From owner-dev-commits-src-all@freebsd.org Thu Apr 15 18:44:53 2021 Return-Path: Delivered-To: dev-commits-src-all@mailman.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.nyi.freebsd.org (Postfix) with ESMTP id 82EDF5D2565; Thu, 15 Apr 2021 18:44:53 +0000 (UTC) (envelope-from git@FreeBSD.org) Received: from mxrelay.nyi.freebsd.org (mxrelay.nyi.freebsd.org [IPv6:2610:1c1:1:606c::19:3]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256 client-signature RSA-PSS (4096 bits) client-digest SHA256) (Client CN "mxrelay.nyi.freebsd.org", Issuer "R3" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 4FLpDP3HWTz4j1m; Thu, 15 Apr 2021 18:44:53 +0000 (UTC) (envelope-from git@FreeBSD.org) Received: from gitrepo.freebsd.org (gitrepo.freebsd.org [IPv6:2610:1c1:1:6068::e6a:5]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (Client did not present a certificate) by mxrelay.nyi.freebsd.org (Postfix) with ESMTPS id 63BE21689F; Thu, 15 Apr 2021 18:44:53 +0000 (UTC) (envelope-from git@FreeBSD.org) Received: from gitrepo.freebsd.org ([127.0.1.44]) by gitrepo.freebsd.org (8.16.1/8.16.1) with ESMTP id 13FIirNn090522; Thu, 15 Apr 2021 18:44:53 GMT (envelope-from git@gitrepo.freebsd.org) Received: (from git@localhost) by gitrepo.freebsd.org (8.16.1/8.16.1/Submit) id 13FIiruL090521; Thu, 15 Apr 2021 18:44:53 GMT (envelope-from git) Date: Thu, 15 Apr 2021 18:44:53 GMT Message-Id: <202104151844.13FIiruL090521@gitrepo.freebsd.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-branches@FreeBSD.org From: Dimitry Andric Subject: git: bda3bf09d82d - stable/13 - Avoid raising unexpected floating point exceptions in libm MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit X-Git-Committer: dim X-Git-Repository: src X-Git-Refname: refs/heads/stable/13 X-Git-Reftype: branch X-Git-Commit: bda3bf09d82daf4352691a7b3a5b0e1cff66a5fd Auto-Submitted: auto-generated X-BeenThere: dev-commits-src-all@freebsd.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: Commit messages for all branches of the src repository List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 15 Apr 2021 18:44:53 -0000 The branch stable/13 has been updated by dim: URL: https://cgit.FreeBSD.org/src/commit/?id=bda3bf09d82daf4352691a7b3a5b0e1cff66a5fd commit bda3bf09d82daf4352691a7b3a5b0e1cff66a5fd Author: Dimitry Andric AuthorDate: 2021-04-09 23:07:54 +0000 Commit: Dimitry Andric CommitDate: 2021-04-15 18:33:54 +0000 Avoid raising unexpected floating point exceptions in libm When using clang with x86_64 CPUs that support AVX, some floating point transformations may raise exceptions that would not have been raised by the original code. To avoid this, use the -fp-exception-behavior=maytrap flag, introduced in clang 10.0.0. In particular, this fixes a number of test failures with ctanhf(3) and ctanf(3), when libm is compiled with -mavx. An unexpected FE_INVALID exception is then raised, because clang emits vdivps instructions to perform certain divides. (The vdivps instruction operates on multiple single-precision float operands simultaneously, but the exceptions may be influenced by unused parts of the XMM registers. In this particular case, it was calculating 0 / 0, which results in FE_INVALID.) If -fp-exception-behavior=maytrap is specified however, clang uses vdivss instructions instead, which work on one operand, and should not raise unexpected exceptions. Reported by: olivier Reviewed by: arichardson PR: 254911 Differential Revision: https://reviews.freebsd.org/D29686 (cherry picked from commit 3b00222f156dca5700c839d73e36daf479fa640c) Only use -fp-exception-behavior=maytrap on x86, for now After 3b00222f156d, it turns out that clang only supports strict floating point semantics for SystemZ and x86 at the moment, while for other architectures it is still experimental. Therefore, only use -fp-exception-behavior=maytrap on x86 for now, otherwise this option results in "error: overriding currently unsupported use of floating point exceptions on this target [-Werror,-Wunsupported-floating-point-opt]" on other architectures. Fixes: 3b00222f156d PR: 254911 (cherry picked from commit bae9fd0b33462e9506c3ac3400089c6dbc4aee8f) --- lib/msun/Makefile | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) diff --git a/lib/msun/Makefile b/lib/msun/Makefile index 4491bc216a4c..0a486bb5a086 100644 --- a/lib/msun/Makefile +++ b/lib/msun/Makefile @@ -34,6 +34,17 @@ CFLAGS+= -I${.CURDIR}/ld128 CFLAGS+= -I${.CURDIR}/${ARCH_SUBDIR} +.include +.if ${COMPILER_TYPE} == "clang" && ${COMPILER_VERSION} >= 100000 && \ + (${MACHINE_CPUARCH} == "amd64" || ${MACHINE_CPUARCH} == "i386") +# When using clang with x86_64 CPUs that support AVX, some floating point +# transformations may raise exceptions that would not have been raised by the +# original code. To avoid this, use the -fp-exception-behavior=maytrap flag, +# introduced in clang 10.0.0. +# See also: https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=254911 +CFLAGS+= -ffp-exception-behavior=maytrap +.endif + .PATH: ${.CURDIR}/bsdsrc .PATH: ${.CURDIR}/src .PATH: ${.CURDIR}/man @@ -113,7 +124,6 @@ COMMON_SRCS+= catrigl.c \ # 'long double' [-Werror=overflow] # if( y >= LDBL_MAX ) # See also: https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=130067 -.include .if ${COMPILER_TYPE} == "gcc" CFLAGS.e_powl.c+= -Wno-error=overflow .endif