[llvm-commits] [llvm] r106097 - in /llvm/trunk: lib/Transforms/Scalar/SimplifyLibCalls.cpp test/Transforms/SimplifyLibCalls/StrNCmp.ll

[Benjamin Kramer]

Author: d0k
Date: Wed Jun 16 05:30:29 2010
New Revision: 106097

URL: http://llvm.org/viewvc/llvm-project?rev=106097&view=rev
Log:
simplify-libcalls: fold strncmp(x, y, 1) -> memcmp(x, y, 1)

The memcmp will be optimized further and even the pathological case
'strstr(x, "x") == x' generates optimal code now.

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

Modified: llvm/trunk/lib/Transforms/Scalar/SimplifyLibCalls.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/SimplifyLibCalls.cpp?rev=106097&r1=106096&r2=106097&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/SimplifyLibCalls.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/SimplifyLibCalls.cpp Wed Jun 16 05:30:29 2010
@@ -342,6 +342,9 @@
     if (Length == 0) // strncmp(x,y,0)   -> 0
       return ConstantInt::get(CI->getType(), 0);
 
+    if (TD && Length == 1) // strncmp(x,y,1) -> memcmp(x,y,1)
+      return EmitMemCmp(Str1P, Str2P, CI->getOperand(3), B, TD);
+
     std::string Str1, Str2;
     bool HasStr1 = GetConstantStringInfo(Str1P, Str1);
     bool HasStr2 = GetConstantStringInfo(Str2P, Str2);

Modified: llvm/trunk/test/Transforms/SimplifyLibCalls/StrNCmp.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/SimplifyLibCalls/StrNCmp.ll?rev=106097&r1=106096&r2=106097&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/SimplifyLibCalls/StrNCmp.ll (original)
+++ llvm/trunk/test/Transforms/SimplifyLibCalls/StrNCmp.ll Wed Jun 16 05:30:29 2010
@@ -2,6 +2,9 @@
 ; RUN: opt < %s -simplify-libcalls -S | \
 ; RUN:   not grep {call.*strncmp}
 
+target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:128:128-n8:16:32"
+target triple = "i386-apple-darwin9.0"
+
 @hello = constant [6 x i8] c"hello\00"		; <[6 x i8]*> [#uses=1]
 @hell = constant [5 x i8] c"hell\00"		; <[5 x i8]*> [#uses=1]
 @null = constant [1 x i8] zeroinitializer		; <[1 x i8]*> [#uses=1]
@@ -26,3 +29,7 @@
 	ret i32 %rslt4
 }
 
+define i32 @test1(i8* %P, i8* %Q) {
+  %cmp = call i32 @strncmp(i8* %P, i8* %Q, i32 1)
+  ret i32 %cmp
+}