Switch invars away from using isTrapping when it really shouldn't be

using it.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@75852 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 7 insertions, 1 deletions

diff --git a/lib/Transforms/Scalar/IndVarSimplify.cpp b/lib/Transforms/Scalar/IndVarSimplify.cpp
index 1a6c6a1..0ac58f1 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).