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From: Szabolcs Nagy <nsz@sourceware.org> To: glibc-cvs@sourceware.org Subject: [glibc/arm/morello/main] math: Fix asin and acos invalid exception with old gcc Date: Wed, 26 Oct 2022 15:09:57 +0000 (GMT) [thread overview] Message-ID: <20221026150957.2635D385114A@sourceware.org> (raw) https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=86cb990eeb22d64be6ab4c7ac3c70b507734dfd7 commit 86cb990eeb22d64be6ab4c7ac3c70b507734dfd7 Author: Szabolcs Nagy <szabolcs.nagy@arm.com> Date: Thu Oct 13 11:10:10 2022 +0100 math: Fix asin and acos invalid exception with old gcc This works around a gcc issue where it const folded inf/inf into nan, preventing the invalid exception to be signalled. (x-x)/(x-x) is more robust against optimizations and works for all out of bounds values including x==nan. The gcc issue https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95115 should be fixed on release branches starting from gcc-10, but it is better to change the code in case glibc is built with older gcc. Diff: --- sysdeps/ieee754/dbl-64/e_asin.c | 18 ++---------------- 1 file changed, 2 insertions(+), 16 deletions(-) diff --git a/sysdeps/ieee754/dbl-64/e_asin.c b/sysdeps/ieee754/dbl-64/e_asin.c index e7ea0cbe8f..6b7c971e76 100644 --- a/sysdeps/ieee754/dbl-64/e_asin.c +++ b/sysdeps/ieee754/dbl-64/e_asin.c @@ -165,14 +165,7 @@ __ieee754_asin(double x){ /*---------------------------- |x|>=1 -------------------------------*/ else if (k==0x3ff00000 && u.i[LOW_HALF]==0) return (m>0)?hp0.x:-hp0.x; else - if (k>0x7ff00000 || (k == 0x7ff00000 && u.i[LOW_HALF] != 0)) return x + x; - else { - u.i[HIGH_HALF]=0x7ff00000; - v.i[HIGH_HALF]=0x7ff00000; - u.i[LOW_HALF]=0; - v.i[LOW_HALF]=0; - return u.x/v.x; /* NaN */ - } + return (x - x) / (x - x); } #ifndef __ieee754_asin libm_alias_finite (__ieee754_asin, __asin) @@ -334,14 +327,7 @@ __ieee754_acos(double x) else if (k==0x3ff00000 && u.i[LOW_HALF]==0) return (m>0)?0:2.0*hp0.x; else - if (k>0x7ff00000 || (k == 0x7ff00000 && u.i[LOW_HALF] != 0)) return x + x; - else { - u.i[HIGH_HALF]=0x7ff00000; - v.i[HIGH_HALF]=0x7ff00000; - u.i[LOW_HALF]=0; - v.i[LOW_HALF]=0; - return u.x/v.x; - } + return (x - x) / (x - x); } #ifndef __ieee754_acos libm_alias_finite (__ieee754_acos, __acos)
next reply other threads:[~2022-10-26 15:09 UTC|newest] Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top 2022-10-26 15:09 Szabolcs Nagy [this message] 2022-11-23 14:38 Szabolcs Nagy
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