Commit 6bd09257 authored by Paul Eggert's avatar Paul Eggert
Browse files

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.
parent 6ad341ee
2019-12-23 Paul Eggert <eggert@cs.ucla.edu>
 
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
......@@ -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
#
......
......@@ -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);
......
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