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Re: Start implementing -frounding-math
- From: Joseph Myers <joseph at codesourcery dot com>
- To: Richard Biener <richard dot guenther at gmail dot com>
- Cc: Marc Glisse <marc dot glisse at inria dot fr>, GCC Patches <gcc-patches at gcc dot gnu dot org>
- Date: Thu, 8 Aug 2019 00:04:59 +0000
- Subject: Re: Start implementing -frounding-math
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- References: <alpine.DEB.2.02.1906221743430.16432@grove.saclay.inria.fr> <ADA10368-A011-4D72-BCD0-BA2E38B07EA3@gmail.com> <alpine.DEB.2.21.1906222238240.24626@stedding.saclay.inria.fr> <CAFiYyc3nmHxFb9W2M37FhMwhhuFQ=mqX66D8jtzVw9=+n+G4FA@mail.gmail.com>
On Mon, 24 Jun 2019, Richard Biener wrote:
> On the patch I'd name _DIV _RDIV (to match the tree code we are dealing
> with). You miss _NEGATE and also the _FIX_TRUNC and _FLOAT in
> case those might trap with -ftrapping-math. There are also internal
Negation (and abs and copysign) can never raise any exceptions even with
signaling NaN arguments.
Conversion between integers and floating-point *can* raise exceptions
(depending on the types involved, e.g. conversions from int to IEEE double
are always exact with no exceptions raised). And conversions from integer
to floating-point, when the types mean they aren't necessarily exact,
depend on the rounding mode (whereas conversions from floating-point to
integer types always truncate towards 0).
--
Joseph S. Myers
joseph@codesourcery.com