As a first step in adding clause support for OpenACC to Semantic
Analysis, this patch adds the 'base' AST nodes required for clauses.
This patch has no functional effect at the moment, but followup patches
will add the semantic analysis of clauses (plus individual clauses).
This patch Implements AST node creation and appertainment enforcement
for 'parallel', as well as changes the 'not implemented' messages to be
more specific. It does not deal with clauses/clause legality, nor a few
of the other rules from the standard, but this gets us most of the way
for a framework for future construct implementation.
'serial', 'parallel', and 'kernel' constructs are all considered
'Compute' constructs. This patch creates the AST type, plus the required
infrastructure for such a type, plus some base types that will be useful
in the future for breaking this up.
The only difference between the three is the 'kind'( plus some minor
clause legalization rules, but those can be differentiated easily
enough), so rather than representing them as separate AST nodes, it
seems
to make sense to make them the same.
Additionally, no clause AST functionality is being implemented yet, as
that fits better in a separate patch, and this is enough to get the
'naked' constructs implemented.
This is otherwise an 'NFC' patch, as it doesn't alter execution at all,
so there aren't any tests. I did this to break up the review workload
and to get feedback on the layout.
