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math: Fix acosf when building with gcc <= 11

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GCC <= 11 wrongly assumes the rounding is to nearest and performs a
constant folding where it should evaluate since the result is not
exact [1].

[1] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=57245
This commit is contained in:
Adhemerval Zanella 2025-01-02 10:54:11 -03:00
parent e41aabcc93
commit 9cc9f8e11e
7 changed files with 7 additions and 15 deletions
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2
sysdeps/aarch64/libm-test-ulps
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@ -11,7 +11,6 @@ float: 1
Function: "acos_downward":
double: 1
float: 1
ldouble: 1
Function: "acos_sve":
@ -20,7 +19,6 @@ float: 1
Function: "acos_towardzero":
double: 1
float: 1
ldouble: 1
Function: "acos_upward":

2
sysdeps/i386/fpu/libm-test-ulps
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@ -7,12 +7,10 @@ float128: 1
ldouble: 2
Function: "acos_downward":
float: 1
float128: 1
ldouble: 2
Function: "acos_towardzero":
float: 1
float128: 1
ldouble: 2

2
sysdeps/i386/i686/fpu/multiarch/libm-test-ulps
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@ -7,12 +7,10 @@ float128: 1
ldouble: 2
Function: "acos_downward":
float: 1
float128: 1
ldouble: 2
Function: "acos_towardzero":
float: 1
float128: 1
ldouble: 2

10
sysdeps/ieee754/flt-32/e_acosf.c
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@ -3,7 +3,7 @@
Copyright (c) 2023-2024 Alexei Sibidanov.
The original version of this file was copied from the CORE-MATH
project (file src/binary32/acos/acosf.c, revision 61d7bef).
project (file src/binary32/acos/acosf.c, revision 56dd347).
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
@ -28,6 +28,7 @@ SOFTWARE.
#include <math.h>
#include <math_private.h>
#include <libm-alias-finite.h>
#include <math-barriers.h>
#include "math_config.h"
static __attribute__ ((noinline)) float
@ -66,7 +67,7 @@ poly12 (double z, const double *c)
float
__ieee754_acosf (float x)
{
const double pi2 = 0x1.921fb54442d18p+0;
double pi2 = 0x1.921fb54442d18p+0;
static const double o[] = { 0, 0x1.921fb54442d18p+1 };
double xs = x;
double r;
@ -87,7 +88,10 @@ __ieee754_acosf (float x)
};
/* Avoid spurious underflow exception. */
if (__glibc_unlikely (ax <= 0x40000000u)) /* |x| < 2^-63 */
return (float) pi2;
/* GCC <= 11 wrongly assumes the rounding is to nearest and
performs a constant folding here:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=57245 */
return math_opt_barrier (pi2);
double z = xs;
double z2 = z * z;
double z4 = z2 * z2;

2
sysdeps/powerpc/fpu/libm-test-ulps
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@ -8,13 +8,11 @@ ldouble: 1
Function: "acos_downward":
double: 1
float: 1
float128: 1
ldouble: 3
Function: "acos_towardzero":
double: 1
float: 1
float128: 1
ldouble: 3

2
sysdeps/s390/fpu/libm-test-ulps
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@ -7,12 +7,10 @@ ldouble: 1
Function: "acos_downward":
double: 1
float: 1
ldouble: 1
Function: "acos_towardzero":
double: 1
float: 1
ldouble: 1
Function: "acos_upward":

2
sysdeps/x86_64/fpu/libm-test-ulps
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@ -8,13 +8,11 @@ ldouble: 2
Function: "acos_downward":
double: 1
float: 1
float128: 1
ldouble: 2
Function: "acos_towardzero":
double: 1
float: 1
float128: 1
ldouble: 2