And everything else.
This is a big (important) change; it addresses one of the greatest
pains of the system.
Keeps were added during the DSL rewrite (to support symbols and such)
to work around the issue that there was no symbol-driven map; it
allowed symbols to persist disjoint from the `__yield' dependency
graph so that they could be mapped back and used by external systems.
The problem with that is that it's both messy (coupling the concept of
external dependencies with the actual code) and difficult to work
with. It had a huge performance impact on the linker for two reasons:
- Checking whether a package had already been seen and importing the
keeps on first visit was expensive because of tree searching and
manipulation; and
- _every_ keep was imported and processed by the linker, even if it
wouldn't end up being used by a particular program.
The later especially had huge performance impacts on the entire
system.
The entire dependency graph is now map-driven, with the exception of
the implicit `__yield' (which will eventually be moved into the map as
well and the magic `lv:yield' removed in favor of a template).
Performance-wise: our largest program ("dwelling") has many thousands
of symbols and the largest package imported the majority of them, many
of them unneeded, as the result of @keep subgraphs. Compilation of
the largest package within that (for the UI) took about a minute and a
half and ate up ~6GiB of RAM, for what really is a trivial task of
resolving externs, some basic symbol processing, a topological sort,
and ordering code fragments.
After this change, it takes ~15s and less than 2GiB of RAM. Still a
lot---and more improvements can be made---but much, much better.
@keep and friends was left in rater.xsd so that nothing breaks while
code is cleaned up; it'll be removed in the future.
* src/current/compiler/linker.xsl: Remove @keep support.
* src/current/dot/attr-keep.xsl: Remove now-unneeded template.
* src/current/dot/defnode.xsl: Remove @keep and related.
* src/current/include/preproc/eligclass.xsl: Remove @keep and related.
* src/current/include/preproc/expand.xsl: Remove @keep and related.
* src/current/include/preproc/macros.xsl: Remove @keep and related.
* src/current/include/preproc/symtable.xsl: Remove @keep and related.
* src/current/rater.xsd: Add TODO to remove @keep and friends.
Mike Gerwitz
Mike Gerwitz