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

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//===- SIFixSGPRCopies.cpp - Remove potential VGPR => SGPR copies ---------===//
//
// 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
/// Copies from VGPR to SGPR registers are illegal and the register coalescer
/// will sometimes generate these illegal copies in situations like this:
///
/// Register Class <vsrc> is the union of <vgpr> and <sgpr>
///
/// BB0:
/// %0 <sgpr> = SCALAR_INST
/// %1 <vsrc> = COPY %0 <sgpr>
/// ...
/// BRANCH %cond BB1, BB2
/// BB1:
/// %2 <vgpr> = VECTOR_INST
/// %3 <vsrc> = COPY %2 <vgpr>
/// BB2:
/// %4 <vsrc> = PHI %1 <vsrc>, <%bb.0>, %3 <vrsc>, <%bb.1>
/// %5 <vgpr> = VECTOR_INST %4 <vsrc>
///
///
/// The coalescer will begin at BB0 and eliminate its copy, then the resulting
/// code will look like this:
///
/// BB0:
/// %0 <sgpr> = SCALAR_INST
/// ...
/// BRANCH %cond BB1, BB2
/// BB1:
/// %2 <vgpr> = VECTOR_INST
/// %3 <vsrc> = COPY %2 <vgpr>
/// BB2:
/// %4 <sgpr> = PHI %0 <sgpr>, <%bb.0>, %3 <vsrc>, <%bb.1>
/// %5 <vgpr> = VECTOR_INST %4 <sgpr>
///
/// Now that the result of the PHI instruction is an SGPR, the register
/// allocator is now forced to constrain the register class of %3 to
/// <sgpr> so we end up with final code like this:
///
/// BB0:
/// %0 <sgpr> = SCALAR_INST
/// ...
/// BRANCH %cond BB1, BB2
/// BB1:
/// %2 <vgpr> = VECTOR_INST
/// %3 <sgpr> = COPY %2 <vgpr>
/// BB2:
/// %4 <sgpr> = PHI %0 <sgpr>, <%bb.0>, %3 <sgpr>, <%bb.1>
/// %5 <vgpr> = VECTOR_INST %4 <sgpr>
///
/// Now this code contains an illegal copy from a VGPR to an SGPR.
///
/// In order to avoid this problem, this pass searches for PHI instructions
/// which define a <vsrc> register and constrains its definition class to
/// <vgpr> if the user of the PHI's definition register is a vector instruction.
/// If the PHI's definition class is constrained to <vgpr> then the coalescer
/// will be unable to perform the COPY removal from the above example which
/// ultimately led to the creation of an illegal COPY.
//===----------------------------------------------------------------------===//
#include "AMDGPU.h"
#include "GCNSubtarget.h"
#include "MCTargetDesc/AMDGPUMCTargetDesc.h"
#include "llvm/CodeGen/MachineDominators.h"
#include "llvm/InitializePasses.h"
#include "llvm/Target/TargetMachine.h"
using namespace llvm;
#define DEBUG_TYPE "si-fix-sgpr-copies"
static cl::opt<bool> EnableM0Merge(
"amdgpu-enable-merge-m0",
cl::desc("Merge and hoist M0 initializations"),
cl::init(true));
namespace {
class SIFixSGPRCopies : public MachineFunctionPass {
MachineDominatorTree *MDT;
public:
static char ID;
MachineRegisterInfo *MRI;
const SIRegisterInfo *TRI;
const SIInstrInfo *TII;
SIFixSGPRCopies() : MachineFunctionPass(ID) {}
bool runOnMachineFunction(MachineFunction &MF) override;
MachineBasicBlock *processPHINode(MachineInstr &MI);
StringRef getPassName() const override { return "SI Fix SGPR copies"; }
void getAnalysisUsage(AnalysisUsage &AU) const override {
AU.addRequired<MachineDominatorTree>();
AU.addPreserved<MachineDominatorTree>();
AU.setPreservesCFG();
MachineFunctionPass::getAnalysisUsage(AU);
}
};
} // end anonymous namespace
INITIALIZE_PASS_BEGIN(SIFixSGPRCopies, DEBUG_TYPE,
"SI Fix SGPR copies", false, false)
INITIALIZE_PASS_DEPENDENCY(MachineDominatorTree)
INITIALIZE_PASS_END(SIFixSGPRCopies, DEBUG_TYPE,
"SI Fix SGPR copies", false, false)
char SIFixSGPRCopies::ID = 0;
char &llvm::SIFixSGPRCopiesID = SIFixSGPRCopies::ID;
FunctionPass *llvm::createSIFixSGPRCopiesPass() {
return new SIFixSGPRCopies();
}
static bool hasVectorOperands(const MachineInstr &MI,
const SIRegisterInfo *TRI) {
const MachineRegisterInfo &MRI = MI.getParent()->getParent()->getRegInfo();
for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) {
if (!MI.getOperand(i).isReg() || !MI.getOperand(i).getReg().isVirtual())
continue;
if (TRI->hasVectorRegisters(MRI.getRegClass(MI.getOperand(i).getReg())))
return true;
}
return false;
}
static std::pair<const TargetRegisterClass *, const TargetRegisterClass *>
getCopyRegClasses(const MachineInstr &Copy,
const SIRegisterInfo &TRI,
const MachineRegisterInfo &MRI) {
Register DstReg = Copy.getOperand(0).getReg();
Register SrcReg = Copy.getOperand(1).getReg();
const TargetRegisterClass *SrcRC = SrcReg.isVirtual()
? MRI.getRegClass(SrcReg)
: TRI.getPhysRegClass(SrcReg);
// We don't really care about the subregister here.
// SrcRC = TRI.getSubRegClass(SrcRC, Copy.getOperand(1).getSubReg());
const TargetRegisterClass *DstRC = DstReg.isVirtual()
? MRI.getRegClass(DstReg)
: TRI.getPhysRegClass(DstReg);
return std::make_pair(SrcRC, DstRC);
}
static bool isVGPRToSGPRCopy(const TargetRegisterClass *SrcRC,
const TargetRegisterClass *DstRC,
const SIRegisterInfo &TRI) {
return SrcRC != &AMDGPU::VReg_1RegClass && TRI.isSGPRClass(DstRC) &&
TRI.hasVectorRegisters(SrcRC);
}
static bool isSGPRToVGPRCopy(const TargetRegisterClass *SrcRC,
const TargetRegisterClass *DstRC,
const SIRegisterInfo &TRI) {
return DstRC != &AMDGPU::VReg_1RegClass && TRI.isSGPRClass(SrcRC) &&
TRI.hasVectorRegisters(DstRC);
}
static bool tryChangeVGPRtoSGPRinCopy(MachineInstr &MI,
const SIRegisterInfo *TRI,
const SIInstrInfo *TII) {
MachineRegisterInfo &MRI = MI.getParent()->getParent()->getRegInfo();
auto &Src = MI.getOperand(1);
Register DstReg = MI.getOperand(0).getReg();
Register SrcReg = Src.getReg();
if (!SrcReg.isVirtual() || !DstReg.isVirtual())
return false;
for (const auto &MO : MRI.reg_nodbg_operands(DstReg)) {
const auto *UseMI = MO.getParent();
if (UseMI == &MI)
continue;
if (MO.isDef() || UseMI->getParent() != MI.getParent() ||
UseMI->getOpcode() <= TargetOpcode::GENERIC_OP_END)
return false;
unsigned OpIdx = UseMI->getOperandNo(&MO);
if (OpIdx >= UseMI->getDesc().getNumOperands() ||
!TII->isOperandLegal(*UseMI, OpIdx, &Src))
return false;
}
// Change VGPR to SGPR destination.
MRI.setRegClass(DstReg, TRI->getEquivalentSGPRClass(MRI.getRegClass(DstReg)));
return true;
}
// Distribute an SGPR->VGPR copy of a REG_SEQUENCE into a VGPR REG_SEQUENCE.
//
// SGPRx = ...
// SGPRy = REG_SEQUENCE SGPRx, sub0 ...
// VGPRz = COPY SGPRy
//
// ==>
//
// VGPRx = COPY SGPRx
// VGPRz = REG_SEQUENCE VGPRx, sub0
//
// This exposes immediate folding opportunities when materializing 64-bit
// immediates.
static bool foldVGPRCopyIntoRegSequence(MachineInstr &MI,
const SIRegisterInfo *TRI,
const SIInstrInfo *TII,
MachineRegisterInfo &MRI) {
assert(MI.isRegSequence());
Register DstReg = MI.getOperand(0).getReg();
if (!TRI->isSGPRClass(MRI.getRegClass(DstReg)))
return false;
if (!MRI.hasOneUse(DstReg))
return false;
MachineInstr &CopyUse = *MRI.use_instr_begin(DstReg);
if (!CopyUse.isCopy())
return false;
// It is illegal to have vreg inputs to a physreg defining reg_sequence.
if (CopyUse.getOperand(0).getReg().isPhysical())
return false;
const TargetRegisterClass *SrcRC, *DstRC;
std::tie(SrcRC, DstRC) = getCopyRegClasses(CopyUse, *TRI, MRI);
if (!isSGPRToVGPRCopy(SrcRC, DstRC, *TRI))
return false;
if (tryChangeVGPRtoSGPRinCopy(CopyUse, TRI, TII))
return true;
// TODO: Could have multiple extracts?
unsigned SubReg = CopyUse.getOperand(1).getSubReg();
if (SubReg != AMDGPU::NoSubRegister)
return false;
MRI.setRegClass(DstReg, DstRC);
// SGPRx = ...
// SGPRy = REG_SEQUENCE SGPRx, sub0 ...
// VGPRz = COPY SGPRy
// =>
// VGPRx = COPY SGPRx
// VGPRz = REG_SEQUENCE VGPRx, sub0
MI.getOperand(0).setReg(CopyUse.getOperand(0).getReg());
bool IsAGPR = TRI->hasAGPRs(DstRC);
for (unsigned I = 1, N = MI.getNumOperands(); I != N; I += 2) {
Register SrcReg = MI.getOperand(I).getReg();
unsigned SrcSubReg = MI.getOperand(I).getSubReg();
const TargetRegisterClass *SrcRC = MRI.getRegClass(SrcReg);
assert(TRI->isSGPRClass(SrcRC) &&
"Expected SGPR REG_SEQUENCE to only have SGPR inputs");
SrcRC = TRI->getSubRegClass(SrcRC, SrcSubReg);
const TargetRegisterClass *NewSrcRC = TRI->getEquivalentVGPRClass(SrcRC);
Register TmpReg = MRI.createVirtualRegister(NewSrcRC);
BuildMI(*MI.getParent(), &MI, MI.getDebugLoc(), TII->get(AMDGPU::COPY),
TmpReg)
.add(MI.getOperand(I));
if (IsAGPR) {
const TargetRegisterClass *NewSrcRC = TRI->getEquivalentAGPRClass(SrcRC);
Register TmpAReg = MRI.createVirtualRegister(NewSrcRC);
unsigned Opc = NewSrcRC == &AMDGPU::AGPR_32RegClass ?
AMDGPU::V_ACCVGPR_WRITE_B32_e64 : AMDGPU::COPY;
BuildMI(*MI.getParent(), &MI, MI.getDebugLoc(), TII->get(Opc),
TmpAReg)
.addReg(TmpReg, RegState::Kill);
TmpReg = TmpAReg;
}
MI.getOperand(I).setReg(TmpReg);
}
CopyUse.eraseFromParent();
return true;
}
static bool isSafeToFoldImmIntoCopy(const MachineInstr *Copy,
const MachineInstr *MoveImm,
const SIInstrInfo *TII,
unsigned &SMovOp,
int64_t &Imm) {
if (Copy->getOpcode() != AMDGPU::COPY)
return false;
if (!MoveImm->isMoveImmediate())
return false;
const MachineOperand *ImmOp =
TII->getNamedOperand(*MoveImm, AMDGPU::OpName::src0);
if (!ImmOp->isImm())
return false;
// FIXME: Handle copies with sub-regs.
if (Copy->getOperand(0).getSubReg())
return false;
switch (MoveImm->getOpcode()) {
default:
return false;
case AMDGPU::V_MOV_B32_e32:
SMovOp = AMDGPU::S_MOV_B32;
break;
case AMDGPU::V_MOV_B64_PSEUDO:
SMovOp = AMDGPU::S_MOV_B64;
break;
}
Imm = ImmOp->getImm();
return true;
}
template <class UnaryPredicate>
bool searchPredecessors(const MachineBasicBlock *MBB,
const MachineBasicBlock *CutOff,
UnaryPredicate Predicate) {
if (MBB == CutOff)
return false;
DenseSet<const MachineBasicBlock *> Visited;
SmallVector<MachineBasicBlock *, 4> Worklist(MBB->predecessors());
while (!Worklist.empty()) {
MachineBasicBlock *MBB = Worklist.pop_back_val();
if (!Visited.insert(MBB).second)
continue;
if (MBB == CutOff)
continue;
if (Predicate(MBB))
return true;
Worklist.append(MBB->pred_begin(), MBB->pred_end());
}
return false;
}
// Checks if there is potential path From instruction To instruction.
// If CutOff is specified and it sits in between of that path we ignore
// a higher portion of the path and report it is not reachable.
static bool isReachable(const MachineInstr *From,
const MachineInstr *To,
const MachineBasicBlock *CutOff,
MachineDominatorTree &MDT) {
if (MDT.dominates(From, To))
return true;
const MachineBasicBlock *MBBFrom = From->getParent();
const MachineBasicBlock *MBBTo = To->getParent();
// Do predecessor search.
// We should almost never get here since we do not usually produce M0 stores
// other than -1.
return searchPredecessors(MBBTo, CutOff, [MBBFrom]
(const MachineBasicBlock *MBB) { return MBB == MBBFrom; });
}
// Return the first non-prologue instruction in the block.
static MachineBasicBlock::iterator
getFirstNonPrologue(MachineBasicBlock *MBB, const TargetInstrInfo *TII) {
MachineBasicBlock::iterator I = MBB->getFirstNonPHI();
while (I != MBB->end() && TII->isBasicBlockPrologue(*I))
++I;
return I;
}
// Hoist and merge identical SGPR initializations into a common predecessor.
// This is intended to combine M0 initializations, but can work with any
// SGPR. A VGPR cannot be processed since we cannot guarantee vector
// executioon.
static bool hoistAndMergeSGPRInits(unsigned Reg,
const MachineRegisterInfo &MRI,
const TargetRegisterInfo *TRI,
MachineDominatorTree &MDT,
const TargetInstrInfo *TII) {
// List of inits by immediate value.
using InitListMap = std::map<unsigned, std::list<MachineInstr *>>;
InitListMap Inits;
// List of clobbering instructions.
SmallVector<MachineInstr*, 8> Clobbers;
// List of instructions marked for deletion.
SmallSet<MachineInstr*, 8> MergedInstrs;
bool Changed = false;
for (auto &MI : MRI.def_instructions(Reg)) {
MachineOperand *Imm = nullptr;
for (auto &MO : MI.operands()) {
if ((MO.isReg() && ((MO.isDef() && MO.getReg() != Reg) || !MO.isDef())) ||
(!MO.isImm() && !MO.isReg()) || (MO.isImm() && Imm)) {
Imm = nullptr;
break;
} else if (MO.isImm())
Imm = &MO;
}
if (Imm)
Inits[Imm->getImm()].push_front(&MI);
else
Clobbers.push_back(&MI);
}
for (auto &Init : Inits) {
auto &Defs = Init.second;
for (auto I1 = Defs.begin(), E = Defs.end(); I1 != E; ) {
MachineInstr *MI1 = *I1;
for (auto I2 = std::next(I1); I2 != E; ) {
MachineInstr *MI2 = *I2;
// Check any possible interference
auto interferes = [&](MachineBasicBlock::iterator From,
MachineBasicBlock::iterator To) -> bool {
assert(MDT.dominates(&*To, &*From));
auto interferes = [&MDT, From, To](MachineInstr* &Clobber) -> bool {
const MachineBasicBlock *MBBFrom = From->getParent();
const MachineBasicBlock *MBBTo = To->getParent();
bool MayClobberFrom = isReachable(Clobber, &*From, MBBTo, MDT);
bool MayClobberTo = isReachable(Clobber, &*To, MBBTo, MDT);
if (!MayClobberFrom && !MayClobberTo)
return false;
if ((MayClobberFrom && !MayClobberTo) ||
(!MayClobberFrom && MayClobberTo))
return true;
// Both can clobber, this is not an interference only if both are
// dominated by Clobber and belong to the same block or if Clobber
// properly dominates To, given that To >> From, so it dominates
// both and located in a common dominator.
return !((MBBFrom == MBBTo &&
MDT.dominates(Clobber, &*From) &&
MDT.dominates(Clobber, &*To)) ||
MDT.properlyDominates(Clobber->getParent(), MBBTo));
};
return (llvm::any_of(Clobbers, interferes)) ||
(llvm::any_of(Inits, [&](InitListMap::value_type &C) {
return C.first != Init.first &&
llvm::any_of(C.second, interferes);
}));
};
if (MDT.dominates(MI1, MI2)) {
if (!interferes(MI2, MI1)) {
LLVM_DEBUG(dbgs()
<< "Erasing from "
<< printMBBReference(*MI2->getParent()) << " " << *MI2);
MergedInstrs.insert(MI2);
Changed = true;
++I2;
continue;
}
} else if (MDT.dominates(MI2, MI1)) {
if (!interferes(MI1, MI2)) {
LLVM_DEBUG(dbgs()
<< "Erasing from "
<< printMBBReference(*MI1->getParent()) << " " << *MI1);
MergedInstrs.insert(MI1);
Changed = true;
++I1;
break;
}
} else {
auto *MBB = MDT.findNearestCommonDominator(MI1->getParent(),
MI2->getParent());
if (!MBB) {
++I2;
continue;
}
MachineBasicBlock::iterator I = getFirstNonPrologue(MBB, TII);
if (!interferes(MI1, I) && !interferes(MI2, I)) {
LLVM_DEBUG(dbgs()
<< "Erasing from "
<< printMBBReference(*MI1->getParent()) << " " << *MI1
<< "and moving from "
<< printMBBReference(*MI2->getParent()) << " to "
<< printMBBReference(*I->getParent()) << " " << *MI2);
I->getParent()->splice(I, MI2->getParent(), MI2);
MergedInstrs.insert(MI1);
Changed = true;
++I1;
break;
}
}
++I2;
}
++I1;
}
}
// Remove initializations that were merged into another.
for (auto &Init : Inits) {
auto &Defs = Init.second;
auto I = Defs.begin();
while (I != Defs.end()) {
if (MergedInstrs.count(*I)) {
(*I)->eraseFromParent();
I = Defs.erase(I);
} else
++I;
}
}
// Try to schedule SGPR initializations as early as possible in the MBB.
for (auto &Init : Inits) {
auto &Defs = Init.second;
for (auto MI : Defs) {
auto MBB = MI->getParent();
MachineInstr &BoundaryMI = *getFirstNonPrologue(MBB, TII);
MachineBasicBlock::reverse_iterator B(BoundaryMI);
// Check if B should actually be a boundary. If not set the previous
// instruction as the boundary instead.
if (!TII->isBasicBlockPrologue(*B))
B++;
auto R = std::next(MI->getReverseIterator());
const unsigned Threshold = 50;
// Search until B or Threshold for a place to insert the initialization.
for (unsigned I = 0; R != B && I < Threshold; ++R, ++I)
if (R->readsRegister(Reg, TRI) || R->definesRegister(Reg, TRI) ||
TII->isSchedulingBoundary(*R, MBB, *MBB->getParent()))
break;
// Move to directly after R.
if (&*--R != MI)
MBB->splice(*R, MBB, MI);
}
}
if (Changed)
MRI.clearKillFlags(Reg);
return Changed;
}
bool SIFixSGPRCopies::runOnMachineFunction(MachineFunction &MF) {
// Only need to run this in SelectionDAG path.
if (MF.getProperties().hasProperty(
MachineFunctionProperties::Property::Selected))
return false;
const GCNSubtarget &ST = MF.getSubtarget<GCNSubtarget>();
MRI = &MF.getRegInfo();
TRI = ST.getRegisterInfo();
TII = ST.getInstrInfo();
MDT = &getAnalysis<MachineDominatorTree>();
for (MachineFunction::iterator BI = MF.begin(), BE = MF.end();
BI != BE; ++BI) {
MachineBasicBlock *MBB = &*BI;
for (MachineBasicBlock::iterator I = MBB->begin(), E = MBB->end(); I != E;
++I) {
MachineInstr &MI = *I;
switch (MI.getOpcode()) {
default:
continue;
case AMDGPU::COPY:
case AMDGPU::WQM:
case AMDGPU::STRICT_WQM:
case AMDGPU::SOFT_WQM:
case AMDGPU::STRICT_WWM: {
Register DstReg = MI.getOperand(0).getReg();
const TargetRegisterClass *SrcRC, *DstRC;
std::tie(SrcRC, DstRC) = getCopyRegClasses(MI, *TRI, *MRI);
if (MI.isCopy()) {
Register SrcReg = MI.getOperand(1).getReg();
if (SrcReg == AMDGPU::SCC) {
Register SCCCopy = MRI->createVirtualRegister(
TRI->getRegClass(AMDGPU::SReg_1_XEXECRegClassID));
I = BuildMI(*MI.getParent(),
std::next(MachineBasicBlock::iterator(MI)),
MI.getDebugLoc(),
TII->get(ST.isWave32() ? AMDGPU::S_CSELECT_B32
: AMDGPU::S_CSELECT_B64),
SCCCopy)
.addImm(-1)
.addImm(0);
I = BuildMI(*MI.getParent(), std::next(I), I->getDebugLoc(),
TII->get(AMDGPU::COPY), DstReg)
.addReg(SCCCopy);
MI.eraseFromParent();
continue;
} else if (DstReg == AMDGPU::SCC) {
unsigned Opcode =
ST.isWave64() ? AMDGPU::S_AND_B64 : AMDGPU::S_AND_B32;
Register Exec = ST.isWave64() ? AMDGPU::EXEC : AMDGPU::EXEC_LO;
Register Tmp = MRI->createVirtualRegister(TRI->getBoolRC());
I = BuildMI(*MI.getParent(),
std::next(MachineBasicBlock::iterator(MI)),
MI.getDebugLoc(), TII->get(Opcode))
.addReg(Tmp, getDefRegState(true))
.addReg(SrcReg)
.addReg(Exec);
MI.eraseFromParent();
continue;
}
}
if (!DstReg.isVirtual()) {
// If the destination register is a physical register there isn't
// really much we can do to fix this.
// Some special instructions use M0 as an input. Some even only use
// the first lane. Insert a readfirstlane and hope for the best.
if (DstReg == AMDGPU::M0 && TRI->hasVectorRegisters(SrcRC)) {
Register TmpReg
= MRI->createVirtualRegister(&AMDGPU::SReg_32_XM0RegClass);
BuildMI(*MBB, MI, MI.getDebugLoc(),
TII->get(AMDGPU::V_READFIRSTLANE_B32), TmpReg)
.add(MI.getOperand(1));
MI.getOperand(1).setReg(TmpReg);
}
continue;
}
if (isVGPRToSGPRCopy(SrcRC, DstRC, *TRI)) {
Register SrcReg = MI.getOperand(1).getReg();
if (!SrcReg.isVirtual()) {
MachineBasicBlock *NewBB = TII->moveToVALU(MI, MDT);
if (NewBB && NewBB != MBB) {
MBB = NewBB;
E = MBB->end();
BI = MachineFunction::iterator(MBB);
BE = MF.end();
}
assert((!NewBB || NewBB == I->getParent()) &&
"moveToVALU did not return the right basic block");
break;
}
MachineInstr *DefMI = MRI->getVRegDef(SrcReg);
unsigned SMovOp;
int64_t Imm;
// If we are just copying an immediate, we can replace the copy with
// s_mov_b32.
if (isSafeToFoldImmIntoCopy(&MI, DefMI, TII, SMovOp, Imm)) {
MI.getOperand(1).ChangeToImmediate(Imm);
MI.addImplicitDefUseOperands(MF);
MI.setDesc(TII->get(SMovOp));
break;
}
MachineBasicBlock *NewBB = TII->moveToVALU(MI, MDT);
if (NewBB && NewBB != MBB) {
MBB = NewBB;
E = MBB->end();
BI = MachineFunction::iterator(MBB);
BE = MF.end();
}
assert((!NewBB || NewBB == I->getParent()) &&
"moveToVALU did not return the right basic block");
} else if (isSGPRToVGPRCopy(SrcRC, DstRC, *TRI)) {
tryChangeVGPRtoSGPRinCopy(MI, TRI, TII);
}
break;
}
case AMDGPU::PHI: {
MachineBasicBlock *NewBB = processPHINode(MI);
if (NewBB && NewBB != MBB) {
MBB = NewBB;
E = MBB->end();
BI = MachineFunction::iterator(MBB);
BE = MF.end();
}
assert((!NewBB || NewBB == I->getParent()) &&
"moveToVALU did not return the right basic block");
break;
}
case AMDGPU::REG_SEQUENCE: {
if (TRI->hasVectorRegisters(TII->getOpRegClass(MI, 0)) ||
!hasVectorOperands(MI, TRI)) {
foldVGPRCopyIntoRegSequence(MI, TRI, TII, *MRI);
continue;
}
LLVM_DEBUG(dbgs() << "Fixing REG_SEQUENCE: " << MI);
MachineBasicBlock *NewBB = TII->moveToVALU(MI, MDT);
if (NewBB && NewBB != MBB) {
MBB = NewBB;
E = MBB->end();
BI = MachineFunction::iterator(MBB);
BE = MF.end();
}
assert((!NewBB || NewBB == I->getParent()) &&
"moveToVALU did not return the right basic block");
break;
}
case AMDGPU::INSERT_SUBREG: {
const TargetRegisterClass *DstRC, *Src0RC, *Src1RC;
DstRC = MRI->getRegClass(MI.getOperand(0).getReg());
Src0RC = MRI->getRegClass(MI.getOperand(1).getReg());
Src1RC = MRI->getRegClass(MI.getOperand(2).getReg());
if (TRI->isSGPRClass(DstRC) &&
(TRI->hasVectorRegisters(Src0RC) ||
TRI->hasVectorRegisters(Src1RC))) {
LLVM_DEBUG(dbgs() << " Fixing INSERT_SUBREG: " << MI);
MachineBasicBlock *NewBB = TII->moveToVALU(MI, MDT);
if (NewBB && NewBB != MBB) {
MBB = NewBB;
E = MBB->end();
BI = MachineFunction::iterator(MBB);
BE = MF.end();
}
assert((!NewBB || NewBB == I->getParent()) &&
"moveToVALU did not return the right basic block");
}
break;
}
case AMDGPU::V_WRITELANE_B32: {
// Some architectures allow more than one constant bus access without
// SGPR restriction
if (ST.getConstantBusLimit(MI.getOpcode()) != 1)
break;
// Writelane is special in that it can use SGPR and M0 (which would
// normally count as using the constant bus twice - but in this case it
// is allowed since the lane selector doesn't count as a use of the
// constant bus). However, it is still required to abide by the 1 SGPR
// rule. Apply a fix here as we might have multiple SGPRs after
// legalizing VGPRs to SGPRs
int Src0Idx =
AMDGPU::getNamedOperandIdx(MI.getOpcode(), AMDGPU::OpName::src0);
int Src1Idx =
AMDGPU::getNamedOperandIdx(MI.getOpcode(), AMDGPU::OpName::src1);
MachineOperand &Src0 = MI.getOperand(Src0Idx);
MachineOperand &Src1 = MI.getOperand(Src1Idx);
// Check to see if the instruction violates the 1 SGPR rule
if ((Src0.isReg() && TRI->isSGPRReg(*MRI, Src0.getReg()) &&
Src0.getReg() != AMDGPU::M0) &&
(Src1.isReg() && TRI->isSGPRReg(*MRI, Src1.getReg()) &&
Src1.getReg() != AMDGPU::M0)) {
// Check for trivially easy constant prop into one of the operands
// If this is the case then perform the operation now to resolve SGPR
// issue. If we don't do that here we will always insert a mov to m0
// that can't be resolved in later operand folding pass
bool Resolved = false;
for (MachineOperand *MO : {&Src0, &Src1}) {
if (MO->getReg().isVirtual()) {
MachineInstr *DefMI = MRI->getVRegDef(MO->getReg());
if (DefMI && TII->isFoldableCopy(*DefMI)) {
const MachineOperand &Def = DefMI->getOperand(0);
if (Def.isReg() &&
MO->getReg() == Def.getReg() &&
MO->getSubReg() == Def.getSubReg()) {
const MachineOperand &Copied = DefMI->getOperand(1);
if (Copied.isImm() &&
TII->isInlineConstant(APInt(64, Copied.getImm(), true))) {
MO->ChangeToImmediate(Copied.getImm());
Resolved = true;
break;
}
}
}
}
}
if (!Resolved) {
// Haven't managed to resolve by replacing an SGPR with an immediate
// Move src1 to be in M0
BuildMI(*MI.getParent(), MI, MI.getDebugLoc(),
TII->get(AMDGPU::COPY), AMDGPU::M0)
.add(Src1);
Src1.ChangeToRegister(AMDGPU::M0, false);
}
}
break;
}
}
}
}
if (MF.getTarget().getOptLevel() > CodeGenOpt::None && EnableM0Merge)
hoistAndMergeSGPRInits(AMDGPU::M0, *MRI, TRI, *MDT, TII);
return true;
}
MachineBasicBlock *SIFixSGPRCopies::processPHINode(MachineInstr &MI) {
unsigned numVGPRUses = 0;
bool AllAGPRUses = true;
SetVector<const MachineInstr *> worklist;
SmallSet<const MachineInstr *, 4> Visited;
SetVector<MachineInstr *> PHIOperands;
MachineBasicBlock *CreatedBB = nullptr;
worklist.insert(&MI);
Visited.insert(&MI);
while (!worklist.empty()) {
const MachineInstr *Instr = worklist.pop_back_val();
Register Reg = Instr->getOperand(0).getReg();
for (const auto &Use : MRI->use_operands(Reg)) {
const MachineInstr *UseMI = Use.getParent();
AllAGPRUses &= (UseMI->isCopy() &&
TRI->isAGPR(*MRI, UseMI->getOperand(0).getReg())) ||
TRI->isAGPR(*MRI, Use.getReg());
if (UseMI->isCopy() || UseMI->isRegSequence()) {
if (UseMI->isCopy() &&
UseMI->getOperand(0).getReg().isPhysical() &&
!TRI->isSGPRReg(*MRI, UseMI->getOperand(0).getReg())) {
numVGPRUses++;
}
if (Visited.insert(UseMI).second)
worklist.insert(UseMI);
continue;
}
if (UseMI->isPHI()) {
const TargetRegisterClass *UseRC = MRI->getRegClass(Use.getReg());
if (!TRI->isSGPRReg(*MRI, Use.getReg()) &&
UseRC != &AMDGPU::VReg_1RegClass)
numVGPRUses++;
continue;
}
const TargetRegisterClass *OpRC =
TII->getOpRegClass(*UseMI, UseMI->getOperandNo(&Use));
if (!TRI->isSGPRClass(OpRC) && OpRC != &AMDGPU::VS_32RegClass &&
OpRC != &AMDGPU::VS_64RegClass) {
numVGPRUses++;
}
}
}
Register PHIRes = MI.getOperand(0).getReg();
const TargetRegisterClass *RC0 = MRI->getRegClass(PHIRes);
if (AllAGPRUses && numVGPRUses && !TRI->hasAGPRs(RC0)) {
LLVM_DEBUG(dbgs() << "Moving PHI to AGPR: " << MI);
MRI->setRegClass(PHIRes, TRI->getEquivalentAGPRClass(RC0));
for (unsigned I = 1, N = MI.getNumOperands(); I != N; I += 2) {
MachineInstr *DefMI = MRI->getVRegDef(MI.getOperand(I).getReg());
if (DefMI && DefMI->isPHI())
PHIOperands.insert(DefMI);
}
}
bool hasVGPRInput = false;
for (unsigned i = 1; i < MI.getNumOperands(); i += 2) {
Register InputReg = MI.getOperand(i).getReg();
MachineInstr *Def = MRI->getVRegDef(InputReg);
if (TRI->isVectorRegister(*MRI, InputReg)) {
if (Def->isCopy()) {
Register SrcReg = Def->getOperand(1).getReg();
const TargetRegisterClass *RC =
TRI->getRegClassForReg(*MRI, SrcReg);
if (TRI->isSGPRClass(RC))
continue;
}
hasVGPRInput = true;
break;
}
else if (Def->isCopy() &&
TRI->isVectorRegister(*MRI, Def->getOperand(1).getReg())) {
Register SrcReg = Def->getOperand(1).getReg();
MachineInstr *SrcDef = MRI->getVRegDef(SrcReg);
unsigned SMovOp;
int64_t Imm;
if (!isSafeToFoldImmIntoCopy(Def, SrcDef, TII, SMovOp, Imm)) {
hasVGPRInput = true;
break;
} else {
// Formally, if we did not do this right away
// it would be done on the next iteration of the
// runOnMachineFunction main loop. But why not if we can?
MachineFunction *MF = MI.getParent()->getParent();
Def->getOperand(1).ChangeToImmediate(Imm);
Def->addImplicitDefUseOperands(*MF);
Def->setDesc(TII->get(SMovOp));
}
}
}
if ((!TRI->isVectorRegister(*MRI, PHIRes) &&
RC0 != &AMDGPU::VReg_1RegClass) &&
(hasVGPRInput || numVGPRUses > 1)) {
LLVM_DEBUG(dbgs() << "Fixing PHI: " << MI);
CreatedBB = TII->moveToVALU(MI);
}
else {
LLVM_DEBUG(dbgs() << "Legalizing PHI: " << MI);
TII->legalizeOperands(MI, MDT);
}
// Propagate register class back to PHI operands which are PHI themselves.
while (!PHIOperands.empty()) {
processPHINode(*PHIOperands.pop_back_val());
}
return CreatedBB;
}
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