r-indexing without backward searching

Suppose we are given a text T of length n and a straight-line program for T with g rules. Let r̅ be the number of runs in the Burrows-Wheeler Transform of the reverse of T. We can index T in O (r̅ + g) space such that, given a pattern P and constant-time access to the Karp-Rabin hashes of the substrings of P and the reverse of P, we can find the maximal exact matches of P with respect to T correctly with high probability and using O (log n) time for each edge we would descend in the suffix tree of T while finding those matches.