From: Paul Eggert Date: Tue, 24 Dec 2019 07:47:37 +0000 (-0800) Subject: mktime: tweak division performance X-Git-Tag: v1.0~4429 X-Git-Url: https://gitweb.git.savannah.gnu.org/gitweb/?a=commitdiff_plain;h=6bd09257a491e635aa7e42d15935747818e492f2;p=gnulib.git mktime: tweak division performance * config/srclist.txt: Do not sync mktime.c for now. * lib/mktime.c (shr, ydhms_diff): Redo with neither ‘%’ nor conditional branches. --- diff --git a/ChangeLog b/ChangeLog index f6a705a7a2..1f7eb19b9e 100644 --- a/ChangeLog +++ b/ChangeLog @@ -1,5 +1,10 @@ 2019-12-23 Paul Eggert + mktime: tweak division performance + * config/srclist.txt: Do not sync mktime.c for now. + * lib/mktime.c (shr, ydhms_diff): + Redo with neither ‘%’ nor conditional branches. + gethrxtime: improve xtime_sec performance Performanced analyzed by Bruno Haible in: https://lists.gnu.org/r/bug-gnulib/2019-12/msg00200.html diff --git a/config/srclist.txt b/config/srclist.txt index 55d574ab31..9a7b9597d4 100644 --- a/config/srclist.txt +++ b/config/srclist.txt @@ -59,7 +59,7 @@ $LIBCSRC posix/regex_internal.c lib $LIBCSRC posix/regex_internal.h lib $LIBCSRC posix/regexec.c lib $LIBCSRC time/timegm.c lib -$LIBCSRC time/mktime.c lib +#$LIBCSRC time/mktime.c lib $LIBCSRC time/mktime-internal.h lib # diff --git a/lib/mktime.c b/lib/mktime.c index 11b0d5353b..81c9ca1fcb 100644 --- a/lib/mktime.c +++ b/lib/mktime.c @@ -141,7 +141,7 @@ shr (long_int a, int b) long_int one = 1; return (-one >> 1 == -1 ? a >> b - : a / (one << b) - (a % (one << b) < 0)); + : (a + (a < 0)) / (one << b) - (a < 0)); } /* Bounds for the intersection of __time64_t and long_int. */ @@ -211,8 +211,8 @@ ydhms_diff (long_int year1, long_int yday1, int hour1, int min1, int sec1, Take care to avoid integer overflow here. */ int a4 = shr (year1, 2) + shr (TM_YEAR_BASE, 2) - ! (year1 & 3); int b4 = shr (year0, 2) + shr (TM_YEAR_BASE, 2) - ! (year0 & 3); - int a100 = a4 / 25 - (a4 % 25 < 0); - int b100 = b4 / 25 - (b4 % 25 < 0); + int a100 = (a4 + (a4 < 0)) / 25 - (a4 < 0); + int b100 = (b4 + (b4 < 0)) / 25 - (b4 < 0); int a400 = shr (a100, 2); int b400 = shr (b100, 2); int intervening_leap_days = (a4 - b4) - (a100 - b100) + (a400 - b400);