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llvm / llvm-project / 089106fdfb853c83cf5d35a37bdd8e663094e6a2 / . / llvm / lib / Target / AMDGPU / SIFoldOperands.cpp
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//===-- 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 "SIFoldOperands.h"
#include "AMDGPU.h"
#include "GCNSubtarget.h"
#include "MCTargetDesc/AMDGPUMCTargetDesc.h"
#include "SIInstrInfo.h"
#include "SIMachineFunctionInfo.h"
#include "SIRegisterInfo.h"
#include "llvm/ADT/DepthFirstIterator.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineOperand.h"
#define DEBUG_TYPE "si-fold-operands"
using namespace llvm;
namespace {
/// Track a value we may want to fold into downstream users, applying
/// subregister extracts along the way.
struct FoldableDef {
union {
MachineOperand *OpToFold = nullptr;
uint64_t ImmToFold;
int FrameIndexToFold;
};
/// Register class of the originally defined value.
const TargetRegisterClass *DefRC = nullptr;
/// Track the original defining instruction for the value.
const MachineInstr *DefMI = nullptr;
/// Subregister to apply to the value at the use point.
unsigned DefSubReg = AMDGPU::NoSubRegister;
/// Kind of value stored in the union.
MachineOperand::MachineOperandType Kind;
FoldableDef() = delete;
FoldableDef(MachineOperand &FoldOp, const TargetRegisterClass *DefRC,
unsigned DefSubReg = AMDGPU::NoSubRegister)
: DefRC(DefRC), DefSubReg(DefSubReg), Kind(FoldOp.getType()) {
if (FoldOp.isImm()) {
ImmToFold = FoldOp.getImm();
} else if (FoldOp.isFI()) {
FrameIndexToFold = FoldOp.getIndex();
} else {
assert(FoldOp.isReg() || FoldOp.isGlobal());
OpToFold = &FoldOp;
}
DefMI = FoldOp.getParent();
}
FoldableDef(int64_t FoldImm, const TargetRegisterClass *DefRC,
unsigned DefSubReg = AMDGPU::NoSubRegister)
: ImmToFold(FoldImm), DefRC(DefRC), DefSubReg(DefSubReg),
Kind(MachineOperand::MO_Immediate) {}
/// Copy the current def and apply \p SubReg to the value.
FoldableDef getWithSubReg(const SIRegisterInfo &TRI, unsigned SubReg) const {
FoldableDef Copy(*this);
Copy.DefSubReg = TRI.composeSubRegIndices(DefSubReg, SubReg);
return Copy;
}
bool isReg() const { return Kind == MachineOperand::MO_Register; }
Register getReg() const {
assert(isReg());
return OpToFold->getReg();
}
unsigned getSubReg() const {
assert(isReg());
return OpToFold->getSubReg();
}
bool isImm() const { return Kind == MachineOperand::MO_Immediate; }
bool isFI() const {
return Kind == MachineOperand::MO_FrameIndex;
}
int getFI() const {
assert(isFI());
return FrameIndexToFold;
}
bool isGlobal() const { return Kind == MachineOperand::MO_GlobalAddress; }
/// Return the effective immediate value defined by this instruction, after
/// application of any subregister extracts which may exist between the use
/// and def instruction.
std::optional<int64_t> getEffectiveImmVal() const {
assert(isImm());
return SIInstrInfo::extractSubregFromImm(ImmToFold, DefSubReg);
}
/// Check if it is legal to fold this effective value into \p MI's \p OpNo
/// operand.
bool isOperandLegal(const SIInstrInfo &TII, const MachineInstr &MI,
unsigned OpIdx) const {
switch (Kind) {
case MachineOperand::MO_Immediate: {
std::optional<int64_t> ImmToFold = getEffectiveImmVal();
if (!ImmToFold)
return false;
// TODO: Should verify the subregister index is supported by the class
// TODO: Avoid the temporary MachineOperand
MachineOperand TmpOp = MachineOperand::CreateImm(*ImmToFold);
return TII.isOperandLegal(MI, OpIdx, &TmpOp);
}
case MachineOperand::MO_FrameIndex: {
if (DefSubReg != AMDGPU::NoSubRegister)
return false;
MachineOperand TmpOp = MachineOperand::CreateFI(FrameIndexToFold);
return TII.isOperandLegal(MI, OpIdx, &TmpOp);
}
default:
// TODO: Try to apply DefSubReg, for global address we can extract
// low/high.
if (DefSubReg != AMDGPU::NoSubRegister)
return false;
return TII.isOperandLegal(MI, OpIdx, OpToFold);
}
llvm_unreachable("covered MachineOperand kind switch");
}
};
struct FoldCandidate {
MachineInstr *UseMI;
FoldableDef Def;
int ShrinkOpcode;
unsigned UseOpNo;
bool Commuted;
FoldCandidate(MachineInstr *MI, unsigned OpNo, FoldableDef Def,
bool Commuted = false, int ShrinkOp = -1)
: UseMI(MI), Def(Def), ShrinkOpcode(ShrinkOp), UseOpNo(OpNo),
Commuted(Commuted) {}
bool isFI() const { return Def.isFI(); }
int getFI() const {
assert(isFI());
return Def.FrameIndexToFold;
}
bool isImm() const { return Def.isImm(); }
bool isReg() const { return Def.isReg(); }
Register getReg() const { return Def.getReg(); }
bool isGlobal() const { return Def.isGlobal(); }
bool needsShrink() const { return ShrinkOpcode != -1; }
};
class SIFoldOperandsImpl {
public:
MachineRegisterInfo *MRI;
const SIInstrInfo *TII;
const SIRegisterInfo *TRI;
const GCNSubtarget *ST;
const SIMachineFunctionInfo *MFI;
bool frameIndexMayFold(const MachineInstr &UseMI, int OpNo,
const FoldableDef &OpToFold) const;
// TODO: Just use TII::getVALUOp
unsigned convertToVALUOp(unsigned Opc, bool UseVOP3 = false) const {
switch (Opc) {
case AMDGPU::S_ADD_I32: {
if (ST->hasAddNoCarry())
return UseVOP3 ? AMDGPU::V_ADD_U32_e64 : AMDGPU::V_ADD_U32_e32;
return UseVOP3 ? AMDGPU::V_ADD_CO_U32_e64 : AMDGPU::V_ADD_CO_U32_e32;
}
case AMDGPU::S_OR_B32:
return UseVOP3 ? AMDGPU::V_OR_B32_e64 : AMDGPU::V_OR_B32_e32;
case AMDGPU::S_AND_B32:
return UseVOP3 ? AMDGPU::V_AND_B32_e64 : AMDGPU::V_AND_B32_e32;
case AMDGPU::S_MUL_I32:
return AMDGPU::V_MUL_LO_U32_e64;
default:
return AMDGPU::INSTRUCTION_LIST_END;
}
}
bool foldCopyToVGPROfScalarAddOfFrameIndex(Register DstReg, Register SrcReg,
MachineInstr &MI) const;
bool updateOperand(FoldCandidate &Fold) const;
bool canUseImmWithOpSel(const MachineInstr *MI, unsigned UseOpNo,
int64_t ImmVal) const;
/// Try to fold immediate \p ImmVal into \p MI's operand at index \p UseOpNo.
bool tryFoldImmWithOpSel(MachineInstr *MI, unsigned UseOpNo,
int64_t ImmVal) const;
bool tryAddToFoldList(SmallVectorImpl<FoldCandidate> &FoldList,
MachineInstr *MI, unsigned OpNo,
const FoldableDef &OpToFold) const;
bool isUseSafeToFold(const MachineInstr &MI,
const MachineOperand &UseMO) const;
const TargetRegisterClass *getRegSeqInit(
MachineInstr &RegSeq,
SmallVectorImpl<std::pair<MachineOperand *, unsigned>> &Defs) const;
const TargetRegisterClass *
getRegSeqInit(SmallVectorImpl<std::pair<MachineOperand *, unsigned>> &Defs,
Register UseReg) const;
std::pair<int64_t, const TargetRegisterClass *>
isRegSeqSplat(MachineInstr &RegSeg) const;
bool tryFoldRegSeqSplat(MachineInstr *UseMI, unsigned UseOpIdx,
int64_t SplatVal,
const TargetRegisterClass *SplatRC) const;
bool tryToFoldACImm(const FoldableDef &OpToFold, MachineInstr *UseMI,
unsigned UseOpIdx,
SmallVectorImpl<FoldCandidate> &FoldList) const;
void foldOperand(FoldableDef OpToFold, MachineInstr *UseMI, int UseOpIdx,
SmallVectorImpl<FoldCandidate> &FoldList,
SmallVectorImpl<MachineInstr *> &CopiesToReplace) const;
std::optional<int64_t> getImmOrMaterializedImm(MachineOperand &Op) const;
bool tryConstantFoldOp(MachineInstr *MI) const;
bool tryFoldCndMask(MachineInstr &MI) const;
bool tryFoldZeroHighBits(MachineInstr &MI) const;
bool foldInstOperand(MachineInstr &MI, const FoldableDef &OpToFold) const;
bool foldCopyToAGPRRegSequence(MachineInstr *CopyMI) const;
bool tryFoldFoldableCopy(MachineInstr &MI,
MachineOperand *&CurrentKnownM0Val) const;
const MachineOperand *isClamp(const MachineInstr &MI) const;
bool tryFoldClamp(MachineInstr &MI);
std::pair<const MachineOperand *, int> isOMod(const MachineInstr &MI) const;
bool tryFoldOMod(MachineInstr &MI);
bool tryFoldRegSequence(MachineInstr &MI);
bool tryFoldPhiAGPR(MachineInstr &MI);
bool tryFoldLoad(MachineInstr &MI);
bool tryOptimizeAGPRPhis(MachineBasicBlock &MBB);
public:
SIFoldOperandsImpl() = default;
bool run(MachineFunction &MF);
};
class SIFoldOperandsLegacy : public MachineFunctionPass {
public:
static char ID;
SIFoldOperandsLegacy() : MachineFunctionPass(ID) {}
bool runOnMachineFunction(MachineFunction &MF) override {
if (skipFunction(MF.getFunction()))
return false;
return SIFoldOperandsImpl().run(MF);
}
StringRef getPassName() const override { return "SI Fold Operands"; }
void getAnalysisUsage(AnalysisUsage &AU) const override {
AU.setPreservesCFG();
MachineFunctionPass::getAnalysisUsage(AU);
}
MachineFunctionProperties getRequiredProperties() const override {
return MachineFunctionProperties().setIsSSA();
}
};
} // End anonymous namespace.
INITIALIZE_PASS(SIFoldOperandsLegacy, DEBUG_TYPE, "SI Fold Operands", false,
false)
char SIFoldOperandsLegacy::ID = 0;
char &llvm::SIFoldOperandsLegacyID = SIFoldOperandsLegacy::ID;
static const TargetRegisterClass *getRegOpRC(const MachineRegisterInfo &MRI,
const TargetRegisterInfo &TRI,
const MachineOperand &MO) {
const TargetRegisterClass *RC = MRI.getRegClass(MO.getReg());
if (const TargetRegisterClass *SubRC =
TRI.getSubRegisterClass(RC, MO.getSubReg()))
RC = SubRC;
return RC;
}
// 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_F16_t16_e64:
return AMDGPU::V_FMA_F16_gfx9_t16_e64;
case AMDGPU::V_FMAC_F16_fake16_e64:
return AMDGPU::V_FMA_F16_gfx9_fake16_e64;
case AMDGPU::V_FMAC_LEGACY_F32_e64:
return AMDGPU::V_FMA_LEGACY_F32_e64;
case AMDGPU::V_FMAC_F64_e64:
return AMDGPU::V_FMA_F64_e64;
}
return AMDGPU::INSTRUCTION_LIST_END;
}
// TODO: Add heuristic that the frame index might not fit in the addressing mode
// immediate offset to avoid materializing in loops.
bool SIFoldOperandsImpl::frameIndexMayFold(const MachineInstr &UseMI, int OpNo,
const FoldableDef &OpToFold) const {
if (!OpToFold.isFI())
return false;
const unsigned Opc = UseMI.getOpcode();
switch (Opc) {
case AMDGPU::S_ADD_I32:
case AMDGPU::S_ADD_U32:
case AMDGPU::V_ADD_U32_e32:
case AMDGPU::V_ADD_CO_U32_e32:
// TODO: Possibly relax hasOneUse. It matters more for mubuf, since we have
// to insert the wave size shift at every point we use the index.
// TODO: Fix depending on visit order to fold immediates into the operand
return UseMI.getOperand(OpNo == 1 ? 2 : 1).isImm() &&
MRI->hasOneNonDBGUse(UseMI.getOperand(OpNo).getReg());
case AMDGPU::V_ADD_U32_e64:
case AMDGPU::V_ADD_CO_U32_e64:
return UseMI.getOperand(OpNo == 2 ? 3 : 2).isImm() &&
MRI->hasOneNonDBGUse(UseMI.getOperand(OpNo).getReg());
default:
break;
}
if (TII->isMUBUF(UseMI))
return OpNo == AMDGPU::getNamedOperandIdx(Opc, AMDGPU::OpName::vaddr);
if (!TII->isFLATScratch(UseMI))
return false;
int SIdx = AMDGPU::getNamedOperandIdx(Opc, AMDGPU::OpName::saddr);
if (OpNo == SIdx)
return true;
int VIdx = AMDGPU::getNamedOperandIdx(Opc, AMDGPU::OpName::vaddr);
return OpNo == VIdx && SIdx == -1;
}
/// Fold %vgpr = COPY (S_ADD_I32 x, frameindex)
///
/// => %vgpr = V_ADD_U32 x, frameindex
bool SIFoldOperandsImpl::foldCopyToVGPROfScalarAddOfFrameIndex(
Register DstReg, Register SrcReg, MachineInstr &MI) const {
if (TRI->isVGPR(*MRI, DstReg) && TRI->isSGPRReg(*MRI, SrcReg) &&
MRI->hasOneNonDBGUse(SrcReg)) {
MachineInstr *Def = MRI->getVRegDef(SrcReg);
if (!Def || Def->getNumOperands() != 4)
return false;
MachineOperand *Src0 = &Def->getOperand(1);
MachineOperand *Src1 = &Def->getOperand(2);
// TODO: This is profitable with more operand types, and for more
// opcodes. But ultimately this is working around poor / nonexistent
// regbankselect.
if (!Src0->isFI() && !Src1->isFI())
return false;
if (Src0->isFI())
std::swap(Src0, Src1);
const bool UseVOP3 = !Src0->isImm() || TII->isInlineConstant(*Src0);
unsigned NewOp = convertToVALUOp(Def->getOpcode(), UseVOP3);
if (NewOp == AMDGPU::INSTRUCTION_LIST_END ||
!Def->getOperand(3).isDead()) // Check if scc is dead
return false;
MachineBasicBlock *MBB = Def->getParent();
const DebugLoc &DL = Def->getDebugLoc();
if (NewOp != AMDGPU::V_ADD_CO_U32_e32) {
MachineInstrBuilder Add =
BuildMI(*MBB, *Def, DL, TII->get(NewOp), DstReg);
if (Add->getDesc().getNumDefs() == 2) {
Register CarryOutReg = MRI->createVirtualRegister(TRI->getBoolRC());
Add.addDef(CarryOutReg, RegState::Dead);
MRI->setRegAllocationHint(CarryOutReg, 0, TRI->getVCC());
}
Add.add(*Src0).add(*Src1).setMIFlags(Def->getFlags());
if (AMDGPU::hasNamedOperand(NewOp, AMDGPU::OpName::clamp))
Add.addImm(0);
Def->eraseFromParent();
MI.eraseFromParent();
return true;
}
assert(NewOp == AMDGPU::V_ADD_CO_U32_e32);
MachineBasicBlock::LivenessQueryResult Liveness =
MBB->computeRegisterLiveness(TRI, AMDGPU::VCC, *Def, 16);
if (Liveness == MachineBasicBlock::LQR_Dead) {
// TODO: If src1 satisfies operand constraints, use vop3 version.
BuildMI(*MBB, *Def, DL, TII->get(NewOp), DstReg)
.add(*Src0)
.add(*Src1)
.setOperandDead(3) // implicit-def $vcc
.setMIFlags(Def->getFlags());
Def->eraseFromParent();
MI.eraseFromParent();
return true;
}
}
return false;
}
FunctionPass *llvm::createSIFoldOperandsLegacyPass() {
return new SIFoldOperandsLegacy();
}
bool SIFoldOperandsImpl::canUseImmWithOpSel(const MachineInstr *MI,
unsigned UseOpNo,
int64_t ImmVal) const {
const uint64_t TSFlags = MI->getDesc().TSFlags;
if (!(TSFlags & SIInstrFlags::IsPacked) || (TSFlags & SIInstrFlags::IsMAI) ||
(TSFlags & SIInstrFlags::IsWMMA) || (TSFlags & SIInstrFlags::IsSWMMAC) ||
(ST->hasDOTOpSelHazard() && (TSFlags & SIInstrFlags::IsDOT)))
return false;
const MachineOperand &Old = MI->getOperand(UseOpNo);
int OpNo = MI->getOperandNo(&Old);
unsigned Opcode = MI->getOpcode();
uint8_t OpType = TII->get(Opcode).operands()[OpNo].OperandType;
switch (OpType) {
default:
return false;
case AMDGPU::OPERAND_REG_IMM_V2FP16:
case AMDGPU::OPERAND_REG_IMM_V2BF16:
case AMDGPU::OPERAND_REG_IMM_V2INT16:
case AMDGPU::OPERAND_REG_INLINE_C_V2FP16:
case AMDGPU::OPERAND_REG_INLINE_C_V2BF16:
case AMDGPU::OPERAND_REG_INLINE_C_V2INT16:
// VOP3 packed instructions ignore op_sel source modifiers, we cannot encode
// two different constants.
if ((TSFlags & SIInstrFlags::VOP3) && !(TSFlags & SIInstrFlags::VOP3P) &&
static_cast<uint16_t>(ImmVal) != static_cast<uint16_t>(ImmVal >> 16))
return false;
break;
}
return true;
}
bool SIFoldOperandsImpl::tryFoldImmWithOpSel(MachineInstr *MI, unsigned UseOpNo,
int64_t ImmVal) const {
MachineOperand &Old = MI->getOperand(UseOpNo);
unsigned Opcode = MI->getOpcode();
int OpNo = MI->getOperandNo(&Old);
uint8_t OpType = TII->get(Opcode).operands()[OpNo].OperandType;
// If the literal can be inlined as-is, apply it and short-circuit the
// tests below. The main motivation for this is to avoid unintuitive
// uses of opsel.
if (AMDGPU::isInlinableLiteralV216(ImmVal, OpType)) {
Old.ChangeToImmediate(ImmVal);
return true;
}
// Refer to op_sel/op_sel_hi and check if we can change the immediate and
// op_sel in a way that allows an inline constant.
AMDGPU::OpName ModName = AMDGPU::OpName::NUM_OPERAND_NAMES;
unsigned SrcIdx = ~0;
if (OpNo == AMDGPU::getNamedOperandIdx(Opcode, AMDGPU::OpName::src0)) {
ModName = AMDGPU::OpName::src0_modifiers;
SrcIdx = 0;
} else if (OpNo == AMDGPU::getNamedOperandIdx(Opcode, AMDGPU::OpName::src1)) {
ModName = AMDGPU::OpName::src1_modifiers;
SrcIdx = 1;
} else if (OpNo == AMDGPU::getNamedOperandIdx(Opcode, AMDGPU::OpName::src2)) {
ModName = AMDGPU::OpName::src2_modifiers;
SrcIdx = 2;
}
assert(ModName != AMDGPU::OpName::NUM_OPERAND_NAMES);
int ModIdx = AMDGPU::getNamedOperandIdx(Opcode, ModName);
MachineOperand &Mod = MI->getOperand(ModIdx);
unsigned ModVal = Mod.getImm();
uint16_t ImmLo =
static_cast<uint16_t>(ImmVal >> (ModVal & SISrcMods::OP_SEL_0 ? 16 : 0));
uint16_t ImmHi =
static_cast<uint16_t>(ImmVal >> (ModVal & SISrcMods::OP_SEL_1 ? 16 : 0));
uint32_t Imm = (static_cast<uint32_t>(ImmHi) << 16) | ImmLo;
unsigned NewModVal = ModVal & ~(SISrcMods::OP_SEL_0 | SISrcMods::OP_SEL_1);
// Helper function that attempts to inline the given value with a newly
// chosen opsel pattern.
auto tryFoldToInline = [&](uint32_t Imm) -> bool {
if (AMDGPU::isInlinableLiteralV216(Imm, OpType)) {
Mod.setImm(NewModVal | SISrcMods::OP_SEL_1);
Old.ChangeToImmediate(Imm);
return true;
}
// Try to shuffle the halves around and leverage opsel to get an inline
// constant.
uint16_t Lo = static_cast<uint16_t>(Imm);
uint16_t Hi = static_cast<uint16_t>(Imm >> 16);
if (Lo == Hi) {
if (AMDGPU::isInlinableLiteralV216(Lo, OpType)) {
Mod.setImm(NewModVal);
Old.ChangeToImmediate(Lo);
return true;
}
if (static_cast<int16_t>(Lo) < 0) {
int32_t SExt = static_cast<int16_t>(Lo);
if (AMDGPU::isInlinableLiteralV216(SExt, OpType)) {
Mod.setImm(NewModVal);
Old.ChangeToImmediate(SExt);
return true;
}
}
// This check is only useful for integer instructions
if (OpType == AMDGPU::OPERAND_REG_IMM_V2INT16) {
if (AMDGPU::isInlinableLiteralV216(Lo << 16, OpType)) {
Mod.setImm(NewModVal | SISrcMods::OP_SEL_0 | SISrcMods::OP_SEL_1);
Old.ChangeToImmediate(static_cast<uint32_t>(Lo) << 16);
return true;
}
}
} else {
uint32_t Swapped = (static_cast<uint32_t>(Lo) << 16) | Hi;
if (AMDGPU::isInlinableLiteralV216(Swapped, OpType)) {
Mod.setImm(NewModVal | SISrcMods::OP_SEL_0);
Old.ChangeToImmediate(Swapped);
return true;
}
}
return false;
};
if (tryFoldToInline(Imm))
return true;
// Replace integer addition by subtraction and vice versa if it allows
// folding the immediate to an inline constant.
//
// We should only ever get here for SrcIdx == 1 due to canonicalization
// earlier in the pipeline, but we double-check here to be safe / fully
// general.
bool IsUAdd = Opcode == AMDGPU::V_PK_ADD_U16;
bool IsUSub = Opcode == AMDGPU::V_PK_SUB_U16;
if (SrcIdx == 1 && (IsUAdd || IsUSub)) {
unsigned ClampIdx =
AMDGPU::getNamedOperandIdx(Opcode, AMDGPU::OpName::clamp);
bool Clamp = MI->getOperand(ClampIdx).getImm() != 0;
if (!Clamp) {
uint16_t NegLo = -static_cast<uint16_t>(Imm);
uint16_t NegHi = -static_cast<uint16_t>(Imm >> 16);
uint32_t NegImm = (static_cast<uint32_t>(NegHi) << 16) | NegLo;
if (tryFoldToInline(NegImm)) {
unsigned NegOpcode =
IsUAdd ? AMDGPU::V_PK_SUB_U16 : AMDGPU::V_PK_ADD_U16;
MI->setDesc(TII->get(NegOpcode));
return true;
}
}
}
return false;
}
bool SIFoldOperandsImpl::updateOperand(FoldCandidate &Fold) const {
MachineInstr *MI = Fold.UseMI;
MachineOperand &Old = MI->getOperand(Fold.UseOpNo);
assert(Old.isReg());
std::optional<int64_t> ImmVal;
if (Fold.isImm())
ImmVal = Fold.Def.getEffectiveImmVal();
if (ImmVal && canUseImmWithOpSel(Fold.UseMI, Fold.UseOpNo, *ImmVal)) {
if (tryFoldImmWithOpSel(Fold.UseMI, Fold.UseOpNo, *ImmVal))
return true;
// We can't represent the candidate as an inline constant. Try as a literal
// with the original opsel, checking constant bus limitations.
MachineOperand New = MachineOperand::CreateImm(*ImmVal);
int OpNo = MI->getOperandNo(&Old);
if (!TII->isOperandLegal(*MI, OpNo, &New))
return false;
Old.ChangeToImmediate(*ImmVal);
return true;
}
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;
}
int Op32 = Fold.ShrinkOpcode;
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.Commuted)
TII->commuteInstruction(*Inst32, false);
return true;
}
assert(!Fold.needsShrink() && "not handled");
if (ImmVal) {
if (Old.isTied()) {
int NewMFMAOpc = AMDGPU::getMFMAEarlyClobberOp(MI->getOpcode());
if (NewMFMAOpc == -1)
return false;
MI->setDesc(TII->get(NewMFMAOpc));
MI->untieRegOperand(0);
}
// TODO: Should we try to avoid adding this to the candidate list?
MachineOperand New = MachineOperand::CreateImm(*ImmVal);
int OpNo = MI->getOperandNo(&Old);
if (!TII->isOperandLegal(*MI, OpNo, &New))
return false;
Old.ChangeToImmediate(*ImmVal);
return true;
}
if (Fold.isGlobal()) {
Old.ChangeToGA(Fold.Def.OpToFold->getGlobal(),
Fold.Def.OpToFold->getOffset(),
Fold.Def.OpToFold->getTargetFlags());
return true;
}
if (Fold.isFI()) {
Old.ChangeToFrameIndex(Fold.getFI());
return true;
}
MachineOperand *New = Fold.Def.OpToFold;
// Rework once the VS_16 register class is updated to include proper
// 16-bit SGPRs instead of 32-bit ones.
if (Old.getSubReg() == AMDGPU::lo16 && TRI->isSGPRReg(*MRI, New->getReg()))
Old.setSubReg(AMDGPU::NoSubRegister);
Old.substVirtReg(New->getReg(), New->getSubReg(), *TRI);
Old.setIsUndef(New->isUndef());
return true;
}
static void appendFoldCandidate(SmallVectorImpl<FoldCandidate> &FoldList,
FoldCandidate &&Entry) {
// Skip additional folding on the same operand.
for (FoldCandidate &Fold : FoldList)
if (Fold.UseMI == Entry.UseMI && Fold.UseOpNo == Entry.UseOpNo)
return;
LLVM_DEBUG(dbgs() << "Append " << (Entry.Commuted ? "commuted" : "normal")
<< " operand " << Entry.UseOpNo << "\n " << *Entry.UseMI);
FoldList.push_back(Entry);
}
static void appendFoldCandidate(SmallVectorImpl<FoldCandidate> &FoldList,
MachineInstr *MI, unsigned OpNo,
const FoldableDef &FoldOp,
bool Commuted = false, int ShrinkOp = -1) {
appendFoldCandidate(FoldList,
FoldCandidate(MI, OpNo, FoldOp, Commuted, ShrinkOp));
}
bool SIFoldOperandsImpl::tryAddToFoldList(
SmallVectorImpl<FoldCandidate> &FoldList, MachineInstr *MI, unsigned OpNo,
const FoldableDef &OpToFold) const {
const unsigned Opc = MI->getOpcode();
auto tryToFoldAsFMAAKorMK = [&]() {
if (!OpToFold.isImm())
return false;
const bool TryAK = OpNo == 3;
const unsigned NewOpc = TryAK ? AMDGPU::S_FMAAK_F32 : AMDGPU::S_FMAMK_F32;
MI->setDesc(TII->get(NewOpc));
// We have to fold into operand which would be Imm not into OpNo.
bool FoldAsFMAAKorMK =
tryAddToFoldList(FoldList, MI, TryAK ? 3 : 2, OpToFold);
if (FoldAsFMAAKorMK) {
// Untie Src2 of fmac.
MI->untieRegOperand(3);
// For fmamk swap operands 1 and 2 if OpToFold was meant for operand 1.
if (OpNo == 1) {
MachineOperand &Op1 = MI->getOperand(1);
MachineOperand &Op2 = MI->getOperand(2);
Register OldReg = Op1.getReg();
// Operand 2 might be an inlinable constant
if (Op2.isImm()) {
Op1.ChangeToImmediate(Op2.getImm());
Op2.ChangeToRegister(OldReg, false);
} else {
Op1.setReg(Op2.getReg());
Op2.setReg(OldReg);
}
}
return true;
}
MI->setDesc(TII->get(Opc));
return false;
};
bool IsLegal = OpToFold.isOperandLegal(*TII, *MI, OpNo);
if (!IsLegal && OpToFold.isImm()) {
if (std::optional<int64_t> ImmVal = OpToFold.getEffectiveImmVal())
IsLegal = canUseImmWithOpSel(MI, OpNo, *ImmVal);
}
if (!IsLegal) {
// Special case for v_mac_{f16, f32}_e64 if we are trying to fold into src2
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 AddOpSel = !AMDGPU::hasNamedOperand(Opc, AMDGPU::OpName::op_sel) &&
AMDGPU::hasNamedOperand(NewOpc, AMDGPU::OpName::op_sel);
if (AddOpSel)
MI->addOperand(MachineOperand::CreateImm(0));
bool FoldAsMAD = tryAddToFoldList(FoldList, MI, OpNo, OpToFold);
if (FoldAsMAD) {
MI->untieRegOperand(OpNo);
return true;
}
if (AddOpSel)
MI->removeOperand(MI->getNumExplicitOperands() - 1);
MI->setDesc(TII->get(Opc));
}
// Special case for s_fmac_f32 if we are trying to fold into Src2.
// By transforming into fmaak we can untie Src2 and make folding legal.
if (Opc == AMDGPU::S_FMAC_F32 && OpNo == 3) {
if (tryToFoldAsFMAAKorMK())
return true;
}
// 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;
}
}
// Operand is not legal, so try to commute the instruction to
// see if this makes it possible to fold.
unsigned CommuteOpNo = TargetInstrInfo::CommuteAnyOperandIndex;
bool CanCommute = TII->findCommutedOpIndices(*MI, OpNo, CommuteOpNo);
if (!CanCommute)
return false;
MachineOperand &Op = MI->getOperand(OpNo);
MachineOperand &CommutedOp = MI->getOperand(CommuteOpNo);
// 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 (!Op.isReg() || !CommutedOp.isReg())
return false;
// The same situation with an immediate could reproduce if both inputs are
// the same register.
if (Op.isReg() && CommutedOp.isReg() &&
(Op.getReg() == CommutedOp.getReg() &&
Op.getSubReg() == CommutedOp.getSubReg()))
return false;
if (!TII->commuteInstruction(*MI, false, OpNo, CommuteOpNo))
return false;
int Op32 = -1;
if (!OpToFold.isOperandLegal(*TII, *MI, CommuteOpNo)) {
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())) {
TII->commuteInstruction(*MI, false, OpNo, CommuteOpNo);
return false;
}
// Verify the other operand is a VGPR, otherwise we would violate the
// constant bus restriction.
MachineOperand &OtherOp = MI->getOperand(OpNo);
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();
Op32 = AMDGPU::getVOPe32(MaybeCommutedOpc);
}
appendFoldCandidate(FoldList, MI, CommuteOpNo, OpToFold, /*Commuted=*/true,
Op32);
return true;
}
// Special case for s_fmac_f32 if we are trying to fold into Src0 or Src1.
// By changing into fmamk we can untie Src2.
// If folding for Src0 happens first and it is identical operand to Src1 we
// should avoid transforming into fmamk which requires commuting as it would
// cause folding into Src1 to fail later on due to wrong OpNo used.
if (Opc == AMDGPU::S_FMAC_F32 &&
(OpNo != 1 || !MI->getOperand(1).isIdenticalTo(MI->getOperand(2)))) {
if (tryToFoldAsFMAAKorMK())
return true;
}
appendFoldCandidate(FoldList, MI, OpNo, OpToFold);
return true;
}
bool SIFoldOperandsImpl::isUseSafeToFold(const MachineInstr &MI,
const MachineOperand &UseMO) const {
// Operands of SDWA instructions must be registers.
return !TII->isSDWA(MI);
}
static MachineOperand *lookUpCopyChain(const SIInstrInfo &TII,
const MachineRegisterInfo &MRI,
Register SrcReg) {
MachineOperand *Sub = nullptr;
for (MachineInstr *SubDef = MRI.getVRegDef(SrcReg);
SubDef && TII.isFoldableCopy(*SubDef);
SubDef = MRI.getVRegDef(Sub->getReg())) {
MachineOperand &SrcOp = SubDef->getOperand(1);
if (SrcOp.isImm())
return &SrcOp;
if (!SrcOp.isReg() || SrcOp.getReg().isPhysical())
break;
Sub = &SrcOp;
// TODO: Support compose
if (SrcOp.getSubReg())
break;
}
return Sub;
}
const TargetRegisterClass *SIFoldOperandsImpl::getRegSeqInit(
MachineInstr &RegSeq,
SmallVectorImpl<std::pair<MachineOperand *, unsigned>> &Defs) const {
assert(RegSeq.isRegSequence());
const TargetRegisterClass *RC = nullptr;
for (unsigned I = 1, E = RegSeq.getNumExplicitOperands(); I != E; I += 2) {
MachineOperand &SrcOp = RegSeq.getOperand(I);
unsigned SubRegIdx = RegSeq.getOperand(I + 1).getImm();
// Only accept reg_sequence with uniform reg class inputs for simplicity.
const TargetRegisterClass *OpRC = getRegOpRC(*MRI, *TRI, SrcOp);
if (!RC)
RC = OpRC;
else if (!TRI->getCommonSubClass(RC, OpRC))
return nullptr;
if (SrcOp.getSubReg()) {
// TODO: Handle subregister compose
Defs.emplace_back(&SrcOp, SubRegIdx);
continue;
}
MachineOperand *DefSrc = lookUpCopyChain(*TII, *MRI, SrcOp.getReg());
if (DefSrc && (DefSrc->isReg() || DefSrc->isImm())) {
Defs.emplace_back(DefSrc, SubRegIdx);
continue;
}
Defs.emplace_back(&SrcOp, SubRegIdx);
}
return RC;
}
// Find a def of the UseReg, check if it is a reg_sequence and find initializers
// for each subreg, tracking it to an immediate if possible. Returns the
// register class of the inputs on success.
const TargetRegisterClass *SIFoldOperandsImpl::getRegSeqInit(
SmallVectorImpl<std::pair<MachineOperand *, unsigned>> &Defs,
Register UseReg) const {
MachineInstr *Def = MRI->getVRegDef(UseReg);
if (!Def || !Def->isRegSequence())
return nullptr;
return getRegSeqInit(*Def, Defs);
}
std::pair<int64_t, const TargetRegisterClass *>
SIFoldOperandsImpl::isRegSeqSplat(MachineInstr &RegSeq) const {
SmallVector<std::pair<MachineOperand *, unsigned>, 32> Defs;
const TargetRegisterClass *SrcRC = getRegSeqInit(RegSeq, Defs);
if (!SrcRC)
return {};
bool TryToMatchSplat64 = false;
int64_t Imm;
for (unsigned I = 0, E = Defs.size(); I != E; ++I) {
const MachineOperand *Op = Defs[I].first;
if (!Op->isImm())
return {};
int64_t SubImm = Op->getImm();
if (!I) {
Imm = SubImm;
continue;
}
if (Imm != SubImm) {
if (I == 1 && (E & 1) == 0) {
// If we have an even number of inputs, there's a chance this is a
// 64-bit element splat broken into 32-bit pieces.
TryToMatchSplat64 = true;
break;
}
return {}; // Can only fold splat constants
}
}
if (!TryToMatchSplat64)
return {Defs[0].first->getImm(), SrcRC};
// Fallback to recognizing 64-bit splats broken into 32-bit pieces
// (i.e. recognize every other other element is 0 for 64-bit immediates)
int64_t SplatVal64;
for (unsigned I = 0, E = Defs.size(); I != E; I += 2) {
const MachineOperand *Op0 = Defs[I].first;
const MachineOperand *Op1 = Defs[I + 1].first;
if (!Op0->isImm() || !Op1->isImm())
return {};
unsigned SubReg0 = Defs[I].second;
unsigned SubReg1 = Defs[I + 1].second;
// Assume we're going to generally encounter reg_sequences with sorted
// subreg indexes, so reject any that aren't consecutive.
if (TRI->getChannelFromSubReg(SubReg0) + 1 !=
TRI->getChannelFromSubReg(SubReg1))
return {};
int64_t MergedVal = Make_64(Op1->getImm(), Op0->getImm());
if (I == 0)
SplatVal64 = MergedVal;
else if (SplatVal64 != MergedVal)
return {};
}
const TargetRegisterClass *RC64 = TRI->getSubRegisterClass(
MRI->getRegClass(RegSeq.getOperand(0).getReg()), AMDGPU::sub0_sub1);
return {SplatVal64, RC64};
}
bool SIFoldOperandsImpl::tryFoldRegSeqSplat(
MachineInstr *UseMI, unsigned UseOpIdx, int64_t SplatVal,
const TargetRegisterClass *SplatRC) const {
const MCInstrDesc &Desc = UseMI->getDesc();
if (UseOpIdx >= Desc.getNumOperands())
return false;
// Filter out unhandled pseudos.
if (!AMDGPU::isSISrcOperand(Desc, UseOpIdx))
return false;
int16_t RCID = Desc.operands()[UseOpIdx].RegClass;
if (RCID == -1)
return false;
const TargetRegisterClass *OpRC = TRI->getRegClass(RCID);
// Special case 0/-1, since when interpreted as a 64-bit element both halves
// have the same bits. These are the only cases where a splat has the same
// interpretation for 32-bit and 64-bit splats.
if (SplatVal != 0 && SplatVal != -1) {
// We need to figure out the scalar type read by the operand. e.g. the MFMA
// operand will be AReg_128, and we want to check if it's compatible with an
// AReg_32 constant.
uint8_t OpTy = Desc.operands()[UseOpIdx].OperandType;
switch (OpTy) {
case AMDGPU::OPERAND_REG_INLINE_AC_INT32:
case AMDGPU::OPERAND_REG_INLINE_AC_FP32:
OpRC = TRI->getSubRegisterClass(OpRC, AMDGPU::sub0);
break;
case AMDGPU::OPERAND_REG_INLINE_AC_FP64:
OpRC = TRI->getSubRegisterClass(OpRC, AMDGPU::sub0_sub1);
break;
default:
return false;
}
if (!TRI->getCommonSubClass(OpRC, SplatRC))
return false;
}
MachineOperand TmpOp = MachineOperand::CreateImm(SplatVal);
if (!TII->isOperandLegal(*UseMI, UseOpIdx, &TmpOp))
return false;
return true;
}
bool SIFoldOperandsImpl::tryToFoldACImm(
const FoldableDef &OpToFold, MachineInstr *UseMI, unsigned UseOpIdx,
SmallVectorImpl<FoldCandidate> &FoldList) const {
const MCInstrDesc &Desc = UseMI->getDesc();
if (UseOpIdx >= Desc.getNumOperands())
return false;
// Filter out unhandled pseudos.
if (!AMDGPU::isSISrcOperand(Desc, UseOpIdx))
return false;
MachineOperand &UseOp = UseMI->getOperand(UseOpIdx);
if (OpToFold.isImm() && OpToFold.isOperandLegal(*TII, *UseMI, UseOpIdx)) {
appendFoldCandidate(FoldList, UseMI, UseOpIdx, OpToFold);
return true;
}
// TODO: Verify the following code handles subregisters correctly.
// TODO: Handle extract of global reference
if (UseOp.getSubReg())
return false;
if (!OpToFold.isReg())
return false;
Register UseReg = OpToFold.getReg();
if (!UseReg.isVirtual())
return false;
// Maybe it is just a COPY of an immediate itself.
// FIXME: Remove this handling. There is already special case folding of
// immediate into copy in foldOperand. This is looking for the def of the
// value the folding started from in the first place.
MachineInstr *Def = MRI->getVRegDef(UseReg);
if (Def && TII->isFoldableCopy(*Def)) {
MachineOperand &DefOp = Def->getOperand(1);
if (DefOp.isImm() && TII->isOperandLegal(*UseMI, UseOpIdx, &DefOp)) {
FoldableDef FoldableImm(DefOp.getImm(), OpToFold.DefRC,
OpToFold.DefSubReg);
appendFoldCandidate(FoldList, UseMI, UseOpIdx, FoldableImm);
return true;
}
}
return false;
}
void SIFoldOperandsImpl::foldOperand(
FoldableDef OpToFold, MachineInstr *UseMI, int UseOpIdx,
SmallVectorImpl<FoldCandidate> &FoldList,
SmallVectorImpl<MachineInstr *> &CopiesToReplace) const {
const MachineOperand *UseOp = &UseMI->getOperand(UseOpIdx);
if (!isUseSafeToFold(*UseMI, *UseOp))
return;
// FIXME: Fold operands with subregs.
if (UseOp->isReg() && OpToFold.isReg()) {
if (UseOp->isImplicit())
return;
// Allow folding from SGPRs to 16-bit VGPRs.
if (UseOp->getSubReg() != AMDGPU::NoSubRegister &&
(UseOp->getSubReg() != AMDGPU::lo16 ||
!TRI->isSGPRReg(*MRI, OpToFold.getReg())))
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();
int64_t SplatVal;
const TargetRegisterClass *SplatRC;
std::tie(SplatVal, SplatRC) = isRegSeqSplat(*UseMI);
// Grab the use operands first
SmallVector<MachineOperand *, 4> UsesToProcess(
llvm::make_pointer_range(MRI->use_nodbg_operands(RegSeqDstReg)));
for (auto *RSUse : UsesToProcess) {
MachineInstr *RSUseMI = RSUse->getParent();
unsigned OpNo = RSUseMI->getOperandNo(RSUse);
if (SplatRC) {
if (tryFoldRegSeqSplat(RSUseMI, OpNo, SplatVal, SplatRC)) {
FoldableDef SplatDef(SplatVal, SplatRC);
appendFoldCandidate(FoldList, RSUseMI, OpNo, SplatDef);
continue;
}
}
// TODO: Handle general compose
if (RSUse->getSubReg() != RegSeqDstSubReg)
continue;
// FIXME: We should avoid recursing here. There should be a cleaner split
// between the in-place mutations and adding to the fold list.
foldOperand(OpToFold, RSUseMI, RSUseMI->getOperandNo(RSUse), FoldList,
CopiesToReplace);
}
return;
}
if (tryToFoldACImm(OpToFold, UseMI, UseOpIdx, FoldList))
return;
if (frameIndexMayFold(*UseMI, UseOpIdx, OpToFold)) {
// Verify 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.getFI());
const unsigned Opc = UseMI->getOpcode();
if (TII->isFLATScratch(*UseMI) &&
AMDGPU::hasNamedOperand(Opc, AMDGPU::OpName::vaddr) &&
!AMDGPU::hasNamedOperand(Opc, AMDGPU::OpName::saddr)) {
unsigned NewOpc = AMDGPU::getFlatScratchInstSSfromSV(Opc);
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 initializations.
if (DestReg.isPhysical() && SrcRC->contains(DestReg))
return;
const TargetRegisterClass *DestRC = TRI->getRegClassForReg(*MRI, DestReg);
if (!DestReg.isPhysical() && DestRC == &AMDGPU::AGPR_32RegClass) {
std::optional<int64_t> UseImmVal = OpToFold.getEffectiveImmVal();
if (UseImmVal && TII->isInlineConstant(
*UseImmVal, AMDGPU::OPERAND_REG_INLINE_C_INT32)) {
UseMI->setDesc(TII->get(AMDGPU::V_ACCVGPR_WRITE_B32_e64));
UseMI->getOperand(1).ChangeToImmediate(*UseImmVal);
CopiesToReplace.push_back(UseMI);
return;
}
}
// Allow immediates COPYd into sgpr_lo16 to be further folded while
// still being legal if not further folded
if (DestRC == &AMDGPU::SGPR_LO16RegClass) {
assert(ST->useRealTrue16Insts());
MRI->setRegClass(DestReg, &AMDGPU::SGPR_32RegClass);
DestRC = &AMDGPU::SGPR_32RegClass;
}
// 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;
// Fold if the destination register class of the MOV instruction (ResRC)
// is a superclass of (or equal to) the destination register class of the
// COPY (DestRC). If this condition fails, folding would be illegal.
const MCInstrDesc &MovDesc = TII->get(MovOp);
assert(MovDesc.getNumDefs() > 0 && MovDesc.operands()[0].RegClass != -1);
const TargetRegisterClass *ResRC =
TRI->getRegClass(MovDesc.operands()[0].RegClass);
if (!DestRC->hasSuperClassEq(ResRC))
return;
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));
}
UseMI->setDesc(TII->get(MovOp));
if (MovOp == AMDGPU::V_MOV_B16_t16_e64) {
const auto &SrcOp = UseMI->getOperand(UseOpIdx);
MachineOperand NewSrcOp(SrcOp);
MachineFunction *MF = UseMI->getParent()->getParent();
UseMI->removeOperand(1);
UseMI->addOperand(*MF, MachineOperand::CreateImm(0)); // src0_modifiers
UseMI->addOperand(NewSrcOp); // src0
UseMI->addOperand(*MF, MachineOperand::CreateImm(0)); // op_sel
UseOpIdx = 2;
UseOp = &UseMI->getOperand(UseOpIdx);
}
CopiesToReplace.push_back(UseMI);
} else {
if (UseMI->isCopy() && OpToFold.isReg() &&
UseMI->getOperand(0).getReg().isVirtual() &&
!UseMI->getOperand(1).getSubReg() &&
OpToFold.DefMI->implicit_operands().empty()) {
LLVM_DEBUG(dbgs() << "Folding " << OpToFold.OpToFold << "\n into "
<< *UseMI);
unsigned Size = TII->getOpSize(*UseMI, 1);
Register UseReg = OpToFold.getReg();
UseMI->getOperand(1).setReg(UseReg);
unsigned SubRegIdx = OpToFold.getSubReg();
// Hack to allow 32-bit SGPRs to be folded into True16 instructions
// Remove this if 16-bit SGPRs (i.e. SGPR_LO16) are added to the
// VS_16RegClass
//
// Excerpt from AMDGPUGenRegisterInfo.inc
// NoSubRegister, //0
// hi16, // 1
// lo16, // 2
// sub0, // 3
// ...
// sub1, // 11
// sub1_hi16, // 12
// sub1_lo16, // 13
static_assert(AMDGPU::sub1_hi16 == 12, "Subregister layout has changed");
if (Size == 2 && TRI->isVGPR(*MRI, UseMI->getOperand(0).getReg()) &&
TRI->isSGPRReg(*MRI, UseReg)) {
// Produce the 32 bit subregister index to which the 16-bit subregister
// is aligned.
if (SubRegIdx > AMDGPU::sub1) {
LaneBitmask M = TRI->getSubRegIndexLaneMask(SubRegIdx);
M |= M.getLane(M.getHighestLane() - 1);
SmallVector<unsigned, 4> Indexes;
TRI->getCoveringSubRegIndexes(TRI->getRegClassForReg(*MRI, UseReg), M,
Indexes);
assert(Indexes.size() == 1 && "Expected one 32-bit subreg to cover");
SubRegIdx = Indexes[0];
// 32-bit registers do not have a sub0 index
} else if (TII->getOpSize(*UseMI, 1) == 4)
SubRegIdx = 0;
else
SubRegIdx = AMDGPU::sub0;
}
UseMI->getOperand(1).setSubReg(SubRegIdx);
UseMI->getOperand(1).setIsKill(false);
CopiesToReplace.push_back(UseMI);
OpToFold.OpToFold->setIsKill(false);
// Remove kill flags as kills may now be out of order with uses.
MRI->clearKillFlags(UseReg);
if (foldCopyToAGPRRegSequence(UseMI))
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.DefMI, *UseMI))
return;
UseMI->setDesc(TII->get(AMDGPU::S_MOV_B32));
if (OpToFold.isImm()) {
UseMI->getOperand(1).ChangeToImmediate(
*OpToFold.getEffectiveImmVal());
} else if (OpToFold.isFI())
UseMI->getOperand(1).ChangeToFrameIndex(OpToFold.getFI());
else {
assert(OpToFold.isGlobal());
UseMI->getOperand(1).ChangeToGA(OpToFold.OpToFold->getGlobal(),
OpToFold.OpToFold->getOffset(),
OpToFold.OpToFold->getTargetFlags());
}
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.DefMI, *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.operands()[UseOpIdx].RegClass == -1)
return;
}
if (!FoldingImmLike) {
if (OpToFold.isReg() && ST->needsAlignedVGPRs()) {
// Don't fold if OpToFold doesn't hold an aligned register.
const TargetRegisterClass *RC =
TRI->getRegClassForReg(*MRI, OpToFold.getReg());
assert(RC);
if (TRI->hasVectorRegisters(RC) && OpToFold.getSubReg()) {
unsigned SubReg = OpToFold.getSubReg();
if (const TargetRegisterClass *SubRC =
TRI->getSubRegisterClass(RC, SubReg))
RC = SubRC;
}
if (!RC || !TRI->isProperlyAlignedRC(*RC))
return;
}
tryAddToFoldList(FoldList, UseMI, UseOpIdx, OpToFold);
// FIXME: We could try to change the instruction from 64-bit to 32-bit
// to enable more folding opportunities. The shrink operands pass
// already does this.
return;
}
tryAddToFoldList(FoldList, UseMI, UseOpIdx, OpToFold);
}
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<int32_t>(LHS) >> (RHS & 31);
return true;
case AMDGPU::V_ASHRREV_I32_e64:
case AMDGPU::V_ASHRREV_I32_e32:
Result = static_cast<int32_t>(RHS) >> (LHS & 31);
return true;
default:
return false;
}
}
static unsigned getMovOpc(bool IsScalar) {
return IsScalar ? AMDGPU::S_MOV_B32 : AMDGPU::V_MOV_B32_e32;
}
static void mutateCopyOp(MachineInstr &MI, const MCInstrDesc &NewDesc) {
MI.setDesc(NewDesc);
// 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.
const MCInstrDesc &Desc = MI.getDesc();
unsigned NumOps = Desc.getNumOperands() + Desc.implicit_uses().size() +
Desc.implicit_defs().size();
for (unsigned I = MI.getNumOperands() - 1; I >= NumOps; --I)
MI.removeOperand(I);
}
std::optional<int64_t>
SIFoldOperandsImpl::getImmOrMaterializedImm(MachineOperand &Op) const {
if (Op.isImm())
return Op.getImm();
if (!Op.isReg() || !Op.getReg().isVirtual())
return std::nullopt;
const MachineInstr *Def = MRI->getVRegDef(Op.getReg());
if (Def && Def->isMoveImmediate()) {
const MachineOperand &ImmSrc = Def->getOperand(1);
if (ImmSrc.isImm())
return TII->extractSubregFromImm(ImmSrc.getImm(), Op.getSubReg());
}
return std::nullopt;
}
// 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.
bool SIFoldOperandsImpl::tryConstantFoldOp(MachineInstr *MI) const {
if (!MI->allImplicitDefsAreDead())
return false;
unsigned Opc = MI->getOpcode();
int Src0Idx = AMDGPU::getNamedOperandIdx(Opc, AMDGPU::OpName::src0);
if (Src0Idx == -1)
return false;
MachineOperand *Src0 = &MI->getOperand(Src0Idx);
std::optional<int64_t> Src0Imm = getImmOrMaterializedImm(*Src0);
if ((Opc == AMDGPU::V_NOT_B32_e64 || Opc == AMDGPU::V_NOT_B32_e32 ||
Opc == AMDGPU::S_NOT_B32) &&
Src0Imm) {
MI->getOperand(1).ChangeToImmediate(~*Src0Imm);
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;
MachineOperand *Src1 = &MI->getOperand(Src1Idx);
std::optional<int64_t> Src1Imm = getImmOrMaterializedImm(*Src1);
if (!Src0Imm && !Src1Imm)
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 (Src0Imm && Src1Imm) {
int32_t NewImm;
if (!evalBinaryInstruction(Opc, NewImm, *Src0Imm, *Src1Imm))
return false;
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 (Src0Imm && !Src1Imm) {
std::swap(Src0, Src1);
std::swap(Src0Idx, Src1Idx);
std::swap(Src0Imm, Src1Imm);
}
int32_t Src1Val = static_cast<int32_t>(*Src1Imm);
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 (Opc == AMDGPU::V_AND_B32_e64 || Opc == AMDGPU::V_AND_B32_e32 ||
Opc == 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));
} else
return false;
return true;
}
if (Opc == AMDGPU::V_XOR_B32_e64 || Opc == AMDGPU::V_XOR_B32_e32 ||
Opc == 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
bool SIFoldOperandsImpl::tryFoldCndMask(MachineInstr &MI) const {
unsigned Opc = MI.getOpcode();
if (Opc != AMDGPU::V_CNDMASK_B32_e32 && Opc != AMDGPU::V_CNDMASK_B32_e64 &&
Opc != AMDGPU::V_CNDMASK_B64_PSEUDO)
return false;
MachineOperand *Src0 = TII->getNamedOperand(MI, AMDGPU::OpName::src0);
MachineOperand *Src1 = TII->getNamedOperand(MI, AMDGPU::OpName::src1);
if (!Src1->isIdenticalTo(*Src0)) {
std::optional<int64_t> Src1Imm = getImmOrMaterializedImm(*Src1);
if (!Src1Imm)
return false;
std::optional<int64_t> Src0Imm = getImmOrMaterializedImm(*Src0);
if (!Src0Imm || *Src0Imm != *Src1Imm)
return false;
}
int Src1ModIdx =
AMDGPU::getNamedOperandIdx(Opc, AMDGPU::OpName::src1_modifiers);
int Src0ModIdx =
AMDGPU::getNamedOperandIdx(Opc, AMDGPU::OpName::src0_modifiers);
if ((Src1ModIdx != -1 && MI.getOperand(Src1ModIdx).getImm() != 0) ||
(Src0ModIdx != -1 && MI.getOperand(Src0ModIdx).getImm() != 0))
return false;
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);
return true;
}
bool SIFoldOperandsImpl::tryFoldZeroHighBits(MachineInstr &MI) const {
if (MI.getOpcode() != AMDGPU::V_AND_B32_e64 &&
MI.getOpcode() != AMDGPU::V_AND_B32_e32)
return false;
std::optional<int64_t> Src0Imm = getImmOrMaterializedImm(MI.getOperand(1));
if (!Src0Imm || *Src0Imm != 0xffff || !MI.getOperand(2).isReg())
return false;
Register Src1 = MI.getOperand(2).getReg();
MachineInstr *SrcDef = MRI->getVRegDef(Src1);
if (!ST->zeroesHigh16BitsOfDest(SrcDef->getOpcode()))
return false;
Register Dst = MI.getOperand(0).getReg();
MRI->replaceRegWith(Dst, Src1);
if (!MI.getOperand(2).isKill())
MRI->clearKillFlags(Src1);
MI.eraseFromParent();
return true;
}
bool SIFoldOperandsImpl::foldInstOperand(MachineInstr &MI,
const FoldableDef &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<MachineInstr *, 4> CopiesToReplace;
SmallVector<FoldCandidate, 4> FoldList;
MachineOperand &Dst = MI.getOperand(0);
bool Changed = false;
if (OpToFold.isImm()) {
for (auto &UseMI :
make_early_inc_range(MRI->use_nodbg_instructions(Dst.getReg()))) {
// 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 (tryConstantFoldOp(&UseMI)) {
LLVM_DEBUG(dbgs() << "Constant folded " << UseMI);
Changed = true;
}
}
}
SmallVector<MachineOperand *, 4> UsesToProcess(
llvm::make_pointer_range(MRI->use_nodbg_operands(Dst.getReg())));
for (auto *U : UsesToProcess) {
MachineInstr *UseMI = U->getParent();
FoldableDef SubOpToFold = OpToFold.getWithSubReg(*TRI, U->getSubReg());
foldOperand(SubOpToFold, UseMI, UseMI->getOperandNo(U), FoldList,
CopiesToReplace);
}
if (CopiesToReplace.empty() && FoldList.empty())
return Changed;
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);
for (FoldCandidate &Fold : FoldList) {
assert(!Fold.isReg() || Fold.Def.OpToFold);
if (Fold.isReg() && Fold.getReg().isVirtual()) {
Register Reg = Fold.getReg();
const MachineInstr *DefMI = Fold.Def.DefMI;
if (DefMI->readsRegister(AMDGPU::EXEC, TRI) &&
execMayBeModifiedBeforeUse(*MRI, Reg, *DefMI, *Fold.UseMI))
continue;
}
if (updateOperand(Fold)) {
// Clear kill flags.
if (Fold.isReg()) {
assert(Fold.Def.OpToFold && Fold.isReg());
// FIXME: Probably shouldn't bother trying to fold if not an
// SGPR. PeepholeOptimizer can eliminate redundant VGPR->VGPR
// copies.
MRI->clearKillFlags(Fold.getReg());
}
LLVM_DEBUG(dbgs() << "Folded source from " << MI << " into OpNo "
<< static_cast<int>(Fold.UseOpNo) << " of "
<< *Fold.UseMI);
if (Fold.isImm() && tryConstantFoldOp(Fold.UseMI)) {
LLVM_DEBUG(dbgs() << "Constant folded " << *Fold.UseMI);
Changed = true;
}
} else if (Fold.Commuted) {
// Restoring instruction's original operand order if fold has failed.
TII->commuteInstruction(*Fold.UseMI, false);
}
}
return true;
}
/// Fold %agpr = COPY (REG_SEQUENCE x_MOV_B32, ...) into REG_SEQUENCE
/// (V_ACCVGPR_WRITE_B32_e64) ... depending on the reg_sequence input values.
bool SIFoldOperandsImpl::foldCopyToAGPRRegSequence(MachineInstr *CopyMI) const {
// It 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.
const TargetRegisterClass *DefRC =
MRI->getRegClass(CopyMI->getOperand(0).getReg());
if (!TRI->isAGPRClass(DefRC))
return false;
Register UseReg = CopyMI->getOperand(1).getReg();
MachineInstr *RegSeq = MRI->getVRegDef(UseReg);
if (!RegSeq || !RegSeq->isRegSequence())
return false;
const DebugLoc &DL = CopyMI->getDebugLoc();
MachineBasicBlock &MBB = *CopyMI->getParent();
MachineInstrBuilder B(*MBB.getParent(), CopyMI);
DenseMap<TargetInstrInfo::RegSubRegPair, Register> VGPRCopies;
const TargetRegisterClass *UseRC =
MRI->getRegClass(CopyMI->getOperand(1).getReg());
// Value, subregindex for new REG_SEQUENCE
SmallVector<std::pair<MachineOperand *, unsigned>, 32> NewDefs;
unsigned NumRegSeqOperands = RegSeq->getNumOperands();
unsigned NumFoldable = 0;
for (unsigned I = 1; I != NumRegSeqOperands; I += 2) {
MachineOperand &RegOp = RegSeq->getOperand(I);
unsigned SubRegIdx = RegSeq->getOperand(I + 1).getImm();
if (RegOp.getSubReg()) {
// TODO: Handle subregister compose
NewDefs.emplace_back(&RegOp, SubRegIdx);
continue;
}
MachineOperand *Lookup = lookUpCopyChain(*TII, *MRI, RegOp.getReg());
if (!Lookup)
Lookup = &RegOp;
if (Lookup->isImm()) {
// Check if this is an agpr_32 subregister.
const TargetRegisterClass *DestSuperRC = TRI->getMatchingSuperRegClass(
DefRC, &AMDGPU::AGPR_32RegClass, SubRegIdx);
if (DestSuperRC &&
TII->isInlineConstant(*Lookup, AMDGPU::OPERAND_REG_INLINE_C_INT32)) {
++NumFoldable;
NewDefs.emplace_back(Lookup, SubRegIdx);
continue;
}
}
const TargetRegisterClass *InputRC =
Lookup->isReg() ? MRI->getRegClass(Lookup->getReg())
: MRI->getRegClass(RegOp.getReg());
// TODO: Account for Lookup->getSubReg()
// If we can't find a matching super class, this is an SGPR->AGPR or
// VGPR->AGPR subreg copy (or something constant-like we have to materialize
// in the AGPR). We can't directly copy from SGPR to AGPR on gfx908, so we
// want to rewrite to copy to an intermediate VGPR class.
const TargetRegisterClass *MatchRC =
TRI->getMatchingSuperRegClass(DefRC, InputRC, SubRegIdx);
if (!MatchRC) {
++NumFoldable;
NewDefs.emplace_back(&RegOp, SubRegIdx);
continue;
}
NewDefs.emplace_back(&RegOp, SubRegIdx);
}
// Do not clone a reg_sequence and merely change the result register class.
if (NumFoldable == 0)
return false;
CopyMI->setDesc(TII->get(AMDGPU::REG_SEQUENCE));
for (unsigned I = CopyMI->getNumOperands() - 1; I > 0; --I)
CopyMI->removeOperand(I);
for (auto [Def, DestSubIdx] : NewDefs) {
if (!Def->isReg()) {
// TODO: Should we use single write for each repeated value like in
// register case?
Register Tmp = MRI->createVirtualRegister(&AMDGPU::AGPR_32RegClass);
BuildMI(MBB, CopyMI, DL, TII->get(AMDGPU::V_ACCVGPR_WRITE_B32_e64), Tmp)
.add(*Def);
B.addReg(Tmp);
} else {
TargetInstrInfo::RegSubRegPair Src = getRegSubRegPair(*Def);
Def->setIsKill(false);
Register &VGPRCopy = VGPRCopies[Src];
if (!VGPRCopy) {
const TargetRegisterClass *VGPRUseSubRC =
TRI->getSubRegisterClass(UseRC, DestSubIdx);
// 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.
// Direct copy from SGPR to AGPR is not possible on gfx908. 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->getSubRegisterClass(MRI->getRegClass(Src.Reg), Src.SubReg) !=
VGPRUseSubRC) {
VGPRCopy = MRI->createVirtualRegister(VGPRUseSubRC);
BuildMI(MBB, CopyMI, DL, TII->get(AMDGPU::COPY), VGPRCopy).add(*Def);
B.addReg(VGPRCopy);
} else {
// If it is already a VGPR, do not copy the register.
B.add(*Def);
}
} else {
B.addReg(VGPRCopy);
}
}
B.addImm(DestSubIdx);
}
LLVM_DEBUG(dbgs() << "Folded " << *CopyMI);
return true;
}
bool SIFoldOperandsImpl::tryFoldFoldableCopy(
MachineInstr &MI, MachineOperand *&CurrentKnownM0Val) const {
Register DstReg = MI.getOperand(0).getReg();
// Specially track simple redefs of m0 to the same value in a block, so we
// can erase the later ones.
if (DstReg == AMDGPU::M0) {
MachineOperand &NewM0Val = MI.getOperand(1);
if (CurrentKnownM0Val && CurrentKnownM0Val->isIdenticalTo(NewM0Val)) {
MI.eraseFromParent();
return true;
}
// We aren't tracking other physical registers
CurrentKnownM0Val = (NewM0Val.isReg() && NewM0Val.getReg().isPhysical())
? nullptr
: &NewM0Val;
return false;
}
MachineOperand *OpToFoldPtr;
if (MI.getOpcode() == AMDGPU::V_MOV_B16_t16_e64) {
// Folding when any src_modifiers are non-zero is unsupported
if (TII->hasAnyModifiersSet(MI))
return false;
OpToFoldPtr = &MI.getOperand(2);
} else
OpToFoldPtr = &MI.getOperand(1);
MachineOperand &OpToFold = *OpToFoldPtr;
bool FoldingImm = OpToFold.isImm() || OpToFold.isFI() || OpToFold.isGlobal();
// FIXME: We could also be folding things like TargetIndexes.
if (!FoldingImm && !OpToFold.isReg())
return false;
if (OpToFold.isReg() && !OpToFold.getReg().isVirtual())
return false;
// 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
if (!DstReg.isVirtual())
return false;
const TargetRegisterClass *DstRC =
MRI->getRegClass(MI.getOperand(0).getReg());
// True16: Fix malformed 16-bit sgpr COPY produced by peephole-opt
// Can remove this code if proper 16-bit SGPRs are implemented
// Example: Pre-peephole-opt
// %29:sgpr_lo16 = COPY %16.lo16:sreg_32
// %32:sreg_32 = COPY %29:sgpr_lo16
// %30:sreg_32 = S_PACK_LL_B32_B16 killed %31:sreg_32, killed %32:sreg_32
// Post-peephole-opt and DCE
// %32:sreg_32 = COPY %16.lo16:sreg_32
// %30:sreg_32 = S_PACK_LL_B32_B16 killed %31:sreg_32, killed %32:sreg_32
// After this transform
// %32:sreg_32 = COPY %16:sreg_32
// %30:sreg_32 = S_PACK_LL_B32_B16 killed %31:sreg_32, killed %32:sreg_32
// After the fold operands pass
// %30:sreg_32 = S_PACK_LL_B32_B16 killed %31:sreg_32, killed %16:sreg_32
if (MI.getOpcode() == AMDGPU::COPY && OpToFold.isReg() &&
OpToFold.getSubReg()) {
if (DstRC == &AMDGPU::SReg_32RegClass &&
DstRC == MRI->getRegClass(OpToFold.getReg())) {
assert(OpToFold.getSubReg() == AMDGPU::lo16);
OpToFold.setSubReg(0);
}
}
// Fold copy to AGPR through reg_sequence
// TODO: Handle with subregister extract
if (OpToFold.isReg() && MI.isCopy() && !MI.getOperand(1).getSubReg()) {
if (foldCopyToAGPRRegSequence(&MI))
return true;
}
FoldableDef Def(OpToFold, DstRC);
bool Changed = foldInstOperand(MI, Def);
// If we managed to fold all uses of this copy then we might as well
// delete it now.
// The only reason we need to follow chains of copies here is that
// tryFoldRegSequence looks forward through copies before folding a
// REG_SEQUENCE into its eventual users.
auto *InstToErase = &MI;
while (MRI->use_nodbg_empty(InstToErase->getOperand(0).getReg())) {
auto &SrcOp = InstToErase->getOperand(1);
auto SrcReg = SrcOp.isReg() ? SrcOp.getReg() : Register();
InstToErase->eraseFromParent();
Changed = true;
InstToErase = nullptr;
if (!SrcReg || SrcReg.isPhysical())
break;
InstToErase = MRI->getVRegDef(SrcReg);
if (!InstToErase || !TII->isFoldableCopy(*InstToErase))
break;
}
if (InstToErase && InstToErase->isRegSequence() &&
MRI->use_nodbg_empty(InstToErase->getOperand(0).getReg())) {
InstToErase->eraseFromParent();
Changed = true;
}
if (Changed)
return true;
// Run this after foldInstOperand to avoid turning scalar additions into
// vector additions when the result scalar result could just be folded into
// the user(s).
return OpToFold.isReg() &&
foldCopyToVGPROfScalarAddOfFrameIndex(DstReg, OpToFold.getReg(), MI);
}
// Clamp patterns are canonically selected to v_max_* instructions, so only
// handle them.
const MachineOperand *
SIFoldOperandsImpl::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_F16_t16_e64:
case AMDGPU::V_MAX_F16_fake16_e64:
case AMDGPU::V_MAX_F64_e64:
case AMDGPU::V_MAX_NUM_F64_e64:
case AMDGPU::V_PK_MAX_F16: {
if (MI.mayRaiseFPException())
return nullptr;
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;
}
}
// FIXME: Clamp for v_mad_mixhi_f16 handled during isel.
bool SIFoldOperandsImpl::tryFoldClamp(MachineInstr &MI) {
const MachineOperand *ClampSrc = isClamp(MI);
if (!ClampSrc || !MRI->hasOneNonDBGUser(ClampSrc->getReg()))
return false;
if (!ClampSrc->getReg().isVirtual())
return false;
// Look through COPY. COPY only observed with True16.
Register DefSrcReg = TRI->lookThruCopyLike(ClampSrc->getReg(), MRI);
MachineInstr *Def =
MRI->getVRegDef(DefSrcReg.isVirtual() ? DefSrcReg : ClampSrc->getReg());
// The type of clamp must be compatible.
if (TII->getClampMask(*Def) != TII->getClampMask(MI))
return false;
if (Def->mayRaiseFPException())
return false;
MachineOperand *DefClamp = TII->getNamedOperand(*Def, AMDGPU::OpName::clamp);
if (!DefClamp)
return false;
LLVM_DEBUG(dbgs() << "Folding clamp " << *DefClamp << " into " << *Def);
// Clamp is applied after omod, so it is OK if omod is set.
DefClamp->setImm(1);
Register DefReg = Def->getOperand(0).getReg();
Register MIDstReg = MI.getOperand(0).getReg();
if (TRI->isSGPRReg(*MRI, DefReg)) {
// Pseudo scalar instructions have a SGPR for dst and clamp is a v_max*
// instruction with a VGPR dst.
BuildMI(*MI.getParent(), MI, MI.getDebugLoc(), TII->get(AMDGPU::COPY),
MIDstReg)
.addReg(DefReg);
} else {
MRI->replaceRegWith(MIDstReg, DefReg);
}
MI.eraseFromParent();
// Use of output modifiers forces VOP3 encoding for a VOP2 mac/fmac
// instruction, so we might as well convert it to the more flexible VOP3-only
// mad/fma form.
if (TII->convertToThreeAddress(*Def, nullptr, nullptr))
Def->eraseFromParent();
return true;
}
static int getOModValue(unsigned Opc, int64_t Val) {
switch (Opc) {
case AMDGPU::V_MUL_F64_e64:
case AMDGPU::V_MUL_F64_pseudo_e64: {
switch (Val) {
case 0x3fe0000000000000: // 0.5
return SIOutMods::DIV2;
case 0x4000000000000000: // 2.0
return SIOutMods::MUL2;
case 0x4010000000000000: // 4.0
return SIOutMods::MUL4;
default:
return SIOutMods::NONE;
}
}
case AMDGPU::V_MUL_F32_e64: {
switch (static_cast<uint32_t>(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:
case AMDGPU::V_MUL_F16_t16_e64:
case AMDGPU::V_MUL_F16_fake16_e64: {
switch (static_cast<uint16_t>(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<const MachineOperand *, int>
SIFoldOperandsImpl::isOMod(const MachineInstr &MI) const {
unsigned Op = MI.getOpcode();
switch (Op) {
case AMDGPU::V_MUL_F64_e64:
case AMDGPU::V_MUL_F64_pseudo_e64:
case AMDGPU::V_MUL_F32_e64:
case AMDGPU::V_MUL_F16_t16_e64:
case AMDGPU::V_MUL_F16_fake16_e64:
case AMDGPU::V_MUL_F16_e64: {
// If output denormals are enabled, omod is ignored.
if ((Op == AMDGPU::V_MUL_F32_e64 &&
MFI->getMode().FP32Denormals.Output != DenormalMode::PreserveSign) ||
((Op == AMDGPU::V_MUL_F64_e64 || Op == AMDGPU::V_MUL_F64_pseudo_e64 ||
Op == AMDGPU::V_MUL_F16_e64 || Op == AMDGPU::V_MUL_F16_t16_e64 ||
Op == AMDGPU::V_MUL_F16_fake16_e64) &&
MFI->getMode().FP64FP16Denormals.Output !=
DenormalMode::PreserveSign) ||
MI.mayRaiseFPException())
return std::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::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::pair(nullptr, SIOutMods::NONE);
return std::pair(RegOp, OMod);
}
case AMDGPU::V_ADD_F64_e64:
case AMDGPU::V_ADD_F64_pseudo_e64:
case AMDGPU::V_ADD_F32_e64:
case AMDGPU::V_ADD_F16_e64:
case AMDGPU::V_ADD_F16_t16_e64:
case AMDGPU::V_ADD_F16_fake16_e64: {
// If output denormals are enabled, omod is ignored.
if ((Op == AMDGPU::V_ADD_F32_e64 &&
MFI->getMode().FP32Denormals.Output != DenormalMode::PreserveSign) ||
((Op == AMDGPU::V_ADD_F64_e64 || Op == AMDGPU::V_ADD_F64_pseudo_e64 ||
Op == AMDGPU::V_ADD_F16_e64 || Op == AMDGPU::V_ADD_F16_t16_e64 ||
Op == AMDGPU::V_ADD_F16_fake16_e64) &&
MFI->getMode().FP64FP16Denormals.Output != DenormalMode::PreserveSign))
return std::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::pair(Src0, SIOutMods::MUL2);
return std::pair(nullptr, SIOutMods::NONE);
}
default:
return std::pair(nullptr, SIOutMods::NONE);
}
}
// FIXME: Does this need to check IEEE bit on function?
bool SIFoldOperandsImpl::tryFoldOMod(MachineInstr &MI) {
const MachineOperand *RegOp;
int OMod;
std::tie(RegOp, OMod) = isOMod(MI);
if (OMod == SIOutMods::NONE || !RegOp->isReg() ||
RegOp->getSubReg() != AMDGPU::NoSubRegister ||
!MRI->hasOneNonDBGUser(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;
if (Def->mayRaiseFPException())
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);
DefOMod->setImm(OMod);
MRI->replaceRegWith(MI.getOperand(0).getReg(), Def->getOperand(0).getReg());
// Kill flags can be wrong if we replaced a def inside a loop with a def
// outside the loop.
MRI->clearKillFlags(Def->getOperand(0).getReg());
MI.eraseFromParent();
// Use of output modifiers forces VOP3 encoding for a VOP2 mac/fmac
// instruction, so we might as well convert it to the more flexible VOP3-only
// mad/fma form.
if (TII->convertToThreeAddress(*Def, nullptr, nullptr))
Def->eraseFromParent();
return true;
}
// Try to fold a reg_sequence with vgpr output and agpr inputs into an
// instruction which can take an agpr. So far that means a store.
bool SIFoldOperandsImpl::tryFoldRegSequence(MachineInstr &MI) {
assert(MI.isRegSequence());
auto Reg = MI.getOperand(0).getReg();
if (!ST->hasGFX90AInsts() || !TRI->isVGPR(*MRI, Reg) ||
!MRI->hasOneNonDBGUse(Reg))
return false;
SmallVector<std::pair<MachineOperand*, unsigned>, 32> Defs;
if (!getRegSeqInit(Defs, Reg))
return false;
for (auto &[Op, SubIdx] : Defs) {
if (!Op->isReg())
return false;
if (TRI->isAGPR(*MRI, Op->getReg()))
continue;
// Maybe this is a COPY from AREG
const MachineInstr *SubDef = MRI->getVRegDef(Op->getReg());
if (!SubDef || !SubDef->isCopy() || SubDef->getOperand(1).getSubReg())
return false;
if (!TRI->isAGPR(*MRI, SubDef->getOperand(1).getReg()))
return false;
}
MachineOperand *Op = &*MRI->use_nodbg_begin(Reg);
MachineInstr *UseMI = Op->getParent();
while (UseMI->isCopy() && !Op->getSubReg()) {
Reg = UseMI->getOperand(0).getReg();
if (!TRI->isVGPR(*MRI, Reg) || !MRI->hasOneNonDBGUse(Reg))
return false;
Op = &*MRI->use_nodbg_begin(Reg);
UseMI = Op->getParent();
}
if (Op->getSubReg())
return false;
unsigned OpIdx = Op - &UseMI->getOperand(0);
const MCInstrDesc &InstDesc = UseMI->getDesc();
const TargetRegisterClass *OpRC =
TII->getRegClass(InstDesc, OpIdx, TRI, *MI.getMF());
if (!OpRC || !TRI->isVectorSuperClass(OpRC))
return false;
const auto *NewDstRC = TRI->getEquivalentAGPRClass(MRI->getRegClass(Reg));
auto Dst = MRI->createVirtualRegister(NewDstRC);
auto RS = BuildMI(*MI.getParent(), MI, MI.getDebugLoc(),
TII->get(AMDGPU::REG_SEQUENCE), Dst);
for (auto &[Def, SubIdx] : Defs) {
Def->setIsKill(false);
if (TRI->isAGPR(*MRI, Def->getReg())) {
RS.add(*Def);
} else { // This is a copy
MachineInstr *SubDef = MRI->getVRegDef(Def->getReg());
SubDef->getOperand(1).setIsKill(false);
RS.addReg(SubDef->getOperand(1).getReg(), 0, Def->getSubReg());
}
RS.addImm(SubIdx);
}
Op->setReg(Dst);
if (!TII->isOperandLegal(*UseMI, OpIdx, Op)) {
Op->setReg(Reg);
RS->eraseFromParent();
return false;
}
LLVM_DEBUG(dbgs() << "Folded " << *RS << " into " << *UseMI);
// Erase the REG_SEQUENCE eagerly, unless we followed a chain of COPY users,
// in which case we can erase them all later in runOnMachineFunction.
if (MRI->use_nodbg_empty(MI.getOperand(0).getReg()))
MI.eraseFromParent();
return true;
}
/// Checks whether \p Copy is a AGPR -> VGPR copy. Returns `true` on success and
/// stores the AGPR register in \p OutReg and the subreg in \p OutSubReg
static bool isAGPRCopy(const SIRegisterInfo &TRI,
const MachineRegisterInfo &MRI, const MachineInstr &Copy,
Register &OutReg, unsigned &OutSubReg) {
assert(Copy.isCopy());
const MachineOperand &CopySrc = Copy.getOperand(1);
Register CopySrcReg = CopySrc.getReg();
if (!CopySrcReg.isVirtual())
return false;
// Common case: copy from AGPR directly, e.g.
// %1:vgpr_32 = COPY %0:agpr_32
if (TRI.isAGPR(MRI, CopySrcReg)) {
OutReg = CopySrcReg;
OutSubReg = CopySrc.getSubReg();
return true;
}
// Sometimes it can also involve two copies, e.g.
// %1:vgpr_256 = COPY %0:agpr_256
// %2:vgpr_32 = COPY %1:vgpr_256.sub0
const MachineInstr *CopySrcDef = MRI.getVRegDef(CopySrcReg);
if (!CopySrcDef || !CopySrcDef->isCopy())
return false;
const MachineOperand &OtherCopySrc = CopySrcDef->getOperand(1);
Register OtherCopySrcReg = OtherCopySrc.getReg();
if (!OtherCopySrcReg.isVirtual() ||
CopySrcDef->getOperand(0).getSubReg() != AMDGPU::NoSubRegister ||
OtherCopySrc.getSubReg() != AMDGPU::NoSubRegister ||
!TRI.isAGPR(MRI, OtherCopySrcReg))
return false;
OutReg = OtherCopySrcReg;
OutSubReg = CopySrc.getSubReg();
return true;
}
// Try to hoist an AGPR to VGPR copy across a PHI.
// This should allow folding of an AGPR into a consumer which may support it.
//
// Example 1: LCSSA PHI
// loop:
// %1:vreg = COPY %0:areg
// exit:
// %2:vreg = PHI %1:vreg, %loop
// =>
// loop:
// exit:
// %1:areg = PHI %0:areg, %loop
// %2:vreg = COPY %1:areg
//
// Example 2: PHI with multiple incoming values:
// entry:
// %1:vreg = GLOBAL_LOAD(..)
// loop:
// %2:vreg = PHI %1:vreg, %entry, %5:vreg, %loop
// %3:areg = COPY %2:vreg
// %4:areg = (instr using %3:areg)
// %5:vreg = COPY %4:areg
// =>
// entry:
// %1:vreg = GLOBAL_LOAD(..)
// %2:areg = COPY %1:vreg
// loop:
// %3:areg = PHI %2:areg, %entry, %X:areg,
// %4:areg = (instr using %3:areg)
bool SIFoldOperandsImpl::tryFoldPhiAGPR(MachineInstr &PHI) {
assert(PHI.isPHI());
Register PhiOut = PHI.getOperand(0).getReg();
if (!TRI->isVGPR(*MRI, PhiOut))
return false;
// Iterate once over all incoming values of the PHI to check if this PHI is
// eligible, and determine the exact AGPR RC we'll target.
const TargetRegisterClass *ARC = nullptr;
for (unsigned K = 1; K < PHI.getNumExplicitOperands(); K += 2) {
MachineOperand &MO = PHI.getOperand(K);
MachineInstr *Copy = MRI->getVRegDef(MO.getReg());
if (!Copy || !Copy->isCopy())
continue;
Register AGPRSrc;
unsigned AGPRRegMask = AMDGPU::NoSubRegister;
if (!isAGPRCopy(*TRI, *MRI, *Copy, AGPRSrc, AGPRRegMask))
continue;
const TargetRegisterClass *CopyInRC = MRI->getRegClass(AGPRSrc);
if (const auto *SubRC = TRI->getSubRegisterClass(CopyInRC, AGPRRegMask))
CopyInRC = SubRC;
if (ARC && !ARC->hasSubClassEq(CopyInRC))
return false;
ARC = CopyInRC;
}
if (!ARC)
return false;
bool IsAGPR32 = (ARC == &AMDGPU::AGPR_32RegClass);
// Rewrite the PHI's incoming values to ARC.
LLVM_DEBUG(dbgs() << "Folding AGPR copies into: " << PHI);
for (unsigned K = 1; K < PHI.getNumExplicitOperands(); K += 2) {
MachineOperand &MO = PHI.getOperand(K);
Register Reg = MO.getReg();
MachineBasicBlock::iterator InsertPt;
MachineBasicBlock *InsertMBB = nullptr;
// Look at the def of Reg, ignoring all copies.
unsigned CopyOpc = AMDGPU::COPY;
if (MachineInstr *Def = MRI->getVRegDef(Reg)) {
// Look at pre-existing COPY instructions from ARC: Steal the operand. If
// the copy was single-use, it will be removed by DCE later.
if (Def->isCopy()) {
Register AGPRSrc;
unsigned AGPRSubReg = AMDGPU::NoSubRegister;
if (isAGPRCopy(*TRI, *MRI, *Def, AGPRSrc, AGPRSubReg)) {
MO.setReg(AGPRSrc);
MO.setSubReg(AGPRSubReg);
continue;
}
// If this is a multi-use SGPR -> VGPR copy, use V_ACCVGPR_WRITE on
// GFX908 directly instead of a COPY. Otherwise, SIFoldOperand may try
// to fold the sgpr -> vgpr -> agpr copy into a sgpr -> agpr copy which
// is unlikely to be profitable.
//
// Note that V_ACCVGPR_WRITE is only used for AGPR_32.
MachineOperand &CopyIn = Def->getOperand(1);
if (IsAGPR32 && !ST->hasGFX90AInsts() && !MRI->hasOneNonDBGUse(Reg) &&
TRI->isSGPRReg(*MRI, CopyIn.getReg()))
CopyOpc = AMDGPU::V_ACCVGPR_WRITE_B32_e64;
}
InsertMBB = Def->getParent();
InsertPt = InsertMBB->SkipPHIsLabelsAndDebug(++Def->getIterator());
} else {
InsertMBB = PHI.getOperand(MO.getOperandNo() + 1).getMBB();
InsertPt = InsertMBB->getFirstTerminator();
}
Register NewReg = MRI->createVirtualRegister(ARC);
MachineInstr *MI = BuildMI(*InsertMBB, InsertPt, PHI.getDebugLoc(),
TII->get(CopyOpc), NewReg)
.addReg(Reg);
MO.setReg(NewReg);
(void)MI;
LLVM_DEBUG(dbgs() << " Created COPY: " << *MI);
}
// Replace the PHI's result with a new register.
Register NewReg = MRI->createVirtualRegister(ARC);
PHI.getOperand(0).setReg(NewReg);
// COPY that new register back to the original PhiOut register. This COPY will
// usually be folded out later.
MachineBasicBlock *MBB = PHI.getParent();
BuildMI(*MBB, MBB->getFirstNonPHI(), PHI.getDebugLoc(),
TII->get(AMDGPU::COPY), PhiOut)
.addReg(NewReg);
LLVM_DEBUG(dbgs() << " Done: Folded " << PHI);
return true;
}
// Attempt to convert VGPR load to an AGPR load.
bool SIFoldOperandsImpl::tryFoldLoad(MachineInstr &MI) {
assert(MI.mayLoad());
if (!ST->hasGFX90AInsts() || MI.getNumExplicitDefs() != 1)
return false;
MachineOperand &Def = MI.getOperand(0);
if (!Def.isDef())
return false;
Register DefReg = Def.getReg();
if (DefReg.isPhysical() || !TRI->isVGPR(*MRI, DefReg))
return false;
SmallVector<const MachineInstr *, 8> Users(
llvm::make_pointer_range(MRI->use_nodbg_instructions(DefReg)));
SmallVector<Register, 8> MoveRegs;
if (Users.empty())
return false;
// Check that all uses a copy to an agpr or a reg_sequence producing an agpr.
while (!Users.empty()) {
const MachineInstr *I = Users.pop_back_val();
if (!I->isCopy() && !I->isRegSequence())
return false;
Register DstReg = I->getOperand(0).getReg();
// Physical registers may have more than one instruction definitions
if (DstReg.isPhysical())
return false;
if (TRI->isAGPR(*MRI, DstReg))
continue;
MoveRegs.push_back(DstReg);
for (const MachineInstr &U : MRI->use_nodbg_instructions(DstReg))
Users.push_back(&U);
}
const TargetRegisterClass *RC = MRI->getRegClass(DefReg);
MRI->setRegClass(DefReg, TRI->getEquivalentAGPRClass(RC));
if (!TII->isOperandLegal(MI, 0, &Def)) {
MRI->setRegClass(DefReg, RC);
return false;
}
while (!MoveRegs.empty()) {
Register Reg = MoveRegs.pop_back_val();
MRI->setRegClass(Reg, TRI->getEquivalentAGPRClass(MRI->getRegClass(Reg)));
}
LLVM_DEBUG(dbgs() << "Folded " << MI);
return true;
}
// tryFoldPhiAGPR will aggressively try to create AGPR PHIs.
// For GFX90A and later, this is pretty much always a good thing, but for GFX908
// there's cases where it can create a lot more AGPR-AGPR copies, which are
// expensive on this architecture due to the lack of V_ACCVGPR_MOV.
//
// This function looks at all AGPR PHIs in a basic block and collects their
// operands. Then, it checks for register that are used more than once across
// all PHIs and caches them in a VGPR. This prevents ExpandPostRAPseudo from
// having to create one VGPR temporary per use, which can get very messy if
// these PHIs come from a broken-up large PHI (e.g. 32 AGPR phis, one per vector
// element).
//
// Example
// a:
// %in:agpr_256 = COPY %foo:vgpr_256
// c:
// %x:agpr_32 = ..
// b:
// %0:areg = PHI %in.sub0:agpr_32, %a, %x, %c
// %1:areg = PHI %in.sub0:agpr_32, %a, %y, %c
// %2:areg = PHI %in.sub0:agpr_32, %a, %z, %c
// =>
// a:
// %in:agpr_256 = COPY %foo:vgpr_256
// %tmp:vgpr_32 = V_ACCVGPR_READ_B32_e64 %in.sub0:agpr_32
// %tmp_agpr:agpr_32 = COPY %tmp
// c:
// %x:agpr_32 = ..
// b:
// %0:areg = PHI %tmp_agpr, %a, %x, %c
// %1:areg = PHI %tmp_agpr, %a, %y, %c
// %2:areg = PHI %tmp_agpr, %a, %z, %c
bool SIFoldOperandsImpl::tryOptimizeAGPRPhis(MachineBasicBlock &MBB) {
// This is only really needed on GFX908 where AGPR-AGPR copies are
// unreasonably difficult.
if (ST->hasGFX90AInsts())
return false;
// Look at all AGPR Phis and collect the register + subregister used.
DenseMap<std::pair<Register, unsigned>, std::vector<MachineOperand *>>
RegToMO;
for (auto &MI : MBB) {
if (!MI.isPHI())
break;
if (!TRI->isAGPR(*MRI, MI.getOperand(0).getReg()))
continue;
for (unsigned K = 1; K < MI.getNumOperands(); K += 2) {
MachineOperand &PhiMO = MI.getOperand(K);
if (!PhiMO.getSubReg())
continue;
RegToMO[{PhiMO.getReg(), PhiMO.getSubReg()}].push_back(&PhiMO);
}
}
// For all (Reg, SubReg) pair that are used more than once, cache the value in
// a VGPR.
bool Changed = false;
for (const auto &[Entry, MOs] : RegToMO) {
if (MOs.size() == 1)
continue;
const auto [Reg, SubReg] = Entry;
MachineInstr *Def = MRI->getVRegDef(Reg);
MachineBasicBlock *DefMBB = Def->getParent();
// Create a copy in a VGPR using V_ACCVGPR_READ_B32_e64 so it's not folded
// out.
const TargetRegisterClass *ARC = getRegOpRC(*MRI, *TRI, *MOs.front());
Register TempVGPR =
MRI->createVirtualRegister(TRI->getEquivalentVGPRClass(ARC));
MachineInstr *VGPRCopy =
BuildMI(*DefMBB, ++Def->getIterator(), Def->getDebugLoc(),
TII->get(AMDGPU::V_ACCVGPR_READ_B32_e64), TempVGPR)
.addReg(Reg, /* flags */ 0, SubReg);
// Copy back to an AGPR and use that instead of the AGPR subreg in all MOs.
Register TempAGPR = MRI->createVirtualRegister(ARC);
BuildMI(*DefMBB, ++VGPRCopy->getIterator(), Def->getDebugLoc(),
TII->get(AMDGPU::COPY), TempAGPR)
.addReg(TempVGPR);
LLVM_DEBUG(dbgs() << "Caching AGPR into VGPR: " << *VGPRCopy);
for (MachineOperand *MO : MOs) {
MO->setReg(TempAGPR);
MO->setSubReg(AMDGPU::NoSubRegister);
LLVM_DEBUG(dbgs() << " Changed PHI Operand: " << *MO << "\n");
}
Changed = true;
}
return Changed;
}
bool SIFoldOperandsImpl::run(MachineFunction &MF) {
MRI = &MF.getRegInfo();
ST = &MF.getSubtarget<GCNSubtarget>();
TII = ST->getInstrInfo();
TRI = &TII->getRegisterInfo();
MFI = MF.getInfo<SIMachineFunctionInfo>();
// 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();
bool Changed = false;
for (MachineBasicBlock *MBB : depth_first(&MF)) {
MachineOperand *CurrentKnownM0Val = nullptr;
for (auto &MI : make_early_inc_range(*MBB)) {
Changed |= tryFoldCndMask(MI);
if (tryFoldZeroHighBits(MI)) {
Changed = true;
continue;
}
if (MI.isRegSequence() && tryFoldRegSequence(MI)) {
Changed = true;
continue;
}
if (MI.isPHI() && tryFoldPhiAGPR(MI)) {
Changed = true;
continue;
}
if (MI.mayLoad() && tryFoldLoad(MI)) {
Changed = true;
continue;
}
if (TII->isFoldableCopy(MI)) {
Changed |= tryFoldFoldableCopy(MI, CurrentKnownM0Val);
continue;
}
// 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))
Changed |= tryFoldClamp(MI);
}
Changed |= tryOptimizeAGPRPhis(*MBB);
}
return Changed;
}
PreservedAnalyses SIFoldOperandsPass::run(MachineFunction &MF,
MachineFunctionAnalysisManager &) {
MFPropsModifier _(*this, MF);
bool Changed = SIFoldOperandsImpl().run(MF);
if (!Changed) {
return PreservedAnalyses::all();
}
auto PA = getMachineFunctionPassPreservedAnalyses();
PA.preserveSet<CFGAnalyses>();
return PA;
}