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llvm-mirror/lib/CodeGen/GlobalISel/Utils.cpp
Matt Arsenault f91d7e4c2e GlobalISel: Use early return and reduce indentation
2020-06-16 14:47:08 -04:00

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//===- llvm/CodeGen/GlobalISel/Utils.cpp -------------------------*- C++ -*-==//
//
// 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 This file implements the utility functions used by the GlobalISel
/// pipeline.
//===----------------------------------------------------------------------===//
#include "llvm/CodeGen/GlobalISel/Utils.h"
#include "llvm/ADT/APFloat.h"
#include "llvm/ADT/Twine.h"
#include "llvm/CodeGen/GlobalISel/GISelChangeObserver.h"
#include "llvm/CodeGen/GlobalISel/RegisterBankInfo.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineOptimizationRemarkEmitter.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/StackProtector.h"
#include "llvm/CodeGen/TargetInstrInfo.h"
#include "llvm/CodeGen/TargetPassConfig.h"
#include "llvm/CodeGen/TargetRegisterInfo.h"
#include "llvm/IR/Constants.h"
#define DEBUG_TYPE "globalisel-utils"
using namespace llvm;
Register llvm::constrainRegToClass(MachineRegisterInfo &MRI,
const TargetInstrInfo &TII,
const RegisterBankInfo &RBI, Register Reg,
const TargetRegisterClass &RegClass) {
if (!RBI.constrainGenericRegister(Reg, RegClass, MRI))
return MRI.createVirtualRegister(&RegClass);
return Reg;
}
Register llvm::constrainOperandRegClass(
const MachineFunction &MF, const TargetRegisterInfo &TRI,
MachineRegisterInfo &MRI, const TargetInstrInfo &TII,
const RegisterBankInfo &RBI, MachineInstr &InsertPt,
const TargetRegisterClass &RegClass, const MachineOperand &RegMO) {
Register Reg = RegMO.getReg();
// Assume physical registers are properly constrained.
assert(Register::isVirtualRegister(Reg) && "PhysReg not implemented");
Register ConstrainedReg = constrainRegToClass(MRI, TII, RBI, Reg, RegClass);
// If we created a new virtual register because the class is not compatible
// then create a copy between the new and the old register.
if (ConstrainedReg != Reg) {
MachineBasicBlock::iterator InsertIt(&InsertPt);
MachineBasicBlock &MBB = *InsertPt.getParent();
if (RegMO.isUse()) {
BuildMI(MBB, InsertIt, InsertPt.getDebugLoc(),
TII.get(TargetOpcode::COPY), ConstrainedReg)
.addReg(Reg);
} else {
assert(RegMO.isDef() && "Must be a definition");
BuildMI(MBB, std::next(InsertIt), InsertPt.getDebugLoc(),
TII.get(TargetOpcode::COPY), Reg)
.addReg(ConstrainedReg);
}
} else {
if (GISelChangeObserver *Observer = MF.getObserver()) {
if (!RegMO.isDef()) {
MachineInstr *RegDef = MRI.getVRegDef(Reg);
Observer->changedInstr(*RegDef);
}
Observer->changingAllUsesOfReg(MRI, Reg);
Observer->finishedChangingAllUsesOfReg();
}
}
return ConstrainedReg;
}
Register llvm::constrainOperandRegClass(
const MachineFunction &MF, const TargetRegisterInfo &TRI,
MachineRegisterInfo &MRI, const TargetInstrInfo &TII,
const RegisterBankInfo &RBI, MachineInstr &InsertPt, const MCInstrDesc &II,
const MachineOperand &RegMO, unsigned OpIdx) {
Register Reg = RegMO.getReg();
// Assume physical registers are properly constrained.
assert(Register::isVirtualRegister(Reg) && "PhysReg not implemented");
const TargetRegisterClass *RegClass = TII.getRegClass(II, OpIdx, &TRI, MF);
// Some of the target independent instructions, like COPY, may not impose any
// register class constraints on some of their operands: If it's a use, we can
// skip constraining as the instruction defining the register would constrain
// it.
// We can't constrain unallocatable register classes, because we can't create
// virtual registers for these classes, so we need to let targets handled this
// case.
if (RegClass && !RegClass->isAllocatable())
RegClass = TRI.getConstrainedRegClassForOperand(RegMO, MRI);
if (!RegClass) {
assert((!isTargetSpecificOpcode(II.getOpcode()) || RegMO.isUse()) &&
"Register class constraint is required unless either the "
"instruction is target independent or the operand is a use");
// FIXME: Just bailing out like this here could be not enough, unless we
// expect the users of this function to do the right thing for PHIs and
// COPY:
// v1 = COPY v0
// v2 = COPY v1
// v1 here may end up not being constrained at all. Please notice that to
// reproduce the issue we likely need a destination pattern of a selection
// rule producing such extra copies, not just an input GMIR with them as
// every existing target using selectImpl handles copies before calling it
// and they never reach this function.
return Reg;
}
return constrainOperandRegClass(MF, TRI, MRI, TII, RBI, InsertPt, *RegClass,
RegMO);
}
bool llvm::constrainSelectedInstRegOperands(MachineInstr &I,
const TargetInstrInfo &TII,
const TargetRegisterInfo &TRI,
const RegisterBankInfo &RBI) {
assert(!isPreISelGenericOpcode(I.getOpcode()) &&
"A selected instruction is expected");
MachineBasicBlock &MBB = *I.getParent();
MachineFunction &MF = *MBB.getParent();
MachineRegisterInfo &MRI = MF.getRegInfo();
for (unsigned OpI = 0, OpE = I.getNumExplicitOperands(); OpI != OpE; ++OpI) {
MachineOperand &MO = I.getOperand(OpI);
// There's nothing to be done on non-register operands.
if (!MO.isReg())
continue;
LLVM_DEBUG(dbgs() << "Converting operand: " << MO << '\n');
assert(MO.isReg() && "Unsupported non-reg operand");
Register Reg = MO.getReg();
// Physical registers don't need to be constrained.
if (Register::isPhysicalRegister(Reg))
continue;
// Register operands with a value of 0 (e.g. predicate operands) don't need
// to be constrained.
if (Reg == 0)
continue;
// If the operand is a vreg, we should constrain its regclass, and only
// insert COPYs if that's impossible.
// constrainOperandRegClass does that for us.
MO.setReg(constrainOperandRegClass(MF, TRI, MRI, TII, RBI, I, I.getDesc(),
MO, OpI));
// Tie uses to defs as indicated in MCInstrDesc if this hasn't already been
// done.
if (MO.isUse()) {
int DefIdx = I.getDesc().getOperandConstraint(OpI, MCOI::TIED_TO);
if (DefIdx != -1 && !I.isRegTiedToUseOperand(DefIdx))
I.tieOperands(DefIdx, OpI);
}
}
return true;
}
bool llvm::canReplaceReg(Register DstReg, Register SrcReg,
MachineRegisterInfo &MRI) {
// Give up if either DstReg or SrcReg is a physical register.
if (DstReg.isPhysical() || SrcReg.isPhysical())
return false;
// Give up if the types don't match.
if (MRI.getType(DstReg) != MRI.getType(SrcReg))
return false;
// Replace if either DstReg has no constraints or the register
// constraints match.
return !MRI.getRegClassOrRegBank(DstReg) ||
MRI.getRegClassOrRegBank(DstReg) == MRI.getRegClassOrRegBank(SrcReg);
}
bool llvm::isTriviallyDead(const MachineInstr &MI,
const MachineRegisterInfo &MRI) {
// If we can move an instruction, we can remove it. Otherwise, it has
// a side-effect of some sort.
bool SawStore = false;
if (!MI.isSafeToMove(/*AA=*/nullptr, SawStore) && !MI.isPHI())
return false;
// Instructions without side-effects are dead iff they only define dead vregs.
for (auto &MO : MI.operands()) {
if (!MO.isReg() || !MO.isDef())
continue;
Register Reg = MO.getReg();
if (Register::isPhysicalRegister(Reg) || !MRI.use_nodbg_empty(Reg))
return false;
}
return true;
}
static void reportGISelDiagnostic(DiagnosticSeverity Severity,
MachineFunction &MF,
const TargetPassConfig &TPC,
MachineOptimizationRemarkEmitter &MORE,
MachineOptimizationRemarkMissed &R) {
bool IsFatal = Severity == DS_Error &&
TPC.isGlobalISelAbortEnabled();
// Print the function name explicitly if we don't have a debug location (which
// makes the diagnostic less useful) or if we're going to emit a raw error.
if (!R.getLocation().isValid() || IsFatal)
R << (" (in function: " + MF.getName() + ")").str();
if (IsFatal)
report_fatal_error(R.getMsg());
else
MORE.emit(R);
}
void llvm::reportGISelWarning(MachineFunction &MF, const TargetPassConfig &TPC,
MachineOptimizationRemarkEmitter &MORE,
MachineOptimizationRemarkMissed &R) {
reportGISelDiagnostic(DS_Warning, MF, TPC, MORE, R);
}
void llvm::reportGISelFailure(MachineFunction &MF, const TargetPassConfig &TPC,
MachineOptimizationRemarkEmitter &MORE,
MachineOptimizationRemarkMissed &R) {
MF.getProperties().set(MachineFunctionProperties::Property::FailedISel);
reportGISelDiagnostic(DS_Error, MF, TPC, MORE, R);
}
void llvm::reportGISelFailure(MachineFunction &MF, const TargetPassConfig &TPC,
MachineOptimizationRemarkEmitter &MORE,
const char *PassName, StringRef Msg,
const MachineInstr &MI) {
MachineOptimizationRemarkMissed R(PassName, "GISelFailure: ",
MI.getDebugLoc(), MI.getParent());
R << Msg;
// Printing MI is expensive; only do it if expensive remarks are enabled.
if (TPC.isGlobalISelAbortEnabled() || MORE.allowExtraAnalysis(PassName))
R << ": " << ore::MNV("Inst", MI);
reportGISelFailure(MF, TPC, MORE, R);
}
Optional<int64_t> llvm::getConstantVRegVal(Register VReg,
const MachineRegisterInfo &MRI) {
Optional<ValueAndVReg> ValAndVReg =
getConstantVRegValWithLookThrough(VReg, MRI, /*LookThroughInstrs*/ false);
assert((!ValAndVReg || ValAndVReg->VReg == VReg) &&
"Value found while looking through instrs");
if (!ValAndVReg)
return None;
return ValAndVReg->Value;
}
Optional<ValueAndVReg> llvm::getConstantVRegValWithLookThrough(
Register VReg, const MachineRegisterInfo &MRI, bool LookThroughInstrs,
bool HandleFConstant) {
SmallVector<std::pair<unsigned, unsigned>, 4> SeenOpcodes;
MachineInstr *MI;
auto IsConstantOpcode = [HandleFConstant](unsigned Opcode) {
return Opcode == TargetOpcode::G_CONSTANT ||
(HandleFConstant && Opcode == TargetOpcode::G_FCONSTANT);
};
auto GetImmediateValue = [HandleFConstant,
&MRI](const MachineInstr &MI) -> Optional<APInt> {
const MachineOperand &CstVal = MI.getOperand(1);
if (!CstVal.isImm() && !CstVal.isCImm() &&
(!HandleFConstant || !CstVal.isFPImm()))
return None;
if (!CstVal.isFPImm()) {
unsigned BitWidth =
MRI.getType(MI.getOperand(0).getReg()).getSizeInBits();
APInt Val = CstVal.isImm() ? APInt(BitWidth, CstVal.getImm())
: CstVal.getCImm()->getValue();
assert(Val.getBitWidth() == BitWidth &&
"Value bitwidth doesn't match definition type");
return Val;
}
return CstVal.getFPImm()->getValueAPF().bitcastToAPInt();
};
while ((MI = MRI.getVRegDef(VReg)) && !IsConstantOpcode(MI->getOpcode()) &&
LookThroughInstrs) {
switch (MI->getOpcode()) {
case TargetOpcode::G_TRUNC:
case TargetOpcode::G_SEXT:
case TargetOpcode::G_ZEXT:
SeenOpcodes.push_back(std::make_pair(
MI->getOpcode(),
MRI.getType(MI->getOperand(0).getReg()).getSizeInBits()));
VReg = MI->getOperand(1).getReg();
break;
case TargetOpcode::COPY:
VReg = MI->getOperand(1).getReg();
if (Register::isPhysicalRegister(VReg))
return None;
break;
case TargetOpcode::G_INTTOPTR:
VReg = MI->getOperand(1).getReg();
break;
default:
return None;
}
}
if (!MI || !IsConstantOpcode(MI->getOpcode()))
return None;
Optional<APInt> MaybeVal = GetImmediateValue(*MI);
if (!MaybeVal)
return None;
APInt &Val = *MaybeVal;
while (!SeenOpcodes.empty()) {
std::pair<unsigned, unsigned> OpcodeAndSize = SeenOpcodes.pop_back_val();
switch (OpcodeAndSize.first) {
case TargetOpcode::G_TRUNC:
Val = Val.trunc(OpcodeAndSize.second);
break;
case TargetOpcode::G_SEXT:
Val = Val.sext(OpcodeAndSize.second);
break;
case TargetOpcode::G_ZEXT:
Val = Val.zext(OpcodeAndSize.second);
break;
}
}
if (Val.getBitWidth() > 64)
return None;
return ValueAndVReg{Val.getSExtValue(), VReg};
}
const llvm::ConstantFP *
llvm::getConstantFPVRegVal(Register VReg, const MachineRegisterInfo &MRI) {
MachineInstr *MI = MRI.getVRegDef(VReg);
if (TargetOpcode::G_FCONSTANT != MI->getOpcode())
return nullptr;
return MI->getOperand(1).getFPImm();
}
namespace {
struct DefinitionAndSourceRegister {
llvm::MachineInstr *MI;
Register Reg;
};
} // namespace
static llvm::Optional<DefinitionAndSourceRegister>
getDefSrcRegIgnoringCopies(Register Reg, const MachineRegisterInfo &MRI) {
Register DefSrcReg = Reg;
auto *DefMI = MRI.getVRegDef(Reg);
auto DstTy = MRI.getType(DefMI->getOperand(0).getReg());
if (!DstTy.isValid())
return None;
while (DefMI->getOpcode() == TargetOpcode::COPY) {
Register SrcReg = DefMI->getOperand(1).getReg();
auto SrcTy = MRI.getType(SrcReg);
if (!SrcTy.isValid() || SrcTy != DstTy)
break;
DefMI = MRI.getVRegDef(SrcReg);
DefSrcReg = SrcReg;
}
return DefinitionAndSourceRegister{DefMI, DefSrcReg};
}
llvm::MachineInstr *llvm::getDefIgnoringCopies(Register Reg,
const MachineRegisterInfo &MRI) {
Optional<DefinitionAndSourceRegister> DefSrcReg =
getDefSrcRegIgnoringCopies(Reg, MRI);
return DefSrcReg ? DefSrcReg->MI : nullptr;
}
Register llvm::getSrcRegIgnoringCopies(Register Reg,
const MachineRegisterInfo &MRI) {
Optional<DefinitionAndSourceRegister> DefSrcReg =
getDefSrcRegIgnoringCopies(Reg, MRI);
return DefSrcReg ? DefSrcReg->Reg : Register();
}
llvm::MachineInstr *llvm::getOpcodeDef(unsigned Opcode, Register Reg,
const MachineRegisterInfo &MRI) {
MachineInstr *DefMI = getDefIgnoringCopies(Reg, MRI);
return DefMI && DefMI->getOpcode() == Opcode ? DefMI : nullptr;
}
APFloat llvm::getAPFloatFromSize(double Val, unsigned Size) {
if (Size == 32)
return APFloat(float(Val));
if (Size == 64)
return APFloat(Val);
if (Size != 16)
llvm_unreachable("Unsupported FPConstant size");
bool Ignored;
APFloat APF(Val);
APF.convert(APFloat::IEEEhalf(), APFloat::rmNearestTiesToEven, &Ignored);
return APF;
}
Optional<APInt> llvm::ConstantFoldBinOp(unsigned Opcode, const Register Op1,
const Register Op2,
const MachineRegisterInfo &MRI) {
auto MaybeOp2Cst = getConstantVRegVal(Op2, MRI);
if (!MaybeOp2Cst)
return None;
auto MaybeOp1Cst = getConstantVRegVal(Op1, MRI);
if (!MaybeOp1Cst)
return None;
LLT Ty = MRI.getType(Op1);
APInt C1(Ty.getSizeInBits(), *MaybeOp1Cst, true);
APInt C2(Ty.getSizeInBits(), *MaybeOp2Cst, true);
switch (Opcode) {
default:
break;
case TargetOpcode::G_ADD:
return C1 + C2;
case TargetOpcode::G_AND:
return C1 & C2;
case TargetOpcode::G_ASHR:
return C1.ashr(C2);
case TargetOpcode::G_LSHR:
return C1.lshr(C2);
case TargetOpcode::G_MUL:
return C1 * C2;
case TargetOpcode::G_OR:
return C1 | C2;
case TargetOpcode::G_SHL:
return C1 << C2;
case TargetOpcode::G_SUB:
return C1 - C2;
case TargetOpcode::G_XOR:
return C1 ^ C2;
case TargetOpcode::G_UDIV:
if (!C2.getBoolValue())
break;
return C1.udiv(C2);
case TargetOpcode::G_SDIV:
if (!C2.getBoolValue())
break;
return C1.sdiv(C2);
case TargetOpcode::G_UREM:
if (!C2.getBoolValue())
break;
return C1.urem(C2);
case TargetOpcode::G_SREM:
if (!C2.getBoolValue())
break;
return C1.srem(C2);
}
return None;
}
bool llvm::isKnownNeverNaN(Register Val, const MachineRegisterInfo &MRI,
bool SNaN) {
const MachineInstr *DefMI = MRI.getVRegDef(Val);
if (!DefMI)
return false;
if (DefMI->getFlag(MachineInstr::FmNoNans))
return true;
if (SNaN) {
// FP operations quiet. For now, just handle the ones inserted during
// legalization.
switch (DefMI->getOpcode()) {
case TargetOpcode::G_FPEXT:
case TargetOpcode::G_FPTRUNC:
case TargetOpcode::G_FCANONICALIZE:
return true;
default:
return false;
}
}
return false;
}
Align llvm::inferAlignFromPtrInfo(MachineFunction &MF,
const MachinePointerInfo &MPO) {
auto PSV = MPO.V.dyn_cast<const PseudoSourceValue *>();
if (auto FSPV = dyn_cast_or_null<FixedStackPseudoSourceValue>(PSV)) {
MachineFrameInfo &MFI = MF.getFrameInfo();
return commonAlignment(MFI.getObjectAlign(FSPV->getFrameIndex()),
MPO.Offset);
}
return Align(1);
}
Optional<APInt> llvm::ConstantFoldExtOp(unsigned Opcode, const Register Op1,
uint64_t Imm,
const MachineRegisterInfo &MRI) {
auto MaybeOp1Cst = getConstantVRegVal(Op1, MRI);
if (MaybeOp1Cst) {
LLT Ty = MRI.getType(Op1);
APInt C1(Ty.getSizeInBits(), *MaybeOp1Cst, true);
switch (Opcode) {
default:
break;
case TargetOpcode::G_SEXT_INREG:
return C1.trunc(Imm).sext(C1.getBitWidth());
}
}
return None;
}
void llvm::getSelectionDAGFallbackAnalysisUsage(AnalysisUsage &AU) {
AU.addPreserved<StackProtector>();
}
LLT llvm::getLCMType(LLT Ty0, LLT Ty1) {
if (!Ty0.isVector() && !Ty1.isVector()) {
unsigned Mul = Ty0.getSizeInBits() * Ty1.getSizeInBits();
int GCDSize = greatestCommonDivisor(Ty0.getSizeInBits(),
Ty1.getSizeInBits());
return LLT::scalar(Mul / GCDSize);
}
if (Ty0.isVector() && !Ty1.isVector()) {
assert(Ty0.getElementType() == Ty1 && "not yet handled");
return Ty0;
}
if (Ty1.isVector() && !Ty0.isVector()) {
assert(Ty1.getElementType() == Ty0 && "not yet handled");
return Ty1;
}
if (Ty0.isVector() && Ty1.isVector()) {
assert(Ty0.getElementType() == Ty1.getElementType() && "not yet handled");
int GCDElts = greatestCommonDivisor(Ty0.getNumElements(),
Ty1.getNumElements());
int Mul = Ty0.getNumElements() * Ty1.getNumElements();
return LLT::vector(Mul / GCDElts, Ty0.getElementType());
}
llvm_unreachable("not yet handled");
}
LLT llvm::getGCDType(LLT OrigTy, LLT TargetTy) {
if (OrigTy.isVector() && TargetTy.isVector()) {
assert(OrigTy.getElementType() == TargetTy.getElementType());
int GCD = greatestCommonDivisor(OrigTy.getNumElements(),
TargetTy.getNumElements());
return LLT::scalarOrVector(GCD, OrigTy.getElementType());
}
if (OrigTy.isVector() && !TargetTy.isVector()) {
assert(OrigTy.getElementType() == TargetTy);
return TargetTy;
}
assert(!OrigTy.isVector() && !TargetTy.isVector() &&
"GCD type of vector and scalar not implemented");
int GCD = greatestCommonDivisor(OrigTy.getSizeInBits(),
TargetTy.getSizeInBits());
return LLT::scalar(GCD);
}
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