sysdeps/ia64/hp-timing.h

   1 /* High precision, low overhead timing functions.  IA-64 version.
   2    Copyright (C) 2001, 2002, 2003, 2004 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4    Contributed by Ulrich Drepper <drepper@cygnus.com>, 2001.
   5
   6    The GNU C Library is free software; you can redistribute it and/or
   7    modify it under the terms of the GNU Lesser General Public
   8    License as published by the Free Software Foundation; either
   9    version 2.1 of the License, or (at your option) any later version.
  10
  11    The GNU C Library is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14    Lesser General Public License for more details.
  15
  16    You should have received a copy of the GNU Lesser General Public
  17    License along with the GNU C Library; if not, write to the Free
  18    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  19    02111-1307 USA.  */
  20
  21 #ifndef _HP_TIMING_H
  22 #define _HP_TIMING_H    1
  23
  24 #include <string.h>
  25 #include <sys/param.h>
  26 #include <stdio-common/_itoa.h>
  27 #include <ia64intrin.h>
  28
  29 /* The macros defined here use the timestamp counter in IA-64.  They
  30    provide a very accurate way to measure the time with very little
  31    overhead.  The time values themself have no real meaning, only
  32    differences are interesting.
  33
  34    The list of macros we need includes the following:
  35
  36    - HP_TIMING_AVAIL: test for availability.
  37
  38    - HP_TIMING_INLINE: this macro is non-zero if the functionality is not
  39      implemented using function calls but instead uses some inlined code
  40      which might simply consist of a few assembler instructions.  We have to
  41      know this since we might want to use the macros here in places where we
  42      cannot make function calls.
  43
  44    - hp_timing_t: This is the type for variables used to store the time
  45      values.
  46
  47    - HP_TIMING_ZERO: clear `hp_timing_t' object.
  48
  49    - HP_TIMING_NOW: place timestamp for current time in variable given as
  50      parameter.
  51
  52    - HP_TIMING_DIFF_INIT: do whatever is necessary to be able to use the
  53      HP_TIMING_DIFF macro.
  54
  55    - HP_TIMING_DIFF: compute difference between two times and store it
  56      in a third.  Source and destination might overlap.
  57
  58    - HP_TIMING_ACCUM: add time difference to another variable.  This might
  59      be a bit more complicated to implement for some platforms as the
  60      operation should be thread-safe and 64bit arithmetic on 32bit platforms
  61      is not.
  62
  63    - HP_TIMING_ACCUM_NT: this is the variant for situations where we know
  64      there are no threads involved.
  65
  66    - HP_TIMING_PRINT: write decimal representation of the timing value into
  67      the given string.  This operation need not be inline even though
  68      HP_TIMING_INLINE is specified.
  69
  70 */
  71
  72 /* We always assume having the timestamp register.  */
  73 #define HP_TIMING_AVAIL         (1)
  74
  75 /* We indeed have inlined functions.  */
  76 #define HP_TIMING_INLINE        (1)
  77
  78 /* We use 64bit values for the times.  */
  79 typedef unsigned long int hp_timing_t;
  80
  81 /* Set timestamp value to zero.  */
  82 #define HP_TIMING_ZERO(Var)     (Var) = (0)
  83
  84
  85 /* The Itanium/Merced has a bug where the ar.itc register value read
  86    is not correct in some situations.  The solution is to read again.
  87    For now we always do this until we know how to recognize a fixed
  88    processor implementation.  */
  89 #define REPEAT_READ(val) __builtin_expect ((long int) val == -1, 0)
  90
  91 /* That's quite simple.  Use the `ar.itc' instruction.  */
  92 #define HP_TIMING_NOW(Var) \
  93   ({ unsigned long int __itc;                                                 \
  94      do                                                                       \
  95        asm volatile ("mov %0=ar.itc" : "=r" (__itc) : : "memory");            \
  96      while (REPEAT_READ (__itc));                                             \
  97      Var = __itc; })
  98
  99 /* Use two 'ar.itc' instructions in a row to find out how long it takes.  */
 100 #define HP_TIMING_DIFF_INIT() \
 101   do {                                                                        \
 102     int __cnt = 5;                                                            \
 103     GLRO(dl_hp_timing_overhead) = ~0ul;                                       \
 104     do                                                                        \
 105       {                                                                       \
 106         hp_timing_t __t1, __t2;                                               \
 107         HP_TIMING_NOW (__t1);                                                 \
 108         HP_TIMING_NOW (__t2);                                                 \
 109         if (__t2 - __t1 < GLRO(dl_hp_timing_overhead))                        \
 110           GLRO(dl_hp_timing_overhead) = __t2 - __t1;                          \
 111       }                                                                       \
 112     while (--__cnt > 0);                                                      \
 113   } while (0)
 114
 115 /* It's simple arithmetic for us.  */
 116 #define HP_TIMING_DIFF(Diff, Start, End)        (Diff) = ((End) - (Start))
 117
 118 /* We have to jump through hoops to get this correctly implemented.  */
 119 #define HP_TIMING_ACCUM(Sum, Diff) \
 120   do {                                                                        \
 121     hp_timing_t __oldval;                                                     \
 122     hp_timing_t __diff = (Diff) - GLRO(dl_hp_timing_overhead);                \
 123     hp_timing_t __newval;                                                     \
 124     do                                                                        \
 125       {                                                                       \
 126         __oldval = (Sum);                                                     \
 127         __newval = __oldval + __diff;                                         \
 128       }                                                                       \
 129     while (! __sync_bool_compare_and_swap (&Sum, __oldvar, __newval));        \
 130   } while (0)
 131
 132 /* No threads, no extra work.  */
 133 #define HP_TIMING_ACCUM_NT(Sum, Diff)   (Sum) += (Diff)
 134
 135 /* Print the time value.  */
 136 #define HP_TIMING_PRINT(Buf, Len, Val) \
 137   do {                                                                        \
 138     char __buf[20];                                                           \
 139     char *__cp = _itoa_word (Val, __buf + sizeof (__buf), 10, 0);             \
 140     int __len = (Len);                                                        \
 141     char *__dest = (Buf);                                                     \
 142     while (__len-- > 0 && __cp < __buf + sizeof (__buf))                      \
 143       *__dest++ = *__cp++;                                                    \
 144     memcpy (__dest, " clock cycles", MIN (__len,                              \
 145                                           (int) sizeof (" clock cycles")));   \
 146   } while (0)
 147
 148 #endif  /* hp-timing.h */