[cfe-dev] clang and Crypto++

[Marshall Clow]

On Jan 5, 2011, at 10:06 AM, Chris Lattner wrote:

> 
> On Jan 5, 2011, at 9:45 AM, Marshall Clow wrote:
> 
>>> Naturally, we'd like to know where in clang this time is going. Is it the front end (-fsyntax-only)? The optimizer (> -O0), and if so, which one(s)?
>> 
>> Looks like the optimizer.
>> 
>> $ time clang++ -Wno-tautological-compare -DNDEBUG -g         -arch x86_64 -arch i386 -DCRYPTOPP_DISABLE_ASM -pipe -fsyntax-only sha.cpp 
>> real	6.234s
>> $ time clang++ -Wno-tautological-compare -DNDEBUG -g         -arch x86_64 -arch i386 -DCRYPTOPP_DISABLE_ASM -pipe -c sha.cpp 
>> real 7.863s
>> $ time clang++ -Wno-tautological-compare -DNDEBUG -g -O1 -arch x86_64 -arch i386 -DCRYPTOPP_DISABLE_ASM -pipe -c sha.cpp 
>> real 17.882s
>> $ time clang++ -Wno-tautological-compare -DNDEBUG -g -O2 -arch x86_64 -arch i386 -DCRYPTOPP_DISABLE_ASM -pipe -c sha.cpp 
>> .... long, long time; I killed it after 30 minutes.
>> 
>> How do I tell which one?
> 
> Try passing -ftime-report to clang.  Another silly question: did you build clang itself in debug mode?  The first few lines of:
> 
> $ clang -cc1 -version
> 
> Should show either:
> 
> Low Level Virtual Machine (http://llvm.org/):
>  llvm version 2.9svn
>  DEBUG build with assertions.
> 
> or:
> 
> Low Level Virtual Machine (http://llvm.org/):
>  llvm version 2.9svn
>  Optimized build.

D'oh! It's a debug build.
I will build a non-debug one and re-run the timings.

-- Marshall