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Re: [gfortran] Exponentiation by integral exponents
- From: Paul Brook <paul at codesourcery dot com>
- To: fortran at gcc dot gnu dot org
- Cc: Tobias Schlüter <tobias dot schlueter at physik dot uni-muenchen dot de>,Andrew Pinski <pinskia at physics dot uc dot edu>,"gcc at gcc dot gnu dot org list" <gcc at gcc dot gnu dot org>
- Date: Tue, 27 Apr 2004 23:15:48 +0100
- Subject: Re: [gfortran] Exponentiation by integral exponents
- Organization: CodeSourcery
- References: <408ECD52.2090709@physik.uni-muenchen.de> <23B628D8-9891-11D8-9EA6-000393A6D2F2@physics.uc.edu> <408ED9A7.5060603@physik.uni-muenchen.de>
On Tuesday 27 April 2004 23:07, Tobias Schlüter wrote:
> Andrew Pinski wrote:
> > On Apr 27, 2004, at 17:14, Tobias Schlüter wrote:
> >> FYI I have ported Andy's code for exponentiation by an integral
> >> exponent to our tree. This is an implementation of Knuth's algorithm
>
> ...
>
> > You should not need it if you use __builtin_pow and you turn on
> > flag_unsafe_math_optimizations on. Maybe the best way is to have
> > another flag
> > to say expand __builtin_pow always.
>
> Does the builtin recognize the case pow(x,(float)i), where i is an
> integer? Then this sounds like a very good idea.
Maybe the way to indicate we always want to expand __builtin_pow would be to
pass the second parameter with an integer type. It may be easier to add
__builtin_powi to avoid needing polymorphic builtins.
Paul