[PATCH] D68974: [ARM] Lower sadd_sat to qadd8 and qadd16

[Dave Green via Phabricator via llvm-commits]

dmgreen created this revision.
dmgreen added reviewers: efriedma, samparker, SjoerdMeijer.
Herald added subscribers: hiraditya, kristof.beyls.
Herald added a project: LLVM.

Lower the target independent signed saturating instructions to qadd8 and qadd16. I've lowered this from a sadd_sat, catching the node early before it is promoted. This also adds a QADD8b and QADD16b node to mean the bottom "lane" of a qadd8/qadd16, so that we can call demand bits on it to show that it does not use the upper bits.

Also handles QSUB8 and QSUB16.


https://reviews.llvm.org/D68974

Files:
  llvm/lib/Target/ARM/ARMISelLowering.cpp
  llvm/lib/Target/ARM/ARMISelLowering.h
  llvm/lib/Target/ARM/ARMInstrInfo.td
  llvm/lib/Target/ARM/ARMInstrThumb2.td
  llvm/test/CodeGen/ARM/sadd_sat.ll
  llvm/test/CodeGen/ARM/sadd_sat_plus.ll
  llvm/test/CodeGen/ARM/ssub_sat.ll
  llvm/test/CodeGen/ARM/ssub_sat_plus.ll

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