Re: Comparing Linux C and C++ Compilers: Benchmarks and Analysis

[Devang Patel <dpatel@apple.com>]

On Sep 19, 2004, at 7:02 AM, Jeremy Sanders wrote:

> On Sat, 18 Sep 2004, Richard Guenther wrote:
>
>> You may want to check gcc 4.0s auto-vectorizing capabilities by using 
>> -ftree-vectorize.  I believe Intel compiler does this by default with 
>> your optimization settings, and also unrolls loops where profitable 
>> (-funroll-loops for all gcc versions).  While I personally do not 
>> have success with auto-vectorizing (neither with Intel nor with gcc), 
>> loop unrolling shows very positive effects on my numerical codes.
>
> I tried compiling scimark with gcc 4 with -ftree-vectorize -msse2 
> -fdump-tree-vect-stats and again with the lno branch. This was with a 
> P4 on Fedora Core 2. Looking at the generated .vect files, it looked 
> like gcc wasn't able to vectorize any of the loops in scimark, which 
> is a bit diappointing. It's possible I didn't use it correctly I 
> suppose.

Would it be possible to post what GCC emits in .vect file, using 
-fdump-tree-vect-details option, for loops that you expect to get 
vectorized (or loops that are vectorized by other compilers)?. If you 
can provide preprocessed source file, I can try it on powerpc-darwin.

Thanks,
-
Devang