commit d7a39788d4fc69f64a23593242a542cbaa4bc08d
author Ömer Sinan Ağacan <omersa@google.com> Thu Sep 05 11:24:10 2024 +0000
committer Ömer Ağacan <omersa@google.com> Thu Sep 05 11:24:10 2024 +0000
tree 0824322c6ef9a7171d4da156fad6c07bba27d418
parent 0e620b27a037fd46e5ddbfc53fa6dec941fa3372

[dart2wasm] Box `Pointer` values obtained from FFI calls

Currently `Pointer` argument and return types of `FfiNative` functions
are translated to Wasm as `i32`.

This causes problems when we need to box those `i32` values as we don't
track which Dart types Wasm types come from when converting a Dart type
like `Pointer` to a Wasm type like `i32`.

Currently this works somewhat accidentally. All `i32`s are boxed as
`BoxedBool`, including `i32`s that represent `Pointer`s.

This breaks when we need to get the type parameter of a `Pointer` (e.g.
in a `is` or `as` check), but more importantly it means that we can't
cache boxed `true` and `false` values and return those cached values
when converting an `i32` to a boxed type as we don't know whether the
`i32` represents a bool or pointer.

Ideally we would have some kind of intermediate layer between
`wasm_builder` and dart2wasm that allows types like "a Wasm i32
representing an unboxed T" (for some T).

Alternatively we could attach extra information to `ValueType`s, for
example using expandos or maybe by adding a `dynamic` field to the base
class.

However it's unclear whether it's worth doing a major refactoring, when
a simpler alternative exist: we box `Pointer` values obtained from an
import in the Dart wrapper for the imported function.

VM already boxes `Pointer`s, so the performance should be acceptable.

This CL implements this simpler alternative of boxing `Pointer` values.

Tested: web/wasm/ffi/ffi_native_test updated.
Change-Id: I02e5c07fdb021a7b51ed5db2a44123b1608c9aad
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/383325
Reviewed-by: Martin Kustermann <kustermann@google.com>
Commit-Queue: Ömer Ağacan <omersa@google.com>