[PATCH] D73215: [MIPS GlobalISel] Select count trailing zeros

[Petar Avramovic via Phabricator via llvm-commits]

Petar.Avramovic created this revision.
Petar.Avramovic added reviewers: atanasyan, petarj.
Herald added subscribers: llvm-commits, volkan, jrtc27, hiraditya, arichardson, rovka, sdardis.
Herald added a project: LLVM.

llvm.cttz.<type> intrinsic has additional i1 argument is_zero_undef,
it tells whether zero as the first argument produces a defined result.
G_CTTZ is generated from llvm.cttz.<type> (<type> <src>, i1 false)
intrinsics, clang generates these intrinsics from __builtin_ctz and
__builtin_ctzll.
G_CTTZ_ZERO_UNDEF comes from llvm.cttz.<type> (<type> <src>, i1 true).
Clang generates such intrinsics as parts of expansion of __builtin_ffs
and __builtin_ffsll. It is also traditionally part of and many 
algorithms that are now predicated on avoiding zero-value inputs.

Add narrow scalar (algorithm uses G_CTTZ_ZERO_UNDEF) for G_CTTZ.
Lower G_CTTZ and G_CTTZ_ZERO_UNDEF for MIPS32.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D73215

Files:
  llvm/include/llvm/CodeGen/GlobalISel/LegalizerHelper.h
  llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
  llvm/lib/Target/Mips/MipsLegalizerInfo.cpp
  llvm/test/CodeGen/Mips/GlobalISel/legalizer/cttz.mir
  llvm/test/CodeGen/Mips/GlobalISel/llvm-ir/cttz.ll

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