enhancements to Fusion/Fracture Specification Language (FSL)

[jeffnye-gh]

Recording the requests for enhancements to FSL that came up during the review:

From Arup: Is there a way to fuse one or more classes of instruction with other instructions? For example, is there a way to define a logical immediate class of instructions for andi, ori, xori and define a sequence in terms of that class, instead of individual instructions?

1. Add support in the syntax/parser for composition in expressing sequences. Add syntax for expressing the composition and for combining them from other sequences. Add the syntax description, add support in the parser and back end.

From Arup: If we do not anticipate having more than one sequence, constraint and conversion clause per transform, wondering if we need to specify the arguments iop1, seq1, cons1 in the agument lists for every transform. Instead, is it okay to make them implicit?

2. Relax the requirement for argument lists in clauses in transforms using the encapsulated style. Change the syntax description, show examples, support in the parser and backend