Teach SimplifyLibCalls to fold memcmp calls with constant arguments.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86141 91177308-0d34-0410-b5e6-96231b3b80d8

test/Transforms/SimplifyLibCalls/memcmp.ll

@@ -17,6 +17,10 @@ define void @test(i8* %P, i8* %Q, i32 %N, i32* %IP, i1* %BP) {
 	%D = call i32 @memcmp( i8* %P, i8* %Q, i32 2 )		; <i32> [#uses=1]
 	%E = icmp eq i32 %D, 0		; <i1> [#uses=1]
 	volatile store i1 %E, i1* %BP
+        %F = call i32 @memcmp(i8* getelementptr ([4 x i8]* @hel, i32 0, i32 0),
+                              i8* getelementptr ([8 x i8]* @hello_u, i32 0, i32 0),
+                              i32 3)
+        volatile store i32 %F, i32* %IP
 	ret void
 }