[PATCH] D98857: [DAG] computeKnownBits - add ISD::MULHS/ISD::MULHU handling

[Simon Pilgrim via Phabricator via llvm-commits]

RKSimon created this revision.
RKSimon added reviewers: spatel, dmgreen, arsenm, foad, nagisa, craig.topper, lebedev.ri.
Herald added subscribers: dexonsmith, kerbowa, pengfei, hiraditya, nhaehnle, jvesely, nemanjai.
RKSimon requested review of this revision.
Herald added a subscriber: wdng.
Herald added a project: LLVM.

Reuse the existing KnownBits multiplication code to handle the 'extend + multiply + extract high bits' pattern for multiply-high ops.

Noticed while looking at the codegen for D88785 <https://reviews.llvm.org/D88785> / D98587 <https://reviews.llvm.org/D98587> - the patch helps division-by-constant expansion code in particular, which suggests that we might have some further KnownBits div/rem cases we could handle - but this was far easier to implement.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D98857

Files:
  llvm/include/llvm/Support/KnownBits.h
  llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
  llvm/lib/Support/KnownBits.cpp
  llvm/test/CodeGen/AMDGPU/atomic_optimizations_global_pointer.ll
  llvm/test/CodeGen/AMDGPU/atomic_optimizations_local_pointer.ll
  llvm/test/CodeGen/AMDGPU/sdiv64.ll
  llvm/test/CodeGen/AMDGPU/srem64.ll
  llvm/test/CodeGen/AMDGPU/udiv64.ll
  llvm/test/CodeGen/AMDGPU/urem-seteq-illegal-types.ll
  llvm/test/CodeGen/AMDGPU/urem64.ll
  llvm/test/CodeGen/ARM/select-imm.ll
  llvm/test/CodeGen/PowerPC/urem-seteq-illegal-types.ll
  llvm/test/CodeGen/X86/2008-04-17-CoalescerBug.ll
  llvm/test/CodeGen/X86/combine-udiv.ll
  llvm/test/CodeGen/X86/omit-urem-of-power-of-two-or-zero-when-comparing-with-zero.ll
  llvm/unittests/Support/KnownBitsTest.cpp

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