[all-commits] [llvm/llvm-project] 617aa6: [LV] Induction Variable does not remain scalar und...

[sjoerdmeijer via All-commits]

  Branch: refs/heads/master
  Home:   https://github.com/llvm/llvm-project
  Commit: 617aa64c84146468b384453375d1d34f97eb57db
      https://github.com/llvm/llvm-project/commit/617aa64c84146468b384453375d1d34f97eb57db
  Author: Sjoerd Meijer <sjoerd.meijer at arm.com>
  Date:   2020-05-07 (Thu, 07 May 2020)

  Changed paths:
    M llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
    M llvm/test/Transforms/LoopVectorize/AArch64/extractvalue-no-scalarization-required.ll
    M llvm/test/Transforms/LoopVectorize/AArch64/pr36032.ll
    M llvm/test/Transforms/LoopVectorize/ARM/sphinx.ll
    M llvm/test/Transforms/LoopVectorize/X86/constant-fold.ll
    M llvm/test/Transforms/LoopVectorize/X86/imprecise-through-phis.ll
    M llvm/test/Transforms/LoopVectorize/X86/load-deref-pred.ll
    M llvm/test/Transforms/LoopVectorize/X86/masked_load_store.ll
    M llvm/test/Transforms/LoopVectorize/X86/metadata-enable.ll
    M llvm/test/Transforms/LoopVectorize/X86/optsize.ll
    M llvm/test/Transforms/LoopVectorize/X86/pr35432.ll
    M llvm/test/Transforms/LoopVectorize/X86/pr36524.ll
    M llvm/test/Transforms/LoopVectorize/X86/small-size.ll
    M llvm/test/Transforms/LoopVectorize/X86/strided_load_cost.ll
    M llvm/test/Transforms/LoopVectorize/X86/vect.omp.force.small-tc.ll
    M llvm/test/Transforms/LoopVectorize/X86/x86-interleaved-accesses-masked-group.ll
    M llvm/test/Transforms/LoopVectorize/fcmp-vectorize.ll
    M llvm/test/Transforms/LoopVectorize/first-order-recurrence-complex.ll
    M llvm/test/Transforms/LoopVectorize/float-minmax-instruction-flag.ll
    M llvm/test/Transforms/LoopVectorize/if-pred-stores.ll
    M llvm/test/Transforms/LoopVectorize/if-reduction.ll
    M llvm/test/Transforms/LoopVectorize/multiple-strides-vectorization.ll
    M llvm/test/Transforms/LoopVectorize/pr35773.ll
    M llvm/test/Transforms/LoopVectorize/pr44488-predication.ll
    M llvm/test/Transforms/LoopVectorize/vector-intrinsic-call-cost.ll

  Log Message:
  -----------
  [LV] Induction Variable does not remain scalar under tail-folding.

If tail-folding of the scalar remainder loop is applied, the primary induction
variable is splat to a vector and used by the masked load/store vector
instructions, thus the IV does not remain scalar. Because we now mark
that the IV does not remain scalar for these cases, we don't emit the vector IV
if it is not used. Thus, the vectoriser produces less dead code.

Thanks to Ayal Zaks for the direction how to fix this.

Differential Revision: https://reviews.llvm.org/D78911