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62 lines
2.2 KiB
C
62 lines
2.2 KiB
C
/* High precision, low overhead timing functions. x86 version.
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Copyright (C) 2018-2020 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but 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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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<https://www.gnu.org/licenses/>. */
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#ifndef _HP_TIMING_H
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#define _HP_TIMING_H 1
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#include <isa.h>
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#if MINIMUM_ISA == 686 || MINIMUM_ISA == 8664
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/* We indeed have inlined functions. */
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# define HP_TIMING_INLINE (1)
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/* We use 64bit values for the times. */
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typedef unsigned long long int hp_timing_t;
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/* That's quite simple. Use the `rdtsc' instruction. Note that the value
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might not be 100% accurate since there might be some more instructions
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running in this moment. This could be changed by using a barrier like
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'cpuid' right before the `rdtsc' instruciton. But we are not interested
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in accurate clock cycles here so we don't do this.
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NB: Use __builtin_ia32_rdtsc directly since including <x86intrin.h>
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makes building glibc very slow. */
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# ifdef USE_RDTSCP
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/* RDTSCP waits until all previous instructions have executed and all
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previous loads are globally visible before reading the counter.
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RDTSC doesn't wait until all previous instructions have been executed
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before reading the counter. */
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# define HP_TIMING_NOW(Var) \
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(__extension__ ({ \
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unsigned int __aux; \
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(Var) = __builtin_ia32_rdtscp (&__aux); \
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}))
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# else
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# define HP_TIMING_NOW(Var) ((Var) = __builtin_ia32_rdtsc ())
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# endif
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# include <hp-timing-common.h>
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#else
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/* NB: Undefine _HP_TIMING_H so that <sysdeps/generic/hp-timing.h> will
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be included. */
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# undef _HP_TIMING_H
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# include <sysdeps/generic/hp-timing.h>
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#endif
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#endif /* hp-timing.h */
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