This change is analogous to the TypeInfo cache in TypeLowering, which does the
exact same thing. In LLDB the ExternalTypeInfoProvider may gain new information
throughout the life of a process, and more importantly, it may return
context-dependent results.
rdar://122432501
Implement computeUnalignedFieldStartOffset as an alternative way to
finding out the start of the fields that belong to the instance when
reading the field's start from binary is not possible (for example,
embedded Swift doesn't emit any reflection metadata on the binary).
Currently, TypeRefBuilder knows how to parse type descriptors from
reflection metadata. We aim to store the same information that lives
in type descriptors externally, as an effort to support embedded Swift
debugging. In order to take advantage of all of the existing type
information parsing code that exists today in remote mirrors, add an
interface for external lookup of type descriptors, and replace all the
usages of type descriptors with their generic counterpart (this patch
only adds support for builtin descriptors, but follow up patches will
add support for other descriptor types).
Separately track text and data segments for ownsAddress. We were previously tracking one range per image, encompassing the range from the start of the image through the end of the data segment. This ends up including a lot of unwanted address space if the two aren't adjacent, as is the case for libraries in the shared cache on Darwin.
This makes metadataIsActor a lot more reliable, as it was previously identifying a lot of garbage as actor metadata due to the supposed descriptor pointer falling in this range.
rdar://113417637
ReflectionContext::allocationMetadataPointer() was reading the
metadata pointer from a wrong offset because of the out-of-sync struct
layouts and dump-generic-metadata was not working correctly.
This change resync's the layouts and adds a static_assert to verify
that the offsets match between GenericMetadataCacheEntry and
GenericCacheEntry.
