diff options
Diffstat (limited to 'lib')
| -rw-r--r-- | lib/Transforms/Scalar/IndVarSimplify.cpp | 8 |
1 files changed, 7 insertions, 1 deletions
diff --git a/lib/Transforms/Scalar/IndVarSimplify.cpp b/lib/Transforms/Scalar/IndVarSimplify.cpp index 1a6c6a1321..0ac58f1fea 100644 --- a/lib/Transforms/Scalar/IndVarSimplify.cpp +++ b/lib/Transforms/Scalar/IndVarSimplify.cpp @@ -544,7 +544,13 @@ void IndVarSimplify::SinkUnusedInvariants(Loop *L) { // New instructions were inserted at the end of the preheader. if (isa<PHINode>(I)) break; - if (I->isTrapping()) + // Don't move instructions which might have side effects, since the side + // effects need to complete before instructions inside the loop. Also + // don't move instructions which might read memory, since the loop may + // modify memory. Note that it's okay if the instruction might have + // undefined behavior: LoopSimplify guarantees that the preheader + // dominates the exit block. + if (I->mayHaveSideEffects() || I->mayReadFromMemory()) continue; // Determine if there is a use in or before the loop (direct or // otherwise). |