This is the mail archive of the mailing list for the GCC project.

Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]
Other format: [Raw text]

Re: [PATCH] RTL expansion of exponentiation by integer constant

On Mon, 23 Jun 2003, Toon Moene wrote:
> Roger Sayle wrote:
> > As always this expansion is guarded by flag_unsafe_math_optimizations
> > as on machines without additional bits there may be rounding issues.  On
> > x86, which has extended precision, a very similar algorithm is used in
> > the implementation of glibc's pow function.  Similarly, the fortran
> > front-end also has similar code to implement X**N.  Hopefully, g77
> > may be able to switch to this code eventually.
> Well, yes, but g77 does this *unconditionally* because it is allowed by
> the Standard.  I could still call your implementation iff -ffast-math,
> of course ...

By design, the tests for both flag_unsafe_math_optimizations and
flag_errno_math are made outside of expand_powi, so that the language
front-ends that allow/want this functionality can call it directly.

I'm also a big fan of g77's code to expand powi of a variable
integer exponent inline using a loop, which I may also homage
(plagiarize) for the rest of GCC at some point in the future :>


Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]