Message ID | 20170624111003.GA284@x4 |
---|---|
State | Committed |
Headers |
Received: (qmail 127338 invoked by alias); 24 Jun 2017 11:10:10 -0000 Mailing-List: contact libc-alpha-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: <libc-alpha.sourceware.org> List-Unsubscribe: <mailto:libc-alpha-unsubscribe-##L=##H@sourceware.org> List-Subscribe: <mailto:libc-alpha-subscribe@sourceware.org> List-Archive: <http://sourceware.org/ml/libc-alpha/> List-Post: <mailto:libc-alpha@sourceware.org> List-Help: <mailto:libc-alpha-help@sourceware.org>, <http://sourceware.org/ml/#faqs> Sender: libc-alpha-owner@sourceware.org Delivered-To: mailing list libc-alpha@sourceware.org Received: (qmail 126824 invoked by uid 89); 24 Jun 2017 11:10:09 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-25.8 required=5.0 tests=AWL, BAYES_00, GIT_PATCH_0, GIT_PATCH_1, GIT_PATCH_2, GIT_PATCH_3, RCVD_IN_DNSWL_LOW, SPF_HELO_PASS autolearn=ham version=3.3.2 spammy= X-HELO: mail.ud10.udmedia.de Date: Sat, 24 Jun 2017 13:10:03 +0200 From: Markus Trippelsdorf <markus@trippelsdorf.de> To: Joseph Myers <joseph@codesourcery.com> Cc: libc-alpha@sourceware.org Subject: Re: Update x86 ulps for GCC 7 [committed] Message-ID: <20170624111003.GA284@x4> References: <alpine.DEB.2.20.1706232023420.16335@digraph.polyomino.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <alpine.DEB.2.20.1706232023420.16335@digraph.polyomino.org.uk> |
Commit Message
Markus Trippelsdorf
June 24, 2017, 11:10 a.m. UTC
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:
Comments
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.
On 2017.06.26 at 10:43 +0000, Joseph Myers wrote: > 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. Yes, it should be an fma issue because I used "march=native" (which turns on -mfma). I don't have write access, so it would be nice if somebody could commit the patch for me. Thanks.
On Mon, 26 Jun 2017, Markus Trippelsdorf wrote: > On 2017.06.26 at 10:43 +0000, Joseph Myers wrote: > > 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. > > Yes, it should be an fma issue because I used "march=native" (which > turns on -mfma). > I don't have write access, so it would be nice if somebody could commit > the patch for me. Now committed.
diff --git a/sysdeps/x86_64/fpu/libm-test-ulps b/sysdeps/x86_64/fpu/libm-test-ulps index 61da961a57..2f74643d34 100644 --- a/sysdeps/x86_64/fpu/libm-test-ulps +++ b/sysdeps/x86_64/fpu/libm-test-ulps @@ -1381,9 +1381,9 @@ ldouble: 3 Function: Imaginary part of "ctan_upward": double: 2 -float: 1 +float: 2 idouble: 2 -ifloat: 1 +ifloat: 2 ildouble: 3 ldouble: 3