glibc/sysdeps/powerpc/fpu/w_sqrt.c
Ulrich Drepper d347a4ab1d Update.
2003-07-31  Jakub Jelinek  <jakub@redhat.com>

	* dlfcn/dlerror.c (once): New.
	(dlerror): Call __libc_once.
	(_dlerror_run): Remove once.

2003-07-31  Jakub Jelinek  <jakub@redhat.com>

	* sysdeps/unix/sysv/linux/ia64/bits/sigcontext.h (struct sigcontext):
	Sync with 2.5.7 and 2.5.73 kernel changes.

2003-07-31  Jakub Jelinek  <jakub@redhat.com>

	* dlfcn/eval.c (funcall): Add noinline attribute to shut up warnings.
	* elf/rtld.c (dl_main): Cast ElfW(Addr) arguments with %Zx/%Zd
	formats to size_t.
	* elf/dl-lookup.c (_dl_debug_bindings): Likewise.
	* elf/tst-tls6.c (do_test): Use %zd format for l_tls_modid.
	* elf/tst-tls8.c (do_test): Use %zd format for modid1 and modid2.
	* gmon/tst-sprofil.c (main): Add parens to shut up warning.
	* iconv/tst-iconv3.c (main): Use %td instead of %zd for pointer
	difference argument.
	* stdio-common/tst-wc-printf.c (main): Cast arguments with %C
	format to wint_t.
	* stdlib/tst-limits.c (main): For WORD_BIT and LONG_BIT, use
	%d format and cast expected value to int.
	* sysdeps/generic/libc-start.c (STATIC): Add
	__attribute__((always_inline) if LIBC_START_MAIN is already defined.
	* sysdeps/powerpc/fpu/w_sqrt.c (a_nan, a_inf): Change from uint32_t
	to ieee_float_shape_type.
	(__sqrt): Avoid type punning.
	* sysdeps/powerpc/fpu/w_sqrtf.c (a_nan, a_inf): Change from uint32_t
	to ieee_float_shape_type.
	(__sqrtf): Avoid type punning.
	* sysdeps/s390/s390-32/dl-machine.h (elf_machine_rela): Don't define
	refsym if in dl-conflict.c.
	* sysdeps/s390/s390-64/dl-machine.h (elf_machine_rela): Likewise.
	* sysdeps/unix/sysv/linux/i386/semctl.c (union semun): Add __old_buf.
	(__new_semctl): Shut up warning.
	* sysdeps/unix/sysv/linux/semctl.c (union semun): Add __old_buf.
	(__new_semctl): Shut up warning.
	* sysdeps/unix/sysv/linux/shmctl.c (__new_shmctl): Wrap long lines.
	Change old into union of __old_shmid_ds and __old_shminfo structs.
	Adjust all users.
	* wcsmbs/wcsmbs-tst1.c (main): Cast arguments with %C format to wint_t.

2003-07-31  Jakub Jelinek  <jakub@redhat.com>

	* sysdeps/unix/sysv/linux/utimes.c (__utimes): Fix actime and
	modtime computation.
	* sysdeps/unix/sysv/linux/futimes.c (__futimes): Likewise.
	* sysdeps/posix/utimes.c (__utimes): Likewise.
2003-07-31 19:26:38 +00:00

147 lines
5.1 KiB
C

/* Double-precision floating point square root.
Copyright (C) 1997, 2002, 2003 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, write to the Free
Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
02111-1307 USA. */
#include <math.h>
#include <math_private.h>
#include <fenv_libc.h>
#include <inttypes.h>
static const double almost_half = 0.5000000000000001; /* 0.5 + 2^-53 */
static const ieee_float_shape_type a_nan = { .word = 0x7fc00000 };
static const ieee_float_shape_type a_inf = { .word = 0x7f800000 };
static const float two108 = 3.245185536584267269e+32;
static const float twom54 = 5.551115123125782702e-17;
extern const float __t_sqrt[1024];
/* The method is based on a description in
Computation of elementary functions on the IBM RISC System/6000 processor,
P. W. Markstein, IBM J. Res. Develop, 34(1) 1990.
Basically, it consists of two interleaved Newton-Rhapson approximations,
one to find the actual square root, and one to find its reciprocal
without the expense of a division operation. The tricky bit here
is the use of the POWER/PowerPC multiply-add operation to get the
required accuracy with high speed.
The argument reduction works by a combination of table lookup to
obtain the initial guesses, and some careful modification of the
generated guesses (which mostly runs on the integer unit, while the
Newton-Rhapson is running on the FPU). */
double
__sqrt(double x)
{
const float inf = a_inf.value;
/* x = f_wash(x); *//* This ensures only one exception for SNaN. */
if (x > 0)
{
if (x != inf)
{
/* Variables named starting with 's' exist in the
argument-reduced space, so that 2 > sx >= 0.5,
1.41... > sg >= 0.70.., 0.70.. >= sy > 0.35... .
Variables named ending with 'i' are integer versions of
floating-point values. */
double sx; /* The value of which we're trying to find the
square root. */
double sg,g; /* Guess of the square root of x. */
double sd,d; /* Difference between the square of the guess and x. */
double sy; /* Estimate of 1/2g (overestimated by 1ulp). */
double sy2; /* 2*sy */
double e; /* Difference between y*g and 1/2 (se = e * fsy). */
double shx; /* == sx * fsg */
double fsg; /* sg*fsg == g. */
fenv_t fe; /* Saved floating-point environment (stores rounding
mode and whether the inexact exception is
enabled). */
uint32_t xi0, xi1, sxi, fsgi;
const float *t_sqrt;
fe = fegetenv_register();
EXTRACT_WORDS (xi0,xi1,x);
relax_fenv_state();
sxi = (xi0 & 0x3fffffff) | 0x3fe00000;
INSERT_WORDS (sx, sxi, xi1);
t_sqrt = __t_sqrt + (xi0 >> (52-32-8-1) & 0x3fe);
sg = t_sqrt[0];
sy = t_sqrt[1];
/* Here we have three Newton-Rhapson iterations each of a
division and a square root and the remainder of the
argument reduction, all interleaved. */
sd = -(sg*sg - sx);
fsgi = (xi0 + 0x40000000) >> 1 & 0x7ff00000;
sy2 = sy + sy;
sg = sy*sd + sg; /* 16-bit approximation to sqrt(sx). */
INSERT_WORDS (fsg, fsgi, 0);
e = -(sy*sg - almost_half);
sd = -(sg*sg - sx);
if ((xi0 & 0x7ff00000) == 0)
goto denorm;
sy = sy + e*sy2;
sg = sg + sy*sd; /* 32-bit approximation to sqrt(sx). */
sy2 = sy + sy;
e = -(sy*sg - almost_half);
sd = -(sg*sg - sx);
sy = sy + e*sy2;
shx = sx * fsg;
sg = sg + sy*sd; /* 64-bit approximation to sqrt(sx),
but perhaps rounded incorrectly. */
sy2 = sy + sy;
g = sg * fsg;
e = -(sy*sg - almost_half);
d = -(g*sg - shx);
sy = sy + e*sy2;
fesetenv_register (fe);
return g + sy*d;
denorm:
/* For denormalised numbers, we normalise, calculate the
square root, and return an adjusted result. */
fesetenv_register (fe);
return __sqrt(x * two108) * twom54;
}
}
else if (x < 0)
{
#ifdef FE_INVALID_SQRT
feraiseexcept (FE_INVALID_SQRT);
/* For some reason, some PowerPC processors don't implement
FE_INVALID_SQRT. I guess no-one ever thought they'd be
used for square roots... :-) */
if (!fetestexcept (FE_INVALID))
#endif
feraiseexcept (FE_INVALID);
#ifndef _IEEE_LIBM
if (_LIB_VERSION != _IEEE_)
x = __kernel_standard(x,x,26);
else
#endif
x = a_nan.value;
}
return f_wash(x);
}
weak_alias (__sqrt, sqrt)
/* Strictly, this is wrong, but the only places where _ieee754_sqrt is
used will not pass in a negative result. */
strong_alias(__sqrt,__ieee754_sqrt)
#ifdef NO_LONG_DOUBLE
weak_alias (__sqrt, __sqrtl)
weak_alias (__sqrt, sqrtl)
#endif