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https://github.com/jart/cosmopolitan.git
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23d333c090
This change includes many bug fixes, for the NT polyfills, strings, memory, boot, and math libraries which were discovered by adding more tools for recreational programming, such as PC emulation. Lemon has also been vendored because it works so well at parsing languages.
97 lines
3.6 KiB
C
97 lines
3.6 KiB
C
/*-*- 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 2020 Justine Alexandra Roberts Tunney │
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│ │
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│ This program is free software; you can redistribute it and/or modify │
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│ it under the terms of the GNU General Public License as published by │
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│ the Free Software Foundation; version 2 of the License. │
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│ │
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│ This program is distributed in the hope that it will be useful, but │
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│ WITHOUT ANY WARRANTY; without even the implied warranty of │
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│ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU │
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│ General Public License for more details. │
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│ │
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│ You should have received a copy of the GNU General Public License │
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│ along with this program; if not, write to the Free Software │
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│ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA │
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│ 02110-1301 USA │
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╚─────────────────────────────────────────────────────────────────────────────*/
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#include "libc/bits/bits.h"
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#include "libc/bits/initializer.h"
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#include "libc/bits/safemacros.h"
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#include "libc/calls/calls.h"
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#include "libc/dce.h"
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#include "libc/nexgen32e/rdtsc.h"
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#include "libc/nexgen32e/x86feature.h"
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#include "libc/sysv/consts/clock.h"
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#include "libc/time/time.h"
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static struct Now {
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bool once;
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uint64_t k0;
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long double r0, cpn;
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} now_;
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/**
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* Returns timestamp without needing system calls.
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* @note uses microsecond scale fallback on k8 or vm
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*/
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long double (*nowl)(void);
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static long double GetTimeSample(void) {
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uint64_t tick1, tick2;
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long double time1, time2;
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sched_yield();
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time1 = dtime(CLOCK_MONOTONIC);
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tick1 = rdtsc();
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nanosleep(&(struct timespec){0, 100000}, NULL);
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time2 = dtime(CLOCK_MONOTONIC);
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tick2 = rdtsc();
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return (time2 - time1) * 1e9 / (tick2 - tick1);
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}
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static long double MeasureNanosPerCycle(void) {
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int i;
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long double avg, samp;
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for (avg = 1.0L, i = 1; i < 5; ++i) {
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samp = GetTimeSample();
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avg += (samp - avg) / i;
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}
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return avg;
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}
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static void InitTime(void) {
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now_.cpn = MeasureNanosPerCycle();
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now_.r0 = dtime(CLOCK_REALTIME);
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now_.k0 = rdtsc();
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now_.once = true;
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}
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long double converttickstonanos(uint64_t ticks) {
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if (!now_.once) InitTime();
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return ticks * now_.cpn; /* pico scale */
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}
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long double converttickstoseconds(uint64_t ticks) {
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return 1 / 1e9 * converttickstonanos(ticks);
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}
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long double nowl$sys(void) {
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return dtime(CLOCK_REALTIME);
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}
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long double nowl$art(void) {
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uint64_t ticks;
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if (!now_.once) InitTime();
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ticks = unsignedsubtract(rdtsc(), now_.k0);
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return now_.r0 + converttickstoseconds(ticks);
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}
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INITIALIZER(301, _init_nowl, {
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if (X86_HAVE(INVTSC)) {
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nowl = nowl$art;
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} else {
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nowl = nowl$sys;
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}
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})
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