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50 lines
2.5 KiB
C
50 lines
2.5 KiB
C
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/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
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│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi│
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╞══════════════════════════════════════════════════════════════════════════════╡
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│ Copyright 2021 Justine Alexandra Roberts Tunney │
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│ │
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│ Permission to use, copy, modify, and/or distribute this software for │
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│ any purpose with or without fee is hereby granted, provided that the │
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│ above copyright notice and this permission notice appear in all copies. │
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│ │
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│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL │
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│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED │
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│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE │
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│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL │
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│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR │
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│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER │
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│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR │
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│ PERFORMANCE OF THIS SOFTWARE. │
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╚─────────────────────────────────────────────────────────────────────────────*/
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#include "libc/runtime/fenv.h"
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/**
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* Sets rounding mode.
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*
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* This configures the x87 FPU as well as SSE.
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*
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* @param mode may be FE_TONEAREST, FE_DOWNWARD, FE_UPWARD, or FE_TOWARDZERO
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* @return 0 on success, or -1 on error
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*/
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int fesetround(int mode) {
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uint16_t x87cw;
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uint32_t ssecw;
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switch (mode) {
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case FE_TONEAREST:
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case FE_DOWNWARD:
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case FE_UPWARD:
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case FE_TOWARDZERO:
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asm("fnstcw\t%0" : "=m"(x87cw));
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x87cw &= ~0x0c00;
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x87cw |= mode;
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asm volatile("fldcw\t%0" : /* no outputs */ : "m"(x87cw));
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asm("stmxcsr\t%0" : "=m"(ssecw));
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ssecw &= ~(0x0c00 << 3);
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ssecw |= (mode << 3);
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asm volatile("ldmxcsr\t%0" : /* no outputs */ : "m"(ssecw));
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return 0;
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default:
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return -1;
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}
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}
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