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llvm-project/llvm/lib/Target/AMDGPU/SIShrinkInstructions.cpp

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//===-- SIShrinkInstructions.cpp - Shrink Instructions --------------------===//
//
// 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
//
/// The pass tries to use the 32-bit encoding for instructions when possible.
//===----------------------------------------------------------------------===//
//
#include "AMDGPU.h"
#include "GCNSubtarget.h"
#include "MCTargetDesc/AMDGPUMCTargetDesc.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#define DEBUG_TYPE "si-shrink-instructions"
STATISTIC(NumInstructionsShrunk,
"Number of 64-bit instruction reduced to 32-bit.");
STATISTIC(NumLiteralConstantsFolded,
"Number of literal constants folded into 32-bit instructions.");
using namespace llvm;
namespace {
class SIShrinkInstructions : public MachineFunctionPass {
public:
static char ID;
void shrinkMIMG(MachineInstr &MI);
public:
SIShrinkInstructions() : MachineFunctionPass(ID) {
}
bool runOnMachineFunction(MachineFunction &MF) override;
StringRef getPassName() const override { return "SI Shrink Instructions"; }
void getAnalysisUsage(AnalysisUsage &AU) const override {
AU.setPreservesCFG();
MachineFunctionPass::getAnalysisUsage(AU);
}
};
} // End anonymous namespace.
INITIALIZE_PASS(SIShrinkInstructions, DEBUG_TYPE,
"SI Shrink Instructions", false, false)
char SIShrinkInstructions::ID = 0;
FunctionPass *llvm::createSIShrinkInstructionsPass() {
return new SIShrinkInstructions();
}
/// This function checks \p MI for operands defined by a move immediate
/// instruction and then folds the literal constant into the instruction if it
/// can. This function assumes that \p MI is a VOP1, VOP2, or VOPC instructions.
static bool foldImmediates(MachineInstr &MI, const SIInstrInfo *TII,
MachineRegisterInfo &MRI, bool TryToCommute = true) {
assert(TII->isVOP1(MI) || TII->isVOP2(MI) || TII->isVOPC(MI));
int Src0Idx = AMDGPU::getNamedOperandIdx(MI.getOpcode(), AMDGPU::OpName::src0);
// Try to fold Src0
MachineOperand &Src0 = MI.getOperand(Src0Idx);
if (Src0.isReg()) {
Register Reg = Src0.getReg();
if (Reg.isVirtual() && MRI.hasOneUse(Reg)) {
MachineInstr *Def = MRI.getUniqueVRegDef(Reg);
if (Def && Def->isMoveImmediate()) {
MachineOperand &MovSrc = Def->getOperand(1);
bool ConstantFolded = false;
if (TII->isOperandLegal(MI, Src0Idx, &MovSrc)) {
if (MovSrc.isImm() &&
(isInt<32>(MovSrc.getImm()) || isUInt<32>(MovSrc.getImm()))) {
Src0.ChangeToImmediate(MovSrc.getImm());
ConstantFolded = true;
} else if (MovSrc.isFI()) {
Src0.ChangeToFrameIndex(MovSrc.getIndex());
ConstantFolded = true;
} else if (MovSrc.isGlobal()) {
Src0.ChangeToGA(MovSrc.getGlobal(), MovSrc.getOffset(),
MovSrc.getTargetFlags());
ConstantFolded = true;
}
}
if (ConstantFolded) {
assert(MRI.use_empty(Reg));
Def->eraseFromParent();
++NumLiteralConstantsFolded;
return true;
}
}
}
}
// We have failed to fold src0, so commute the instruction and try again.
if (TryToCommute && MI.isCommutable()) {
if (TII->commuteInstruction(MI)) {
if (foldImmediates(MI, TII, MRI, false))
return true;
// Commute back.
TII->commuteInstruction(MI);
}
}
return false;
}
static bool isKImmOperand(const SIInstrInfo *TII, const MachineOperand &Src) {
return isInt<16>(Src.getImm()) &&
!TII->isInlineConstant(*Src.getParent(),
Src.getParent()->getOperandNo(&Src));
}
static bool isKUImmOperand(const SIInstrInfo *TII, const MachineOperand &Src) {
return isUInt<16>(Src.getImm()) &&
!TII->isInlineConstant(*Src.getParent(),
Src.getParent()->getOperandNo(&Src));
}
static bool isKImmOrKUImmOperand(const SIInstrInfo *TII,
const MachineOperand &Src,
bool &IsUnsigned) {
if (isInt<16>(Src.getImm())) {
IsUnsigned = false;
return !TII->isInlineConstant(Src);
}
if (isUInt<16>(Src.getImm())) {
IsUnsigned = true;
return !TII->isInlineConstant(Src);
}
return false;
}
/// \returns true if the constant in \p Src should be replaced with a bitreverse
/// of an inline immediate.
static bool isReverseInlineImm(const SIInstrInfo *TII,
const MachineOperand &Src,
int32_t &ReverseImm) {
if (!isInt<32>(Src.getImm()) || TII->isInlineConstant(Src))
return false;
ReverseImm = reverseBits<int32_t>(static_cast<int32_t>(Src.getImm()));
return ReverseImm >= -16 && ReverseImm <= 64;
}
/// Copy implicit register operands from specified instruction to this
/// instruction that are not part of the instruction definition.
static void copyExtraImplicitOps(MachineInstr &NewMI, MachineFunction &MF,
const MachineInstr &MI) {
for (unsigned i = MI.getDesc().getNumOperands() +
MI.getDesc().getNumImplicitUses() +
MI.getDesc().getNumImplicitDefs(), e = MI.getNumOperands();
i != e; ++i) {
const MachineOperand &MO = MI.getOperand(i);
if ((MO.isReg() && MO.isImplicit()) || MO.isRegMask())
NewMI.addOperand(MF, MO);
}
}
static void shrinkScalarCompare(const SIInstrInfo *TII, MachineInstr &MI) {
// cmpk instructions do scc = dst <cc op> imm16, so commute the instruction to
// get constants on the RHS.
if (!MI.getOperand(0).isReg())
TII->commuteInstruction(MI, false, 0, 1);
// cmpk requires src0 to be a register
const MachineOperand &Src0 = MI.getOperand(0);
if (!Src0.isReg())
return;
const MachineOperand &Src1 = MI.getOperand(1);
if (!Src1.isImm())
return;
int SOPKOpc = AMDGPU::getSOPKOp(MI.getOpcode());
if (SOPKOpc == -1)
return;
// eq/ne is special because the imm16 can be treated as signed or unsigned,
// and initially selected to the unsigned versions.
if (SOPKOpc == AMDGPU::S_CMPK_EQ_U32 || SOPKOpc == AMDGPU::S_CMPK_LG_U32) {
bool HasUImm;
if (isKImmOrKUImmOperand(TII, Src1, HasUImm)) {
if (!HasUImm) {
SOPKOpc = (SOPKOpc == AMDGPU::S_CMPK_EQ_U32) ?
AMDGPU::S_CMPK_EQ_I32 : AMDGPU::S_CMPK_LG_I32;
}
MI.setDesc(TII->get(SOPKOpc));
}
return;
}
const MCInstrDesc &NewDesc = TII->get(SOPKOpc);
if ((TII->sopkIsZext(SOPKOpc) && isKUImmOperand(TII, Src1)) ||
(!TII->sopkIsZext(SOPKOpc) && isKImmOperand(TII, Src1))) {
MI.setDesc(NewDesc);
}
}
// Shrink NSA encoded instructions with contiguous VGPRs to non-NSA encoding.
void SIShrinkInstructions::shrinkMIMG(MachineInstr &MI) {
const AMDGPU::MIMGInfo *Info = AMDGPU::getMIMGInfo(MI.getOpcode());
if (!Info || Info->MIMGEncoding != AMDGPU::MIMGEncGfx10NSA)
return;
MachineFunction *MF = MI.getParent()->getParent();
const GCNSubtarget &ST = MF->getSubtarget<GCNSubtarget>();
const SIInstrInfo *TII = ST.getInstrInfo();
const SIRegisterInfo &TRI = TII->getRegisterInfo();
int VAddr0Idx =
AMDGPU::getNamedOperandIdx(MI.getOpcode(), AMDGPU::OpName::vaddr0);
unsigned NewAddrDwords = Info->VAddrDwords;
const TargetRegisterClass *RC;
if (Info->VAddrDwords == 2) {
RC = &AMDGPU::VReg_64RegClass;
} else if (Info->VAddrDwords == 3) {
RC = &AMDGPU::VReg_96RegClass;
} else if (Info->VAddrDwords == 4) {
RC = &AMDGPU::VReg_128RegClass;
} else if (Info->VAddrDwords == 5) {
RC = &AMDGPU::VReg_160RegClass;
} else if (Info->VAddrDwords == 6) {
RC = &AMDGPU::VReg_192RegClass;
} else if (Info->VAddrDwords == 7) {
RC = &AMDGPU::VReg_224RegClass;
} else if (Info->VAddrDwords == 8) {
RC = &AMDGPU::VReg_256RegClass;
} else {
RC = &AMDGPU::VReg_512RegClass;
NewAddrDwords = 16;
}
unsigned VgprBase = 0;
bool IsUndef = true;
bool IsKill = NewAddrDwords == Info->VAddrDwords;
for (unsigned i = 0; i < Info->VAddrDwords; ++i) {
const MachineOperand &Op = MI.getOperand(VAddr0Idx + i);
unsigned Vgpr = TRI.getHWRegIndex(Op.getReg());
if (i == 0) {
VgprBase = Vgpr;
} else if (VgprBase + i != Vgpr)
return;
if (!Op.isUndef())
IsUndef = false;
if (!Op.isKill())
IsKill = false;
}
if (VgprBase + NewAddrDwords > 256)
return;
// Further check for implicit tied operands - this may be present if TFE is
// enabled
int TFEIdx = AMDGPU::getNamedOperandIdx(MI.getOpcode(), AMDGPU::OpName::tfe);
int LWEIdx = AMDGPU::getNamedOperandIdx(MI.getOpcode(), AMDGPU::OpName::lwe);
unsigned TFEVal = (TFEIdx == -1) ? 0 : MI.getOperand(TFEIdx).getImm();
unsigned LWEVal = (LWEIdx == -1) ? 0 : MI.getOperand(LWEIdx).getImm();
int ToUntie = -1;
if (TFEVal || LWEVal) {
// TFE/LWE is enabled so we need to deal with an implicit tied operand
for (unsigned i = LWEIdx + 1, e = MI.getNumOperands(); i != e; ++i) {
if (MI.getOperand(i).isReg() && MI.getOperand(i).isTied() &&
MI.getOperand(i).isImplicit()) {
// This is the tied operand
assert(
ToUntie == -1 &&
"found more than one tied implicit operand when expecting only 1");
ToUntie = i;
MI.untieRegOperand(ToUntie);
}
}
}
unsigned NewOpcode =
AMDGPU::getMIMGOpcode(Info->BaseOpcode, AMDGPU::MIMGEncGfx10Default,
Info->VDataDwords, NewAddrDwords);
MI.setDesc(TII->get(NewOpcode));
MI.getOperand(VAddr0Idx).setReg(RC->getRegister(VgprBase));
MI.getOperand(VAddr0Idx).setIsUndef(IsUndef);
MI.getOperand(VAddr0Idx).setIsKill(IsKill);
for (unsigned i = 1; i < Info->VAddrDwords; ++i)
MI.RemoveOperand(VAddr0Idx + 1);
if (ToUntie >= 0) {
MI.tieOperands(
AMDGPU::getNamedOperandIdx(MI.getOpcode(), AMDGPU::OpName::vdata),
ToUntie - (Info->VAddrDwords - 1));
}
}
/// Attempt to shink AND/OR/XOR operations requiring non-inlineable literals.
/// For AND or OR, try using S_BITSET{0,1} to clear or set bits.
/// If the inverse of the immediate is legal, use ANDN2, ORN2 or
/// XNOR (as a ^ b == ~(a ^ ~b)).
/// \returns true if the caller should continue the machine function iterator
static bool shrinkScalarLogicOp(const GCNSubtarget &ST,
MachineRegisterInfo &MRI,
const SIInstrInfo *TII,
MachineInstr &MI) {
unsigned Opc = MI.getOpcode();
const MachineOperand *Dest = &MI.getOperand(0);
MachineOperand *Src0 = &MI.getOperand(1);
MachineOperand *Src1 = &MI.getOperand(2);
MachineOperand *SrcReg = Src0;
MachineOperand *SrcImm = Src1;
if (!SrcImm->isImm() ||
AMDGPU::isInlinableLiteral32(SrcImm->getImm(), ST.hasInv2PiInlineImm()))
return false;
uint32_t Imm = static_cast<uint32_t>(SrcImm->getImm());
uint32_t NewImm = 0;
if (Opc == AMDGPU::S_AND_B32) {
if (isPowerOf2_32(~Imm)) {
NewImm = countTrailingOnes(Imm);
Opc = AMDGPU::S_BITSET0_B32;
} else if (AMDGPU::isInlinableLiteral32(~Imm, ST.hasInv2PiInlineImm())) {
NewImm = ~Imm;
Opc = AMDGPU::S_ANDN2_B32;
}
} else if (Opc == AMDGPU::S_OR_B32) {
if (isPowerOf2_32(Imm)) {
NewImm = countTrailingZeros(Imm);
Opc = AMDGPU::S_BITSET1_B32;
} else if (AMDGPU::isInlinableLiteral32(~Imm, ST.hasInv2PiInlineImm())) {
NewImm = ~Imm;
Opc = AMDGPU::S_ORN2_B32;
}
} else if (Opc == AMDGPU::S_XOR_B32) {
if (AMDGPU::isInlinableLiteral32(~Imm, ST.hasInv2PiInlineImm())) {
NewImm = ~Imm;
Opc = AMDGPU::S_XNOR_B32;
}
} else {
llvm_unreachable("unexpected opcode");
}
if (NewImm != 0) {
if (Dest->getReg().isVirtual() && SrcReg->isReg()) {
MRI.setRegAllocationHint(Dest->getReg(), 0, SrcReg->getReg());
MRI.setRegAllocationHint(SrcReg->getReg(), 0, Dest->getReg());
return true;
}
if (SrcReg->isReg() && SrcReg->getReg() == Dest->getReg()) {
const bool IsUndef = SrcReg->isUndef();
const bool IsKill = SrcReg->isKill();
MI.setDesc(TII->get(Opc));
if (Opc == AMDGPU::S_BITSET0_B32 ||
Opc == AMDGPU::S_BITSET1_B32) {
Src0->ChangeToImmediate(NewImm);
// Remove the immediate and add the tied input.
MI.getOperand(2).ChangeToRegister(Dest->getReg(), /*IsDef*/ false,
/*isImp*/ false, IsKill,
/*isDead*/ false, IsUndef);
MI.tieOperands(0, 2);
} else {
SrcImm->setImm(NewImm);
}
}
}
return false;
}
// This is the same as MachineInstr::readsRegister/modifiesRegister except
// it takes subregs into account.
static bool instAccessReg(iterator_range<MachineInstr::const_mop_iterator> &&R,
Register Reg, unsigned SubReg,
const SIRegisterInfo &TRI) {
for (const MachineOperand &MO : R) {
if (!MO.isReg())
continue;
if (Reg.isPhysical() && MO.getReg().isPhysical()) {
if (TRI.regsOverlap(Reg, MO.getReg()))
return true;
} else if (MO.getReg() == Reg && Reg.isVirtual()) {
LaneBitmask Overlap = TRI.getSubRegIndexLaneMask(SubReg) &
TRI.getSubRegIndexLaneMask(MO.getSubReg());
if (Overlap.any())
return true;
}
}
return false;
}
static bool instReadsReg(const MachineInstr *MI,
unsigned Reg, unsigned SubReg,
const SIRegisterInfo &TRI) {
return instAccessReg(MI->uses(), Reg, SubReg, TRI);
}
static bool instModifiesReg(const MachineInstr *MI,
unsigned Reg, unsigned SubReg,
const SIRegisterInfo &TRI) {
return instAccessReg(MI->defs(), Reg, SubReg, TRI);
}
static TargetInstrInfo::RegSubRegPair
getSubRegForIndex(Register Reg, unsigned Sub, unsigned I,
const SIRegisterInfo &TRI, const MachineRegisterInfo &MRI) {
if (TRI.getRegSizeInBits(Reg, MRI) != 32) {
if (Reg.isPhysical()) {
Reg = TRI.getSubReg(Reg, TRI.getSubRegFromChannel(I));
} else {
Sub = TRI.getSubRegFromChannel(I + TRI.getChannelFromSubReg(Sub));
}
}
return TargetInstrInfo::RegSubRegPair(Reg, Sub);
}
static void dropInstructionKeepingImpDefs(MachineInstr &MI,
const SIInstrInfo *TII) {
for (unsigned i = MI.getDesc().getNumOperands() +
MI.getDesc().getNumImplicitUses() +
MI.getDesc().getNumImplicitDefs(), e = MI.getNumOperands();
i != e; ++i) {
const MachineOperand &Op = MI.getOperand(i);
if (!Op.isDef())
continue;
BuildMI(*MI.getParent(), MI.getIterator(), MI.getDebugLoc(),
TII->get(AMDGPU::IMPLICIT_DEF), Op.getReg());
}
MI.eraseFromParent();
}
// Match:
// mov t, x
// mov x, y
// mov y, t
//
// =>
//
// mov t, x (t is potentially dead and move eliminated)
// v_swap_b32 x, y
//
// Returns next valid instruction pointer if was able to create v_swap_b32.
//
// This shall not be done too early not to prevent possible folding which may
// remove matched moves, and this should prefereably be done before RA to
// release saved registers and also possibly after RA which can insert copies
// too.
//
// This is really just a generic peephole that is not a canocical shrinking,
// although requirements match the pass placement and it reduces code size too.
static MachineInstr* matchSwap(MachineInstr &MovT, MachineRegisterInfo &MRI,
const SIInstrInfo *TII) {
assert(MovT.getOpcode() == AMDGPU::V_MOV_B32_e32 ||
MovT.getOpcode() == AMDGPU::COPY);
Register T = MovT.getOperand(0).getReg();
unsigned Tsub = MovT.getOperand(0).getSubReg();
MachineOperand &Xop = MovT.getOperand(1);
if (!Xop.isReg())
return nullptr;
Register X = Xop.getReg();
unsigned Xsub = Xop.getSubReg();
unsigned Size = TII->getOpSize(MovT, 0) / 4;
const SIRegisterInfo &TRI = TII->getRegisterInfo();
if (!TRI.isVGPR(MRI, X))
return nullptr;
if (MovT.hasRegisterImplicitUseOperand(AMDGPU::M0))
return nullptr;
const unsigned SearchLimit = 16;
unsigned Count = 0;
bool KilledT = false;
for (auto Iter = std::next(MovT.getIterator()),
E = MovT.getParent()->instr_end();
Iter != E && Count < SearchLimit && !KilledT; ++Iter, ++Count) {
MachineInstr *MovY = &*Iter;
KilledT = MovY->killsRegister(T, &TRI);
if ((MovY->getOpcode() != AMDGPU::V_MOV_B32_e32 &&
MovY->getOpcode() != AMDGPU::COPY) ||
!MovY->getOperand(1).isReg() ||
MovY->getOperand(1).getReg() != T ||
MovY->getOperand(1).getSubReg() != Tsub ||
MovY->hasRegisterImplicitUseOperand(AMDGPU::M0))
continue;
Register Y = MovY->getOperand(0).getReg();
unsigned Ysub = MovY->getOperand(0).getSubReg();
if (!TRI.isVGPR(MRI, Y))
continue;
MachineInstr *MovX = nullptr;
for (auto IY = MovY->getIterator(), I = std::next(MovT.getIterator());
I != IY; ++I) {
if (instReadsReg(&*I, X, Xsub, TRI) ||
instModifiesReg(&*I, Y, Ysub, TRI) ||
instModifiesReg(&*I, T, Tsub, TRI) ||
(MovX && instModifiesReg(&*I, X, Xsub, TRI))) {
MovX = nullptr;
break;
}
if (!instReadsReg(&*I, Y, Ysub, TRI)) {
if (!MovX && instModifiesReg(&*I, X, Xsub, TRI)) {
MovX = nullptr;
break;
}
continue;
}
if (MovX ||
(I->getOpcode() != AMDGPU::V_MOV_B32_e32 &&
I->getOpcode() != AMDGPU::COPY) ||
I->getOperand(0).getReg() != X ||
I->getOperand(0).getSubReg() != Xsub) {
MovX = nullptr;
break;
}
// Implicit use of M0 is an indirect move.
if (I->hasRegisterImplicitUseOperand(AMDGPU::M0))
continue;
if (Size > 1 && (I->getNumImplicitOperands() > (I->isCopy() ? 0U : 1U)))
continue;
MovX = &*I;
}
if (!MovX)
continue;
LLVM_DEBUG(dbgs() << "Matched v_swap_b32:\n" << MovT << *MovX << *MovY);
for (unsigned I = 0; I < Size; ++I) {
TargetInstrInfo::RegSubRegPair X1, Y1;
X1 = getSubRegForIndex(X, Xsub, I, TRI, MRI);
Y1 = getSubRegForIndex(Y, Ysub, I, TRI, MRI);
MachineBasicBlock &MBB = *MovT.getParent();
auto MIB = BuildMI(MBB, MovX->getIterator(), MovT.getDebugLoc(),
TII->get(AMDGPU::V_SWAP_B32))
.addDef(X1.Reg, 0, X1.SubReg)
.addDef(Y1.Reg, 0, Y1.SubReg)
.addReg(Y1.Reg, 0, Y1.SubReg)
.addReg(X1.Reg, 0, X1.SubReg).getInstr();
if (MovX->hasRegisterImplicitUseOperand(AMDGPU::EXEC)) {
// Drop implicit EXEC.
MIB->RemoveOperand(MIB->getNumExplicitOperands());
MIB->copyImplicitOps(*MBB.getParent(), *MovX);
}
}
MovX->eraseFromParent();
dropInstructionKeepingImpDefs(*MovY, TII);
MachineInstr *Next = &*std::next(MovT.getIterator());
if (T.isVirtual() && MRI.use_nodbg_empty(T)) {
dropInstructionKeepingImpDefs(MovT, TII);
} else {
Xop.setIsKill(false);
for (int I = MovT.getNumImplicitOperands() - 1; I >= 0; --I ) {
unsigned OpNo = MovT.getNumExplicitOperands() + I;
const MachineOperand &Op = MovT.getOperand(OpNo);
if (Op.isKill() && TRI.regsOverlap(X, Op.getReg()))
MovT.RemoveOperand(OpNo);
}
}
return Next;
}
return nullptr;
}
bool SIShrinkInstructions::runOnMachineFunction(MachineFunction &MF) {
if (skipFunction(MF.getFunction()))
return false;
MachineRegisterInfo &MRI = MF.getRegInfo();
const GCNSubtarget &ST = MF.getSubtarget<GCNSubtarget>();
const SIInstrInfo *TII = ST.getInstrInfo();
unsigned VCCReg = ST.isWave32() ? AMDGPU::VCC_LO : AMDGPU::VCC;
std::vector<unsigned> I1Defs;
for (MachineFunction::iterator BI = MF.begin(), BE = MF.end();
BI != BE; ++BI) {
MachineBasicBlock &MBB = *BI;
MachineBasicBlock::iterator I, Next;
for (I = MBB.begin(); I != MBB.end(); I = Next) {
Next = std::next(I);
MachineInstr &MI = *I;
if (MI.getOpcode() == AMDGPU::V_MOV_B32_e32) {
// If this has a literal constant source that is the same as the
// reversed bits of an inline immediate, replace with a bitreverse of
// that constant. This saves 4 bytes in the common case of materializing
// sign bits.
// Test if we are after regalloc. We only want to do this after any
// optimizations happen because this will confuse them.
// XXX - not exactly a check for post-regalloc run.
MachineOperand &Src = MI.getOperand(1);
if (Src.isImm() && MI.getOperand(0).getReg().isPhysical()) {
int32_t ReverseImm;
if (isReverseInlineImm(TII, Src, ReverseImm)) {
MI.setDesc(TII->get(AMDGPU::V_BFREV_B32_e32));
Src.setImm(ReverseImm);
continue;
}
}
}
if (ST.hasSwap() && (MI.getOpcode() == AMDGPU::V_MOV_B32_e32 ||
MI.getOpcode() == AMDGPU::COPY)) {
if (auto *NextMI = matchSwap(MI, MRI, TII)) {
Next = NextMI->getIterator();
continue;
}
}
// FIXME: We also need to consider movs of constant operands since
// immediate operands are not folded if they have more than one use, and
// the operand folding pass is unaware if the immediate will be free since
// it won't know if the src == dest constraint will end up being
// satisfied.
if (MI.getOpcode() == AMDGPU::S_ADD_I32 ||
MI.getOpcode() == AMDGPU::S_MUL_I32) {
const MachineOperand *Dest = &MI.getOperand(0);
MachineOperand *Src0 = &MI.getOperand(1);
MachineOperand *Src1 = &MI.getOperand(2);
if (!Src0->isReg() && Src1->isReg()) {
if (TII->commuteInstruction(MI, false, 1, 2))
std::swap(Src0, Src1);
}
// FIXME: This could work better if hints worked with subregisters. If
// we have a vector add of a constant, we usually don't get the correct
// allocation due to the subregister usage.
if (Dest->getReg().isVirtual() && Src0->isReg()) {
MRI.setRegAllocationHint(Dest->getReg(), 0, Src0->getReg());
MRI.setRegAllocationHint(Src0->getReg(), 0, Dest->getReg());
continue;
}
if (Src0->isReg() && Src0->getReg() == Dest->getReg()) {
if (Src1->isImm() && isKImmOperand(TII, *Src1)) {
unsigned Opc = (MI.getOpcode() == AMDGPU::S_ADD_I32) ?
AMDGPU::S_ADDK_I32 : AMDGPU::S_MULK_I32;
MI.setDesc(TII->get(Opc));
MI.tieOperands(0, 1);
}
}
}
// Try to use s_cmpk_*
if (MI.isCompare() && TII->isSOPC(MI)) {
shrinkScalarCompare(TII, MI);
continue;
}
// Try to use S_MOVK_I32, which will save 4 bytes for small immediates.
if (MI.getOpcode() == AMDGPU::S_MOV_B32) {
const MachineOperand &Dst = MI.getOperand(0);
MachineOperand &Src = MI.getOperand(1);
if (Src.isImm() && Dst.getReg().isPhysical()) {
int32_t ReverseImm;
if (isKImmOperand(TII, Src))
MI.setDesc(TII->get(AMDGPU::S_MOVK_I32));
else if (isReverseInlineImm(TII, Src, ReverseImm)) {
MI.setDesc(TII->get(AMDGPU::S_BREV_B32));
Src.setImm(ReverseImm);
}
}
continue;
}
// Shrink scalar logic operations.
if (MI.getOpcode() == AMDGPU::S_AND_B32 ||
MI.getOpcode() == AMDGPU::S_OR_B32 ||
MI.getOpcode() == AMDGPU::S_XOR_B32) {
if (shrinkScalarLogicOp(ST, MRI, TII, MI))
continue;
}
if (TII->isMIMG(MI.getOpcode()) &&
ST.getGeneration() >= AMDGPUSubtarget::GFX10 &&
MF.getProperties().hasProperty(
MachineFunctionProperties::Property::NoVRegs)) {
shrinkMIMG(MI);
continue;
}
if (!TII->hasVALU32BitEncoding(MI.getOpcode()))
continue;
if (!TII->canShrink(MI, MRI)) {
// Try commuting the instruction and see if that enables us to shrink
// it.
if (!MI.isCommutable() || !TII->commuteInstruction(MI) ||
!TII->canShrink(MI, MRI))
continue;
}
int Op32 = AMDGPU::getVOPe32(MI.getOpcode());
if (TII->isVOPC(Op32)) {
Register DstReg = MI.getOperand(0).getReg();
if (DstReg.isVirtual()) {
// VOPC instructions can only write to the VCC register. We can't
// force them to use VCC here, because this is only one register and
// cannot deal with sequences which would require multiple copies of
// VCC, e.g. S_AND_B64 (vcc = V_CMP_...), (vcc = V_CMP_...)
//
// So, instead of forcing the instruction to write to VCC, we provide
// a hint to the register allocator to use VCC and then we will run
// this pass again after RA and shrink it if it outputs to VCC.
MRI.setRegAllocationHint(MI.getOperand(0).getReg(), 0, VCCReg);
continue;
}
if (DstReg != VCCReg)
continue;
}
if (Op32 == AMDGPU::V_CNDMASK_B32_e32) {
// We shrink V_CNDMASK_B32_e64 using regalloc hints like we do for VOPC
// instructions.
const MachineOperand *Src2 =
TII->getNamedOperand(MI, AMDGPU::OpName::src2);
if (!Src2->isReg())
continue;
Register SReg = Src2->getReg();
if (SReg.isVirtual()) {
MRI.setRegAllocationHint(SReg, 0, VCCReg);
continue;
}
if (SReg != VCCReg)
continue;
}
// Check for the bool flag output for instructions like V_ADD_I32_e64.
const MachineOperand *SDst = TII->getNamedOperand(MI,
AMDGPU::OpName::sdst);
if (SDst) {
bool Next = false;
if (SDst->getReg() != VCCReg) {
if (SDst->getReg().isVirtual())
MRI.setRegAllocationHint(SDst->getReg(), 0, VCCReg);
Next = true;
}
// All of the instructions with carry outs also have an SGPR input in
// src2.
const MachineOperand *Src2 = TII->getNamedOperand(MI,
AMDGPU::OpName::src2);
if (Src2 && Src2->getReg() != VCCReg) {
if (Src2->getReg().isVirtual())
MRI.setRegAllocationHint(Src2->getReg(), 0, VCCReg);
Next = true;
}
if (Next)
continue;
}
// We can shrink this instruction
LLVM_DEBUG(dbgs() << "Shrinking " << MI);
MachineInstr *Inst32 = TII->buildShrunkInst(MI, Op32);
++NumInstructionsShrunk;
// Copy extra operands not present in the instruction definition.
copyExtraImplicitOps(*Inst32, MF, MI);
// Copy deadness from the old explicit vcc def to the new implicit def.
if (SDst && SDst->isDead())
Inst32->findRegisterDefOperand(VCCReg)->setIsDead();
MI.eraseFromParent();
foldImmediates(*Inst32, TII, MRI);
LLVM_DEBUG(dbgs() << "e32 MI = " << *Inst32 << '\n');
}
}
return false;
}
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