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/* High precision, low overhead timing functions. powerpc64 version.
Copyright (C) 2005-2013 Free Software Foundation, Inc.
This file is part of the GNU C Library.
Contributed by Ulrich Drepper <drepper@cygnus.com>, 1998.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<http://www.gnu.org/licenses/>. */
#ifndef _HP_TIMING_H
#define _HP_TIMING_H 1
#include <string.h>
#include <sys/param.h>
#include <_itoa.h>
#include <atomic.h>
/* The macros defined here use the powerpc 64-bit time base register.
The time base is nominally clocked at 1/8th the CPU clock, but this
can vary.
The list of macros we need includes the following:
- HP_TIMING_AVAIL: test for availability.
- HP_TIMING_INLINE: this macro is non-zero if the functionality is not
implemented using function calls but instead uses some inlined code
which might simply consist of a few assembler instructions. We have to
know this since we might want to use the macros here in places where we
cannot make function calls.
- hp_timing_t: This is the type for variables used to store the time
values.
- HP_TIMING_ZERO: clear `hp_timing_t' object.
- HP_TIMING_NOW: place timestamp for current time in variable given as
parameter.
- HP_TIMING_DIFF_INIT: do whatever is necessary to be able to use the
HP_TIMING_DIFF macro.
- HP_TIMING_DIFF: compute difference between two times and store it
in a third. Source and destination might overlap.
- HP_TIMING_ACCUM: add time difference to another variable. This might
be a bit more complicated to implement for some platforms as the
operation should be thread-safe and 64bit arithmetic on 32bit platforms
is not.
- HP_TIMING_ACCUM_NT: this is the variant for situations where we know
there are no threads involved.
- HP_TIMING_PRINT: write decimal representation of the timing value into
the given string. This operation need not be inline even though
HP_TIMING_INLINE is specified.
*/
/* We always assume having the timestamp register. */
#define HP_TIMING_AVAIL (1)
/* We indeed have inlined functions. */
#define HP_TIMING_INLINE (1)
/* We use 64bit values for the times. */
typedef unsigned long long int hp_timing_t;
/* Set timestamp value to zero. */
#define HP_TIMING_ZERO(Var) (Var) = (0)
/* That's quite simple. Use the `mftb' instruction. Note that the value
might not be 100% accurate since there might be some more instructions
running in this moment. This could be changed by using a barrier like
'lwsync' right before the `mftb' instruciton. But we are not interested
in accurate clock cycles here so we don't do this. */
#ifdef _ARCH_PWR4
#define HP_TIMING_NOW(Var) __asm__ __volatile__ ("mfspr %0,268" : "=r" (Var))
#else
#define HP_TIMING_NOW(Var) __asm__ __volatile__ ("mftb %0" : "=r" (Var))
#endif
/* Use two 'mftb' instructions in a row to find out how long it takes.
On current POWER4, POWER5, and 970 processors mftb take ~10 cycles. */
#define HP_TIMING_DIFF_INIT() \
do { \
if (GLRO(dl_hp_timing_overhead) == 0) \
{ \
int __cnt = 5; \
GLRO(dl_hp_timing_overhead) = ~0ull; \
do \
{ \
hp_timing_t __t1, __t2; \
HP_TIMING_NOW (__t1); \
HP_TIMING_NOW (__t2); \
if (__t2 - __t1 < GLRO(dl_hp_timing_overhead)) \
GLRO(dl_hp_timing_overhead) = __t2 - __t1; \
} \
while (--__cnt > 0); \
} \
} while (0)
/* It's simple arithmetic in 64-bit. */
#define HP_TIMING_DIFF(Diff, Start, End) (Diff) = ((End) - (Start))
/* We need to insure that this add is atomic in threaded environments. We use
__arch_atomic_exchange_and_add_64 from atomic.h to get thread safety. */
#define HP_TIMING_ACCUM(Sum, Diff) \
do { \
hp_timing_t __diff = (Diff) - GLRO(dl_hp_timing_overhead); \
__arch_atomic_exchange_and_add_64 (&(Sum), __diff); \
} while (0)
/* No threads, no extra work. */
#define HP_TIMING_ACCUM_NT(Sum, Diff) (Sum) += (Diff)
/* Print the time value. */
#define HP_TIMING_PRINT(Buf, Len, Val) \
do { \
char __buf[20]; \
char *__cp = _itoa (Val, __buf + sizeof (__buf), 10, 0); \
size_t __len = (Len); \
char *__dest = (Buf); \
while (__len-- > 0 && __cp < __buf + sizeof (__buf)) \
*__dest++ = *__cp++; \
memcpy (__dest, " ticks", MIN (__len, sizeof (" ticks"))); \
} while (0)
#endif /* hp-timing.h */
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