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[Constant Hoisting] Don't update the use list while traversing it - DOH! 

This fix first traverses the whole use list of the constant expression and
keeps track of the instructions that need to be updated. Then perform the
fixup afterwards.

llvm-svn: 201008
This commit is contained in:
Juergen Ributzka 2014-02-08 00:20:45 +00:00
parent 4393aa7efb
commit 4c8a02521d
1 changed files with 16 additions and 5 deletions
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21
llvm/lib/Transforms/Scalar/ConstantHoisting.cpp
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@ -350,14 +350,19 @@ void ConstantHoisting::EmitBaseConstants(Function &F, User *U,
}
assert(isa<ConstantExpr>(U) && "Expected a ConstantExpr.");
ConstantExpr *CE = cast<ConstantExpr>(U);
SmallVector<std::pair<Instruction *, Instruction *>, 8> WorkList;
DEBUG(dbgs() << "Visit ConstantExpr " << *CE << '\n');
for (Value::use_iterator UU = CE->use_begin(), E = CE->use_end();
UU != E; ++UU) {
DEBUG(dbgs() << "Check user "; UU->print(dbgs()); dbgs() << '\n');
// We only handel instructions here and won't walk down a ConstantExpr chain
// to replace all ConstExpr with instructions.
if (Instruction *I = dyn_cast<Instruction>(*UU)) {
// Only update constant expressions in the current function.
if (I->getParent()->getParent() != &F)
if (I->getParent()->getParent() != &F) {
DEBUG(dbgs() << "Not in the same function - skip.\n");
continue;
}
Instruction *Mat = Base;
Instruction *InsertBefore = getMatInsertPt(I, DT);
@ -380,12 +385,18 @@ void ConstantHoisting::EmitBaseConstants(Function &F, User *U,
// Use the same debug location as the instruction we are about to update.
ICE->setDebugLoc(I->getDebugLoc());
DEBUG(dbgs() << "Create instruction: " << *ICE << '\n');
DEBUG(dbgs() << "Update: " << *I << '\n');
I->replaceUsesOfWith(CE, ICE);
DEBUG(dbgs() << "To: " << *I << '\n');
WorkList.push_back(std::make_pair(I, ICE));
} else {
DEBUG(dbgs() << "Not an instruction - skip.\n");
}
}
SmallVectorImpl<std::pair<Instruction *, Instruction *> >::iterator I, E;
for (I = WorkList.begin(), E = WorkList.end(); I != E; ++I) {
DEBUG(dbgs() << "Create instruction: " << *I->second << '\n');
DEBUG(dbgs() << "Update: " << *I->first << '\n');
I->first->replaceUsesOfWith(CE, I->second);
DEBUG(dbgs() << "To: " << *I->first << '\n');
}
}
/// \brief Hoist and hide the base constant behind a bitcast and emit