Skip to content

round: Abolished the CPU rounding mode change and modified it to a different logic. #13435

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
merged 2 commits into from
Mar 8, 2024
Merged

round: Abolished the CPU rounding mode change and modified it to a different logic. #13435

Changes from all commits
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
4aed7e7
Fixed to avoid incorrect optimization with llvm15.0.0
SakiTakamachi Feb 20, 2024
ed08faa
Removed changing CPU round mode and added processing to detect and co…
SakiTakamachi Feb 20, 2024
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
33 changes: 19 additions & 14 deletions ext/standard/math.c
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -27,7 +27,6 @@
#include <float.h>
#include <math.h>
#include <stdlib.h>
#include <fenv.h>

#include "basic_functions.h"

Expand Down Expand Up @@ -163,9 +162,7 @@ static inline double php_round_helper(double integral, double value, double expo
* mode. For the specifics of the algorithm, see http://wiki.php.net/rfc/rounding
*/
PHPAPI double _php_math_round(double value, int places, int mode) {
double exponent;
double tmp_value;
int cpu_round_mode;
double exponent, tmp_value, tmp_value2;

if (!zend_finite(value) || value == 0.0) {
return value;
Expand All @@ -182,21 +179,29 @@ PHPAPI double _php_math_round(double value, int places, int mode) {
* 0.285 * 10000000000 => 2849999999.9999995
* floor(0.285 * 10000000000) => 2849999999
*
* Therefore, change the CPU rounding mode to away from 0 only from
* fegetround to fesetround.
* Add 1 to the absolute value of the value adjusted by floor or ceil, use the
* exponent to return it to its original precision, and compare it with value.
* If it is equal to value, it is assumed that the absolute value is 1 smaller
* due to error and will be corrected.
* e.g.
* 0.285 * 10000000000 => 2850000000.0
* floor(0.285 * 10000000000) => 2850000000
* 0.285 * 10000000000 => 2849999999.9999995
* floor(0.285 * 10000000000) => 2849999999 (tmp_value)
* tmp_value2 = 2849999999 + 1 => 2850000000
* 2850000000 / 10000000000 == 0.285 => true
* tmp_value = tmp_value2
*/
cpu_round_mode = fegetround();

if (value >= 0.0) {
fesetround(FE_UPWARD);
tmp_value = floor(places > 0 ? value * exponent : value / exponent);
tmp_value = floor(places > 0 ? value * exponent : value / exponent);
tmp_value2 = tmp_value + 1.0;
} else {
fesetround(FE_DOWNWARD);
tmp_value = ceil(places > 0 ? value * exponent : value / exponent);
tmp_value = ceil(places > 0 ? value * exponent : value / exponent);
tmp_value2 = tmp_value - 1.0;
}

if ((places > 0 ? tmp_value2 / exponent : tmp_value2 * exponent) == value) {
tmp_value = tmp_value2;
}
fesetround(cpu_round_mode);

/* This value is beyond our precision, so rounding it is pointless */
if (fabs(tmp_value) >= 1e15) {
Expand Down