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//===--- RDFCopy.cpp ------------------------------------------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// Simplistic RDF-based copy propagation.
#include "RDFCopy.h"
#include "RDFGraph.h"
#include "llvm/CodeGen/MachineBasicBlock.h"
#include "llvm/CodeGen/MachineDominators.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/Support/CommandLine.h"
#include <atomic>
#ifndef NDEBUG
static cl::opt<unsigned> CpLimit("rdf-cp-limit", cl::init(0), cl::Hidden);
static unsigned CpCount = 0;
#endif
using namespace llvm;
using namespace rdf;
void CopyPropagation::recordCopy(NodeAddr<StmtNode*> SA, MachineInstr *MI) {
assert(MI->getOpcode() == TargetOpcode::COPY);
const MachineOperand &Op0 = MI->getOperand(0), &Op1 = MI->getOperand(1);
RegisterRef DstR = { Op0.getReg(), Op0.getSubReg() };
RegisterRef SrcR = { Op1.getReg(), Op1.getSubReg() };
auto FS = DefM.find(SrcR);
if (FS == DefM.end() || FS->second.empty())
return;
Copies.push_back(SA.Id);
RDefMap[SrcR][SA.Id] = FS->second.top()->Id;
// Insert DstR into the map.
RDefMap[DstR];
}
void CopyPropagation::updateMap(NodeAddr<InstrNode*> IA) {
RegisterSet RRs;
for (NodeAddr<RefNode*> RA : IA.Addr->members(DFG))
RRs.insert(RA.Addr->getRegRef());
bool Common = false;
for (auto &R : RDefMap) {
if (!RRs.count(R.first))
continue;
Common = true;
break;
}
if (!Common)
return;
for (auto &R : RDefMap) {
if (!RRs.count(R.first))
continue;
auto F = DefM.find(R.first);
if (F == DefM.end() || F->second.empty())
continue;
R.second[IA.Id] = F->second.top()->Id;
}
}
bool CopyPropagation::scanBlock(MachineBasicBlock *B) {
bool Changed = false;
auto BA = DFG.getFunc().Addr->findBlock(B, DFG);
DFG.markBlock(BA.Id, DefM);
for (NodeAddr<InstrNode*> IA : BA.Addr->members(DFG)) {
if (DFG.IsCode<NodeAttrs::Stmt>(IA)) {
NodeAddr<StmtNode*> SA = IA;
MachineInstr *MI = SA.Addr->getCode();
if (MI->isCopy())
recordCopy(SA, MI);
}
updateMap(IA);
DFG.pushDefs(IA, DefM);
}
MachineDomTreeNode *N = MDT.getNode(B);
for (auto I : *N)
Changed |= scanBlock(I->getBlock());
DFG.releaseBlock(BA.Id, DefM);
return Changed;
}
bool CopyPropagation::run() {
scanBlock(&DFG.getMF().front());
if (trace()) {
dbgs() << "Copies:\n";
for (auto I : Copies)
dbgs() << *DFG.addr<StmtNode*>(I).Addr->getCode();
dbgs() << "\nRDef map:\n";
for (auto R : RDefMap) {
dbgs() << Print<RegisterRef>(R.first, DFG) << " -> {";
for (auto &M : R.second)
dbgs() << ' ' << Print<NodeId>(M.first, DFG) << ':'
<< Print<NodeId>(M.second, DFG);
dbgs() << " }\n";
}
}
bool Changed = false;
NodeSet Deleted;
#ifndef NDEBUG
bool HasLimit = CpLimit.getNumOccurrences() > 0;
#endif
for (auto I : Copies) {
#ifndef NDEBUG
if (HasLimit && CpCount >= CpLimit)
break;
#endif
if (Deleted.count(I))
continue;
auto SA = DFG.addr<InstrNode*>(I);
NodeList Ds = SA.Addr->members_if(DFG.IsDef, DFG);
if (Ds.size() != 1)
continue;
NodeAddr<DefNode*> DA = Ds[0];
RegisterRef DR0 = DA.Addr->getRegRef();
NodeList Us = SA.Addr->members_if(DFG.IsUse, DFG);
if (Us.size() != 1)
continue;
NodeAddr<UseNode*> UA0 = Us[0];
RegisterRef UR0 = UA0.Addr->getRegRef();
NodeId RD0 = UA0.Addr->getReachingDef();
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() != DR0)
continue;
NodeAddr<InstrNode*> IA = UA.Addr->getOwner(DFG);
assert(DFG.IsCode<NodeAttrs::Stmt>(IA));
MachineInstr *MI = NodeAddr<StmtNode*>(IA).Addr->getCode();
if (RDefMap[UR0][IA.Id] != RD0)
continue;
MachineOperand &Op = UA.Addr->getOp();
if (Op.isTied())
continue;
if (trace()) {
dbgs() << "can replace " << Print<RegisterRef>(DR0, DFG)
<< " with " << Print<RegisterRef>(UR0, DFG) << " in "
<< *NodeAddr<StmtNode*>(IA).Addr->getCode();
}
Op.setReg(UR0.Reg);
Op.setSubReg(UR0.Sub);
Changed = true;
#ifndef NDEBUG
if (HasLimit && CpCount >= CpLimit)
break;
CpCount++;
#endif
if (MI->isCopy()) {
MachineOperand &Op0 = MI->getOperand(0), &Op1 = MI->getOperand(1);
if (Op0.getReg() == Op1.getReg() && Op0.getSubReg() == Op1.getSubReg())
MI->eraseFromParent();
Deleted.insert(IA.Id);
}
}
}
return Changed;
}
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