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Re: [PATCH, testsuite]: PR 58757: Check for FP denormal values without triggering denormal exceptions
- From: "Joseph S. Myers" <joseph at codesourcery dot com>
- To: Uros Bizjak <ubizjak at gmail dot com>
- Cc: "gcc-patches at gcc dot gnu dot org" <gcc-patches at gcc dot gnu dot org>, Marc Glisse <marc dot glisse at inria dot fr>
- Date: Tue, 23 Sep 2014 18:20:10 +0000
- Subject: Re: [PATCH, testsuite]: PR 58757: Check for FP denormal values without triggering denormal exceptions
- Authentication-results: sourceware.org; auth=none
- References: <CAFULd4bDzGPgSoGh-20zL4AOfTfoVoY_H12DJxvjdy-KGLo_Xg at mail dot gmail dot com> <Pine dot LNX dot 4 dot 64 dot 1409231755090 dot 20232 at digraph dot polyomino dot org dot uk> <CAFULd4YgvB8UNZFywToAvK8PxXC+VizinykEOGM4mJaCBuMbvA at mail dot gmail dot com>
On Tue, 23 Sep 2014, Uros Bizjak wrote:
> On Tue, Sep 23, 2014 at 7:57 PM, Joseph S. Myers
> <joseph@codesourcery.com> wrote:
>
> >> Attached patch avoids triggering denormal exceptions when FP insns are
> >> used to check for non-zero denormal values.
> >
> > But I thought the point of the test was to verify that the compiler's
> > understanding of existence of subnormal values was consistent with the
> > processor. If the processor is in a mode supporting such values, the
> > exceptions should be masked. That is, the present test should pass
> > unconditionally, if it doesn't pass that indicates a bug (which might be
> > appropriate for XFAILing).
>
> Alpha needs special instruction mode to process denormals. Without
> this special mode the insn traps as soon as denormal value is
> processed.
Yes, but I thought the point of that PR was that unless -mieee was given
to support such values, *_TRUE_MIN should be the same as *_MIN, reflecting
that they aren't supported. And so the failure is showing that this bug
is present (and so XFAILing with a comment referring to the bug is
appropriate, rather than changing the test to pass).
--
Joseph S. Myers
joseph@codesourcery.com