[cfe-dev] Clang versus GCC speed

[Douglas Gregor]

On Nov 20, 2009, at 11:07 AM, Jean-Daniel Dupas wrote:

>
> Le 20 nov. 2009 à 19:36, David Chisnall a écrit :
>
>> Hi,
>>
>> Has anyone done any tests comparing gcc compilation speed to clang
>> recently?  I just did some tests with Objective-C programs and found
>> clang much slower than GCC 4.2, with an optimized build of LLVM and
>> Clang and a stock build of GCC.
>>
>> David
>>
>
>
> Just a quick test gave me this on an Objective-C project:
>
> Clang (r89342) (Note that I replaced Xcode's clang binaries by a svn  
> version so it uses it when I pass com.apple.compilers.llvm.clang.1_0)
> time xcodebuild -configuration Release  
> GCC_VERSION=com.apple.compilers.llvm.clang.1_0 ARCHS=i386
> 	68.314u 16.219s 1:07.79 124.6%	0+0k 17+476io 0pf+0w
>
> GCC-4.2:
> time xcodebuild -configuration Release ARCHS=i386
> 	127.909u 45.820s 2:02.94 141.3%	0+0k 0+639io 0pf+0w

I'm guessing that you're using precompiled headers. Clang usually tops  
out at about 30% faster than GCC without precompiled headers, with  
much better performance when we're using precompiled headers.

	- Doug