Date: Sat, 10 Apr 2021 12:02:17 GMT From: Dimitry Andric <dim@FreeBSD.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-main@FreeBSD.org Subject: git: 3b00222f156d - main - Avoid raising unexpected floating point exceptions in libm Message-ID: <202104101202.13AC2Hgh092268@gitrepo.freebsd.org>
next in thread | raw e-mail | index | archive | help
The branch main has been updated by dim: URL: https://cgit.FreeBSD.org/src/commit/?id=3b00222f156dca5700c839d73e36daf479fa640c commit 3b00222f156dca5700c839d73e36daf479fa640c Author: Dimitry Andric <dim@FreeBSD.org> AuthorDate: 2021-04-09 23:07:54 +0000 Commit: Dimitry Andric <dim@FreeBSD.org> CommitDate: 2021-04-10 11:59:57 +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 MFC after: 1 week Differential Revision: https://reviews.freebsd.org/D29686 --- lib/msun/Makefile | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff --git a/lib/msun/Makefile b/lib/msun/Makefile index 4491bc216a4c..959dbd113ec1 100644 --- a/lib/msun/Makefile +++ b/lib/msun/Makefile @@ -34,6 +34,16 @@ CFLAGS+= -I${.CURDIR}/ld128 CFLAGS+= -I${.CURDIR}/${ARCH_SUBDIR} +.include <bsd.compiler.mk> +.if ${COMPILER_TYPE} == "clang" && ${COMPILER_VERSION} >= 100000 +# 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 +123,6 @@ 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 <bsd.compiler.mk> .if ${COMPILER_TYPE} == "gcc" CFLAGS.e_powl.c+= -Wno-error=overflow .endif
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?202104101202.13AC2Hgh092268>