From: Paul Eggert Date: Tue, 24 Dec 2019 07:48:35 +0000 (-0800) Subject: nstrftime: tweak division performance X-Git-Tag: v1.0~4428 X-Git-Url: https://gitweb.git.savannah.gnu.org/gitweb/?a=commitdiff_plain;h=99e080c2f4dc243ef6f7d845e35295f62393cd52;p=gnulib.git nstrftime: tweak division performance * lib/nstrftime.c (SHR, tm_diff, __strftime_internal): Redo with neither ‘%’ nor conditional branches. --- diff --git a/ChangeLog b/ChangeLog index 1f7eb19b9e..4b47142040 100644 --- a/ChangeLog +++ b/ChangeLog @@ -1,5 +1,9 @@ 2019-12-23 Paul Eggert + 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): diff --git a/lib/nstrftime.c b/lib/nstrftime.c index 23b0a64608..62bc7a61e3 100644 --- a/lib/nstrftime.c +++ b/lib/nstrftime.c @@ -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'):