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Sink the return instruction collection until after we're done deleting

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dead code, including dead return instructions in some cases. Otherwise,
we end up having a bogus poniter to a return instruction that blows up
much further down the road.

It turns out that this pattern is both simpler to code, easier to update
in the face of enhancements to the inliner cleanup, and likely cheaper
given that it won't add dead instructions to the list.

Thanks to John Regehr's numerous test cases for teasing this out.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@154157 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chandler Carruth
2012-04-06 01:11:52 +00:00
parent f16936e592
commit 6bbab86af9
2 changed files with 46 additions and 7 deletions
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16
lib/Transforms/Utils/CloneFunction.cpp
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@ -200,7 +200,6 @@ namespace {
const Function *OldFunc;
ValueToValueMapTy &VMap;
bool ModuleLevelChanges;
SmallVectorImpl<ReturnInst*> &Returns;
const char *NameSuffix;
ClonedCodeInfo *CodeInfo;
const TargetData *TD;
@ -208,13 +207,12 @@ namespace {
PruningFunctionCloner(Function *newFunc, const Function *oldFunc,
ValueToValueMapTy &valueMap,
bool moduleLevelChanges,
SmallVectorImpl<ReturnInst*> &returns,
const char *nameSuffix,
ClonedCodeInfo *codeInfo,
const TargetData *td)
: NewFunc(newFunc), OldFunc(oldFunc),
VMap(valueMap), ModuleLevelChanges(moduleLevelChanges),
Returns(returns), NameSuffix(nameSuffix), CodeInfo(codeInfo), TD(td) {
NameSuffix(nameSuffix), CodeInfo(codeInfo), TD(td) {
}
/// CloneBlock - The specified block is found to be reachable, clone it and
@ -352,9 +350,6 @@ void PruningFunctionCloner::CloneBlock(const BasicBlock *BB,
CodeInfo->ContainsDynamicAllocas |= hasStaticAllocas &&
BB != &BB->getParent()->front();
}
if (ReturnInst *RI = dyn_cast<ReturnInst>(NewBB->getTerminator()))
Returns.push_back(RI);
}
/// CloneAndPruneFunctionInto - This works exactly like CloneFunctionInto,
@ -381,7 +376,7 @@ void llvm::CloneAndPruneFunctionInto(Function *NewFunc, const Function *OldFunc,
#endif
PruningFunctionCloner PFC(NewFunc, OldFunc, VMap, ModuleLevelChanges,
Returns, NameSuffix, CodeInfo, TD);
NameSuffix, CodeInfo, TD);
// Clone the entry block, and anything recursively reachable from it.
std::vector<const BasicBlock*> CloneWorklist;
@ -537,6 +532,13 @@ void llvm::CloneAndPruneFunctionInto(Function *NewFunc, const Function *OldFunc,
// and we still want to prune the dead code as early as possible.
ConstantFoldTerminator(I);
// Track all of the newly-inserted returns.
if (ReturnInst *RI = dyn_cast<ReturnInst>(I->getTerminator())) {
Returns.push_back(RI);
++I;
continue;
}
BranchInst *BI = dyn_cast<BranchInst>(I->getTerminator());
if (!BI || BI->isConditional()) { ++I; continue; }