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Fix a case where SROA did not correctly detect dead PHI or selects due

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to chains or cycles between PHIs and/or selects. Also add a couple of
really nice test cases reduced from Kostya's reports in PR13905 and
PR13906. Both are fixed by this patch.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@164596 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chandler Carruth
2012-09-25 10:03:40 +00:00
parent 00edf4c1d8
commit c303463dcc
2 changed files with 55 additions and 5 deletions
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15
lib/Transforms/Scalar/SROA.cpp
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@@ -522,8 +522,10 @@ private:
void insertUse(Instruction &I, int64_t Offset, uint64_t Size,
bool IsSplittable = false) {
// Completely skip uses which don't overlap the allocation.
if ((Offset >= 0 && (uint64_t)Offset >= AllocSize) ||
// Completely skip uses which have a zero size or don't overlap the
// allocation.
if (Size == 0 ||
(Offset >= 0 && (uint64_t)Offset >= AllocSize) ||
(Offset < 0 && (uint64_t)-Offset >= Size)) {
DEBUG(dbgs() << "WARNING: Ignoring " << Size << " byte use @" << Offset
<< " which starts past the end of the " << AllocSize
@@ -697,6 +699,9 @@ private:
SmallVector<std::pair<Instruction *, Instruction *>, 4> Uses;
Visited.insert(Root);
Uses.push_back(std::make_pair(cast<Instruction>(*U), Root));
// If there are no loads or stores, the access is dead. We mark that as
// a size zero access.
Size = 0;
do {
Instruction *I, *UsedI;
llvm::tie(UsedI, I) = Uses.pop_back_val();
@@ -824,9 +829,9 @@ private:
}
void insertUse(Instruction &User, int64_t Offset, uint64_t Size) {
// If the use extends outside of the allocation, record it as a dead use
// for elimination later.
if ((uint64_t)Offset >= AllocSize ||
// If the use has a zero size or extends outside of the allocation, record
// it as a dead use for elimination later.
if (Size == 0 || (uint64_t)Offset >= AllocSize ||
(Offset < 0 && (uint64_t)-Offset >= Size))
return markAsDead(User);