cosmopolitan/libc/tinymath/round.S

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/*-*- mode:unix-assembly; indent-tabs-mode:t; tab-width:8; coding:utf-8 -*-│
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vi: set et ft=asm ts=8 tw=8 fenc=utf-8 :vi
Copyright 2020 Justine Alexandra Roberts Tunney
This program is free software; you can redistribute it and/or modify │
it under the terms of the GNU General Public License as published by
the Free Software Foundation; version 2 of the License. │
This program 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
General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software │
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
02110-1301 USA
*/
#include "libc/macros.h"
#include "libc/bits/smmintrin.h"
#include "libc/nexgen32e/x86feature.h"
.source __FILE__
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/ Rounds to nearest integer, away from zero.
/
/ @param 𝑥 is double scalar in low half of %xmm0
/ @return double scalar in low half of %xmm0
/ @define round(𝑥) = copysign(trunc(fabs(𝑥)+.5),𝑥)
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/ round(𝑥) = trunc(𝑥+copysign(.5,𝑥))
tinymath_round:
#if !X86_NEED(SSE4_2)
testb X86_HAVE(SSE4_2)+kCpuids(%rip)
jz tinymath_round$k8
.text.antiquity
tinymath_round$k8:
.leafprologue
.profilable
movapd %xmm0,%xmm1
movsd D(%rip),%xmm2
movsd C(%rip),%xmm3
andpd %xmm2,%xmm1
ucomisd %xmm1,%xmm3
jbe 2f
addsd A(%rip),%xmm1
andnpd %xmm0,%xmm2
movapd %xmm2,%xmm0
cvttsd2siq %xmm1,%rax
pxor %xmm1,%xmm1
cvtsi2sdq %rax,%xmm1
orpd %xmm1,%xmm0
2: .leafepilogue
.endfn tinymath_round$k8,globl,hidden
.previous
.rodata.cst16
C: .quad 0x4330000000000000,0
D: .quad 0x7fffffffffffffff,0
.previous
#endif
movapd %xmm0,%xmm1
andpd B(%rip),%xmm0
orpd A(%rip),%xmm0
addsd %xmm1,%xmm0
roundsd $_MM_FROUND_TO_ZERO,%xmm0,%xmm0
ret
.endfn tinymath_round,globl
.alias tinymath_round,round
.rodata.cst16
A: .quad 0x3fdfffffffffffff,0
B: .quad 0x8000000000000000,0