On 12/23/19 12:38 AM, Bruno Haible wrote:
> => I'm in favour of installing your new formula.
Sure, I installed the attached. The first patch is for xtime.h, the remaining
patches are for other instances of this idiom in Gnulib.
>From 6ad341ee4a0cca1a8b1744bc269282aafd765868 Mon Sep 17 00:00:00 2001
From: Paul Eggert <egg...@cs.ucla.edu>
Date: Mon, 23 Dec 2019 19:04:50 -0800
Subject: [PATCH 1/4] gethrxtime: improve xtime_sec performance
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Performanced analyzed by Bruno Haible in:
https://lists.gnu.org/r/bug-gnulib/2019-12/msg00200.html
* lib/xtime.h (xtime_sec): Redo with neither ‘%’ nor conditional
branches.
---
ChangeLog | 8 ++++++++
lib/xtime.h | 2 +-
2 files changed, 9 insertions(+), 1 deletion(-)
diff --git a/ChangeLog b/ChangeLog
index e0ecf87b7..f6a705a7a 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,11 @@
+2019-12-23 Paul Eggert <egg...@cs.ucla.edu>
+
+ gethrxtime: improve xtime_sec performance
+ Performanced analyzed by Bruno Haible in:
+ https://lists.gnu.org/r/bug-gnulib/2019-12/msg00200.html
+ * lib/xtime.h (xtime_sec): Redo with neither ‘%’ nor conditional
+ branches.
+
2019-12-23 Bruno Haible <br...@clisp.org>
setlocale-null: Export the lock function also on non-Windows platforms.
diff --git a/lib/xtime.h b/lib/xtime.h
index 5dea46767..25185d01b 100644
--- a/lib/xtime.h
+++ b/lib/xtime.h
@@ -61,7 +61,7 @@ xtime_nonnegative_sec (xtime_t t)
XTIME_INLINE xtime_t
xtime_sec (xtime_t t)
{
- return t / XTIME_PRECISION - (t % XTIME_PRECISION < 0);
+ return (t + (t < 0)) / XTIME_PRECISION - (t < 0);
}
/* Return the number of nanoseconds in T, which must be nonnegative. */
--
2.17.1
>From f29bc5f35e5871452270c742f1784d9422f95c62 Mon Sep 17 00:00:00 2001
From: Paul Eggert <egg...@cs.ucla.edu>
Date: Mon, 23 Dec 2019 23:47:37 -0800
Subject: [PATCH 2/4] mktime: tweak division performance
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* config/srclist.txt: Do not sync mktime.c for now.
* lib/mktime.c (shr, ydhms_diff):
Redo with neither ‘%’ nor conditional branches.
---
ChangeLog | 5 +++++
config/srclist.txt | 2 +-
lib/mktime.c | 6 +++---
3 files changed, 9 insertions(+), 4 deletions(-)
diff --git a/ChangeLog b/ChangeLog
index f6a705a7a..1f7eb19b9 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,10 @@
2019-12-23 Paul Eggert <egg...@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
diff --git a/config/srclist.txt b/config/srclist.txt
index 55d574ab3..9a7b9597d 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 11b0d5353..81c9ca1fc 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);
--
2.17.1
>From 3c8e21069a9e66b7e845a3f39d22d429c263ff0c Mon Sep 17 00:00:00 2001
From: Paul Eggert <egg...@cs.ucla.edu>
Date: Mon, 23 Dec 2019 23:48:35 -0800
Subject: [PATCH 3/4] nstrftime: tweak division performance
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* lib/nstrftime.c (SHR, tm_diff, __strftime_internal):
Redo with neither ‘%’ nor conditional branches.
---
ChangeLog | 4 ++++
lib/nstrftime.c | 14 ++++++++------
2 files changed, 12 insertions(+), 6 deletions(-)
diff --git a/ChangeLog b/ChangeLog
index 1f7eb19b9..4b4714204 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,9 @@
2019-12-23 Paul Eggert <egg...@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):
diff --git a/lib/nstrftime.c b/lib/nstrftime.c
index 23b0a6460..62bc7a61e 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'):
--
2.17.1
>From 6f9ead5181f2c117b3c5a4c965fe44dc1258661b Mon Sep 17 00:00:00 2001
From: Paul Eggert <egg...@cs.ucla.edu>
Date: Mon, 23 Dec 2019 23:53:23 -0800
Subject: [PATCH 4/4] strptime: tweak division performance
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* lib/strptime.c (day_of_the_week):
Redo with neither ‘%’ nor conditional branches.
---
ChangeLog | 17 ++++++-----------
lib/strptime.c | 7 ++++---
2 files changed, 10 insertions(+), 14 deletions(-)
diff --git a/ChangeLog b/ChangeLog
index 4b4714204..168037ed1 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,20 +1,15 @@
2019-12-23 Paul Eggert <egg...@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
+ gethrxtime, mktime, nstrftime, strptime: tweak division performance
+ Performanced analyzed by Bruno Haible in:
+ https://lists.gnu.org/r/bug-gnulib/2019-12/msg00200.html
* config/srclist.txt: Do not sync mktime.c for now.
* lib/mktime.c (shr, ydhms_diff):
+ * lib/nstrftime.c (SHR, tm_diff, __strftime_internal):
+ * lib/strptime.c (day_of_the_week):
+ * lib/xtime.h (xtime_sec):
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
- * lib/xtime.h (xtime_sec): Redo with neither ‘%’ nor conditional
- branches.
-
2019-12-23 Bruno Haible <br...@clisp.org>
setlocale-null: Export the lock function also on non-Windows platforms.
diff --git a/lib/strptime.c b/lib/strptime.c
index e6d405a44..9c2c2e38b 100644
--- a/lib/strptime.c
+++ b/lib/strptime.c
@@ -202,11 +202,12 @@ day_of_the_week (struct tm *tm)
difference between this data in the one on TM and so determine
the weekday. */
int corr_year = 1900 + tm->tm_year - (tm->tm_mon < 2);
+ int corr_quad = corr_year / 4;
int wday = (-473
+ (365 * (tm->tm_year - 70))
- + (corr_year / 4)
- - ((corr_year / 4) / 25) + ((corr_year / 4) % 25 < 0)
- + (((corr_year / 4) / 25) / 4)
+ + corr_quad
+ - (corr_quad + (corr_quad < 0)) / 25 - (corr_quad < 0)
+ + ((corr_quad / 25) / 4)
+ __mon_yday[0][tm->tm_mon]
+ tm->tm_mday - 1);
tm->tm_wday = ((wday % 7) + 7) % 7;
--
2.17.1
