[NewGVN] Fix handling of assumes

This patch fixes two bugs:

* test1: Previously assume(a >= 5) concluded that a == 5. That's only
         valid for assume(a == 5)...
* test2: If operands were swapped, additional users were added to the
         wrong cmp operand. This resulted in an "unsettled iteration"
         assertion failure.

Patch by Nikita Popov

Differential Revision: https://reviews.llvm.org/D46974

llvm-svn: 333007

1 files changed, 4 insertions, 4 deletions

diff --git a/llvm/lib/Transforms/Scalar/NewGVN.cpp b/llvm/lib/Transforms/Scalar/NewGVN.cpp
index 0cf9979b40a..94973c986e9 100644
--- a/llvm/lib/Transforms/Scalar/NewGVN.cpp
+++ b/llvm/lib/Transforms/Scalar/NewGVN.cpp
@@ -1585,11 +1585,11 @@ NewGVN::performSymbolicPredicateInfoEvaluation(Instruction *I) const {
       SwappedOps ? Cmp->getSwappedPredicate() : Cmp->getPredicate();
 
   if (isa<PredicateAssume>(PI)) {
-    // If the comparison is true when the operands are equal, then we know the
-    // operands are equal, because assumes must always be true.
-    if (CmpInst::isTrueWhenEqual(Predicate)) {
+    // If we assume the operands are equal, then they are equal.
+    if (Predicate == CmpInst::ICMP_EQ) {
       addPredicateUsers(PI, I);
-      addAdditionalUsers(Cmp->getOperand(0), I);
+      addAdditionalUsers(SwappedOps ? Cmp->getOperand(1) : Cmp->getOperand(0),
+                         I);
       return createVariableOrConstant(FirstOp);
     }
   }