[all-commits] [llvm/llvm-project] 682e73: [LV] Fix FoldTail under user VF and UF

[azaks via All-commits]

  Branch: refs/heads/master
  Home:   https://github.com/llvm/llvm-project
  Commit: 682e739638a9c569d4c5c358ab75365175a95efc
      https://github.com/llvm/llvm-project/commit/682e739638a9c569d4c5c358ab75365175a95efc
  Author: Ayal Zaks <ayal.zaks at intel.com>
  Date:   2020-05-19 (Tue, 19 May 2020)

  Changed paths:
    M llvm/lib/Transforms/Vectorize/LoopVectorizationPlanner.h
    M llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
    A llvm/test/Transforms/LoopVectorize/pr45679-fold-tail-by-masking.ll

  Log Message:
  -----------
  [LV] Fix FoldTail under user VF and UF

LV considers an internally computed MaxVF to decide if a constant trip-count is
a multiple of any subsequently chosen VF, and conclude that no scalar remainder
iterations (tail) will be left for Fold Tail to handle. If an external VF is
provided via -force-vector-width, it must be considered instead of the internal
MaxVF.
If an external UF is provided via -force-vector-interleave, it too must be
considered in addition to MaxVF or user VF.

Fixes PR45679.

Differential Revision: https://reviews.llvm.org/D80085