[all-commits] [llvm/llvm-project] 532d05: [ARM] Attempt to distribute reductions

[David Green via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 532d05b714b3f64603be53398571d49a6f4b2f92
      https://github.com/llvm/llvm-project/commit/532d05b714b3f64603be53398571d49a6f4b2f92
  Author: David Green <david.green at arm.com>
  Date:   2021-07-30 (Fri, 30 Jul 2021)

  Changed paths:
    M llvm/lib/Target/ARM/ARMISelLowering.cpp
    M llvm/test/CodeGen/Thumb2/mve-vaddv.ll
    M llvm/test/CodeGen/Thumb2/mve-vecreduce-slp.ll

  Log Message:
  -----------
  [ARM] Attempt to distribute reductions

This adds a combine for adds of reductions, distributing them so that
they occur sequentially to enable better use of accumulating VADDVA
instructions. It combines:
  add(X, add(vecreduce(Y), vecreduce(Z))) ->
    add(add(X, vecreduce(Y)), vecreduce(Z))
and
  add(add(A, reduce(B)), add(C, reduce(D))) ->
    add(add(add(A, C), reduce(B)), reduce(D))

These together distribute the add's so that more reductions can be
selected to VADDVA.

Differential Revision: https://reviews.llvm.org/D106532