[all-commits] [llvm/llvm-project] 40c083: [DAGCombiner] Add command line options to guard st...

[weiguozhi via All-commits]

  Branch: refs/heads/master
  Home:   https://github.com/llvm/llvm-project
  Commit: 40c08367e411a178404d4f01a82f651188f2ed01
      https://github.com/llvm/llvm-project/commit/40c08367e411a178404d4f01a82f651188f2ed01
  Author: Guozhi Wei <carrot at google.com>
  Date:   2020-05-29 (Fri, 29 May 2020)

  Changed paths:
    M llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
    A llvm/test/CodeGen/X86/clear-bitfield.ll
    A llvm/test/CodeGen/X86/disable-shrink-store.ll

  Log Message:
  -----------
  [DAGCombiner] Add command line options to guard store width reduction
optimizations

As discussed in the thread http://lists.llvm.org/pipermail/llvm-dev/2020-May/141838.html,
some bit field access width can be reduced by ReduceLoadOpStoreWidth, some
can't. If two accesses are very close, and the first access width is reduced,
the second is not. Then the wide load of second access will be stalled for long
time.

This patch add command line options to guard ReduceLoadOpStoreWidth and
ShrinkLoadReplaceStoreWithStore, so users can use them to disable these
store width reduction optimizations.

Differential Revision: https://reviews.llvm.org/D80745