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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"
bool VRegRenamer::doVRegRenaming(
const std::map<unsigned, unsigned> &VRegRenameMap) {
bool Changed = false;
for (auto I = VRegRenameMap.begin(), E = VRegRenameMap.end(); I != E; ++I) {
auto VReg = I->first;
auto Rename = I->second;
std::vector<MachineOperand *> RenameMOs;
for (auto &MO : MRI.reg_operands(VReg)) {
RenameMOs.push_back(&MO);
}
for (auto *MO : RenameMOs) {
Changed = true;
MO->setReg(Rename);
if (!MO->isDef())
MO->setIsKill(false);
}
}
return Changed;
}
std::map<unsigned, unsigned>
VRegRenamer::getVRegRenameMap(const std::vector<NamedVReg> &VRegs) {
std::map<unsigned, unsigned> VRegRenameMap;
std::map<std::string, unsigned> VRegNameCollisionMap;
auto GetUniqueVRegName =
[&VRegNameCollisionMap](const NamedVReg &Reg) -> std::string {
auto It = VRegNameCollisionMap.find(Reg.getName());
unsigned Counter = 0;
if (It != VRegNameCollisionMap.end()) {
Counter = It->second;
}
++Counter;
VRegNameCollisionMap[Reg.getName()] = Counter;
return Reg.getName() + "__" + std::to_string(Counter);
};
for (auto &Vreg : VRegs) {
auto Reg = Vreg.getReg();
assert(Register::isVirtualRegister(Reg) &&
"Expecting Virtual Registers Only");
auto NewNameForReg = GetUniqueVRegName(Vreg);
auto Rename = createVirtualRegisterWithName(Reg, NewNameForReg);
VRegRenameMap.insert(std::pair<unsigned, unsigned>(Reg, Rename));
}
return VRegRenameMap;
}
std::string VRegRenamer::getInstructionOpcodeHash(MachineInstr &MI) {
std::string S;
raw_string_ostream OS(S);
auto HashOperand = [this](const MachineOperand &MO) -> unsigned {
if (MO.isImm())
return MO.getImm();
if (MO.isTargetIndex())
return MO.getOffset() | (MO.getTargetFlags() << 16);
if (MO.isReg()) {
return Register::isVirtualRegister(MO.getReg())
? MRI.getVRegDef(MO.getReg())->getOpcode()
: (unsigned)MO.getReg();
}
// 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 collission but there's enough information
// (Opcodes,other registers etc) that this will likely not be a problem.
return 0;
};
SmallVector<unsigned, 16> MIOperands;
MIOperands.push_back(MI.getOpcode());
for (auto &Op : MI.uses()) {
MIOperands.push_back(HashOperand(Op));
}
auto HashMI = hash_combine_range(MIOperands.begin(), MIOperands.end());
return std::to_string(HashMI).substr(0, 5);
}
unsigned VRegRenamer::createVirtualRegister(unsigned VReg) {
return createVirtualRegisterWithName(
VReg, getInstructionOpcodeHash(*MRI.getVRegDef(VReg)));
}
bool VRegRenamer::renameInstsInMBB(MachineBasicBlock *MBB) {
std::vector<NamedVReg> VRegs;
std::string Prefix = "bb" + std::to_string(getCurrentBBNumber()) + "_";
for (auto &MII : *MBB) {
MachineInstr &Candidate = MII;
// 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)));
}
// If we have populated no vregs to rename then bail.
// The rest of this function does the vreg remaping.
if (VRegs.size() == 0)
return false;
auto VRegRenameMap = getVRegRenameMap(VRegs);
return doVRegRenaming(VRegRenameMap);
}
bool VRegRenamer::renameVRegs(MachineBasicBlock *MBB, unsigned BBNum) {
CurrentBBNumber = BBNum;
return renameInstsInMBB(MBB);
}
unsigned VRegRenamer::createVirtualRegisterWithName(unsigned VReg,
const std::string &Name) {
std::string Temp(Name);
std::transform(Temp.begin(), Temp.end(), Temp.begin(), ::tolower);
if (auto RC = MRI.getRegClassOrNull(VReg))
return MRI.createVirtualRegister(RC, Temp);
return MRI.createGenericVirtualRegister(MRI.getType(VReg), Name);
}
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