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/* llround function. PowerPC64 version.
Copyright (C) 2004-2017 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
<http://www.gnu.org/licenses/>. */
#include <sysdep.h>
#include <math_ldbl_opt.h>
#include <libm-alias-double.h>
.section ".toc","aw"
.LC0: /* 2^52 */
.tc FD_43300000_0[TC],0x4330000000000000
.LC1: /* 0.5 */
.tc FD_3fe00000_0[TC],0x3fe0000000000000
.section ".text"
/* long long [r3] llround (double x [fp1])
IEEE 1003.1 llround function. IEEE specifies "round to the nearest
integer value, rounding halfway cases away from zero, regardless of
the current rounding mode." However PowerPC Architecture defines
"round to Nearest" as "Choose the best approximation. In case of a
tie, choose the one that is even (least significant bit o).".
So we can't use the PowerPC "round to Nearest" mode. Instead we set
"round toward Zero" mode and round by adding +-0.5 before rounding
to the integer value.
It is necessary to detect when x is (+-)0x1.fffffffffffffp-2
because adding +-0.5 in this case will cause an erroneous shift,
carry and round. We simply return 0 if 0.5 > x > -0.5. Likewise
if x is and odd number between +-(2^52 and 2^53-1) a shift and
carry will erroneously round if biased with +-0.5. Therefore if x
is greater/less than +-2^52 we don't need to bias the number with
+-0.5. */
ENTRY (__llround)
CALL_MCOUNT 0
lfd fp9,.LC0@toc(2) /* Load 2^52 into fpr9. */
lfd fp10,.LC1@toc(2)/* Load 0.5 into fpr10. */
fabs fp2,fp1 /* Get the absolute value of x. */
fsub fp12,fp10,fp10 /* Compute 0.0 into fp12. */
fcmpu cr6,fp2,fp10 /* if |x| < 0.5 */
fcmpu cr7,fp2,fp9 /* if |x| >= 2^52 */
fcmpu cr1,fp1,fp12 /* x is negative? x < 0.0 */
blt- cr6,.Lretzero /* 0.5 > x < -0.5 so just return 0. */
bge- cr7,.Lnobias /* 2^52 > x < -2^52 just convert with no bias. */
/* Test whether an integer to avoid spurious "inexact". */
fadd fp3,fp2,fp9
fsub fp3,fp3,fp9
fcmpu cr5,fp2,fp3
beq cr5,.Lnobias
fadd fp3,fp2,fp10 /* |x|+=0.5 bias to prepare to round. */
bge cr1,.Lconvert /* x is positive so don't negate x. */
fnabs fp3,fp3 /* -(|x|+=0.5) */
.Lconvert:
fctidz fp4,fp3 /* Convert to Integer double word round toward 0. */
stfd fp4,-16(r1)
nop
nop
nop
ld r3,-16(r1) /* Load return as integer. */
.Lout:
blr
.Lretzero: /* 0.5 > x > -0.5 */
li r3,0 /* return 0. */
b .Lout
.Lnobias:
fmr fp3,fp1
b .Lconvert
END (__llround)
strong_alias (__llround, __lround)
libm_alias_double (__llround, llround)
libm_alias_double (__lround, lround)
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