[PATCH] D107658: [RISCV] Teach isel to select ADDW/SUBW/MULW/SLLIW when only the lower 32-bits are used.

[Craig Topper via Phabricator via llvm-commits]

craig.topper created this revision.
craig.topper added reviewers: asb, luismarques, frasercrmck, jrtc27, evandro, khchen, arcbbb, HsiangKai.
Herald added subscribers: StephenFan, vkmr, apazos, sameer.abuasal, s.egerton, Jim, benna, psnobl, jocewei, PkmX, the_o, brucehoult, MartinMosbeck, rogfer01, edward-jones, zzheng, shiva0217, kito-cheng, niosHD, sabuasal, simoncook, johnrusso, rbar, hiraditya.
craig.topper requested review of this revision.
Herald added a subscriber: MaskRay.
Herald added a project: LLVM.

We normally select these when the root node is a sext_inreg, but
SimplifyDemandedBits can sometimes bypass the sext_inreg for some
users. This can create situation where sext_inreg+add/sub/mul/shl
is selected to a W instruction, and then the add/sub/mul/shl is
separately selected to a non-W instruction with the same inputs.

This patch tries to detect when it would still be ok to use a W
instruction without the sext_inreg by checking the direct users.
This can allow the W instruction to CSE with any created for a
sext_inreg+add/sub/mul/shl. To minimize complexity and cost of
checking, we make no attempt to determine if the CSE will happen
and just always use a W instruction when we can.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D107658

Files:
  llvm/lib/Target/RISCV/RISCVISelDAGToDAG.cpp
  llvm/lib/Target/RISCV/RISCVISelDAGToDAG.h
  llvm/lib/Target/RISCV/RISCVInstrInfo.td
  llvm/lib/Target/RISCV/RISCVInstrInfoM.td
  llvm/test/CodeGen/RISCV/add-imm.ll
  llvm/test/CodeGen/RISCV/atomic-cmpxchg.ll
  llvm/test/CodeGen/RISCV/atomic-rmw.ll
  llvm/test/CodeGen/RISCV/atomic-signext.ll
  llvm/test/CodeGen/RISCV/calling-conv-lp64-lp64f-lp64d-common.ll
  llvm/test/CodeGen/RISCV/div.ll
  llvm/test/CodeGen/RISCV/mul.ll
  llvm/test/CodeGen/RISCV/rv64i-demanded-bits.ll
  llvm/test/CodeGen/RISCV/rv64i-w-insts-legalization.ll
  llvm/test/CodeGen/RISCV/rv64zbb.ll
  llvm/test/CodeGen/RISCV/rvv/fixed-vectors-ctlz.ll
  llvm/test/CodeGen/RISCV/shadowcallstack.ll
  llvm/test/CodeGen/RISCV/shift-masked-shamt.ll
  llvm/test/CodeGen/RISCV/srem-lkk.ll
  llvm/test/CodeGen/RISCV/srem-vector-lkk.ll
  llvm/test/CodeGen/RISCV/urem-vector-lkk.ll
  llvm/test/CodeGen/RISCV/vararg.ll
  llvm/test/CodeGen/RISCV/xaluo.ll

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