High-precision timing functions.
authordrepper <drepper>
Tue, 24 Apr 2001 05:16:21 +0000 (05:16 +0000)
committerdrepper <drepper>
Tue, 24 Apr 2001 05:16:21 +0000 (05:16 +0000)
sysdeps/ia64/hp-timing.h [new file with mode: 0644]

diff --git a/sysdeps/ia64/hp-timing.h b/sysdeps/ia64/hp-timing.h
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+/* High precision, low overhead timing functions.  IA-64 version.
+   Copyright (C) 2001 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+   Contributed by Ulrich Drepper <drepper@cygnus.com>, 2001.
+
+   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>
+#include <ia64intrin.h>
+
+/* The macros defined here use the timestamp counter in IA-64.  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.
+
+   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 int hp_timing_t;
+
+/* Internal variable 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)
+
+
+/* The Itanium/Merced has a bug where the ar.itc register value read
+   is not correct in some situations.  The solution is to read again.
+   For now we always do this until we know how to recognize a fixed
+   processor implementation.  */
+#define REPEAT_READ(val) __builtin_expect ((int) val == -1, 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) \
+  ({ unsigned long int __itc;                                                \
+     do                                                                              \
+       asm volatile ("mov %0=ar.itc" : "=r" (__itc) : : "memory");           \
+     while (REPEAT_READ (__itc));                                            \
+     Var = __itc; })
+
+/* Use two 'ar.itc' instructions in a row to find out how long it takes.  */
+#define HP_TIMING_DIFF_INIT() \
+  do {                                                                       \
+    int __cnt = 5;                                                           \
+    __libc_hp_timing_overhead = ~0ul;                                        \
+    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 {                                                                       \
+    hp_timing_t __oldval;                                                    \
+    hp_timing_t __diff = (Diff) - __libc_hp_timing_overhead;                 \
+    hp_timing_t __newval;                                                    \
+    do                                                                       \
+      {                                                                              \
+       __oldval = (Sum);                                                     \
+       __newval = __oldval + __diff;                                         \
+      }                                                                              \
+    while (! __sync_bool_compare_and_swap (&Sum, __oldvar, __newval));       \
+  } 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_word (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 */