This CL replaces the equirecursive type system for wasm-gc with the
isorecursive hybrid type system presented here:
https://github.com/WebAssembly/gc/issues/257.
In broad strokes, this includes the following changes:
- In the module decoder, remove equirecursive types. Implement recursive
type groups, subtype definitions, and function/struct/array
definitions. Treat nominal modules as syntactic sugar of an
isorecursive module, where all types belong in the same recursive
group.
- Remove rtt.sub and all related infrastructure.
- Change subtyping to work with explicit supertypes only.
- Add ValidSubtypeDefinition in subtyping, to check that subtype
declarations are valid during decoding.
- Remove the subtyping cache.
- Add support for functions to have specific signature index in
WasmModuleBuilder and in test-gc.cc.
- Adapt tests.
Current restrictions:
- Recursive groups are not stored beyond decoding.
- Type canonicalization is not implemented. No tests relying on types
being considered identical post-canonicalization.
- No cross-module subtyping is possible. Tests relying on cross-module
subtyping have been commented out.
Bug: v8:7748
Change-Id: I69fd04ecc5611f6230c95d5c89d1c520163fffae
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3416239
Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Commit-Queue: Manos Koukoutos <manoskouk@chromium.org>
Cr-Commit-Position: refs/heads/main@{#78816}
Design doc: bit.ly/36MfD6Y
We introduce simplified operators LoadImmutableFromObject and
InitializeImmutableInObject. These are lowered to Loads and Stores like
LoadFromObject and StoreToObject.
We split CsaLoadElimination::AbstractState in two HalfStates,
which represent the mutable and immutable component of the state.
Immutable operators in the effect chain modify the immutable half-state,
and plain operators modify the mutable half-state. The immutable part is
maintained through write effects and loop headers. Immutable
initializations do not lookup and kill previous overlapping stores,
assuming each offset cannot be initialized more than once.
Bug: v8:11510
Change-Id: I0f5feca3354fdd3bdc1f511cc5214ec51e1407ad
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3268728
Reviewed-by: Nico Hartmann <nicohartmann@chromium.org>
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Commit-Queue: Manos Koukoutos <manoskouk@chromium.org>
Cr-Commit-Position: refs/heads/main@{#78325}
