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[SEH] Push reloads of the SEH code past phi nodes

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This in turn would sometimes introduce new cleanupblocks that didn't
previously exist. The uses were being introduced by SSA value demotion.
We actually want to *promote* uses of EH pointers and selectors, so I
added some spcecial casing to avoid demoting such instructions.  This is
getting overly complicated, but hopefully we'll come along and delete it
in the new representation.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@241950 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Reid Kleckner
2015-07-10 22:21:54 +00:00
parent 34b9a7dcb1
commit 09450da653
2 changed files with 119 additions and 6 deletions
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34
lib/CodeGen/WinEHPrepare.cpp
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@ -616,6 +616,26 @@ void WinEHPrepare::demoteValuesLiveAcrossHandlers(
// identifyEHBlocks() should have been called before this function.
assert(!NormalBlocks.empty());
// Try to avoid demoting EH pointer and selector values. They get in the way
// of our pattern matching.
SmallPtrSet<Instruction *, 10> EHVals;
for (BasicBlock &BB : F) {
LandingPadInst *LP = BB.getLandingPadInst();
if (!LP)
continue;
EHVals.insert(LP);
for (User *U : LP->users()) {
auto *EI = dyn_cast<ExtractValueInst>(U);
if (!EI)
continue;
EHVals.insert(EI);
for (User *U2 : EI->users()) {
if (auto *PN = dyn_cast<PHINode>(U2))
EHVals.insert(PN);
}
}
}
SetVector<Argument *> ArgsToDemote;
SetVector<Instruction *> InstrsToDemote;
for (BasicBlock &BB : F) {
@ -641,7 +661,11 @@ void WinEHPrepare::demoteValuesLiveAcrossHandlers(
continue;
}
// Don't demote EH values.
auto *OpI = cast<Instruction>(Op);
if (EHVals.count(OpI))
continue;
BasicBlock *OpBB = OpI->getParent();
// If a value is produced and consumed in the same BB, we don't need to
// demote it.
@ -822,7 +846,8 @@ bool WinEHPrepare::prepareExceptionHandlers(
LPad->replaceAllUsesWith(UndefValue::get(LPad->getType()));
// Rewrite uses of the exception pointer to loads of an alloca.
for (Instruction *E : SEHCodeUses) {
while (!SEHCodeUses.empty()) {
Instruction *E = SEHCodeUses.pop_back_val();
SmallVector<Use *, 4> Uses;
for (Use &U : E->uses())
Uses.push_back(&U);
@ -830,13 +855,10 @@ bool WinEHPrepare::prepareExceptionHandlers(
auto *I = cast<Instruction>(U->getUser());
if (isa<ResumeInst>(I))
continue;
LoadInst *LI;
if (auto *Phi = dyn_cast<PHINode>(I))
LI = new LoadInst(SEHExceptionCodeSlot, "sehcode", false,
Phi->getIncomingBlock(*U)->getTerminator());
SEHCodeUses.push_back(Phi);
else
LI = new LoadInst(SEHExceptionCodeSlot, "sehcode", false, I);
U->set(LI);
U->set(new LoadInst(SEHExceptionCodeSlot, "sehcode", false, I));
}
E->replaceAllUsesWith(UndefValue::get(E->getType()));
E->eraseFromParent();