cosmopolitan/libc/runtime/fastmath.S

46 lines
2.6 KiB
ArmAsm

/*-*- mode:unix-assembly; indent-tabs-mode:t; tab-width:8; coding:utf-8 -*-│
vi: set et ft=asm ts=8 sw=8 fenc=utf-8 :vi
Copyright 2020 Justine Alexandra Roberts Tunney
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.
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.
*/
#include "libc/macros.h"
#include "libc/notice.inc"
.text.startup
.source __FILE__
/ Intel Manual V.1 §10.2.3 - MXCSR Control and Status Register
#define MXCSR_DE (1 << 1) /* Denormal Flag */
#define MXCSR_DAZ (1 << 6) /* Denormals Are Zeros */
#define MXCSR_DM (1 << 8) /* Denormal Operation Mask */
#define MXCSR_FTZ (1 << 15) /* Flush to Zero */
/ Initializes fast math.
/
/ Seymour Cray didn't care that 81.0/3.0 did not give exactly
/ 27.0 on the CDC 6000 class machines, and he was universally
/ respected for making the fastest machines around.
/ Linus Torvalds
__fast_math:
push %rbp
mov %rsp,%rbp
push %rax
stmxcsr (%rsp)
orl $MXCSR_FTZ+MXCSR_DAZ,(%rsp)
ldmxcsr (%rsp)
leave
ret
.endfn __fast_math,globl