[llvm-commits] [llvm] r104648 - in /llvm/trunk: lib/Transforms/Scalar/SimplifyLibCalls.cpp test/Transforms/SimplifyLibCalls/memcmp.ll

[Benjamin Kramer]

Author: d0k
Date: Tue May 25 17:53:43 2010
New Revision: 104648

URL: http://llvm.org/viewvc/llvm-project?rev=104648&view=rev
Log:
Properly promote operands when optimizing a single-character memcmp.

Modified:
    llvm/trunk/lib/Transforms/Scalar/SimplifyLibCalls.cpp
    llvm/trunk/test/Transforms/SimplifyLibCalls/memcmp.ll

Modified: llvm/trunk/lib/Transforms/Scalar/SimplifyLibCalls.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/SimplifyLibCalls.cpp?rev=104648&r1=104647&r2=104648&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/SimplifyLibCalls.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/SimplifyLibCalls.cpp Tue May 25 17:53:43 2010
@@ -558,9 +558,12 @@
     if (Len == 0) // memcmp(s1,s2,0) -> 0
       return Constant::getNullValue(CI->getType());
 
-    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");
+    // memcmp(S1,S2,1) -> *(unsigned char*)LHS - *(unsigned char*)RHS
+    if (Len == 1) {
+      Value *LHSV = B.CreateZExt(B.CreateLoad(CastToCStr(LHS, B), "lhsc"),
+                                 CI->getType(), "lhsv");
+      Value *RHSV = B.CreateZExt(B.CreateLoad(CastToCStr(RHS, B), "rhsc"),
+                                 CI->getType(), "rhsv");
       return B.CreateSExt(B.CreateSub(LHSV, RHSV, "chardiff"), CI->getType());
     }
 

Modified: llvm/trunk/test/Transforms/SimplifyLibCalls/memcmp.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/SimplifyLibCalls/memcmp.ll?rev=104648&r1=104647&r2=104648&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/SimplifyLibCalls/memcmp.ll (original)
+++ llvm/trunk/test/Transforms/SimplifyLibCalls/memcmp.ll Tue May 25 17:53:43 2010
@@ -1,5 +1,5 @@
 ; Test that the memcmpOptimizer works correctly
-; RUN: opt < %s -simplify-libcalls -S | not grep {call.*memcmp}
+; RUN: opt < %s -simplify-libcalls -S | FileCheck %s
 
 @h = constant [2 x i8] c"h\00"		; <[2 x i8]*> [#uses=0]
 @hel = constant [4 x i8] c"hel\00"		; <[4 x i8]*> [#uses=0]
@@ -9,14 +9,26 @@
 
 define void @test(i8* %P, i8* %Q, i32 %N, i32* %IP, i1* %BP) {
 	%A = call i32 @memcmp( i8* %P, i8* %P, i32 %N )		; <i32> [#uses=1]
+; CHECK-NOT: call {{.*}} memcmp
+; CHECK: volatile store
 	volatile store i32 %A, i32* %IP
 	%B = call i32 @memcmp( i8* %P, i8* %Q, i32 0 )		; <i32> [#uses=1]
+; CHECK-NOT: call {{.*}} memcmp
+; CHECK: volatile store
 	volatile store i32 %B, i32* %IP
 	%C = call i32 @memcmp( i8* %P, i8* %Q, i32 1 )		; <i32> [#uses=1]
+; CHECK: load
+; CHECK: zext
+; CHECK: load
+; CHECK: zext
+; CHECK: sub
+; CHECK: volatile store
 	volatile store i32 %C, i32* %IP
         %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)
+; CHECK-NOT: call {{.*}} memcmp
+; CHECK: volatile store
         volatile store i32 %F, i32* %IP
 	ret void
 }