Alex Zinenko cb3ecb5291 Overhaul the SDBM expression kind hierarchy ... Swap the allowed nesting of sum and diff expressions: now a diff expression can contain a sum expression, but only on the left hand side. A difference of two expressions sum must be canonicalized by grouping their constant terms in a single expression. This change of sturcture became possible thanks to the introduction of the "direct" super-kind. It is necessary to enable support of sum expressions on the left hand side of the stripe expression. SDBM expressions are now grouped into the following structure - expression - varying - direct - sum <- (term, constant) - term - symbol - dimension - stripe <- (term, constant) - negation <- (direct) - difference <- (direct, term) - constant The notation <- (...) denotes the types of subexpressions a compound expression can combine. PiperOrigin-RevId: 269337222		2019-09-16 08:16:06 -07:00
mlir	Overhaul the SDBM expression kind hierarchy	2019-09-16 08:16:06 -07:00