[Patch, fortran] [00/66] PR fortran/43829 Inline sum and product (AKA scalarization of reductions)

[Mikael Morin]

On Friday 28 October 2011 15:56:36 Jack Howarth wrote:
> Mikael,
>     The complete patch bootstraps current FSF gcc trunk on
> x86_64-apple-darwin11 and the resulting gfortran compiler can compile the
> Polyhedron 2005 benchmarks using...
> 
> Compile Command : gfortran-fsf-4.7 -O3 -ffast-math -funroll-loops -flto
> -fwhole-program %n.f90 -o %n
> 
> without runtime regressions. However I don't seem to see any particular
> performance improvements with your patches applied. In fact, a few
> benchmarks including nf and test_fpu seem to show slower runtimes
> (~8-11%). Have you done any benchmarking with and without the proposed
> patches? Jack

Not myself, but the previous versions of the patch have been reported to give 
sensitive improvement on "tonto" here:
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43829#c26
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43829#c35

Since those versions, the array constructor handling has been improved, and a 
few mostly cosmetic changes have been applied, so I expect the posted patch to 
be on par with the previous ones, possibly slightly better.

Now regarding your regressions, it is quite a lot worse, and quite unexpected.
I have just looked at test_fpu.f90 and nf.f90 from a polyhedron source I have 
found at http://www.polyhedron.com/web_images/documents/pb05.zip. 
There is no call to product in them, and both use only single-argument sum 
calls, which are not (or shouldn't be) impacted by my patch (scalar cases). 
Indeed, if I compare the code produced using -fdump-tree-original, there is 
zero difference in nf.f90, and in test_fpu.f90 only slight variations which 
are very very unlikely to cause the regression you see (see attached diff).

Could you double check your figures, and/or that the regressions are really 
caused by my patch?

Mikael
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