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Use bulk conversion in BCMath of BCD/CHAR where possible #14103

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merged 2 commits into from
May 1, 2024
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Use bulk conversion in BCMath of BCD/CHAR where possible #14103

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Use bulk conversion in BCMath of BCD/CHAR where possible
nielsdos May 1, 2024
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nielsdos May 1, 2024
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2 changes: 1 addition & 1 deletion ext/bcmath/config.m4
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Original file line number Diff line number Diff line change
Expand Up @@ -8,7 +8,7 @@ if test "$PHP_BCMATH" != "no"; then
libbcmath/src/add.c libbcmath/src/div.c libbcmath/src/init.c libbcmath/src/neg.c libbcmath/src/raisemod.c libbcmath/src/sub.c \
libbcmath/src/compare.c libbcmath/src/divmod.c libbcmath/src/int2num.c libbcmath/src/num2long.c libbcmath/src/output.c libbcmath/src/recmul.c \
libbcmath/src/sqrt.c libbcmath/src/zero.c libbcmath/src/doaddsub.c libbcmath/src/floor_or_ceil.c libbcmath/src/nearzero.c libbcmath/src/num2str.c \
libbcmath/src/raise.c libbcmath/src/rmzero.c libbcmath/src/round.c libbcmath/src/str2num.c,
libbcmath/src/raise.c libbcmath/src/rmzero.c libbcmath/src/round.c libbcmath/src/str2num.c libbcmath/src/convert.c,
$ext_shared,, -DZEND_ENABLE_STATIC_TSRMLS_CACHE=1)
PHP_ADD_BUILD_DIR($ext_builddir/libbcmath/src)
AC_DEFINE(HAVE_BCMATH, 1, [Whether you have bcmath])
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2 changes: 1 addition & 1 deletion ext/bcmath/config.w32
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Expand Up @@ -8,7 +8,7 @@ if (PHP_BCMATH == "yes") {
raisemod.c sub.c compare.c divmod.c int2num.c \
num2long.c output.c recmul.c sqrt.c zero.c doaddsub.c \
floor_or_ceil.c nearzero.c num2str.c raise.c rmzero.c str2num.c \
round.c", "bcmath");
round.c convert.c", "bcmath");

AC_DEFINE('HAVE_BCMATH', 1, 'Have BCMATH library');
}
59 changes: 59 additions & 0 deletions ext/bcmath/libbcmath/src/convert.c
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@@ -0,0 +1,59 @@
/*
+----------------------------------------------------------------------+
| Copyright (c) The PHP Group |
+----------------------------------------------------------------------+
| This source file is subject to version 3.01 of the PHP license, |
| that is bundled with this package in the file LICENSE, and is |
| available through the world-wide-web at the following url: |
| https://www.php.net/license/3_01.txt |
| If you did not receive a copy of the PHP license and are unable to |
| obtain it through the world-wide-web, please send a note to |
| license@php.net so we can mail you a copy immediately. |
+----------------------------------------------------------------------+
| Authors: Niels Dossche <nielsdos@php.net> |
+----------------------------------------------------------------------+
*/

#include "bcmath.h"
#include "convert.h"

#define SWAR_ONES (~((size_t) 0) / 0xFF)
#define SWAR_REPEAT(x) (SWAR_ONES * (x))

static char *bc_copy_and_shift_numbers(char *dest, const char *source, const char *source_end, unsigned char shift, bool add)
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Possible add a restrict keyword for dest and source? As those APIs are only used within other C files, so we don't need to have compatibility with C++?

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Right, I'll add the restrict keyword.

I'll explain what the code does.
The intention is to copy each byte from source to dest, but subtract or add '0' to each byte.
The idea of this patch is to try to read+write 8 bytes at once, adding/subtracting '0' to each byte also in parallel.

SWAR_ONES will be of the form 0x01010101 for 32-bit or 0x0101010101010101 for 64-bit.
Example: SWAR_ONES * 0xAB will therefore be equal to 0xABABABAB for 32-bit or 0xABABABABABABABAB for 64-bit.
So in this case, for SWAR_REPEAT('0'), it will be a 32/64-bit word where each byte is equal to '0', i.e. 0x303030...

Since we know that subtract/add overflow from one byte to another can't occur, we can subtract/add with 0x303030... to the entire 4/8 bytes which will be equivalent to adding 0x30 to each byte individually.

And to be complete: SWAR stands for "SIMD Within A Register"

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Ahhh okay, well could you please write this in a comment in the file? :D

{
size_t bulk_shift = SWAR_REPEAT(shift);
if (!add) {
bulk_shift = -bulk_shift;
shift = -shift;
}

while (source + sizeof(size_t) <= source_end) {
size_t bytes;
memcpy(&bytes, source, sizeof(bytes));

bytes += bulk_shift;
memcpy(dest, &bytes, sizeof(bytes));

source += sizeof(size_t);
dest += sizeof(size_t);
}

while (source < source_end) {
*dest = *source + shift;
dest++;
source++;
}

return dest;
}

char *bc_copy_ch_val(char *dest, const char *source, const char *source_end)
{
return bc_copy_and_shift_numbers(dest, source, source_end, '0', false);
}

char *bc_copy_bcd_val(char *dest, const char *source, const char *source_end)
{
return bc_copy_and_shift_numbers(dest, source, source_end, '0', true);
}
23 changes: 23 additions & 0 deletions ext/bcmath/libbcmath/src/convert.h
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@@ -0,0 +1,23 @@
/*
+----------------------------------------------------------------------+
| Copyright (c) The PHP Group |
+----------------------------------------------------------------------+
| This source file is subject to version 3.01 of the PHP license, |
| that is bundled with this package in the file LICENSE, and is |
| available through the world-wide-web at the following url: |
| https://www.php.net/license/3_01.txt |
| If you did not receive a copy of the PHP license and are unable to |
| obtain it through the world-wide-web, please send a note to |
| license@php.net so we can mail you a copy immediately. |
+----------------------------------------------------------------------+
| Authors: Niels Dossche <nielsdos@php.net> |
+----------------------------------------------------------------------+
*/

#ifndef BCMATH_CONVERT_H
#define BCMATH_CONVERT_H

char *bc_copy_ch_val(char *dest, const char *source, const char *source_end);
char *bc_copy_bcd_val(char *dest, const char *source, const char *source_end);

#endif
14 changes: 6 additions & 8 deletions ext/bcmath/libbcmath/src/num2str.c
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Expand Up @@ -30,7 +30,7 @@
*************************************************************************/

#include "bcmath.h"
#include <stddef.h>
#include "convert.h"
#include "zend_string.h"

/* Convert a numbers to a string. Base 10 only.*/
Expand All @@ -40,9 +40,10 @@ zend_string *bc_num2str_ex(bc_num num, size_t scale)
char *sptr;
size_t index;
bool signch;
size_t min_scale = MIN(num->n_scale, scale);

/* Number of sign chars. */
signch = num->n_sign != PLUS && !bc_is_zero_for_scale(num, MIN(num->n_scale, scale));
signch = num->n_sign != PLUS && !bc_is_zero_for_scale(num, min_scale);
/* Allocate the string memory. */
if (scale > 0) {
str = zend_string_alloc(num->n_len + scale + signch + 1, 0);
Expand All @@ -56,16 +57,13 @@ zend_string *bc_num2str_ex(bc_num num, size_t scale)

/* Load the whole number. */
const char *nptr = num->n_value;
for (index = num->n_len; index > 0; index--) {
*sptr++ = BCD_CHAR(*nptr++);
}
sptr = bc_copy_bcd_val(sptr, nptr, nptr + num->n_len);
nptr += num->n_len;

/* Now the fraction. */
if (scale > 0) {
*sptr++ = '.';
for (index = 0; index < scale && index < num->n_scale; index++) {
*sptr++ = BCD_CHAR(*nptr++);
}
sptr = bc_copy_bcd_val(sptr, nptr, nptr + min_scale);
for (index = num->n_scale; index < scale; index++) {
*sptr++ = BCD_CHAR(0);
}
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19 changes: 4 additions & 15 deletions ext/bcmath/libbcmath/src/str2num.c
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Original file line number Diff line number Diff line change
Expand Up @@ -30,6 +30,7 @@
*************************************************************************/

#include "bcmath.h"
#include "convert.h"
#include <stdbool.h>
#include <stddef.h>

Expand Down Expand Up @@ -124,24 +125,12 @@ bool bc_str2num(bc_num *num, char *str, size_t scale, bool auto_scale)
* If zero_int is true and the str_scale is 0, there is an early return,
* so here str_scale is always greater than 0.
*/
while (fractional_ptr < fractional_end) {
*nptr = CH_VAL(*fractional_ptr);
nptr++;
fractional_ptr++;
}
nptr = bc_copy_ch_val(nptr, fractional_ptr, fractional_end);
} else {
const char *integer_end = integer_ptr + digits;
while (integer_ptr < integer_end) {
*nptr = CH_VAL(*integer_ptr);
nptr++;
integer_ptr++;
}
nptr = bc_copy_ch_val(nptr, integer_ptr, integer_end);
if (str_scale > 0) {
while (fractional_ptr < fractional_end) {
*nptr = CH_VAL(*fractional_ptr);
nptr++;
fractional_ptr++;
}
nptr = bc_copy_ch_val(nptr, fractional_ptr, fractional_end);
}
}

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