I'm not sure if this is the right place for this to happen, and
it should become obsolete when comptime mutation is rewritten
and the remaining legacy value tags are remove, so keeping this
as a separate revertable commit.
Previously, there were types and values for inferred allocations and a
lot of special-case handling. Now, instead, the special casing is
limited to AIR instructions for these use cases.
Instead of storing data in Value payloads, the data is now stored in AIR
instruction data as well as the previously `void` value type of the
`unresolved_inferred_allocs` hash map.
Store `InternPool.Index` as the key instead which means that an AIR
instruction no longer needs to be burned to store the type, and also
that we can use AutoArrayHashMap instead of an ArrayList, which avoids
storing duplicates into the set, potentially saving CPU time.
This allows some code (like struct initializers) to use interned types
while other code (such as comptime mutation) continues to use legacy
types.
With these changes, an `zig build-obj empty.zig` gets to a crash on
missing interned error union types.
One change worth noting in this commit is that `module.global_error_set`
is no longer kept strictly up-to-date. The previous code reserved
integer error values when dealing with error set types, but this is no
longer needed because the integer values are not needed for semantic
analysis unless `@errorToInt` or `@intToError` are used and therefore
may be assigned lazily.
Also I moved `anyframe` from being represented by `SimpleType` to being
represented by the `none` tag of `anyframe_type` because most code wants
to handle these two types together.
Anonymous structs and anonymous tuples can be stored via a
only_possible_value tag because their type encodings, by definition,
will have every value specified, which can be used to populate the
fields slice in `Key.Aggregate`.
Also fix `isTupleOrAnonStruct`.
I'm seeing a new assertion trip: the call to `enumTagFieldIndex` in the
implementation of `@Type` is attempting to query the field index of an
union's enum tag, but the type of the enum tag value provided is not the
same as the union's tag type. Most likely this is a problem with type
coercion, since values are now typed.
Another problem is that I added some hacks in std.builtin because I
didn't see any convenient way to access them from Sema. That should
definitely be cleaned up before merging this branch.
Unlike unions and structs, enums are actually *encoded* into the
InternPool directly, rather than using the SegmentedList trick. This
results in them being quite compact, and greatly improved the ergonomics
of using enum types throughout the compiler.
It did however require introducing a new concept to the InternPool which
is an "incomplete" item - something that is added to gain a permanent
Index, but which is then mutated in place. This was necessary because
enum tag values and tag types may reference the namespaces created by
the enum itself, which required constructing the namespace, decl, and
calling analyzeDecl on the decl, which required the decl value, which
required the enum type, which required an InternPool index to be
assigned and for it to be meaningful.
The API for updating enums in place turned out to be quite slick and
efficient - the methods directly populate pre-allocated arrays and
return the information necessary to output the same compilation errors
as before.
This introduces a string table into InternPool as well as a curious new
field called `maps` which is an array list of array hash maps with
void/void key/value.
Some types such as enums, structs, and unions need to store mappings
from field names to field index, or value to field index. In such cases,
they will store the underlying field names and values directly, relying
on one of these maps, stored separately, to provide lookup.
This allows the InternPool to be serialized via simple array copies,
omitting all the maps, which are only used for optimizing lookup based
on field name or field value.
When the InternPool is deserialized it can be loaded via simple array
copies, and then as a post-processing step the field name maps can be
generated as extra metadata that is tacked on.
This commit provides two encodings for enums - one when the integer tag
type is explicitly provided and one when it is not. This is simpler than
the previous setup, which has three encodings.
Previous sizes:
* EnumSimple: 40 bytes + 16 bytes per field
* EnumNumbered: 80 bytes + 24 bytes per field
* EnumFull: 184 bytes + 24 bytes per field
Sizes after this commit:
* type_enum_explicit: 24 bytes + 8 bytes per field
* type_enum_auto: 16 bytes + 4 bytes per field
This is handy if you have a u32 and want a u32 and don't want to take a
detour through many layers of abstraction elsewhere in the std.hash
namespace.
Copied from https://nullprogram.com/blog/2018/07/31/
