[llvm] r176766 - TLI: Microoptimize calls to strlen+memcmp to strncmp.
Anton Yartsev
anton.yartsev at gmail.com
Wed Mar 13 07:04:23 PDT 2013
On 13.03.2013 17:52, Benjamin Kramer wrote:
> On 13.03.2013, at 14:42, Anton Yartsev <anton.yartsev at gmail.com> wrote:
>
>> Hi Benjamin,
>>
>> I failed to compile Clang after this change. VS2008 complains:
> Does r176946 help? This behavior of MSVC violates C++03 and is really annoying :(
Now compiles, thanks!
>
> - Ben
>
>> 1>------ Build started: Project: LLVMTarget, Configuration: Debug Win32 ------
>> 1>Compiling...
>> 1>TargetLibraryInfo.cpp
>> 1>C:\Program Files\Microsoft Visual Studio 9.0\VC\include\xutility(346) : error C2666: '`anonymous-namespace'::StringComparator::operator ()' : 3 overloads have similar conversions
>> 1> ..\..\..\lib\Target\TargetLibraryInfo.cpp(604): could be 'bool `anonymous-namespace'::StringComparator::operator ()(const char *,llvm::StringRef) const'
>> 1> ..\..\..\lib\Target\TargetLibraryInfo.cpp(611): or 'bool `anonymous-namespace'::StringComparator::operator ()(llvm::StringRef,const char *) const'
>> 1> ..\..\..\lib\Target\TargetLibraryInfo.cpp(612): or 'bool `anonymous-namespace'::StringComparator::operator ()(llvm::StringRef,llvm::StringRef) const'
>> 1> while trying to match the argument list '(const char *, const char *)'
>> 1> C:\Program Files\Microsoft Visual Studio 9.0\VC\include\xutility(1699) : see reference to function template instantiation 'bool std::_Debug_lt_pred<_Pr,const char*,const char*>(_Pr,_Ty1 &,_Ty2 &,const wchar_t *,unsigned int)' being compiled
>> 1> with
>> 1> [
>> 1> _Pr=`anonymous-namespace'::StringComparator,
>> 1> _Ty1=const char *,
>> 1> _Ty2=const char *
>> 1> ]
>> 1> C:\Program Files\Microsoft Visual Studio 9.0\VC\include\xutility(1709) : see reference to function template instantiation 'void std::_Debug_order_single2<_InIt,_Pr>(_FwdIt,_FwdIt,_Pr,bool,const wchar_t *,unsigned int,std::forward_iterator_tag)' being compiled
>> 1> with
>> 1> [
>> 1> _InIt=const char **,
>> 1> _Pr=`anonymous-namespace'::StringComparator,
>> 1> _FwdIt=const char **
>> 1> ]
>> 1> C:\Program Files\Microsoft Visual Studio 9.0\VC\include\algorithm(2290) : see reference to function template instantiation 'void std::_Debug_order_single<_FwdIt,_Pr>(_InIt,_InIt,_Pr,bool,const wchar_t *,unsigned int)' being compiled
>> 1> with
>> 1> [
>> 1> _FwdIt=const char **,
>> 1> _Pr=`anonymous-namespace'::StringComparator,
>> 1> _InIt=const char **
>> 1> ]
>> 1> C:\Program Files\Microsoft Visual Studio 9.0\VC\include\algorithm(2314) : see reference to function template instantiation '_FwdIt std::_Lower_bound<const char**,_Ty,std::iterator_traits<_Iter>::difference_type,_Pr>(_FwdIt,_FwdIt,const _Ty &,_Pr,_Diff *)' being compiled
>> 1> with
>> 1> [
>> 1> _FwdIt=const char **,
>> 1> _Ty=llvm::StringRef,
>> 1> _Iter=const char **,
>> 1> _Pr=`anonymous-namespace'::StringComparator,
>> 1> _Diff=std::iterator_traits<const char **>::difference_type
>> 1> ]
>> 1> ..\..\..\lib\Target\TargetLibraryInfo.cpp(630) : see reference to function template instantiation '_FwdIt std::lower_bound<const char**,llvm::StringRef,`anonymous-namespace'::StringComparator>(_FwdIt,_FwdIt,const _Ty &,_Pr)' being compiled
>> 1> with
>> 1> [
>> 1> _FwdIt=const char **,
>> 1> _Ty=llvm::StringRef,
>> 1> _Pr=`anonymous-namespace'::StringComparator
>> 1> ]
>> 1>C:\Program Files\Microsoft Visual Studio 9.0\VC\include\xutility(348) : error C2666: '`anonymous-namespace'::StringComparator::operator ()' : 3 overloads have similar conversions
>> 1> ..\..\..\lib\Target\TargetLibraryInfo.cpp(604): could be 'bool `anonymous-namespace'::StringComparator::operator ()(const char *,llvm::StringRef) const'
>> 1> ..\..\..\lib\Target\TargetLibraryInfo.cpp(611): or 'bool `anonymous-namespace'::StringComparator::operator ()(llvm::StringRef,const char *) const'
>> 1> ..\..\..\lib\Target\TargetLibraryInfo.cpp(612): or 'bool `anonymous-namespace'::StringComparator::operator ()(llvm::StringRef,llvm::StringRef) const'
>> 1> while trying to match the argument list '(const char *, const char *)'
>> 1>Build log was saved at "file://f:\llvm_COMMON\-VS_build-\lib\Target\LLVMTarget.dir\Debug\BuildLog.htm"
>> 1>LLVMTarget - 2 error(s), 0 warning(s)
>>
>>> Author: d0k
>>> Date: Sat Mar 9 07:48:23 2013
>>> New Revision: 176766
>>>
>>> URL: http://llvm.org/viewvc/llvm-project?rev=176766&view=rev
>>> Log:
>>> TLI: Microoptimize calls to strlen+memcmp to strncmp.
>>>
>>> The strlen+memcmp was hidden in a call to StringRef::operator==. We check if
>>> there are any null bytes in the string upfront so we can simplify the comparison
>>> Small speedup when compiling code with many function calls.
>>>
>>> Modified:
>>> llvm/trunk/lib/Target/TargetLibraryInfo.cpp
>>>
>>> Modified: llvm/trunk/lib/Target/TargetLibraryInfo.cpp
>>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/TargetLibraryInfo.cpp?rev=176766&r1=176765&r2=176766&view=diff
>>> ==============================================================================
>>> --- llvm/trunk/lib/Target/TargetLibraryInfo.cpp (original)
>>> +++ llvm/trunk/lib/Target/TargetLibraryInfo.cpp Sat Mar 9 07:48:23 2013
>>> @@ -597,15 +597,37 @@ TargetLibraryInfo::TargetLibraryInfo(con
>>> CustomNames = TLI.CustomNames;
>>> }
>>> +namespace {
>>> +struct StringComparator {
>>> + /// Compare two strings and return true if LHS is lexicographically less than
>>> + /// RHS. Requires that RHS doesn't contain any zero bytes.
>>> + bool operator()(const char *LHS, StringRef RHS) const {
>>> + // Compare prefixes with strncmp. If prefixes match we know that LHS is
>>> + // greater or equal to RHS as RHS can't contain any '\0'.
>>> + return std::strncmp(LHS, RHS.data(), RHS.size()) < 0;
>>> + }
>>> +
>>> + // Provided for compatibility with MSVC's debug mode.
>>> + bool operator()(StringRef LHS, const char *RHS) const { return LHS < RHS; }
>>> + bool operator()(StringRef LHS, StringRef RHS) const { return LHS < RHS; }
>>> +};
>>> +}
>>> +
>>> bool TargetLibraryInfo::getLibFunc(StringRef funcName,
>>> LibFunc::Func &F) const {
>>> const char **Start = &StandardNames[0];
>>> const char **End = &StandardNames[LibFunc::NumLibFuncs];
>>> +
>>> + // Filter out empty names and names containing null bytes, those can't be in
>>> + // our table.
>>> + if (funcName.empty() || funcName.find('\0') != StringRef::npos)
>>> + return false;
>>> +
>>> // Check for \01 prefix that is used to mangle __asm declarations and
>>> // strip it if present.
>>> - if (!funcName.empty() && funcName.front() == '\01')
>>> + if (funcName.front() == '\01')
>>> funcName = funcName.substr(1);
>>> - const char **I = std::lower_bound(Start, End, funcName);
>>> + const char **I = std::lower_bound(Start, End, funcName, StringComparator());
>>> if (I != End && *I == funcName) {
>>> F = (LibFunc::Func)(I - Start);
>>> return true;
>>>
>>>
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>>
>> --
>> Anton
>>
--
Anton
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