[PATCH] D96622: [DAG] PromoteIntRes_ADDSUBSHLSAT - use promoted ISD::USUBSAT directly

[Simon Pilgrim via Phabricator via llvm-commits]

RKSimon created this revision.
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As discussed on D96413 <https://reviews.llvm.org/D96413>, as long as the promoted bits of the args are zero we can use the basic ISD::USUBSAT pattern directly, without the shifting like we do for other ops.

I think something similar should be possible for ISD::UADDSAT as well, which I'll look at later.

Also, create a ISD::USUBSAT node directly - this will be expanded back by the legalizer later on if necessary.

https://alive2.llvm.org/ce/


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D96622

Files:
  llvm/lib/CodeGen/SelectionDAG/LegalizeIntegerTypes.cpp
  llvm/test/CodeGen/AArch64/usub_sat_vec.ll
  llvm/test/CodeGen/AMDGPU/usubsat.ll
  llvm/test/CodeGen/ARM/usub_sat_plus.ll
  llvm/test/CodeGen/X86/usub_sat_plus.ll
  llvm/test/CodeGen/X86/usub_sat_vec.ll

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