[PATCH] D96399: [X86][CodeGenPrepare] Try to reuse IV's incremented value instead of adding the offset

[Juneyoung Lee via Phabricator via llvm-commits]

aqjune added a comment.

The change from the previous output to the new output looks valid to me.

  $ ./build/alive-tv D96399.srctgt.ll -disable-undef-input
  
  ----------------------------------------
  define * @src(* %p, i64 %idx) {
  %0:
    %addr1 = mul i64 %idx, 4
    %ptr = gep * %p, 1 x i64 %addr1
    %ptr2 = gep * %ptr, 1 x i64 -4
    ret * %ptr2
  }
  =>
  define * @tgt(* %p, i64 %idx) {
  %0:
    %res = usub_overflow {i64, i1, i24} %idx, 1
    %sub = extractvalue {i64, i1, i24} %res, 0
    %addr2 = mul i64 %sub, 4
    %ptr2 = gep * %p, 1 x i64 %addr2
    ret * %ptr2
  }
  Transformation seems to be correct!


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  https://reviews.llvm.org/D96399/new/

https://reviews.llvm.org/D96399