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Re: -O* Gives Different Results than Individual Optimizations?
> There was another interesting question in that mail: is "-O1" flag
> something different from just combination of "-fsomething" flags?
This really is the question I'm interested in. The problem itself was
fixed, I just don't understand why applying the same optimizations
(and more) which make up -O1 don't elicit the same behavior.
Mike
On Mon, Oct 12, 2009 at 3:43 AM, Alexey Salmin <alexey.salmin@gmail.com> wrote:
>
> On Mon, Oct 12, 2009 at 2:20 PM, Ian Lance Taylor <iant@google.com> wrote:
> > Mike Sullivan <mbsullivan@gmail.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
> > -mfpmath=sse.
> >
> > Ian
> >
>
> There was another interesting question in that mail: is "-O1" flag
> something different from just combination of "-fsomething" flags?
>
> Alexey