cosmopolitan/libc/runtime/fesetround.c
Justine Tunney 8f52c0d773 Get Fabrice Bellard's JavaScript engine to build
$ m=tiny
$ make -j12 MODE=$m o/$m/third_party/quickjs/qjs.com
$ o/$m/third_party/quickjs/qjs.com -e 'console.log(2 + 2)'
4
$ ls -hal o/$m/third_party/quickjs/qjs.com
631.5K

See #97
2021-04-09 01:06:57 -07:00

51 lines
2.6 KiB
C

/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi│
╞══════════════════════════════════════════════════════════════════════════════╡
│ Copyright 2021 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/runtime/fenv.h"
/* TODO(jart): This needs tests. */
/**
* Sets rounding mode.
*
* This configures the x87 FPU as well as SSE.
*
* @param mode may be FE_TONEAREST, FE_DOWNWARD, FE_UPWARD, or FE_TOWARDZERO
* @return 0 on success, or -1 on error
*/
int fesetround(int mode) {
uint16_t x87cw;
uint32_t ssecw;
switch (mode) {
case FE_TONEAREST:
case FE_DOWNWARD:
case FE_UPWARD:
case FE_TOWARDZERO:
asm("fnstcw\t%0" : "=m"(x87cw));
x87cw &= ~0x0c00;
x87cw |= mode;
asm volatile("fldcw\t%0" : /* no outputs */ : "m"(x87cw));
asm("stmxcsr\t%0" : "=m"(ssecw));
ssecw &= ~(0x0c00 << 3);
ssecw |= (mode << 3);
asm volatile("ldmxcsr\t%0" : /* no outputs */ : "m"(ssecw));
return 0;
default:
return -1;
}
}