[all-commits] [llvm/llvm-project] 4e5e65: [VPlan] Only compute reg pressure if considered. N...

[Luke Lau via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 4e5e65e55dc5a5ffc6e3db321df7f118e1c42d38
      https://github.com/llvm/llvm-project/commit/4e5e65e55dc5a5ffc6e3db321df7f118e1c42d38
  Author: Luke Lau <luke at igalia.com>
  Date:   2025-09-05 (Fri, 05 Sep 2025)

  Changed paths:
    M llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
    M llvm/test/Transforms/LoopVectorize/AArch64/reg-usage.ll

  Log Message:
  -----------
  [VPlan] Only compute reg pressure if considered. NFCI (#156923)

In #149056 VF pruning was changed so that it only pruned VFs that
stemmed from MaxBandwidth being enabled.

However we always compute register pressure regardless of whether or not
max bandwidth is permitted for any VFs (via
`MaxPermissibleVFWithoutMaxBW`).

This skips the computation if not needed and renames the method for
clarity.

The diff in reg-usage.ll is due to the scalable VPlan not actually
having any maxbandwidth VFs, so I've changed it to check the
fixed-length VF instead, which is affected by maxbandwidth.



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