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/* nearbyint long double.
IBM extended format long double version.
Copyright (C) 2004, 2006 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 <sysdep.h>
#include <math_ldbl_opt.h>
.section ".toc","aw"
.LC0: /* 2**52 */
.tc FD_43300000_0[TC],0x4330000000000000
.section ".text"
/* long double [fp1,fp2] nearbyintl (long double x [fp1,fp2])
IEEE 1003.1 nearbyintl function. nearbyintl is simular to the rintl
but does raise the "inexact" exception. This implementation is
based on rintl but explicitly maskes the inexact exception on entry
and clears any pending inexact before restoring the exception mask
on exit.
PowerPC64 long double uses the IBM extended format which is
represented two 64-floating point double values. The values are
non-overlapping giving an effective precision of 106 bits. The first
double contains the high order bits of mantisa and is always rounded
to represent a normal rounding of long double to double. Since the
long double value is sum of the high and low values, the low double
normally has the opposite sign to compensate for the this rounding.
For long double there are two cases:
1) |x| < 2**52, all the integer bits are in the high double.
floor the high double and set the low double to -0.0.
2) |x| >= 2**52, Rounding involves both doubles.
See the comment before lable .L2 for details.
*/
ENTRY (__nearbyintl)
mffs fp11 /* Save current FPSCR. */
lfd fp13,.LC0@toc(2)
fabs fp0,fp1
mtfsb0 28 /* Disable "inexact" exceptions. */
fsub fp12,fp13,fp13 /* generate 0.0 */
fabs fp9,fp2
fcmpu cr7,fp0,fp13 /* if (fabs(x) > TWO52) */
fcmpu cr6,fp1,fp12 /* if (x > 0.0) */
bnl- cr7,.L2
fmr fp2,fp12
bng- cr6,.L4
fadd fp1,fp1,fp13 /* x+= TWO52; */
fsub fp1,fp1,fp13 /* x-= TWO52; */
b .L9
.L4:
bnl- cr6,.L9 /* if (x < 0.0) */
fsub fp1,fp13,fp1 /* x = TWO52 - x; */
fsub fp0,fp1,fp13 /* x = - (x - TWO52); */
fneg fp1,fp0
.L9:
mtfsb0 6 /* Clear any pending "inexact" exceptions. */
mtfsf 0x01,fp11 /* restore exception mask. */
blr
/* The high double is > TWO52 so we need to round the low double and
perhaps the high double. This gets a bit tricky so we use the
following algorithm:
tau = floor(x_high/TWO52);
x0 = x_high - tau;
x1 = x_low + tau;
r1 = nearbyint(x1);
y_high = x0 + r1;
y_low = r1 - tau;
return y; */
.L2:
fcmpu cr7,fp9,fp13 /* if (|x_low| > TWO52) */
fcmpu cr0,fp9,fp12 /* || (|x_low| == 0.0) */
bge- cr7,.L9 /* return x; */
beq- cr0,.L9
fdiv fp8,fp1,fp13 /* x_high/TWO52 */
fctidz fp0,fp8
fcfid fp8,fp0 /* tau = floor(x_high/TWO52); */
fsub fp3,fp1,fp8 /* x0 = x_high - tau; */
fadd fp4,fp2,fp8 /* x1 = x_low + tau; */
fcmpu cr6,fp4,fp12 /* if (x1 > 0.0) */
bng- cr6,.L8
fadd fp5,fp4,fp13 /* r1 = x1 + TWO52; */
fsub fp5,fp5,fp13 /* r1 = r1 - TWO52; */
b .L6
.L8:
fmr fp5,fp4
bge- cr6,.L6 /* if (x1 < 0.0) */
fsub fp5,fp13,fp4 /* r1 = TWO52 - x1; */
fsub fp0,fp5,fp13 /* r1 = - (r1 - TWO52); */
fneg fp5,fp0
.L6:
fadd fp1,fp3,fp5 /* y_high = x0 + r1; */
fsub fp2,fp5,fp8 /* y_low = r1 - tau; */
b .L9
END (__nearbyintl)
long_double_symbol (libm, __nearbyintl, nearbyintl)
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