Implements memory access through the `Pointer`, `Struct` and `Union` FFI
types. `Pointer` supports `fromAddress`, `address`, `elementAt`, `cast`,
`value`, `ref` (only getter), `[]`, `[]=` (not for structs and unions),
`==` and `hashCode`. Structs and unions support getters and setters for
their members.
`Pointer`, `Struct` and `Union` are all represented as `i32`, both
internally and in imports and exports. They currently don't have any
boxed representation, which means they can't be nullable (a `Pointer`
can still contain `nullptr` - the C null) and can't be assigned to
supertypes (i.e. `Object`, `dynamic`, type variables), stored in
containers nor passed as arguments or return values of local functions
or function expressions. To pass an FFI value in these situations, box
it manually by storing it in a field.
For the FFI integer types, only the explicitly sized versions (e.g.
`Int8`, `Uint32`) are supported.
Whenever the feature is used, the module will import a memory by the
name "ffi.memory", which will be accessed by the operations.
This also adds an optional commandline argument to `run_wasm.js` to
specify the module containing the FFI code. When such a module is
specified, it will be instantiated first, and its exports will appear as
imports to the Dart module under the "ffi" module name.
Change-Id: Ie55b072056f972b42db6b75e0c676944bbe88c1a
Cq-Include-Trybots: luci.dart.try:vm-kernel-precomp-linux-debug-x64-try
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/237686
Reviewed-by: Joshua Litt <joshualitt@google.com>
Reviewed-by: Johnni Winther <johnniwinther@google.com>
Commit-Queue: Aske Simon Christensen <askesc@google.com>
Aske Simon Christensen
c2339ee782