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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 Date: Thu, 20 Oct 2022 17:21:13 +0000 (GMT) [thread overview] Message-ID: <20221020172113.2DB75384D1BF@sourceware.org> (raw) https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=4ad4ea848b335d803bcf4754a1cea78f697eaec5 commit 4ad4ea848b335d803bcf4754a1cea78f697eaec5 Author: Szabolcs Nagy <szabolcs.nagy@arm.com> Date: Thu Oct 13 11:10:10 2022 +0100 math: Fix asin and acos invalid exception This works around a gcc issue where it const folds inf/inf into nan, preventing the invalid exception signal to be raised. (x-x)/(x-x) is more robust against optimizations and works for x==nan too. The issue should be fixed in gcc-11.3.0 and gcc-12, but glibc supports older compilers. 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)
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