cosmopolitan/libc/tinymath/roundl.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
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Permission to use, copy, modify, and/or distribute this software for
any purpose with or without fee is hereby granted, provided that the
above copyright notice and this permission notice appear in all copies.
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THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL
WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE
AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
PERFORMANCE OF THIS SOFTWARE.
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*/
#include "ape/lib/pc.h"
#include "libc/macros.h"
// Rounds to nearest integer, away from zero.
//
// @param 𝑥 is an 80-bit long double passed on stack in 16-bytes
// @return result of exponentiation on FPU stack in %st
roundl: push %rbp
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mov %rsp,%rbp
.profilable
push %rax
fldt 16(%rbp)
fnstcw -6(%rbp)
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fnstcw -8(%rbp)
orb $0b00001100,-7(%rbp) # RC = 0
fxam # C1 is set to sign bit
fnstsw
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fabs
test $FPU_C1>>8,%ah
fadds .Lhalf(%rip)
fldcw -8(%rbp)
frndint
fldcw -6(%rbp)
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je 1f
fchs
1: leave
ret
.endfn roundl,globl
.source __FILE__
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.rodata.cst4
.Lhalf: .float .5