Re: optimization/10189: pentium4 breaks suns libm code for __ieee754_pow(double x, double y)

[Alexander Leidinger <Alexander@Leidinger.net>]

The following reply was made to PR optimization/10189; it has been noted by GNATS.

From: Alexander Leidinger <Alexander@Leidinger.net>
To: gcc-gnats@gcc.gnu.org
Cc: ljrittle@gcc.gnu.org, freebsd-current@freebsd.org, gcc-bugs@gcc.gnu.org,
   gcc-prs@gcc.gnu.org, nobody@gcc.gnu.org, till@f111.hadiko.de
Subject: Re: optimization/10189: pentium4 breaks suns libm code for
 __ieee754_pow(double x, double y)
Date: Wed, 26 Mar 2003 22:09:34 +0100

 On 26 Mar 2003 13:01:18 -0000
 ljrittle@gcc.gnu.org wrote:
 
 > Synopsis: pentium4 breaks suns libm code for __ieee754_pow(double x, double y)
 
 [...]
 
 >  FreeBSD src tree; and (c) that really cares about building FreeBSD
 >  src with special CPU settings (do you guys really see enough speedup
 >  to warrant this extra nightmare? ;-)
 
 Without knowing anything about the FreeBSD related PRs in the gcc PR
 database I just comment on the last part of the quoted sentence...
 
 The official "allowed" optimization is "-O". But it is as easy as
 setting 'CFLAGS=-my-special-optim' in /etc/make.conf and start "make
 buildworld" in /usr/src to rebuild the userland with new optimizations.
 And trust me, as long as gcc ships with a description of other
 optimizations beneath "-O" there will be (clueless or smart... does it
 really matter here?) people which will try those optimizations on
 everything (after I managed to convince the Linux version of icc to
 generate FreeBSD object files and committed a port into our ports
 collection one of the first questions was "Are we are able to build the
 userland/kernel with it?", and now after icc is also able to link files
 without the help of gcc they ask "How much does it gain us to build the
 userland/kernel with icc?", even if it isn't possible to use icc to
 build the entire (or even large parts of the) kernel/userland yet). So
 it isn't a matter of "does it improve things if I do it this way" or "is
 it possible to do it this way", it's a matter of "how many PRs does it
 generate when -march=pentium4 breaks something but other -march=pentiumX
 optimizations don't"...
 
 Thanks for your insightful mail,
 Alexander.
 
 -- 
             0 and 1. Now what could be so hard about that?
 
 http://www.Leidinger.net                       Alexander @ Leidinger.net
   GPG fingerprint = C518 BC70 E67F 143F BE91  3365 79E2 9C60 B006 3FE7