[all-commits] [llvm/llvm-project] 1247fd: [SimplifyCFG] Relax `cttz` cost check in `simplify...

[Antonio Frighetto via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 1247fddf3676543837b71965c88f021072513c63
      https://github.com/llvm/llvm-project/commit/1247fddf3676543837b71965c88f021072513c63
  Author: Antonio Frighetto <me at antoniofrighetto.com>
  Date:   2025-06-24 (Tue, 24 Jun 2025)

  Changed paths:
    M llvm/lib/Transforms/Utils/SimplifyCFG.cpp
    A llvm/test/Transforms/SimplifyCFG/X86/switch-of-powers-of-two.ll

  Log Message:
  -----------
  [SimplifyCFG] Relax `cttz` cost check in `simplifySwitchOfPowersOfTwo`

We should be able to allow `simplifySwitchOfPowersOfTwo` transform
to take place, as, on recent X86 targets, the weighted latency-size
appears to be 2. This favours computing trailing zeroes and indexing
into a smaller value table, over generating a jump table with an
indirect branch, which overall should be more efficient.



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