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Convert _time_t_to_tm to asm

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46 bytes size gain, -8% cycles on the unit tests
This commit is contained in:
Colin Leroy-Mira 2024-01-09 21:28:37 +01:00
parent 8aa59e4af3
commit 348a9048b7
3 changed files with 135 additions and 67 deletions
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64
libsrc/common/_time_t_to_tm.c
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@ -1,64 +0,0 @@
/*****************************************************************************/
/* */
/* gmtime.c */
/* */
/* Convert calendar time into broken down time in UTC */
/* */
/* */
/* */
/* (C) 2002 Ullrich von Bassewitz */
/* Wacholderweg 14 */
/* D-70597 Stuttgart */
/* EMail: uz@musoftware.de */
/* */
/* */
/* This software is provided 'as-is', without any expressed or implied */
/* warranty. In no event will the authors be held liable for any damages */
/* arising from the use of this software. */
/* */
/* Permission is granted to anyone to use this software for any purpose, */
/* including commercial applications, and to alter it and redistribute it */
/* freely, subject to the following restrictions: */
/* */
/* 1. The origin of this software must not be misrepresented; you must not */
/* claim that you wrote the original software. If you use this software */
/* in a product, an acknowledgment in the product documentation would be */
/* appreciated but is not required. */
/* 2. Altered source versions must be plainly marked as such, and must not */
/* be misrepresented as being the original software. */
/* 3. This notice may not be removed or altered from any source */
/* distribution. */
/* */
/*****************************************************************************/
#include <time.h>
/*****************************************************************************/
/* Code */
/*****************************************************************************/
struct tm* __fastcall__ _time_t_to_tm (const time_t t)
{
static struct tm timebuf;
/* Since our ints are just 16 bits, split the given time into seconds,
** hours and days. Each of the values will fit in a 16 bit variable.
** The mktime routine will then do the rest.
*/
timebuf.tm_sec = t % 3600;
timebuf.tm_min = 0;
timebuf.tm_hour = (t / 3600) % 24;
timebuf.tm_mday = (t / (3600UL * 24UL)) + 1;
timebuf.tm_mon = 0;
timebuf.tm_year = 70; /* Base value is 1/1/1970 */
/* Call mktime to do the final conversion */
mktime (&timebuf);
/* Return the result */
return &timebuf;
}

129
libsrc/common/_time_t_to_tm.s Normal file
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@ -0,0 +1,129 @@
;
; Colin Leroy-Mira, 2024
;
; struct tm* __fastcall__ _time_t_to_tm (const time_t t)
;
; Helper to gmtime and localtime. Breaks down a number of
; seconds since Jan 1, 1970 into days, hours and seconds,
; so that each of them fits in 16 bits; passes the
; result to _mktime which fixes all values in the struct,
; and returns a pointer to the struct to callers.
;
.export __time_t_to_tm
.import udiv32, _mktime
.importzp sreg, tmp3, ptr1, ptr2, ptr3, ptr4
.include "time.inc"
.macpack cpu
__time_t_to_tm:
; Divide number of seconds since epoch, in ptr1:sreg,
; by 86400 to get the number of days since epoch, and
; the number of seconds today in the remainder.
; Load t as dividend (sreg is already set by the caller)
sta ptr1
stx ptr1+1
; Load 86400 as divisor
lda #$80
sta ptr3
lda #$51
sta ptr3+1
lda #$01
sta ptr4
lda #$00
sta ptr4+1
; Clear TM buf while we have zero in A
ldx #.sizeof(tm)-1
: sta TM,x
dex
bne :-
; Divide t/86400
jsr udiv32
; Store the quotient (the number of full days), and increment
; by one as epoch starts at day 1.
clc
lda ptr1
adc #1
sta TM + tm::tm_mday
lda ptr1+1
adc #0
sta TM + tm::tm_mday+1
; Now divide the number of remaining seconds by 3600,
; to get the number of hours, and the seconds in the
; current hour, in neat 16-bit integers.
; Load the previous division's remainder (in ptr2:tmp3:tmp4)
; as dividend
lda ptr2
sta ptr1
lda ptr2+1
sta ptr1+1
lda tmp3
sta sreg
; We ignore the high byte stored in tmp4 because it will be
; zero. We'll zero sreg+1 right below, when we'll have
; a convenient zero already in A.
; Load divisor
lda #<3600
sta ptr3
lda #>3600
sta ptr3+1
; Zero the two high bytes of the divisor and the high byte
; of the dividend.
.if .cpu .bitand CPU_ISET_65SC02
stz ptr4
stz ptr4+1
stz sreg+1
.else
lda #$00
sta ptr4
sta ptr4+1
sta sreg+1
.endif
; Do the division
jsr udiv32
; Store year
lda #70
sta TM + tm::tm_year
; Store hours (the quotient of the last division)
lda ptr1
sta TM + tm::tm_hour
lda ptr1+1
sta TM + tm::tm_hour+1
; Store seconds (the remainder of the last division)
lda ptr2
sta TM + tm::tm_sec
lda ptr2+1
sta TM + tm::tm_sec+1
; The rest of the struct tm fields are zero. mktime
; will take care of shifting extra seconds to minutes,
; and extra days to months and years.
; Call mktime
lda #<TM
ldx #>TM
jsr _mktime
; And return our pointer
lda #<TM
ldx #>TM
rts
.bss
TM: .tag tm

9
libsrc/common/mktime.c
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@ -65,7 +65,8 @@ static const unsigned MonthDays [] = {
/* Code */
/*****************************************************************************/
/* use statics for size optimisation (~34 bytes) */
#pragma static-locals(push, on)
time_t __fastcall__ mktime (register struct tm* TM)
/* Make a time in seconds since 1/1/1970 from the broken down time in TM.
@ -74,8 +75,8 @@ time_t __fastcall__ mktime (register struct tm* TM)
*/
{
register div_t D;
static int Max;
static unsigned DayCount;
int Max;
unsigned DayCount;
/* Check if TM is valid */
if (TM == 0) {
@ -182,3 +183,5 @@ time_t __fastcall__ mktime (register struct tm* TM)
((unsigned) TM->tm_sec) -
_tz.timezone;
}
#pragma static-locals(pop)