Remove dmap and deprecated distributions

[bradcray]

This PR removes the deprecated symbols related to distributions, layouts, and the dmap type. Specifically, it removes:

• the dmap type
• distributions that had previously been implemented as classes and been deprecated (e.g., Block was deprecated in favor of blockDist)
• the deprecated LayoutCS module
• a deprecated config const in BlockDist.chpl, disableAliasedBulkTransfer.

In more detail:

• I simply removed all deprecated distributions (BlockCyclic, Block, Cyclic, DimensionalDist2D, Hashed, Private, Replicated, Stencil), associated comments, and the aforementioned config

• Similarly, I removed the LayoutCS module and all references to it

• The dmap type was still used to create the logical singleton defaultDist, as it still provides the value-based wrapping around the DefaultDist class. Ultimately, DefaultDist should be rewritten to be a record, but here I took the simpler and more minimal approach of renaming the dmap type to chpl_dmap, effectively making it an internal symbol. Beyond updating defaultDist's use of it, this also required updating Dyno to recognize the new name, as it is currently special-cased there.

• I removed a pair of helper routines in ChapelArray.chpl that existed merely to keep the dmap type working while deprecated.

• I removed tests in the test/deprecated directory related to these features

• Interestingly, the removal of disableAliasedBulkTransfer caused BlockDist.chpl to go from being a non-dead module to a dead one; presumably, the presence of a config in a module prevents it from being dead-code eliminated since it represents a (potential) user-facing feature. This required updates to tests that were sensitive to module init/deinit order and counts of dead modules, such as:

  • test/modules/sungeun/init/printModuleInitOrder.chpl
  • test/modules/vass/deinit-order-modules.verbose.chpl
  • test/optimizations/deadCodeElimination/elliot/countDeadModules.chpl

• In SparseBlockDist.getDefaultSparseDist(), I changed a case that relied on dmap into a halt() because I believe it was only used for (old, now removed) class-based distributions, so should no longer be hit in practice. In essence, the halt() serves as an always-on assertion.

• I added a pair of records to wrap class-based distributions to DSIUtil.chpl, similar to how chpl_PrivatizedDistHelper did this for the Block, Cyclic, etc. classes when they were being converted into records. One is for wrapping a rectangular distribution, the other for associative (chpl__rectLayoutHelper and chpl__assocLayoutHelper, respectively). At present, these are only used by tests in the test system that created custom distribution classes, though if we had class-based layouts, they could be used there as well to convert to record-based implementations. That said, if writing a new record-based distribution today, it should simply be written as a record, which would obviate the need for wrapping a class. Put another way, this is just a trick to minimize the amount of code that needs to be rewritten; with more effort, the tests that create custom distributions could/should be rewritten to simply use a record type as well.

• Tests with custom class-based distributions that required updates to use record-based distributions (and leverage the above helpers) included:

  • MyDist => myDist in test/arrays/dmapped-new-error-class.chpl
  • MyDist => myDist in test/distributions/bradc/wrongDomForDist/*.chpl
  • GlobalDistribution => globalDistribution in test/domains/vass/no-dom-field-error.chpl
  • AccumStencil => accumStencil in test/studies/comd/elegant/arrayOfStructs/util/*.chpl

• I updated tests or code patterns that relied on new dmap(new DefaultDist()) to simply use defaultDist instead, such as in test/unstable/dmapped-sparse.chpl and test/users/engin/sparse_bulk/sparseBulkBoundsCheck.chpl

• I also removed test/distributions/diten/domainMethodNewDist.chpl which seemed to serve no particular purpose in a dmap-less world

[jabraham17]

Looks good!

Just noting that I still see mentions of dmap in the docs

• doc/rst/technotes/dsi.rst
• doc/rst/language/spec/domain-maps.rst

And those should probably be updated as well

[jabraham17]

This error message is now incorrect, there is no dmap a user can use

[bradcray]

Also a good catch! I'm going to remove this test (in addition to removing the compiler logic that printed new dmap(), as it was specific to a time when some, but not all, distributions were converted to classes.

While here, I also updated the error message to print the actual distribution type rather than <DistName> which seems like an obvious/simple improvement.