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//===---------- MIRVRegNamerUtils.cpp - MIR VReg Renaming Utilities -------===//
//
// 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
//
//===----------------------------------------------------------------------===//
#include "MIRVRegNamerUtils.h"
#include "llvm/Support/Debug.h"
using namespace llvm;
#define DEBUG_TYPE "mir-vregnamer-utils"
using VRegRenameMap = std::map<unsigned, unsigned>;
bool VRegRenamer::doVRegRenaming(const VRegRenameMap &VRM) {
bool Changed = false;
for (const auto &E : VRM) {
Changed = Changed || !MRI.reg_empty(E.first);
MRI.replaceRegWith(E.first, E.second);
}
return Changed;
}
VRegRenameMap
VRegRenamer::getVRegRenameMap(const std::vector<NamedVReg> &VRegs) {
StringMap<unsigned> VRegNameCollisionMap;
auto GetUniqueVRegName = [&VRegNameCollisionMap](const NamedVReg &Reg) {
if (VRegNameCollisionMap.find(Reg.getName()) == VRegNameCollisionMap.end())
VRegNameCollisionMap[Reg.getName()] = 0;
const unsigned Counter = ++VRegNameCollisionMap[Reg.getName()];
return Reg.getName() + "__" + std::to_string(Counter);
};
VRegRenameMap VRM;
for (const auto &VReg : VRegs) {
const unsigned Reg = VReg.getReg();
VRM[Reg] = createVirtualRegisterWithLowerName(Reg, GetUniqueVRegName(VReg));
}
return VRM;
}
std::string VRegRenamer::getInstructionOpcodeHash(MachineInstr &MI) {
std::string S;
raw_string_ostream OS(S);
// Gets a hashable artifact from a given MachineOperand (ie an unsigned).
auto GetHashableMO = [this](const MachineOperand &MO) -> unsigned {
if (MO.isImm())
return MO.getImm();
if (MO.isTargetIndex())
return MO.getOffset() | (MO.getTargetFlags() << 16);
if (MO.isReg() && Register::isVirtualRegister(MO.getReg()))
return MRI.getVRegDef(MO.getReg())->getOpcode();
if (MO.isReg())
return MO.getReg();
// TODO:
// We could explicitly handle all the types of the MachineOperand,
// here but we can just return a common number until we find a
// compelling test case where this is bad. The only side effect here
// is contributing to a hash collision but there's enough information
// (Opcodes,other registers etc) that this will likely not be a problem.
return 0;
};
SmallVector<unsigned, 16> MIOperands = {MI.getOpcode(), MI.getFlags()};
llvm::transform(MI.uses(), std::back_inserter(MIOperands), GetHashableMO);
for (const auto *Op : MI.memoperands()) {
MIOperands.push_back((unsigned)Op->getSize());
MIOperands.push_back((unsigned)Op->getFlags());
MIOperands.push_back((unsigned)Op->getOffset());
MIOperands.push_back((unsigned)Op->getOrdering());
MIOperands.push_back((unsigned)Op->getAddrSpace());
MIOperands.push_back((unsigned)Op->getSyncScopeID());
MIOperands.push_back((unsigned)Op->getBaseAlignment());
MIOperands.push_back((unsigned)Op->getFailureOrdering());
}
auto HashMI = hash_combine_range(MIOperands.begin(), MIOperands.end());
return std::to_string(HashMI).substr(0, 5);
}
unsigned VRegRenamer::createVirtualRegister(unsigned VReg) {
assert(Register::isVirtualRegister(VReg) && "Expected Virtual Registers");
std::string Name = getInstructionOpcodeHash(*MRI.getVRegDef(VReg));
return createVirtualRegisterWithLowerName(VReg, Name);
}
bool VRegRenamer::renameInstsInMBB(MachineBasicBlock *MBB) {
std::vector<NamedVReg> VRegs;
std::string Prefix = "bb" + std::to_string(CurrentBBNumber) + "_";
for (MachineInstr &Candidate : *MBB) {
// Don't rename stores/branches.
if (Candidate.mayStore() || Candidate.isBranch())
continue;
if (!Candidate.getNumOperands())
continue;
// Look for instructions that define VRegs in operand 0.
MachineOperand &MO = Candidate.getOperand(0);
// Avoid non regs, instructions defining physical regs.
if (!MO.isReg() || !Register::isVirtualRegister(MO.getReg()))
continue;
VRegs.push_back(
NamedVReg(MO.getReg(), Prefix + getInstructionOpcodeHash(Candidate)));
}
return VRegs.size() ? doVRegRenaming(getVRegRenameMap(VRegs)) : false;
}
unsigned VRegRenamer::createVirtualRegisterWithLowerName(unsigned VReg,
StringRef Name) {
std::string LowerName = Name.lower();
const TargetRegisterClass *RC = MRI.getRegClassOrNull(VReg);
return RC ? MRI.createVirtualRegister(RC, LowerName)
: MRI.createGenericVirtualRegister(MRI.getType(VReg), LowerName);
}
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