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Careful with reg_sequence coalescing to not to overwrite sub-register indices.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@103971 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Evan Cheng
2010-05-17 20:57:12 +00:00
parent 7f43fd84db
commit 53c779bb3a
2 changed files with 119 additions and 40 deletions
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117
lib/CodeGen/TwoAddressInstructionPass.cpp
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@ -128,6 +128,8 @@ namespace {
void ProcessCopy(MachineInstr *MI, MachineBasicBlock *MBB,
SmallPtrSet<MachineInstr*, 8> &Processed);
void CoalesceExtSubRegs(SmallVector<unsigned,4> &Srcs, unsigned DstReg);
/// EliminateRegSequences - Eliminate REG_SEQUENCE instructions as part
/// of the de-ssa process. This replaces sources of REG_SEQUENCE as
/// sub-register references of the register defined by REG_SEQUENCE.
@ -1132,7 +1134,7 @@ bool TwoAddressInstructionPass::runOnMachineFunction(MachineFunction &MF) {
}
static void UpdateRegSequenceSrcs(unsigned SrcReg,
unsigned DstReg, unsigned SrcIdx,
unsigned DstReg, unsigned SubIdx,
MachineRegisterInfo *MRI) {
for (MachineRegisterInfo::reg_iterator RI = MRI->reg_begin(SrcReg),
RE = MRI->reg_end(); RI != RE; ) {
@ -1140,7 +1142,77 @@ static void UpdateRegSequenceSrcs(unsigned SrcReg,
++RI;
MO.setReg(DstReg);
assert(MO.getSubReg() == 0);
MO.setSubReg(SrcIdx);
MO.setSubReg(SubIdx);
}
}
/// CoalesceExtSubRegs - If a number of sources of the REG_SEQUENCE are
/// EXTRACT_SUBREG from the same register and to the same virtual register
/// with different sub-register indices, attempt to combine the
/// EXTRACT_SUBREGs and pre-coalesce them. e.g.
/// %reg1026<def> = VLDMQ %reg1025<kill>, 260, pred:14, pred:%reg0
/// %reg1029:6<def> = EXTRACT_SUBREG %reg1026, 6
/// %reg1029:5<def> = EXTRACT_SUBREG %reg1026<kill>, 5
/// Since D subregs 5, 6 can combine to a Q register, we can coalesce
/// reg1026 to reg1029.
void
TwoAddressInstructionPass::CoalesceExtSubRegs(SmallVector<unsigned,4> &Srcs,
unsigned DstReg) {
SmallSet<unsigned, 4> Seen;
for (unsigned i = 0, e = Srcs.size(); i != e; ++i) {
unsigned SrcReg = Srcs[i];
if (!Seen.insert(SrcReg))
continue;
// If there are no other uses than extract_subreg which feed into
// the reg_sequence, then we might be able to coalesce them.
bool CanCoalesce = true;
SmallVector<unsigned, 4> SubIndices;
for (MachineRegisterInfo::use_nodbg_iterator
UI = MRI->use_nodbg_begin(SrcReg),
UE = MRI->use_nodbg_end(); UI != UE; ++UI) {
MachineInstr *UseMI = &*UI;
if (!UseMI->isExtractSubreg() ||
UseMI->getOperand(0).getReg() != DstReg) {
CanCoalesce = false;
break;
}
SubIndices.push_back(UseMI->getOperand(2).getImm());
}
if (!CanCoalesce || SubIndices.size() < 2)
continue;
std::sort(SubIndices.begin(), SubIndices.end());
unsigned NewSubIdx = 0;
if (TRI->canCombinedSubRegIndex(MRI->getRegClass(SrcReg), SubIndices,
NewSubIdx)) {
bool Proceed = true;
if (NewSubIdx)
for (MachineRegisterInfo::reg_iterator RI = MRI->reg_begin(SrcReg),
RE = MRI->reg_end(); RI != RE; ) {
MachineOperand &MO = RI.getOperand();
++RI;
// FIXME: If the sub-registers do not combine to the whole
// super-register, i.e. NewSubIdx != 0, and any of the use has a
// sub-register index, then abort the coalescing attempt.
if (MO.getSubReg()) {
Proceed = false;
break;
}
MO.setReg(DstReg);
MO.setSubReg(NewSubIdx);
}
if (Proceed)
for (MachineRegisterInfo::reg_iterator RI = MRI->reg_begin(SrcReg),
RE = MRI->reg_end(); RI != RE; ) {
MachineOperand &MO = RI.getOperand();
++RI;
MO.setReg(DstReg);
if (NewSubIdx)
MO.setSubReg(NewSubIdx);
}
}
}
}
@ -1221,50 +1293,15 @@ bool TwoAddressInstructionPass::EliminateRegSequences() {
for (unsigned i = 1, e = MI->getNumOperands(); i < e; i += 2) {
unsigned SrcReg = MI->getOperand(i).getReg();
unsigned SrcIdx = MI->getOperand(i+1).getImm();
UpdateRegSequenceSrcs(SrcReg, DstReg, SrcIdx, MRI);
unsigned SubIdx = MI->getOperand(i+1).getImm();
UpdateRegSequenceSrcs(SrcReg, DstReg, SubIdx, MRI);
}
DEBUG(dbgs() << "Eliminated: " << *MI);
MI->eraseFromParent();
// Try coalescing some EXTRACT_SUBREG instructions.
Seen.clear();
for (unsigned i = 0, e = RealSrcs.size(); i != e; ++i) {
unsigned SrcReg = RealSrcs[i];
if (!Seen.insert(SrcReg))
continue;
// If there are no other uses than extract_subreg which feed into
// the reg_sequence, then we might be able to coalesce them.
bool CanCoalesce = true;
SmallVector<unsigned, 4> SubIndices;
for (MachineRegisterInfo::use_nodbg_iterator
UI = MRI->use_nodbg_begin(SrcReg),
UE = MRI->use_nodbg_end(); UI != UE; ++UI) {
MachineInstr *UseMI = &*UI;
if (!UseMI->isExtractSubreg() ||
UseMI->getOperand(0).getReg() != DstReg) {
CanCoalesce = false;
break;
}
SubIndices.push_back(UseMI->getOperand(2).getImm());
}
if (!CanCoalesce)
continue;
// %reg1026<def> = VLDMQ %reg1025<kill>, 260, pred:14, pred:%reg0
// %reg1029:6<def> = EXTRACT_SUBREG %reg1026, 6
// %reg1029:5<def> = EXTRACT_SUBREG %reg1026<kill>, 5
// Since D subregs 5, 6 can combine to a Q register, we can coalesce
// reg1026 to reg1029.
std::sort(SubIndices.begin(), SubIndices.end());
unsigned NewSubIdx = 0;
if (TRI->canCombinedSubRegIndex(MRI->getRegClass(SrcReg), SubIndices,
NewSubIdx))
UpdateRegSequenceSrcs(SrcReg, DstReg, NewSubIdx, MRI);
}
CoalesceExtSubRegs(RealSrcs, DstReg);
}
RegSequences.clear();