[llvm] [SmallPtrSet] Optimize find/erase (PR #104740)

[Fangrui Song via llvm-commits]

MaskRay wrote:

https://llvm-compile-time-tracker.com/compare.php?from=c64ce8bf283120fd145a57d0e61f9697f719139d&to=0de5f8109403426ad82a0a48c2a43eaec15ab476&stat=instructions%3Au

stage1-O3:

|Benchmark|Old|New|
|--- |--- |--- |
|kimwitu++|42462M|42452M (-0.02%)|
|sqlite3|38313M|38264M (-0.13%)|
|consumer-typeset|34798M|34768M (-0.09%)|
|Bullet|103581M|103529M (-0.05%)|
|tramp3d-v4|86502M|86370M (-0.15%)|
|mafft|36182M|36158M (-0.07%)|
|ClamAV|55277M|55214M (-0.11%)|
|lencod|66504M|66467M (-0.05%)|
|SPASS|46805M|46733M (-0.15%)|
|7zip|212496M|212337M (-0.07%)|
|geomean|60628M|60573M (-0.09%)|


https://github.com/llvm/llvm-project/pull/104740