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Re: where to discuss problems with IEEE 754 standard on x86 architecture?
- From: Brian Dessent <brian at dessent dot net>
- To: Petr Savicky <savicky at cs dot cas dot cz>
- Cc: Nick Maclaren <nmm1 at cus dot cam dot ac dot uk>, gcc-help at gcc dot gnu dot org
- Date: Wed, 23 May 2007 01:18:56 -0700
- Subject: Re: where to discuss problems with IEEE 754 standard on x86 architecture?
- References: <E1Hqav8-0002Ul-Uk@draco.cus.cam.ac.uk> <20070523070851.GA2951@cs.cas.cz>
- Reply-to: gcc-help at gcc dot gnu dot org
Petr Savicky wrote:
> With "gcc -mfpmath=sse -msse" I obtained no warning/error, but the program
> behaves in the old wrong way.
Try with -O2 and you'll see vastly different results. Without any -O
you're telling gcc not to do any optimization whatsoever, and many, many
passes are just never run in that case so lots of stuff won't work.
It's possible that none of -mfpmath or -ffast-math or -ffloat-store or
-mpc32/-mpc64/-mpc80 et al. don't work without optimization passes
enabled. But you'd have to look at the code and documentation to find
out for sure.
Brian