[SimplifyLibCalls] Add a test to make sure we lower fls(0) correctly.

llvm-svn: 289895

diff --git a/llvm/test/Transforms/InstCombine/fls.ll b/llvm/test/Transforms/InstCombine/fls.ll
index bf608b3..9ccc56a 100644 (file)
--- a/llvm/test/Transforms/InstCombine/fls.ll
+++ b/llvm/test/Transforms/InstCombine/fls.ll
@@ -43,6 +43,15 @@ define i32 @flsnotconst(i64 %z) {
   ret i32 %goo
 }
 
+; Make sure we lower fls(0) to 0 and not to `undef`.
+; CHECK-LABEL: define i32 @flszero(
+; CHECK: ret i32 0
+; CHECK: }
+define i32 @flszero() {
+  %zero = call i32 @fls(i32 0)
+  ret i32 %zero
+}
+
 declare i32 @fls(i32)
 declare i32 @flsl(i64)
 declare i32 @flsll(i64)