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Diffstat (limited to 'gnu/llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp')
| -rw-r--r-- | gnu/llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp | 335 |
1 files changed, 0 insertions, 335 deletions
diff --git a/gnu/llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp b/gnu/llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp deleted file mode 100644 index b1c5670a6de..00000000000 --- a/gnu/llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp +++ /dev/null @@ -1,335 +0,0 @@ -//===-- lib/CodeGen/GlobalISel/GICombinerHelper.cpp -----------------------===// -// -// The LLVM Compiler Infrastructure -// -// This file is distributed under the University of Illinois Open Source -// License. See LICENSE.TXT for details. -// -//===----------------------------------------------------------------------===// -#include "llvm/CodeGen/GlobalISel/CombinerHelper.h" -#include "llvm/CodeGen/GlobalISel/Combiner.h" -#include "llvm/CodeGen/GlobalISel/GISelChangeObserver.h" -#include "llvm/CodeGen/GlobalISel/MachineIRBuilder.h" -#include "llvm/CodeGen/GlobalISel/Utils.h" -#include "llvm/CodeGen/MachineInstr.h" -#include "llvm/CodeGen/MachineRegisterInfo.h" -#include "llvm/CodeGen/TargetInstrInfo.h" - -#define DEBUG_TYPE "gi-combiner" - -using namespace llvm; - -CombinerHelper::CombinerHelper(GISelChangeObserver &Observer, - MachineIRBuilder &B) - : Builder(B), MRI(Builder.getMF().getRegInfo()), Observer(Observer) {} - -void CombinerHelper::replaceRegWith(MachineRegisterInfo &MRI, unsigned FromReg, - unsigned ToReg) const { - Observer.changingAllUsesOfReg(MRI, FromReg); - - if (MRI.constrainRegAttrs(ToReg, FromReg)) - MRI.replaceRegWith(FromReg, ToReg); - else - Builder.buildCopy(ToReg, FromReg); - - Observer.finishedChangingAllUsesOfReg(); -} - -void CombinerHelper::replaceRegOpWith(MachineRegisterInfo &MRI, - MachineOperand &FromRegOp, - unsigned ToReg) const { - assert(FromRegOp.getParent() && "Expected an operand in an MI"); - Observer.changingInstr(*FromRegOp.getParent()); - - FromRegOp.setReg(ToReg); - - Observer.changedInstr(*FromRegOp.getParent()); -} - -bool CombinerHelper::tryCombineCopy(MachineInstr &MI) { - if (MI.getOpcode() != TargetOpcode::COPY) - return false; - unsigned DstReg = MI.getOperand(0).getReg(); - unsigned SrcReg = MI.getOperand(1).getReg(); - LLT DstTy = MRI.getType(DstReg); - LLT SrcTy = MRI.getType(SrcReg); - // Simple Copy Propagation. - // a(sx) = COPY b(sx) -> Replace all uses of a with b. - if (DstTy.isValid() && SrcTy.isValid() && DstTy == SrcTy) { - MI.eraseFromParent(); - replaceRegWith(MRI, DstReg, SrcReg); - return true; - } - return false; -} - -namespace { -struct PreferredTuple { - LLT Ty; // The result type of the extend. - unsigned ExtendOpcode; // G_ANYEXT/G_SEXT/G_ZEXT - MachineInstr *MI; -}; - -/// Select a preference between two uses. CurrentUse is the current preference -/// while *ForCandidate is attributes of the candidate under consideration. -PreferredTuple ChoosePreferredUse(PreferredTuple &CurrentUse, - const LLT &TyForCandidate, - unsigned OpcodeForCandidate, - MachineInstr *MIForCandidate) { - if (!CurrentUse.Ty.isValid()) { - if (CurrentUse.ExtendOpcode == OpcodeForCandidate || - CurrentUse.ExtendOpcode == TargetOpcode::G_ANYEXT) - return {TyForCandidate, OpcodeForCandidate, MIForCandidate}; - return CurrentUse; - } - - // We permit the extend to hoist through basic blocks but this is only - // sensible if the target has extending loads. If you end up lowering back - // into a load and extend during the legalizer then the end result is - // hoisting the extend up to the load. - - // Prefer defined extensions to undefined extensions as these are more - // likely to reduce the number of instructions. - if (OpcodeForCandidate == TargetOpcode::G_ANYEXT && - CurrentUse.ExtendOpcode != TargetOpcode::G_ANYEXT) - return CurrentUse; - else if (CurrentUse.ExtendOpcode == TargetOpcode::G_ANYEXT && - OpcodeForCandidate != TargetOpcode::G_ANYEXT) - return {TyForCandidate, OpcodeForCandidate, MIForCandidate}; - - // Prefer sign extensions to zero extensions as sign-extensions tend to be - // more expensive. - if (CurrentUse.Ty == TyForCandidate) { - if (CurrentUse.ExtendOpcode == TargetOpcode::G_SEXT && - OpcodeForCandidate == TargetOpcode::G_ZEXT) - return CurrentUse; - else if (CurrentUse.ExtendOpcode == TargetOpcode::G_ZEXT && - OpcodeForCandidate == TargetOpcode::G_SEXT) - return {TyForCandidate, OpcodeForCandidate, MIForCandidate}; - } - - // This is potentially target specific. We've chosen the largest type - // because G_TRUNC is usually free. One potential catch with this is that - // some targets have a reduced number of larger registers than smaller - // registers and this choice potentially increases the live-range for the - // larger value. - if (TyForCandidate.getSizeInBits() > CurrentUse.Ty.getSizeInBits()) { - return {TyForCandidate, OpcodeForCandidate, MIForCandidate}; - } - return CurrentUse; -} - -/// Find a suitable place to insert some instructions and insert them. This -/// function accounts for special cases like inserting before a PHI node. -/// The current strategy for inserting before PHI's is to duplicate the -/// instructions for each predecessor. However, while that's ok for G_TRUNC -/// on most targets since it generally requires no code, other targets/cases may -/// want to try harder to find a dominating block. -static void InsertInsnsWithoutSideEffectsBeforeUse( - MachineIRBuilder &Builder, MachineInstr &DefMI, MachineOperand &UseMO, - std::function<void(MachineBasicBlock *, MachineBasicBlock::iterator)> - Inserter) { - MachineInstr &UseMI = *UseMO.getParent(); - - MachineBasicBlock *InsertBB = UseMI.getParent(); - - // If the use is a PHI then we want the predecessor block instead. - if (UseMI.isPHI()) { - MachineOperand *PredBB = std::next(&UseMO); - InsertBB = PredBB->getMBB(); - } - - // If the block is the same block as the def then we want to insert just after - // the def instead of at the start of the block. - if (InsertBB == DefMI.getParent()) { - MachineBasicBlock::iterator InsertPt = &DefMI; - Inserter(InsertBB, std::next(InsertPt)); - return; - } - - // Otherwise we want the start of the BB - Inserter(InsertBB, InsertBB->getFirstNonPHI()); -} -} // end anonymous namespace - -bool CombinerHelper::tryCombineExtendingLoads(MachineInstr &MI) { - struct InsertionPoint { - MachineOperand *UseMO; - MachineBasicBlock *InsertIntoBB; - MachineBasicBlock::iterator InsertBefore; - InsertionPoint(MachineOperand *UseMO, MachineBasicBlock *InsertIntoBB, - MachineBasicBlock::iterator InsertBefore) - : UseMO(UseMO), InsertIntoBB(InsertIntoBB), InsertBefore(InsertBefore) { - } - }; - - // We match the loads and follow the uses to the extend instead of matching - // the extends and following the def to the load. This is because the load - // must remain in the same position for correctness (unless we also add code - // to find a safe place to sink it) whereas the extend is freely movable. - // It also prevents us from duplicating the load for the volatile case or just - // for performance. - - if (MI.getOpcode() != TargetOpcode::G_LOAD && - MI.getOpcode() != TargetOpcode::G_SEXTLOAD && - MI.getOpcode() != TargetOpcode::G_ZEXTLOAD) - return false; - - auto &LoadValue = MI.getOperand(0); - assert(LoadValue.isReg() && "Result wasn't a register?"); - - LLT LoadValueTy = MRI.getType(LoadValue.getReg()); - if (!LoadValueTy.isScalar()) - return false; - - // Find the preferred type aside from the any-extends (unless it's the only - // one) and non-extending ops. We'll emit an extending load to that type and - // and emit a variant of (extend (trunc X)) for the others according to the - // relative type sizes. At the same time, pick an extend to use based on the - // extend involved in the chosen type. - unsigned PreferredOpcode = MI.getOpcode() == TargetOpcode::G_LOAD - ? TargetOpcode::G_ANYEXT - : MI.getOpcode() == TargetOpcode::G_SEXTLOAD - ? TargetOpcode::G_SEXT - : TargetOpcode::G_ZEXT; - PreferredTuple Preferred = {LLT(), PreferredOpcode, nullptr}; - for (auto &UseMI : MRI.use_instructions(LoadValue.getReg())) { - if (UseMI.getOpcode() == TargetOpcode::G_SEXT || - UseMI.getOpcode() == TargetOpcode::G_ZEXT || - UseMI.getOpcode() == TargetOpcode::G_ANYEXT) { - Preferred = ChoosePreferredUse(Preferred, - MRI.getType(UseMI.getOperand(0).getReg()), - UseMI.getOpcode(), &UseMI); - } - } - - // There were no extends - if (!Preferred.MI) - return false; - // It should be impossible to chose an extend without selecting a different - // type since by definition the result of an extend is larger. - assert(Preferred.Ty != LoadValueTy && "Extending to same type?"); - - LLVM_DEBUG(dbgs() << "Preferred use is: " << *Preferred.MI); - - // Rewrite the load to the chosen extending load. - unsigned ChosenDstReg = Preferred.MI->getOperand(0).getReg(); - Observer.changingInstr(MI); - MI.setDesc( - Builder.getTII().get(Preferred.ExtendOpcode == TargetOpcode::G_SEXT - ? TargetOpcode::G_SEXTLOAD - : Preferred.ExtendOpcode == TargetOpcode::G_ZEXT - ? TargetOpcode::G_ZEXTLOAD - : TargetOpcode::G_LOAD)); - - // Rewrite all the uses to fix up the types. - SmallVector<MachineInstr *, 1> ScheduleForErase; - SmallVector<InsertionPoint, 4> ScheduleForInsert; - for (auto &UseMO : MRI.use_operands(LoadValue.getReg())) { - MachineInstr *UseMI = UseMO.getParent(); - - // If the extend is compatible with the preferred extend then we should fix - // up the type and extend so that it uses the preferred use. - if (UseMI->getOpcode() == Preferred.ExtendOpcode || - UseMI->getOpcode() == TargetOpcode::G_ANYEXT) { - unsigned UseDstReg = UseMI->getOperand(0).getReg(); - MachineOperand &UseSrcMO = UseMI->getOperand(1); - const LLT &UseDstTy = MRI.getType(UseDstReg); - if (UseDstReg != ChosenDstReg) { - if (Preferred.Ty == UseDstTy) { - // If the use has the same type as the preferred use, then merge - // the vregs and erase the extend. For example: - // %1:_(s8) = G_LOAD ... - // %2:_(s32) = G_SEXT %1(s8) - // %3:_(s32) = G_ANYEXT %1(s8) - // ... = ... %3(s32) - // rewrites to: - // %2:_(s32) = G_SEXTLOAD ... - // ... = ... %2(s32) - replaceRegWith(MRI, UseDstReg, ChosenDstReg); - ScheduleForErase.push_back(UseMO.getParent()); - } else if (Preferred.Ty.getSizeInBits() < UseDstTy.getSizeInBits()) { - // If the preferred size is smaller, then keep the extend but extend - // from the result of the extending load. For example: - // %1:_(s8) = G_LOAD ... - // %2:_(s32) = G_SEXT %1(s8) - // %3:_(s64) = G_ANYEXT %1(s8) - // ... = ... %3(s64) - /// rewrites to: - // %2:_(s32) = G_SEXTLOAD ... - // %3:_(s64) = G_ANYEXT %2:_(s32) - // ... = ... %3(s64) - replaceRegOpWith(MRI, UseSrcMO, ChosenDstReg); - } else { - // If the preferred size is large, then insert a truncate. For - // example: - // %1:_(s8) = G_LOAD ... - // %2:_(s64) = G_SEXT %1(s8) - // %3:_(s32) = G_ZEXT %1(s8) - // ... = ... %3(s32) - /// rewrites to: - // %2:_(s64) = G_SEXTLOAD ... - // %4:_(s8) = G_TRUNC %2:_(s32) - // %3:_(s64) = G_ZEXT %2:_(s8) - // ... = ... %3(s64) - InsertInsnsWithoutSideEffectsBeforeUse( - Builder, MI, UseMO, - [&](MachineBasicBlock *InsertIntoBB, - MachineBasicBlock::iterator InsertBefore) { - ScheduleForInsert.emplace_back(&UseMO, InsertIntoBB, InsertBefore); - }); - } - continue; - } - // The use is (one of) the uses of the preferred use we chose earlier. - // We're going to update the load to def this value later so just erase - // the old extend. - ScheduleForErase.push_back(UseMO.getParent()); - continue; - } - - // The use isn't an extend. Truncate back to the type we originally loaded. - // This is free on many targets. - InsertInsnsWithoutSideEffectsBeforeUse( - Builder, MI, UseMO, - [&](MachineBasicBlock *InsertIntoBB, - MachineBasicBlock::iterator InsertBefore) { - ScheduleForInsert.emplace_back(&UseMO, InsertIntoBB, InsertBefore); - }); - } - - DenseMap<MachineBasicBlock *, MachineInstr *> EmittedInsns; - for (auto &InsertionInfo : ScheduleForInsert) { - MachineOperand *UseMO = InsertionInfo.UseMO; - MachineBasicBlock *InsertIntoBB = InsertionInfo.InsertIntoBB; - MachineBasicBlock::iterator InsertBefore = InsertionInfo.InsertBefore; - - MachineInstr *PreviouslyEmitted = EmittedInsns.lookup(InsertIntoBB); - if (PreviouslyEmitted) { - Observer.changingInstr(*UseMO->getParent()); - UseMO->setReg(PreviouslyEmitted->getOperand(0).getReg()); - Observer.changedInstr(*UseMO->getParent()); - continue; - } - - Builder.setInsertPt(*InsertIntoBB, InsertBefore); - unsigned NewDstReg = MRI.cloneVirtualRegister(MI.getOperand(0).getReg()); - MachineInstr *NewMI = Builder.buildTrunc(NewDstReg, ChosenDstReg); - EmittedInsns[InsertIntoBB] = NewMI; - replaceRegOpWith(MRI, *UseMO, NewDstReg); - } - for (auto &EraseMI : ScheduleForErase) { - Observer.erasingInstr(*EraseMI); - EraseMI->eraseFromParent(); - } - MI.getOperand(0).setReg(ChosenDstReg); - Observer.changedInstr(MI); - - return true; -} - -bool CombinerHelper::tryCombine(MachineInstr &MI) { - if (tryCombineCopy(MI)) - return true; - return tryCombineExtendingLoads(MI); -} |