"@string = constant i8 0" is a value i8* string of length zero. Analyze that

correctly in GetStringLength, fixing PR11181!


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@142558 91177308-0d34-0410-b5e6-96231b3b80d8

test/Transforms/SimplifyLibCalls/StrLen.ll

@@ -6,6 +6,7 @@ target datalayout = "e-p:32:32"
 @hello = constant [6 x i8] c"hello\00"		; <[6 x i8]*> [#uses=3]
 @null = constant [1 x i8] zeroinitializer		; <[1 x i8]*> [#uses=3]
 @null_hello = constant [7 x i8] c"\00hello\00"		; <[7 x i8]*> [#uses=1]
+@nullstring = constant i8 0
 
 declare i32 @strlen(i8*)
 
@@ -54,3 +55,8 @@ define i1 @test7() {
 	%ne_null = icmp ne i32 %null_l, 0		; <i1> [#uses=1]
 	ret i1 %ne_null
 }
+
+define i32 @test8() {
+	%len = tail call i32 @strlen(i8* @nullstring) nounwind
+	ret i32 %len
+}