Re: [PATCH] implement log10 and log2 functions as x87 builtins

[Uros Bizjak <uros at kss-loka dot si>]

Roger Sayle wrote:

> The patch itself looks fine.  However to large accept contributions to
> GCC we need to have a FSF copyright assignment on file.  You'll need to
> send an e-mail to assignments@gnu.org requesting the relevant forms.
>  
Thanks for reviewing this patch! As this is mainly cut'n'paste work, I 
didn't
consider it a big contribution, but following your instructions,  I have 
sent a request for
copyright assignment.

> For this patch, its also a good idea to include a new testcase or two.
> All that's required is a simple check that "log2" and "log10" can be
> called (probably both with compile-time constants or with variables) in
> their float, double and long double forms with -ffast-math on x86.  You
> don't even need to check the return values.  This ensures that all of
> the new code added by your patch is executed atleast once in gcc's
> testsuite, and prevents someone from breaking it in the future.
>  
Thanks for instructions, I will make an appropriate testcase.

> Once the paperwork is sorted out, there should be no problem getting
> this patch approved and committed to mainline for gcc 3.5.
>  
 BTW: From existing code, builtins for exp10() and exp2() functions can 
be written the same way
as builtins for logN. With these functions, it is possible to provide 
following transformations
with -ffast-math:

pow(10.0, x) -> exp10(x)
pow(2.0,x) -> exp2(x)
pow(e,x) -> exp(x)   // this one is somehow funny...

   Uros.