[llvm] r199771 - [SROA] Fix a bug which could cause the common type finding to return
Chandler Carruth
chandlerc at gmail.com
Tue Jan 21 15:16:05 PST 2014
Author: chandlerc
Date: Tue Jan 21 17:16:05 2014
New Revision: 199771
URL: http://llvm.org/viewvc/llvm-project?rev=199771&view=rev
Log:
[SROA] Fix a bug which could cause the common type finding to return
inconsistent results for different orderings of alloca slices. The
fundamental issue is that it is just always a mistake to return early
from this function. There is no effective early exit to leverage. This
patch stops trynig to do so and simplifies the code a bit as
a consequence.
Original diagnosis and patch by James Molloy with some name tweaks by me
in part reflecting feedback from Duncan Smith on the mailing list.
Modified:
llvm/trunk/lib/Transforms/Scalar/SROA.cpp
Modified: llvm/trunk/lib/Transforms/Scalar/SROA.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/SROA.cpp?rev=199771&r1=199770&r2=199771&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/SROA.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/SROA.cpp Tue Jan 21 17:16:05 2014
@@ -957,7 +957,11 @@ static Type *findCommonType(AllocaSlices
AllocaSlices::const_iterator E,
uint64_t EndOffset) {
Type *Ty = 0;
- bool IgnoreNonIntegralTypes = false;
+ bool TyIsCommon = true;
+ IntegerType *ITy = 0;
+
+ // Note that we need to look at *every* alloca slice's Use to ensure we
+ // always get consistent results regardless of the order of slices.
for (AllocaSlices::const_iterator I = B; I != E; ++I) {
Use *U = I->getUse();
if (isa<IntrinsicInst>(*U->getUser()))
@@ -970,37 +974,30 @@ static Type *findCommonType(AllocaSlices
UserTy = LI->getType();
} else if (StoreInst *SI = dyn_cast<StoreInst>(U->getUser())) {
UserTy = SI->getValueOperand()->getType();
- } else {
- IgnoreNonIntegralTypes = true; // Give up on anything but an iN type.
- continue;
}
- if (IntegerType *ITy = dyn_cast<IntegerType>(UserTy)) {
+ if (!UserTy || (Ty && Ty != UserTy))
+ TyIsCommon = false; // Give up on anything but an iN type.
+ else
+ Ty = UserTy;
+
+ if (IntegerType *UserITy = dyn_cast_or_null<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. Also skip if the type is not a byte width
// multiple.
- if (ITy->getBitWidth() % 8 != 0 ||
- ITy->getBitWidth() / 8 > (EndOffset - B->beginOffset()))
+ if (UserITy->getBitWidth() % 8 != 0 ||
+ UserITy->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.
- //
- // 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;
+ // Track the largest bitwidth integer type used in this way in case there
+ // is no common type.
+ if (!ITy || ITy->getBitWidth() < UserITy->getBitWidth())
+ ITy = UserITy;
}
-
- if (Ty && Ty != UserTy)
- IgnoreNonIntegralTypes = true; // Give up on anything but an iN type.
-
- Ty = UserTy;
}
- return Ty;
+
+ return TyIsCommon ? Ty : ITy;
}
/// PHI instructions that use an alloca and are subsequently loaded can be
More information about the llvm-commits
mailing list