From: Chris Lattner <sabre@nondot.org>
Date: Sat, 30 May 2009 18:43:04 +0000 (+0000)
Subject: fix PR4284, a bug in simplifylibcalls handling memcmp.  Patch by
X-Git-Url: http://plrg.eecs.uci.edu/git/?a=commitdiff_plain;h=0e98e4d299e76ab627d53c976f0f84b449106d15;p=oota-llvm.git

fix PR4284, a bug in simplifylibcalls handling memcmp.  Patch by
Benjamin Kramer!


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@72625 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Transforms/Scalar/SimplifyLibCalls.cpp b/lib/Transforms/Scalar/SimplifyLibCalls.cpp
index 8c41c728c06..4b0064090cf 100644
--- a/lib/Transforms/Scalar/SimplifyLibCalls.cpp
+++ b/lib/Transforms/Scalar/SimplifyLibCalls.cpp
@@ -878,7 +878,7 @@ struct VISIBILITY_HIDDEN MemCmpOpt : public LibCallOptimization {
     if (Len == 1) { // memcmp(S1,S2,1) -> *LHS - *RHS
       Value *LHSV = B.CreateLoad(CastToCStr(LHS, B), "lhsv");
       Value *RHSV = B.CreateLoad(CastToCStr(RHS, B), "rhsv");
-      return B.CreateZExt(B.CreateSub(LHSV, RHSV, "chardiff"), CI->getType());
+      return B.CreateSExt(B.CreateSub(LHSV, RHSV, "chardiff"), CI->getType());
     }
 
     // memcmp(S1,S2,2) != 0 -> (*(short*)LHS ^ *(short*)RHS)  != 0
diff --git a/test/Transforms/SimplifyLibCalls/2009-05-30-memcmp-byte.ll b/test/Transforms/SimplifyLibCalls/2009-05-30-memcmp-byte.ll
new file mode 100644
index 00000000000..f7209934f76
--- /dev/null
+++ b/test/Transforms/SimplifyLibCalls/2009-05-30-memcmp-byte.ll
@@ -0,0 +1,14 @@
+; RUN: llvm-as < %s | opt -simplify-libcalls -instcombine | llvm-dis | grep {ret i32 -65}
+; PR4284
+
+define i32 @test() nounwind {
+entry:
+	%c0 = alloca i8, align 1		; <i8*> [#uses=2]
+	%c2 = alloca i8, align 1		; <i8*> [#uses=2]
+	store i8 64, i8* %c0
+	store i8 -127, i8* %c2
+	%call = call i32 @memcmp(i8* %c0, i8* %c2, i32 1)		; <i32> [#uses=1]
+	ret i32 %call
+}
+
+declare i32 @memcmp(i8*, i8*, i32)