ~0u,
68 unsigned CatchRetOpcode = ~0u, unsigned ReturnOpcode = ~0u)
69 : CallFrameSetupOpcode(CFSetupOpcode),
70 CallFrameDestroyOpcode(CFDestroyOpcode), CatchRetOpcode(CatchRetOpcode),
71 ReturnOpcode(ReturnOpcode) {}
72 TargetInstrInfo(const TargetInstrInfo &) = delete;
73 TargetInstrInfo &operator=(const TargetInstrInfo &) = delete;
74 virtual ~TargetInstrInfo();
76 static bool isGenericOpcode(unsigned Opc) {
77 return Opc <= TargetOpcode::GENERIC_OP_END;
80 /// Given a machine instruction descriptor, returns the register
81 /// class constraint for OpNum, or NULL.
82 const TargetRegisterClass *getRegClass(const MCInstrDesc &TID, unsigned OpNum,
83 const TargetRegisterInfo *TRI,
84 const MachineFunction &MF) const;
86 /// Return true if the instruction is trivially rematerializable, meaning it
87 /// has no side effects and requires no operands that aren't always available.
88 /// This means the only allowed uses are constants and unallocatable physical
89 /// registers so that the instructions result is independent of the place
91 bool isTriviallyReMaterializable(const MachineInstr &MI,
92 AliasAnalysis *AA = nullptr) const {
93 return MI.getOpcode() == TargetOpcode::IMPLICIT_DEF ||
94 (MI.getDesc().isRematerializable() &&
95 (isReallyTriviallyReMaterializable(MI, AA) ||
96 isReallyTriviallyReMaterializableGeneric(MI, AA)));
100 /// For instructions with opcodes for which the M_REMATERIALIZABLE flag is
101 /// set, this hook lets the target specify whether the instruction is actually
102 /// trivially rematerializable, taking into consideration its operands. This
103 /// predicate must return false if the instruction has any side effects other
104 /// than producing a value, or if it requres any address registers that are
105 /// not always available.
106 /// Requirements must be check as stated in isTriviallyReMaterializable() .
107 virtual bool isReallyTriviallyReMaterializable(const MachineInstr &MI,
108 AliasAnalysis *AA) const {
112 /// This method commutes the operands of the given machine instruction MI.
113 /// The operands to be commuted are specified by their indices OpIdx1 and
116 /// If a target has any instructions that are commutable but require
117 /// converting to different instructions or making non-trivial changes
118 /// to commute them, this method can be overloaded to do that.
119 /// The default implementation simply swaps the commutable operands.
121 /// If NewMI is false, MI is modified in place and returned; otherwise, a
122 /// new machine instruction is created and returned.
124 /// Do not call this method for a non-commutable instruction.
125 /// Even though the instruction is commutable, the method may still
126 /// fail to commute the operands, null pointer is returned in such cases.
127 virtual MachineInstr *commuteInstructionImpl(MachineInstr &MI, bool NewMI,
129 unsigned OpIdx2) const;
131 /// Assigns the (CommutableOpIdx1, CommutableOpIdx2) pair of commutable
132 /// operand indices to (ResultIdx1, ResultIdx2).
133 /// One or both input values of the pair: (ResultIdx1, ResultIdx2) may be
134 /// predefined to some indices or be undefined (designated by the special
135 /// value 'CommuteAnyOperandIndex').
136 /// The predefined result indices cannot be re-defined.
137 /// The function returns true iff after the result pair redefinition
138 /// the fixed result pair is equal to or equivalent to the source pair of
139 /// indices: (CommutableOpIdx1, CommutableOpIdx2). It is assumed here that
140 /// the pairs (x,y) and (y,x) are equivalent.
141 static bool fixCommutedOpIndices(unsigned &ResultIdx1, unsigned &ResultIdx2,
142 unsigned CommutableOpIdx1,
143 unsigned CommutableOpIdx2);
146 /// For instructions with opcodes for which the M_REMATERIALIZABLE flag is
147 /// set and the target hook isReallyTriviallyReMaterializable returns false,
148 /// this function does target-independent tests to determine if the
149 /// instruction is really trivially rematerializable.
150 bool isReallyTriviallyReMaterializableGeneric(const MachineInstr &MI,
151 AliasAnalysis *AA) const;
154 /// These methods return the opcode of the frame setup/destroy instructions
155 /// if they exist (-1 otherwise). Some targets use pseudo instructions in
156 /// order to abstract away the difference between operating with a frame
157 /// pointer and operating without, through the use of these two instructions.
159 unsigned getCallFrameSetupOpcode() const { return CallFrameSetupOpcode; }
160 unsigned getCallFrameDestroyOpcode() const { return CallFrameDestroyOpcode; }
162 /// Returns true if the argument is a frame pseudo instruction.
163 bool isFrameInstr(const MachineInstr &I) const {
164 return I.getOpcode() == getCallFrameSetupOpcode() ||
165 I.getOpcode() == getCallFrameDestroyOpcode();
168 /// Returns true if the argument is a frame setup pseudo instruction.
169 bool isFrameSetup(const MachineInstr &I) const {
170 return I.getOpcode() == getCallFrameSetupOpcode();
173 /// Returns size of the frame associated with the given frame instruction.
174 /// For frame setup instruction this is frame that is set up space set up
175 /// after the instruction. For frame destroy instruction this is the frame
176 /// freed by the caller.
177 /// Note, in some cases a call frame (or a part of it) may be prepared prior
178 /// to the frame setup instruction. It occurs in the calls that involve
179 /// inalloca arguments. This function reports only the size of the frame part
180 /// that is set up between the frame setup and destroy pseudo instructions.
181 int64_t getFrameSize(const MachineInstr &I) const {
182 assert(isFrameInstr(I) && "Not a frame instruction");
183 assert(I.getOperand(0).getImm() >= 0);
184 return I.getOperand(0).getImm();
187 /// Returns the total frame size, which is made up of the space set up inside
188 /// the pair of frame start-stop instructions and the space that is set up
189 /// prior to the pair.
190 int64_t getFrameTotalSize(const MachineInstr &I) const {
191 if (isFrameSetup(I)) {
192 assert(I.getOperand(1).getImm() >= 0 &&
193 "Frame size must not be negative");
194 return getFrameSize(I) + I.getOperand(1).getImm();
196 return getFrameSize(I);
199 unsigned getCatchReturnOpcode() const { return CatchRetOpcode; }
200 unsigned getReturnOpcode() const { return ReturnOpcode; }
202 /// Returns the actual stack pointer adjustment made by an instruction
203 /// as part of a call sequence. By default, only call frame setup/destroy
204 /// instructions adjust the stack, but targets may want to override this
205 /// to enable more fine-grained adjustment, or adjust by a different value.
206 virtual int getSPAdjust(const MachineInstr &MI) const;
208 /// Return true if the instruction is a "coalescable" extension instruction.
209 /// That is, it's like a copy where it's legal for the source to overlap the
210 /// destination. e.g. X86::MOVSX64rr32. If this returns true, then it's
211 /// expected the pre-extension value is available as a subreg of the result
212 /// register. This also returns the sub-register index in SubIdx.
213 virtual bool isCoalescableExtInstr(const MachineInstr &MI, unsigned &SrcReg,
214 unsigned &DstReg, unsigned &SubIdx) const {
218 /// If the specified machine instruction is a direct
219 /// load from a stack slot, return the virtual or physical register number of
220 /// the destination along with the FrameIndex of the loaded stack slot. If
221 /// not, return 0. This predicate must return 0 if the instruction has
222 /// any side effects other than loading from the stack slot.
223 virtual unsigned isLoadFromStackSlot(const MachineInstr &MI,
224 int &FrameIndex) const {
228 /// Check for post-frame ptr elimination stack locations as well.
229 /// This uses a heuristic so it isn't reliable for correctness.
230 virtual unsigned isLoadFromStackSlotPostFE(const MachineInstr &MI,
231 int &FrameIndex) const {
235 /// If the specified machine instruction has a load from a stack slot,
236 /// return true along with the FrameIndex of the loaded stack slot and the
237 /// machine mem operand containing the reference.
238 /// If not, return false. Unlike isLoadFromStackSlot, this returns true for
239 /// any instructions that loads from the stack. This is just a hint, as some
240 /// cases may be missed.
241 virtual bool hasLoadFromStackSlot(const MachineInstr &MI,
242 const MachineMemOperand *&MMO,
243 int &FrameIndex) const;
245 /// If the specified machine instruction is a direct
246 /// store to a stack slot, return the virtual or physical register number of
247 /// the source reg along with the FrameIndex of the loaded stack slot. If
248 /// not, return 0. This predicate must return 0 if the instruction has
249 /// any side effects other than storing to the stack slot.
250 virtual unsigned isStoreToStackSlot(const MachineInstr &MI,
251 int &FrameIndex) const {
255 /// Check for post-frame ptr elimination stack locations as well.
256 /// This uses a heuristic, so it isn't reliable for correctness.
257 virtual unsigned isStoreToStackSlotPostFE(const MachineInstr &MI,
258 int &FrameIndex) const {
262 /// If the specified machine instruction has a store to a stack slot,
263 /// return true along with the FrameIndex of the loaded stack slot and the
264 /// machine mem operand containing the reference.
265 /// If not, return false. Unlike isStoreToStackSlot,
266 /// this returns true for any instructions that stores to the
267 /// stack. This is just a hint, as some cases may be missed.
268 virtual bool hasStoreToStackSlot(const MachineInstr &MI,
269 const MachineMemOperand *&MMO,
270 int &FrameIndex) const;
272 /// Return true if the specified machine instruction
273 /// is a copy of one stack slot to another and has no other effect.
274 /// Provide the identity of the two frame indices.
275 virtual bool isStackSlotCopy(const MachineInstr &MI, int &DestFrameIndex,
276 int &SrcFrameIndex) const {
280 /// Compute the size in bytes and offset within a stack slot of a spilled
281 /// register or subregister.
283 /// \param [out] Size in bytes of the spilled value.
284 /// \param [out] Offset in bytes within the stack slot.
285 /// \returns true if both Size and Offset are successfully computed.
287 /// Not all subregisters have computable spill slots. For example,
288 /// subregisters registers may not be byte-sized, and a pair of discontiguous
289 /// subregisters has no single offset.
291 /// Targets with nontrivial bigendian implementations may need to override
292 /// this, particularly to support spilled vector registers.
293 virtual bool getStackSlotRange(const TargetRegisterClass *RC, unsigned SubIdx,
294 unsigned &Size, unsigned &Offset,
295 const MachineFunction &MF) const;
297 /// Returns the size in bytes of the specified MachineInstr, or ~0U
298 /// when this function is not implemented by a target.
299 virtual unsigned getInstSizeInBytes(const MachineInstr &MI) const {
303 /// Return true if the instruction is as cheap as a move instruction.
305 /// Targets for different archs need to override this, and different
306 /// micro-architectures can also be finely tuned inside.
307 virtual bool isAsCheapAsAMove(const MachineInstr &MI) const {
308 return MI.isAsCheapAsAMove();
311 /// Return true if the instruction should be sunk by MachineSink.
313 /// MachineSink determines on its own whether the instruction is safe to sink;
314 /// this gives the target a hook to override the default behavior with regards
315 /// to which instructions should be sunk.
316 virtual bool shouldSink(const MachineInstr &MI) const { return true; }
318 /// Re-issue the specified 'original' instruction at the
319 /// specific location targeting a new destination register.
320 /// The register in Orig->getOperand(0).getReg() will be substituted by
321 /// DestReg:SubIdx. Any existing subreg index is preserved or composed with
323 virtual void reMaterialize(MachineBasicBlock &MBB,
324 MachineBasicBlock::iterator MI, unsigned DestReg,
325 unsigned SubIdx, const MachineInstr &Orig,
326 const TargetRegisterInfo &TRI) const;
328 /// \brief Clones instruction or the whole instruction bundle \p Orig and
329 /// insert into \p MBB before \p InsertBefore. The target may update operands
330 /// that are required to be unique.
332 /// \p Orig must not return true for MachineInstr::isNotDuplicable().
333 virtual MachineInstr &duplicate(MachineBasicBlock &MBB,
334 MachineBasicBlock::iterator InsertBefore,
335 const MachineInstr &Orig) const;
337 /// This method must be implemented by targets that
338 /// set the M_CONVERTIBLE_TO_3_ADDR flag. When this flag is set, the target
339 /// may be able to convert a two-address instruction into one or more true
340 /// three-address instructions on demand. This allows the X86 target (for
341 /// example) to convert ADD and SHL instructions into LEA instructions if they
342 /// would require register copies due to two-addressness.
344 /// This method returns a null pointer if the transformation cannot be
345 /// performed, otherwise it returns the last new instruction.
347 virtual MachineInstr *convertToThreeAddress(MachineFunction::iterator &MFI,
349 LiveVariables *LV) const {
353 // This constant can be used as an input value of operand index passed to
354 // the method findCommutedOpIndices() to tell the method that the
355 // corresponding operand index is not pre-defined and that the method
356 // can pick any commutable operand.
357 static const unsigned CommuteAnyOperandIndex = ~0U;
359 /// This method commutes the operands of the given machine instruction MI.
361 /// The operands to be commuted are specified by their indices OpIdx1 and
362 /// OpIdx2. OpIdx1 and OpIdx2 arguments may be set to a special value
363 /// 'CommuteAnyOperandIndex', which means that the method is free to choose
364 /// any arbitrarily chosen commutable operand. If both arguments are set to
365 /// 'CommuteAnyOperandIndex' then the method looks for 2 different commutable
366 /// operands; then commutes them if such operands could be found.
368 /// If NewMI is false, MI is modified in place and returned; otherwise, a
369 /// new machine instruction is created and returned.
371 /// Do not call this method for a non-commutable instruction or
372 /// for non-commuable operands.
373 /// Even though the instruction is commutable, the method may still
374 /// fail to commute the operands, null pointer is returned in such cases.
376 commuteInstruction(MachineInstr &MI, bool NewMI = false,
377 unsigned OpIdx1 = CommuteAnyOperandIndex,
378 unsigned OpIdx2 = CommuteAnyOperandIndex) const;
380 /// Returns true iff the routine could find two commutable operands in the
381 /// given machine instruction.
382 /// The 'SrcOpIdx1' and 'SrcOpIdx2' are INPUT and OUTPUT arguments.
383 /// If any of the INPUT values is set to the special value
384 /// 'CommuteAnyOperandIndex' then the method arbitrarily picks a commutable
385 /// operand, then returns its index in the corresponding argument.
386 /// If both of INPUT values are set to 'CommuteAnyOperandIndex' then method
387 /// looks for 2 commutable operands.
388 /// If INPUT values refer to some operands of MI, then the method simply
389 /// returns true if the corresponding operands are commutable and returns
392 /// For example, calling this method this way:
393 /// unsigned Op1 = 1, Op2 = CommuteAnyOperandIndex;
394 /// findCommutedOpIndices(MI, Op1, Op2);
395 /// can be interpreted as a query asking to find an operand that would be
396 /// commutable with the operand#1.
397 virtual bool findCommutedOpIndices(MachineInstr &MI, unsigned &SrcOpIdx1,
398 unsigned &SrcOpIdx2) const;
400 /// A pair composed of a register and a sub-register index.
401 /// Used to give some type checking when modeling Reg:SubReg.
402 struct RegSubRegPair {
406 RegSubRegPair(unsigned Reg = 0, unsigned SubReg = 0)
407 : Reg(Reg), SubReg(SubReg) {}
410 /// A pair composed of a pair of a register and a sub-register index,
411 /// and another sub-register index.
412 /// Used to give some type checking when modeling Reg:SubReg1, SubReg2.
413 struct RegSubRegPairAndIdx : RegSubRegPair {
416 RegSubRegPairAndIdx(unsigned Reg = 0, unsigned SubReg = 0,
418 : RegSubRegPair(Reg, SubReg), SubIdx(SubIdx) {}
421 /// Build the equivalent inputs of a REG_SEQUENCE for the given \p MI
423 /// \p [out] InputRegs of the equivalent REG_SEQUENCE. Each element of
424 /// the list is modeled as <Reg:SubReg, SubIdx>.
425 /// E.g., REG_SEQUENCE %1:sub1, sub0, %2, sub1 would produce
430 /// \returns true if it is possible to build such an input sequence
431 /// with the pair \p MI, \p DefIdx. False otherwise.
433 /// \pre MI.isRegSequence() or MI.isRegSequenceLike().
435 /// \note The generic implementation does not provide any support for
436 /// MI.isRegSequenceLike(). In other words, one has to override
437 /// getRegSequenceLikeInputs for target specific instructions.
439 getRegSequenceInputs(const MachineInstr &MI, unsigned DefIdx,
440 SmallVectorImpl<RegSubRegPairAndIdx> &InputRegs) const;
442 /// Build the equivalent inputs of a EXTRACT_SUBREG for the given \p MI
444 /// \p [out] InputReg of the equivalent EXTRACT_SUBREG.
445 /// E.g., EXTRACT_SUBREG %1:sub1, sub0, sub1 would produce:
448 /// \returns true if it is possible to build such an input sequence
449 /// with the pair \p MI, \p DefIdx. False otherwise.
451 /// \pre MI.isExtractSubreg() or MI.isExtractSubregLike().
453 /// \note The generic implementation does not provide any support for
454 /// MI.isExtractSubregLike(). In other words, one has to override
455 /// getExtractSubregLikeInputs for target specific instructions.
456 bool getExtractSubregInputs(const MachineInstr &MI, unsigned DefIdx,
457 RegSubRegPairAndIdx &InputReg) const;
459 /// Build the equivalent inputs of a INSERT_SUBREG for the given \p MI
461 /// \p [out] BaseReg and \p [out] InsertedReg contain
462 /// the equivalent inputs of INSERT_SUBREG.
463 /// E.g., INSERT_SUBREG %0:sub0, %1:sub1, sub3 would produce:
464 /// - BaseReg: %0:sub0
465 /// - InsertedReg: %1:sub1, sub3
467 /// \returns true if it is possible to build such an input sequence
468 /// with the pair \p MI, \p DefIdx. False otherwise.
470 /// \pre MI.isInsertSubreg() or MI.isInsertSubregLike().
472 /// \note The generic implementation does not provide any support for
473 /// MI.isInsertSubregLike(). In other words, one has to override
474 /// getInsertSubregLikeInputs for target specific instructions.
475 bool getInsertSubregInputs(const MachineInstr &MI, unsigned DefIdx,
476 RegSubRegPair &BaseReg,
477 RegSubRegPairAndIdx &InsertedReg) const;
479 /// Return true if two machine instructions would produce identical values.
480 /// By default, this is only true when the two instructions
481 /// are deemed identical except for defs. If this function is called when the
482 /// IR is still in SSA form, the caller can pass the MachineRegisterInfo for
483 /// aggressive checks.
484 virtual bool produceSameValue(const MachineInstr &MI0,
485 const MachineInstr &MI1,
486 const MachineRegisterInfo *MRI = nullptr) const;
488 /// \returns true if a branch from an instruction with opcode \p BranchOpc
489 /// bytes is capable of jumping to a position \p BrOffset bytes away.
490 virtual bool isBranchOffsetInRange(unsigned BranchOpc,
491 int64_t BrOffset) const {
492 llvm_unreachable("target did not implement");
495 /// \returns The block that branch instruction \p MI jumps to.
496 virtual MachineBasicBlock *getBranchDestBlock(const MachineInstr &MI) const {
497 llvm_unreachable("target did not implement");
500 /// Insert an unconditional indirect branch at the end of \p MBB to \p
501 /// NewDestBB. \p BrOffset indicates the offset of \p NewDestBB relative to
502 /// the offset of the position to insert the new branch.
504 /// \returns The number of bytes added to the block.
505 virtual unsigned insertIndirectBranch(MachineBasicBlock &MBB,
506 MachineBasicBlock &NewDestBB,
508 int64_t BrOffset = 0,
509 RegScavenger *RS = nullptr) const {
510 llvm_unreachable("target did not implement");
513 /// Analyze the branching code at the end of MBB, returning
514 /// true if it cannot be understood (e.g. it's a switch dispatch or isn't
515 /// implemented for a target). Upon success, this returns false and returns
516 /// with the following information in various cases:
518 /// 1. If this block ends with no branches (it just falls through to its succ)
519 /// just return false, leaving TBB/FBB null.
520 /// 2. If this block ends with only an unconditional branch, it sets TBB to be
521 /// the destination block.
522 /// 3. If this block ends with a conditional branch and it falls through to a
523 /// successor block, it sets TBB to be the branch destination block and a
524 /// list of operands that evaluate the condition. These operands can be
525 /// passed to other TargetInstrInfo methods to create new branches.
526 /// 4. If this block ends with a conditional branch followed by an
527 /// unconditional branch, it returns the 'true' destination in TBB, the
528 /// 'false' destination in FBB, and a list of operands that evaluate the
529 /// condition. These operands can be passed to other TargetInstrInfo
530 /// methods to create new branches.
532 /// Note that removeBranch and insertBranch must be implemented to support
533 /// cases where this method returns success.
535 /// If AllowModify is true, then this routine is allowed to modify the basic
536 /// block (e.g. delete instructions after the unconditional branch).
538 /// The CFG information in MBB.Predecessors and MBB.Successors must be valid
539 /// before calling this function.
540 virtual bool analyzeBranch(MachineBasicBlock &MBB, MachineBasicBlock *&TBB,
541 MachineBasicBlock *&FBB,
542 SmallVectorImpl<MachineOperand> &Cond,
543 bool AllowModify = false) const {
547 /// Represents a predicate at the MachineFunction level. The control flow a
548 /// MachineBranchPredicate represents is:
550 /// Reg = LHS `Predicate` RHS == ConditionDef
551 /// if Reg then goto TrueDest else goto FalseDest
553 struct MachineBranchPredicate {
554 enum ComparePredicate {
555 PRED_EQ, // True if two values are equal
556 PRED_NE, // True if two values are not equal
557 PRED_INVALID // Sentinel value
560 ComparePredicate Predicate = PRED_INVALID;
561 MachineOperand LHS = MachineOperand::CreateImm(0);
562 MachineOperand RHS = MachineOperand::CreateImm(0);
563 MachineBasicBlock *TrueDest = nullptr;
564 MachineBasicBlock *FalseDest = nullptr;
565 MachineInstr *ConditionDef = nullptr;
567 /// SingleUseCondition is true if ConditionDef is dead except for the
568 /// branch(es) at the end of the basic block.
570 bool SingleUseCondition = false;
572 explicit MachineBranchPredicate() = default;
575 /// Analyze the branching code at the end of MBB and parse it into the
576 /// MachineBranchPredicate structure if possible. Returns false on success
577 /// and true on failure.
579 /// If AllowModify is true, then this routine is allowed to modify the basic
580 /// block (e.g. delete instructions after the unconditional branch).
582 virtual bool analyzeBranchPredicate(MachineBasicBlock &MBB,
583 MachineBranchPredicate &MBP,
584 bool AllowModify = false) const {
588 /// Remove the branching code at the end of the specific MBB.
589 /// This is only invoked in cases where AnalyzeBranch returns success. It
590 /// returns the number of instructions that were removed.
591 /// If \p BytesRemoved is non-null, report the change in code size from the
592 /// removed instructions.
593 virtual unsigned removeBranch(MachineBasicBlock &MBB,
594 int *BytesRemoved = nullptr) const {
595 llvm_unreachable("Target didn't implement TargetInstrInfo::removeBranch!");
598 /// Insert branch code into the end of the specified MachineBasicBlock. The
599 /// operands to this method are the same as those returned by AnalyzeBranch.
600 /// This is only invoked in cases where AnalyzeBranch returns success. It
601 /// returns the number of instructions inserted. If \p BytesAdded is non-null,
602 /// report the change in code size from the added instructions.
604 /// It is also invoked by tail merging to add unconditional branches in
605 /// cases where AnalyzeBranch doesn't apply because there was no original
606 /// branch to analyze. At least this much must be implemented, else tail
607 /// merging needs to be disabled.
609 /// The CFG information in MBB.Predecessors and MBB.Successors must be valid
610 /// before calling this function.
611 virtual unsigned insertBranch(MachineBasicBlock &MBB, MachineBasicBlock *TBB,
612 MachineBasicBlock *FBB,
613 ArrayRef<MachineOperand> Cond,
615 int *BytesAdded = nullptr) const {
616 llvm_unreachable("Target didn't implement TargetInstrInfo::insertBranch!");
619 unsigned insertUnconditionalBranch(MachineBasicBlock &MBB,
620 MachineBasicBlock *DestBB,
622 int *BytesAdded = nullptr) const {
623 return insertBranch(MBB, DestBB, nullptr, ArrayRef<MachineOperand>(), DL,
627 /// Analyze the loop code, return true if it cannot be understoo. Upon
628 /// success, this function returns false and returns information about the
629 /// induction variable and compare instruction used at the end.
630 virtual bool analyzeLoop(MachineLoop &L, MachineInstr *&IndVarInst,
631 MachineInstr *&CmpInst) const {
635 /// Generate code to reduce the loop iteration by one and check if the loop is
636 /// finished. Return the value/register of the the new loop count. We need
637 /// this function when peeling off one or more iterations of a loop. This
638 /// function assumes the nth iteration is peeled first.
639 virtual unsigned reduceLoopCount(MachineBasicBlock &MBB, MachineInstr *IndVar,
641 SmallVectorImpl<MachineOperand> &Cond,
642 SmallVectorImpl<MachineInstr *> &PrevInsts,
643 unsigned Iter, unsigned MaxIter) const {
644 llvm_unreachable("Target didn't implement ReduceLoopCount");
647 /// Delete the instruction OldInst and everything after it, replacing it with
648 /// an unconditional branch to NewDest. This is used by the tail merging pass.
649 virtual void ReplaceTailWithBranchTo(MachineBasicBlock::iterator Tail,
650 MachineBasicBlock *NewDest) const;
652 /// Return true if it's legal to split the given basic
653 /// block at the specified instruction (i.e. instruction would be the start
654 /// of a new basic block).
655 virtual bool isLegalToSplitMBBAt(MachineBasicBlock &MBB,
656 MachineBasicBlock::iterator MBBI) const {
660 /// Return true if it's profitable to predicate
661 /// instructions with accumulated instruction latency of "NumCycles"
662 /// of the specified basic block, where the probability of the instructions
663 /// being executed is given by Probability, and Confidence is a measure
664 /// of our confidence that it will be properly predicted.
665 virtual bool isProfitableToIfCvt(MachineBasicBlock &MBB, unsigned NumCycles,
666 unsigned ExtraPredCycles,
667 BranchProbability Probability) const {
671 /// Second variant of isProfitableToIfCvt. This one
672 /// checks for the case where two basic blocks from true and false path
673 /// of a if-then-else (diamond) are predicated on mutally exclusive
674 /// predicates, where the probability of the true path being taken is given
675 /// by Probability, and Confidence is a measure of our confidence that it
676 /// will be properly predicted.
677 virtual bool isProfitableToIfCvt(MachineBasicBlock &TMBB, unsigned NumTCycles,
678 unsigned ExtraTCycles,
679 MachineBasicBlock &FMBB, unsigned NumFCycles,
680 unsigned ExtraFCycles,
681 BranchProbability Probability) const {
685 /// Return true if it's profitable for if-converter to duplicate instructions
686 /// of specified accumulated instruction latencies in the specified MBB to
687 /// enable if-conversion.
688 /// The probability of the instructions being executed is given by
689 /// Probability, and Confidence is a measure of our confidence that it
690 /// will be properly predicted.
691 virtual bool isProfitableToDupForIfCvt(MachineBasicBlock &MBB,
693 BranchProbability Probability) const {
697 /// Return true if it's profitable to unpredicate
698 /// one side of a 'diamond', i.e. two sides of if-else predicated on mutually
699 /// exclusive predicates.
707 /// This may be profitable is conditional instructions are always executed.
708 virtual bool isProfitableToUnpredicate(MachineBasicBlock &TMBB,
709 MachineBasicBlock &FMBB) const {
713 /// Return true if it is possible to insert a select
714 /// instruction that chooses between TrueReg and FalseReg based on the
715 /// condition code in Cond.
717 /// When successful, also return the latency in cycles from TrueReg,
718 /// FalseReg, and Cond to the destination register. In most cases, a select
719 /// instruction will be 1 cycle, so CondCycles = TrueCycles = FalseCycles = 1
721 /// Some x86 implementations have 2-cycle cmov instructions.
723 /// @param MBB Block where select instruction would be inserted.
724 /// @param Cond Condition returned by AnalyzeBranch.
725 /// @param TrueReg Virtual register to select when Cond is true.
726 /// @param FalseReg Virtual register to select when Cond is false.
727 /// @param CondCycles Latency from Cond+Branch to select output.
728 /// @param TrueCycles Latency from TrueReg to select output.
729 /// @param FalseCycles Latency from FalseReg to select output.
730 virtual bool canInsertSelect(const MachineBasicBlock &MBB,
731 ArrayRef<MachineOperand> Cond, unsigned TrueReg,
732 unsigned FalseReg, int &CondCycles,
733 int &TrueCycles, int &FalseCycles) const {
737 /// Insert a select instruction into MBB before I that will copy TrueReg to
738 /// DstReg when Cond is true, and FalseReg to DstReg when Cond is false.
740 /// This function can only be called after canInsertSelect() returned true.
741 /// The condition in Cond comes from AnalyzeBranch, and it can be assumed
742 /// that the same flags or registers required by Cond are available at the
745 /// @param MBB Block where select instruction should be inserted.
746 /// @param I Insertion point.
747 /// @param DL Source location for debugging.
748 /// @param DstReg Virtual register to be defined by select instruction.
749 /// @param Cond Condition as computed by AnalyzeBranch.
750 /// @param TrueReg Virtual register to copy when Cond is true.
751 /// @param FalseReg Virtual register to copy when Cons is false.
752 virtual void insertSelect(MachineBasicBlock &MBB,
753 MachineBasicBlock::iterator I, const DebugLoc &DL,
754 unsigned DstReg, ArrayRef<MachineOperand> Cond,
755 unsigned TrueReg, unsigned FalseReg) const {
756 llvm_unreachable("Target didn't implement TargetInstrInfo::insertSelect!");
759 /// Analyze the given select instruction, returning true if
760 /// it cannot be understood. It is assumed that MI->isSelect() is true.
762 /// When successful, return the controlling condition and the operands that
763 /// determine the true and false result values.
765 /// Result = SELECT Cond, TrueOp, FalseOp
767 /// Some targets can optimize select instructions, for example by predicating
768 /// the instruction defining one of the operands. Such targets should set
771 /// @param MI Select instruction to analyze.
772 /// @param Cond Condition controlling the select.
773 /// @param TrueOp Operand number of the value selected when Cond is true.
774 /// @param FalseOp Operand number of the value selected when Cond is false.
775 /// @param Optimizable Returned as true if MI is optimizable.
776 /// @returns False on success.
777 virtual bool analyzeSelect(const MachineInstr &MI,
778 SmallVectorImpl<MachineOperand> &Cond,
779 unsigned &TrueOp, unsigned &FalseOp,
780 bool &Optimizable) const {
781 assert(MI.getDesc().isSelect() && "MI must be a select instruction");
785 /// Given a select instruction that was understood by
786 /// analyzeSelect and returned Optimizable = true, attempt to optimize MI by
787 /// merging it with one of its operands. Returns NULL on failure.
789 /// When successful, returns the new select instruction. The client is
790 /// responsible for deleting MI.
792 /// If both sides of the select can be optimized, PreferFalse is used to pick
795 /// @param MI Optimizable select instruction.
796 /// @param NewMIs Set that record all MIs in the basic block up to \p
797 /// MI. Has to be updated with any newly created MI or deleted ones.
798 /// @param PreferFalse Try to optimize FalseOp instead of TrueOp.
799 /// @returns Optimized instruction or NULL.
800 virtual MachineInstr *optimizeSelect(MachineInstr &MI,
801 SmallPtrSetImpl<MachineInstr *> &NewMIs,
802 bool PreferFalse = false) const {
803 // This function must be implemented if Optimizable is ever set.
804 llvm_unreachable("Target must implement TargetInstrInfo::optimizeSelect!");
807 /// Emit instructions to copy a pair of physical registers.
809 /// This function should support copies within any legal register class as
810 /// well as any cross-class copies created during instruction selection.
812 /// The source and destination registers may overlap, which may require a
813 /// careful implementation when multiple copy instructions are required for
814 /// large registers. See for example the ARM target.
815 virtual void copyPhysReg(MachineBasicBlock &MBB,
816 MachineBasicBlock::iterator MI, const DebugLoc &DL,
817 unsigned DestReg, unsigned SrcReg,
818 bool KillSrc) const {
819 llvm_unreachable("Target didn't implement TargetInstrInfo::copyPhysReg!");
822 /// Store the specified register of the given register class to the specified
823 /// stack frame index. The store instruction is to be added to the given
824 /// machine basic block before the specified machine instruction. If isKill
825 /// is true, the register operand is the last use and must be marked kill.
826 virtual void storeRegToStackSlot(MachineBasicBlock &MBB,
827 MachineBasicBlock::iterator MI,
828 unsigned SrcReg, bool isKill, int FrameIndex,
829 const TargetRegisterClass *RC,
830 const TargetRegisterInfo *TRI) const {
831 llvm_unreachable("Target didn't implement "
832 "TargetInstrInfo::storeRegToStackSlot!");
835 /// Load the specified register of the given register class from the specified
836 /// stack frame index. The load instruction is to be added to the given
837 /// machine basic block before the specified machine instruction.
838 virtual void loadRegFromStackSlot(MachineBasicBlock &MBB,
839 MachineBasicBlock::iterator MI,
840 unsigned DestReg, int FrameIndex,
841 const TargetRegisterClass *RC,
842 const TargetRegisterInfo *TRI) const {
843 llvm_unreachable("Target didn't implement "
844 "TargetInstrInfo::loadRegFromStackSlot!");
847 /// This function is called for all pseudo instructions
848 /// that remain after register allocation. Many pseudo instructions are
849 /// created to help register allocation. This is the place to convert them
850 /// into real instructions. The target can edit MI in place, or it can insert
851 /// new instructions and erase MI. The function should return true if
852 /// anything was changed.
853 virtual bool expandPostRAPseudo(MachineInstr &MI) const { return false; }
855 /// Check whether the target can fold a load that feeds a subreg operand
856 /// (or a subreg operand that feeds a store).
857 /// For example, X86 may want to return true if it can fold
858 /// movl (%esp), %eax
863 /// Ideally, we'd like the target implementation of foldMemoryOperand() to
864 /// reject subregs - but since this behavior used to be enforced in the
865 /// target-independent code, moving this responsibility to the targets
866 /// has the potential of causing nasty silent breakage in out-of-tree targets.
867 virtual bool isSubregFoldable() const { return false; }
869 /// Attempt to fold a load or store of the specified stack
870 /// slot into the specified machine instruction for the specified operand(s).
871 /// If this is possible, a new instruction is returned with the specified
872 /// operand folded, otherwise NULL is returned.
873 /// The new instruction is inserted before MI, and the client is responsible
874 /// for removing the old instruction.
875 MachineInstr *foldMemoryOperand(MachineInstr &MI, ArrayRef<unsigned> Ops,
877 LiveIntervals *LIS = nullptr) const;
879 /// Same as the previous version except it allows folding of any load and
880 /// store from / to any address, not just from a specific stack slot.
881 MachineInstr *foldMemoryOperand(MachineInstr &MI, ArrayRef<unsigned> Ops,
882 MachineInstr &LoadMI,
883 LiveIntervals *LIS = nullptr) const;
885 /// Return true when there is potentially a faster code sequence
886 /// for an instruction chain ending in \p Root. All potential patterns are
887 /// returned in the \p Pattern vector. Pattern should be sorted in priority
888 /// order since the pattern evaluator stops checking as soon as it finds a
890 /// \param Root - Instruction that could be combined with one of its operands
891 /// \param Patterns - Vector of possible combination patterns
892 virtual bool getMachineCombinerPatterns(
894 SmallVectorImpl<MachineCombinerPattern> &Patterns) const;
896 /// Return true when a code sequence can improve throughput. It
897 /// should be called only for instructions in loops.
898 /// \param Pattern - combiner pattern
899 virtual bool isThroughputPattern(MachineCombinerPattern Pattern) const;
901 /// Return true if the input \P Inst is part of a chain of dependent ops
902 /// that are suitable for reassociation, otherwise return false.
903 /// If the instruction's operands must be commuted to have a previous
904 /// instruction of the same type define the first source operand, \P Commuted
905 /// will be set to true.
906 bool isReassociationCandidate(const MachineInstr &Inst, bool &Commuted) const;
908 /// Return true when \P Inst is both associative and commutative.
909 virtual bool isAssociativeAndCommutative(const MachineInstr &Inst) const {
913 /// Return true when \P Inst has reassociable operands in the same \P MBB.
914 virtual bool hasReassociableOperands(const MachineInstr &Inst,
915 const MachineBasicBlock *MBB) const;
917 /// Return true when \P Inst has reassociable sibling.
918 bool hasReassociableSibling(const MachineInstr &Inst, bool &Commuted) const;
920 /// When getMachineCombinerPatterns() finds patterns, this function generates
921 /// the instructions that could replace the original code sequence. The client
922 /// has to decide whether the actual replacement is beneficial or not.
923 /// \param Root - Instruction that could be combined with one of its operands
924 /// \param Pattern - Combination pattern for Root
925 /// \param InsInstrs - Vector of new instructions that implement P
926 /// \param DelInstrs - Old instructions, including Root, that could be
927 /// replaced by InsInstr
928 /// \param InstrIdxForVirtReg - map of virtual register to instruction in
929 /// InsInstr that defines it
930 virtual void genAlternativeCodeSequence(
931 MachineInstr &Root, MachineCombinerPattern Pattern,
932 SmallVectorImpl<MachineInstr *> &InsInstrs,
933 SmallVectorImpl<MachineInstr *> &DelInstrs,
934 DenseMap<unsigned, unsigned> &InstrIdxForVirtReg) const;
936 /// Attempt to reassociate \P Root and \P Prev according to \P Pattern to
937 /// reduce critical path length.
938 void reassociateOps(MachineInstr &Root, MachineInstr &Prev,
939 MachineCombinerPattern Pattern,
940 SmallVectorImpl<MachineInstr *> &InsInstrs,
941 SmallVectorImpl<MachineInstr *> &DelInstrs,
942 DenseMap<unsigned, unsigned> &InstrIdxForVirtReg) const;
944 /// This is an architecture-specific helper function of reassociateOps.
945 /// Set special operand attributes for new instructions after reassociation.
946 virtual void setSpecialOperandAttr(MachineInstr &OldMI1, MachineInstr &OldMI2,
947 MachineInstr &NewMI1,
948 MachineInstr &NewMI2) const {}
950 /// Return true when a target supports MachineCombiner.
951 virtual bool useMachineCombiner() const { return false; }
953 /// Return true if the given SDNode can be copied during scheduling
954 /// even if it has glue.
955 virtual bool canCopyGluedNodeDuringSchedule(SDNode *N) const { return false; }
958 /// Target-dependent implementation for foldMemoryOperand.
959 /// Target-independent code in foldMemoryOperand will
960 /// take care of adding a MachineMemOperand to the newly created instruction.
961 /// The instruction and any auxiliary instructions necessary will be inserted
963 virtual MachineInstr *
964 foldMemoryOperandImpl(MachineFunction &MF, MachineInstr &MI,
965 ArrayRef<unsigned> Ops,
966 MachineBasicBlock::iterator InsertPt, int FrameIndex,
967 LiveIntervals *LIS = nullptr) const {
971 /// Target-dependent implementation for foldMemoryOperand.
972 /// Target-independent code in foldMemoryOperand will
973 /// take care of adding a MachineMemOperand to the newly created instruction.
974 /// The instruction and any auxiliary instructions necessary will be inserted
976 virtual MachineInstr *foldMemoryOperandImpl(
977 MachineFunction &MF, MachineInstr &MI, ArrayRef<unsigned> Ops,
978 MachineBasicBlock::iterator InsertPt, MachineInstr &LoadMI,
979 LiveIntervals *LIS = nullptr) const {
983 /// \brief Target-dependent implementation of getRegSequenceInputs.
985 /// \returns true if it is possible to build the equivalent
986 /// REG_SEQUENCE inputs with the pair \p MI, \p DefIdx. False otherwise.
988 /// \pre MI.isRegSequenceLike().
990 /// \see TargetInstrInfo::getRegSequenceInputs.
991 virtual bool getRegSequenceLikeInputs(
992 const MachineInstr &MI, unsigned DefIdx,
993 SmallVectorImpl<RegSubRegPairAndIdx> &InputRegs) const {
997 /// \brief Target-dependent implementation of getExtractSubregInputs.
999 /// \returns true if it is possible to build the equivalent
1000 /// EXTRACT_SUBREG inputs with the pair \p MI, \p DefIdx. False otherwise.
1002 /// \pre MI.isExtractSubregLike().
1004 /// \see TargetInstrInfo::getExtractSubregInputs.
1005 virtual bool getExtractSubregLikeInputs(const MachineInstr &MI,
1007 RegSubRegPairAndIdx &InputReg) const {
1011 /// \brief Target-dependent implementation of getInsertSubregInputs.
1013 /// \returns true if it is possible to build the equivalent
1014 /// INSERT_SUBREG inputs with the pair \p MI, \p DefIdx. False otherwise.
1016 /// \pre MI.isInsertSubregLike().
1018 /// \see TargetInstrInfo::getInsertSubregInputs.
1020 getInsertSubregLikeInputs(const MachineInstr &MI, unsigned DefIdx,
1021 RegSubRegPair &BaseReg,
1022 RegSubRegPairAndIdx &InsertedReg) const {
1027 /// getAddressSpaceForPseudoSourceKind - Given the kind of memory
1028 /// (e.g. stack) the target returns the corresponding address space.
1030 getAddressSpaceForPseudoSourceKind(PseudoSourceValue::PSVKind Kind) const {
1034 /// unfoldMemoryOperand - Separate a single instruction which folded a load or
1035 /// a store or a load and a store into two or more instruction. If this is
1036 /// possible, returns true as well as the new instructions by reference.
1038 unfoldMemoryOperand(MachineFunction &MF, MachineInstr &MI, unsigned Reg,
1039 bool UnfoldLoad, bool UnfoldStore,
1040 SmallVectorImpl<MachineInstr *> &NewMIs) const {
1044 virtual bool unfoldMemoryOperand(SelectionDAG &DAG, SDNode *N,
1045 SmallVectorImpl<SDNode *> &NewNodes) const {
1049 /// Returns the opcode of the would be new
1050 /// instruction after load / store are unfolded from an instruction of the
1051 /// specified opcode. It returns zero if the specified unfolding is not
1052 /// possible. If LoadRegIndex is non-null, it is filled in with the operand
1053 /// index of the operand which will hold the register holding the loaded
1056 getOpcodeAfterMemoryUnfold(unsigned Opc, bool UnfoldLoad, bool UnfoldStore,
1057 unsigned *LoadRegIndex = nullptr) const {
1061 /// This is used by the pre-regalloc scheduler to determine if two loads are
1062 /// loading from the same base address. It should only return true if the base
1063 /// pointers are the same and the only differences between the two addresses
1064 /// are the offset. It also returns the offsets by reference.
1065 virtual bool areLoadsFromSameBasePtr(SDNode *Load1, SDNode *Load2,
1067 int64_t &Offset2) const {
1071 /// This is a used by the pre-regalloc scheduler to determine (in conjunction
1072 /// with areLoadsFromSameBasePtr) if two loads should be scheduled together.
1073 /// On some targets if two loads are loading from
1074 /// addresses in the same cache line, it's better if they are scheduled
1075 /// together. This function takes two integers that represent the load offsets
1076 /// from the common base address. It returns true if it decides it's desirable
1077 /// to schedule the two loads together. "NumLoads" is the number of loads that
1078 /// have already been scheduled after Load1.
1079 virtual bool shouldScheduleLoadsNear(SDNode *Load1, SDNode *Load2,
1080 int64_t Offset1, int64_t Offset2,
1081 unsigned NumLoads) const {
1085 /// Get the base register and byte offset of an instruction that reads/writes
1087 virtual bool getMemOpBaseRegImmOfs(MachineInstr &MemOp, unsigned &BaseReg,
1089 const TargetRegisterInfo *TRI) const {
1093 /// Return true if the instruction contains a base register and offset. If
1094 /// true, the function also sets the operand position in the instruction
1095 /// for the base register and offset.
1096 virtual bool getBaseAndOffsetPosition(const MachineInstr &MI,
1098 unsigned &OffsetPos) const {
1102 /// If the instruction is an increment of a constant value, return the amount.
1103 virtual bool getIncrementValue(const MachineInstr &MI, int &Value) const {
1107 /// Returns true if the two given memory operations should be scheduled
1108 /// adjacent. Note that you have to add:
1109 /// DAG->addMutation(createLoadClusterDAGMutation(DAG->TII, DAG->TRI));
1111 /// DAG->addMutation(createStoreClusterDAGMutation(DAG->TII, DAG->TRI));
1112 /// to TargetPassConfig::createMachineScheduler() to have an effect.
1113 virtual bool shouldClusterMemOps(MachineInstr &FirstLdSt, unsigned BaseReg1,
1114 MachineInstr &SecondLdSt, unsigned BaseReg2,
1115 unsigned NumLoads) const {
1116 llvm_unreachable("target did not implement shouldClusterMemOps()");
1119 /// Reverses the branch condition of the specified condition list,
1120 /// returning false on success and true if it cannot be reversed.
1122 reverseBranchCondition(SmallVectorImpl<MachineOperand> &Cond) const {
1126 /// Insert a noop into the instruction stream at the specified point.
1127 virtual void insertNoop(MachineBasicBlock &MBB,
1128 MachineBasicBlock::iterator MI) const;
1130 /// Return the noop instruction to use for a noop.
1131 virtual void getNoop(MCInst &NopInst) const;
1133 /// Return true for post-incremented instructions.
1134 virtual bool isPostIncrement(const MachineInstr &MI) const { return false; }
1136 /// Returns true if the instruction is already predicated.
1137 virtual bool isPredicated(const MachineInstr &MI) const { return false; }
1139 /// Returns true if the instruction is a
1140 /// terminator instruction that has not been predicated.
1141 virtual bool isUnpredicatedTerminator(const MachineInstr &MI) const;
1143 /// Returns true if MI is an unconditional tail call.
1144 virtual bool isUnconditionalTailCall(const MachineInstr &MI) const {
1148 /// Returns true if the tail call can be made conditional on BranchCond.
1149 virtual bool canMakeTailCallConditional(SmallVectorImpl<MachineOperand> &Cond,
1150 const MachineInstr &TailCall) const {
1154 /// Replace the conditional branch in MBB with a conditional tail call.
1155 virtual void replaceBranchWithTailCall(MachineBasicBlock &MBB,
1156 SmallVectorImpl<MachineOperand> &Cond,
1157 const MachineInstr &TailCall) const {
1158 llvm_unreachable("Target didn't implement replaceBranchWithTailCall!");
1161 /// Convert the instruction into a predicated instruction.
1162 /// It returns true if the operation was successful.
1163 virtual bool PredicateInstruction(MachineInstr &MI,
1164 ArrayRef<MachineOperand> Pred) const;
1166 /// Returns true if the first specified predicate
1167 /// subsumes the second, e.g. GE subsumes GT.
1168 virtual bool SubsumesPredicate(ArrayRef<MachineOperand> Pred1,
1169 ArrayRef<MachineOperand> Pred2) const {
1173 /// If the specified instruction defines any predicate
1174 /// or condition code register(s) used for predication, returns true as well
1175 /// as the definition predicate(s) by reference.
1176 virtual bool DefinesPredicate(MachineInstr &MI,
1177 std::vector<MachineOperand> &Pred) const {
1181 /// Return true if the specified instruction can be predicated.
1182 /// By default, this returns true for every instruction with a
1183 /// PredicateOperand.
1184 virtual bool isPredicable(const MachineInstr &MI) const {
1185 return MI.getDesc().isPredicable();
1188 /// Return true if it's safe to move a machine
1189 /// instruction that defines the specified register class.
1190 virtual bool isSafeToMoveRegClassDefs(const TargetRegisterClass *RC) const {
1194 /// Test if the given instruction should be considered a scheduling boundary.
1195 /// This primarily includes labels and terminators.
1196 virtual bool isSchedulingBoundary(const MachineInstr &MI,
1197 const MachineBasicBlock *MBB,
1198 const MachineFunction &MF) const;
1200 /// Measure the specified inline asm to determine an approximation of its
1202 virtual unsigned getInlineAsmLength(const char *Str,
1203 const MCAsmInfo &MAI) const;
1205 /// Allocate and return a hazard recognizer to use for this target when
1206 /// scheduling the machine instructions before register allocation.
1207 virtual ScheduleHazardRecognizer *
1208 CreateTargetHazardRecognizer(const TargetSubtargetInfo *STI,
1209 const ScheduleDAG *DAG) const;
1211 /// Allocate and return a hazard recognizer to use for this target when
1212 /// scheduling the machine instructions before register allocation.
1213 virtual ScheduleHazardRecognizer *
1214 CreateTargetMIHazardRecognizer(const InstrItineraryData *,
1215 const ScheduleDAG *DAG) const;
1217 /// Allocate and return a hazard recognizer to use for this target when
1218 /// scheduling the machine instructions after register allocation.
1219 virtual ScheduleHazardRecognizer *
1220 CreateTargetPostRAHazardRecognizer(const InstrItineraryData *,
1221 const ScheduleDAG *DAG) const;
1223 /// Allocate and return a hazard recognizer to use for by non-scheduling
1225 virtual ScheduleHazardRecognizer *
1226 CreateTargetPostRAHazardRecognizer(const MachineFunction &MF) const {
1230 /// Provide a global flag for disabling the PreRA hazard recognizer that
1231 /// targets may choose to honor.
1232 bool usePreRAHazardRecognizer() const;
1234 /// For a comparison instruction, return the source registers
1235 /// in SrcReg and SrcReg2 if having two register operands, and the value it
1236 /// compares against in CmpValue. Return true if the comparison instruction
1237 /// can be analyzed.
1238 virtual bool analyzeCompare(const MachineInstr &MI, unsigned &SrcReg,
1239 unsigned &SrcReg2, int &Mask, int &Value) const {
1243 /// See if the comparison instruction can be converted
1244 /// into something more efficient. E.g., on ARM most instructions can set the
1245 /// flags register, obviating the need for a separate CMP.
1246 virtual bool optimizeCompareInstr(MachineInstr &CmpInstr, unsigned SrcReg,
1247 unsigned SrcReg2, int Mask, int Value,
1248 const MachineRegisterInfo *MRI) const {
1251 virtual bool optimizeCondBranch(MachineInstr &MI) const { return false; }
1253 /// Try to remove the load by folding it to a register operand at the use.
1254 /// We fold the load instructions if and only if the
1255 /// def and use are in the same BB. We only look at one load and see
1256 /// whether it can be folded into MI. FoldAsLoadDefReg is the virtual register
1257 /// defined by the load we are trying to fold. DefMI returns the machine
1258 /// instruction that defines FoldAsLoadDefReg, and the function returns
1259 /// the machine instruction generated due to folding.
1260 virtual MachineInstr *optimizeLoadInstr(MachineInstr &MI,
1261 const MachineRegisterInfo *MRI,
1262 unsigned &FoldAsLoadDefReg,
1263 MachineInstr *&DefMI) const {
1267 /// 'Reg' is known to be defined by a move immediate instruction,
1268 /// try to fold the immediate into the use instruction.
1269 /// If MRI->hasOneNonDBGUse(Reg) is true, and this function returns true,
1270 /// then the caller may assume that DefMI has been erased from its parent
1271 /// block. The caller may assume that it will not be erased by this
1272 /// function otherwise.
1273 virtual bool FoldImmediate(MachineInstr &UseMI, MachineInstr &DefMI,
1274 unsigned Reg, MachineRegisterInfo *MRI) const {
1278 /// Return the number of u-operations the given machine
1279 /// instruction will be decoded to on the target cpu. The itinerary's
1280 /// IssueWidth is the number of microops that can be dispatched each
1281 /// cycle. An instruction with zero microops takes no dispatch resources.
1282 virtual unsigned getNumMicroOps(const InstrItineraryData *ItinData,
1283 const MachineInstr &MI) const;
1285 /// Return true for pseudo instructions that don't consume any
1286 /// machine resources in their current form. These are common cases that the
1287 /// scheduler should consider free, rather than conservatively handling them
1288 /// as instructions with no itinerary.
1289 bool isZeroCost(unsigned Opcode) const {
1290 return Opcode <= TargetOpcode::COPY;
1293 virtual int getOperandLatency(const InstrItineraryData *ItinData,
1294 SDNode *DefNode, unsigned DefIdx,
1295 SDNode *UseNode, unsigned UseIdx) const;
1297 /// Compute and return the use operand latency of a given pair of def and use.
1298 /// In most cases, the static scheduling itinerary was enough to determine the
1299 /// operand latency. But it may not be possible for instructions with variable
1300 /// number of defs / uses.
1302 /// This is a raw interface to the itinerary that may be directly overridden
1303 /// by a target. Use computeOperandLatency to get the best estimate of
1305 virtual int getOperandLatency(const InstrItineraryData *ItinData,
1306 const MachineInstr &DefMI, unsigned DefIdx,
1307 const MachineInstr &UseMI,
1308 unsigned UseIdx) const;
1310 /// Compute the instruction latency of a given instruction.
1311 /// If the instruction has higher cost when predicated, it's returned via
1313 virtual unsigned getInstrLatency(const InstrItineraryData *ItinData,
1314 const MachineInstr &MI,
1315 unsigned *PredCost = nullptr) const;
1317 virtual unsigned getPredicationCost(const MachineInstr &MI) const;
1319 virtual int getInstrLatency(const InstrItineraryData *ItinData,
1320 SDNode *Node) const;
1322 /// Return the default expected latency for a def based on its opcode.
1323 unsigned defaultDefLatency(const MCSchedModel &SchedModel,
1324 const MachineInstr &DefMI) const;
1326 int computeDefOperandLatency(const InstrItineraryData *ItinData,
1327 const MachineInstr &DefMI) const;
1329 /// Return true if this opcode has high latency to its result.
1330 virtual bool isHighLatencyDef(int opc) const { return false; }
1332 /// Compute operand latency between a def of 'Reg'
1333 /// and a use in the current loop. Return true if the target considered
1334 /// it 'high'. This is used by optimization passes such as machine LICM to
1335 /// determine whether it makes sense to hoist an instruction out even in a
1336 /// high register pressure situation.
1337 virtual bool hasHighOperandLatency(const TargetSchedModel &SchedModel,
1338 const MachineRegisterInfo *MRI,
1339 const MachineInstr &DefMI, unsigned DefIdx,
1340 const MachineInstr &UseMI,
1341 unsigned UseIdx) const {
1345 /// Compute operand latency of a def of 'Reg'. Return true
1346 /// if the target considered it 'low'.
1347 virtual bool hasLowDefLatency(const TargetSchedModel &SchedModel,
1348 const MachineInstr &DefMI,
1349 unsigned DefIdx) const;
1351 /// Perform target-specific instruction verification.
1352 virtual bool verifyInstruction(const MachineInstr &MI,
1353 StringRef &ErrInfo) const {
1357 /// Return the current execution domain and bit mask of
1358 /// possible domains for instruction.
1360 /// Some micro-architectures have multiple execution domains, and multiple
1361 /// opcodes that perform the same operation in different domains. For
1362 /// example, the x86 architecture provides the por, orps, and orpd
1363 /// instructions that all do the same thing. There is a latency penalty if a
1364 /// register is written in one domain and read in another.
1366 /// This function returns a pair (domain, mask) containing the execution
1367 /// domain of MI, and a bit mask of possible domains. The setExecutionDomain
1368 /// function can be used to change the opcode to one of the domains in the
1369 /// bit mask. Instructions whose execution domain can't be changed should
1370 /// return a 0 mask.
1372 /// The execution domain numbers don't have any special meaning except domain
1373 /// 0 is used for instructions that are not associated with any interesting
1374 /// execution domain.
1376 virtual std::pair<uint16_t, uint16_t>
1377 getExecutionDomain(const MachineInstr &MI) const {
1378 return std::make_pair(0, 0);
1381 /// Change the opcode of MI to execute in Domain.
1383 /// The bit (1 << Domain) must be set in the mask returned from
1384 /// getExecutionDomain(MI).
1385 virtual void setExecutionDomain(MachineInstr &MI, unsigned Domain) const {}
1387 /// Returns the preferred minimum clearance
1388 /// before an instruction with an unwanted partial register update.
1390 /// Some instructions only write part of a register, and implicitly need to
1391 /// read the other parts of the register. This may cause unwanted stalls
1392 /// preventing otherwise unrelated instructions from executing in parallel in
1393 /// an out-of-order CPU.
1395 /// For example, the x86 instruction cvtsi2ss writes its result to bits
1396 /// [31:0] of the destination xmm register. Bits [127:32] are unaffected, so
1397 /// the instruction needs to wait for the old value of the register to become
1400 /// addps %xmm1, %xmm0
1401 /// movaps %xmm0, (%rax)
1402 /// cvtsi2ss %rbx, %xmm0
1404 /// In the code above, the cvtsi2ss instruction needs to wait for the addps
1405 /// instruction before it can issue, even though the high bits of %xmm0
1406 /// probably aren't needed.
1408 /// This hook returns the preferred clearance before MI, measured in
1409 /// instructions. Other defs of MI's operand OpNum are avoided in the last N
1410 /// instructions before MI. It should only return a positive value for
1411 /// unwanted dependencies. If the old bits of the defined register have
1412 /// useful values, or if MI is determined to otherwise read the dependency,
1413 /// the hook should return 0.
1415 /// The unwanted dependency may be handled by:
1417 /// 1. Allocating the same register for an MI def and use. That makes the
1418 /// unwanted dependency identical to a required dependency.
1420 /// 2. Allocating a register for the def that has no defs in the previous N
1423 /// 3. Calling breakPartialRegDependency() with the same arguments. This
1424 /// allows the target to insert a dependency breaking instruction.
1427 getPartialRegUpdateClearance(const MachineInstr &MI, unsigned OpNum,
1428 const TargetRegisterInfo *TRI) const {
1429 // The default implementation returns 0 for no partial register dependency.
1433 /// \brief Return the minimum clearance before an instruction that reads an
1434 /// unused register.
1436 /// For example, AVX instructions may copy part of a register operand into
1437 /// the unused high bits of the destination register.
1439 /// vcvtsi2sdq %rax, undef %xmm0, %xmm14
1441 /// In the code above, vcvtsi2sdq copies %xmm0[127:64] into %xmm14 creating a
1442 /// false dependence on any previous write to %xmm0.
1444 /// This hook works similarly to getPartialRegUpdateClearance, except that it
1445 /// does not take an operand index. Instead sets \p OpNum to the index of the
1446 /// unused register.
1447 virtual unsigned getUndefRegClearance(const MachineInstr &MI, unsigned &OpNum,
1448 const TargetRegisterInfo *TRI) const {
1449 // The default implementation returns 0 for no undef register dependency.
1453 /// Insert a dependency-breaking instruction
1454 /// before MI to eliminate an unwanted dependency on OpNum.
1456 /// If it wasn't possible to avoid a def in the last N instructions before MI
1457 /// (see getPartialRegUpdateClearance), this hook will be called to break the
1458 /// unwanted dependency.
1460 /// On x86, an xorps instruction can be used as a dependency breaker:
1462 /// addps %xmm1, %xmm0
1463 /// movaps %xmm0, (%rax)
1464 /// xorps %xmm0, %xmm0
1465 /// cvtsi2ss %rbx, %xmm0
1467 /// An <imp-kill> operand should be added to MI if an instruction was
1468 /// inserted. This ties the instructions together in the post-ra scheduler.
1470 virtual void breakPartialRegDependency(MachineInstr &MI, unsigned OpNum,
1471 const TargetRegisterInfo *TRI) const {}
1473 /// Create machine specific model for scheduling.
1474 virtual DFAPacketizer *
1475 CreateTargetScheduleState(const TargetSubtargetInfo &) const {
1479 /// Sometimes, it is possible for the target
1480 /// to tell, even without aliasing information, that two MIs access different
1481 /// memory addresses. This function returns true if two MIs access different
1482 /// memory addresses and false otherwise.
1484 /// Assumes any physical registers used to compute addresses have the same
1485 /// value for both instructions. (This is the most useful assumption for
1486 /// post-RA scheduling.)
1488 /// See also MachineInstr::mayAlias, which is implemented on top of this
1491 areMemAccessesTriviallyDisjoint(MachineInstr &MIa, MachineInstr &MIb,
1492 AliasAnalysis *AA = nullptr) const {
1493 assert((MIa.mayLoad() || MIa.mayStore()) &&
1494 "MIa must load from or modify a memory location");
1495 assert((MIb.mayLoad() || MIb.mayStore()) &&
1496 "MIb must load from or modify a memory location");
1500 /// \brief Return the value to use for the MachineCSE's LookAheadLimit,
1501 /// which is a heuristic used for CSE'ing phys reg defs.
1502 virtual unsigned getMachineCSELookAheadLimit() const {
1503 // The default lookahead is small to prevent unprofitable quadratic
1508 /// Return an array that contains the ids of the target indices (used for the
1509 /// TargetIndex machine operand) and their names.
1511 /// MIR Serialization is able to serialize only the target indices that are
1512 /// defined by this method.
1513 virtual ArrayRef<std::pair<int, const char *>>
1514 getSerializableTargetIndices() const {
1518 /// Decompose the machine operand's target flags into two values - the direct
1519 /// target flag value and any of bit flags that are applied.
1520 virtual std::pair<unsigned, unsigned>
1521 decomposeMachineOperandsTargetFlags(unsigned /*TF*/) const {
1522 return std::make_pair(0u, 0u);
1525 /// Return an array that contains the direct target flag values and their
1528 /// MIR Serialization is able to serialize only the target flags that are
1529 /// defined by this method.
1530 virtual ArrayRef<std::pair<unsigned, const char *>>
1531 getSerializableDirectMachineOperandTargetFlags() const {
1535 /// Return an array that contains the bitmask target flag values and their
1538 /// MIR Serialization is able to serialize only the target flags that are
1539 /// defined by this method.
1540 virtual ArrayRef<std::pair<unsigned, const char *>>
1541 getSerializableBitmaskMachineOperandTargetFlags() const {
1545 /// Return an array that contains the MMO target flag values and their
1548 /// MIR Serialization is able to serialize only the MMO target flags that are
1549 /// defined by this method.
1550 virtual ArrayRef<std::pair<MachineMemOperand::Flags, const char *>>
1551 getSerializableMachineMemOperandTargetFlags() const {
1555 /// Determines whether \p Inst is a tail call instruction. Override this
1556 /// method on targets that do not properly set MCID::Return and MCID::Call on
1557 /// tail call instructions."
1558 virtual bool isTailCall(const MachineInstr &Inst) const {
1559 return Inst.isReturn() && Inst.isCall();
1562 /// True if the instruction is bound to the top of its basic block and no
1563 /// other instructions shall be inserted before it. This can be implemented
1564 /// to prevent register allocator to insert spills before such instructions.
1565 virtual bool isBasicBlockPrologue(const MachineInstr &MI) const {
1569 /// \brief Describes the number of instructions that it will take to call and
1570 /// construct a frame for a given outlining candidate.
1571 struct MachineOutlinerInfo {
1572 /// Number of instructions to call an outlined function for this candidate.
1573 unsigned CallOverhead;
1575 /// \brief Number of instructions to construct an outlined function frame
1576 /// for this candidate.
1577 unsigned FrameOverhead;
1579 /// \brief Represents the specific instructions that must be emitted to
1580 /// construct a call to this candidate.
1581 unsigned CallConstructionID;
1583 /// \brief Represents the specific instructions that must be emitted to
1584 /// construct a frame for this candidate's outlined function.
1585 unsigned FrameConstructionID;
1587 MachineOutlinerInfo() {}
1588 MachineOutlinerInfo(unsigned CallOverhead, unsigned FrameOverhead,
1589 unsigned CallConstructionID,
1590 unsigned FrameConstructionID)
1591 : CallOverhead(CallOverhead), FrameOverhead(FrameOverhead),
1592 CallConstructionID(CallConstructionID),
1593 FrameConstructionID(FrameConstructionID) {}
1596 /// \brief Returns a \p MachineOutlinerInfo struct containing target-specific
1597 /// information for a set of outlining candidates.
1598 virtual MachineOutlinerInfo getOutlininingCandidateInfo(
1600 std::pair<MachineBasicBlock::iterator, MachineBasicBlock::iterator>>
1601 &RepeatedSequenceLocs) const {
1603 "Target didn't implement TargetInstrInfo::getOutliningOverhead!");
1606 /// Represents how an instruction should be mapped by the outliner.
1607 /// \p Legal instructions are those which are safe to outline.
1608 /// \p Illegal instructions are those which cannot be outlined.
1609 /// \p Invisible instructions are instructions which can be outlined, but
1610 /// shouldn't actually impact the outlining result.
1611 enum MachineOutlinerInstrType { Legal, Illegal, Invisible };
1613 /// Returns how or if \p MI should be outlined.
1614 virtual MachineOutlinerInstrType getOutliningType(MachineInstr &MI) const {
1616 "Target didn't implement TargetInstrInfo::getOutliningType!");
1619 /// Insert a custom epilogue for outlined functions.
1620 /// This may be empty, in which case no epilogue or return statement will be
1622 virtual void insertOutlinerEpilogue(MachineBasicBlock &MBB,
1623 MachineFunction &MF,
1624 const MachineOutlinerInfo &MInfo) const {
1626 "Target didn't implement TargetInstrInfo::insertOutlinerEpilogue!");
1629 /// Insert a call to an outlined function into the program.
1630 /// Returns an iterator to the spot where we inserted the call. This must be
1631 /// implemented by the target.
1632 virtual MachineBasicBlock::iterator
1633 insertOutlinedCall(Module &M, MachineBasicBlock &MBB,
1634 MachineBasicBlock::iterator &It, MachineFunction &MF,
1635 const MachineOutlinerInfo &MInfo) const {
1637 "Target didn't implement TargetInstrInfo::insertOutlinedCall!");
1640 /// Insert a custom prologue for outlined functions.
1641 /// This may be empty, in which case no prologue will be emitted.
1642 virtual void insertOutlinerPrologue(MachineBasicBlock &MBB,
1643 MachineFunction &MF,
1644 const MachineOutlinerInfo &MInfo) const {
1646 "Target didn't implement TargetInstrInfo::insertOutlinerPrologue!");
1649 /// Return true if the function can safely be outlined from.
1650 /// A function \p MF is considered safe for outlining if an outlined function
1651 /// produced from instructions in F will produce a program which produces the
1652 /// same output for any set of given inputs.
1653 virtual bool isFunctionSafeToOutlineFrom(MachineFunction &MF,
1654 bool OutlineFromLinkOnceODRs) const {
1655 llvm_unreachable("Target didn't implement "
1656 "TargetInstrInfo::isFunctionSafeToOutlineFrom!");
1660 unsigned CallFrameSetupOpcode, CallFrameDestroyOpcode;
1661 unsigned CatchRetOpcode;
1662 unsigned ReturnOpcode;
1665 /// \brief Provide DenseMapInfo for TargetInstrInfo::RegSubRegPair.
1666 template <> struct DenseMapInfo<TargetInstrInfo::RegSubRegPair> {
1667 using RegInfo = DenseMapInfo<unsigned>;
1669 static inline TargetInstrInfo::RegSubRegPair getEmptyKey() {
1670 return TargetInstrInfo::RegSubRegPair(RegInfo::getEmptyKey(),
1671 RegInfo::getEmptyKey());
1674 static inline TargetInstrInfo::RegSubRegPair getTombstoneKey() {
1675 return TargetInstrInfo::RegSubRegPair(RegInfo::getTombstoneKey(),
1676 RegInfo::getTombstoneKey());
1679 /// \brief Reuse getHashValue implementation from
1680 /// std::pair<unsigned, unsigned>.
1681 static unsigned getHashValue(const TargetInstrInfo::RegSubRegPair &Val) {
1682 std::pair<unsigned, unsigned> PairVal = std::make_pair(Val.Reg, Val.SubReg);
1683 return DenseMapInfo<std::pair<unsigned, unsigned>>::getHashValue(PairVal);
1686 static bool isEqual(const TargetInstrInfo::RegSubRegPair &LHS,
1687 const TargetInstrInfo::RegSubRegPair &RHS) {
1688 return RegInfo::isEqual(LHS.Reg, RHS.Reg) &&
1689 RegInfo::isEqual(LHS.SubReg, RHS.SubReg);
1693 } // end namespace llvm
1695 #endif // LLVM_TARGET_TARGETINSTRINFO_H