[PATCH] D113526: [InstCombine] Generalize complex OR patterns to AND

[Stanislav Mekhanoshin via Phabricator via llvm-commits]

rampitec created this revision.
rampitec added reviewers: spatel, lebedev.ri.
Herald added a subscriber: hiraditya.
rampitec requested review of this revision.
Herald added a project: LLVM.

For every pattern with only NOT, OR, and AND operations there is
always a symmetrical pattern with AND and OR swapped.

This adds 2 transformations:

  (~(a & b) | c) & (~(a & c) | b) --> ~((b ^ c) & a)
  (~(a & b) | c) & ~(a & c) --> ~((b | c) & a)



  ----------------------------------------
  define i4 @src(i4 %a, i4 %b, i4 %c) {
  %0:
    %and1 = and i4 %b, %a
    %not1 = xor i4 %and1, 15
    %and2 = and i4 %a, %c
    %not2 = xor i4 %and2, 15
    %or = or i4 %not2, %b
    %r = and i4 %or, %not1
    ret i4 %r
  }
  =>
  define i4 @tgt(i4 %a, i4 %b, i4 %c) {
  %0:
    %or = or i4 %b, %c
    %and = and i4 %or, %a
    %r = xor i4 %and, 15
    ret i4 %r
  }
  Transformation seems to be correct!
  
  ----------------------------------------
  define i4 @src(i4 %a, i4 %b, i4 %c) {
  %0:
    %and1 = and i4 %a, %b
    %not1 = xor i4 %and1, 15
    %or1 = or i4 %not1, %c
    %and2 = and i4 %a, %c
    %not2 = xor i4 %and2, 15
    %or2 = or i4 %not2, %b
    %and3 = and i4 %or1, %or2
    ret i4 %and3
  }
  =>
  define i4 @tgt(i4 %a, i4 %b, i4 %c) {
  %0:
    %xor = xor i4 %b, %c
    %and = and i4 %xor, %a
    %not = xor i4 %and, 15
    ret i4 %not
  }
  Transformation seems to be correct!


https://reviews.llvm.org/D113526

Files:
  llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
  llvm/test/Transforms/InstCombine/and-xor-or.ll

-------------- next part --------------
A non-text attachment was scrubbed...
Name: D113526.386001.patch
Type: text/x-patch
Size: 24959 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20211110/e302bcba/attachment.bin>