[MatMul] Make MatMul detection independent of internal isl representations.
The pattern recognition for MatMul is restrictive.
The number of "disjuncts" in the isl_map containing constraint
information was previously required to be 1
(as per isl_*_coalesce - which should ideally produce a domain map with
a single disjunct, but does not under some circumstances).
This was changed and made more flexible.
Contributed-by: Annanay Agarwal <cs14btech11001@iith.ac.in>
Differential Revision: https://reviews.llvm.org/D36460
git-svn-id: https://llvm.org/svn/llvm-project/polly/trunk@311302 91177308-0d34-0410-b5e6-96231b3b80d8