- A spot fix in SILGen for reabstracting the result of a downcast, which fixes checked casts to function types.
- Associate the layout information in type metadata records with the most abstract representation of the type. This is the correct thing to do in cases where we need the metadata as a tag for an opaque value--if we store a value in an Any, or pass it as an unconstrained generic parameter, we must maximally reabstract it. This fixes the value semantics of existentials containing trivial metatypes.
- To ensure that we get runtime layout of structs and enums correct when they contain reabstractable types, introduce a "metadata for layout" concept, which doesn't need to describe the canonical metadata for the type, but only needs to describe a type with equivalent layout and value semantics. This is a correctness fix that allows us to correctly lay out generic types containing dependent tuples and functions, and although we don't really take advantage of it here, it's also a potential runtime performance win down the road, because we could potentially produce direct metadata for a primitive type that's layout-equivalent with a runtime-instantiated type. To aid in type safety here, push SILType deeper into IRGen in places where we potentially care about specific representations of types.
- Finally, fix an inconsistency between the runtime and IRGen's concept of what spare bits unmanaged references and thick metatypes have.
Together, these fixes address rdar://problem/16406907, rdar://problem/17822208, rdar://problem/18189508, and likely many other related issues, and also fixes crash suite cases 012 and 024.
Swift SVN r21963
unexpected forematter from the superclass.
This requires a pretty substantial shift in the
generic-metadata allocation/initialization dance
because (1) we can't allocate class metadata without
knowing what the superclass is and (2) the offset
from the metadata cache entry to the address point is
no longer determined solely by the metadata pattern.
While I'm making invasive changes to metadata, fix
two race conditions in metadata creation. The first
is that we need to ensure that only one thread succeeds
at lazily creating a generic-metadata cache. The second
is that we need to ensure that only one thread actually
attempts to create a particular metadata; any others
should block until the metadata is successfully built.
This commit finishes rdar://17776354. LLDB will
need to adjust to the runtime-private metadata layout
changes.
Swift SVN r20537
