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authorBill Wendling <isanbard@gmail.com>2013-11-20 06:15:56 +0000
committerBill Wendling <isanbard@gmail.com>2013-11-20 06:15:56 +0000
commit43f41cc550e74346f927dc45cb82c57ddcf07117 (patch)
tree6d709abfcc8d887395cf3aff6d829337a3764020 /lib/Transforms
parentd20d4e58d91ce99a78b71af070bee327896b2366 (diff)
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Merging r195118:
------------------------------------------------------------------------ r195118 | chandlerc | 2013-11-19 01:03:18 -0800 (Tue, 19 Nov 2013) | 22 lines Fix an issue where SROA computed different results based on the relative order of slices of the alloca which have exactly the same size and other properties. This was found by a perniciously unstable sort implementation used to flush out buggy uses of the algorithm. The fundamental idea is that findCommonType should return the best common type it can find across all of the slices in the range. There were two bugs here previously: 1) We would accept an integer type smaller than a byte-width multiple, and if there were different bit-width integer types, we would accept the first one. This caused an actual failure in the testcase updated here when the sort order changed. 2) If we found a bad combination of types or a non-load, non-store use before an integer typed load or store we would bail, but if we found the integere typed load or store, we would use it. The correct behavior is to always use an integer typed operation which covers the partition if one exists. While a clever debugging sort algorithm found problem #1 in our existing test cases, I have no useful test case ideas for #2. I spotted in by inspection when looking at this code. ------------------------------------------------------------------------ git-svn-id: https://llvm.org/svn/llvm-project/llvm/branches/release_34@195217 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'lib/Transforms')
-rw-r--r--lib/Transforms/Scalar/SROA.cpp29
1 files changed, 19 insertions, 10 deletions
diff --git a/lib/Transforms/Scalar/SROA.cpp b/lib/Transforms/Scalar/SROA.cpp
index a0be2c6..9f3fc83 100644
--- a/lib/Transforms/Scalar/SROA.cpp
+++ b/lib/Transforms/Scalar/SROA.cpp
@@ -938,6 +938,7 @@ static Type *findCommonType(AllocaSlices::const_iterator B,
AllocaSlices::const_iterator E,
uint64_t EndOffset) {
Type *Ty = 0;
+ bool IgnoreNonIntegralTypes = false;
for (AllocaSlices::const_iterator I = B; I != E; ++I) {
Use *U = I->getUse();
if (isa<IntrinsicInst>(*U->getUser()))
@@ -946,29 +947,37 @@ static Type *findCommonType(AllocaSlices::const_iterator B,
continue;
Type *UserTy = 0;
- if (LoadInst *LI = dyn_cast<LoadInst>(U->getUser()))
+ if (LoadInst *LI = dyn_cast<LoadInst>(U->getUser())) {
UserTy = LI->getType();
- else if (StoreInst *SI = dyn_cast<StoreInst>(U->getUser()))
+ } else if (StoreInst *SI = dyn_cast<StoreInst>(U->getUser())) {
UserTy = SI->getValueOperand()->getType();
- else
- return 0; // Bail if we have weird uses.
+ } else {
+ IgnoreNonIntegralTypes = true; // Give up on anything but an iN type.
+ continue;
+ }
if (IntegerType *ITy = dyn_cast<IntegerType>(UserTy)) {
// If the type is larger than the partition, skip it. We only encounter
// this for split integer operations where we want to use the type of the
- // entity causing the split.
- if (ITy->getBitWidth() / 8 > (EndOffset - B->beginOffset()))
+ // entity causing the split. Also skip if the type is not a byte width
+ // multiple.
+ if (ITy->getBitWidth() % 8 != 0 ||
+ ITy->getBitWidth() / 8 > (EndOffset - B->beginOffset()))
continue;
// If we have found an integer type use covering the alloca, use that
- // regardless of the other types, as integers are often used for a
- // "bucket
- // of bits" type.
+ // regardless of the other types, as integers are often used for
+ // a "bucket of bits" type.
+ //
+ // NB: This *must* be the only return from inside the loop so that the
+ // order of slices doesn't impact the computed type.
return ITy;
+ } else if (IgnoreNonIntegralTypes) {
+ continue;
}
if (Ty && Ty != UserTy)
- return 0;
+ IgnoreNonIntegralTypes = true; // Give up on anything but an iN type.
Ty = UserTy;
}