[all-commits] [llvm/llvm-project] eaf48d: [VPlan] Replace BranchOnCount with BranchOnCond if...

[Florian Hahn via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: eaf48dd9b079c005d92ed9ef858f12bc452e71ef
      https://github.com/llvm/llvm-project/commit/eaf48dd9b079c005d92ed9ef858f12bc452e71ef
  Author: Florian Hahn <flo at fhahn.com>
  Date:   2022-06-06 (Mon, 06 Jun 2022)

  Changed paths:
    M llvm/lib/Transforms/Vectorize/VPlan.cpp
    M llvm/test/Transforms/LoopVectorize/AArch64/sve-low-trip-count.ll
    M llvm/test/Transforms/LoopVectorize/X86/constant-fold.ll
    M llvm/test/Transforms/LoopVectorize/X86/outer_loop_test1_no_explicit_vect_width.ll
    M llvm/test/Transforms/LoopVectorize/X86/pr34438.ll
    M llvm/test/Transforms/LoopVectorize/X86/pr42674.ll

  Log Message:
  -----------
  [VPlan] Replace BranchOnCount with BranchOnCond if TC <= UF * VF.

Try to simplify BranchOnCount to `BranchOnCond true` if TC <= UF * VF.

This is an alternative to D121899 which simplifies the VPlan directly
instead of doing so late in code-gen.

The potential benefit of doing this in VPlan is that this may help
cost-modeling in the future. The reason this is done in prepareToExecute
at the moment is that a single plan may be used for multiple VFs/UFs.

There are further simplifications that can be applied as follow ups:

1. Replace inductions with constants
2. Replace vector region with regular block.

Fixes #55354.

Depends on D126679.

Reviewed By: Ayal

Differential Revision: https://reviews.llvm.org/D126680