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Re: optimization/10189: pentium4 breaks suns libm code for __ieee754_pow(double x, double y)
- From: "David O'Brien" <obrien at freebsd dot org>
- To: ljrittle at gcc dot gnu dot org, freebsd-current at freebsd dot org, gcc-bugs at gcc dot gnu dot org, gcc-prs at gcc dot gnu dot org, nobody at gcc dot gnu dot org, till at f111 dot hadiko dot de, gcc-gnats at gcc dot gnu dot org
- Date: Wed, 26 Mar 2003 09:45:35 -0800
- Subject: Re: optimization/10189: pentium4 breaks suns libm code for __ieee754_pow(double x, double y)
- Organization: The NUXI BSD Group
- References: <20030326130118.8374.qmail@sources.redhat.com>
- Reply-to: obrien at freebsd dot org
On Wed, Mar 26, 2003 at 01:01:18PM -0000, ljrittle at gcc dot gnu dot org wrote:
> Synopsis: pentium4 breaks suns libm code for __ieee754_pow(double x, double y)
Beautiful email!!
> Special secret #2: Although the FSF-side does want to improve all
> code generation (and I think proper PRs RE CPU switches will be
> looked at by someone given enough time) be aware that -O2 without
> special arch flags is probably the most stable for any given CPU
> for any given gcc release. Do you really want to trust a kernel
> built with optimization flags and arch flags that near zero or zero
> people have fully tested? Doubtful. However, inline with secret
> #1 and by virtual of being digital, if even one person tests it
> (i.e. yourself) and it appears OK, then it is probably safe to at
> least attempt to build a kernel and run it.
FreeBSD has for years recommended -O[1] vs. -O2. Do you think there is
value in having the GCC test suite runs you do at FreeBSD.org do runs
with both settings? To also do runs with the newer CPU types?