From 7363a9a9a097c455a7ddb9386b4c6f7bdf91065f Mon Sep 17 00:00:00 2001 From: Szabolcs Nagy Date: Thu, 13 Oct 2022 11:10:10 +0100 Subject: [PATCH] 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. Reviewed-by: Wilco Dijkstra --- 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) -- 2.43.5