On 6/17/07, Uros Bizjak <[EMAIL PROTECTED]> wrote:
Hello!
> I was wondering if there are objects to automatically activating Uros'
> new -mrecip flag when -ffast-math is specified. It looks like a good
> match since -mrecip is exactly about fast non-precise mathematics.
There is a discussion in gcc-patches@ mailing list about this topic, in
"Re: [PATCH, middle-end, i386]: reciprocal rsqrt pass + full recip x86
backend support" thread [1]. The main problem is, that one of the
polyhedron tests segfaults with this patch (not the problem of the recip
patch, but usage of questionable FP equivalence tests and FP indexes in
the array).
Of course there are cases with every optimization enabled by -ffast-math that
can break existing programs. Just that we know of one case beforehand shouldn't
prevent us from enabling -mrecip at -ffast-math (provided -mno-recip
still works,
regardless if provided before or after -ffast-math). [We'll at least
get some more
testing coverage this way]
Richard.
