Delinearization of expressions that contain array size parameters

This allows us to delinerize code such as:

  A[][n]

  for (i
    for (j
      A[i][n-j-1] = ...

which would previously have been delinearize to an access A[i+1][-j-1].

To recover the correct access we apply the piecewise expression:

  { A[i][j] -> A[i-1][i+N]: i < 0; A[i][j] -> A[i][i]: i >= 0}

This approach generalizes to higher dimensions.

llvm-svn: 233566