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Retrieving sys/user time in timevars is quite expensive because it always needs a system call. Only getting the wall time is much cheaper because operating systems have optimized paths for this. The sys time isn't that interesting for a compiler and wall time is usually close to user time except when the system is overloaded. On the other hand when it is not wall time is more accurate because it has less overhead. For building tramp3d with -O0 the -ftime-report overhead drops from 18% to 3%. For -O2 it drops from 8% to not measurable. I changed the code to use gettimeofday as a fallback for clock_gettime CLOCK_MONOTONIC. If a host has neither of those the time will not be measured. Previously clock was the fallback. This removes a lot of code in timevar.cc: gcc/timevar.cc | 167 ++++++--------------------------------------------------- gcc/timevar.h | 10 +--- 2 files changed, 17 insertions(+), 160 deletions(-) gcc/ChangeLog: * timevar.cc (struct tms): Remove. (RUSAGE_SELF): Remove. (TICKS_PER_SECOND): Remove. (USE_TIMES): Remove. (HAVE_USER_TIME): Remove. (HAVE_SYS_TIME): Remove. (HAVE_WALL_TIME): Remove. (USE_GETRUSAGE): Remove. (USE_CLOCK): Remove. (NANOSEC_PER_SEC): Remove. (TICKS_TO_NANOSEC): Remove. (CLOCKS_TO_NANOSEC): Remove. (timer::named_items::push): Remove sys/user. (get_time): Remove clock and times and getruage code. (timevar_accumulate): Remove sys/user. (timevar_diff): Dito. (timer::validate_phases): Dito. (timer::print_row): Dito. (timer::all_zero): Dito. (timer::print): Dito. (make_json_for_timevar_time_def): Dito. * timevar.h (struct timevar_time_def): Dito.
This directory contains the GNU Compiler Collection (GCC). The GNU Compiler Collection is free software. See the files whose names start with COPYING for copying permission. The manuals, and some of the runtime libraries, are under different terms; see the individual source files for details. The directory INSTALL contains copies of the installation information as HTML and plain text. The source of this information is gcc/doc/install.texi. The installation information includes details of what is included in the GCC sources and what files GCC installs. See the file gcc/doc/gcc.texi (together with other files that it includes) for usage and porting information. An online readable version of the manual is in the files gcc/doc/gcc.info*. See http://gcc.gnu.org/bugs/ for how to report bugs usefully. Copyright years on GCC source files may be listed using range notation, e.g., 1987-2012, indicating that every year in the range, inclusive, is a copyrightable year that could otherwise be listed individually.