[PATCH] D123508: GlobalISel: Allow forming atomic/volatile G_ZEXTLOAD

[Matt Arsenault via Phabricator via llvm-commits]

arsenm created this revision.
arsenm added reviewers: aemerson, paquette, dsanders, bogner, reames.
Herald added subscribers: kerbowa, hiraditya, kristof.beyls, rovka, jvesely.
Herald added a project: All.
arsenm requested review of this revision.
Herald added a subscriber: wdng.
Herald added a project: LLVM.

SelectionDAG has a target hook, getExtendForAtomicOps, which it uses
in the computeKnownBits implementation for ATOMIC_LOAD. This is pretty
ugly (as is having a separate load opcode for atomics), so instead
allow making use of atomic zextload. Enable this for AArch64 since the
DAG path defaults in to the zext behavior.

      

The tablegen changes are pretty ugly, but partially helps migrate
SelectionDAG from using ISD::ATOMIC_LOAD to regular ISD::LOAD with
atomic memory operands. For now the DAG emitter will emit matchers for
patterns which the DAG will not produce.

      

I'm still a bit confused by the intent of the isLoad/isStore/isAtomic
bits. The DAG implementation rejects trying to use any of these in
combination. For now I've opted to make the isLoad checks also check
isAtomic, although I think having isLoad and isAtomic set on these
makes most sense.


https://reviews.llvm.org/D123508

Files:
  llvm/docs/GlobalISel/GenericOpcode.rst
  llvm/include/llvm/Target/GlobalISel/SelectionDAGCompat.td
  llvm/include/llvm/Target/TargetSelectionDAG.td
  llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp
  llvm/lib/Target/AArch64/AArch64InstrAtomics.td
  llvm/lib/Target/AArch64/GISel/AArch64LegalizerInfo.cpp
  llvm/test/CodeGen/AArch64/GlobalISel/legalizer-info-validation.mir
  llvm/test/CodeGen/AArch64/GlobalISel/prelegalizer-combiner-load-and-mask.mir
  llvm/test/CodeGen/AArch64/GlobalISel/select-zextload.mir
  llvm/test/CodeGen/AMDGPU/GlobalISel/postlegalizer-combiner-zextload-from-and.mir
  llvm/utils/TableGen/CodeGenDAGPatterns.cpp
  llvm/utils/TableGen/GlobalISelEmitter.cpp

-------------- next part --------------
A non-text attachment was scrubbed...
Name: D123508.421905.patch
Type: text/x-patch
Size: 25372 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20220411/801a6aab/attachment.bin>