[all-commits] [llvm/llvm-project] b55d4c: Revert "[LV] Remove `LoopVectorizationCostModel::u...

[David Green via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: b55d4c2ad8ea083f64f9cd851ac28bfd9a1a020c
      https://github.com/llvm/llvm-project/commit/b55d4c2ad8ea083f64f9cd851ac28bfd9a1a020c
  Author: David Green <david.green at arm.com>
  Date:   2022-02-09 (Wed, 09 Feb 2022)

  Changed paths:
    M llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
    M llvm/test/Analysis/CostModel/X86/masked-gather-i32-with-i8-index.ll
    M llvm/test/Analysis/CostModel/X86/masked-gather-i64-with-i8-index.ll
    M llvm/test/Analysis/CostModel/X86/masked-interleaved-load-i16.ll
    M llvm/test/Analysis/CostModel/X86/masked-interleaved-store-i16.ll
    M llvm/test/Analysis/CostModel/X86/masked-load-i16.ll
    M llvm/test/Analysis/CostModel/X86/masked-load-i32.ll
    M llvm/test/Analysis/CostModel/X86/masked-load-i64.ll
    M llvm/test/Analysis/CostModel/X86/masked-load-i8.ll
    M llvm/test/Transforms/LoopVectorize/AArch64/tail-fold-uniform-memops.ll
    M llvm/test/Transforms/LoopVectorize/X86/gather_scatter.ll
    M llvm/test/Transforms/LoopVectorize/X86/x86-interleaved-accesses-masked-group.ll
    M llvm/test/Transforms/LoopVectorize/if-pred-stores.ll
    M llvm/test/Transforms/LoopVectorize/memdep-fold-tail.ll
    M llvm/test/Transforms/LoopVectorize/optsize.ll
    M llvm/test/Transforms/LoopVectorize/tripcount.ll
    M llvm/test/Transforms/LoopVectorize/vplan-sink-scalars-and-merge.ll

  Log Message:
  -----------
  Revert "[LV] Remove `LoopVectorizationCostModel::useEmulatedMaskMemRefHack()`"

This reverts commit 77a0da926c9ea86afa9baf28158d79c7678fc6b9 as we've
received multiple reports of this significantly impacting performance,
in ways that don't seem to just be target specific cost models going
wrong. I would offer some reproducers, but the test changes here seem to
be full of them!

Reverting for now and hopefully we can remove the "hack" more carefully
as we go.