[all-commits] [llvm/llvm-project] 892af4: [ARM] Distribute MVE post-increments

[David Green via All-commits]

  Branch: refs/heads/master
  Home:   https://github.com/llvm/llvm-project
  Commit: 892af45c8697849666ea26e20492603b11533866
      https://github.com/llvm/llvm-project/commit/892af45c8697849666ea26e20492603b11533866
  Author: David Green <david.green at arm.com>
  Date:   2020-04-22 (Wed, 22 Apr 2020)

  Changed paths:
    M llvm/lib/Target/ARM/ARMBaseInstrInfo.h
    M llvm/lib/Target/ARM/ARMLoadStoreOptimizer.cpp
    M llvm/lib/Target/ARM/ARMLowOverheadLoops.cpp
    M llvm/test/CodeGen/ARM/O3-pipeline.ll
    M llvm/test/CodeGen/Thumb2/mve-float32regloops.ll
    M llvm/test/CodeGen/Thumb2/mve-ldst-postinc.ll
    M llvm/test/CodeGen/Thumb2/mve-postinc-distribute.ll
    M llvm/test/CodeGen/Thumb2/mve-postinc-distribute.mir
    M llvm/test/CodeGen/Thumb2/mve-satmul-loops.ll
    M llvm/test/CodeGen/Thumb2/mve-vld2-post.ll
    M llvm/test/CodeGen/Thumb2/mve-vld4-post.ll
    M llvm/test/CodeGen/Thumb2/mve-vldst4.ll
    M llvm/test/CodeGen/Thumb2/mve-vst2-post.ll
    M llvm/test/CodeGen/Thumb2/mve-vst4-post.ll

  Log Message:
  -----------
  [ARM] Distribute MVE post-increments

This adds some extra processing into the Pre-RA ARM load/store optimizer
to detect and merge MVE loads/stores and adds of the same base. This we
don't always turn into a post-inc during ISel, and due to the nature of
it being a graph we don't always know an order to use for the nodes, not
knowing which nodes to make post-inc and which to use the new post-inc
of. After ISel, we have an order that we can use to post-inc the
following instructions.

So this looks for a loads/store with a starting offset of 0, and an
add/sub from the same base, plus a number of other loads/stores. We then
do some checks and convert the zero offset load/store into a postinc
variant. Any loads/stores after it have the offset subtracted from their
immediates.  For example:
  LDR #4           LDR #4
  LDR #0           LDR_POSTINC #16
  LDR #8           LDR #-8
  LDR #12          LDR #-4
  ADD #16
It only handles MVE loads/stores at the moment. Normal loads/store will
be added in a followup patch, they just have some extra details to
ensure that we keep generating LDRD/LDM successfully.

Differential Revision: https://reviews.llvm.org/D77813