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[GlobalISel] Add a 'getConstantVRegVal' helper. 

Use it to compare immediate operands.

llvm-svn: 298855
This commit is contained in:
Ahmed Bougacha 2017-03-27 16:35:27 +00:00
parent c1cbcee170
commit 2d29998f22
2 changed files with 24 additions and 12 deletions
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4
llvm/include/llvm/CodeGen/GlobalISel/InstructionSelector.h
View File

@ -16,6 +16,7 @@
#ifndef LLVM_CODEGEN_GLOBALISEL_INSTRUCTIONSELECTOR_H
#define LLVM_CODEGEN_GLOBALISEL_INSTRUCTIONSELECTOR_H
#include "llvm/ADT/Optional.h"
#include <cstdint>
namespace llvm {
@ -61,6 +62,9 @@ protected:
const TargetRegisterInfo &TRI,
const RegisterBankInfo &RBI) const;
Optional<int64_t> getConstantVRegVal(unsigned VReg,
const MachineRegisterInfo &MRI) const;
bool isOperandImmEqual(const MachineOperand &MO, int64_t Value,
const MachineRegisterInfo &MRI) const;
};

32
llvm/lib/CodeGen/GlobalISel/InstructionSelector.cpp
View File

@ -68,21 +68,29 @@ bool InstructionSelector::constrainSelectedInstRegOperands(
return true;
}
Optional<int64_t>
InstructionSelector::getConstantVRegVal(unsigned VReg,
const MachineRegisterInfo &MRI) const {
MachineInstr *MI = MRI.getVRegDef(VReg);
if (MI->getOpcode() != TargetOpcode::G_CONSTANT)
return None;
if (MI->getOperand(1).isImm())
return MI->getOperand(1).getImm();
if (MI->getOperand(1).isCImm() &&
MI->getOperand(1).getCImm()->getBitWidth() <= 64)
return MI->getOperand(1).getCImm()->getSExtValue();
return None;
}
bool InstructionSelector::isOperandImmEqual(
const MachineOperand &MO, int64_t Value,
const MachineRegisterInfo &MRI) const {
// TODO: We should also test isImm() and isCImm() too but this isn't required
// until a DAGCombine equivalent is implemented.
if (MO.isReg()) {
MachineInstr *Def = MRI.getVRegDef(MO.getReg());
if (Def->getOpcode() != TargetOpcode::G_CONSTANT)
return false;
assert(Def->getOperand(1).isCImm() &&
"G_CONSTANT values must be constants");
const ConstantInt &Imm = *Def->getOperand(1).getCImm();
return Imm.getBitWidth() <= 64 && Imm.getSExtValue() == Value;
}
if (MO.getReg())
if (auto VRegVal = getConstantVRegVal(MO.getReg(), MRI))
return *VRegVal == Value;
return false;
}