//===-- SIFoldOperands.cpp - Fold operands --- ----------------------------===// // // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. // See https://llvm.org/LICENSE.txt for license information. // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception // /// \file //===----------------------------------------------------------------------===// // #include "AMDGPU.h" #include "GCNSubtarget.h" #include "MCTargetDesc/AMDGPUMCTargetDesc.h" #include "SIMachineFunctionInfo.h" #include "llvm/ADT/DepthFirstIterator.h" #include "llvm/CodeGen/MachineFunctionPass.h" #define DEBUG_TYPE "si-fold-operands" using namespace llvm; namespace { struct FoldCandidate { MachineInstr *UseMI; union { MachineOperand *OpToFold; uint64_t ImmToFold; int FrameIndexToFold; }; int ShrinkOpcode; unsigned UseOpNo; MachineOperand::MachineOperandType Kind; bool Commuted; FoldCandidate(MachineInstr *MI, unsigned OpNo, MachineOperand *FoldOp, bool Commuted_ = false, int ShrinkOp = -1) : UseMI(MI), OpToFold(nullptr), ShrinkOpcode(ShrinkOp), UseOpNo(OpNo), Kind(FoldOp->getType()), Commuted(Commuted_) { if (FoldOp->isImm()) { ImmToFold = FoldOp->getImm(); } else if (FoldOp->isFI()) { FrameIndexToFold = FoldOp->getIndex(); } else { assert(FoldOp->isReg() || FoldOp->isGlobal()); OpToFold = FoldOp; } } bool isFI() const { return Kind == MachineOperand::MO_FrameIndex; } bool isImm() const { return Kind == MachineOperand::MO_Immediate; } bool isReg() const { return Kind == MachineOperand::MO_Register; } bool isGlobal() const { return Kind == MachineOperand::MO_GlobalAddress; } bool isCommuted() const { return Commuted; } bool needsShrink() const { return ShrinkOpcode != -1; } int getShrinkOpcode() const { return ShrinkOpcode; } }; class SIFoldOperands : public MachineFunctionPass { public: static char ID; MachineRegisterInfo *MRI; const SIInstrInfo *TII; const SIRegisterInfo *TRI; const GCNSubtarget *ST; const SIMachineFunctionInfo *MFI; void foldOperand(MachineOperand &OpToFold, MachineInstr *UseMI, int UseOpIdx, SmallVectorImpl &FoldList, SmallVectorImpl &CopiesToReplace) const; void foldInstOperand(MachineInstr &MI, MachineOperand &OpToFold) const; const MachineOperand *isClamp(const MachineInstr &MI) const; bool tryFoldClamp(MachineInstr &MI); std::pair isOMod(const MachineInstr &MI) const; bool tryFoldOMod(MachineInstr &MI); public: SIFoldOperands() : MachineFunctionPass(ID) { initializeSIFoldOperandsPass(*PassRegistry::getPassRegistry()); } bool runOnMachineFunction(MachineFunction &MF) override; StringRef getPassName() const override { return "SI Fold Operands"; } void getAnalysisUsage(AnalysisUsage &AU) const override { AU.setPreservesCFG(); MachineFunctionPass::getAnalysisUsage(AU); } }; } // End anonymous namespace. INITIALIZE_PASS(SIFoldOperands, DEBUG_TYPE, "SI Fold Operands", false, false) char SIFoldOperands::ID = 0; char &llvm::SIFoldOperandsID = SIFoldOperands::ID; // Map multiply-accumulate opcode to corresponding multiply-add opcode if any. static unsigned macToMad(unsigned Opc) { switch (Opc) { case AMDGPU::V_MAC_F32_e64: return AMDGPU::V_MAD_F32_e64; case AMDGPU::V_MAC_F16_e64: return AMDGPU::V_MAD_F16_e64; case AMDGPU::V_FMAC_F32_e64: return AMDGPU::V_FMA_F32_e64; case AMDGPU::V_FMAC_F16_e64: return AMDGPU::V_FMA_F16_gfx9_e64; case AMDGPU::V_FMAC_LEGACY_F32_e64: return AMDGPU::V_FMA_LEGACY_F32_e64; } return AMDGPU::INSTRUCTION_LIST_END; } // Wrapper around isInlineConstant that understands special cases when // instruction types are replaced during operand folding. static bool isInlineConstantIfFolded(const SIInstrInfo *TII, const MachineInstr &UseMI, unsigned OpNo, const MachineOperand &OpToFold) { if (TII->isInlineConstant(UseMI, OpNo, OpToFold)) return true; unsigned Opc = UseMI.getOpcode(); unsigned NewOpc = macToMad(Opc); if (NewOpc != AMDGPU::INSTRUCTION_LIST_END) { // Special case for mac. Since this is replaced with mad when folded into // src2, we need to check the legality for the final instruction. int Src2Idx = AMDGPU::getNamedOperandIdx(Opc, AMDGPU::OpName::src2); if (static_cast(OpNo) == Src2Idx) { const MCInstrDesc &MadDesc = TII->get(NewOpc); return TII->isInlineConstant(OpToFold, MadDesc.OpInfo[OpNo].OperandType); } } return false; } // TODO: Add heuristic that the frame index might not fit in the addressing mode // immediate offset to avoid materializing in loops. static bool frameIndexMayFold(const SIInstrInfo *TII, const MachineInstr &UseMI, int OpNo, const MachineOperand &OpToFold) { if (!OpToFold.isFI()) return false; if (TII->isMUBUF(UseMI)) return OpNo == AMDGPU::getNamedOperandIdx(UseMI.getOpcode(), AMDGPU::OpName::vaddr); if (!TII->isFLATScratch(UseMI)) return false; int SIdx = AMDGPU::getNamedOperandIdx(UseMI.getOpcode(), AMDGPU::OpName::saddr); if (OpNo == SIdx) return true; int VIdx = AMDGPU::getNamedOperandIdx(UseMI.getOpcode(), AMDGPU::OpName::vaddr); return OpNo == VIdx && SIdx == -1; } FunctionPass *llvm::createSIFoldOperandsPass() { return new SIFoldOperands(); } static bool updateOperand(FoldCandidate &Fold, const SIInstrInfo &TII, const TargetRegisterInfo &TRI, const GCNSubtarget &ST) { MachineInstr *MI = Fold.UseMI; MachineOperand &Old = MI->getOperand(Fold.UseOpNo); assert(Old.isReg()); if (Fold.isImm()) { if (MI->getDesc().TSFlags & SIInstrFlags::IsPacked && !(MI->getDesc().TSFlags & SIInstrFlags::IsMAI) && AMDGPU::isFoldableLiteralV216(Fold.ImmToFold, ST.hasInv2PiInlineImm())) { // Set op_sel/op_sel_hi on this operand or bail out if op_sel is // already set. unsigned Opcode = MI->getOpcode(); int OpNo = MI->getOperandNo(&Old); int ModIdx = -1; if (OpNo == AMDGPU::getNamedOperandIdx(Opcode, AMDGPU::OpName::src0)) ModIdx = AMDGPU::OpName::src0_modifiers; else if (OpNo == AMDGPU::getNamedOperandIdx(Opcode, AMDGPU::OpName::src1)) ModIdx = AMDGPU::OpName::src1_modifiers; else if (OpNo == AMDGPU::getNamedOperandIdx(Opcode, AMDGPU::OpName::src2)) ModIdx = AMDGPU::OpName::src2_modifiers; assert(ModIdx != -1); ModIdx = AMDGPU::getNamedOperandIdx(Opcode, ModIdx); MachineOperand &Mod = MI->getOperand(ModIdx); unsigned Val = Mod.getImm(); if (!(Val & SISrcMods::OP_SEL_0) && (Val & SISrcMods::OP_SEL_1)) { // Only apply the following transformation if that operand requries // a packed immediate. switch (TII.get(Opcode).OpInfo[OpNo].OperandType) { case AMDGPU::OPERAND_REG_IMM_V2FP16: case AMDGPU::OPERAND_REG_IMM_V2INT16: case AMDGPU::OPERAND_REG_INLINE_C_V2FP16: case AMDGPU::OPERAND_REG_INLINE_C_V2INT16: // If upper part is all zero we do not need op_sel_hi. if (!isUInt<16>(Fold.ImmToFold)) { if (!(Fold.ImmToFold & 0xffff)) { Mod.setImm(Mod.getImm() | SISrcMods::OP_SEL_0); Mod.setImm(Mod.getImm() & ~SISrcMods::OP_SEL_1); Old.ChangeToImmediate((Fold.ImmToFold >> 16) & 0xffff); return true; } Mod.setImm(Mod.getImm() & ~SISrcMods::OP_SEL_1); Old.ChangeToImmediate(Fold.ImmToFold & 0xffff); return true; } break; default: break; } } } } if ((Fold.isImm() || Fold.isFI() || Fold.isGlobal()) && Fold.needsShrink()) { MachineBasicBlock *MBB = MI->getParent(); auto Liveness = MBB->computeRegisterLiveness(&TRI, AMDGPU::VCC, MI, 16); if (Liveness != MachineBasicBlock::LQR_Dead) { LLVM_DEBUG(dbgs() << "Not shrinking " << MI << " due to vcc liveness\n"); return false; } MachineRegisterInfo &MRI = MBB->getParent()->getRegInfo(); int Op32 = Fold.getShrinkOpcode(); MachineOperand &Dst0 = MI->getOperand(0); MachineOperand &Dst1 = MI->getOperand(1); assert(Dst0.isDef() && Dst1.isDef()); bool HaveNonDbgCarryUse = !MRI.use_nodbg_empty(Dst1.getReg()); const TargetRegisterClass *Dst0RC = MRI.getRegClass(Dst0.getReg()); Register NewReg0 = MRI.createVirtualRegister(Dst0RC); MachineInstr *Inst32 = TII.buildShrunkInst(*MI, Op32); if (HaveNonDbgCarryUse) { BuildMI(*MBB, MI, MI->getDebugLoc(), TII.get(AMDGPU::COPY), Dst1.getReg()) .addReg(AMDGPU::VCC, RegState::Kill); } // Keep the old instruction around to avoid breaking iterators, but // replace it with a dummy instruction to remove uses. // // FIXME: We should not invert how this pass looks at operands to avoid // this. Should track set of foldable movs instead of looking for uses // when looking at a use. Dst0.setReg(NewReg0); for (unsigned I = MI->getNumOperands() - 1; I > 0; --I) MI->RemoveOperand(I); MI->setDesc(TII.get(AMDGPU::IMPLICIT_DEF)); if (Fold.isCommuted()) TII.commuteInstruction(*Inst32, false); return true; } assert(!Fold.needsShrink() && "not handled"); if (Fold.isImm()) { Old.ChangeToImmediate(Fold.ImmToFold); return true; } if (Fold.isGlobal()) { Old.ChangeToGA(Fold.OpToFold->getGlobal(), Fold.OpToFold->getOffset(), Fold.OpToFold->getTargetFlags()); return true; } if (Fold.isFI()) { Old.ChangeToFrameIndex(Fold.FrameIndexToFold); return true; } MachineOperand *New = Fold.OpToFold; Old.substVirtReg(New->getReg(), New->getSubReg(), TRI); Old.setIsUndef(New->isUndef()); return true; } static bool isUseMIInFoldList(ArrayRef FoldList, const MachineInstr *MI) { for (auto Candidate : FoldList) { if (Candidate.UseMI == MI) return true; } return false; } static void appendFoldCandidate(SmallVectorImpl &FoldList, MachineInstr *MI, unsigned OpNo, MachineOperand *FoldOp, bool Commuted = false, int ShrinkOp = -1) { // Skip additional folding on the same operand. for (FoldCandidate &Fold : FoldList) if (Fold.UseMI == MI && Fold.UseOpNo == OpNo) return; LLVM_DEBUG(dbgs() << "Append " << (Commuted ? "commuted" : "normal") << " operand " << OpNo << "\n " << *MI << '\n'); FoldList.push_back(FoldCandidate(MI, OpNo, FoldOp, Commuted, ShrinkOp)); } static bool tryAddToFoldList(SmallVectorImpl &FoldList, MachineInstr *MI, unsigned OpNo, MachineOperand *OpToFold, const SIInstrInfo *TII) { if (!TII->isOperandLegal(*MI, OpNo, OpToFold)) { // Special case for v_mac_{f16, f32}_e64 if we are trying to fold into src2 unsigned Opc = MI->getOpcode(); unsigned NewOpc = macToMad(Opc); if (NewOpc != AMDGPU::INSTRUCTION_LIST_END) { // Check if changing this to a v_mad_{f16, f32} instruction will allow us // to fold the operand. MI->setDesc(TII->get(NewOpc)); bool FoldAsMAD = tryAddToFoldList(FoldList, MI, OpNo, OpToFold, TII); if (FoldAsMAD) { MI->untieRegOperand(OpNo); return true; } MI->setDesc(TII->get(Opc)); } // Special case for s_setreg_b32 if (OpToFold->isImm()) { unsigned ImmOpc = 0; if (Opc == AMDGPU::S_SETREG_B32) ImmOpc = AMDGPU::S_SETREG_IMM32_B32; else if (Opc == AMDGPU::S_SETREG_B32_mode) ImmOpc = AMDGPU::S_SETREG_IMM32_B32_mode; if (ImmOpc) { MI->setDesc(TII->get(ImmOpc)); appendFoldCandidate(FoldList, MI, OpNo, OpToFold); return true; } } // If we are already folding into another operand of MI, then // we can't commute the instruction, otherwise we risk making the // other fold illegal. if (isUseMIInFoldList(FoldList, MI)) return false; unsigned CommuteOpNo = OpNo; // Operand is not legal, so try to commute the instruction to // see if this makes it possible to fold. unsigned CommuteIdx0 = TargetInstrInfo::CommuteAnyOperandIndex; unsigned CommuteIdx1 = TargetInstrInfo::CommuteAnyOperandIndex; bool CanCommute = TII->findCommutedOpIndices(*MI, CommuteIdx0, CommuteIdx1); if (CanCommute) { if (CommuteIdx0 == OpNo) CommuteOpNo = CommuteIdx1; else if (CommuteIdx1 == OpNo) CommuteOpNo = CommuteIdx0; } // One of operands might be an Imm operand, and OpNo may refer to it after // the call of commuteInstruction() below. Such situations are avoided // here explicitly as OpNo must be a register operand to be a candidate // for memory folding. if (CanCommute && (!MI->getOperand(CommuteIdx0).isReg() || !MI->getOperand(CommuteIdx1).isReg())) return false; if (!CanCommute || !TII->commuteInstruction(*MI, false, CommuteIdx0, CommuteIdx1)) return false; if (!TII->isOperandLegal(*MI, CommuteOpNo, OpToFold)) { if ((Opc == AMDGPU::V_ADD_CO_U32_e64 || Opc == AMDGPU::V_SUB_CO_U32_e64 || Opc == AMDGPU::V_SUBREV_CO_U32_e64) && // FIXME (OpToFold->isImm() || OpToFold->isFI() || OpToFold->isGlobal())) { MachineRegisterInfo &MRI = MI->getParent()->getParent()->getRegInfo(); // Verify the other operand is a VGPR, otherwise we would violate the // constant bus restriction. unsigned OtherIdx = CommuteOpNo == CommuteIdx0 ? CommuteIdx1 : CommuteIdx0; MachineOperand &OtherOp = MI->getOperand(OtherIdx); if (!OtherOp.isReg() || !TII->getRegisterInfo().isVGPR(MRI, OtherOp.getReg())) return false; assert(MI->getOperand(1).isDef()); // Make sure to get the 32-bit version of the commuted opcode. unsigned MaybeCommutedOpc = MI->getOpcode(); int Op32 = AMDGPU::getVOPe32(MaybeCommutedOpc); appendFoldCandidate(FoldList, MI, CommuteOpNo, OpToFold, true, Op32); return true; } TII->commuteInstruction(*MI, false, CommuteIdx0, CommuteIdx1); return false; } appendFoldCandidate(FoldList, MI, CommuteOpNo, OpToFold, true); return true; } // Check the case where we might introduce a second constant operand to a // scalar instruction if (TII->isSALU(MI->getOpcode())) { const MCInstrDesc &InstDesc = MI->getDesc(); const MCOperandInfo &OpInfo = InstDesc.OpInfo[OpNo]; const SIRegisterInfo &SRI = TII->getRegisterInfo(); // Fine if the operand can be encoded as an inline constant if (OpToFold->isImm()) { if (!SRI.opCanUseInlineConstant(OpInfo.OperandType) || !TII->isInlineConstant(*OpToFold, OpInfo)) { // Otherwise check for another constant for (unsigned i = 0, e = InstDesc.getNumOperands(); i != e; ++i) { auto &Op = MI->getOperand(i); if (OpNo != i && TII->isLiteralConstantLike(Op, OpInfo)) { return false; } } } } } appendFoldCandidate(FoldList, MI, OpNo, OpToFold); return true; } // If the use operand doesn't care about the value, this may be an operand only // used for register indexing, in which case it is unsafe to fold. static bool isUseSafeToFold(const SIInstrInfo *TII, const MachineInstr &MI, const MachineOperand &UseMO) { if (UseMO.isUndef() || TII->isSDWA(MI)) return false; switch (MI.getOpcode()) { case AMDGPU::V_MOV_B32_e32: case AMDGPU::V_MOV_B32_e64: case AMDGPU::V_MOV_B64_PSEUDO: // Do not fold into an indirect mov. return !MI.hasRegisterImplicitUseOperand(AMDGPU::M0); } return true; //return !MI.hasRegisterImplicitUseOperand(UseMO.getReg()); } // Find a def of the UseReg, check if it is a reg_seqence and find initializers // for each subreg, tracking it to foldable inline immediate if possible. // Returns true on success. static bool getRegSeqInit( SmallVectorImpl> &Defs, Register UseReg, uint8_t OpTy, const SIInstrInfo *TII, const MachineRegisterInfo &MRI) { MachineInstr *Def = MRI.getUniqueVRegDef(UseReg); if (!Def || !Def->isRegSequence()) return false; for (unsigned I = 1, E = Def->getNumExplicitOperands(); I < E; I += 2) { MachineOperand *Sub = &Def->getOperand(I); assert (Sub->isReg()); for (MachineInstr *SubDef = MRI.getUniqueVRegDef(Sub->getReg()); SubDef && Sub->isReg() && !Sub->getSubReg() && TII->isFoldableCopy(*SubDef); SubDef = MRI.getUniqueVRegDef(Sub->getReg())) { MachineOperand *Op = &SubDef->getOperand(1); if (Op->isImm()) { if (TII->isInlineConstant(*Op, OpTy)) Sub = Op; break; } if (!Op->isReg()) break; Sub = Op; } Defs.push_back(std::make_pair(Sub, Def->getOperand(I + 1).getImm())); } return true; } static bool tryToFoldACImm(const SIInstrInfo *TII, const MachineOperand &OpToFold, MachineInstr *UseMI, unsigned UseOpIdx, SmallVectorImpl &FoldList) { const MCInstrDesc &Desc = UseMI->getDesc(); const MCOperandInfo *OpInfo = Desc.OpInfo; if (!OpInfo || UseOpIdx >= Desc.getNumOperands()) return false; uint8_t OpTy = OpInfo[UseOpIdx].OperandType; if (OpTy < AMDGPU::OPERAND_REG_INLINE_AC_FIRST || OpTy > AMDGPU::OPERAND_REG_INLINE_AC_LAST) return false; if (OpToFold.isImm() && TII->isInlineConstant(OpToFold, OpTy) && TII->isOperandLegal(*UseMI, UseOpIdx, &OpToFold)) { UseMI->getOperand(UseOpIdx).ChangeToImmediate(OpToFold.getImm()); return true; } if (!OpToFold.isReg()) return false; Register UseReg = OpToFold.getReg(); if (!UseReg.isVirtual()) return false; if (llvm::any_of(FoldList, [UseMI](const FoldCandidate &FC) { return FC.UseMI == UseMI; })) return false; MachineRegisterInfo &MRI = UseMI->getParent()->getParent()->getRegInfo(); SmallVector, 32> Defs; if (!getRegSeqInit(Defs, UseReg, OpTy, TII, MRI)) return false; int32_t Imm; for (unsigned I = 0, E = Defs.size(); I != E; ++I) { const MachineOperand *Op = Defs[I].first; if (!Op->isImm()) return false; auto SubImm = Op->getImm(); if (!I) { Imm = SubImm; if (!TII->isInlineConstant(*Op, OpTy) || !TII->isOperandLegal(*UseMI, UseOpIdx, Op)) return false; continue; } if (Imm != SubImm) return false; // Can only fold splat constants } appendFoldCandidate(FoldList, UseMI, UseOpIdx, Defs[0].first); return true; } void SIFoldOperands::foldOperand( MachineOperand &OpToFold, MachineInstr *UseMI, int UseOpIdx, SmallVectorImpl &FoldList, SmallVectorImpl &CopiesToReplace) const { const MachineOperand &UseOp = UseMI->getOperand(UseOpIdx); if (!isUseSafeToFold(TII, *UseMI, UseOp)) return; // FIXME: Fold operands with subregs. if (UseOp.isReg() && OpToFold.isReg()) { if (UseOp.isImplicit() || UseOp.getSubReg() != AMDGPU::NoSubRegister) return; } // Special case for REG_SEQUENCE: We can't fold literals into // REG_SEQUENCE instructions, so we have to fold them into the // uses of REG_SEQUENCE. if (UseMI->isRegSequence()) { Register RegSeqDstReg = UseMI->getOperand(0).getReg(); unsigned RegSeqDstSubReg = UseMI->getOperand(UseOpIdx + 1).getImm(); MachineRegisterInfo::use_nodbg_iterator Next; for (MachineRegisterInfo::use_nodbg_iterator RSUse = MRI->use_nodbg_begin(RegSeqDstReg), RSE = MRI->use_nodbg_end(); RSUse != RSE; RSUse = Next) { Next = std::next(RSUse); MachineInstr *RSUseMI = RSUse->getParent(); if (tryToFoldACImm(TII, UseMI->getOperand(0), RSUseMI, RSUse.getOperandNo(), FoldList)) continue; if (RSUse->getSubReg() != RegSeqDstSubReg) continue; foldOperand(OpToFold, RSUseMI, RSUse.getOperandNo(), FoldList, CopiesToReplace); } return; } if (tryToFoldACImm(TII, OpToFold, UseMI, UseOpIdx, FoldList)) return; if (frameIndexMayFold(TII, *UseMI, UseOpIdx, OpToFold)) { // Sanity check that this is a stack access. // FIXME: Should probably use stack pseudos before frame lowering. if (TII->isMUBUF(*UseMI)) { if (TII->getNamedOperand(*UseMI, AMDGPU::OpName::srsrc)->getReg() != MFI->getScratchRSrcReg()) return; // Ensure this is either relative to the current frame or the current // wave. MachineOperand &SOff = *TII->getNamedOperand(*UseMI, AMDGPU::OpName::soffset); if (!SOff.isImm() || SOff.getImm() != 0) return; } // A frame index will resolve to a positive constant, so it should always be // safe to fold the addressing mode, even pre-GFX9. UseMI->getOperand(UseOpIdx).ChangeToFrameIndex(OpToFold.getIndex()); if (TII->isFLATScratch(*UseMI) && AMDGPU::getNamedOperandIdx(UseMI->getOpcode(), AMDGPU::OpName::vaddr) != -1) { unsigned NewOpc = AMDGPU::getFlatScratchInstSSfromSV(UseMI->getOpcode()); UseMI->setDesc(TII->get(NewOpc)); } return; } bool FoldingImmLike = OpToFold.isImm() || OpToFold.isFI() || OpToFold.isGlobal(); if (FoldingImmLike && UseMI->isCopy()) { Register DestReg = UseMI->getOperand(0).getReg(); Register SrcReg = UseMI->getOperand(1).getReg(); assert(SrcReg.isVirtual()); const TargetRegisterClass *SrcRC = MRI->getRegClass(SrcReg); // Don't fold into a copy to a physical register with the same class. Doing // so would interfere with the register coalescer's logic which would avoid // redundant initalizations. if (DestReg.isPhysical() && SrcRC->contains(DestReg)) return; const TargetRegisterClass *DestRC = TRI->getRegClassForReg(*MRI, DestReg); if (!DestReg.isPhysical()) { if (TRI->isSGPRClass(SrcRC) && TRI->hasVectorRegisters(DestRC)) { MachineRegisterInfo::use_nodbg_iterator NextUse; SmallVector CopyUses; for (MachineRegisterInfo::use_nodbg_iterator Use = MRI->use_nodbg_begin(DestReg), E = MRI->use_nodbg_end(); Use != E; Use = NextUse) { NextUse = std::next(Use); // There's no point trying to fold into an implicit operand. if (Use->isImplicit()) continue; FoldCandidate FC = FoldCandidate(Use->getParent(), Use.getOperandNo(), &UseMI->getOperand(1)); CopyUses.push_back(FC); } for (auto &F : CopyUses) { foldOperand(*F.OpToFold, F.UseMI, F.UseOpNo, FoldList, CopiesToReplace); } } if (DestRC == &AMDGPU::AGPR_32RegClass && TII->isInlineConstant(OpToFold, AMDGPU::OPERAND_REG_INLINE_C_INT32)) { UseMI->setDesc(TII->get(AMDGPU::V_ACCVGPR_WRITE_B32_e64)); UseMI->getOperand(1).ChangeToImmediate(OpToFold.getImm()); CopiesToReplace.push_back(UseMI); return; } } // In order to fold immediates into copies, we need to change the // copy to a MOV. unsigned MovOp = TII->getMovOpcode(DestRC); if (MovOp == AMDGPU::COPY) return; UseMI->setDesc(TII->get(MovOp)); MachineInstr::mop_iterator ImpOpI = UseMI->implicit_operands().begin(); MachineInstr::mop_iterator ImpOpE = UseMI->implicit_operands().end(); while (ImpOpI != ImpOpE) { MachineInstr::mop_iterator Tmp = ImpOpI; ImpOpI++; UseMI->RemoveOperand(UseMI->getOperandNo(Tmp)); } CopiesToReplace.push_back(UseMI); } else { if (UseMI->isCopy() && OpToFold.isReg() && UseMI->getOperand(0).getReg().isVirtual() && !UseMI->getOperand(1).getSubReg()) { LLVM_DEBUG(dbgs() << "Folding " << OpToFold << "\n into " << *UseMI << '\n'); unsigned Size = TII->getOpSize(*UseMI, 1); Register UseReg = OpToFold.getReg(); UseMI->getOperand(1).setReg(UseReg); UseMI->getOperand(1).setSubReg(OpToFold.getSubReg()); UseMI->getOperand(1).setIsKill(false); CopiesToReplace.push_back(UseMI); OpToFold.setIsKill(false); // That is very tricky to store a value into an AGPR. v_accvgpr_write_b32 // can only accept VGPR or inline immediate. Recreate a reg_sequence with // its initializers right here, so we will rematerialize immediates and // avoid copies via different reg classes. SmallVector, 32> Defs; if (Size > 4 && TRI->isAGPR(*MRI, UseMI->getOperand(0).getReg()) && getRegSeqInit(Defs, UseReg, AMDGPU::OPERAND_REG_INLINE_C_INT32, TII, *MRI)) { const DebugLoc &DL = UseMI->getDebugLoc(); MachineBasicBlock &MBB = *UseMI->getParent(); UseMI->setDesc(TII->get(AMDGPU::REG_SEQUENCE)); for (unsigned I = UseMI->getNumOperands() - 1; I > 0; --I) UseMI->RemoveOperand(I); MachineInstrBuilder B(*MBB.getParent(), UseMI); DenseMap VGPRCopies; SmallSetVector SeenAGPRs; for (unsigned I = 0; I < Size / 4; ++I) { MachineOperand *Def = Defs[I].first; TargetInstrInfo::RegSubRegPair CopyToVGPR; if (Def->isImm() && TII->isInlineConstant(*Def, AMDGPU::OPERAND_REG_INLINE_C_INT32)) { int64_t Imm = Def->getImm(); auto Tmp = MRI->createVirtualRegister(&AMDGPU::AGPR_32RegClass); BuildMI(MBB, UseMI, DL, TII->get(AMDGPU::V_ACCVGPR_WRITE_B32_e64), Tmp).addImm(Imm); B.addReg(Tmp); } else if (Def->isReg() && TRI->isAGPR(*MRI, Def->getReg())) { auto Src = getRegSubRegPair(*Def); Def->setIsKill(false); if (!SeenAGPRs.insert(Src)) { // We cannot build a reg_sequence out of the same registers, they // must be copied. Better do it here before copyPhysReg() created // several reads to do the AGPR->VGPR->AGPR copy. CopyToVGPR = Src; } else { B.addReg(Src.Reg, Def->isUndef() ? RegState::Undef : 0, Src.SubReg); } } else { assert(Def->isReg()); Def->setIsKill(false); auto Src = getRegSubRegPair(*Def); // Direct copy from SGPR to AGPR is not possible. To avoid creation // of exploded copies SGPR->VGPR->AGPR in the copyPhysReg() later, // create a copy here and track if we already have such a copy. if (TRI->isSGPRReg(*MRI, Src.Reg)) { CopyToVGPR = Src; } else { auto Tmp = MRI->createVirtualRegister(&AMDGPU::AGPR_32RegClass); BuildMI(MBB, UseMI, DL, TII->get(AMDGPU::COPY), Tmp).add(*Def); B.addReg(Tmp); } } if (CopyToVGPR.Reg) { Register Vgpr; if (VGPRCopies.count(CopyToVGPR)) { Vgpr = VGPRCopies[CopyToVGPR]; } else { Vgpr = MRI->createVirtualRegister(&AMDGPU::VGPR_32RegClass); BuildMI(MBB, UseMI, DL, TII->get(AMDGPU::COPY), Vgpr).add(*Def); VGPRCopies[CopyToVGPR] = Vgpr; } auto Tmp = MRI->createVirtualRegister(&AMDGPU::AGPR_32RegClass); BuildMI(MBB, UseMI, DL, TII->get(AMDGPU::V_ACCVGPR_WRITE_B32_e64), Tmp).addReg(Vgpr); B.addReg(Tmp); } B.addImm(Defs[I].second); } LLVM_DEBUG(dbgs() << "Folded " << *UseMI << '\n'); return; } if (Size != 4) return; if (TRI->isAGPR(*MRI, UseMI->getOperand(0).getReg()) && TRI->isVGPR(*MRI, UseMI->getOperand(1).getReg())) UseMI->setDesc(TII->get(AMDGPU::V_ACCVGPR_WRITE_B32_e64)); else if (TRI->isVGPR(*MRI, UseMI->getOperand(0).getReg()) && TRI->isAGPR(*MRI, UseMI->getOperand(1).getReg())) UseMI->setDesc(TII->get(AMDGPU::V_ACCVGPR_READ_B32_e64)); return; } unsigned UseOpc = UseMI->getOpcode(); if (UseOpc == AMDGPU::V_READFIRSTLANE_B32 || (UseOpc == AMDGPU::V_READLANE_B32 && (int)UseOpIdx == AMDGPU::getNamedOperandIdx(UseOpc, AMDGPU::OpName::src0))) { // %vgpr = V_MOV_B32 imm // %sgpr = V_READFIRSTLANE_B32 %vgpr // => // %sgpr = S_MOV_B32 imm if (FoldingImmLike) { if (execMayBeModifiedBeforeUse(*MRI, UseMI->getOperand(UseOpIdx).getReg(), *OpToFold.getParent(), *UseMI)) return; UseMI->setDesc(TII->get(AMDGPU::S_MOV_B32)); if (OpToFold.isImm()) UseMI->getOperand(1).ChangeToImmediate(OpToFold.getImm()); else UseMI->getOperand(1).ChangeToFrameIndex(OpToFold.getIndex()); UseMI->RemoveOperand(2); // Remove exec read (or src1 for readlane) return; } if (OpToFold.isReg() && TRI->isSGPRReg(*MRI, OpToFold.getReg())) { if (execMayBeModifiedBeforeUse(*MRI, UseMI->getOperand(UseOpIdx).getReg(), *OpToFold.getParent(), *UseMI)) return; // %vgpr = COPY %sgpr0 // %sgpr1 = V_READFIRSTLANE_B32 %vgpr // => // %sgpr1 = COPY %sgpr0 UseMI->setDesc(TII->get(AMDGPU::COPY)); UseMI->getOperand(1).setReg(OpToFold.getReg()); UseMI->getOperand(1).setSubReg(OpToFold.getSubReg()); UseMI->getOperand(1).setIsKill(false); UseMI->RemoveOperand(2); // Remove exec read (or src1 for readlane) return; } } const MCInstrDesc &UseDesc = UseMI->getDesc(); // Don't fold into target independent nodes. Target independent opcodes // don't have defined register classes. if (UseDesc.isVariadic() || UseOp.isImplicit() || UseDesc.OpInfo[UseOpIdx].RegClass == -1) return; } if (!FoldingImmLike) { tryAddToFoldList(FoldList, UseMI, UseOpIdx, &OpToFold, TII); // FIXME: We could try to change the instruction from 64-bit to 32-bit // to enable more folding opportunites. The shrink operands pass // already does this. return; } const MCInstrDesc &FoldDesc = OpToFold.getParent()->getDesc(); const TargetRegisterClass *FoldRC = TRI->getRegClass(FoldDesc.OpInfo[0].RegClass); // Split 64-bit constants into 32-bits for folding. if (UseOp.getSubReg() && AMDGPU::getRegBitWidth(FoldRC->getID()) == 64) { Register UseReg = UseOp.getReg(); const TargetRegisterClass *UseRC = MRI->getRegClass(UseReg); if (AMDGPU::getRegBitWidth(UseRC->getID()) != 64) return; APInt Imm(64, OpToFold.getImm()); if (UseOp.getSubReg() == AMDGPU::sub0) { Imm = Imm.getLoBits(32); } else { assert(UseOp.getSubReg() == AMDGPU::sub1); Imm = Imm.getHiBits(32); } MachineOperand ImmOp = MachineOperand::CreateImm(Imm.getSExtValue()); tryAddToFoldList(FoldList, UseMI, UseOpIdx, &ImmOp, TII); return; } tryAddToFoldList(FoldList, UseMI, UseOpIdx, &OpToFold, TII); } static bool evalBinaryInstruction(unsigned Opcode, int32_t &Result, uint32_t LHS, uint32_t RHS) { switch (Opcode) { case AMDGPU::V_AND_B32_e64: case AMDGPU::V_AND_B32_e32: case AMDGPU::S_AND_B32: Result = LHS & RHS; return true; case AMDGPU::V_OR_B32_e64: case AMDGPU::V_OR_B32_e32: case AMDGPU::S_OR_B32: Result = LHS | RHS; return true; case AMDGPU::V_XOR_B32_e64: case AMDGPU::V_XOR_B32_e32: case AMDGPU::S_XOR_B32: Result = LHS ^ RHS; return true; case AMDGPU::S_XNOR_B32: Result = ~(LHS ^ RHS); return true; case AMDGPU::S_NAND_B32: Result = ~(LHS & RHS); return true; case AMDGPU::S_NOR_B32: Result = ~(LHS | RHS); return true; case AMDGPU::S_ANDN2_B32: Result = LHS & ~RHS; return true; case AMDGPU::S_ORN2_B32: Result = LHS | ~RHS; return true; case AMDGPU::V_LSHL_B32_e64: case AMDGPU::V_LSHL_B32_e32: case AMDGPU::S_LSHL_B32: // The instruction ignores the high bits for out of bounds shifts. Result = LHS << (RHS & 31); return true; case AMDGPU::V_LSHLREV_B32_e64: case AMDGPU::V_LSHLREV_B32_e32: Result = RHS << (LHS & 31); return true; case AMDGPU::V_LSHR_B32_e64: case AMDGPU::V_LSHR_B32_e32: case AMDGPU::S_LSHR_B32: Result = LHS >> (RHS & 31); return true; case AMDGPU::V_LSHRREV_B32_e64: case AMDGPU::V_LSHRREV_B32_e32: Result = RHS >> (LHS & 31); return true; case AMDGPU::V_ASHR_I32_e64: case AMDGPU::V_ASHR_I32_e32: case AMDGPU::S_ASHR_I32: Result = static_cast(LHS) >> (RHS & 31); return true; case AMDGPU::V_ASHRREV_I32_e64: case AMDGPU::V_ASHRREV_I32_e32: Result = static_cast(RHS) >> (LHS & 31); return true; default: return false; } } static unsigned getMovOpc(bool IsScalar) { return IsScalar ? AMDGPU::S_MOV_B32 : AMDGPU::V_MOV_B32_e32; } /// Remove any leftover implicit operands from mutating the instruction. e.g. /// if we replace an s_and_b32 with a copy, we don't need the implicit scc def /// anymore. static void stripExtraCopyOperands(MachineInstr &MI) { const MCInstrDesc &Desc = MI.getDesc(); unsigned NumOps = Desc.getNumOperands() + Desc.getNumImplicitUses() + Desc.getNumImplicitDefs(); for (unsigned I = MI.getNumOperands() - 1; I >= NumOps; --I) MI.RemoveOperand(I); } static void mutateCopyOp(MachineInstr &MI, const MCInstrDesc &NewDesc) { MI.setDesc(NewDesc); stripExtraCopyOperands(MI); } static MachineOperand *getImmOrMaterializedImm(MachineRegisterInfo &MRI, MachineOperand &Op) { if (Op.isReg()) { // If this has a subregister, it obviously is a register source. if (Op.getSubReg() != AMDGPU::NoSubRegister || !Op.getReg().isVirtual()) return &Op; MachineInstr *Def = MRI.getVRegDef(Op.getReg()); if (Def && Def->isMoveImmediate()) { MachineOperand &ImmSrc = Def->getOperand(1); if (ImmSrc.isImm()) return &ImmSrc; } } return &Op; } // Try to simplify operations with a constant that may appear after instruction // selection. // TODO: See if a frame index with a fixed offset can fold. static bool tryConstantFoldOp(MachineRegisterInfo &MRI, const SIInstrInfo *TII, MachineInstr *MI, MachineOperand *ImmOp) { unsigned Opc = MI->getOpcode(); if (Opc == AMDGPU::V_NOT_B32_e64 || Opc == AMDGPU::V_NOT_B32_e32 || Opc == AMDGPU::S_NOT_B32) { MI->getOperand(1).ChangeToImmediate(~ImmOp->getImm()); mutateCopyOp(*MI, TII->get(getMovOpc(Opc == AMDGPU::S_NOT_B32))); return true; } int Src1Idx = AMDGPU::getNamedOperandIdx(Opc, AMDGPU::OpName::src1); if (Src1Idx == -1) return false; int Src0Idx = AMDGPU::getNamedOperandIdx(Opc, AMDGPU::OpName::src0); MachineOperand *Src0 = getImmOrMaterializedImm(MRI, MI->getOperand(Src0Idx)); MachineOperand *Src1 = getImmOrMaterializedImm(MRI, MI->getOperand(Src1Idx)); if (!Src0->isImm() && !Src1->isImm()) return false; // and k0, k1 -> v_mov_b32 (k0 & k1) // or k0, k1 -> v_mov_b32 (k0 | k1) // xor k0, k1 -> v_mov_b32 (k0 ^ k1) if (Src0->isImm() && Src1->isImm()) { int32_t NewImm; if (!evalBinaryInstruction(Opc, NewImm, Src0->getImm(), Src1->getImm())) return false; const SIRegisterInfo &TRI = TII->getRegisterInfo(); bool IsSGPR = TRI.isSGPRReg(MRI, MI->getOperand(0).getReg()); // Be careful to change the right operand, src0 may belong to a different // instruction. MI->getOperand(Src0Idx).ChangeToImmediate(NewImm); MI->RemoveOperand(Src1Idx); mutateCopyOp(*MI, TII->get(getMovOpc(IsSGPR))); return true; } if (!MI->isCommutable()) return false; if (Src0->isImm() && !Src1->isImm()) { std::swap(Src0, Src1); std::swap(Src0Idx, Src1Idx); } int32_t Src1Val = static_cast(Src1->getImm()); if (Opc == AMDGPU::V_OR_B32_e64 || Opc == AMDGPU::V_OR_B32_e32 || Opc == AMDGPU::S_OR_B32) { if (Src1Val == 0) { // y = or x, 0 => y = copy x MI->RemoveOperand(Src1Idx); mutateCopyOp(*MI, TII->get(AMDGPU::COPY)); } else if (Src1Val == -1) { // y = or x, -1 => y = v_mov_b32 -1 MI->RemoveOperand(Src1Idx); mutateCopyOp(*MI, TII->get(getMovOpc(Opc == AMDGPU::S_OR_B32))); } else return false; return true; } if (MI->getOpcode() == AMDGPU::V_AND_B32_e64 || MI->getOpcode() == AMDGPU::V_AND_B32_e32 || MI->getOpcode() == AMDGPU::S_AND_B32) { if (Src1Val == 0) { // y = and x, 0 => y = v_mov_b32 0 MI->RemoveOperand(Src0Idx); mutateCopyOp(*MI, TII->get(getMovOpc(Opc == AMDGPU::S_AND_B32))); } else if (Src1Val == -1) { // y = and x, -1 => y = copy x MI->RemoveOperand(Src1Idx); mutateCopyOp(*MI, TII->get(AMDGPU::COPY)); stripExtraCopyOperands(*MI); } else return false; return true; } if (MI->getOpcode() == AMDGPU::V_XOR_B32_e64 || MI->getOpcode() == AMDGPU::V_XOR_B32_e32 || MI->getOpcode() == AMDGPU::S_XOR_B32) { if (Src1Val == 0) { // y = xor x, 0 => y = copy x MI->RemoveOperand(Src1Idx); mutateCopyOp(*MI, TII->get(AMDGPU::COPY)); return true; } } return false; } // Try to fold an instruction into a simpler one static bool tryFoldInst(const SIInstrInfo *TII, MachineInstr *MI) { unsigned Opc = MI->getOpcode(); if (Opc == AMDGPU::V_CNDMASK_B32_e32 || Opc == AMDGPU::V_CNDMASK_B32_e64 || Opc == AMDGPU::V_CNDMASK_B64_PSEUDO) { const MachineOperand *Src0 = TII->getNamedOperand(*MI, AMDGPU::OpName::src0); const MachineOperand *Src1 = TII->getNamedOperand(*MI, AMDGPU::OpName::src1); int Src1ModIdx = AMDGPU::getNamedOperandIdx(Opc, AMDGPU::OpName::src1_modifiers); int Src0ModIdx = AMDGPU::getNamedOperandIdx(Opc, AMDGPU::OpName::src0_modifiers); if (Src1->isIdenticalTo(*Src0) && (Src1ModIdx == -1 || !MI->getOperand(Src1ModIdx).getImm()) && (Src0ModIdx == -1 || !MI->getOperand(Src0ModIdx).getImm())) { LLVM_DEBUG(dbgs() << "Folded " << *MI << " into "); auto &NewDesc = TII->get(Src0->isReg() ? (unsigned)AMDGPU::COPY : getMovOpc(false)); int Src2Idx = AMDGPU::getNamedOperandIdx(Opc, AMDGPU::OpName::src2); if (Src2Idx != -1) MI->RemoveOperand(Src2Idx); MI->RemoveOperand(AMDGPU::getNamedOperandIdx(Opc, AMDGPU::OpName::src1)); if (Src1ModIdx != -1) MI->RemoveOperand(Src1ModIdx); if (Src0ModIdx != -1) MI->RemoveOperand(Src0ModIdx); mutateCopyOp(*MI, NewDesc); LLVM_DEBUG(dbgs() << *MI << '\n'); return true; } } return false; } void SIFoldOperands::foldInstOperand(MachineInstr &MI, MachineOperand &OpToFold) const { // We need mutate the operands of new mov instructions to add implicit // uses of EXEC, but adding them invalidates the use_iterator, so defer // this. SmallVector CopiesToReplace; SmallVector FoldList; MachineOperand &Dst = MI.getOperand(0); bool FoldingImm = OpToFold.isImm() || OpToFold.isFI() || OpToFold.isGlobal(); if (FoldingImm) { unsigned NumLiteralUses = 0; MachineOperand *NonInlineUse = nullptr; int NonInlineUseOpNo = -1; MachineRegisterInfo::use_nodbg_iterator NextUse; for (MachineRegisterInfo::use_nodbg_iterator Use = MRI->use_nodbg_begin(Dst.getReg()), E = MRI->use_nodbg_end(); Use != E; Use = NextUse) { NextUse = std::next(Use); MachineInstr *UseMI = Use->getParent(); unsigned OpNo = Use.getOperandNo(); // Folding the immediate may reveal operations that can be constant // folded or replaced with a copy. This can happen for example after // frame indices are lowered to constants or from splitting 64-bit // constants. // // We may also encounter cases where one or both operands are // immediates materialized into a register, which would ordinarily not // be folded due to multiple uses or operand constraints. if (OpToFold.isImm() && tryConstantFoldOp(*MRI, TII, UseMI, &OpToFold)) { LLVM_DEBUG(dbgs() << "Constant folded " << *UseMI << '\n'); // Some constant folding cases change the same immediate's use to a new // instruction, e.g. and x, 0 -> 0. Make sure we re-visit the user // again. The same constant folded instruction could also have a second // use operand. NextUse = MRI->use_nodbg_begin(Dst.getReg()); FoldList.clear(); continue; } // Try to fold any inline immediate uses, and then only fold other // constants if they have one use. // // The legality of the inline immediate must be checked based on the use // operand, not the defining instruction, because 32-bit instructions // with 32-bit inline immediate sources may be used to materialize // constants used in 16-bit operands. // // e.g. it is unsafe to fold: // s_mov_b32 s0, 1.0 // materializes 0x3f800000 // v_add_f16 v0, v1, s0 // 1.0 f16 inline immediate sees 0x00003c00 // Folding immediates with more than one use will increase program size. // FIXME: This will also reduce register usage, which may be better // in some cases. A better heuristic is needed. if (isInlineConstantIfFolded(TII, *UseMI, OpNo, OpToFold)) { foldOperand(OpToFold, UseMI, OpNo, FoldList, CopiesToReplace); } else if (frameIndexMayFold(TII, *UseMI, OpNo, OpToFold)) { foldOperand(OpToFold, UseMI, OpNo, FoldList, CopiesToReplace); } else { if (++NumLiteralUses == 1) { NonInlineUse = &*Use; NonInlineUseOpNo = OpNo; } } } if (NumLiteralUses == 1) { MachineInstr *UseMI = NonInlineUse->getParent(); foldOperand(OpToFold, UseMI, NonInlineUseOpNo, FoldList, CopiesToReplace); } } else { // Folding register. SmallVector UsesToProcess; for (MachineRegisterInfo::use_nodbg_iterator Use = MRI->use_nodbg_begin(Dst.getReg()), E = MRI->use_nodbg_end(); Use != E; ++Use) { UsesToProcess.push_back(Use); } for (auto U : UsesToProcess) { MachineInstr *UseMI = U->getParent(); foldOperand(OpToFold, UseMI, U.getOperandNo(), FoldList, CopiesToReplace); } } MachineFunction *MF = MI.getParent()->getParent(); // Make sure we add EXEC uses to any new v_mov instructions created. for (MachineInstr *Copy : CopiesToReplace) Copy->addImplicitDefUseOperands(*MF); SmallPtrSet Folded; for (FoldCandidate &Fold : FoldList) { assert(!Fold.isReg() || Fold.OpToFold); if (Folded.count(Fold.UseMI)) continue; if (Fold.isReg() && Fold.OpToFold->getReg().isVirtual()) { Register Reg = Fold.OpToFold->getReg(); MachineInstr *DefMI = Fold.OpToFold->getParent(); if (DefMI->readsRegister(AMDGPU::EXEC, TRI) && execMayBeModifiedBeforeUse(*MRI, Reg, *DefMI, *Fold.UseMI)) continue; } if (updateOperand(Fold, *TII, *TRI, *ST)) { // Clear kill flags. if (Fold.isReg()) { assert(Fold.OpToFold && Fold.OpToFold->isReg()); // FIXME: Probably shouldn't bother trying to fold if not an // SGPR. PeepholeOptimizer can eliminate redundant VGPR->VGPR // copies. MRI->clearKillFlags(Fold.OpToFold->getReg()); } LLVM_DEBUG(dbgs() << "Folded source from " << MI << " into OpNo " << static_cast(Fold.UseOpNo) << " of " << *Fold.UseMI << '\n'); if (tryFoldInst(TII, Fold.UseMI)) Folded.insert(Fold.UseMI); } else if (Fold.isCommuted()) { // Restoring instruction's original operand order if fold has failed. TII->commuteInstruction(*Fold.UseMI, false); } } } // Clamp patterns are canonically selected to v_max_* instructions, so only // handle them. const MachineOperand *SIFoldOperands::isClamp(const MachineInstr &MI) const { unsigned Op = MI.getOpcode(); switch (Op) { case AMDGPU::V_MAX_F32_e64: case AMDGPU::V_MAX_F16_e64: case AMDGPU::V_MAX_F64_e64: case AMDGPU::V_PK_MAX_F16: { if (!TII->getNamedOperand(MI, AMDGPU::OpName::clamp)->getImm()) return nullptr; // Make sure sources are identical. const MachineOperand *Src0 = TII->getNamedOperand(MI, AMDGPU::OpName::src0); const MachineOperand *Src1 = TII->getNamedOperand(MI, AMDGPU::OpName::src1); if (!Src0->isReg() || !Src1->isReg() || Src0->getReg() != Src1->getReg() || Src0->getSubReg() != Src1->getSubReg() || Src0->getSubReg() != AMDGPU::NoSubRegister) return nullptr; // Can't fold up if we have modifiers. if (TII->hasModifiersSet(MI, AMDGPU::OpName::omod)) return nullptr; unsigned Src0Mods = TII->getNamedOperand(MI, AMDGPU::OpName::src0_modifiers)->getImm(); unsigned Src1Mods = TII->getNamedOperand(MI, AMDGPU::OpName::src1_modifiers)->getImm(); // Having a 0 op_sel_hi would require swizzling the output in the source // instruction, which we can't do. unsigned UnsetMods = (Op == AMDGPU::V_PK_MAX_F16) ? SISrcMods::OP_SEL_1 : 0u; if (Src0Mods != UnsetMods && Src1Mods != UnsetMods) return nullptr; return Src0; } default: return nullptr; } } // We obviously have multiple uses in a clamp since the register is used twice // in the same instruction. static bool hasOneNonDBGUseInst(const MachineRegisterInfo &MRI, unsigned Reg) { int Count = 0; for (auto I = MRI.use_instr_nodbg_begin(Reg), E = MRI.use_instr_nodbg_end(); I != E; ++I) { if (++Count > 1) return false; } return true; } // FIXME: Clamp for v_mad_mixhi_f16 handled during isel. bool SIFoldOperands::tryFoldClamp(MachineInstr &MI) { const MachineOperand *ClampSrc = isClamp(MI); if (!ClampSrc || !hasOneNonDBGUseInst(*MRI, ClampSrc->getReg())) return false; MachineInstr *Def = MRI->getVRegDef(ClampSrc->getReg()); // The type of clamp must be compatible. if (TII->getClampMask(*Def) != TII->getClampMask(MI)) return false; MachineOperand *DefClamp = TII->getNamedOperand(*Def, AMDGPU::OpName::clamp); if (!DefClamp) return false; LLVM_DEBUG(dbgs() << "Folding clamp " << *DefClamp << " into " << *Def << '\n'); // Clamp is applied after omod, so it is OK if omod is set. DefClamp->setImm(1); MRI->replaceRegWith(MI.getOperand(0).getReg(), Def->getOperand(0).getReg()); MI.eraseFromParent(); return true; } static int getOModValue(unsigned Opc, int64_t Val) { switch (Opc) { case AMDGPU::V_MUL_F32_e64: { switch (static_cast(Val)) { case 0x3f000000: // 0.5 return SIOutMods::DIV2; case 0x40000000: // 2.0 return SIOutMods::MUL2; case 0x40800000: // 4.0 return SIOutMods::MUL4; default: return SIOutMods::NONE; } } case AMDGPU::V_MUL_F16_e64: { switch (static_cast(Val)) { case 0x3800: // 0.5 return SIOutMods::DIV2; case 0x4000: // 2.0 return SIOutMods::MUL2; case 0x4400: // 4.0 return SIOutMods::MUL4; default: return SIOutMods::NONE; } } default: llvm_unreachable("invalid mul opcode"); } } // FIXME: Does this really not support denormals with f16? // FIXME: Does this need to check IEEE mode bit? SNaNs are generally not // handled, so will anything other than that break? std::pair SIFoldOperands::isOMod(const MachineInstr &MI) const { unsigned Op = MI.getOpcode(); switch (Op) { case AMDGPU::V_MUL_F32_e64: case AMDGPU::V_MUL_F16_e64: { // If output denormals are enabled, omod is ignored. if ((Op == AMDGPU::V_MUL_F32_e64 && MFI->getMode().FP32OutputDenormals) || (Op == AMDGPU::V_MUL_F16_e64 && MFI->getMode().FP64FP16OutputDenormals)) return std::make_pair(nullptr, SIOutMods::NONE); const MachineOperand *RegOp = nullptr; const MachineOperand *ImmOp = nullptr; const MachineOperand *Src0 = TII->getNamedOperand(MI, AMDGPU::OpName::src0); const MachineOperand *Src1 = TII->getNamedOperand(MI, AMDGPU::OpName::src1); if (Src0->isImm()) { ImmOp = Src0; RegOp = Src1; } else if (Src1->isImm()) { ImmOp = Src1; RegOp = Src0; } else return std::make_pair(nullptr, SIOutMods::NONE); int OMod = getOModValue(Op, ImmOp->getImm()); if (OMod == SIOutMods::NONE || TII->hasModifiersSet(MI, AMDGPU::OpName::src0_modifiers) || TII->hasModifiersSet(MI, AMDGPU::OpName::src1_modifiers) || TII->hasModifiersSet(MI, AMDGPU::OpName::omod) || TII->hasModifiersSet(MI, AMDGPU::OpName::clamp)) return std::make_pair(nullptr, SIOutMods::NONE); return std::make_pair(RegOp, OMod); } case AMDGPU::V_ADD_F32_e64: case AMDGPU::V_ADD_F16_e64: { // If output denormals are enabled, omod is ignored. if ((Op == AMDGPU::V_ADD_F32_e64 && MFI->getMode().FP32OutputDenormals) || (Op == AMDGPU::V_ADD_F16_e64 && MFI->getMode().FP64FP16OutputDenormals)) return std::make_pair(nullptr, SIOutMods::NONE); // Look through the DAGCombiner canonicalization fmul x, 2 -> fadd x, x const MachineOperand *Src0 = TII->getNamedOperand(MI, AMDGPU::OpName::src0); const MachineOperand *Src1 = TII->getNamedOperand(MI, AMDGPU::OpName::src1); if (Src0->isReg() && Src1->isReg() && Src0->getReg() == Src1->getReg() && Src0->getSubReg() == Src1->getSubReg() && !TII->hasModifiersSet(MI, AMDGPU::OpName::src0_modifiers) && !TII->hasModifiersSet(MI, AMDGPU::OpName::src1_modifiers) && !TII->hasModifiersSet(MI, AMDGPU::OpName::clamp) && !TII->hasModifiersSet(MI, AMDGPU::OpName::omod)) return std::make_pair(Src0, SIOutMods::MUL2); return std::make_pair(nullptr, SIOutMods::NONE); } default: return std::make_pair(nullptr, SIOutMods::NONE); } } // FIXME: Does this need to check IEEE bit on function? bool SIFoldOperands::tryFoldOMod(MachineInstr &MI) { const MachineOperand *RegOp; int OMod; std::tie(RegOp, OMod) = isOMod(MI); if (OMod == SIOutMods::NONE || !RegOp->isReg() || RegOp->getSubReg() != AMDGPU::NoSubRegister || !hasOneNonDBGUseInst(*MRI, RegOp->getReg())) return false; MachineInstr *Def = MRI->getVRegDef(RegOp->getReg()); MachineOperand *DefOMod = TII->getNamedOperand(*Def, AMDGPU::OpName::omod); if (!DefOMod || DefOMod->getImm() != SIOutMods::NONE) return false; // Clamp is applied after omod. If the source already has clamp set, don't // fold it. if (TII->hasModifiersSet(*Def, AMDGPU::OpName::clamp)) return false; LLVM_DEBUG(dbgs() << "Folding omod " << MI << " into " << *Def << '\n'); DefOMod->setImm(OMod); MRI->replaceRegWith(MI.getOperand(0).getReg(), Def->getOperand(0).getReg()); MI.eraseFromParent(); return true; } bool SIFoldOperands::runOnMachineFunction(MachineFunction &MF) { if (skipFunction(MF.getFunction())) return false; MRI = &MF.getRegInfo(); ST = &MF.getSubtarget(); TII = ST->getInstrInfo(); TRI = &TII->getRegisterInfo(); MFI = MF.getInfo(); // omod is ignored by hardware if IEEE bit is enabled. omod also does not // correctly handle signed zeros. // // FIXME: Also need to check strictfp bool IsIEEEMode = MFI->getMode().IEEE; bool HasNSZ = MFI->hasNoSignedZerosFPMath(); for (MachineBasicBlock *MBB : depth_first(&MF)) { MachineBasicBlock::iterator I, Next; MachineOperand *CurrentKnownM0Val = nullptr; for (I = MBB->begin(); I != MBB->end(); I = Next) { Next = std::next(I); MachineInstr &MI = *I; tryFoldInst(TII, &MI); if (!TII->isFoldableCopy(MI)) { // Saw an unknown clobber of m0, so we no longer know what it is. if (CurrentKnownM0Val && MI.modifiesRegister(AMDGPU::M0, TRI)) CurrentKnownM0Val = nullptr; // TODO: Omod might be OK if there is NSZ only on the source // instruction, and not the omod multiply. if (IsIEEEMode || (!HasNSZ && !MI.getFlag(MachineInstr::FmNsz)) || !tryFoldOMod(MI)) tryFoldClamp(MI); continue; } // Specially track simple redefs of m0 to the same value in a block, so we // can erase the later ones. if (MI.getOperand(0).getReg() == AMDGPU::M0) { MachineOperand &NewM0Val = MI.getOperand(1); if (CurrentKnownM0Val && CurrentKnownM0Val->isIdenticalTo(NewM0Val)) { MI.eraseFromParent(); continue; } // We aren't tracking other physical registers CurrentKnownM0Val = (NewM0Val.isReg() && NewM0Val.getReg().isPhysical()) ? nullptr : &NewM0Val; continue; } MachineOperand &OpToFold = MI.getOperand(1); bool FoldingImm = OpToFold.isImm() || OpToFold.isFI() || OpToFold.isGlobal(); // FIXME: We could also be folding things like TargetIndexes. if (!FoldingImm && !OpToFold.isReg()) continue; if (OpToFold.isReg() && !OpToFold.getReg().isVirtual()) continue; // Prevent folding operands backwards in the function. For example, // the COPY opcode must not be replaced by 1 in this example: // // %3 = COPY %vgpr0; VGPR_32:%3 // ... // %vgpr0 = V_MOV_B32_e32 1, implicit %exec MachineOperand &Dst = MI.getOperand(0); if (Dst.isReg() && !Dst.getReg().isVirtual()) continue; foldInstOperand(MI, OpToFold); } } return true; }