Commit 99e080c2 authored by Paul Eggert's avatar Paul Eggert
Browse files

nstrftime: tweak division performance

* lib/nstrftime.c (SHR, tm_diff, __strftime_internal):
Redo with neither ‘%’ nor conditional branches.
parent 6bd09257
2019-12-23 Paul Eggert <eggert@cs.ucla.edu>
 
nstrftime: tweak division performance
* lib/nstrftime.c (SHR, tm_diff, __strftime_internal):
Redo with neither ‘%’ nor conditional branches.
mktime: tweak division performance
* config/srclist.txt: Do not sync mktime.c for now.
* lib/mktime.c (shr, ydhms_diff):
......@@ -113,7 +113,7 @@ extern char *tzname[];
#define SHR(a, b) \
(-1 >> 1 == -1 \
? (a) >> (b) \
: (a) / (1 << (b)) - ((a) % (1 << (b)) < 0))
: ((a) + ((a) < 0)) / (1 << (b)) - ((a) < 0))
#define TM_YEAR_BASE 1900
......@@ -348,8 +348,8 @@ tm_diff (const struct tm *a, const struct tm *b)
but it's OK to assume that A and B are close to each other. */
int a4 = SHR (a->tm_year, 2) + SHR (TM_YEAR_BASE, 2) - ! (a->tm_year & 3);
int b4 = SHR (b->tm_year, 2) + SHR (TM_YEAR_BASE, 2) - ! (b->tm_year & 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);
......@@ -927,9 +927,11 @@ __strftime_internal (STREAM_OR_CHAR_T *s, STRFTIME_ARG (size_t maxsize)
}
{
int century = tp->tm_year / 100 + TM_YEAR_BASE / 100;
century -= tp->tm_year % 100 < 0 && 0 < century;
DO_YEARISH (2, tp->tm_year < - TM_YEAR_BASE, century);
bool negative_year = tp->tm_year < - TM_YEAR_BASE;
bool zero_thru_1899 = !negative_year & (tp->tm_year < 0);
int century = ((tp->tm_year - 99 * zero_thru_1899) / 100
+ TM_YEAR_BASE / 100);
DO_YEARISH (2, negative_year, century);
}
case L_('x'):
......
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