That is, return everything in the return argument. On the SysV ABI, that
means everything gets returned in registers, in both 32- and 64-bit
platforms (unlike QtPrivate::ParsedNumber). There's a minor but
perceptible performance improvement in parsing strings and byte arrays.
Before:
Parsed string "42" "1234" "-1548860221"
Clock (ns) 16.673 18.878 25.517
CPU cycles 46.548 52.704 71.243
Instructions 201 233 331
After:
Parsed string "42" "1234" "-1548860221"
Clock (ns) 15.577 17.998 24.198
CPU cycles 43.491 49.942 67.552
Instructions 179 211 308
On my Core i7-1165G7 @ 2.80 GHz, the 22-23 instruction gain per
iteration results in half the expected clock gain in runtime (22 /
2.8 GHz = 7.8 ns) because of a slightly lower instruction per cycle
rate. That's acceptable because we need less speculative execution.
Pick-to: 6.4
Task-number: QTBUG-107788
Change-Id: I07ec23f3cb174fb197c3fffd17220fd64d473cc0
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>
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