glibc/math/s_clog_template.c
Szabolcs Nagy 347a5b592c math: Fix float conversion regressions with gcc-12 [BZ #28713]
Converting double precision constants to float is now affected by the
runtime dynamic rounding mode instead of being evaluated at compile
time with default rounding mode (except static object initializers).

This can change the computed result and cause performance regression.
The known correctness issues (increased ulp errors) are already fixed,
this patch fixes remaining cases of unnecessary runtime conversions.

Add float M_* macros to math.h as new GNU extension API.  To avoid
conversions the new M_* macros are used and instead of casting double
literals to float, use float literals (only required if the conversion
is inexact).

The patch was tested on aarch64 where the following symbols had new
spurious conversion instructions that got fixed:

  __clog10f
  __gammaf_r_finite@GLIBC_2.17
  __j0f_finite@GLIBC_2.17
  __j1f_finite@GLIBC_2.17
  __jnf_finite@GLIBC_2.17
  __kernel_casinhf
  __lgamma_negf
  __log1pf
  __y0f_finite@GLIBC_2.17
  __y1f_finite@GLIBC_2.17
  cacosf
  cacoshf
  casinhf
  catanf
  catanhf
  clogf
  gammaf_positive

Fixes bug 28713.

Reviewed-by: Paul Zimmermann <Paul.Zimmermann@inria.fr>
2022-01-10 14:27:17 +00:00

116 lines
3.1 KiB
C

/* Compute complex natural logarithm.
Copyright (C) 1997-2022 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
#include <complex.h>
#include <math.h>
#include <math_private.h>
#include <math-underflow.h>
#include <float.h>
CFLOAT
M_DECL_FUNC (__clog) (CFLOAT x)
{
CFLOAT result;
int rcls = fpclassify (__real__ x);
int icls = fpclassify (__imag__ x);
if (__glibc_unlikely (rcls == FP_ZERO && icls == FP_ZERO))
{
/* Real and imaginary part are 0.0. */
__imag__ result = signbit (__real__ x) ? M_MLIT (M_PI) : 0;
__imag__ result = M_COPYSIGN (__imag__ result, __imag__ x);
/* Yes, the following line raises an exception. */
__real__ result = -1 / M_FABS (__real__ x);
}
else if (__glibc_likely (rcls != FP_NAN && icls != FP_NAN))
{
/* Neither real nor imaginary part is NaN. */
FLOAT absx = M_FABS (__real__ x), absy = M_FABS (__imag__ x);
int scale = 0;
if (absx < absy)
{
FLOAT t = absx;
absx = absy;
absy = t;
}
if (absx > M_MAX / 2)
{
scale = -1;
absx = M_SCALBN (absx, scale);
absy = (absy >= M_MIN * 2 ? M_SCALBN (absy, scale) : 0);
}
else if (absx < M_MIN && absy < M_MIN)
{
scale = M_MANT_DIG;
absx = M_SCALBN (absx, scale);
absy = M_SCALBN (absy, scale);
}
if (absx == 1 && scale == 0)
{
__real__ result = M_LOG1P (absy * absy) / 2;
math_check_force_underflow_nonneg (__real__ result);
}
else if (absx > 1 && absx < 2 && absy < 1 && scale == 0)
{
FLOAT d2m1 = (absx - 1) * (absx + 1);
if (absy >= M_EPSILON)
d2m1 += absy * absy;
__real__ result = M_LOG1P (d2m1) / 2;
}
else if (absx < 1
&& absx >= M_LIT (0.5)
&& absy < M_EPSILON / 2
&& scale == 0)
{
FLOAT d2m1 = (absx - 1) * (absx + 1);
__real__ result = M_LOG1P (d2m1) / 2;
}
else if (absx < 1
&& absx >= M_LIT (0.5)
&& scale == 0
&& absx * absx + absy * absy >= M_LIT (0.5))
{
FLOAT d2m1 = M_SUF (__x2y2m1) (absx, absy);
__real__ result = M_LOG1P (d2m1) / 2;
}
else
{
FLOAT d = M_HYPOT (absx, absy);
__real__ result = M_LOG (d) - scale * M_MLIT (M_LN2);
}
__imag__ result = M_ATAN2 (__imag__ x, __real__ x);
}
else
{
__imag__ result = M_NAN;
if (rcls == FP_INFINITE || icls == FP_INFINITE)
/* Real or imaginary part is infinite. */
__real__ result = M_HUGE_VAL;
else
__real__ result = M_NAN;
}
return result;
}
declare_mgen_alias (__clog, clog)