[all-commits] [llvm/llvm-project] 975824: [LV] Use SCEV to check if the trip count <= VF * UF.

[Florian Hahn via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 9758242046b3cdce6fb713acb6d3f5bfaa933a47
      https://github.com/llvm/llvm-project/commit/9758242046b3cdce6fb713acb6d3f5bfaa933a47
  Author: Florian Hahn <flo at fhahn.com>
  Date:   2022-12-24 (Sat, 24 Dec 2022)

  Changed paths:
    M llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp
    M llvm/test/Transforms/LoopVectorize/vector-loop-backedge-elimination.ll

  Log Message:
  -----------
  [LV] Use SCEV to check if the trip count <= VF * UF.

Just comparing constant trip counts causes LV to miss cases where the
vector loop body only executes once.

The motivation for this is to remove the need for unrolling to remove
vector loop back-edges, if the body only executes once in more cases.

Reviewed By: Ayal

Differential Revision: https://reviews.llvm.org/D133017