[InstCombine] weaken assertions for icmp folds (PR35846)
Because of potential UB (known bits conflicts with an llvm.assume),
we have to check rather than assert here because InstSimplify doesn't
kill the compare:
https://bugs.llvm.org/show_bug.cgi?id=35846
llvm-svn: 322104
diff --git a/llvm/test/Transforms/InstCombine/assume.ll b/llvm/test/Transforms/InstCombine/assume.ll
index 13fa633..7016dfc 100644
--- a/llvm/test/Transforms/InstCombine/assume.ll
+++ b/llvm/test/Transforms/InstCombine/assume.ll
@@ -275,6 +275,23 @@
ret i1 %rval
}
+; PR35846 - https://bugs.llvm.org/show_bug.cgi?id=35846
+
+define i32 @assumption_conflicts_with_known_bits(i32 %a, i32 %b) {
+; CHECK-LABEL: @assumption_conflicts_with_known_bits(
+; CHECK-NEXT: tail call void @llvm.assume(i1 false)
+; CHECK-NEXT: ret i32 0
+;
+ %and1 = and i32 %b, 3
+ %B1 = lshr i32 %and1, %and1
+ %B3 = shl nuw nsw i32 %and1, %B1
+ %cmp = icmp eq i32 %B3, 1
+ tail call void @llvm.assume(i1 %cmp)
+ %cmp2 = icmp eq i32 %B1, %B3
+ tail call void @llvm.assume(i1 %cmp2)
+ ret i32 %and1
+}
+
attributes #0 = { nounwind uwtable }
attributes #1 = { nounwind }