LLVM  12.0.0git
X86FixupLEAs.cpp
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1 //===-- X86FixupLEAs.cpp - use or replace LEA instructions -----------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // This file defines the pass that finds instructions that can be
10 // re-written as LEA instructions in order to reduce pipeline delays.
11 // It replaces LEAs with ADD/INC/DEC when that is better for size/speed.
12 //
13 //===----------------------------------------------------------------------===//
14 
15 #include "X86.h"
16 #include "X86InstrInfo.h"
17 #include "X86Subtarget.h"
18 #include "llvm/ADT/Statistic.h"
24 #include "llvm/CodeGen/Passes.h"
26 #include "llvm/Support/Debug.h"
28 using namespace llvm;
29 
30 #define FIXUPLEA_DESC "X86 LEA Fixup"
31 #define FIXUPLEA_NAME "x86-fixup-LEAs"
32 
33 #define DEBUG_TYPE FIXUPLEA_NAME
34 
35 STATISTIC(NumLEAs, "Number of LEA instructions created");
36 
37 namespace {
38 class FixupLEAPass : public MachineFunctionPass {
39  enum RegUsageState { RU_NotUsed, RU_Write, RU_Read };
40 
41  /// Given a machine register, look for the instruction
42  /// which writes it in the current basic block. If found,
43  /// try to replace it with an equivalent LEA instruction.
44  /// If replacement succeeds, then also process the newly created
45  /// instruction.
46  void seekLEAFixup(MachineOperand &p, MachineBasicBlock::iterator &I,
48 
49  /// Given a memory access or LEA instruction
50  /// whose address mode uses a base and/or index register, look for
51  /// an opportunity to replace the instruction which sets the base or index
52  /// register with an equivalent LEA instruction.
53  void processInstruction(MachineBasicBlock::iterator &I,
55 
56  /// Given a LEA instruction which is unprofitable
57  /// on SlowLEA targets try to replace it with an equivalent ADD instruction.
58  void processInstructionForSlowLEA(MachineBasicBlock::iterator &I,
60 
61  /// Given a LEA instruction which is unprofitable
62  /// on SNB+ try to replace it with other instructions.
63  /// According to Intel's Optimization Reference Manual:
64  /// " For LEA instructions with three source operands and some specific
65  /// situations, instruction latency has increased to 3 cycles, and must
66  /// dispatch via port 1:
67  /// - LEA that has all three source operands: base, index, and offset
68  /// - LEA that uses base and index registers where the base is EBP, RBP,
69  /// or R13
70  /// - LEA that uses RIP relative addressing mode
71  /// - LEA that uses 16-bit addressing mode "
72  /// This function currently handles the first 2 cases only.
73  void processInstrForSlow3OpLEA(MachineBasicBlock::iterator &I,
74  MachineBasicBlock &MBB, bool OptIncDec);
75 
76  /// Look for LEAs that are really two address LEAs that we might be able to
77  /// turn into regular ADD instructions.
78  bool optTwoAddrLEA(MachineBasicBlock::iterator &I,
79  MachineBasicBlock &MBB, bool OptIncDec,
80  bool UseLEAForSP) const;
81 
82  /// Determine if an instruction references a machine register
83  /// and, if so, whether it reads or writes the register.
84  RegUsageState usesRegister(MachineOperand &p, MachineBasicBlock::iterator I);
85 
86  /// Step backwards through a basic block, looking
87  /// for an instruction which writes a register within
88  /// a maximum of INSTR_DISTANCE_THRESHOLD instruction latency cycles.
92 
93  /// if an instruction can be converted to an
94  /// equivalent LEA, insert the new instruction into the basic block
95  /// and return a pointer to it. Otherwise, return zero.
96  MachineInstr *postRAConvertToLEA(MachineBasicBlock &MBB,
98 
99 public:
100  static char ID;
101 
102  StringRef getPassName() const override { return FIXUPLEA_DESC; }
103 
104  FixupLEAPass() : MachineFunctionPass(ID) { }
105 
106  /// Loop over all of the basic blocks,
107  /// replacing instructions by equivalent LEA instructions
108  /// if needed and when possible.
109  bool runOnMachineFunction(MachineFunction &MF) override;
110 
111  // This pass runs after regalloc and doesn't support VReg operands.
112  MachineFunctionProperties getRequiredProperties() const override {
115  }
116 
117  void getAnalysisUsage(AnalysisUsage &AU) const override {
121  }
122 
123 private:
124  TargetSchedModel TSM;
125  const X86InstrInfo *TII = nullptr;
126  const X86RegisterInfo *TRI = nullptr;
127 };
128 }
129 
130 char FixupLEAPass::ID = 0;
131 
132 INITIALIZE_PASS(FixupLEAPass, FIXUPLEA_NAME, FIXUPLEA_DESC, false, false)
133 
134 MachineInstr *
135 FixupLEAPass::postRAConvertToLEA(MachineBasicBlock &MBB,
136  MachineBasicBlock::iterator &MBBI) const {
137  MachineInstr &MI = *MBBI;
138  switch (MI.getOpcode()) {
139  case X86::MOV32rr:
140  case X86::MOV64rr: {
141  const MachineOperand &Src = MI.getOperand(1);
142  const MachineOperand &Dest = MI.getOperand(0);
143  MachineInstr *NewMI =
144  BuildMI(MBB, MBBI, MI.getDebugLoc(),
145  TII->get(MI.getOpcode() == X86::MOV32rr ? X86::LEA32r
146  : X86::LEA64r))
147  .add(Dest)
148  .add(Src)
149  .addImm(1)
150  .addReg(0)
151  .addImm(0)
152  .addReg(0);
153  return NewMI;
154  }
155  }
156 
157  if (!MI.isConvertibleTo3Addr())
158  return nullptr;
159 
160  switch (MI.getOpcode()) {
161  default:
162  // Only convert instructions that we've verified are safe.
163  return nullptr;
164  case X86::ADD64ri32:
165  case X86::ADD64ri8:
166  case X86::ADD64ri32_DB:
167  case X86::ADD64ri8_DB:
168  case X86::ADD32ri:
169  case X86::ADD32ri8:
170  case X86::ADD32ri_DB:
171  case X86::ADD32ri8_DB:
172  if (!MI.getOperand(2).isImm()) {
173  // convertToThreeAddress will call getImm()
174  // which requires isImm() to be true
175  return nullptr;
176  }
177  break;
178  case X86::SHL64ri:
179  case X86::SHL32ri:
180  case X86::INC64r:
181  case X86::INC32r:
182  case X86::DEC64r:
183  case X86::DEC32r:
184  case X86::ADD64rr:
185  case X86::ADD64rr_DB:
186  case X86::ADD32rr:
187  case X86::ADD32rr_DB:
188  // These instructions are all fine to convert.
189  break;
190  }
192  return TII->convertToThreeAddress(MFI, MI, nullptr);
193 }
194 
195 FunctionPass *llvm::createX86FixupLEAs() { return new FixupLEAPass(); }
196 
197 static bool isLEA(unsigned Opcode) {
198  return Opcode == X86::LEA32r || Opcode == X86::LEA64r ||
199  Opcode == X86::LEA64_32r;
200 }
201 
202 bool FixupLEAPass::runOnMachineFunction(MachineFunction &MF) {
203  if (skipFunction(MF.getFunction()))
204  return false;
205 
206  const X86Subtarget &ST = MF.getSubtarget<X86Subtarget>();
207  bool IsSlowLEA = ST.slowLEA();
208  bool IsSlow3OpsLEA = ST.slow3OpsLEA();
209  bool LEAUsesAG = ST.LEAusesAG();
210 
211  bool OptIncDec = !ST.slowIncDec() || MF.getFunction().hasOptSize();
212  bool UseLEAForSP = ST.useLeaForSP();
213 
214  TSM.init(&ST);
215  TII = ST.getInstrInfo();
216  TRI = ST.getRegisterInfo();
217  auto *PSI = &getAnalysis<ProfileSummaryInfoWrapperPass>().getPSI();
218  auto *MBFI = (PSI && PSI->hasProfileSummary())
219  ? &getAnalysis<LazyMachineBlockFrequencyInfoPass>().getBFI()
220  : nullptr;
221 
222  LLVM_DEBUG(dbgs() << "Start X86FixupLEAs\n";);
223  for (MachineBasicBlock &MBB : MF) {
224  // First pass. Try to remove or optimize existing LEAs.
225  bool OptIncDecPerBB =
226  OptIncDec || llvm::shouldOptimizeForSize(&MBB, PSI, MBFI);
227  for (MachineBasicBlock::iterator I = MBB.begin(); I != MBB.end(); ++I) {
228  if (!isLEA(I->getOpcode()))
229  continue;
230 
231  if (optTwoAddrLEA(I, MBB, OptIncDecPerBB, UseLEAForSP))
232  continue;
233 
234  if (IsSlowLEA)
235  processInstructionForSlowLEA(I, MBB);
236  else if (IsSlow3OpsLEA)
237  processInstrForSlow3OpLEA(I, MBB, OptIncDecPerBB);
238  }
239 
240  // Second pass for creating LEAs. This may reverse some of the
241  // transformations above.
242  if (LEAUsesAG) {
243  for (MachineBasicBlock::iterator I = MBB.begin(); I != MBB.end(); ++I)
244  processInstruction(I, MBB);
245  }
246  }
247 
248  LLVM_DEBUG(dbgs() << "End X86FixupLEAs\n";);
249 
250  return true;
251 }
252 
253 FixupLEAPass::RegUsageState
254 FixupLEAPass::usesRegister(MachineOperand &p, MachineBasicBlock::iterator I) {
255  RegUsageState RegUsage = RU_NotUsed;
256  MachineInstr &MI = *I;
257 
258  for (unsigned i = 0; i < MI.getNumOperands(); ++i) {
259  MachineOperand &opnd = MI.getOperand(i);
260  if (opnd.isReg() && opnd.getReg() == p.getReg()) {
261  if (opnd.isDef())
262  return RU_Write;
263  RegUsage = RU_Read;
264  }
265  }
266  return RegUsage;
267 }
268 
269 /// getPreviousInstr - Given a reference to an instruction in a basic
270 /// block, return a reference to the previous instruction in the block,
271 /// wrapping around to the last instruction of the block if the block
272 /// branches to itself.
275  if (I == MBB.begin()) {
276  if (MBB.isPredecessor(&MBB)) {
277  I = --MBB.end();
278  return true;
279  } else
280  return false;
281  }
282  --I;
283  return true;
284 }
285 
287 FixupLEAPass::searchBackwards(MachineOperand &p, MachineBasicBlock::iterator &I,
289  int InstrDistance = 1;
291  static const int INSTR_DISTANCE_THRESHOLD = 5;
292 
293  CurInst = I;
294  bool Found;
295  Found = getPreviousInstr(CurInst, MBB);
296  while (Found && I != CurInst) {
297  if (CurInst->isCall() || CurInst->isInlineAsm())
298  break;
299  if (InstrDistance > INSTR_DISTANCE_THRESHOLD)
300  break; // too far back to make a difference
301  if (usesRegister(p, CurInst) == RU_Write) {
302  return CurInst;
303  }
304  InstrDistance += TSM.computeInstrLatency(&*CurInst);
305  Found = getPreviousInstr(CurInst, MBB);
306  }
308 }
309 
310 static inline bool isInefficientLEAReg(unsigned Reg) {
311  return Reg == X86::EBP || Reg == X86::RBP ||
312  Reg == X86::R13D || Reg == X86::R13;
313 }
314 
315 /// Returns true if this LEA uses base an index registers, and the base register
316 /// is known to be inefficient for the subtarget.
317 // TODO: use a variant scheduling class to model the latency profile
318 // of LEA instructions, and implement this logic as a scheduling predicate.
319 static inline bool hasInefficientLEABaseReg(const MachineOperand &Base,
320  const MachineOperand &Index) {
321  return Base.isReg() && isInefficientLEAReg(Base.getReg()) && Index.isReg() &&
322  Index.getReg() != X86::NoRegister;
323 }
324 
325 static inline bool hasLEAOffset(const MachineOperand &Offset) {
326  return (Offset.isImm() && Offset.getImm() != 0) || Offset.isGlobal();
327 }
328 
329 static inline unsigned getADDrrFromLEA(unsigned LEAOpcode) {
330  switch (LEAOpcode) {
331  default:
332  llvm_unreachable("Unexpected LEA instruction");
333  case X86::LEA32r:
334  case X86::LEA64_32r:
335  return X86::ADD32rr;
336  case X86::LEA64r:
337  return X86::ADD64rr;
338  }
339 }
340 
341 static inline unsigned getADDriFromLEA(unsigned LEAOpcode,
342  const MachineOperand &Offset) {
343  bool IsInt8 = Offset.isImm() && isInt<8>(Offset.getImm());
344  switch (LEAOpcode) {
345  default:
346  llvm_unreachable("Unexpected LEA instruction");
347  case X86::LEA32r:
348  case X86::LEA64_32r:
349  return IsInt8 ? X86::ADD32ri8 : X86::ADD32ri;
350  case X86::LEA64r:
351  return IsInt8 ? X86::ADD64ri8 : X86::ADD64ri32;
352  }
353 }
354 
355 static inline unsigned getINCDECFromLEA(unsigned LEAOpcode, bool IsINC) {
356  switch (LEAOpcode) {
357  default:
358  llvm_unreachable("Unexpected LEA instruction");
359  case X86::LEA32r:
360  case X86::LEA64_32r:
361  return IsINC ? X86::INC32r : X86::DEC32r;
362  case X86::LEA64r:
363  return IsINC ? X86::INC64r : X86::DEC64r;
364  }
365 }
366 
367 bool FixupLEAPass::optTwoAddrLEA(MachineBasicBlock::iterator &I,
368  MachineBasicBlock &MBB, bool OptIncDec,
369  bool UseLEAForSP) const {
370  MachineInstr &MI = *I;
371 
372  const MachineOperand &Base = MI.getOperand(1 + X86::AddrBaseReg);
373  const MachineOperand &Scale = MI.getOperand(1 + X86::AddrScaleAmt);
374  const MachineOperand &Index = MI.getOperand(1 + X86::AddrIndexReg);
375  const MachineOperand &Disp = MI.getOperand(1 + X86::AddrDisp);
376  const MachineOperand &Segment = MI.getOperand(1 + X86::AddrSegmentReg);
377 
378  if (Segment.getReg() != 0 || !Disp.isImm() || Scale.getImm() > 1 ||
379  MBB.computeRegisterLiveness(TRI, X86::EFLAGS, I) !=
381  return false;
382 
383  Register DestReg = MI.getOperand(0).getReg();
384  Register BaseReg = Base.getReg();
385  Register IndexReg = Index.getReg();
386 
387  // Don't change stack adjustment LEAs.
388  if (UseLEAForSP && (DestReg == X86::ESP || DestReg == X86::RSP))
389  return false;
390 
391  // LEA64_32 has 64-bit operands but 32-bit result.
392  if (MI.getOpcode() == X86::LEA64_32r) {
393  if (BaseReg != 0)
394  BaseReg = TRI->getSubReg(BaseReg, X86::sub_32bit);
395  if (IndexReg != 0)
396  IndexReg = TRI->getSubReg(IndexReg, X86::sub_32bit);
397  }
398 
399  MachineInstr *NewMI = nullptr;
400 
401  // Look for lea(%reg1, %reg2), %reg1 or lea(%reg2, %reg1), %reg1
402  // which can be turned into add %reg2, %reg1
403  if (BaseReg != 0 && IndexReg != 0 && Disp.getImm() == 0 &&
404  (DestReg == BaseReg || DestReg == IndexReg)) {
405  unsigned NewOpcode = getADDrrFromLEA(MI.getOpcode());
406  if (DestReg != BaseReg)
407  std::swap(BaseReg, IndexReg);
408 
409  if (MI.getOpcode() == X86::LEA64_32r) {
410  // TODO: Do we need the super register implicit use?
411  NewMI = BuildMI(MBB, I, MI.getDebugLoc(), TII->get(NewOpcode), DestReg)
412  .addReg(BaseReg).addReg(IndexReg)
413  .addReg(Base.getReg(), RegState::Implicit)
414  .addReg(Index.getReg(), RegState::Implicit);
415  } else {
416  NewMI = BuildMI(MBB, I, MI.getDebugLoc(), TII->get(NewOpcode), DestReg)
417  .addReg(BaseReg).addReg(IndexReg);
418  }
419  } else if (DestReg == BaseReg && IndexReg == 0) {
420  // This is an LEA with only a base register and a displacement,
421  // We can use ADDri or INC/DEC.
422 
423  // Does this LEA have one these forms:
424  // lea %reg, 1(%reg)
425  // lea %reg, -1(%reg)
426  if (OptIncDec && (Disp.getImm() == 1 || Disp.getImm() == -1)) {
427  bool IsINC = Disp.getImm() == 1;
428  unsigned NewOpcode = getINCDECFromLEA(MI.getOpcode(), IsINC);
429 
430  if (MI.getOpcode() == X86::LEA64_32r) {
431  // TODO: Do we need the super register implicit use?
432  NewMI = BuildMI(MBB, I, MI.getDebugLoc(), TII->get(NewOpcode), DestReg)
433  .addReg(BaseReg).addReg(Base.getReg(), RegState::Implicit);
434  } else {
435  NewMI = BuildMI(MBB, I, MI.getDebugLoc(), TII->get(NewOpcode), DestReg)
436  .addReg(BaseReg);
437  }
438  } else {
439  unsigned NewOpcode = getADDriFromLEA(MI.getOpcode(), Disp);
440  if (MI.getOpcode() == X86::LEA64_32r) {
441  // TODO: Do we need the super register implicit use?
442  NewMI = BuildMI(MBB, I, MI.getDebugLoc(), TII->get(NewOpcode), DestReg)
443  .addReg(BaseReg).addImm(Disp.getImm())
444  .addReg(Base.getReg(), RegState::Implicit);
445  } else {
446  NewMI = BuildMI(MBB, I, MI.getDebugLoc(), TII->get(NewOpcode), DestReg)
447  .addReg(BaseReg).addImm(Disp.getImm());
448  }
449  }
450  } else
451  return false;
452 
454  MBB.erase(I);
455  I = NewMI;
456  return true;
457 }
458 
459 void FixupLEAPass::processInstruction(MachineBasicBlock::iterator &I,
461  // Process a load, store, or LEA instruction.
462  MachineInstr &MI = *I;
463  const MCInstrDesc &Desc = MI.getDesc();
464  int AddrOffset = X86II::getMemoryOperandNo(Desc.TSFlags);
465  if (AddrOffset >= 0) {
466  AddrOffset += X86II::getOperandBias(Desc);
467  MachineOperand &p = MI.getOperand(AddrOffset + X86::AddrBaseReg);
468  if (p.isReg() && p.getReg() != X86::ESP) {
469  seekLEAFixup(p, I, MBB);
470  }
471  MachineOperand &q = MI.getOperand(AddrOffset + X86::AddrIndexReg);
472  if (q.isReg() && q.getReg() != X86::ESP) {
473  seekLEAFixup(q, I, MBB);
474  }
475  }
476 }
477 
478 void FixupLEAPass::seekLEAFixup(MachineOperand &p,
481  MachineBasicBlock::iterator MBI = searchBackwards(p, I, MBB);
482  if (MBI != MachineBasicBlock::iterator()) {
483  MachineInstr *NewMI = postRAConvertToLEA(MBB, MBI);
484  if (NewMI) {
485  ++NumLEAs;
486  LLVM_DEBUG(dbgs() << "FixLEA: Candidate to replace:"; MBI->dump(););
487  // now to replace with an equivalent LEA...
488  LLVM_DEBUG(dbgs() << "FixLEA: Replaced by: "; NewMI->dump(););
489  MBB.getParent()->substituteDebugValuesForInst(*MBI, *NewMI, 1);
490  MBB.erase(MBI);
492  static_cast<MachineBasicBlock::iterator>(NewMI);
493  processInstruction(J, MBB);
494  }
495  }
496 }
497 
498 void FixupLEAPass::processInstructionForSlowLEA(MachineBasicBlock::iterator &I,
500  MachineInstr &MI = *I;
501  const unsigned Opcode = MI.getOpcode();
502 
503  const MachineOperand &Dst = MI.getOperand(0);
504  const MachineOperand &Base = MI.getOperand(1 + X86::AddrBaseReg);
505  const MachineOperand &Scale = MI.getOperand(1 + X86::AddrScaleAmt);
506  const MachineOperand &Index = MI.getOperand(1 + X86::AddrIndexReg);
507  const MachineOperand &Offset = MI.getOperand(1 + X86::AddrDisp);
508  const MachineOperand &Segment = MI.getOperand(1 + X86::AddrSegmentReg);
509 
510  if (Segment.getReg() != 0 || !Offset.isImm() ||
511  MBB.computeRegisterLiveness(TRI, X86::EFLAGS, I, 4) !=
513  return;
514  const Register DstR = Dst.getReg();
515  const Register SrcR1 = Base.getReg();
516  const Register SrcR2 = Index.getReg();
517  if ((SrcR1 == 0 || SrcR1 != DstR) && (SrcR2 == 0 || SrcR2 != DstR))
518  return;
519  if (Scale.getImm() > 1)
520  return;
521  LLVM_DEBUG(dbgs() << "FixLEA: Candidate to replace:"; I->dump(););
522  LLVM_DEBUG(dbgs() << "FixLEA: Replaced by: ";);
523  MachineInstr *NewMI = nullptr;
524  // Make ADD instruction for two registers writing to LEA's destination
525  if (SrcR1 != 0 && SrcR2 != 0) {
526  const MCInstrDesc &ADDrr = TII->get(getADDrrFromLEA(Opcode));
527  const MachineOperand &Src = SrcR1 == DstR ? Index : Base;
528  NewMI =
529  BuildMI(MBB, I, MI.getDebugLoc(), ADDrr, DstR).addReg(DstR).add(Src);
530  LLVM_DEBUG(NewMI->dump(););
531  }
532  // Make ADD instruction for immediate
533  if (Offset.getImm() != 0) {
534  const MCInstrDesc &ADDri =
535  TII->get(getADDriFromLEA(Opcode, Offset));
536  const MachineOperand &SrcR = SrcR1 == DstR ? Base : Index;
537  NewMI = BuildMI(MBB, I, MI.getDebugLoc(), ADDri, DstR)
538  .add(SrcR)
539  .addImm(Offset.getImm());
540  LLVM_DEBUG(NewMI->dump(););
541  }
542  if (NewMI) {
544  MBB.erase(I);
545  I = NewMI;
546  }
547 }
548 
549 void FixupLEAPass::processInstrForSlow3OpLEA(MachineBasicBlock::iterator &I,
551  bool OptIncDec) {
552  MachineInstr &MI = *I;
553  const unsigned LEAOpcode = MI.getOpcode();
554 
555  const MachineOperand &Dest = MI.getOperand(0);
556  const MachineOperand &Base = MI.getOperand(1 + X86::AddrBaseReg);
557  const MachineOperand &Scale = MI.getOperand(1 + X86::AddrScaleAmt);
558  const MachineOperand &Index = MI.getOperand(1 + X86::AddrIndexReg);
559  const MachineOperand &Offset = MI.getOperand(1 + X86::AddrDisp);
560  const MachineOperand &Segment = MI.getOperand(1 + X86::AddrSegmentReg);
561 
562  if (!(TII->isThreeOperandsLEA(MI) || hasInefficientLEABaseReg(Base, Index)) ||
563  MBB.computeRegisterLiveness(TRI, X86::EFLAGS, I, 4) !=
565  Segment.getReg() != X86::NoRegister)
566  return;
567 
568  Register DestReg = Dest.getReg();
569  Register BaseReg = Base.getReg();
570  Register IndexReg = Index.getReg();
571 
572  if (MI.getOpcode() == X86::LEA64_32r) {
573  if (BaseReg != 0)
574  BaseReg = TRI->getSubReg(BaseReg, X86::sub_32bit);
575  if (IndexReg != 0)
576  IndexReg = TRI->getSubReg(IndexReg, X86::sub_32bit);
577  }
578 
579  bool IsScale1 = Scale.getImm() == 1;
580  bool IsInefficientBase = isInefficientLEAReg(BaseReg);
581  bool IsInefficientIndex = isInefficientLEAReg(IndexReg);
582 
583  // Skip these cases since it takes more than 2 instructions
584  // to replace the LEA instruction.
585  if (IsInefficientBase && DestReg == BaseReg && !IsScale1)
586  return;
587 
588  LLVM_DEBUG(dbgs() << "FixLEA: Candidate to replace:"; MI.dump(););
589  LLVM_DEBUG(dbgs() << "FixLEA: Replaced by: ";);
590 
591  MachineInstr *NewMI = nullptr;
592 
593  // First try to replace LEA with one or two (for the 3-op LEA case)
594  // add instructions:
595  // 1.lea (%base,%index,1), %base => add %index,%base
596  // 2.lea (%base,%index,1), %index => add %base,%index
597  if (IsScale1 && (DestReg == BaseReg || DestReg == IndexReg)) {
598  unsigned NewOpc = getADDrrFromLEA(MI.getOpcode());
599  if (DestReg != BaseReg)
600  std::swap(BaseReg, IndexReg);
601 
602  if (MI.getOpcode() == X86::LEA64_32r) {
603  // TODO: Do we need the super register implicit use?
604  NewMI = BuildMI(MBB, I, MI.getDebugLoc(), TII->get(NewOpc), DestReg)
605  .addReg(BaseReg)
606  .addReg(IndexReg)
607  .addReg(Base.getReg(), RegState::Implicit)
608  .addReg(Index.getReg(), RegState::Implicit);
609  } else {
610  NewMI = BuildMI(MBB, I, MI.getDebugLoc(), TII->get(NewOpc), DestReg)
611  .addReg(BaseReg)
612  .addReg(IndexReg);
613  }
614  } else if (!IsInefficientBase || (!IsInefficientIndex && IsScale1)) {
615  // If the base is inefficient try switching the index and base operands,
616  // otherwise just break the 3-Ops LEA inst into 2-Ops LEA + ADD instruction:
617  // lea offset(%base,%index,scale),%dst =>
618  // lea (%base,%index,scale); add offset,%dst
619  NewMI = BuildMI(MBB, MI, MI.getDebugLoc(), TII->get(LEAOpcode))
620  .add(Dest)
621  .add(IsInefficientBase ? Index : Base)
622  .add(Scale)
623  .add(IsInefficientBase ? Base : Index)
624  .addImm(0)
625  .add(Segment);
626  LLVM_DEBUG(NewMI->dump(););
627  }
628 
629  // If either replacement succeeded above, add the offset if needed, then
630  // replace the instruction.
631  if (NewMI) {
632  // Create ADD instruction for the Offset in case of 3-Ops LEA.
633  if (hasLEAOffset(Offset)) {
634  if (OptIncDec && Offset.isImm() &&
635  (Offset.getImm() == 1 || Offset.getImm() == -1)) {
636  unsigned NewOpc =
637  getINCDECFromLEA(MI.getOpcode(), Offset.getImm() == 1);
638  NewMI = BuildMI(MBB, I, MI.getDebugLoc(), TII->get(NewOpc), DestReg)
639  .addReg(DestReg);
640  LLVM_DEBUG(NewMI->dump(););
641  } else {
642  unsigned NewOpc = getADDriFromLEA(MI.getOpcode(), Offset);
643  NewMI = BuildMI(MBB, I, MI.getDebugLoc(), TII->get(NewOpc), DestReg)
644  .addReg(DestReg)
645  .add(Offset);
646  LLVM_DEBUG(NewMI->dump(););
647  }
648  }
649 
651  MBB.erase(I);
652  I = NewMI;
653  return;
654  }
655 
656  // Handle the rest of the cases with inefficient base register:
657  assert(DestReg != BaseReg && "DestReg == BaseReg should be handled already!");
658  assert(IsInefficientBase && "efficient base should be handled already!");
659 
660  // FIXME: Handle LEA64_32r.
661  if (LEAOpcode == X86::LEA64_32r)
662  return;
663 
664  // lea (%base,%index,1), %dst => mov %base,%dst; add %index,%dst
665  if (IsScale1 && !hasLEAOffset(Offset)) {
666  bool BIK = Base.isKill() && BaseReg != IndexReg;
667  TII->copyPhysReg(MBB, MI, MI.getDebugLoc(), DestReg, BaseReg, BIK);
668  LLVM_DEBUG(MI.getPrevNode()->dump(););
669 
670  unsigned NewOpc = getADDrrFromLEA(MI.getOpcode());
671  NewMI = BuildMI(MBB, MI, MI.getDebugLoc(), TII->get(NewOpc), DestReg)
672  .addReg(DestReg)
673  .add(Index);
674  LLVM_DEBUG(NewMI->dump(););
675 
677  MBB.erase(I);
678  I = NewMI;
679  return;
680  }
681 
682  // lea offset(%base,%index,scale), %dst =>
683  // lea offset( ,%index,scale), %dst; add %base,%dst
684  NewMI = BuildMI(MBB, MI, MI.getDebugLoc(), TII->get(LEAOpcode))
685  .add(Dest)
686  .addReg(0)
687  .add(Scale)
688  .add(Index)
689  .add(Offset)
690  .add(Segment);
691  LLVM_DEBUG(NewMI->dump(););
692 
693  unsigned NewOpc = getADDrrFromLEA(MI.getOpcode());
694  NewMI = BuildMI(MBB, MI, MI.getDebugLoc(), TII->get(NewOpc), DestReg)
695  .addReg(DestReg)
696  .add(Base);
697  LLVM_DEBUG(NewMI->dump(););
698 
700  MBB.erase(I);
701  I = NewMI;
702 }
const MachineInstrBuilder & add(const MachineOperand &MO) const
This class represents lattice values for constants.
Definition: AllocatorList.h:23
Not emitted register (e.g. carry, or temporary result).
bool hasOptSize() const
Optimize this function for size (-Os) or minimum size (-Oz).
Definition: Function.h:685
Describe properties that are true of each instruction in the target description file.
Definition: MCInstrDesc.h:196
unsigned Reg
static bool isInefficientLEAReg(unsigned Reg)
constexpr bool isInt< 8 >(int64_t x)
Definition: MathExtras.h:368
STATISTIC(NumFunctions, "Total number of functions")
unsigned const TargetRegisterInfo * TRI
bool isImm() const
isImm - Tests if this is a MO_Immediate operand.
Function & getFunction()
Return the LLVM function that this machine code represents.
MachineBasicBlock & MBB
LivenessQueryResult computeRegisterLiveness(const TargetRegisterInfo *TRI, MCRegister Reg, const_iterator Before, unsigned Neighborhood=10) const
Return whether (physical) register Reg has been defined and not killed as of just before Before.
static bool hasInefficientLEABaseReg(const MachineOperand &Base, const MachineOperand &Index)
Returns true if this LEA uses base an index registers, and the base register is known to be inefficie...
AnalysisUsage & addRequired()
void copyPhysReg(MachineBasicBlock &MBB, MachineBasicBlock::iterator I, const DebugLoc &DL, MCRegister DestReg, MCRegister SrcReg, bool KillSrc) const override
Emit instructions to copy a pair of physical registers.
instr_iterator erase(instr_iterator I)
Remove an instruction from the instruction list and delete it.
MachineFunctionPass - This class adapts the FunctionPass interface to allow convenient creation of pa...
Provide an instruction scheduling machine model to CodeGen passes.
const HexagonInstrInfo * TII
An analysis pass based on legacy pass manager to deliver ProfileSummaryInfo.
static bool getPreviousInstr(MachineBasicBlock::iterator &I, MachineBasicBlock &MBB)
getPreviousInstr - Given a reference to an instruction in a basic block, return a reference to the pr...
AddrSegmentReg - The operand # of the segment in the memory operand.
Definition: X86BaseInfo.h:38
===- LazyMachineBlockFrequencyInfo.h - Lazy Block Frequency -*- C++ -*–===//
FunctionPass * createX86FixupLEAs()
Return a pass that selectively replaces certain instructions (like add, sub, inc, dec,...
void dump() const
Definition: Pass.cpp:131
MachineInstrBuilder BuildMI(MachineFunction &MF, const DebugLoc &DL, const MCInstrDesc &MCID)
Builder interface. Specify how to create the initial instruction itself.
MachineInstrBundleIterator< MachineInstr > iterator
const TargetSubtargetInfo & getSubtarget() const
getSubtarget - Return the subtarget for which this machine code is being compiled.
void getAnalysisUsage(AnalysisUsage &AU) const override
getAnalysisUsage - Subclasses that override getAnalysisUsage must call this.
This is an alternative analysis pass to MachineBlockFrequencyInfo.
bool isPredecessor(const MachineBasicBlock *MBB) const
Return true if the specified MBB is a predecessor of this block.
Register is known to be fully dead.
Represent the analysis usage information of a pass.
FunctionPass class - This class is used to implement most global optimizations.
Definition: Pass.h:298
unsigned getOperandBias(const MCInstrDesc &Desc)
Compute whether all of the def operands are repeated in the uses and therefore should be skipped.
Definition: X86BaseInfo.h:1044
self_iterator getIterator()
Definition: ilist_node.h:81
#define llvm_unreachable(msg)
Marks that the current location is not supposed to be reachable.
static unsigned getADDriFromLEA(unsigned LEAOpcode, const MachineOperand &Offset)
#define INITIALIZE_PASS(passName, arg, name, cfg, analysis)
Definition: PassSupport.h:37
#define FIXUPLEA_DESC
uint64_t Offset
void substituteDebugValuesForInst(const MachineInstr &Old, MachineInstr &New, unsigned MaxOperand=UINT_MAX)
Create substitutions for any tracked values in Old, to point at New.
MachineOperand class - Representation of each machine instruction operand.
static unsigned getINCDECFromLEA(unsigned LEAOpcode, bool IsINC)
uint32_t Index
int64_t getImm() const
static unsigned getADDrrFromLEA(unsigned LEAOpcode)
static bool isLEA(unsigned Opcode)
raw_ostream & dbgs()
dbgs() - This returns a reference to a raw_ostream for debugging messages.
Definition: Debug.cpp:132
void swap(llvm::BitVector &LHS, llvm::BitVector &RHS)
Implement std::swap in terms of BitVector swap.
Definition: BitVector.h:944
bool shouldOptimizeForSize(const MachineFunction *MF, ProfileSummaryInfo *PSI, const MachineBlockFrequencyInfo *BFI, PGSOQueryType QueryType=PGSOQueryType::Other)
Returns true if machine function MF is suggested to be size-optimized based on the profile.
#define FIXUPLEA_NAME
MachineFunctionProperties & set(Property P)
Representation of each machine instruction.
Definition: MachineInstr.h:62
const MachineFunction * getParent() const
Return the MachineFunction containing this basic block.
const MachineInstrBuilder & addImm(int64_t Val) const
Add a new immediate operand.
static bool hasLEAOffset(const MachineOperand &Offset)
#define I(x, y, z)
Definition: MD5.cpp:59
bool isReg() const
isReg - Tests if this is a MO_Register operand.
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
IRTranslator LLVM IR MI
StringRef - Represent a constant reference to a string, i.e.
Definition: StringRef.h:57
Register getReg() const
getReg - Returns the register number.
#define LLVM_DEBUG(X)
Definition: Debug.h:122
const MachineInstrBuilder & addReg(Register RegNo, unsigned flags=0, unsigned SubReg=0) const
Add a new virtual register operand.
MachineBasicBlock MachineBasicBlock::iterator MBBI
Properties which a MachineFunction may have at a given point in time.
Wrapper class representing virtual and physical registers.
Definition: Register.h:19
int getMemoryOperandNo(uint64_t TSFlags)
The function returns the MCInst operand # for the first field of the memory operand.
Definition: X86BaseInfo.h:1084