This is the mail archive of the
mailing list for the GCC project.
Re: -O* Gives Different Results than Individual Optimizations?
- From: Ian Lance Taylor <iant at google dot com>
- To: Mike Sullivan <mbsullivan at gmail dot com>
- Cc: gcc-help at gcc dot gnu dot org
- Date: Mon, 12 Oct 2009 00:20:07 -0700
- Subject: Re: -O* Gives Different Results than Individual Optimizations?
- References: <firstname.lastname@example.org>
Mike Sullivan <email@example.com> writes:
> A co-worker of mine is having some odd floating-point issues that are
> related to the compilation options passed to GCC v4.3.3.
There are many instability issues with gcc floating point when using
the 80387 FP stack on x86. This is the classic bug report
http://gcc.gnu.org/PR323 , which has finally been fixed for the
upcoming gcc 4.5 by adding a new option -fexcess-precision=standard.
If your processor is newer than a Pentium 3, then you can avoid the
problem by using option such as -march=pentium4 -mtune=generic