[llvm-commits] [llvm] r141227 - in /llvm/trunk: lib/Transforms/Scalar/SimplifyLibCalls.cpp test/Transforms/SimplifyLibCalls/StrCmp.ll test/Transforms/SimplifyLibCalls/StrNCmp.ll

Eli Friedman eli.friedman at gmail.com
Wed Oct 5 15:27:16 PDT 2011


Author: efriedma
Date: Wed Oct  5 17:27:16 2011
New Revision: 141227

URL: http://llvm.org/viewvc/llvm-project?rev=141227&view=rev
Log:
PR11061: Make simplifylibcalls fold strcmp("", x) correctly.

While I'm here, fix the related issue with strncmp, add some actual tests for strcmp and strncmp, and start using StringRef::compare for constant folding instead of using strcmp/strncmp so that the optimized IR isn't dependent on the host's implementation of strcmp.


Modified:
    llvm/trunk/lib/Transforms/Scalar/SimplifyLibCalls.cpp
    llvm/trunk/test/Transforms/SimplifyLibCalls/StrCmp.ll
    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=141227&r1=141226&r2=141227&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/SimplifyLibCalls.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/SimplifyLibCalls.cpp Wed Oct  5 17:27:16 2011
@@ -338,16 +338,17 @@
     bool HasStr1 = GetConstantStringInfo(Str1P, Str1);
     bool HasStr2 = GetConstantStringInfo(Str2P, Str2);
 
-    if (HasStr1 && Str1.empty()) // strcmp("", x) -> *x
-      return B.CreateZExt(B.CreateLoad(Str2P, "strcmpload"), CI->getType());
-
-    if (HasStr2 && Str2.empty()) // strcmp(x,"") -> *x
-      return B.CreateZExt(B.CreateLoad(Str1P, "strcmpload"), CI->getType());
-
     // strcmp(x, y)  -> cnst  (if both x and y are constant strings)
     if (HasStr1 && HasStr2)
       return ConstantInt::get(CI->getType(),
-                                     strcmp(Str1.c_str(),Str2.c_str()));
+                              StringRef(Str1).compare(Str2));
+
+    if (HasStr1 && Str1.empty()) // strcmp("", x) -> -*x
+      return B.CreateNeg(B.CreateZExt(B.CreateLoad(Str2P, "strcmpload"),
+                                      CI->getType()));
+
+    if (HasStr2 && Str2.empty()) // strcmp(x,"") -> *x
+      return B.CreateZExt(B.CreateLoad(Str1P, "strcmpload"), CI->getType());
 
     // strcmp(P, "x") -> memcmp(P, "x", 2)
     uint64_t Len1 = GetStringLength(Str1P);
@@ -400,16 +401,20 @@
     bool HasStr1 = GetConstantStringInfo(Str1P, Str1);
     bool HasStr2 = GetConstantStringInfo(Str2P, Str2);
 
-    if (HasStr1 && Str1.empty())  // strncmp("", x, n) -> *x
-      return B.CreateZExt(B.CreateLoad(Str2P, "strcmpload"), CI->getType());
+    // strncmp(x, y)  -> cnst  (if both x and y are constant strings)
+    if (HasStr1 && HasStr2) {
+      StringRef SubStr1 = StringRef(Str1).substr(0, Length);
+      StringRef SubStr2 = StringRef(Str2).substr(0, Length);
+      return ConstantInt::get(CI->getType(), SubStr1.compare(SubStr2));
+    }
+
+    if (HasStr1 && Str1.empty())  // strncmp("", x, n) -> -*x
+      return B.CreateNeg(B.CreateZExt(B.CreateLoad(Str2P, "strcmpload"),
+                                      CI->getType()));
 
     if (HasStr2 && Str2.empty())  // strncmp(x, "", n) -> *x
       return B.CreateZExt(B.CreateLoad(Str1P, "strcmpload"), CI->getType());
 
-    // strncmp(x, y)  -> cnst  (if both x and y are constant strings)
-    if (HasStr1 && HasStr2)
-      return ConstantInt::get(CI->getType(),
-                              strncmp(Str1.c_str(), Str2.c_str(), Length));
     return 0;
   }
 };

Modified: llvm/trunk/test/Transforms/SimplifyLibCalls/StrCmp.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/SimplifyLibCalls/StrCmp.ll?rev=141227&r1=141226&r2=141227&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/SimplifyLibCalls/StrCmp.ll (original)
+++ llvm/trunk/test/Transforms/SimplifyLibCalls/StrCmp.ll Wed Oct  5 17:27:16 2011
@@ -1,28 +1,65 @@
 ; Test that the StrCmpOptimizer works correctly
-; RUN: opt < %s -simplify-libcalls -S | \
-; RUN:   not grep {call.*strcmp}
+; RUN: opt < %s -simplify-libcalls -S | FileCheck %s
+
+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"
 
 @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]
+ at bell = constant [5 x i8] c"bell\00"		; <[5 x i8]*> [#uses=1]
 @null = constant [1 x i8] zeroinitializer		; <[1 x i8]*> [#uses=1]
 
 declare i32 @strcmp(i8*, i8*)
 
-declare i32 @puts(i8*)
+; strcmp("", x) -> -*x
+define i32 @test1(i8* %str) {
+  %temp1 = call i32 @strcmp(i8* getelementptr inbounds ([1 x i8]* @null, i32 0, i32 0), i8* %str)
+  ret i32 %temp1
+  ; CHECK: @test1
+  ; CHECK: %strcmpload = load i8* %str
+  ; CHECK: %1 = zext i8 %strcmpload to i32
+  ; CHECK: %temp1 = sub i32 0, %1
+  ; CHECK: ret i32 %temp1
+}
+
+; strcmp(x, "") -> *x
+define i32 @test2(i8* %str) {
+  %temp1 = call i32 @strcmp(i8* %str, i8* getelementptr inbounds ([1 x i8]* @null, i32 0, i32 0))
+  ret i32 %temp1
+  ; CHECK: @test2
+  ; CHECK: %strcmpload = load i8* %str
+  ; CHECK: %temp1 = zext i8 %strcmpload to i32
+  ; CHECK: ret i32 %temp1
+}
+
+; strcmp(x, y)  -> cnst
+define i32 @test3() {
+  %temp1 = call i32 @strcmp(i8* getelementptr inbounds ([5 x i8]* @hell, i32 0, i32 0), i8* getelementptr inbounds ([6 x i8]* @hello, i32 0, i32 0))
+  ret i32 %temp1
+  ; CHECK: @test3
+  ; CHECK: ret i32 -1
+}
+define i32 @test4() {
+  %temp1 = call i32 @strcmp(i8* getelementptr inbounds ([5 x i8]* @hell, i32 0, i32 0), i8* getelementptr inbounds ([1 x i8]* @null, i32 0, i32 0))
+  ret i32 %temp1
+  ; CHECK: @test4
+  ; CHECK: ret i32 1
+}
 
-define i32 @main() {
-	%hello_p = getelementptr [6 x i8]* @hello, i32 0, i32 0		; <i8*> [#uses=5]
-	%hell_p = getelementptr [5 x i8]* @hell, i32 0, i32 0		; <i8*> [#uses=1]
-	%null_p = getelementptr [1 x i8]* @null, i32 0, i32 0		; <i8*> [#uses=4]
-	%temp1 = call i32 @strcmp( i8* %hello_p, i8* %hello_p )		; <i32> [#uses=1]
-	%temp2 = call i32 @strcmp( i8* %null_p, i8* %null_p )		; <i32> [#uses=1]
-	%temp3 = call i32 @strcmp( i8* %hello_p, i8* %null_p )		; <i32> [#uses=1]
-	%temp4 = call i32 @strcmp( i8* %null_p, i8* %hello_p )		; <i32> [#uses=1]
-	%temp5 = call i32 @strcmp( i8* %hell_p, i8* %hello_p )		; <i32> [#uses=1]
-	%rslt1 = add i32 %temp1, %temp2		; <i32> [#uses=1]
-	%rslt2 = add i32 %rslt1, %temp3		; <i32> [#uses=1]
-	%rslt3 = add i32 %rslt2, %temp4		; <i32> [#uses=1]
-	%rslt4 = add i32 %rslt3, %temp5		; <i32> [#uses=1]
-	ret i32 %rslt4
+; strcmp(x, y)   -> memcmp(x, y, <known length>)
+; (This transform is rather difficult to trigger in a useful manner)
+define i32 @test5(i1 %b) {
+  %sel = select i1 %b, i8* getelementptr inbounds ([5 x i8]* @hell, i32 0, i32 0), i8* getelementptr inbounds ([5 x i8]* @bell, i32 0, i32 0)
+  %temp1 = call i32 @strcmp(i8* getelementptr inbounds ([6 x i8]* @hello, i32 0, i32 0), i8* %sel)
+  ret i32 %temp1
+  ; CHECK: @test5
+  ; CHECK: %memcmp = call i32 @memcmp(i8* getelementptr inbounds ([6 x i8]* @hello, i32 0, i32 0), i8* %sel, i32 5)
+  ; CHECK: ret i32 %memcmp
 }
 
+; strcmp(x,x)  -> 0
+define i32 @test6(i8* %str) {
+  %temp1 = call i32 @strcmp(i8* %str, i8* %str)
+  ret i32 %temp1
+  ; CHECK: @test6
+  ; CHECK: ret i32 0
+}

Modified: llvm/trunk/test/Transforms/SimplifyLibCalls/StrNCmp.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/SimplifyLibCalls/StrNCmp.ll?rev=141227&r1=141226&r2=141227&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/SimplifyLibCalls/StrNCmp.ll (original)
+++ llvm/trunk/test/Transforms/SimplifyLibCalls/StrNCmp.ll Wed Oct  5 17:27:16 2011
@@ -1,35 +1,78 @@
-; Test that the StrNCmpOptimizer works correctly
-; RUN: opt < %s -simplify-libcalls -S | \
-; RUN:   not grep {call.*strncmp}
+; Test that the StrCmpOptimizer works correctly
+; RUN: opt < %s -simplify-libcalls -S | FileCheck %s
 
-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"
+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"
 
 @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]
+ at bell = constant [5 x i8] c"bell\00"		; <[5 x i8]*> [#uses=1]
 @null = constant [1 x i8] zeroinitializer		; <[1 x i8]*> [#uses=1]
 
 declare i32 @strncmp(i8*, i8*, i32)
 
-declare i32 @puts(i8*)
+; strcmp("", x) -> -*x
+define i32 @test1(i8* %str) {
+  %temp1 = call i32 @strncmp(i8* getelementptr inbounds ([1 x i8]* @null, i32 0, i32 0), i8* %str, i32 10)
+  ret i32 %temp1
+  ; CHECK: @test1
+  ; CHECK: %strcmpload = load i8* %str
+  ; CHECK: %1 = zext i8 %strcmpload to i32
+  ; CHECK: %temp1 = sub i32 0, %1
+  ; CHECK: ret i32 %temp1
+}
+
+; strcmp(x, "") -> *x
+define i32 @test2(i8* %str) {
+  %temp1 = call i32 @strncmp(i8* %str, i8* getelementptr inbounds ([1 x i8]* @null, i32 0, i32 0), i32 10)
+  ret i32 %temp1
+  ; CHECK: @test2
+  ; CHECK: %strcmpload = load i8* %str
+  ; CHECK: %temp1 = zext i8 %strcmpload to i32
+  ; CHECK: ret i32 %temp1
+}
+
+; strncmp(x, y, n)  -> cnst
+define i32 @test3() {
+  %temp1 = call i32 @strncmp(i8* getelementptr inbounds ([5 x i8]* @hell, i32 0, i32 0), i8* getelementptr inbounds ([6 x i8]* @hello, i32 0, i32 0), i32 10)
+  ret i32 %temp1
+  ; CHECK: @test3
+  ; CHECK: ret i32 -1
+}
+define i32 @test4() {
+  %temp1 = call i32 @strncmp(i8* getelementptr inbounds ([5 x i8]* @hell, i32 0, i32 0), i8* getelementptr inbounds ([1 x i8]* @null, i32 0, i32 0), i32 10)
+  ret i32 %temp1
+  ; CHECK: @test4
+  ; CHECK: ret i32 1
+}
+define i32 @test5() {
+  %temp1 = call i32 @strncmp(i8* getelementptr inbounds ([5 x i8]* @hell, i32 0, i32 0), i8* getelementptr inbounds ([6 x i8]* @hello, i32 0, i32 0), i32 4)
+  ret i32 %temp1
+  ; CHECK: @test5
+  ; CHECK: ret i32 0
+}
+
+; strncmp(x,y,1) -> memcmp(x,y,1)
+define i32 @test6(i8* %str1, i8* %str2) {
+  %temp1 = call i32 @strncmp(i8* %str1, i8* %str2, i32 1)
+  ret i32 %temp1
+  ; CHECK: @test6
+  ; CHECK: load i8*
+  ; CHECK: load i8*
+  ; CHECK: sub i32
+}
+
+; strncmp(x,y,0)   -> 0
+define i32 @test7(i8* %str1, i8* %str2) {
+  %temp1 = call i32 @strncmp(i8* %str1, i8* %str2, i32 0)
+  ret i32 %temp1
+  ; CHECK: @test7
+  ; CHECK: ret i32 0
+}
 
-define i32 @main() {
-	%hello_p = getelementptr [6 x i8]* @hello, i32 0, i32 0		; <i8*> [#uses=5]
-	%hell_p = getelementptr [5 x i8]* @hell, i32 0, i32 0		; <i8*> [#uses=1]
-	%null_p = getelementptr [1 x i8]* @null, i32 0, i32 0		; <i8*> [#uses=4]
-	%temp1 = call i32 @strncmp( i8* %hello_p, i8* %hello_p, i32 5 )		; <i32> [#uses=1]
-	%temp2 = call i32 @strncmp( i8* %null_p, i8* %null_p, i32 0 )		; <i32> [#uses=1]
-	%temp3 = call i32 @strncmp( i8* %hello_p, i8* %null_p, i32 0 )		; <i32> [#uses=1]
-	%temp4 = call i32 @strncmp( i8* %null_p, i8* %hello_p, i32 0 )		; <i32> [#uses=1]
-	%temp5 = call i32 @strncmp( i8* %hell_p, i8* %hello_p, i32 4 )		; <i32> [#uses=1]
-	%rslt1 = add i32 %temp1, %temp2		; <i32> [#uses=1]
-	%rslt2 = add i32 %rslt1, %temp3		; <i32> [#uses=1]
-	%rslt3 = add i32 %rslt2, %temp4		; <i32> [#uses=1]
-	%rslt4 = add i32 %rslt3, %temp5		; <i32> [#uses=1]
-	ret i32 %rslt4
-}
-
-define i32 @test1(i8* %P, i8* %Q) {
-  %cmp = call i32 @strncmp(i8* %P, i8* %Q, i32 1)
-  ret i32 %cmp
+; strncmp(x,x,n)  -> 0
+define i32 @test8(i8* %str, i32 %n) {
+  %temp1 = call i32 @strncmp(i8* %str, i8* %str, i32 %n)
+  ret i32 %temp1
+  ; CHECK: @test8
+  ; CHECK: ret i32 0
 }





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