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Re: Update x86 ulps for GCC 7 [committed]
- From: Joseph Myers <joseph at codesourcery dot com>
- To: Markus Trippelsdorf <markus at trippelsdorf dot de>
- Cc: <libc-alpha at sourceware dot org>
- Date: Mon, 26 Jun 2017 10:43:57 +0000
- Subject: Re: Update x86 ulps for GCC 7 [committed]
- Authentication-results: sourceware.org; auth=none
- References: <alpine.DEB.firstname.lastname@example.org> <20170624111003.GA284@x4>
On Sat, 24 Jun 2017, Markus Trippelsdorf wrote:
> On 2017.06.23 at 20:23 +0000, Joseph Myers wrote:
> > Testing with GCC 7 for 32-bit x86 showed some ulps differences,
> > presumably from variation in when values with excess precision get
> > spilled to the stack and so lose that precision. This patch updates
> > the libm-test-ulps files accordingly.
> For AMD Ryzen x86_64 I need an additional update:
Such updates should generally just be committed. In this case (x86_64,
not long double) I'm not clear why you'd have ulps variation between
processors, since excess precision is irrelevant on x86_64 and the x87
transcendental instructions would only be used for long double. But it
could be an fma issue, if $CC $CFLAGS defaults to generating fma
instructions, as that can cause ulps variation across architectures.
Joseph S. Myers