[PATCH] D142535: [DAGCombine] Fold redundant select

[Sam Parker via Phabricator via llvm-commits]

samparker created this revision.
samparker added reviewers: RKSimon, craig.topper.
Herald added subscribers: luke, pmatos, asb, armkevincheng, sjarus, eric-k256, frasercrmck, ecnelises, luismarques, apazos, sameer.abuasal, pengfei, s.egerton, Jim, jocewei, PkmX, the_o, brucehoult, MartinMosbeck, rogfer01, edward-jones, zzheng, jrtc27, niosHD, sabuasal, simoncook, johnrusso, rbar, hiraditya, jgravelle-google, sbc100, dschuff.
Herald added a project: All.
samparker requested review of this revision.
Herald added subscribers: pcwang-thead, MaskRay, aheejin.
Herald added a project: LLVM.

If a chain of two selects share a true/false value and are controlled by two setcc nodes, that are never both true, we can fold away one of the selects. The setcc check is currently limited to seteq with a constant. So, the following

  (select (setcc X, const0, eq), Y,
    (select (setcc X, const1, eq), Z, Y))

      

Can be combined to:

  select (setcc X, const1, eq) Z, Y


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D142535

Files:
  llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
  llvm/test/CodeGen/RISCV/fpclamptosat_vec.ll
  llvm/test/CodeGen/WebAssembly/fpclamptosat.ll
  llvm/test/CodeGen/WebAssembly/fpclamptosat_vec.ll
  llvm/test/CodeGen/X86/fpclamptosat_vec.ll

-------------- next part --------------
A non-text attachment was scrubbed...
Name: D142535.492082.patch
Type: text/x-patch
Size: 11899 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20230125/a71218b9/attachment-0001.bin>