AuroraMiddleware/qt5base-lts
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

Performance improvement for integer->QString conversion

Browse Source 
The compiler can generate better code when the base is known
in integer to string conversion. This patch creates separate branches
for known bases and leaves generic code as a fallback.
Saved about 12ns per conversion of 12345678 in one measurement.

Task-number: QTBUG-87330
Change-Id: I44c9bb467cf211f7e617ed55104476062296bba6
Reviewed-by: Andrei Golubev <andrei.golubev@qt.io>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
This commit is contained in:
Andreas Buhr 2020-10-26 19:33:47 +01:00
parent 81957e753e
commit 0d3fb3784b
1 changed files with 43 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

47
src/corelib/text/qlocale_tools.cpp
View File

@ -468,11 +468,50 @@ QString qulltoa(qulonglong number, int base, const QStringView zero)
char16_t buff[maxlen];
char16_t *const end = buff + maxlen, *p = end;
// Performance-optimized code. Compiler can generate faster code when base is known.
if (base != 10 || zero == u"0") {
while (number != 0) {
int c = number % base;
*--p = c < 10 ? '0' + c : c - 10 + 'a';
number /= base;
switch (base) {
#ifndef __OPTIMIZE_SIZE__
case 10:
while (number != 0) {
const int c = number % 10;
const qulonglong temp = number / 10;
*--p = '0' + c;
number = temp;
}
break;
case 2:
while (number != 0) {
const int c = number % 2;
const qulonglong temp = number / 2;
*--p = '0' + c;
number = temp;
}
break;
case 8:
while (number != 0) {
const int c = number % 8;
const qulonglong temp = number / 8;
*--p = '0' + c;
number = temp;
}
break;
case 16:
while (number != 0) {
const int c = number % 16;
const qulonglong temp = number / 16;
*--p = c < 10 ? '0' + c : c - 10 + 'a';
number = temp;
}
break;
#endif
default:
while (number != 0) {
const int c = number % base;
const qulonglong temp = number / base;
*--p = c < 10 ? '0' + c : c - 10 + 'a';
number = temp;
}
}
} else if (zero.size() && !zero.at(0).isSurrogate()) {
const char16_t zeroUcs2 = zero.at(0).unicode();