[AST] Tail-allocate GenericEnvironment's archetypes-to-interface types mapping #6014
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…s mapping Store the archetype-to-interface-type mapping (which is used to map *out* of a generic environment) is a tail-allocated array of (archetype, generic type parameter) pairs. This array is built up lazily, as we compute the context types for generic parameters. Searching in this array is linear while it is being constructed. Once it is complete, it is sorted so that future searches are logarithmic. Aside from the space savings of not having a DenseMap lying around, this means we no longer need to register a destructor of a GenericEnvironment with the ASTContext, which saves us tear-down time.
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@swift-ci please smoke test and merge |
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Oh hey. :-) Awful thought: is 65536 mappings enough? |
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That's a fine upper limit on the number of generic parameters in a contezt |
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"64K parameters ought to be enough for anyone" |
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Store the archetype-to-interface-type mapping (which is used to map
out of a generic environment) is a tail-allocated array of
(archetype, generic type parameter) pairs. This array is built up
lazily, as we compute the context types for generic parameters.
Searching in this array is linear while it is being constructed. Once
it is complete, it is sorted so that future searches are logarithmic.
Aside from the space savings of not having a DenseMap lying around,
this means we no longer need to register a destructor of a
GenericEnvironment with the ASTContext, which saves us tear-down
time.
@jrose-apple happy now?