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Avoid hoisting spills when looking at a copy from another register that is also 

about to be spilled.

This can only happen when two extra snippet registers are included in the spill,
and there is a copy between them. Hoisting the spill creates problems because
the hoist will mark the copy for later dead code elimination, and spilling the
second register will turn the copy into a spill.

<rdar://problem/9420853>

llvm-svn: 131192
This commit is contained in:
Jakob Stoklund Olesen 2011-05-11 18:25:10 +00:00
parent c7c465c573
commit 31a0b5e2f0
1 changed files with 16 additions and 7 deletions
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23
llvm/lib/CodeGen/InlineSpiller.cpp
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@ -855,6 +855,7 @@ void InlineSpiller::insertSpill(LiveInterval &NewLI, const LiveInterval &OldLI,
/// spillAroundUses - insert spill code around each use of Reg.
void InlineSpiller::spillAroundUses(unsigned Reg) {
DEBUG(dbgs() << "spillAroundUses " << PrintReg(Reg) << '\n');
LiveInterval &OldLI = LIS.getInterval(Reg);
// Iterate over instructions using Reg.
@ -902,6 +903,12 @@ void InlineSpiller::spillAroundUses(unsigned Reg) {
// Check for a sibling copy.
unsigned SibReg = isFullCopyOf(MI, Reg);
if (SibReg && isSibling(SibReg)) {
// This may actually be a copy between snippets.
if (isRegToSpill(SibReg)) {
DEBUG(dbgs() << "Found new snippet copy: " << *MI);
SnippetCopies.insert(MI);
continue;
}
if (Writes) {
// Hoist the spill of a sib-reg copy.
if (hoistSpill(OldLI, MI)) {
@ -983,13 +990,15 @@ void InlineSpiller::spillAll() {
}
// Finally delete the SnippetCopies.
for (MachineRegisterInfo::reg_iterator RI = MRI.reg_begin(Edit->getReg());
MachineInstr *MI = RI.skipInstruction();) {
assert(SnippetCopies.count(MI) && "Remaining use wasn't a snippet copy");
// FIXME: Do this with a LiveRangeEdit callback.
VRM.RemoveMachineInstrFromMaps(MI);
LIS.RemoveMachineInstrFromMaps(MI);
MI->eraseFromParent();
for (unsigned i = 0, e = RegsToSpill.size(); i != e; ++i) {
for (MachineRegisterInfo::reg_iterator RI = MRI.reg_begin(RegsToSpill[i]);
MachineInstr *MI = RI.skipInstruction();) {
assert(SnippetCopies.count(MI) && "Remaining use wasn't a snippet copy");
// FIXME: Do this with a LiveRangeEdit callback.
VRM.RemoveMachineInstrFromMaps(MI);
LIS.RemoveMachineInstrFromMaps(MI);
MI->eraseFromParent();
}
}
// Delete all spilled registers.