[flang][OpenMP] Upgrade support for Flush, Depend, Taskwait construct to OpenMP 5.0

[kiranktp]

Summary

This patch enhances parser support for below OpenMP constructs to OpenMP 5.0.
Depend Clause
Flush Construct
Taskwait Construct

The patch includes code changes and testcase modifications.

[sscalpone]

@kiranktp Hi Kiran, Will any of the proposed OpenMP 5.1 features affect these features?

Thanks!

[kiranchandramohan]

We have tracking per OpenMP directives/constructs in a google docs spreadsheet (link below). This spreadsheet was already being used for the OpenMP IRBuilder work. So we just added additional sheets to cover Parsing, Semantics, Lowering to OpenMP MLIR, OpenMP Ops spec, Lowering to LLVM IR. There is also a master sheet. The new OpenMP 5.0 constructs are the ones in bold (updated in master, parsing sheets), the ones which have additional clauses in OpenMP 5.0 are listed in the third column (parsing sheet only).
https://docs.google.com/spreadsheets/d/1FvHPuSkGbl4mQZRAwCIndvQx9dQboffiD-xD0oqxgU0/edit#gid=0

[sscalpone]

In D81848#2093203, @kiranchandramohan wrote:

We have tracking per OpenMP directives/constructs in a google docs spreadsheet (link below).

Great! I have amended my questions.

[kiranktp]

In D81848#2093052, @sscalpone wrote:

@kiranktp Hi Kiran, Will any of the proposed OpenMP 5.1 features affect these features?

Thanks!

Hi Steve,
I referred to OpenMP 5.1 standard as well. Among these 3 constructs, only Depend clause has a new dependence type addition to it. I have taken care of that as well.

[kiranchandramohan]

@kiranktp Can we have separate patches for Flush, depend & iterator, taskwait? It will be easier to review.

flang/test/Semantics/omp-clause-validity01.f90

457

Can this and the one below be in lowercase?

[kiranktp]

In D81848#2096663, @kiranchandramohan wrote:

@kiranktp Can we have separate patches for Flush, depend & iterator, taskwait? It will be easier to review.

Sure. I will divide this into 3 separate patches. I will abandon this review request.
I will take care of other review comments as well.