[PATCH] D49585: [ARM] Prefer lsls+lsrs over lsls+ands or lsrs+ands in Thumb1.

[Eli Friedman via Phabricator via llvm-commits]

efriedma created this revision.
efriedma added reviewers: SjoerdMeijer, t.p.northover, samparker.
Herald added a reviewer: javed.absar.
Herald added subscribers: chrib, kristof.beyls.

Saves materializing the immediate for the "ands".

Corresponding patterns exist for lsrs+lsls, but that seems less common in practice.

Not sure Select() is the best place for this; maybe it could be done as a target-specific combine? But I'm not sure what other consequences messing with the canonical form in DAGCombine would have.


Repository:
  rL LLVM

https://reviews.llvm.org/D49585

Files:
  lib/Target/ARM/ARMISelDAGToDAG.cpp
  test/CodeGen/Thumb/shift-and.ll

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