Initial commit.

1 files changed, 1598 insertions, 0 deletions

diff --git a/gmp-6.3.0/tune/time.c b/gmp-6.3.0/tune/time.c
new file mode 100644
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--- /dev/null
+++ b/gmp-6.3.0/tune/time.c
@@ -0,0 +1,1598 @@
+/* Time routines for speed measurements.
+
+Copyright 1999-2004, 2010-2012 Free Software Foundation, Inc.
+
+This file is part of the GNU MP Library.
+
+The GNU MP Library is free software; you can redistribute it and/or modify
+it under the terms of either:
+
+  * the GNU Lesser General Public License as published by the Free
+    Software Foundation; either version 3 of the License, or (at your
+    option) any later version.
+
+or
+
+  * the GNU General Public License as published by the Free Software
+    Foundation; either version 2 of the License, or (at your option) any
+    later version.
+
+or both in parallel, as here.
+
+The GNU MP 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 General Public License
+for more details.
+
+You should have received copies of the GNU General Public License and the
+GNU Lesser General Public License along with the GNU MP Library.  If not,
+see https://www.gnu.org/licenses/.  */
+
+
+/* Usage:
+
+   The code in this file implements the lowest level of time measuring,
+   simple one-time measuring of time between two points.
+
+   void speed_starttime (void)
+   double speed_endtime (void)
+       Call speed_starttime to start measuring, and then call speed_endtime
+       when done.
+
+       speed_endtime returns the time taken, in seconds.  Or if the timebase
+       is in CPU cycles and the CPU frequency is unknown then speed_endtime
+       returns cycles.  Applications can identify the cycles return by
+       checking for speed_cycletime (described below) equal to 1.0.
+
+       If some sort of temporary glitch occurs then speed_endtime returns
+       0.0.  Currently this is for various cases where a negative time has
+       occurred.  This unfortunately occurs with getrusage on some systems,
+       and with the hppa cycle counter on hpux.
+
+   double speed_cycletime
+       The time in seconds for each CPU cycle.  For example on a 100 MHz CPU
+       this would be 1.0e-8.
+
+       If the CPU frequency is unknown, then speed_cycletime is either 0.0
+       or 1.0.  It's 0.0 when speed_endtime is returning seconds, or it's
+       1.0 when speed_endtime is returning cycles.
+
+       It may be noted that "speed_endtime() / speed_cycletime" gives a
+       measured time in cycles, irrespective of whether speed_endtime is
+       returning cycles or seconds.  (Assuming cycles can be had, ie. it's
+       either cycles already or the cpu frequency is known.  See also
+       speed_cycletime_need_cycles below.)
+
+   double speed_unittime
+       The unit of time measurement accuracy for the timing method in use.
+       This is in seconds or cycles, as per speed_endtime.
+
+   char speed_time_string[]
+       A null-terminated string describing the time method in use.
+
+   void speed_time_init (void)
+       Initialize time measuring.  speed_starttime() does this
+       automatically, so it's only needed if an application wants to inspect
+       the above global variables before making a measurement.
+
+   int speed_precision
+       The intended accuracy of time measurements.  speed_measure() in
+       common.c for instance runs target routines with enough repetitions so
+       it takes at least "speed_unittime * speed_precision" (this expression
+       works for both cycles or seconds from speed_endtime).
+
+       A program can provide an option so the user to set speed_precision.
+       If speed_precision is zero when speed_time_init or speed_starttime
+       first run then it gets a default based on the measuring method
+       chosen.  (More precision for higher accuracy methods.)
+
+   void speed_cycletime_need_seconds (void)
+       Call this to demand that speed_endtime will return seconds, and not
+       cycles.  If only cycles are available then an error is printed and
+       the program exits.
+
+   void speed_cycletime_need_cycles (void)
+       Call this to demand that speed_cycletime is non-zero, so that
+       "speed_endtime() / speed_cycletime" will give times in cycles.
+
+
+
+   Notes:
+
+   Various combinations of cycle counter, read_real_time(), getrusage(),
+   gettimeofday() and times() can arise, according to which are available
+   and their precision.
+
+
+   Allowing speed_endtime() to return either seconds or cycles is only a
+   slight complication and makes it possible for the speed program to do
+   some sensible things without demanding the CPU frequency.  If seconds are
+   being measured then it can always print seconds, and if cycles are being
+   measured then it can always print them without needing to know how long
+   they are.  Also the tune program doesn't care at all what the units are.
+
+   GMP_CPU_FREQUENCY can always be set when the automated methods in freq.c
+   fail.  This will be needed if times in seconds are wanted but a cycle
+   counter is being used, or if times in cycles are wanted but getrusage or
+   another seconds based timer is in use.
+
+   If the measuring method uses a cycle counter but supplements it with
+   getrusage or the like, then knowing the CPU frequency is mandatory since
+   the code compares values from the two.
+
+
+   Not done:
+
+   Solaris gethrtime() seems no more than a slow way to access the Sparc V9
+   cycle counter.  gethrvtime() seems to be relevant only to light weight
+   processes, it doesn't for instance give nanosecond virtual time.  So
+   neither of these are used.
+
+
+   Bugs:
+
+   getrusage_microseconds_p is fundamentally flawed, getrusage and
+   gettimeofday can have resolutions other than clock ticks or microseconds,
+   for instance IRIX 5 has a tick of 10 ms but a getrusage of 1 ms.
+
+
+   Enhancements:
+
+   The SGI hardware counter has 64 bits on some machines, which could be
+   used when available.  But perhaps 32 bits is enough range, and then rely
+   on the getrusage supplement.
+
+   Maybe getrusage (or times) should be used as a supplement for any
+   wall-clock measuring method.  Currently a wall clock with a good range
+   (eg. a 64-bit cycle counter) is used without a supplement.
+
+   On PowerPC the timebase registers could be used, but would have to do
+   something to find out the speed.  On 6xx chips it's normally 1/4 bus
+   speed, on 4xx chips it's either that or an external clock.  Measuring
+   against gettimeofday might be ok.  */
+
+
+#include "config.h"
+
+#include <errno.h>
+#include <setjmp.h>
+#include <signal.h>
+#include <stddef.h>
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h> /* for getenv() */
+
+#if HAVE_FCNTL_H
+#include <fcntl.h>  /* for open() */
+#endif
+
+#if HAVE_STDINT_H
+#include <stdint.h> /* for uint64_t */
+#endif
+
+#if HAVE_UNISTD_H
+#include <unistd.h> /* for sysconf() */
+#endif
+
+#include <sys/types.h>
+
+#if TIME_WITH_SYS_TIME
+# include <sys/time.h>  /* for struct timeval */
+# include <time.h>
+#else
+# if HAVE_SYS_TIME_H
+#  include <sys/time.h>
+# else
+#  include <time.h>
+# endif
+#endif
+
+#if HAVE_SYS_MMAN_H
+#include <sys/mman.h>      /* for mmap() */
+#endif
+
+#if HAVE_SYS_RESOURCE_H
+#include <sys/resource.h>  /* for struct rusage */
+#endif
+
+#if HAVE_SYS_SYSSGI_H
+#include <sys/syssgi.h>    /* for syssgi() */
+#endif
+
+#if HAVE_SYS_SYSTEMCFG_H
+#include <sys/systemcfg.h> /* for RTC_POWER on AIX */
+#endif
+
+#if HAVE_SYS_TIMES_H
+#include <sys/times.h>  /* for times() and struct tms */
+#endif
+
+#include "gmp-impl.h"
+
+#include "speed.h"
+
+
+/* strerror is only used for some stuff on newish systems, no need to have a
+   proper replacement */
+#if ! HAVE_STRERROR
+#define strerror(n)  "<strerror not available>"
+#endif
+
+
+char    speed_time_string[256];
+int     speed_precision = 0;
+double  speed_unittime;
+double  speed_cycletime = 0.0;
+
+
+/* don't rely on "unsigned" to "double" conversion, it's broken in SunOS 4
+   native cc */
+#define M_2POWU   (((double) INT_MAX + 1.0) * 2.0)
+
+#define M_2POW32  4294967296.0
+#define M_2POW64  (M_2POW32 * M_2POW32)
+
+
+/* Conditionals for the time functions available are done with normal C
+   code, which is a lot easier than wildly nested preprocessor directives.
+
+   The choice of what to use is partly made at run-time, according to
+   whether the cycle counter works and the measured accuracy of getrusage
+   and gettimeofday.
+
+   A routine that's not available won't be getting called, but is an abort()
+   to be sure it isn't called mistakenly.
+
+   It can be assumed that if a function exists then its data type will, but
+   if the function doesn't then the data type might or might not exist, so
+   the type can't be used unconditionally.  The "struct_rusage" etc macros
+   provide dummies when the respective function doesn't exist. */
+
+
+#if HAVE_SPEED_CYCLECOUNTER
+static const int have_cycles = HAVE_SPEED_CYCLECOUNTER;
+#else
+static const int have_cycles = 0;
+#define speed_cyclecounter(p)  ASSERT_FAIL (speed_cyclecounter not available)
+#endif
+
+/* "stck" returns ticks since 1 Jan 1900 00:00 GMT, where each tick is 2^-12
+   microseconds.  Same #ifdefs here as in longlong.h.  */
+#if defined (__GNUC__) && ! defined (NO_ASM)                            \
+  && (defined (__i370__) || defined (__s390__) || defined (__mvs__))
+static const int  have_stck = 1;
+static const int  use_stck = 1;  /* always use when available */
+typedef uint64_t  stck_t; /* gcc for s390 is quite new, always has uint64_t */
+#define STCK(timestamp)                 \
+  do {                                  \
+    asm ("stck %0" : "=Q" (timestamp)); \
+  } while (0)
+#else
+static const int  have_stck = 0;
+static const int  use_stck = 0;
+typedef unsigned long  stck_t;   /* dummy */
+#define STCK(timestamp)  ASSERT_FAIL (stck instruction not available)
+#endif
+#define STCK_PERIOD      (1.0 / 4096e6)   /* 2^-12 microseconds */
+
+/* mftb
+   Enhancement: On 64-bit chips mftb gives a 64-bit value, no need for mftbu
+   and a loop (see powerpc64.asm).  */
+#if HAVE_HOST_CPU_FAMILY_powerpc
+static const int  have_mftb = 1;
+#if defined (__GNUC__) && ! defined (NO_ASM)
+#define MFTB(a)                         \
+  do {                                  \
+    unsigned  __h1, __l, __h2;          \
+    do {                                \
+      asm volatile ("mftbu %0\n"        \
+		    "mftb  %1\n"        \
+		    "mftbu %2"          \
+		    : "=r" (__h1),      \
+		      "=r" (__l),       \
+		      "=r" (__h2));     \
+    } while (__h1 != __h2);             \
+    a[0] = __l;                         \
+    a[1] = __h1;                        \
+  } while (0)
+#else
+#define MFTB(a)   mftb_function (a)
+#endif
+#else /* ! powerpc */
+static const int  have_mftb = 0;
+#define MFTB(a)                         \
+  do {                                  \
+    a[0] = 0;                           \
+    a[1] = 0;                           \
+    ASSERT_FAIL (mftb not available);   \
+  } while (0)
+#endif
+
+/* Unicos 10.X has syssgi(), but not mmap(). */
+#if HAVE_SYSSGI && HAVE_MMAP
+static const int  have_sgi = 1;
+#else
+static const int  have_sgi = 0;
+#endif
+
+#if HAVE_READ_REAL_TIME
+static const int have_rrt = 1;
+#else
+static const int have_rrt = 0;
+#define read_real_time(t,s)     ASSERT_FAIL (read_real_time not available)
+#define time_base_to_time(t,s)  ASSERT_FAIL (time_base_to_time not available)
+#define RTC_POWER     1
+#define RTC_POWER_PC  2
+#define timebasestruct_t   struct timebasestruct_dummy
+struct timebasestruct_dummy {
+  int             flag;
+  unsigned int    tb_high;
+  unsigned int    tb_low;
+};
+#endif
+
+#if HAVE_CLOCK_GETTIME
+static const int have_cgt = 1;
+#define struct_timespec  struct timespec
+#else
+static const int have_cgt = 0;
+#define struct_timespec       struct timespec_dummy
+#define clock_gettime(id,ts)  (ASSERT_FAIL (clock_gettime not available), -1)
+#define clock_getres(id,ts)   (ASSERT_FAIL (clock_getres not available), -1)
+#endif
+
+#if HAVE_GETRUSAGE
+static const int have_grus = 1;
+#define struct_rusage   struct rusage
+#else
+static const int have_grus = 0;
+#define getrusage(n,ru)  ASSERT_FAIL (getrusage not available)
+#define struct_rusage    struct rusage_dummy
+#endif
+
+#if HAVE_GETTIMEOFDAY
+static const int have_gtod = 1;
+#define struct_timeval   struct timeval
+#else
+static const int have_gtod = 0;
+#define gettimeofday(tv,tz)  ASSERT_FAIL (gettimeofday not available)
+#define struct_timeval   struct timeval_dummy
+#endif
+
+#if HAVE_TIMES
+static const int have_times = 1;
+#define struct_tms   struct tms
+#else
+static const int have_times = 0;
+#define times(tms)   ASSERT_FAIL (times not available)
+#define struct_tms   struct tms_dummy
+#endif
+
+struct tms_dummy {
+  long  tms_utime;
+};
+struct timeval_dummy {
+  long  tv_sec;
+  long  tv_usec;
+};
+struct rusage_dummy {
+  struct_timeval ru_utime;
+};
+struct timespec_dummy {
+  long  tv_sec;
+  long  tv_nsec;
+};
+
+static int  use_cycles;
+static int  use_mftb;
+static int  use_sgi;
+static int  use_rrt;
+static int  use_cgt;
+static int  use_gtod;
+static int  use_grus;
+static int  use_times;
+static int  use_tick_boundary;
+
+static unsigned         start_cycles[2];
+static stck_t           start_stck;
+static unsigned         start_mftb[2];
+static unsigned         start_sgi;
+static timebasestruct_t start_rrt;
+static struct_timespec  start_cgt;
+static struct_rusage    start_grus;
+static struct_timeval   start_gtod;
+static struct_tms       start_times;
+
+static double  cycles_limit = 1e100;
+static double  mftb_unittime;
+static double  sgi_unittime;
+static double  cgt_unittime;
+static double  grus_unittime;
+static double  gtod_unittime;
+static double  times_unittime;
+
+/* for RTC_POWER format, ie. seconds and nanoseconds */
+#define TIMEBASESTRUCT_SECS(t)  ((t)->tb_high + (t)->tb_low * 1e-9)
+
+
+/* Return a string representing a time in seconds, nicely formatted.
+   Eg. "10.25ms".  */
+char *
+unittime_string (double t)
+{
+  static char  buf[128];
+
+  const char  *unit;
+  int         prec;
+
+  /* choose units and scale */
+  if (t < 1e-6)
+    t *= 1e9, unit = "ns";
+  else if (t < 1e-3)
+    t *= 1e6, unit = "us";
+  else if (t < 1.0)
+    t *= 1e3, unit = "ms";
+  else
+    unit = "s";
+
+  /* want 4 significant figures */
+  if (t < 1.0)
+    prec = 4;
+  else if (t < 10.0)
+    prec = 3;
+  else if (t < 100.0)
+    prec = 2;
+  else
+    prec = 1;
+
+  sprintf (buf, "%.*f%s", prec, t, unit);
+  return buf;
+}
+
+
+static jmp_buf  cycles_works_buf;
+
+static RETSIGTYPE
+cycles_works_handler (int sig)
+{
+  longjmp (cycles_works_buf, 1);
+}
+
+int
+cycles_works_p (void)
+{
+  static int  result = -1;
+
+  if (result != -1)
+    goto done;
+
+  /* FIXME: On linux, the cycle counter is not saved and restored over
+   * context switches, making it almost useless for precise cputime
+   * measurements. When available, it's better to use clock_gettime,
+   * which seems to have reasonable accuracy (tested on x86_32,
+   * linux-2.6.26, glibc-2.7). However, there are also some linux
+   * systems where clock_gettime is broken in one way or the other,
+   * like CLOCK_PROCESS_CPUTIME_ID not implemented (easy case) or
+   * kind-of implemented but broken (needs code to detect that), and
+   * on those systems a wall-clock cycle counter is the least bad
+   * fallback.
+   *
+   * So we need some code to disable the cycle counter on some but not
+   * all linux systems. */
+#ifdef SIGILL
+  {
+    RETSIGTYPE (*old_handler) (int);
+    unsigned  cycles[2];
+
+    old_handler = signal (SIGILL, cycles_works_handler);
+    if (old_handler == SIG_ERR)
+      {
+	if (speed_option_verbose)
+	  printf ("cycles_works_p(): SIGILL not supported, assuming speed_cyclecounter() works\n");
+	goto yes;
+      }
+    if (setjmp (cycles_works_buf))
+      {
+	if (speed_option_verbose)
+	  printf ("cycles_works_p(): SIGILL during speed_cyclecounter(), so doesn't work\n");
+	result = 0;
+	goto done;
+      }
+    speed_cyclecounter (cycles);
+    signal (SIGILL, old_handler);
+    if (speed_option_verbose)
+      printf ("cycles_works_p(): speed_cyclecounter() works\n");
+  }
+#else
+
+  if (speed_option_verbose)
+    printf ("cycles_works_p(): SIGILL not defined, assuming speed_cyclecounter() works\n");
+  goto yes;
+#endif
+
+ yes:
+  result = 1;
+
+ done:
+  return result;
+}
+
+
+/* The number of clock ticks per second, but looking at sysconf rather than
+   just CLK_TCK, where possible.  */
+long
+clk_tck (void)
+{
+  static long  result = -1L;
+  if (result != -1L)
+    return result;
+
+#if HAVE_SYSCONF
+  result = sysconf (_SC_CLK_TCK);
+  if (result != -1L)
+    {
+      if (speed_option_verbose)
+	printf ("sysconf(_SC_CLK_TCK) is %ld per second\n", result);
+      return result;
+    }
+
+  fprintf (stderr,
+	   "sysconf(_SC_CLK_TCK) not working, using CLK_TCK instead\n");
+#endif
+
+#ifdef CLK_TCK
+  result = CLK_TCK;
+  if (speed_option_verbose)
+    printf ("CLK_TCK is %ld per second\n", result);
+  return result;
+#else
+  fprintf (stderr, "CLK_TCK not defined, cannot continue\n");
+  abort ();
+#endif
+}
+
+
+/* If two times can be observed less than half a clock tick apart, then
+   assume "get" is microsecond accurate.
+
+   Two times only 1 microsecond apart are not believed, since some kernels
+   take it upon themselves to ensure gettimeofday doesn't return the same
+   value twice, for the benefit of applications using it for a timestamp.
+   This is obviously very stupid given the speed of CPUs these days.
+
+   Making "reps" many calls to noop_1() is designed to waste some CPU, with
+   a view to getting measurements 2 microseconds (or more) apart.  "reps" is
+   increased progressively until such a period is seen.
+
+   The outer loop "attempts" are just to allow for any random nonsense or
+   system load upsetting the measurements (ie. making two successive calls
+   to "get" come out as a longer interval than normal).
+
+   Bugs:
+
+   The assumption that any interval less than a half tick implies
+   microsecond resolution is obviously fairly rash, the true resolution
+   could be anything between a microsecond and that half tick.  Perhaps
+   something special would have to be done on a system where this is the
+   case, since there's no obvious reliable way to detect it
+   automatically.  */
+
+#define MICROSECONDS_P(name, type, get, sec, usec)                      \
+  {                                                                     \
+    static int  result = -1;                                            \
+    type      st, et;                                                   \
+    long      dt, half_tick;                                            \
+    unsigned  attempt, reps, i, j;                                      \
+									\
+    if (result != -1)                                                   \
+      return result;                                                    \
+									\
+    result = 0;                                                         \
+    half_tick = (1000000L / clk_tck ()) / 2;                            \
+									\
+    for (attempt = 0; attempt < 5; attempt++)                           \
+      {                                                                 \
+	reps = 0;                                                       \
+	for (;;)                                                        \
+	  {                                                             \
+	    get (st);                                                   \
+	    for (i = 0; i < reps; i++)                                  \
+	      for (j = 0; j < 100; j++)                                 \
+		noop_1 (CNST_LIMB(0));                                  \
+	    get (et);                                                   \
+									\
+	    dt = (sec(et)-sec(st))*1000000L + usec(et)-usec(st);        \
+									\
+	    if (speed_option_verbose >= 2)                              \
+	      printf ("%s attempt=%u, reps=%u, dt=%ld\n",               \
+		      name, attempt, reps, dt);                         \
+									\
+	    if (dt >= 2)                                                \
+	      break;                                                    \
+									\
+	    reps = (reps == 0 ? 1 : 2*reps);                            \
+	    if (reps == 0)                                              \
+	      break;  /* uint overflow, not normal */                   \
+	  }                                                             \
+									\
+	if (dt < half_tick)                                             \
+	  {                                                             \
+	    result = 1;                                                 \
+	    break;                                                      \
+	  }                                                             \
+      }                                                                 \
+									\
+    if (speed_option_verbose)                                           \
+      {                                                                 \
+	if (result)                                                     \
+	  printf ("%s is microsecond accurate\n", name);                \
+	else                                                            \
+	  printf ("%s is only %s clock tick accurate\n",                \
+		  name, unittime_string (1.0/clk_tck()));               \
+      }                                                                 \
+    return result;                                                      \
+  }
+
+
+int
+gettimeofday_microseconds_p (void)
+{
+#define call_gettimeofday(t)   gettimeofday (&(t), NULL)
+#define timeval_tv_sec(t)      ((t).tv_sec)
+#define timeval_tv_usec(t)     ((t).tv_usec)
+  MICROSECONDS_P ("gettimeofday", struct_timeval,
+		  call_gettimeofday, timeval_tv_sec, timeval_tv_usec);
+}
+
+int
+getrusage_microseconds_p (void)
+{
+#define call_getrusage(t)   getrusage (0, &(t))
+#define rusage_tv_sec(t)    ((t).ru_utime.tv_sec)
+#define rusage_tv_usec(t)   ((t).ru_utime.tv_usec)
+  MICROSECONDS_P ("getrusage", struct_rusage,
+		  call_getrusage, rusage_tv_sec, rusage_tv_usec);
+}
+
+/* Test whether getrusage goes backwards, return non-zero if it does
+   (suggesting it's flawed).
+
+   On a macintosh m68040-unknown-netbsd1.4.1 getrusage looks like it's
+   microsecond accurate, but has been seen remaining unchanged after many
+   microseconds have elapsed.  It also regularly goes backwards by 1000 to
+   5000 usecs, this has been seen after between 500 and 4000 attempts taking
+   perhaps 0.03 seconds.  We consider this too broken for good measuring.
+   We used to have configure pretend getrusage didn't exist on this system,
+   but a runtime test should be more reliable, since we imagine the problem
+   is not confined to just this exact system tuple.  */
+
+int
+getrusage_backwards_p (void)
+{
+  static int result = -1;
+  struct rusage  start, prev, next;
+  long  d;
+  int   i;
+
+  if (result != -1)
+    return result;
+
+  getrusage (0, &start);
+  memcpy (&next, &start, sizeof (next));
+
+  result = 0;
+  i = 0;
+  for (;;)
+    {
+      memcpy (&prev, &next, sizeof (prev));
+      getrusage (0, &next);
+
+      if (next.ru_utime.tv_sec < prev.ru_utime.tv_sec
+	  || (next.ru_utime.tv_sec == prev.ru_utime.tv_sec
+	      && next.ru_utime.tv_usec < prev.ru_utime.tv_usec))
+	{
+	  if (speed_option_verbose)
+	    printf ("getrusage went backwards (attempt %d: %ld.%06ld -> %ld.%06ld)\n",
+		    i,
+		    (long) prev.ru_utime.tv_sec, (long) prev.ru_utime.tv_usec,
+		    (long) next.ru_utime.tv_sec, (long) next.ru_utime.tv_usec);
+	  result = 1;
+	  break;
+	}
+
+      /* minimum 1000 attempts, then stop after either 0.1 seconds or 50000
+	 attempts, whichever comes first */
+      d = 1000000 * (next.ru_utime.tv_sec - start.ru_utime.tv_sec)
+	+ (next.ru_utime.tv_usec - start.ru_utime.tv_usec);
+      i++;
+      if (i > 50000 || (i > 1000 && d > 100000))
+	break;
+    }
+
+  return result;
+}
+
+/* CLOCK_PROCESS_CPUTIME_ID looks like it's going to be in a future version
+   of glibc (some time post 2.2).
+
+   CLOCK_VIRTUAL is process time, available in BSD systems (though sometimes
+   defined, but returning -1 for an error).  */
+
+#ifdef CLOCK_PROCESS_CPUTIME_ID
+# define CGT_ID        CLOCK_PROCESS_CPUTIME_ID
+#else
+# ifdef CLOCK_VIRTUAL
+#  define CGT_ID       CLOCK_VIRTUAL
+# endif
+#endif
+#ifdef CGT_ID
+const int  have_cgt_id = 1;
+#else
+const int  have_cgt_id = 0;
+# define CGT_ID       (ASSERT_FAIL (CGT_ID not determined), -1)
+#endif
+
+#define CGT_DELAY_COUNT 1000
+
+int
+cgt_works_p (void)
+{
+  static int  result = -1;
+  struct_timespec  unit;
+
+  if (! have_cgt)
+    return 0;
+
+  if (! have_cgt_id)
+    {
+      if (speed_option_verbose)
+	printf ("clock_gettime don't know what ID to use\n");
+      result = 0;
+      return result;
+    }
+
+  if (result != -1)
+    return result;
+
+  /* trial run to see if it works */
+  if (clock_gettime (CGT_ID, &unit) != 0)
+    {
+      if (speed_option_verbose)
+	printf ("clock_gettime id=%d error: %s\n", CGT_ID, strerror (errno));
+      result = 0;
+      return result;
+    }
+
+  /* get the resolution */
+  if (clock_getres (CGT_ID, &unit) != 0)
+    {
+      if (speed_option_verbose)
+	printf ("clock_getres id=%d error: %s\n", CGT_ID, strerror (errno));
+      result = 0;
+      return result;
+    }
+
+  cgt_unittime = unit.tv_sec + unit.tv_nsec * 1e-9;
+  if (speed_option_verbose)
+    printf ("clock_gettime is %s accurate\n", unittime_string (cgt_unittime));
+
+  if (cgt_unittime < 10e-9)
+    {
+      /* Do we believe this? */
+      struct timespec start, end;
+      static volatile int counter;
+      double duration;
+      if (clock_gettime (CGT_ID, &start))
+	{
+	  if (speed_option_verbose)
+	    printf ("clock_gettime id=%d error: %s\n", CGT_ID, strerror (errno));
+	  result = 0;
+	  return result;
+	}
+      /* Loop of at least 1000 memory accesses, ought to take at
+	 least 100 ns*/
+      for (counter = 0; counter < CGT_DELAY_COUNT; counter++)
+	;
+      if (clock_gettime (CGT_ID, &end))
+	{
+	  if (speed_option_verbose)
+	    printf ("clock_gettime id=%d error: %s\n", CGT_ID, strerror (errno));
+	  result = 0;
+	  return result;
+	}
+      duration = (end.tv_sec + end.tv_nsec * 1e-9
+		  - start.tv_sec - start.tv_nsec * 1e-9);
+      if (speed_option_verbose)
+	printf ("delay loop of %d rounds took %s (according to clock_gettime)\n",
+		CGT_DELAY_COUNT, unittime_string (duration));
+      if (duration < 100e-9)
+	{
+	  if (speed_option_verbose)
+	    printf ("clock_gettime id=%d not believable\n", CGT_ID);
+	  result = 0;
+	  return result;
+	}
+    }
+  result = 1;
+  return result;
+}
+
+
+static double
+freq_measure_mftb_one (void)
+{
+#define call_gettimeofday(t)   gettimeofday (&(t), NULL)
+#define timeval_tv_sec(t)      ((t).tv_sec)
+#define timeval_tv_usec(t)     ((t).tv_usec)
+  FREQ_MEASURE_ONE ("mftb", struct_timeval,
+		    call_gettimeofday, MFTB,
+		    timeval_tv_sec, timeval_tv_usec);
+}
+
+
+static jmp_buf  mftb_works_buf;
+
+static RETSIGTYPE
+mftb_works_handler (int sig)
+{
+  longjmp (mftb_works_buf, 1);
+}
+
+int
+mftb_works_p (void)
+{
+  unsigned   a[2];
+  RETSIGTYPE (*old_handler) (int);
+  double     cycletime;
+
+  /* suppress a warning about a[] unused */
+  a[0] = 0;
+
+  if (! have_mftb)
+    return 0;
+
+#ifdef SIGILL
+  old_handler = signal (SIGILL, mftb_works_handler);
+  if (old_handler == SIG_ERR)
+    {
+      if (speed_option_verbose)
+	printf ("mftb_works_p(): SIGILL not supported, assuming mftb works\n");
+      return 1;
+    }
+  if (setjmp (mftb_works_buf))
+    {
+      if (speed_option_verbose)
+	printf ("mftb_works_p(): SIGILL during mftb, so doesn't work\n");
+      return 0;
+    }
+  MFTB (a);
+  signal (SIGILL, old_handler);
+  if (speed_option_verbose)
+    printf ("mftb_works_p(): mftb works\n");
+#else
+
+  if (speed_option_verbose)
+    printf ("mftb_works_p(): SIGILL not defined, assuming mftb works\n");
+#endif
+
+#if ! HAVE_GETTIMEOFDAY
+  if (speed_option_verbose)
+    printf ("mftb_works_p(): no gettimeofday available to measure mftb\n");
+  return 0;
+#endif
+
+  /* The time base is normally 1/4 of the bus speed on 6xx and 7xx chips, on
+     other chips it can be driven from an external clock. */
+  cycletime = freq_measure ("mftb", freq_measure_mftb_one);
+  if (cycletime == -1.0)
+    {
+      if (speed_option_verbose)
+	printf ("mftb_works_p(): cannot measure mftb period\n");
+      return 0;
+    }
+
+  mftb_unittime = cycletime;
+  return 1;
+}
+
+
+volatile unsigned  *sgi_addr;
+
+int
+sgi_works_p (void)
+{
+#if HAVE_SYSSGI && HAVE_MMAP
+  static int  result = -1;
+
+  size_t          pagesize, offset;
+  __psunsigned_t  phys, physpage;
+  void            *virtpage;
+  unsigned        period_picoseconds;
+  int             size, fd;
+
+  if (result != -1)
+    return result;
+
+  phys = syssgi (SGI_QUERY_CYCLECNTR, &period_picoseconds);
+  if (phys == (__psunsigned_t) -1)
+    {
+      /* ENODEV is the error when a counter is not available */
+      if (speed_option_verbose)
+	printf ("syssgi SGI_QUERY_CYCLECNTR error: %s\n", strerror (errno));
+      result = 0;
+      return result;
+    }
+  sgi_unittime = period_picoseconds * 1e-12;
+
+  /* IRIX 5 doesn't have SGI_CYCLECNTR_SIZE, assume 32 bits in that case.
+     Challenge/ONYX hardware has a 64 bit byte counter, but there seems no
+     obvious way to identify that without SGI_CYCLECNTR_SIZE.  */
+#ifdef SGI_CYCLECNTR_SIZE
+  size = syssgi (SGI_CYCLECNTR_SIZE);
+  if (size == -1)
+    {
+      if (speed_option_verbose)
+	{
+	  printf ("syssgi SGI_CYCLECNTR_SIZE error: %s\n", strerror (errno));
+	  printf ("    will assume size==4\n");
+	}
+      size = 32;
+    }
+#else
+  size = 32;
+#endif
+
+  if (size < 32)
+    {
+      printf ("syssgi SGI_CYCLECNTR_SIZE gives %d, expected 32 or 64\n", size);
+      result = 0;
+      return result;
+    }
+
+  pagesize = getpagesize();
+  offset = (size_t) phys & (pagesize-1);
+  physpage = phys - offset;
+
+  /* shouldn't cross over a page boundary */
+  ASSERT_ALWAYS (offset + size/8 <= pagesize);
+
+  fd = open("/dev/mmem", O_RDONLY);
+  if (fd == -1)
+    {
+      if (speed_option_verbose)
+	printf ("open /dev/mmem: %s\n", strerror (errno));
+      result = 0;
+      return result;
+    }
+
+  virtpage = mmap (0, pagesize, PROT_READ, MAP_PRIVATE, fd, (off_t) physpage);
+  if (virtpage == (void *) -1)
+    {
+      if (speed_option_verbose)
+	printf ("mmap /dev/mmem: %s\n", strerror (errno));
+      result = 0;
+      return result;
+    }
+
+  /* address of least significant 4 bytes, knowing mips is big endian */
+  sgi_addr = (unsigned *) ((char *) virtpage + offset
+			   + size/8 - sizeof(unsigned));
+  result = 1;
+  return result;
+
+#else /* ! (HAVE_SYSSGI && HAVE_MMAP) */
+  return 0;
+#endif
+}
+
+
+#define DEFAULT(var,n)  \
+  do {                  \
+    if (! (var))        \
+      (var) = (n);      \
+  } while (0)
+
+void
+speed_time_init (void)
+{
+  double supplement_unittime = 0.0;
+
+  static int  speed_time_initialized = 0;
+  if (speed_time_initialized)
+    return;
+  speed_time_initialized = 1;
+
+  speed_cycletime_init ();
+
+  if (!speed_option_cycles_broken && have_cycles && cycles_works_p ())
+    {
+      use_cycles = 1;
+      DEFAULT (speed_cycletime, 1.0);
+      speed_unittime = speed_cycletime;
+      DEFAULT (speed_precision, 10000);
+      strcpy (speed_time_string, "CPU cycle counter");
+
+      /* only used if a supplementary method is chosen below */
+      cycles_limit = (have_cycles == 1 ? M_2POW32 : M_2POW64) / 2.0
+	* speed_cycletime;
+
+      if (have_grus && getrusage_microseconds_p() && ! getrusage_backwards_p())
+	{
+	  /* this is a good combination */
+	  use_grus = 1;
+	  supplement_unittime = grus_unittime = 1.0e-6;
+	  strcpy (speed_time_string, "CPU cycle counter, supplemented by microsecond getrusage()");
+	}
+      else if (have_cycles == 1)
+	{
+	  /* When speed_cyclecounter has a limited range, look for something
+	     to supplement it. */
+	  if (have_gtod && gettimeofday_microseconds_p())
+	    {
+	      use_gtod = 1;
+	      supplement_unittime = gtod_unittime = 1.0e-6;
+	      strcpy (speed_time_string, "CPU cycle counter, supplemented by microsecond gettimeofday()");
+	    }
+	  else if (have_grus)
+	    {
+	      use_grus = 1;
+	      supplement_unittime = grus_unittime = 1.0 / (double) clk_tck ();
+	      sprintf (speed_time_string, "CPU cycle counter, supplemented by %s clock tick getrusage()", unittime_string (supplement_unittime));
+	    }
+	  else if (have_times)
+	    {
+	      use_times = 1;
+	      supplement_unittime = times_unittime = 1.0 / (double) clk_tck ();
+	      sprintf (speed_time_string, "CPU cycle counter, supplemented by %s clock tick times()", unittime_string (supplement_unittime));
+	    }
+	  else if (have_gtod)
+	    {
+	      use_gtod = 1;
+	      supplement_unittime = gtod_unittime = 1.0 / (double) clk_tck ();
+	      sprintf (speed_time_string, "CPU cycle counter, supplemented by %s clock tick gettimeofday()", unittime_string (supplement_unittime));
+	    }
+	  else
+	    {
+	      fprintf (stderr, "WARNING: cycle counter is 32 bits and there's no other functions.\n");
+	      fprintf (stderr, "    Wraparounds may produce bad results on long measurements.\n");
+	    }
+	}
+
+      if (use_grus || use_times || use_gtod)
+	{
+	  /* must know cycle period to compare cycles to other measuring
+	     (via cycles_limit) */
+	  speed_cycletime_need_seconds ();
+
+	  if (speed_precision * supplement_unittime > cycles_limit)
+	    {
+	      fprintf (stderr, "WARNING: requested precision can't always be achieved due to limited range\n");
+	      fprintf (stderr, "    cycle counter and limited precision supplemental method\n");
+	      fprintf (stderr, "    (%s)\n", speed_time_string);
+	    }
+	}
+    }
+  else if (have_stck)
+    {
+      strcpy (speed_time_string, "STCK timestamp");
+      /* stck is in units of 2^-12 microseconds, which is very likely higher
+	 resolution than a cpu cycle */
+      if (speed_cycletime == 0.0)
+	speed_cycletime_fail
+	  ("Need to know CPU frequency for effective stck unit");
+      speed_unittime = MAX (speed_cycletime, STCK_PERIOD);
+      DEFAULT (speed_precision, 10000);
+    }
+  else if (have_mftb && mftb_works_p ())
+    {
+      use_mftb = 1;
+      DEFAULT (speed_precision, 10000);
+      speed_unittime = mftb_unittime;
+      sprintf (speed_time_string, "mftb counter (%s)",
+	       unittime_string (speed_unittime));
+    }
+  else if (have_sgi && sgi_works_p ())
+    {
+      use_sgi = 1;
+      DEFAULT (speed_precision, 10000);
+      speed_unittime = sgi_unittime;
+      sprintf (speed_time_string, "syssgi() mmap counter (%s), supplemented by millisecond getrusage()",
+	       unittime_string (speed_unittime));
+      /* supplemented with getrusage, which we assume to have 1ms resolution */
+      use_grus = 1;
+      supplement_unittime = 1e-3;
+    }
+  else if (have_rrt)
+    {
+      timebasestruct_t  t;
+      use_rrt = 1;
+      DEFAULT (speed_precision, 10000);
+      read_real_time (&t, sizeof(t));
+      switch (t.flag) {
+      case RTC_POWER:
+	/* FIXME: What's the actual RTC resolution? */
+	speed_unittime = 1e-7;
+	strcpy (speed_time_string, "read_real_time() power nanoseconds");
+	break;
+      case RTC_POWER_PC:
+	t.tb_high = 1;
+	t.tb_low = 0;
+	time_base_to_time (&t, sizeof(t));
+	speed_unittime = TIMEBASESTRUCT_SECS(&t) / M_2POW32;
+	sprintf (speed_time_string, "%s read_real_time() powerpc ticks",
+		 unittime_string (speed_unittime));
+	break;
+      default:
+	fprintf (stderr, "ERROR: Unrecognised timebasestruct_t flag=%d\n",
+		 t.flag);
+	abort ();
+      }
+    }
+  else if (have_cgt && cgt_works_p() && cgt_unittime < 1.5e-6)
+    {
+      /* use clock_gettime if microsecond or better resolution */
+    choose_cgt:
+      use_cgt = 1;
+      speed_unittime = cgt_unittime;
+      DEFAULT (speed_precision, (cgt_unittime <= 0.1e-6 ? 10000 : 1000));
+      strcpy (speed_time_string, "microsecond accurate clock_gettime()");
+    }
+  else if (have_times && clk_tck() > 1000000)
+    {
+      /* Cray vector systems have times() which is clock cycle resolution
+	 (eg. 450 MHz).  */
+      DEFAULT (speed_precision, 10000);
+      goto choose_times;
+    }
+  else if (have_grus && getrusage_microseconds_p() && ! getrusage_backwards_p())
+    {
+      use_grus = 1;
+      speed_unittime = grus_unittime = 1.0e-6;
+      DEFAULT (speed_precision, 1000);
+      strcpy (speed_time_string, "microsecond accurate getrusage()");
+    }
+  else if (have_gtod && gettimeofday_microseconds_p())
+    {
+      use_gtod = 1;
+      speed_unittime = gtod_unittime = 1.0e-6;
+      DEFAULT (speed_precision, 1000);
+      strcpy (speed_time_string, "microsecond accurate gettimeofday()");
+    }
+  else if (have_cgt && cgt_works_p() && cgt_unittime < 1.5/clk_tck())
+    {
+      /* use clock_gettime if 1 tick or better resolution */
+      goto choose_cgt;
+    }
+  else if (have_times)
+    {
+      use_tick_boundary = 1;
+      DEFAULT (speed_precision, 200);
+    choose_times:
+      use_times = 1;
+      speed_unittime = times_unittime = 1.0 / (double) clk_tck ();
+      sprintf (speed_time_string, "%s clock tick times()",
+	       unittime_string (speed_unittime));
+    }
+  else if (have_grus)
+    {
+      use_grus = 1;
+      use_tick_boundary = 1;
+      speed_unittime = grus_unittime = 1.0 / (double) clk_tck ();
+      DEFAULT (speed_precision, 200);
+      sprintf (speed_time_string, "%s clock tick getrusage()\n",
+	       unittime_string (speed_unittime));
+    }
+  else if (have_gtod)
+    {
+      use_gtod = 1;
+      use_tick_boundary = 1;
+      speed_unittime = gtod_unittime = 1.0 / (double) clk_tck ();
+      DEFAULT (speed_precision, 200);
+      sprintf (speed_time_string, "%s clock tick gettimeofday()",
+	       unittime_string (speed_unittime));
+    }
+  else
+    {
+      fprintf (stderr, "No time measuring method available\n");
+      fprintf (stderr, "None of: speed_cyclecounter(), STCK(), getrusage(), gettimeofday(), times()\n");
+      abort ();
+    }
+
+  if (speed_option_verbose)
+    {
+      printf ("speed_time_init: %s\n", speed_time_string);
+      printf ("    speed_precision     %d\n", speed_precision);
+      printf ("    speed_unittime      %.2g\n", speed_unittime);
+      if (supplement_unittime)
+	printf ("    supplement_unittime %.2g\n", supplement_unittime);
+      printf ("    use_tick_boundary   %d\n", use_tick_boundary);
+      if (have_cycles)
+	printf ("    cycles_limit        %.2g seconds\n", cycles_limit);
+    }
+}
+
+
+
+/* Burn up CPU until a clock tick boundary, for greater accuracy.  Set the
+   corresponding "start_foo" appropriately too. */
+
+void
+grus_tick_boundary (void)
+{
+  struct_rusage  prev;
+  getrusage (0, &prev);
+  do {
+    getrusage (0, &start_grus);
+  } while (start_grus.ru_utime.tv_usec == prev.ru_utime.tv_usec);
+}
+
+void
+gtod_tick_boundary (void)
+{
+  struct_timeval  prev;
+  gettimeofday (&prev, NULL);
+  do {
+    gettimeofday (&start_gtod, NULL);
+  } while (start_gtod.tv_usec == prev.tv_usec);
+}
+
+void
+times_tick_boundary (void)
+{
+  struct_tms  prev;
+  times (&prev);
+  do
+    times (&start_times);
+  while (start_times.tms_utime == prev.tms_utime);
+}
+
+
+/* "have_" values are tested to let unused code go dead.  */
+
+void
+speed_starttime (void)
+{
+  speed_time_init ();
+
+  if (have_grus && use_grus)
+    {
+      if (use_tick_boundary)
+	grus_tick_boundary ();
+      else
+	getrusage (0, &start_grus);
+    }
+
+  if (have_gtod && use_gtod)
+    {
+      if (use_tick_boundary)
+	gtod_tick_boundary ();
+      else
+	gettimeofday (&start_gtod, NULL);
+    }
+
+  if (have_times && use_times)
+    {
+      if (use_tick_boundary)
+	times_tick_boundary ();
+      else
+	times (&start_times);
+    }
+
+  if (have_cgt && use_cgt)
+    clock_gettime (CGT_ID, &start_cgt);
+
+  if (have_rrt && use_rrt)
+    read_real_time (&start_rrt, sizeof(start_rrt));
+
+  if (have_sgi && use_sgi)
+    start_sgi = *sgi_addr;
+
+  if (have_mftb && use_mftb)
+    MFTB (start_mftb);
+
+  if (have_stck && use_stck)
+    STCK (start_stck);
+
+  /* Cycles sampled last for maximum accuracy. */
+  if (have_cycles && use_cycles)
+    speed_cyclecounter (start_cycles);
+}
+
+
+/* Calculate the difference between two cycle counter samples, as a "double"
+   counter of cycles.
+
+   The start and end values are allowed to cancel in integers in case the
+   counter values are bigger than the 53 bits that normally fit in a double.
+
+   This works even if speed_cyclecounter() puts a value bigger than 32-bits
+   in the low word (the high word always gets a 2**32 multiplier though). */
+
+double
+speed_cyclecounter_diff (const unsigned end[2], const unsigned start[2])
+{
+  unsigned  d;
+  double    t;
+
+  if (have_cycles == 1)
+    {
+      t = (end[0] - start[0]);
+    }
+  else
+    {
+      d = end[0] - start[0];
+      t = d - (d > end[0] ? M_2POWU : 0.0);
+      t += (end[1] - start[1]) * M_2POW32;
+    }
+  return t;
+}
+
+
+double
+speed_mftb_diff (const unsigned end[2], const unsigned start[2])
+{
+  unsigned  d;
+  double    t;
+
+  d = end[0] - start[0];
+  t = (double) d - (d > end[0] ? M_2POW32 : 0.0);
+  t += (end[1] - start[1]) * M_2POW32;
+  return t;
+}
+
+
+/* Calculate the difference between "start" and "end" using fields "sec" and
+   "psec", where each "psec" is a "punit" of a second.
+
+   The seconds parts are allowed to cancel before being combined with the
+   psec parts, in case a simple "sec+psec*punit" exceeds the precision of a
+   double.
+
+   Total time is only calculated in a "double" since an integer count of
+   psecs might overflow.  2^32 microseconds is only a bit over an hour, or
+   2^32 nanoseconds only about 4 seconds.
+
+   The casts to "long" are for the benefit of timebasestruct_t, where the
+   fields are only "unsigned int", but we want a signed difference.  */
+
+#define DIFF_SECS_ROUTINE(sec, psec, punit)                     \
+  {                                                             \
+    long  sec_diff, psec_diff;                                  \
+    sec_diff = (long) end->sec - (long) start->sec;             \
+    psec_diff = (long) end->psec - (long) start->psec;          \
+    return (double) sec_diff + punit * (double) psec_diff;      \
+  }
+
+double
+timeval_diff_secs (const struct_timeval *end, const struct_timeval *start)
+{
+  DIFF_SECS_ROUTINE (tv_sec, tv_usec, 1e-6);
+}
+
+double
+rusage_diff_secs (const struct_rusage *end, const struct_rusage *start)
+{
+  DIFF_SECS_ROUTINE (ru_utime.tv_sec, ru_utime.tv_usec, 1e-6);
+}
+
+double
+timespec_diff_secs (const struct_timespec *end, const struct_timespec *start)
+{
+  DIFF_SECS_ROUTINE (tv_sec, tv_nsec, 1e-9);
+}
+
+/* This is for use after time_base_to_time, ie. for seconds and nanoseconds. */
+double
+timebasestruct_diff_secs (const timebasestruct_t *end,
+			  const timebasestruct_t *start)
+{
+  DIFF_SECS_ROUTINE (tb_high, tb_low, 1e-9);
+}
+
+
+double
+speed_endtime (void)
+{
+#define END_USE(name,value)                             \
+  do {                                                  \
+    if (speed_option_verbose >= 3)                      \
+      printf ("speed_endtime(): used %s\n", name);      \
+    result = value;                                     \
+    goto done;                                          \
+  } while (0)
+
+#define END_ENOUGH(name,value)                                          \
+  do {                                                                  \
+    if (speed_option_verbose >= 3)                                      \
+      printf ("speed_endtime(): %s gives enough precision\n", name);    \
+    result = value;                                                     \
+    goto done;                                                          \
+  } while (0)
+
+#define END_EXCEED(name,value)                                            \
+  do {                                                                    \
+    if (speed_option_verbose >= 3)                                        \
+      printf ("speed_endtime(): cycle counter limit exceeded, used %s\n", \
+	      name);                                                      \
+    result = value;                                                       \
+    goto done;                                                            \
+  } while (0)
+
+  unsigned          end_cycles[2];
+  stck_t            end_stck;
+  unsigned          end_mftb[2];
+  unsigned          end_sgi;
+  timebasestruct_t  end_rrt;
+  struct_timespec   end_cgt;
+  struct_timeval    end_gtod;
+  struct_rusage     end_grus;
+  struct_tms        end_times;
+  double            t_gtod, t_grus, t_times, t_cgt;
+  double            t_rrt, t_sgi, t_mftb, t_stck, t_cycles;
+  double            result;
+
+  /* Cycles sampled first for maximum accuracy.
+     "have_" values tested to let unused code go dead.  */
+
+  if (have_cycles && use_cycles)  speed_cyclecounter (end_cycles);
+  if (have_stck   && use_stck)    STCK (end_stck);
+  if (have_mftb   && use_mftb)    MFTB (end_mftb);
+  if (have_sgi    && use_sgi)     end_sgi = *sgi_addr;
+  if (have_rrt    && use_rrt)     read_real_time (&end_rrt, sizeof(end_rrt));
+  if (have_cgt    && use_cgt)     clock_gettime (CGT_ID, &end_cgt);
+  if (have_gtod   && use_gtod)    gettimeofday (&end_gtod, NULL);
+  if (have_grus   && use_grus)    getrusage (0, &end_grus);
+  if (have_times  && use_times)   times (&end_times);
+
+  result = -1.0;
+
+  if (speed_option_verbose >= 4)
+    {
+      printf ("speed_endtime():\n");
+      if (use_cycles)
+	printf ("   cycles  0x%X,0x%X -> 0x%X,0x%X\n",
+		start_cycles[1], start_cycles[0],
+		end_cycles[1], end_cycles[0]);
+
+      if (use_stck)
+	printf ("   stck  0x%lX -> 0x%lX\n", start_stck, end_stck);
+
+      if (use_mftb)
+	printf ("   mftb  0x%X,%08X -> 0x%X,%08X\n",
+		start_mftb[1], start_mftb[0],
+		end_mftb[1], end_mftb[0]);
+
+      if (use_sgi)
+	printf ("   sgi  0x%X -> 0x%X\n", start_sgi, end_sgi);
+
+      if (use_rrt)
+	printf ("   read_real_time  (%d)%u,%u -> (%d)%u,%u\n",
+		start_rrt.flag, start_rrt.tb_high, start_rrt.tb_low,
+		end_rrt.flag, end_rrt.tb_high, end_rrt.tb_low);
+
+      if (use_cgt)
+	printf ("   clock_gettime  %ld.%09ld -> %ld.%09ld\n",
+		(long) start_cgt.tv_sec, (long) start_cgt.tv_nsec,
+		(long) end_cgt.tv_sec, (long) end_cgt.tv_nsec);
+
+      if (use_gtod)
+	printf ("   gettimeofday  %ld.%06ld -> %ld.%06ld\n",
+		(long) start_gtod.tv_sec, (long) start_gtod.tv_usec,
+		(long) end_gtod.tv_sec, (long) end_gtod.tv_usec);
+
+      if (use_grus)
+	printf ("   getrusage  %ld.%06ld -> %ld.%06ld\n",
+		(long) start_grus.ru_utime.tv_sec,
+		(long) start_grus.ru_utime.tv_usec,
+		(long) end_grus.ru_utime.tv_sec,
+		(long) end_grus.ru_utime.tv_usec);
+
+      if (use_times)
+	printf ("   times  %ld -> %ld\n",
+		start_times.tms_utime, end_times.tms_utime);
+    }
+
+  if (use_rrt)
+    {
+      time_base_to_time (&start_rrt, sizeof(start_rrt));
+      time_base_to_time (&end_rrt, sizeof(end_rrt));
+      t_rrt = timebasestruct_diff_secs (&end_rrt, &start_rrt);
+      END_USE ("read_real_time()", t_rrt);
+    }
+
+  if (use_cgt)
+    {
+      t_cgt = timespec_diff_secs (&end_cgt, &start_cgt);
+      END_USE ("clock_gettime()", t_cgt);
+    }
+
+  if (use_grus)
+    {
+      t_grus = rusage_diff_secs (&end_grus, &start_grus);
+
+      /* Use getrusage() if the cycle counter limit would be exceeded, or if
+	 it provides enough accuracy already. */
+      if (use_cycles)
+	{
+	  if (t_grus >= speed_precision*grus_unittime)
+	    END_ENOUGH ("getrusage()", t_grus);
+	  if (t_grus >= cycles_limit)
+	    END_EXCEED ("getrusage()", t_grus);
+	}
+    }
+
+  if (use_times)
+    {
+      t_times = (end_times.tms_utime - start_times.tms_utime) * times_unittime;
+
+      /* Use times() if the cycle counter limit would be exceeded, or if
+	 it provides enough accuracy already. */
+      if (use_cycles)
+	{
+	  if (t_times >= speed_precision*times_unittime)
+	    END_ENOUGH ("times()", t_times);
+	  if (t_times >= cycles_limit)
+	    END_EXCEED ("times()", t_times);
+	}
+    }
+
+  if (use_gtod)
+    {
+      t_gtod = timeval_diff_secs (&end_gtod, &start_gtod);
+
+      /* Use gettimeofday() if it measured a value bigger than the cycle
+	 counter can handle.  */
+      if (use_cycles)
+	{
+	  if (t_gtod >= cycles_limit)
+	    END_EXCEED ("gettimeofday()", t_gtod);
+	}
+    }
+
+  if (use_mftb)
+    {
+      t_mftb = speed_mftb_diff (end_mftb, start_mftb) * mftb_unittime;
+      END_USE ("mftb", t_mftb);
+    }
+
+  if (use_stck)
+    {
+      t_stck = (end_stck - start_stck) * STCK_PERIOD;
+      END_USE ("stck", t_stck);
+    }
+
+  if (use_sgi)
+    {
+      t_sgi = (end_sgi - start_sgi) * sgi_unittime;
+      END_USE ("SGI hardware counter", t_sgi);
+    }
+
+  if (use_cycles)
+    {
+      t_cycles = speed_cyclecounter_diff (end_cycles, start_cycles)
+	* speed_cycletime;
+      END_USE ("cycle counter", t_cycles);
+    }
+
+  if (use_grus && getrusage_microseconds_p())
+    END_USE ("getrusage()", t_grus);
+
+  if (use_gtod && gettimeofday_microseconds_p())
+    END_USE ("gettimeofday()", t_gtod);
+
+  if (use_times)  END_USE ("times()",        t_times);
+  if (use_grus)   END_USE ("getrusage()",    t_grus);
+  if (use_gtod)   END_USE ("gettimeofday()", t_gtod);
+
+  fprintf (stderr, "speed_endtime(): oops, no time method available\n");
+  abort ();
+
+ done:
+  if (result < 0.0)
+    {
+      if (speed_option_verbose >= 2)
+	fprintf (stderr, "speed_endtime(): warning, treating negative time as zero: %.9f\n", result);
+      result = 0.0;
+    }
+  return result;
+}