aleks-tmb wrote: @MatzeB Hi, could you please take a look. Described issue manifested after your patch: ``` SHA: b30c9c937802a78ef986cb4219eba51148f76e6c Author: Matthias Braun Date: 2023-09-11 14:23:29 -0700 -0700 LoopUnrollRuntime: Add weights to all branches ```
Actually your patch added branch weights scaling. So imagine a loop with scaled latch weights ratio from 1:2 to 127:254 one. If we decide to peel 3 iterations of such loop, initial 1:2 ratio will be updated as: ``` 0th peeled latch: 1:2 1st peeled latch: 1:1 2nd peeled latch: 1:1 ``` And with initial 127:254: ``` 0th peeled latch: 127:254 1st peeled latch: 127:127 2nd peeled latch: 127:1 ``` So the hotness of the mail loop header changed from neutral 1:1 to 127:1, making it almost unreachable. In my patch I tried to make it: https://github.com/llvm/llvm-project/pull/70094 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
