[all-commits] [llvm/llvm-project] c55899: [DAGCombiner] Hoist funnel shifts from logic opera...

[fzhinkin via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: c55899f763b6d4510fd77711af3b605fd444e7fa
      https://github.com/llvm/llvm-project/commit/c55899f763b6d4510fd77711af3b605fd444e7fa
  Author: Filipp Zhinkin <filipp.zhinkin at gmail.com>
  Date:   2022-08-05 (Fri, 05 Aug 2022)

  Changed paths:
    M llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
    M llvm/test/CodeGen/X86/funnel-shift-logic-fold.ll
    M llvm/test/CodeGen/X86/icmp-shift-opt.ll

  Log Message:
  -----------
  [DAGCombiner] Hoist funnel shifts from logic operation

Hoist funnel shift from logic op:
logic_op (FSH x0, x1, s), (FSH y0, y1, s) --> FSH (logic_op x0, y0), (logic_op x1, y1), s

The transformation improves code generated for some cases related to
issue https://github.com/llvm/llvm-project/issues/49541.

Reduced amount of funnel shifts can also improve throughput on x86 CPUs by utilizing more
available ports: https://quick-bench.com/q/gC7AKkJJsDZzRrs_JWDzm9t_iDM

Transformation correctness checks:
https://alive2.llvm.org/ce/z/TKPULH
https://alive2.llvm.org/ce/z/UvTd_9
https://alive2.llvm.org/ce/z/j8qW3_
https://alive2.llvm.org/ce/z/7Wq7gE
https://alive2.llvm.org/ce/z/Xr5w8R
https://alive2.llvm.org/ce/z/D5xe_E
https://alive2.llvm.org/ce/z/2yBZiy

Differential Revision: https://reviews.llvm.org/D130994