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Code size optimisation: don't rewrite fputs to fwrite when optimising for size

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because fwrite requires more arguments and thus extra MOVs are required.

llvm-svn: 274753
This commit is contained in:
Sjoerd Meijer 2016-07-07 13:56:23 +00:00
parent a251b41b25
commit fade1bf838
2 changed files with 30 additions and 0 deletions
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2
lib/Transforms/Utils/SimplifyLibCalls.cpp
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@ -2056,6 +2056,8 @@ Value *LibCallSimplifier::optimizeCall(CallInst *CI) {
case LibFunc::fwrite:
return optimizeFWrite(CI, Builder);
case LibFunc::fputs:
if (CI->getParent()->getParent()->optForSize())
return nullptr;
return optimizeFPuts(CI, Builder);
case LibFunc::log:
case LibFunc::log10:

28
test/Transforms/InstCombine/fputs-opt-size.ll Normal file
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@ -0,0 +1,28 @@
; When optimising for size, we don't want to rewrite fputs to fwrite
; because it requires more arguments and thus extra MOVs are required.
;
; RUN: opt < %s -instcombine -S | FileCheck %s
%struct._IO_FILE = type { i32, i8*, i8*, i8*, i8*, i8*, i8*, i8*, i8*, i8*, i8*, i8*, %struct._IO_marker*, %struct._IO_FILE*, i32, i32, i32, i16, i8, [1 x i8], i8*, i64, i8*, i8*, i8*, i8*, i32, i32, [40 x i8] }
%struct._IO_marker = type { %struct._IO_marker*, %struct._IO_FILE*, i32 }
@.str = private unnamed_addr constant [10 x i8] c"mylog.txt\00", align 1
@.str.1 = private unnamed_addr constant [2 x i8] c"a\00", align 1
@.str.2 = private unnamed_addr constant [27 x i8] c"Hello world this is a test\00", align 1
define i32 @main() local_unnamed_addr #0 {
entry:
; CHECK-LABEL: @main(
; CHECK-NOT: call i64 @fwrite
; CHECK: call i32 @fputs
%call = tail call %struct._IO_FILE* @fopen(i8* getelementptr inbounds ([10 x i8], [10 x i8]* @.str, i32 0, i32 0), i8* getelementptr inbounds ([2 x i8], [2 x i8]* @.str.1, i32 0, i32 0)) #2
%call1 = tail call i32 @fputs(i8* getelementptr inbounds ([27 x i8], [27 x i8]* @.str.2, i32 0, i32 0), %struct._IO_FILE* %call) #2
ret i32 0
}
declare noalias %struct._IO_FILE* @fopen(i8* nocapture readonly, i8* nocapture readonly) local_unnamed_addr #1
declare i32 @fputs(i8* nocapture readonly, %struct._IO_FILE* nocapture) local_unnamed_addr #1
attributes #0 = { nounwind optsize }
attributes #1 = { nounwind optsize }