Fix PR2496, a really nasty bug which involved sinking volatile loads
into phis. This is actually the same bug as PR2262 /
2008-04-29-VolatileLoadDontMerge.ll, but I missed checking the first
predecessor for multiple successors. Testcase here:
InstCombine/2008-07-08-VolatileLoadMerge.ll
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@53240 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp
index 8bc9091..f8ad98c 100644
--- a/lib/Transforms/Scalar/InstructionCombining.cpp
+++ b/lib/Transforms/Scalar/InstructionCombining.cpp
@@ -9354,6 +9354,14 @@
if (LI->getParent() != PN.getIncomingBlock(0) ||
!isSafeToSinkLoad(LI))
return 0;
+
+ // If the PHI is of volatile loads and the load block has multiple
+ // successors, sinking it would remove a load of the volatile value from
+ // the path through the other successor.
+ if (isVolatile &&
+ LI->getParent()->getTerminator()->getNumSuccessors() != 1)
+ return 0;
+
} else if (isa<GetElementPtrInst>(FirstInst)) {
if (FirstInst->getNumOperands() == 2)
return FoldPHIArgBinOpIntoPHI(PN);
@@ -9380,9 +9388,9 @@
!isSafeToSinkLoad(LI))
return 0;
- // If the PHI is volatile and its block has multiple successors, sinking
- // it would remove a load of the volatile value from the path through the
- // other successor.
+ // If the PHI is of volatile loads and the load block has multiple
+ // successors, sinking it would remove a load of the volatile value from
+ // the path through the other successor.
if (isVolatile &&
LI->getParent()->getTerminator()->getNumSuccessors() != 1)
return 0;