operator=(~) and assign(~) share similar names but, until now, have not
shared the same functionality. This patch introduces the usage of
QByteArray::assign() within the non-sharing assignment operator to
effectively boost efficiency by reusing the available capacity.
Since these assignment operators are frequently used in many places,
both within Qt and non-Qt code, this patch comes with benchmarks.
The preview of the benchmark results are compared with this patch and
before this patch. The findings indicate a slight enhancement in
performance associated with the assignment operator. Despite the results
displaying only a minor improvement, progress has been made. Therefore
use assign(QByteArrayView) as replacement.
(x86_64-little_endian-lp64 shared (dynamic) release build (O3); by
gcc 13.2.1, endeavouros ; 13th Gen Intel(R) Core(TM) i9-13900K
benchmarks executed with -perf -iterations 1000000
* The last value at the EOL represent the string size.
QByteArray &operator=(const char *ch) (current)
65 cycles/iter; 317 instructions/iter; 16.0 nsec/iter (5)
71.7 cycles/iter; 383 instructions/iter; 13.0 nsec/iter (10)
59.8 cycles/iter; 318 instructions/iter; 10.9 nsec/iter (20)
70.8 cycles/iter; 340 instructions/iter; 12.9 nsec/iter (50)
80.2 cycles/iter; 419 instructions/iter; 14.6 nsec/iter (100)
164.2 cycles/iter; 899 instructions/iter; 29.9 nsec/iter (500)
260.5 cycles/iter; 1522 instructions/iter; 45.6 nsec/iter (1'000)
QByteArray &operator=(const char *ch) (before)
66.8 cycles/iter; 317 instructions/iter; 16.9 nsec/iter (5)
76.5 cycles/iter; 383 instructions/iter; 13.9 nsec/iter (10)
63.7 cycles/iter; 318 instructions/iter; 11.6 nsec/iter (20)
71.6 cycles/iter; 344 instructions/iter; 13.0 nsec/iter (50)
77.5 cycles/iter; 419 instructions/iter; 14.1 nsec/iter (100)
143.4 cycles/iter; 893 instructions/iter; 26.1 nsec/iter (500)
270.8 cycles/iter; 1516 instructions/iter; 48.2 nsec/iter (1'000)
Task-number: QTBUG-106201
Change-Id: I0745c33f0f61f1d844a60960cc55f565320d5945
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
3c38efbfe4