Add performance enhancements for SkRegion::op
When looking at pprof for a particularly gnarly set of
consecutive ops (see new benchmark), a curious hotspot
was distance_to_sentinel. We can look at the item just
before the current run to see how long it is instead of
using a loop to walk
the entire way. This had a ~15% improvement.
Before:
```
$ ./control_nanobench --match region
curr/maxrss loops min median mean max stddev samples config bench
91/88 MB 497 16.2ns 16.2ns 16.2ns 16.2ns 0% █▁▁▁▁▁▁▁▁▃ nonrendering region_contains_sect
92/88 MB 1 1.37s 1.46s 1.5s 1.77s 8% ▁▃▄▄█▅▂▁▃▂ nonrendering region_checkerboard
91/88 MB 1 1.23ms 1.26ms 1.27ms 1.35ms 3% █▃▂▄▁▁▅▁▁▆ nonrendering region_setRects_10000_sorted
91/88 MB 1 301µs 301µs 302µs 307µs 1% █▂▂█▁▁▁▁▁▁ nonrendering region_setRects_2500_sorted
91/88 MB 4 59.1µs 59.1µs 60.1µs 69.1µs 5% █▁▁▁▁▁▁▁▁▁ nonrendering region_setRects_500_sorted
91/88 MB 42 5.63µs 5.65µs 5.74µs 6.59µs 5% ▁▁▁▁▁▁█▁▁▁ nonrendering region_setRects_50_sorted
91/88 MB 1 5.5ms 5.51ms 5.52ms 5.55ms 0% █▂▃█▂▁▄▁█▃ nonrendering region_setRects_10000
91/88 MB 1 1.37ms 1.39ms 1.39ms 1.42ms 1% ▇▁▄▇▂▃█▁▁▇ nonrendering region_setRects_2500
91/88 MB 2 266µs 266µs 268µs 285µs 2% ▂▂▁▁█▁▁▁▁▁ nonrendering region_setRects_500
91/88 MB 12 16.9µs 16.9µs 17.6µs 22.5µs 10% ▂▁▁▁█▁▁▁▁▂ nonrendering region_setRects_50
```
After:
```
$ ./nanobench --match region
curr/maxrss loops min median mean max stddev samples config bench
91/88 MB 394 16.2ns 16.2ns 16.2ns 16.5ns 1% █▂▁▂▁▂▂▂▂▂ nonrendering region_contains_sect
92/88 MB 1 1.07s 1.1s 1.12s 1.26s 7% ▃▂█▄█▁▁▁▁▂ nonrendering region_checkerboard
92/88 MB 1 1.08ms 1.09ms 1.11ms 1.16ms 2% █▂▆▂▁▆▂▂▁▅ nonrendering region_setRects_10000_sorted
91/88 MB 2 266µs 268µs 270µs 285µs 2% ▁▃▂▂▁█▁▃▁▂ nonrendering region_setRects_2500_sorted
91/88 MB 5 52µs 52.3µs 53.1µs 59.1µs 4% ▂▁▁▁█▃▁▁▁▂ nonrendering region_setRects_500_sorted
91/88 MB 49 5µs 5.01µs 5.03µs 5.19µs 1% ▂▁▁▁▁▁▁█▂▂ nonrendering region_setRects_50_sorted
91/88 MB 1 4.85ms 4.86ms 4.87ms 4.91ms 0% ▄▃▃▆▂▁▂█▁▁ nonrendering region_setRects_10000
91/88 MB 1 1.22ms 1.22ms 1.23ms 1.26ms 1% █▁▁█▂▁▂█▂▂ nonrendering region_setRects_2500
91/88 MB 2 238µs 239µs 246µs 282µs 6% ▆▁▁▁▁▁▁▁█▁ nonrendering region_setRects_500
91/88 MB 13 14.6µs 14.7µs 14.8µs 15.6µs 2% █▂▁▄▁▁▁▁▁▁ nonrendering region_setRects_50
```
Bug: 511952524
Change-Id: I9c496ba621c61e62790cca62793de1fefee3a85e
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/1235636
Auto-Submit: Kaylee Lubick <kjlubick@google.com>
Reviewed-by: Florin Malita <fmalita@google.com>
Commit-Queue: Florin Malita <fmalita@google.com>
2 files changed
