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Diffstat (limited to 'sysdeps/i386/i686/hp-timing.h')
| -rw-r--r-- | sysdeps/i386/i686/hp-timing.h | 160 |
1 files changed, 160 insertions, 0 deletions
diff --git a/sysdeps/i386/i686/hp-timing.h b/sysdeps/i386/i686/hp-timing.h new file mode 100644 index 0000000..ffbeb27 --- /dev/null +++ b/sysdeps/i386/i686/hp-timing.h @@ -0,0 +1,160 @@ +/* High precision, low overhead timing functions. i686 version. + Copyright (C) 1998 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 Library General Public License as + published by the Free Software Foundation; either version 2 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 + Library General Public License for more details. + + You should have received a copy of the GNU Library General Public + License along with the GNU C Library; see the file COPYING.LIB. If not, + write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330, + Boston, MA 02111-1307, USA. */ + +#ifndef _HP_TIMING_H +#define _HP_TIMING_H 1 + +#include <string.h> +#include <sys/param.h> +#include <stdio-common/_itoa.h> + +/* The macros defined here use the timestamp counter in i586 and up versions + of the x86 processors. They provide a very accurate way to measure the + time with very little overhead. The time values themself have no real + meaning, only differences are interesting. + + This version is for the i686 processors. The difference to the i586 + version is that the timerstamp register is unconditionally used. This is + not the case for the i586 version where we have to perform runtime test + whether the processor really has this capability. We have to make this + distinction since the sysdeps/i386/i586 code is supposed to work on all + platforms while the i686 already contains i686-specific code. + + 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; + +/* Internal variabled used to store the overhead of the measurement + opcodes. */ +extern hp_timing_t __libc_hp_timing_overhead; + +/* Set timestamp value to zero. */ +#define HP_TIMING_ZERO(Var) (Var) = (0) + +/* That's quite simple. Use the `rdtsc' 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 + 'cpuid' right before the `rdtsc' instruciton. But we are not interested + in accurate clock cycles here so we don't do this. */ +#define HP_TIMING_NOW(Var) __asm__ __volatile__ ("rdtsc" : "=A" (Var)) + +/* Use two 'rdtsc' instructions in a row to find out how long it takes. */ +#define HP_TIMING_DIFF_INIT() \ + do { \ + int __cnt = 5; \ + __libc_hp_timing_overhead = ~0ull; \ + do \ + { \ + hp_timing_t __t1, __t2; \ + HP_TIMING_NOW (__t1); \ + HP_TIMING_NOW (__t2); \ + if (__t2 - __t1 < __libc_hp_timing_overhead) \ + __libc_hp_timing_overhead = __t2 - __t1; \ + } \ + while (--__cnt > 0); \ + } while (0) + +/* It's simple arithmetic for us. */ +#define HP_TIMING_DIFF(Diff, Start, End) (Diff) = ((End) - (Start)) + +/* We have to jump through hoops to get this correctly implemented. */ +#define HP_TIMING_ACCUM(Sum, Diff) \ + do { \ + char __not_done; \ + hp_timing_t __oldval = (Sum); \ + hp_timing_t __diff = (Diff) - __libc_hp_timing_overhead; \ + do \ + { \ + hp_timing_t __newval = __oldval + __diff; \ + int __temp0, __temp1; \ + __asm__ __volatile__ ("xchgl %4, %%ebx\n\t" \ + "lock; cmpxchg8b %1\n\t" \ + "sete %0\n\t" \ + "movl %4, %%ebx" \ + : "=q" (__not_done), "=m" (Sum), \ + "=A" (__oldval), "=c" (__temp0), \ + "=SD" (__temp1) \ + : "1" (Sum), "2" (__oldval), \ + "3" (__newval >> 32), \ + "4" (__newval & 0xffffffff) \ + : "memory"); \ + } \ + while (__not_done); \ + } 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); \ + int __len = (Len); \ + char *__dest = (Buf); \ + while (__len-- > 0 && __cp < __buf + sizeof (__buf)) \ + *__dest++ = *__cp++; \ + memcpy (__dest, " clock cycles", MIN (__len, sizeof (" clock cycles"))); \ + } while (0) + +#endif /* hp-timing.h */ |