[PATCH] D45872: [DA] Enable -da-delinearize by default

[Hal Finkel via Phabricator via llvm-commits]

hfinkel added a comment.

In https://reviews.llvm.org/D45872#1073553, @grosser wrote:

> We probably need to also add code that ensures that the arrays that result from delinearization remain within bounds. Without this code, the resulting checks are likely incorrect.


I agree. To be clear, I think that this means addressing the FIXME in the code:

  // The delinearization transforms a single-subscript MIV dependence test into
  // a multi-subscript SIV dependence test that is easier to compute. So we
  // resize Pair to contain as many pairs of subscripts as the delinearization
  // has found, and then initialize the pairs following the delinearization.
  Pair.resize(size);
  for (int i = 0; i < size; ++i) {
    Pair[i].Src = SrcSubscripts[i];
    Pair[i].Dst = DstSubscripts[i];
    unifySubscriptType(&Pair[i]);
  
    // FIXME: we should record the bounds SrcSizes[i] and DstSizes[i] that the
    // delinearization has found, and add these constraints to the dependence
    // check to avoid memory accesses overflow from one dimension into another.
    // This is related to the problem of determining the existence of data
    // dependences in array accesses using a different number of subscripts: in
    // C one can access an array A[100][100]; as A[0][9999], *A[9999], etc.
  }

I'd assumed that is why delinearization is disabled by default.


https://reviews.llvm.org/D45872