[all-commits] [llvm/llvm-project] 0b45c2: [SelectionDAG] rot(x, y) --> x iff ComputeNumSignB...

[Simon Pilgrim via All-commits]

  Branch: refs/heads/master
  Home:   https://github.com/llvm/llvm-project
  Commit: 0b45c2264a430b9f40e3cfaf0704050c2101b830
      https://github.com/llvm/llvm-project/commit/0b45c2264a430b9f40e3cfaf0704050c2101b830
  Author: Simon Pilgrim <llvm-dev at redking.me.uk>
  Date:   2020-01-24 (Fri, 24 Jan 2020)

  Changed paths:
    M llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
    M llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
    M llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
    M llvm/test/CodeGen/X86/rotate_vec.ll
    M llvm/test/CodeGen/X86/sdiv_fix.ll

  Log Message:
  -----------
  [SelectionDAG] rot(x, y) --> x iff ComputeNumSignBits(x) == BitWidth(x)

Rotating an 0/-1 value by any amount will always result in the same 0/-1 value