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//===- RDFCopy.cpp --------------------------------------------------------===//
//
// 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
//
//===----------------------------------------------------------------------===//
//
// RDF-based copy propagation.
//
//===----------------------------------------------------------------------===//
#include "RDFCopy.h"
#include "llvm/CodeGen/MachineDominators.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/MachineOperand.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/RDFGraph.h"
#include "llvm/CodeGen/RDFLiveness.h"
#include "llvm/CodeGen/RDFRegisters.h"
#include "llvm/CodeGen/TargetOpcodes.h"
#include "llvm/CodeGen/TargetRegisterInfo.h"
#include "llvm/MC/MCRegisterInfo.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/raw_ostream.h"
#include <cassert>
#include <cstdint>
#include <utility>
using namespace llvm;
using namespace rdf;
#ifndef NDEBUG
static cl::opt<unsigned> CpLimit("rdf-cp-limit", cl::init(0), cl::Hidden);
static unsigned CpCount = 0;
#endif
bool CopyPropagation::interpretAsCopy(const MachineInstr *MI, EqualityMap &EM) {
unsigned Opc = MI->getOpcode();
switch (Opc) {
case TargetOpcode::COPY: {
const MachineOperand &Dst = MI->getOperand(0);
const MachineOperand &Src = MI->getOperand(1);
RegisterRef DstR = DFG.makeRegRef(Dst.getReg(), Dst.getSubReg());
RegisterRef SrcR = DFG.makeRegRef(Src.getReg(), Src.getSubReg());
assert(Register::isPhysicalRegister(DstR.Reg));
assert(Register::isPhysicalRegister(SrcR.Reg));
const TargetRegisterInfo &TRI = DFG.getTRI();
if (TRI.getMinimalPhysRegClass(DstR.Reg) !=
TRI.getMinimalPhysRegClass(SrcR.Reg))
return false;
EM.insert(std::make_pair(DstR, SrcR));
return true;
}
case TargetOpcode::REG_SEQUENCE:
llvm_unreachable("Unexpected REG_SEQUENCE");
}
return false;
}
void CopyPropagation::recordCopy(NodeAddr<StmtNode*> SA, EqualityMap &EM) {
CopyMap.insert(std::make_pair(SA.Id, EM));
Copies.push_back(SA.Id);
}
bool CopyPropagation::scanBlock(MachineBasicBlock *B) {
bool Changed = false;
NodeAddr<BlockNode*> BA = DFG.findBlock(B);
for (NodeAddr<InstrNode*> IA : BA.Addr->members(DFG)) {
if (DFG.IsCode<NodeAttrs::Stmt>(IA)) {
NodeAddr<StmtNode*> SA = IA;
EqualityMap EM;
if (interpretAsCopy(SA.Addr->getCode(), EM))
recordCopy(SA, EM);
}
}
MachineDomTreeNode *N = MDT.getNode(B);
for (auto I : *N)
Changed |= scanBlock(I->getBlock());
return Changed;
}
NodeId CopyPropagation::getLocalReachingDef(RegisterRef RefRR,
NodeAddr<InstrNode*> IA) {
NodeAddr<RefNode*> RA = L.getNearestAliasedRef(RefRR, IA);
if (RA.Id != 0) {
if (RA.Addr->getKind() == NodeAttrs::Def)
return RA.Id;
assert(RA.Addr->getKind() == NodeAttrs::Use);
if (NodeId RD = RA.Addr->getReachingDef())
return RD;
}
return 0;
}
bool CopyPropagation::run() {
scanBlock(&DFG.getMF().front());
if (trace()) {
dbgs() << "Copies:\n";
for (NodeId I : Copies) {
dbgs() << "Instr: " << *DFG.addr<StmtNode*>(I).Addr->getCode();
dbgs() << " eq: {";
for (auto J : CopyMap[I])
dbgs() << ' ' << Print<RegisterRef>(J.first, DFG) << '='
<< Print<RegisterRef>(J.second, DFG);
dbgs() << " }\n";
}
}
bool Changed = false;
#ifndef NDEBUG
bool HasLimit = CpLimit.getNumOccurrences() > 0;
#endif
auto MinPhysReg = [this] (RegisterRef RR) -> unsigned {
const TargetRegisterInfo &TRI = DFG.getTRI();
const TargetRegisterClass &RC = *TRI.getMinimalPhysRegClass(RR.Reg);
if ((RC.LaneMask & RR.Mask) == RC.LaneMask)
return RR.Reg;
for (MCSubRegIndexIterator S(RR.Reg, &TRI); S.isValid(); ++S)
if (RR.Mask == TRI.getSubRegIndexLaneMask(S.getSubRegIndex()))
return S.getSubReg();
llvm_unreachable("Should have found a register");
return 0;
};
for (NodeId C : Copies) {
#ifndef NDEBUG
if (HasLimit && CpCount >= CpLimit)
break;
#endif
auto SA = DFG.addr<InstrNode*>(C);
auto FS = CopyMap.find(SA.Id);
if (FS == CopyMap.end())
continue;
EqualityMap &EM = FS->second;
for (NodeAddr<DefNode*> DA : SA.Addr->members_if(DFG.IsDef, DFG)) {
RegisterRef DR = DA.Addr->getRegRef(DFG);
auto FR = EM.find(DR);
if (FR == EM.end())
continue;
RegisterRef SR = FR->second;
if (DR == SR)
continue;
NodeId AtCopy = getLocalReachingDef(SR, SA);
for (NodeId N = DA.Addr->getReachedUse(), NextN; N; N = NextN) {
auto UA = DFG.addr<UseNode*>(N);
NextN = UA.Addr->getSibling();
uint16_t F = UA.Addr->getFlags();
if ((F & NodeAttrs::PhiRef) || (F & NodeAttrs::Fixed))
continue;
if (UA.Addr->getRegRef(DFG) != DR)
continue;
NodeAddr<InstrNode*> IA = UA.Addr->getOwner(DFG);
assert(DFG.IsCode<NodeAttrs::Stmt>(IA));
NodeId AtUse = getLocalReachingDef(SR, IA);
if (AtCopy != AtUse)
continue;
MachineOperand &Op = UA.Addr->getOp();
if (Op.isTied())
continue;
if (trace()) {
dbgs() << "Can replace " << Print<RegisterRef>(DR, DFG)
<< " with " << Print<RegisterRef>(SR, DFG) << " in "
<< *NodeAddr<StmtNode*>(IA).Addr->getCode();
}
unsigned NewReg = MinPhysReg(SR);
Op.setReg(NewReg);
Op.setSubReg(0);
DFG.unlinkUse(UA, false);
if (AtCopy != 0) {
UA.Addr->linkToDef(UA.Id, DFG.addr<DefNode*>(AtCopy));
} else {
UA.Addr->setReachingDef(0);
UA.Addr->setSibling(0);
}
Changed = true;
#ifndef NDEBUG
if (HasLimit && CpCount >= CpLimit)
break;
CpCount++;
#endif
auto FC = CopyMap.find(IA.Id);
if (FC != CopyMap.end()) {
// Update the EM map in the copy's entry.
auto &M = FC->second;
for (auto &J : M) {
if (J.second != DR)
continue;
J.second = SR;
break;
}
}
} // for (N in reached-uses)
} // for (DA in defs)
} // for (C in Copies)
return Changed;
}
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