wasmtime_environ/component/

translate.rs

use crate::Abi;
use crate::component::dfg::AbstractInstantiations;
use crate::component::*;
use crate::prelude::*;
use crate::{
    DefinedGlobalIndex, DefinedMemoryIndex, DefinedTableIndex, EngineOrModuleTypeIndex,
    EntityIndex, FactInlineIntrinsic, FuncKey, KnownEntity, KnownGlobal, ModuleEnvironment,
    ModuleInternedTypeIndex, ModuleTranslation, ModuleTypesBuilder, PrimaryMap, ScopeVec, TagIndex,
    Tunables, TypeConvert, WasmHeapType, WasmResult, WasmValType,
};
use core::str::FromStr;
use cranelift_entity::{EntityRef, SecondaryMap};
use indexmap::IndexMap;
use std::collections::{HashMap, HashSet};
use std::mem;
use wasmparser::component_types::{
    AliasableResourceId, ComponentCoreModuleTypeId, ComponentDefinedTypeId, ComponentEntityType,
    ComponentFuncTypeId, ComponentInstanceTypeId, ComponentValType,
};
use wasmparser::types::Types;
use wasmparser::{Chunk, ComponentExternName, Encoding, Parser, Payload, Validator};

mod adapt;
pub use self::adapt::*;
mod inline;

/// Structure used to translate a component and parse it.
pub struct Translator<'a, 'data> {
    /// The current component being translated.
    ///
    /// This will get swapped out as translation traverses the body of a
    /// component and a sub-component is entered or left.
    result: Translation<'data>,

    /// Current state of parsing a binary component. Note that like `result`
    /// this will change as the component is traversed.
    parser: Parser,

    /// Stack of lexical scopes that are in-progress but not finished yet.
    ///
    /// This is pushed to whenever a component is entered and popped from
    /// whenever a component is left. Each lexical scope also contains
    /// information about the variables that it is currently required to close
    /// over which is threaded into the current in-progress translation of
    /// the sub-component which pushed a scope here.
    lexical_scopes: Vec<LexicalScope<'data>>,

    /// The validator in use to verify that the raw input binary is a valid
    /// component.
    validator: &'a mut Validator,

    /// Type information shared for the entire component.
    ///
    /// This builder is also used for all core wasm modules found to intern
    /// signatures across all modules.
    types: PreInliningComponentTypes<'a>,

    /// The compiler configuration provided by the embedder.
    tunables: &'a Tunables,

    /// Auxiliary location to push generated adapter modules onto.
    scope_vec: &'data ScopeVec<u8>,

    /// Completely translated core wasm modules that have been found so far.
    ///
    /// Note that this translation only involves learning about type
    /// information and functions are not actually compiled here.
    static_modules: PrimaryMap<StaticModuleIndex, ModuleTranslation<'data>>,

    /// Completely translated components that have been found so far.
    ///
    /// As frames are popped from `lexical_scopes` their completed component
    /// will be pushed onto this list.
    static_components: PrimaryMap<StaticComponentIndex, Translation<'data>>,

    /// The top-level import name for Wasmtime's unsafe intrinsics, if any.
    unsafe_intrinsics_import: Option<&'a str>,
}

/// Representation of the syntactic scope of a component meaning where it is
/// and what its state is at in the binary format.
///
/// These scopes are pushed and popped when a sub-component starts being
/// parsed and finishes being parsed. The main purpose of this frame is to
/// have a `ClosedOverVars` field which encapsulates data that is inherited
/// from the scope specified into the component being translated just beneath
/// it.
///
/// This structure exists to implement outer aliases to components and modules.
/// When a component or module is closed over then that means it needs to be
/// inherited in a sense to the component which actually had the alias. This is
/// achieved with a deceptively simple scheme where each parent of the
/// component with the alias will inherit the component from the desired
/// location.
///
/// For example with a component structure that looks like:
///
/// ```wasm
/// (component $A
///     (core module $M)
///     (component $B
///         (component $C
///             (alias outer $A $M (core module))
///         )
///     )
/// )
/// ```
///
/// here the `C` component is closing over `M` located in the root component
/// `A`. When `C` is being translated the `lexical_scopes` field will look like
/// `[A, B]`. When the alias is encountered (for module index 0) this will
/// place a `ClosedOverModule::Local(0)` entry into the `closure_args` field of
/// `A`'s frame. This will in turn give a `ModuleUpvarIndex` which is then
/// inserted into `closure_args` in `B`'s frame. This produces yet another
/// `ModuleUpvarIndex` which is finally inserted into `C`'s module index space
/// via `LocalInitializer::AliasModuleUpvar` with the last index.
///
/// All of these upvar indices and such are interpreted in the "inline" phase
/// of compilation and not at runtime. This means that when `A` is being
/// instantiated one of its initializers will be
/// `LocalInitializer::ComponentStatic`. This starts to create `B` and the
/// variables captured for `B` are listed as local module 0, or `M`. This list
/// is then preserved in the definition of the component `B` and later reused
/// by `C` again to finally get access to the closed over component.
///
/// Effectively the scopes are managed hierarchically where a reference to an
/// outer variable automatically injects references into all parents up to
/// where the reference is. This variable scopes are the processed during
/// inlining where a component definition is a reference to the static
/// component information (`Translation`) plus closed over variables
/// (`ComponentClosure` during inlining).
struct LexicalScope<'data> {
    /// Current state of translating the `translation` below.
    parser: Parser,
    /// Current state of the component's translation as found so far.
    translation: Translation<'data>,
    /// List of captures that `translation` will need to process to create the
    /// sub-component which is directly beneath this lexical scope.
    closure_args: ClosedOverVars,
}

/// A "local" translation of a component.
///
/// This structure is used as a sort of in-progress translation of a component.
/// This is not `Component` which is the final form as consumed by Wasmtime
/// at runtime. Instead this is a fairly simple representation of a component
/// where almost everything is ordered as a list of initializers. The binary
/// format is translated to a list of initializers here which is later processed
/// during "inlining" to produce a final component with the final set of
/// initializers.
#[derive(Default)]
struct Translation<'data> {
    /// Instructions which form this component.
    ///
    /// There is one initializer for all members of each index space, and all
    /// index spaces are incrementally built here as the initializer list is
    /// processed.
    initializers: Vec<LocalInitializer<'data>>,

    /// The list of exports from this component, as pairs of names and an
    /// index into an index space of what's being exported.
    exports: IndexMap<&'data str, (ComponentItem, wasmparser::ComponentExternName<'data>)>,

    /// Type information produced by `wasmparser` for this component.
    ///
    /// This type information is available after the translation of the entire
    /// component has finished, e.g. for the `inline` pass, but beforehand this
    /// is set to `None`.
    types: Option<Types>,
}

// NB: the type information contained in `LocalInitializer` should always point
// to `wasmparser`'s type information, not Wasmtime's. Component types cannot be
// fully determined due to resources until instantiations are known which is
// tracked during the inlining phase. This means that all type information below
// is straight from `wasmparser`'s passes.
enum LocalInitializer<'data> {
    // imports
    Import(ComponentExternName<'data>, ComponentEntityType),

    // An import of an intrinsic for compile-time builtins.
    IntrinsicsImport,

    // canonical function sections
    Lower {
        func: ComponentFuncIndex,
        lower_ty: ComponentFuncTypeId,
        options: LocalCanonicalOptions,
    },
    Lift(ComponentFuncTypeId, FuncIndex, LocalCanonicalOptions),

    // resources
    Resource(AliasableResourceId, WasmValType, Option<FuncIndex>),
    ResourceNew(AliasableResourceId, ModuleInternedTypeIndex),
    ResourceRep(AliasableResourceId, ModuleInternedTypeIndex),
    ResourceDrop(AliasableResourceId, ModuleInternedTypeIndex),

    BackpressureInc {
        func: ModuleInternedTypeIndex,
    },
    BackpressureDec {
        func: ModuleInternedTypeIndex,
    },
    TaskReturn {
        result: Option<ComponentValType>,
        options: LocalCanonicalOptions,
    },
    TaskCancel {
        func: ModuleInternedTypeIndex,
    },
    WaitableSetNew {
        func: ModuleInternedTypeIndex,
    },
    WaitableSetWait {
        options: LocalCanonicalOptions,
    },
    WaitableSetPoll {
        options: LocalCanonicalOptions,
    },
    WaitableSetDrop {
        func: ModuleInternedTypeIndex,
    },
    WaitableJoin {
        func: ModuleInternedTypeIndex,
    },
    SubtaskDrop {
        func: ModuleInternedTypeIndex,
    },
    SubtaskCancel {
        func: ModuleInternedTypeIndex,
        async_: bool,
    },
    StreamNew {
        ty: ComponentDefinedTypeId,
        func: ModuleInternedTypeIndex,
    },
    StreamRead {
        ty: ComponentDefinedTypeId,
        options: LocalCanonicalOptions,
    },
    StreamWrite {
        ty: ComponentDefinedTypeId,
        options: LocalCanonicalOptions,
    },
    StreamCancelRead {
        ty: ComponentDefinedTypeId,
        func: ModuleInternedTypeIndex,
        async_: bool,
    },
    StreamCancelWrite {
        ty: ComponentDefinedTypeId,
        func: ModuleInternedTypeIndex,
        async_: bool,
    },
    StreamDropReadable {
        ty: ComponentDefinedTypeId,
        func: ModuleInternedTypeIndex,
    },
    StreamDropWritable {
        ty: ComponentDefinedTypeId,
        func: ModuleInternedTypeIndex,
    },
    FutureNew {
        ty: ComponentDefinedTypeId,
        func: ModuleInternedTypeIndex,
    },
    FutureRead {
        ty: ComponentDefinedTypeId,
        options: LocalCanonicalOptions,
    },
    FutureWrite {
        ty: ComponentDefinedTypeId,
        options: LocalCanonicalOptions,
    },
    FutureCancelRead {
        ty: ComponentDefinedTypeId,
        func: ModuleInternedTypeIndex,
        async_: bool,
    },
    FutureCancelWrite {
        ty: ComponentDefinedTypeId,
        func: ModuleInternedTypeIndex,
        async_: bool,
    },
    FutureDropReadable {
        ty: ComponentDefinedTypeId,
        func: ModuleInternedTypeIndex,
    },
    FutureDropWritable {
        ty: ComponentDefinedTypeId,
        func: ModuleInternedTypeIndex,
    },
    ErrorContextNew {
        options: LocalCanonicalOptions,
    },
    ErrorContextDebugMessage {
        options: LocalCanonicalOptions,
    },
    ErrorContextDrop {
        func: ModuleInternedTypeIndex,
    },
    ContextGet {
        func: ModuleInternedTypeIndex,
        i: u32,
    },
    ContextSet {
        func: ModuleInternedTypeIndex,
        i: u32,
    },
    ThreadIndex {
        func: ModuleInternedTypeIndex,
    },
    ThreadNewIndirect {
        func: ModuleInternedTypeIndex,
        start_func_ty: ComponentTypeIndex,
        start_func_table_index: TableIndex,
    },
    ThreadResumeLater {
        func: ModuleInternedTypeIndex,
    },
    ThreadSuspend {
        func: ModuleInternedTypeIndex,
    },
    ThreadYield {
        func: ModuleInternedTypeIndex,
    },
    ThreadSuspendThenResume {
        func: ModuleInternedTypeIndex,
    },
    ThreadYieldThenResume {
        func: ModuleInternedTypeIndex,
    },
    ThreadSuspendThenPromote {
        func: ModuleInternedTypeIndex,
    },
    ThreadYieldThenPromote {
        func: ModuleInternedTypeIndex,
    },

    // core wasm modules
    ModuleStatic(StaticModuleIndex, ComponentCoreModuleTypeId),

    // core wasm module instances
    ModuleInstantiate(ModuleIndex, HashMap<&'data str, ModuleInstanceIndex>),
    ModuleSynthetic(HashMap<&'data str, EntityIndex>),

    // components
    ComponentStatic(StaticComponentIndex, ClosedOverVars),

    // component instances
    ComponentInstantiate(
        ComponentIndex,
        HashMap<&'data str, ComponentItem>,
        ComponentInstanceTypeId,
    ),
    ComponentSynthetic(
        HashMap<&'data str, (ComponentItem, wasmparser::ComponentExternName<'data>)>,
        ComponentInstanceTypeId,
    ),

    // alias section
    AliasExportFunc(ModuleInstanceIndex, &'data str),
    AliasExportTable(ModuleInstanceIndex, &'data str),
    AliasExportGlobal(ModuleInstanceIndex, &'data str),
    AliasExportMemory(ModuleInstanceIndex, &'data str),
    AliasExportTag(ModuleInstanceIndex, &'data str),
    AliasComponentExport(ComponentInstanceIndex, &'data str),
    AliasModule(ClosedOverModule),
    AliasComponent(ClosedOverComponent),

    // export section
    Export(ComponentItem),
}

/// The "closure environment" of components themselves.
///
/// For more information see `LexicalScope`.
#[derive(Default)]
struct ClosedOverVars {
    components: PrimaryMap<ComponentUpvarIndex, ClosedOverComponent>,
    modules: PrimaryMap<ModuleUpvarIndex, ClosedOverModule>,
}

/// Description how a component is closed over when the closure variables for
/// a component are being created.
///
/// For more information see `LexicalScope`.
enum ClosedOverComponent {
    /// A closed over component is coming from the local component's index
    /// space, meaning a previously defined component is being captured.
    Local(ComponentIndex),
    /// A closed over component is coming from our own component's list of
    /// upvars. This list was passed to us by our enclosing component, which
    /// will eventually have bottomed out in closing over a `Local` component
    /// index for some parent component.
    Upvar(ComponentUpvarIndex),
}

/// Same as `ClosedOverComponent`, but for modules.
enum ClosedOverModule {
    Local(ModuleIndex),
    Upvar(ModuleUpvarIndex),
}

/// The data model for objects that are not unboxed in locals.
#[derive(Debug, Clone, Hash, Eq, PartialEq)]
pub enum LocalDataModel {
    /// Data is stored in GC objects.
    Gc {},

    /// Data is stored in a linear memory.
    LinearMemory {
        /// An optional memory definition supplied.
        memory: Option<MemoryIndex>,
        /// An optional definition of `realloc` to used.
        realloc: Option<FuncIndex>,
    },
}

/// Representation of canonical ABI options.
struct LocalCanonicalOptions {
    string_encoding: StringEncoding,
    post_return: Option<FuncIndex>,
    async_: bool,
    callback: Option<FuncIndex>,
    /// The type index of the core GC types signature.
    core_type: ModuleInternedTypeIndex,
    data_model: LocalDataModel,
}

enum Action {
    KeepGoing,
    Skip(usize),
    Done,
}

impl<'a, 'data> Translator<'a, 'data> {
    /// Creates a new translation state ready to translate a component.
    pub fn new(
        tunables: &'a Tunables,
        validator: &'a mut Validator,
        types: &'a mut ComponentTypesBuilder,
        scope_vec: &'data ScopeVec<u8>,
    ) -> Self {
        let mut parser = Parser::new(0);
        parser.set_features(*validator.features());
        Self {
            result: Translation::default(),
            tunables,
            validator,
            types: PreInliningComponentTypes::new(types),
            parser,
            lexical_scopes: Vec::new(),
            static_components: Default::default(),
            static_modules: Default::default(),
            scope_vec,
            unsafe_intrinsics_import: None,
        }
    }

    /// Expose Wasmtime's unsafe intrinsics under the given top-level import
    /// name.
    pub fn expose_unsafe_intrinsics(&mut self, name: &'a str) -> &mut Self {
        assert!(self.unsafe_intrinsics_import.is_none());
        self.unsafe_intrinsics_import = Some(name);
        self
    }

    /// Translates the binary `component`.
    ///
    /// This is the workhorse of compilation which will parse all of
    /// `component` and create type information for Wasmtime and such. The
    /// `component` does not have to be valid and it will be validated during
    /// compilation.
    ///
    /// The result of this function is a tuple of the final component's
    /// description plus a list of core wasm modules found within the
    /// component. The component's description actually erases internal
    /// components, instances, etc, as much as it can. Instead `Component`
    /// retains a flat list of initializers (no nesting) which was created
    /// as part of compilation from the nested structure of the original
    /// component.
    ///
    /// The list of core wasm modules found is provided to allow compiling
    /// modules externally in parallel. Additionally initializers in
    /// `Component` may refer to the modules in the map returned by index.
    ///
    /// # Errors
    ///
    /// This function will return an error if the `component` provided is
    /// invalid.
    pub fn translate(
        mut self,
        component: &'data [u8],
    ) -> Result<(
        ComponentTranslation,
        PrimaryMap<StaticModuleIndex, ModuleTranslation<'data>>,
    )> {
        // First up wasmparser is used to actually perform the translation and
        // validation of this component. This will produce a list of core wasm
        // modules in addition to components which are found during the
        // translation process. When doing this only a `Translation` is created
        // which is a simple representation of a component.
        let mut remaining = component;
        loop {
            let payload = match self.parser.parse(remaining, true)? {
                Chunk::Parsed { payload, consumed } => {
                    remaining = &remaining[consumed..];
                    payload
                }
                Chunk::NeedMoreData(_) => unreachable!(),
            };

            match self.translate_payload(payload, component)? {
                Action::KeepGoing => {}
                Action::Skip(n) => remaining = &remaining[n..],
                Action::Done => break,
            }
        }
        assert!(remaining.is_empty());
        assert!(self.lexical_scopes.is_empty());

        // ... after translation initially finishes the next pass is performed
        // which we're calling "inlining". This will "instantiate" the root
        // component, following nested component instantiations, creating a
        // global list of initializers along the way. This phase uses the simple
        // initializers in each component to track dataflow of host imports and
        // internal references to items throughout a component at compile-time.
        // The produce initializers in the final `Component` are intended to be
        // much simpler than the original component and more efficient for
        // Wasmtime to process at runtime as well (e.g. no string lookups as
        // most everything is done through indices instead).
        let mut component = inline::run(
            self.types.types_mut_for_inlining(),
            &self.result,
            &self.static_modules,
            &self.static_components,
        )?;

        // Now that inlining has finished and the dataflow graph is complete,
        // determine which fused adapters can skip their
        // `{enter,exit}-sync-call` calls.
        component.transparent_adapters = transparent_adapters(&component, self.types.types());

        self.partition_adapter_modules(&mut component);

        analyze_same_vmctx_imports(&component, &mut self.static_modules);

        let translation =
            component.finish(self.types.types_mut_for_inlining(), self.result.types_ref())?;

        self.analyze_imports(&translation);

        Ok((translation, self.static_modules))
    }

    /// Record everything we statically know about each module's imports.
    ///
    /// See `ModuleTranslation::known_imported_functions` and
    /// `ModuleTranslation::known_imported_globals` for how we can optimize
    /// lowering based on this information.
    fn analyze_imports(&mut self, translation: &ComponentTranslation) {
        // First, abstract interpret the initializers to create a map from each
        // static module to its abstract set of instantiations.
        let mut instantiations = SecondaryMap::<StaticModuleIndex, AbstractInstantiations>::new();
        let mut instances = StaticInstances::new();
        for init in &translation.component.initializers {
            match init {
                GlobalInitializer::InstantiateModule(instantiation, _) => match instantiation {
                    InstantiateModule::Static(module, args) => {
                        instantiations[*module].join(AbstractInstantiations::One(&*args));
                        instances.push(Some((*module, &args[..])));
                    }
                    _ => {
                        instances.push(None);
                    }
                },
                _ => continue,
            }
        }

        // Second, make sure to mark exported modules as instantiated many
        // times, since they could be linked with who-knows-what at runtime.
        for item in translation.component.export_items.values() {
            if let Export::ModuleStatic { index, .. } = item {
                instantiations[*index].join(AbstractInstantiations::Many)
            }
        }

        // Third, find the globals, memories, and tables whose identity is not
        // statically known to everything that can access them. Note that this
        // is a property of the whole component and not of a single module's
        // instantiations; see `ModuleTranslation::known_imported_globals` for
        // details.
        let ambiguous = ambiguous_entities(
            &self.static_modules,
            translation,
            &instantiations,
            &instances,
        );

        // Fourth, record which of each module's own defined entities all of
        // their importers agree on, which lets those modules use a precise alias
        // region for them even when they are exported.
        for (module, translation) in self.static_modules.iter_mut() {
            for i in 0..translation.module.num_defined_globals() {
                let index = DefinedGlobalIndex::new(i);
                let global = translation.module.global_index(index);
                if !ambiguous
                    .entities
                    .contains(&(module, EntityIndex::Global(global)))
                {
                    translation.globals_known_to_importers.insert(index);
                }
            }
            for i in 0..translation.module.num_defined_memories() {
                let index = DefinedMemoryIndex::new(i);
                let memory = translation.module.memory_index(index);
                if !ambiguous
                    .entities
                    .contains(&(module, EntityIndex::Memory(memory)))
                {
                    translation.memories_known_to_importers.insert(index);
                }
            }
            for i in 0..translation.module.num_defined_tables() {
                let index = DefinedTableIndex::new(i);
                let table = translation.module.table_index(index);
                if !ambiguous
                    .entities
                    .contains(&(module, EntityIndex::Table(table)))
                {
                    translation.tables_known_to_importers.insert(index);
                }
            }
        }

        // Finally, iterate over our instantiations and record statically-known
        // imports: function imports so that they can get translated into direct
        // calls (and eventually get inlined) rather than indirect calls through
        // the imports table; and global, memory, and table imports so that they
        // can get precise alias regions instead of the conservative regions
        // shared by everything that crosses a module boundary.
        for (module, instantiations) in instantiations.iter() {
            let args = match instantiations {
                dfg::AbstractInstantiations::Many | dfg::AbstractInstantiations::None => continue,
                dfg::AbstractInstantiations::One(args) => args,
            };

            for (i, arg) in args.iter().enumerate() {
                // Record that this global, memory, or table import is always the
                // same defined entity, when we know that and when everything
                // else that imports that entity knows it too.
                macro_rules! record_known_entity {
                    ($variant:ident, $imported:expr, $defined_index:ident, $known:ident, $wrap:expr) => {{
                        let Some((arg_module, EntityIndex::$variant(arg_entity))) =
                            unambiguous_entity(
                                &self.static_modules,
                                &instances,
                                &ambiguous.entities,
                                arg,
                            )
                        else {
                            continue;
                        };
                        let index = self.static_modules[arg_module]
                            .module
                            .$defined_index(arg_entity)
                            .expect(
                                "`resolve_core_export` only returns entities that their module \
                                 defines",
                            );
                        assert!(self.static_modules[module].$known[$imported].is_none());
                        self.static_modules[module].$known[$imported] = Some($wrap(KnownEntity {
                            module: arg_module,
                            index,
                        }));
                    }};
                }

                match self.static_modules[module].module.import_index(i).unwrap() {
                    EntityIndex::Function(imported_func) => {
                        debug_assert!(
                            self.static_modules[module]
                                .module
                                .defined_func_index(imported_func)
                                .is_none()
                        );

                        let known_func = match arg {
                            CoreDef::InstanceFlags(_) => {
                                unreachable!("instance flags are not a function")
                            }

                            // We could in theory inline these trampolines, so it
                            // could potentially make sense to record that we
                            // know this imported function is this particular
                            // trampoline. However, everything else is based
                            // around (module, defined-function) pairs and these
                            // trampolines don't fit that paradigm. Also,
                            // inlining trampolines gets really tricky when we
                            // consider the stack pointer, frame pointer, and
                            // return address note-taking that they do for the
                            // purposes of stack walking. We could, with enough
                            // effort, turn them into direct calls even though we
                            // probably wouldn't ever inline them, but it just
                            // doesn't seem worth the effort.
                            //
                            // That said, a couple of adapter trampolines are
                            // lowered inline during translation. We record these
                            // here so `FuncEnvironment` recognizes them. All
                            // other trampolines remain indirect calls.
                            CoreDef::Trampoline(index) => match translation.trampolines[*index] {
                                Trampoline::EnterSyncCall => {
                                    FactInlineIntrinsic::EnterSyncCall.into()
                                }
                                Trampoline::ExitSyncCall => {
                                    FactInlineIntrinsic::ExitSyncCall.into()
                                }
                                Trampoline::Trap(trap) => FactInlineIntrinsic::Trap(trap).into(),
                                _ => continue,
                            },

                            // This import is a compile-time builtin intrinsic,
                            // we should inline its implementation during
                            // function translation.
                            CoreDef::UnsafeIntrinsic(i) => {
                                FuncKey::UnsafeIntrinsic(Abi::Wasm, *i).into()
                            }

                            // This imported function is an export from another
                            // instance, a perfect candidate for becoming an
                            // inlinable direct call!
                            CoreDef::Export(export) => {
                                let Some((arg_module, arg_entity)) =
                                    resolve_core_export(&self.static_modules, &instances, export)
                                else {
                                    // Either an instance of a dynamic module that
                                    // is not part of this component, or a
                                    // re-export chain that bottoms out in
                                    // something that isn't a defined function
                                    // (for example a re-export of a trampoline;
                                    // note that we only match trampolines and
                                    // intrinsics as *direct* arguments above).
                                    // Either way we have to do an indirect call.
                                    continue;
                                };

                                let EntityIndex::Function(arg_func) = arg_entity else {
                                    unreachable!("function imports must be functions")
                                };

                                let arg_module_def_func = self.static_modules[arg_module]
                                    .module
                                    .defined_func_index(arg_func)
                                    .expect(
                                        "`resolve_core_export` only returns entities that their \
                                         module defines",
                                    );

                                FuncKey::DefinedWasmFunction(arg_module, arg_module_def_func).into()
                            }
                        };

                        assert!(
                            self.static_modules[module].known_imported_functions[imported_func]
                                .is_none()
                        );
                        self.static_modules[module].known_imported_functions[imported_func] =
                            Some(known_func);
                    }

                    // Note that a global import is not necessarily satisfied by a
                    // wasm global: it can also be one of the component-model
                    // flags that live in the `VMComponentContext`, and those get
                    // their own alias regions rather than a defined-global one.
                    EntityIndex::Global(imported_global) => match component_flags(arg) {
                        Some(flags) => {
                            if ambiguous.flags.contains(&flags) {
                                continue;
                            }
                            assert!(
                                self.static_modules[module].known_imported_globals[imported_global]
                                    .is_none()
                            );
                            self.static_modules[module].known_imported_globals[imported_global] =
                                Some(flags);
                        }
                        None => record_known_entity!(
                            Global,
                            imported_global,
                            defined_global_index,
                            known_imported_globals,
                            KnownGlobal::Defined
                        ),
                    },

                    EntityIndex::Memory(imported_memory) => record_known_entity!(
                        Memory,
                        imported_memory,
                        defined_memory_index,
                        known_imported_memories,
                        core::convert::identity
                    ),

                    EntityIndex::Table(imported_table) => record_known_entity!(
                        Table,
                        imported_table,
                        defined_table_index,
                        known_imported_tables,
                        core::convert::identity
                    ),

                    // Tags don't have alias regions of their own.
                    EntityIndex::Tag(_) => {}
                }
            }
        }
    }

    fn translate_payload(
        &mut self,
        payload: Payload<'data>,
        component: &'data [u8],
    ) -> Result<Action> {
        match payload {
            Payload::Version {
                num,
                encoding,
                range,
            } => {
                self.validator.version(num, encoding, &range)?;

                match encoding {
                    Encoding::Component => {}
                    Encoding::Module => {
                        bail!("attempted to parse a wasm module with a component parser");
                    }
                }
            }

            Payload::End(offset) => {
                assert!(self.result.types.is_none());
                self.result.types = Some(self.validator.end(offset)?);

                // Exit the current lexical scope. If there is no parent (no
                // frame currently on the stack) then translation is finished.
                // Otherwise that means that a nested component has been
                // completed and is recorded as such.
                let LexicalScope {
                    parser,
                    translation,
                    closure_args,
                } = match self.lexical_scopes.pop() {
                    Some(frame) => frame,
                    None => return Ok(Action::Done),
                };
                self.parser = parser;
                let component = mem::replace(&mut self.result, translation);
                let static_idx = self.static_components.push(component);
                self.result
                    .initializers
                    .push(LocalInitializer::ComponentStatic(static_idx, closure_args));
            }

            // When we see a type section the types are validated and then
            // translated into Wasmtime's representation. Each active type
            // definition is recorded in the `ComponentTypesBuilder` tables, or
            // this component's active scope.
            //
            // Note that the push/pop of the component types scope happens above
            // in `Version` and `End` since multiple type sections can appear
            // within a component.
            Payload::ComponentTypeSection(s) => {
                let mut component_type_index =
                    self.validator.types(0).unwrap().component_type_count();
                self.validator.component_type_section(&s)?;

                // Look for resource types and if a local resource is defined
                // then an initializer is added to define that resource type and
                // reference its destructor.
                let types = self.validator.types(0).unwrap();
                for ty in s {
                    match ty? {
                        wasmparser::ComponentType::Resource { rep, dtor } => {
                            let rep = self.types.convert_valtype(rep)?;
                            let id = types
                                .component_any_type_at(component_type_index)
                                .unwrap_resource();
                            let dtor = dtor.map(FuncIndex::from_u32);
                            self.result
                                .initializers
                                .push(LocalInitializer::Resource(id, rep, dtor));
                        }

                        // no extra processing needed
                        wasmparser::ComponentType::Defined(_)
                        | wasmparser::ComponentType::Func(_)
                        | wasmparser::ComponentType::Instance(_)
                        | wasmparser::ComponentType::Component(_) => {}
                    }

                    component_type_index += 1;
                }
            }
            Payload::CoreTypeSection(s) => {
                self.validator.core_type_section(&s)?;
            }

            // Processing the import section at this point is relatively simple
            // which is to simply record the name of the import and the type
            // information associated with it.
            Payload::ComponentImportSection(s) => {
                self.validator.component_import_section(&s)?;
                for import in s {
                    let import = import?;
                    let types = self.validator.types(0).unwrap();
                    let ty = types
                        .component_item_for_import(import.name.name)
                        .unwrap()
                        .ty;

                    if self.is_unsafe_intrinsics_import(import.name.name) {
                        self.check_unsafe_intrinsics_import(import.name.name, ty)?;
                        self.result
                            .initializers
                            .push(LocalInitializer::IntrinsicsImport);
                    } else {
                        self.result
                            .initializers
                            .push(LocalInitializer::Import(import.name, ty));
                    }
                }
            }

            // Entries in the canonical section will get initializers recorded
            // with the listed options for lifting/lowering.
            Payload::ComponentCanonicalSection(s) => {
                let types = self.validator.types(0).unwrap();
                let mut core_func_index = types.function_count();
                self.validator.component_canonical_section(&s)?;
                for func in s {
                    let init = match func? {
                        wasmparser::CanonicalFunction::Lift {
                            type_index,
                            core_func_index,
                            options,
                        } => {
                            let ty = self
                                .validator
                                .types(0)
                                .unwrap()
                                .component_any_type_at(type_index)
                                .unwrap_func();

                            let func = FuncIndex::from_u32(core_func_index);
                            let options = self.canonical_options(&options, core_func_index)?;
                            LocalInitializer::Lift(ty, func, options)
                        }
                        wasmparser::CanonicalFunction::Lower {
                            func_index,
                            options,
                        } => {
                            let lower_ty = self
                                .validator
                                .types(0)
                                .unwrap()
                                .component_function_at(func_index);
                            let func = ComponentFuncIndex::from_u32(func_index);
                            let options = self.canonical_options(&options, core_func_index)?;
                            core_func_index += 1;
                            LocalInitializer::Lower {
                                func,
                                options,
                                lower_ty,
                            }
                        }
                        wasmparser::CanonicalFunction::ResourceNew { resource } => {
                            let resource = self
                                .validator
                                .types(0)
                                .unwrap()
                                .component_any_type_at(resource)
                                .unwrap_resource();
                            let ty = self.core_func_signature(core_func_index)?;
                            core_func_index += 1;
                            LocalInitializer::ResourceNew(resource, ty)
                        }
                        wasmparser::CanonicalFunction::ResourceDrop { resource } => {
                            let resource = self
                                .validator
                                .types(0)
                                .unwrap()
                                .component_any_type_at(resource)
                                .unwrap_resource();
                            let ty = self.core_func_signature(core_func_index)?;
                            core_func_index += 1;
                            LocalInitializer::ResourceDrop(resource, ty)
                        }
                        wasmparser::CanonicalFunction::ResourceRep { resource } => {
                            let resource = self
                                .validator
                                .types(0)
                                .unwrap()
                                .component_any_type_at(resource)
                                .unwrap_resource();
                            let ty = self.core_func_signature(core_func_index)?;
                            core_func_index += 1;
                            LocalInitializer::ResourceRep(resource, ty)
                        }
                        wasmparser::CanonicalFunction::ThreadSpawnRef { .. }
                        | wasmparser::CanonicalFunction::ThreadSpawnIndirect { .. }
                        | wasmparser::CanonicalFunction::ThreadAvailableParallelism => {
                            bail!("unsupported intrinsic")
                        }
                        wasmparser::CanonicalFunction::BackpressureInc => {
                            let core_type = self.core_func_signature(core_func_index)?;
                            core_func_index += 1;
                            LocalInitializer::BackpressureInc { func: core_type }
                        }
                        wasmparser::CanonicalFunction::BackpressureDec => {
                            let core_type = self.core_func_signature(core_func_index)?;
                            core_func_index += 1;
                            LocalInitializer::BackpressureDec { func: core_type }
                        }

                        wasmparser::CanonicalFunction::TaskReturn { result, options } => {
                            let result = result.map(|ty| match ty {
                                wasmparser::ComponentValType::Primitive(ty) => {
                                    ComponentValType::Primitive(ty)
                                }
                                wasmparser::ComponentValType::Type(ty) => ComponentValType::Type(
                                    self.validator
                                        .types(0)
                                        .unwrap()
                                        .component_defined_type_at(ty),
                                ),
                            });
                            let options = self.canonical_options(&options, core_func_index)?;
                            core_func_index += 1;
                            LocalInitializer::TaskReturn { result, options }
                        }
                        wasmparser::CanonicalFunction::TaskCancel => {
                            let func = self.core_func_signature(core_func_index)?;
                            core_func_index += 1;
                            LocalInitializer::TaskCancel { func }
                        }
                        wasmparser::CanonicalFunction::WaitableSetNew => {
                            let func = self.core_func_signature(core_func_index)?;
                            core_func_index += 1;
                            LocalInitializer::WaitableSetNew { func }
                        }
                        wasmparser::CanonicalFunction::WaitableSetWait { memory } => {
                            let core_type = self.core_func_signature(core_func_index)?;
                            core_func_index += 1;
                            LocalInitializer::WaitableSetWait {
                                options: LocalCanonicalOptions {
                                    core_type,
                                    async_: false,
                                    data_model: LocalDataModel::LinearMemory {
                                        memory: Some(MemoryIndex::from_u32(memory)),
                                        realloc: None,
                                    },
                                    post_return: None,
                                    callback: None,
                                    string_encoding: StringEncoding::Utf8,
                                },
                            }
                        }
                        wasmparser::CanonicalFunction::WaitableSetPoll { memory } => {
                            let core_type = self.core_func_signature(core_func_index)?;
                            core_func_index += 1;
                            LocalInitializer::WaitableSetPoll {
                                options: LocalCanonicalOptions {
                                    core_type,
                                    async_: false,
                                    data_model: LocalDataModel::LinearMemory {
                                        memory: Some(MemoryIndex::from_u32(memory)),
                                        realloc: None,
                                    },
                                    post_return: None,
                                    callback: None,
                                    string_encoding: StringEncoding::Utf8,
                                },
                            }
                        }
                        wasmparser::CanonicalFunction::WaitableSetDrop => {
                            let func = self.core_func_signature(core_func_index)?;
                            core_func_index += 1;
                            LocalInitializer::WaitableSetDrop { func }
                        }
                        wasmparser::CanonicalFunction::WaitableJoin => {
                            let func = self.core_func_signature(core_func_index)?;
                            core_func_index += 1;
                            LocalInitializer::WaitableJoin { func }
                        }
                        wasmparser::CanonicalFunction::SubtaskDrop => {
                            let func = self.core_func_signature(core_func_index)?;
                            core_func_index += 1;
                            LocalInitializer::SubtaskDrop { func }
                        }
                        wasmparser::CanonicalFunction::SubtaskCancel { async_ } => {
                            let func = self.core_func_signature(core_func_index)?;
                            core_func_index += 1;
                            LocalInitializer::SubtaskCancel { func, async_ }
                        }
                        wasmparser::CanonicalFunction::StreamNew { ty } => {
                            let ty = self
                                .validator
                                .types(0)
                                .unwrap()
                                .component_defined_type_at(ty);
                            let func = self.core_func_signature(core_func_index)?;
                            core_func_index += 1;
                            LocalInitializer::StreamNew { ty, func }
                        }
                        wasmparser::CanonicalFunction::StreamRead { ty, options } => {
                            let ty = self
                                .validator
                                .types(0)
                                .unwrap()
                                .component_defined_type_at(ty);
                            let options = self.canonical_options(&options, core_func_index)?;
                            core_func_index += 1;
                            LocalInitializer::StreamRead { ty, options }
                        }
                        wasmparser::CanonicalFunction::StreamWrite { ty, options } => {
                            let ty = self
                                .validator
                                .types(0)
                                .unwrap()
                                .component_defined_type_at(ty);
                            let options = self.canonical_options(&options, core_func_index)?;
                            core_func_index += 1;
                            LocalInitializer::StreamWrite { ty, options }
                        }
                        wasmparser::CanonicalFunction::StreamCancelRead { ty, async_ } => {
                            let ty = self
                                .validator
                                .types(0)
                                .unwrap()
                                .component_defined_type_at(ty);
                            let func = self.core_func_signature(core_func_index)?;
                            core_func_index += 1;
                            LocalInitializer::StreamCancelRead { ty, func, async_ }
                        }
                        wasmparser::CanonicalFunction::StreamCancelWrite { ty, async_ } => {
                            let ty = self
                                .validator
                                .types(0)
                                .unwrap()
                                .component_defined_type_at(ty);
                            let func = self.core_func_signature(core_func_index)?;
                            core_func_index += 1;
                            LocalInitializer::StreamCancelWrite { ty, func, async_ }
                        }
                        wasmparser::CanonicalFunction::StreamDropReadable { ty } => {
                            let ty = self
                                .validator
                                .types(0)
                                .unwrap()
                                .component_defined_type_at(ty);
                            let func = self.core_func_signature(core_func_index)?;
                            core_func_index += 1;
                            LocalInitializer::StreamDropReadable { ty, func }
                        }
                        wasmparser::CanonicalFunction::StreamDropWritable { ty } => {
                            let ty = self
                                .validator
                                .types(0)
                                .unwrap()
                                .component_defined_type_at(ty);
                            let func = self.core_func_signature(core_func_index)?;
                            core_func_index += 1;
                            LocalInitializer::StreamDropWritable { ty, func }
                        }
                        wasmparser::CanonicalFunction::FutureNew { ty } => {
                            let ty = self
                                .validator
                                .types(0)
                                .unwrap()
                                .component_defined_type_at(ty);
                            let func = self.core_func_signature(core_func_index)?;
                            core_func_index += 1;
                            LocalInitializer::FutureNew { ty, func }
                        }
                        wasmparser::CanonicalFunction::FutureRead { ty, options } => {
                            let ty = self
                                .validator
                                .types(0)
                                .unwrap()
                                .component_defined_type_at(ty);
                            let options = self.canonical_options(&options, core_func_index)?;
                            core_func_index += 1;
                            LocalInitializer::FutureRead { ty, options }
                        }
                        wasmparser::CanonicalFunction::FutureWrite { ty, options } => {
                            let ty = self
                                .validator
                                .types(0)
                                .unwrap()
                                .component_defined_type_at(ty);
                            let options = self.canonical_options(&options, core_func_index)?;
                            core_func_index += 1;
                            LocalInitializer::FutureWrite { ty, options }
                        }
                        wasmparser::CanonicalFunction::FutureCancelRead { ty, async_ } => {
                            let ty = self
                                .validator
                                .types(0)
                                .unwrap()
                                .component_defined_type_at(ty);
                            let func = self.core_func_signature(core_func_index)?;
                            core_func_index += 1;
                            LocalInitializer::FutureCancelRead { ty, func, async_ }
                        }
                        wasmparser::CanonicalFunction::FutureCancelWrite { ty, async_ } => {
                            let ty = self
                                .validator
                                .types(0)
                                .unwrap()
                                .component_defined_type_at(ty);
                            let func = self.core_func_signature(core_func_index)?;
                            core_func_index += 1;
                            LocalInitializer::FutureCancelWrite { ty, func, async_ }
                        }
                        wasmparser::CanonicalFunction::FutureDropReadable { ty } => {
                            let ty = self
                                .validator
                                .types(0)
                                .unwrap()
                                .component_defined_type_at(ty);
                            let func = self.core_func_signature(core_func_index)?;
                            core_func_index += 1;
                            LocalInitializer::FutureDropReadable { ty, func }
                        }
                        wasmparser::CanonicalFunction::FutureDropWritable { ty } => {
                            let ty = self
                                .validator
                                .types(0)
                                .unwrap()
                                .component_defined_type_at(ty);
                            let func = self.core_func_signature(core_func_index)?;
                            core_func_index += 1;
                            LocalInitializer::FutureDropWritable { ty, func }
                        }
                        wasmparser::CanonicalFunction::ErrorContextNew { options } => {
                            let options = self.canonical_options(&options, core_func_index)?;
                            core_func_index += 1;
                            LocalInitializer::ErrorContextNew { options }
                        }
                        wasmparser::CanonicalFunction::ErrorContextDebugMessage { options } => {
                            let options = self.canonical_options(&options, core_func_index)?;
                            core_func_index += 1;
                            LocalInitializer::ErrorContextDebugMessage { options }
                        }
                        wasmparser::CanonicalFunction::ErrorContextDrop => {
                            let func = self.core_func_signature(core_func_index)?;
                            core_func_index += 1;
                            LocalInitializer::ErrorContextDrop { func }
                        }
                        wasmparser::CanonicalFunction::ContextGet { slot, ty } => {
                            if ty != wasmparser::ValType::I32 {
                                bail!("unsupported context.get type: {ty:?}");
                            }
                            let func = self.core_func_signature(core_func_index)?;
                            core_func_index += 1;
                            LocalInitializer::ContextGet { i: slot, func }
                        }
                        wasmparser::CanonicalFunction::ContextSet { slot, ty } => {
                            if ty != wasmparser::ValType::I32 {
                                bail!("unsupported context.set type: {ty:?}");
                            }
                            let func = self.core_func_signature(core_func_index)?;
                            core_func_index += 1;
                            LocalInitializer::ContextSet { i: slot, func }
                        }
                        wasmparser::CanonicalFunction::ThreadIndex => {
                            let func = self.core_func_signature(core_func_index)?;
                            core_func_index += 1;
                            LocalInitializer::ThreadIndex { func }
                        }
                        wasmparser::CanonicalFunction::ThreadNewIndirect {
                            func_ty_index,
                            table_index,
                        } => {
                            let func = self.core_func_signature(core_func_index)?;
                            core_func_index += 1;
                            LocalInitializer::ThreadNewIndirect {
                                func,
                                start_func_ty: ComponentTypeIndex::from_u32(func_ty_index),
                                start_func_table_index: TableIndex::from_u32(table_index),
                            }
                        }
                        wasmparser::CanonicalFunction::ThreadResumeLater => {
                            let func = self.core_func_signature(core_func_index)?;
                            core_func_index += 1;
                            LocalInitializer::ThreadResumeLater { func }
                        }
                        wasmparser::CanonicalFunction::ThreadSuspend => {
                            let func = self.core_func_signature(core_func_index)?;
                            core_func_index += 1;
                            LocalInitializer::ThreadSuspend { func }
                        }
                        wasmparser::CanonicalFunction::ThreadYield => {
                            let func = self.core_func_signature(core_func_index)?;
                            core_func_index += 1;
                            LocalInitializer::ThreadYield { func }
                        }
                        wasmparser::CanonicalFunction::ThreadSuspendThenResume => {
                            let func = self.core_func_signature(core_func_index)?;
                            core_func_index += 1;
                            LocalInitializer::ThreadSuspendThenResume { func }
                        }
                        wasmparser::CanonicalFunction::ThreadYieldThenResume => {
                            let func = self.core_func_signature(core_func_index)?;
                            core_func_index += 1;
                            LocalInitializer::ThreadYieldThenResume { func }
                        }
                        wasmparser::CanonicalFunction::ThreadSuspendThenPromote => {
                            let func = self.core_func_signature(core_func_index)?;
                            core_func_index += 1;
                            LocalInitializer::ThreadSuspendThenPromote { func }
                        }
                        wasmparser::CanonicalFunction::ThreadYieldThenPromote => {
                            let func = self.core_func_signature(core_func_index)?;
                            core_func_index += 1;
                            LocalInitializer::ThreadYieldThenPromote { func }
                        }
                    };
                    self.result.initializers.push(init);
                }
            }

            // Core wasm modules are translated inline directly here with the
            // `ModuleEnvironment` from core wasm compilation. This will return
            // to the caller the size of the module so it knows how many bytes
            // of the input are skipped.
            //
            // Note that this is just initial type translation of the core wasm
            // module and actual function compilation is deferred until this
            // entire process has completed.
            Payload::ModuleSection {
                parser,
                unchecked_range,
            } => {
                let index = self.validator.types(0).unwrap().module_count();
                self.validator.module_section(&unchecked_range)?;
                let static_module_index = self.static_modules.next_key();
                let mut translation = ModuleEnvironment::new(
                    self.tunables,
                    self.validator,
                    self.types.module_types_builder(),
                    static_module_index,
                )
                .translate(
                    parser,
                    component
                        .get(unchecked_range.start as usize..unchecked_range.end as usize)
                        .ok_or_else(|| {
                            format_err!(
                                "section range {}..{} is out of bounds (bound = {})",
                                unchecked_range.start,
                                unchecked_range.end,
                                component.len()
                            )
                            .context("wasm component contains an invalid module section")
                        })?,
                )?;

                translation.wasm_module_offset = unchecked_range.start;
                let static_module_index2 = self.static_modules.push(translation);
                assert_eq!(static_module_index, static_module_index2);
                let types = self.validator.types(0).unwrap();
                let ty = types.module_at(index);
                self.result
                    .initializers
                    .push(LocalInitializer::ModuleStatic(static_module_index, ty));
                return Ok(Action::Skip(
                    (unchecked_range.end - unchecked_range.start) as usize,
                ));
            }

            // When a sub-component is found then the current translation state
            // is pushed onto the `lexical_scopes` stack. This will subsequently
            // get popped as part of `Payload::End` processing above.
            //
            // Note that the set of closure args for this new lexical scope
            // starts empty since it will only get populated if translation of
            // the nested component ends up aliasing some outer module or
            // component.
            Payload::ComponentSection {
                parser,
                unchecked_range,
            } => {
                self.validator.component_section(&unchecked_range)?;
                self.lexical_scopes.push(LexicalScope {
                    parser: mem::replace(&mut self.parser, parser),
                    translation: mem::take(&mut self.result),
                    closure_args: ClosedOverVars::default(),
                });
            }

            // Both core wasm instances and component instances record
            // initializers of what form of instantiation is performed which
            // largely just records the arguments given from wasmparser into a
            // `HashMap` for processing later during inlining.
            Payload::InstanceSection(s) => {
                self.validator.instance_section(&s)?;
                for instance in s {
                    let init = match instance? {
                        wasmparser::Instance::Instantiate { module_index, args } => {
                            let index = ModuleIndex::from_u32(module_index);
                            self.instantiate_module(index, &args)
                        }
                        wasmparser::Instance::FromExports(exports) => {
                            self.instantiate_module_from_exports(&exports)
                        }
                    };
                    self.result.initializers.push(init);
                }
            }
            Payload::ComponentInstanceSection(s) => {
                let mut index = self.validator.types(0).unwrap().component_instance_count();
                self.validator.component_instance_section(&s)?;
                for instance in s {
                    let types = self.validator.types(0).unwrap();
                    let ty = types.component_instance_at(index);
                    let init = match instance? {
                        wasmparser::ComponentInstance::Instantiate {
                            component_index,
                            args,
                        } => {
                            let index = ComponentIndex::from_u32(component_index);
                            self.instantiate_component(index, &args, ty)?
                        }
                        wasmparser::ComponentInstance::FromExports(exports) => {
                            self.instantiate_component_from_exports(&exports, ty)?
                        }
                    };
                    self.result.initializers.push(init);
                    index += 1;
                }
            }

            // Exports don't actually fill out the `initializers` array but
            // instead fill out the one other field in a `Translation`, the
            // `exports` field (as one might imagine). This for now simply
            // records the index of what's exported and that's tracked further
            // later during inlining.
            Payload::ComponentExportSection(s) => {
                self.validator.component_export_section(&s)?;
                for export in s {
                    let export = export?;
                    let item = self.kind_to_item(export.kind, export.index)?;
                    let prev = self
                        .result
                        .exports
                        .insert(export.name.name, (item, export.name));
                    assert!(prev.is_none());
                    self.result
                        .initializers
                        .push(LocalInitializer::Export(item));
                }
            }

            Payload::ComponentStartSection { start, range } => {
                self.validator.component_start_section(&start, &range)?;
                unimplemented!("component start section");
            }

            // Aliases of instance exports (either core or component) will be
            // recorded as an initializer of the appropriate type with outer
            // aliases handled specially via upvars and type processing.
            Payload::ComponentAliasSection(s) => {
                self.validator.component_alias_section(&s)?;
                for alias in s {
                    let init = match alias? {
                        wasmparser::ComponentAlias::InstanceExport {
                            kind: _,
                            instance_index,
                            name,
                        } => {
                            let instance = ComponentInstanceIndex::from_u32(instance_index);
                            LocalInitializer::AliasComponentExport(instance, name)
                        }
                        wasmparser::ComponentAlias::Outer { kind, count, index } => {
                            self.alias_component_outer(kind, count, index);
                            continue;
                        }
                        wasmparser::ComponentAlias::CoreInstanceExport {
                            kind,
                            instance_index,
                            name,
                        } => {
                            let instance = ModuleInstanceIndex::from_u32(instance_index);
                            self.alias_module_instance_export(kind, instance, name)
                        }
                    };
                    self.result.initializers.push(init);
                }
            }

            // All custom sections are ignored by Wasmtime at this time.
            //
            // FIXME(WebAssembly/component-model#14): probably want to specify
            // and parse a `name` section here.
            Payload::CustomSection { .. } => {}

            // Anything else is either not reachable since we never enable the
            // feature in Wasmtime or we do enable it and it's a bug we don't
            // implement it, so let validation take care of most errors here and
            // if it gets past validation provide a helpful error message to
            // debug.
            other => {
                self.validator.payload(&other)?;
                panic!("unimplemented section {other:?}");
            }
        }

        Ok(Action::KeepGoing)
    }

    fn instantiate_module(
        &mut self,
        module: ModuleIndex,
        raw_args: &[wasmparser::InstantiationArg<'data>],
    ) -> LocalInitializer<'data> {
        let mut args = HashMap::with_capacity(raw_args.len());
        for arg in raw_args {
            match arg.kind {
                wasmparser::InstantiationArgKind::Instance => {
                    let idx = ModuleInstanceIndex::from_u32(arg.index);
                    args.insert(arg.name, idx);
                }
            }
        }
        LocalInitializer::ModuleInstantiate(module, args)
    }

    /// Creates a synthetic module from the list of items currently in the
    /// module and their given names.
    fn instantiate_module_from_exports(
        &mut self,
        exports: &[wasmparser::Export<'data>],
    ) -> LocalInitializer<'data> {
        let mut map = HashMap::with_capacity(exports.len());
        for export in exports {
            let idx = match export.kind {
                wasmparser::ExternalKind::Func | wasmparser::ExternalKind::FuncExact => {
                    let index = FuncIndex::from_u32(export.index);
                    EntityIndex::Function(index)
                }
                wasmparser::ExternalKind::Table => {
                    let index = TableIndex::from_u32(export.index);
                    EntityIndex::Table(index)
                }
                wasmparser::ExternalKind::Memory => {
                    let index = MemoryIndex::from_u32(export.index);
                    EntityIndex::Memory(index)
                }
                wasmparser::ExternalKind::Global => {
                    let index = GlobalIndex::from_u32(export.index);
                    EntityIndex::Global(index)
                }
                wasmparser::ExternalKind::Tag => {
                    let index = TagIndex::from_u32(export.index);
                    EntityIndex::Tag(index)
                }
            };
            map.insert(export.name, idx);
        }
        LocalInitializer::ModuleSynthetic(map)
    }

    fn instantiate_component(
        &mut self,
        component: ComponentIndex,
        raw_args: &[wasmparser::ComponentInstantiationArg<'data>],
        ty: ComponentInstanceTypeId,
    ) -> Result<LocalInitializer<'data>> {
        let mut args = HashMap::with_capacity(raw_args.len());
        for arg in raw_args {
            let idx = self.kind_to_item(arg.kind, arg.index)?;
            args.insert(arg.name, idx);
        }

        Ok(LocalInitializer::ComponentInstantiate(component, args, ty))
    }

    /// Creates a synthetic module from the list of items currently in the
    /// module and their given names.
    fn instantiate_component_from_exports(
        &mut self,
        exports: &[wasmparser::ComponentExport<'data>],
        ty: ComponentInstanceTypeId,
    ) -> Result<LocalInitializer<'data>> {
        let mut map = HashMap::with_capacity(exports.len());
        for export in exports {
            let idx = self.kind_to_item(export.kind, export.index)?;
            map.insert(export.name.name, (idx, export.name));
        }

        Ok(LocalInitializer::ComponentSynthetic(map, ty))
    }

    fn kind_to_item(
        &mut self,
        kind: wasmparser::ComponentExternalKind,
        index: u32,
    ) -> Result<ComponentItem> {
        Ok(match kind {
            wasmparser::ComponentExternalKind::Func => {
                let index = ComponentFuncIndex::from_u32(index);
                ComponentItem::Func(index)
            }
            wasmparser::ComponentExternalKind::Module => {
                let index = ModuleIndex::from_u32(index);
                ComponentItem::Module(index)
            }
            wasmparser::ComponentExternalKind::Instance => {
                let index = ComponentInstanceIndex::from_u32(index);
                ComponentItem::ComponentInstance(index)
            }
            wasmparser::ComponentExternalKind::Component => {
                let index = ComponentIndex::from_u32(index);
                ComponentItem::Component(index)
            }
            wasmparser::ComponentExternalKind::Value => {
                unimplemented!("component values");
            }
            wasmparser::ComponentExternalKind::Type => {
                let types = self.validator.types(0).unwrap();
                let ty = types.component_any_type_at(index);
                ComponentItem::Type(ty)
            }
        })
    }

    fn alias_module_instance_export(
        &mut self,
        kind: wasmparser::ExternalKind,
        instance: ModuleInstanceIndex,
        name: &'data str,
    ) -> LocalInitializer<'data> {
        match kind {
            wasmparser::ExternalKind::Func | wasmparser::ExternalKind::FuncExact => {
                LocalInitializer::AliasExportFunc(instance, name)
            }
            wasmparser::ExternalKind::Memory => LocalInitializer::AliasExportMemory(instance, name),
            wasmparser::ExternalKind::Table => LocalInitializer::AliasExportTable(instance, name),
            wasmparser::ExternalKind::Global => LocalInitializer::AliasExportGlobal(instance, name),
            wasmparser::ExternalKind::Tag => LocalInitializer::AliasExportTag(instance, name),
        }
    }

    fn alias_component_outer(
        &mut self,
        kind: wasmparser::ComponentOuterAliasKind,
        count: u32,
        index: u32,
    ) {
        match kind {
            wasmparser::ComponentOuterAliasKind::CoreType
            | wasmparser::ComponentOuterAliasKind::Type => {}

            // For more information about the implementation of outer aliases
            // see the documentation of `LexicalScope`. Otherwise though the
            // main idea here is that the data to close over starts as `Local`
            // and then transitions to `Upvar` as its inserted into the parents
            // in order from target we're aliasing back to the current
            // component.
            wasmparser::ComponentOuterAliasKind::CoreModule => {
                let index = ModuleIndex::from_u32(index);
                let mut module = ClosedOverModule::Local(index);
                let depth = self.lexical_scopes.len() - (count as usize);
                for frame in self.lexical_scopes[depth..].iter_mut() {
                    module = ClosedOverModule::Upvar(frame.closure_args.modules.push(module));
                }

                // If the `module` is still `Local` then the `depth` was 0 and
                // it's an alias into our own space. Otherwise it's switched to
                // an upvar and will index into the upvar space. Either way
                // it's just plumbed directly into the initializer.
                self.result
                    .initializers
                    .push(LocalInitializer::AliasModule(module));
            }
            wasmparser::ComponentOuterAliasKind::Component => {
                let index = ComponentIndex::from_u32(index);
                let mut component = ClosedOverComponent::Local(index);
                let depth = self.lexical_scopes.len() - (count as usize);
                for frame in self.lexical_scopes[depth..].iter_mut() {
                    component =
                        ClosedOverComponent::Upvar(frame.closure_args.components.push(component));
                }

                self.result
                    .initializers
                    .push(LocalInitializer::AliasComponent(component));
            }
        }
    }

    fn canonical_options(
        &mut self,
        opts: &[wasmparser::CanonicalOption],
        core_func_index: u32,
    ) -> WasmResult<LocalCanonicalOptions> {
        let core_type = self.core_func_signature(core_func_index)?;

        let mut string_encoding = StringEncoding::Utf8;
        let mut post_return = None;
        let mut async_ = false;
        let mut callback = None;
        let mut memory = None;
        let mut realloc = None;
        let mut gc = false;

        for opt in opts {
            match opt {
                wasmparser::CanonicalOption::UTF8 => {
                    string_encoding = StringEncoding::Utf8;
                }
                wasmparser::CanonicalOption::UTF16 => {
                    string_encoding = StringEncoding::Utf16;
                }
                wasmparser::CanonicalOption::CompactUTF16 => {
                    string_encoding = StringEncoding::CompactUtf16;
                }
                wasmparser::CanonicalOption::Memory(idx) => {
                    let idx = MemoryIndex::from_u32(*idx);
                    memory = Some(idx);
                }
                wasmparser::CanonicalOption::Realloc(idx) => {
                    let idx = FuncIndex::from_u32(*idx);
                    realloc = Some(idx);
                }
                wasmparser::CanonicalOption::PostReturn(idx) => {
                    let idx = FuncIndex::from_u32(*idx);
                    post_return = Some(idx);
                }
                wasmparser::CanonicalOption::Async => async_ = true,
                wasmparser::CanonicalOption::Callback(idx) => {
                    let idx = FuncIndex::from_u32(*idx);
                    callback = Some(idx);
                }
                wasmparser::CanonicalOption::CoreType(idx) => {
                    if cfg!(debug_assertions) {
                        let types = self.validator.types(0).unwrap();
                        let core_ty_id = types.core_type_at_in_component(*idx).unwrap_sub();
                        let interned = self
                            .types
                            .module_types_builder()
                            .intern_type(types, core_ty_id)?;
                        debug_assert_eq!(interned, core_type);
                    }
                }
                wasmparser::CanonicalOption::Gc => {
                    gc = true;
                }
            }
        }

        Ok(LocalCanonicalOptions {
            string_encoding,
            post_return,
            async_,
            callback,
            core_type,
            data_model: if gc {
                LocalDataModel::Gc {}
            } else {
                LocalDataModel::LinearMemory { memory, realloc }
            },
        })
    }

    /// Get the interned type index for the `index`th core function.
    fn core_func_signature(&mut self, index: u32) -> WasmResult<ModuleInternedTypeIndex> {
        let types = self.validator.types(0).unwrap();
        let id = types.core_function_at(index);
        self.types.module_types_builder().intern_type(types, id)
    }

    fn is_unsafe_intrinsics_import(&self, import: &str) -> bool {
        self.lexical_scopes.is_empty()
            && self
                .unsafe_intrinsics_import
                .is_some_and(|name| import == name)
    }

    fn check_unsafe_intrinsics_import(&self, import: &str, ty: ComponentEntityType) -> Result<()> {
        let types = &self.validator.types(0).unwrap();

        let ComponentEntityType::Instance(instance_ty) = ty else {
            bail!("bad unsafe intrinsics import: import `{import}` must be an instance import")
        };
        let instance_ty = &types[instance_ty];

        ensure!(
            instance_ty.defined_resources.is_empty(),
            "bad unsafe intrinsics import: import `{import}` cannot define any resources"
        );
        ensure!(
            instance_ty.explicit_resources.is_empty(),
            "bad unsafe intrinsics import: import `{import}` cannot export any resources"
        );

        for (name, ty) in &instance_ty.exports {
            let ComponentEntityType::Func(func_ty) = ty.ty else {
                bail!(
                    "bad unsafe intrinsics import: imported instance `{import}` must \
                     only export functions"
                )
            };
            let func_ty = &types[func_ty];

            fn ty_eq(a: &InterfaceType, b: &wasmparser::component_types::ComponentValType) -> bool {
                use wasmparser::{PrimitiveValType as P, component_types::ComponentValType as C};
                match (a, b) {
                    (InterfaceType::U8, C::Primitive(P::U8)) => true,
                    (InterfaceType::U8, _) => false,

                    (InterfaceType::U16, C::Primitive(P::U16)) => true,
                    (InterfaceType::U16, _) => false,

                    (InterfaceType::U32, C::Primitive(P::U32)) => true,
                    (InterfaceType::U32, _) => false,

                    (InterfaceType::U64, C::Primitive(P::U64)) => true,
                    (InterfaceType::U64, _) => false,

                    (ty, _) => unreachable!("no unsafe intrinsics use {ty:?}"),
                }
            }

            fn check_types<'a>(
                expected: impl ExactSizeIterator<Item = &'a InterfaceType>,
                actual: impl ExactSizeIterator<Item = &'a wasmparser::component_types::ComponentValType>,
                kind: &str,
                import: &str,
                name: &str,
            ) -> Result<()> {
                let expected_len = expected.len();
                let actual_len = actual.len();
                ensure!(
                    expected_len == actual_len,
                    "bad unsafe intrinsics import at `{import}`: function `{name}` must have \
                     {expected_len} {kind}, found {actual_len}"
                );

                for (i, (actual_ty, expected_ty)) in actual.zip(expected).enumerate() {
                    ensure!(
                        ty_eq(expected_ty, actual_ty),
                        "bad unsafe intrinsics import at `{import}`: {kind}[{i}] for function \
                         `{name}` must be `{expected_ty:?}`, found `{actual_ty:?}`"
                    );
                }
                Ok(())
            }

            let intrinsic = UnsafeIntrinsic::from_str(name)
                .with_context(|| format!("bad unsafe intrinsics import at `{import}`"))?;

            check_types(
                intrinsic.component_params().iter(),
                func_ty.params.iter().map(|(_name, ty)| ty),
                "parameters",
                &import,
                &name,
            )?;
            check_types(
                intrinsic.component_results().iter(),
                func_ty.result.iter(),
                "results",
                &import,
                &name,
            )?;
        }

        Ok(())
    }
}

impl Translation<'_> {
    fn types_ref(&self) -> wasmparser::types::TypesRef<'_> {
        self.types.as_ref().unwrap().as_ref()
    }
}

/// A small helper module which wraps a `ComponentTypesBuilder` and attempts
/// to disallow access to mutable access to the builder before the inlining
/// pass.
///
/// Type information in this translation pass must be preserved at the
/// wasmparser layer of abstraction rather than being lowered into Wasmtime's
/// own type system. Only during inlining are types fully assigned because
/// that's when resource types become available as it's known which instance
/// defines which resource, or more concretely the same component instantiated
/// twice will produce two unique resource types unlike one as seen by
/// wasmparser within the component.
mod pre_inlining {
    use super::*;

    pub struct PreInliningComponentTypes<'a> {
        types: &'a mut ComponentTypesBuilder,
    }

    impl<'a> PreInliningComponentTypes<'a> {
        pub fn new(types: &'a mut ComponentTypesBuilder) -> Self {
            Self { types }
        }

        pub fn module_types_builder(&mut self) -> &mut ModuleTypesBuilder {
            self.types.module_types_builder_mut()
        }

        pub fn types(&self) -> &ComponentTypesBuilder {
            self.types
        }

        // NB: this should in theory only be used for the `inline` phase of
        // translation.
        pub fn types_mut_for_inlining(&mut self) -> &mut ComponentTypesBuilder {
            self.types
        }
    }

    impl TypeConvert for PreInliningComponentTypes<'_> {
        fn lookup_heap_type(&self, index: wasmparser::UnpackedIndex) -> WasmHeapType {
            self.types.lookup_heap_type(index)
        }

        fn lookup_type_index(&self, index: wasmparser::UnpackedIndex) -> EngineOrModuleTypeIndex {
            self.types.lookup_type_index(index)
        }
    }
}
use pre_inlining::PreInliningComponentTypes;

/// A map from each runtime instance to the static module it is an instance of
/// and the arguments it was instantiated with, when we statically know them.
///
/// `None` for instances of modules that are not part of this component, and
/// whose shape we therefore cannot see into.
type StaticInstances<'a> =
    PrimaryMap<RuntimeInstanceIndex, Option<(StaticModuleIndex, &'a [CoreDef])>>;

/// Every entity whose identity is not statically known to everything that can
/// access it.
#[derive(Default)]
struct Ambiguous {
    /// Globals, memories, and tables defined by a static module in this
    /// component.
    entities: HashSet<(StaticModuleIndex, EntityIndex)>,

    /// Component-model flags living in the `VMComponentContext`. Only ever
    /// contains the non-`KnownGlobal::Defined` variants.
    flags: HashSet<KnownGlobal>,
}

/// Get the component-model flag that a `CoreDef` names, if it names one.
fn component_flags(def: &CoreDef) -> Option<KnownGlobal> {
    match def {
        CoreDef::InstanceFlags(instance) => Some(KnownGlobal::ComponentInstanceFlags(*instance)),
        CoreDef::Export(_) | CoreDef::Trampoline(_) | CoreDef::UnsafeIntrinsic(_) => None,
    }
}

/// Resolve a `CoreExport` to the static module that *defines* it and the entity
/// index it refers to within that module, when we can see through it statically.
///
/// A module may import an entity and then re-export it, in which case the
/// export names an index in the re-exporting module's *imported* index space.
/// We follow those chains all the way back to the module that actually defines
/// the entity, so that the returned pair is a canonical identity for it: every
/// reference to the same entity resolves to the same `(module, entity)` pair, no
/// matter how many modules it was laundered through along the way. That is
/// load-bearing for alias regions, where naming the same bytes with two
/// different keys is a miscompile.
///
/// Therefore a returned `Some((module, entity))` always satisfies
/// `!static_modules[module].module.is_imported(entity)`.
fn resolve_core_export(
    static_modules: &PrimaryMap<StaticModuleIndex, ModuleTranslation<'_>>,
    instances: &StaticInstances<'_>,
    export: &CoreExport<EntityIndex>,
) -> Option<(StaticModuleIndex, EntityIndex)> {
    let mut instance = export.instance;
    let mut item = &export.item;

    loop {
        // This can be an instance of a dynamic module that is not part of this
        // component, rather than a statically-known module inside of it.
        let (module, args) = instances[instance]?;

        let index = match item {
            ExportItem::Index(index) => *index,
            // Names are only used for instances of modules whose shape we don't
            // statically know, which we already filtered out.
            ExportItem::Name(_) => return None,
        };

        // The common case: this instance's module defines the entity itself, so
        // we've bottomed out at its canonical identity.
        if !static_modules[module].module.is_imported(index) {
            return Some((module, index));
        }

        // Otherwise this is a re-export of one of the module's imports, so keep
        // walking through whichever argument satisfied that import.
        let position = static_modules[module]
            .module
            .import_position(index)
            .expect("imported entities always have an associated import initializer");
        match &args[position] {
            CoreDef::Export(next) => {
                // An instantiation's arguments are always exports of instances
                // created before the instance being instantiated: `LinearizeDfg`
                // builds the argument `CoreDef`s before assigning the new
                // instance's `RuntimeInstanceIndex`, and would panic building an
                // export of an instance it had not linearized yet. So this walk
                // strictly decreases and must terminate.
                assert!(next.instance < instance);
                instance = next.instance;
                item = &next.item;
            }

            // The chain bottoms out in something that is not an export of
            // another instance in this component, so there is no defining module
            // for us to name.
            CoreDef::InstanceFlags(_) | CoreDef::Trampoline(_) | CoreDef::UnsafeIntrinsic(_) => {
                return None;
            }
        }
    }
}

/// Same as `resolve_core_export`, but for a `CoreDef` that must additionally be
/// unambiguous.
fn unambiguous_entity(
    static_modules: &PrimaryMap<StaticModuleIndex, ModuleTranslation<'_>>,
    instances: &StaticInstances<'_>,
    ambiguous: &HashSet<(StaticModuleIndex, EntityIndex)>,
    def: &CoreDef,
) -> Option<(StaticModuleIndex, EntityIndex)> {
    let CoreDef::Export(export) = def else {
        return None;
    };
    let entity = resolve_core_export(static_modules, instances, export)?;
    if ambiguous.contains(&entity) {
        return None;
    }
    Some(entity)
}

/// Find every core wasm entity in this component whose identity is *not*
/// statically known to every module that may import it.
///
/// An entity is unambiguous when every argument it flows into belongs to a
/// module that we only ever instantiate with that same entity:
///
/// * An argument to a module that we may instantiate differently elsewhere is
///   ambiguous because that module cannot statically know which one of these
///   entities it was given at runtime.
///
/// * An argument to an imported module is ambiguous because that module is
///   compiled separately from this component, and it may re-export the entity
///   back to us under a name we cannot see through, which we may then hand to a
///   module whose imports we do otherwise know.
///
/// Note that ambiguity is never partial: if a module importing an entity has to
/// conservatively tag its accesses with that entity's public alias region, then
/// the module defining the entity must do the same, or else inlining one of
/// them into the other would access the same bytes through two different alias
/// regions, which is invalid.
///
/// Entities in the returned set are identified by the module that *defines*
/// them, as resolved by `resolve_core_export`. That is what makes the previous
/// paragraph work through re-exports: marking a module's re-export of an import
/// as ambiguous poisons the definition it ultimately refers to, and therefore
/// every other module that can reach that definition, and not just the
/// re-exporter.
fn ambiguous_entities(
    static_modules: &PrimaryMap<StaticModuleIndex, ModuleTranslation<'_>>,
    translation: &ComponentTranslation,
    instantiations: &SecondaryMap<StaticModuleIndex, dfg::AbstractInstantiations<'_>>,
    instances: &StaticInstances<'_>,
) -> Ambiguous {
    let mut ambiguous = Ambiguous::default();

    let mut mark = |def: &CoreDef| match def {
        CoreDef::Export(export) => {
            if let Some(entity) = resolve_core_export(static_modules, instances, export) {
                ambiguous.entities.insert(entity);
            }
        }

        CoreDef::InstanceFlags(_) => {
            ambiguous.flags.insert(component_flags(def).unwrap());
        }

        // Neither of these is an entity that gets an alias region keyed by a
        // defining module and index.
        CoreDef::Trampoline(_) | CoreDef::UnsafeIntrinsic(_) => {}
    };

    for init in &translation.component.initializers {
        match init {
            GlobalInitializer::InstantiateModule(instantiation, _) => match instantiation {
                InstantiateModule::Static(module, args) => {
                    // Arguments to modules that we only instantiate one way are
                    // exactly the references that keep an entity unambiguous, so
                    // they are the one case we do not mark here. Everything else
                    // gets whichever of a number of different entities it was
                    // handed at runtime, and so has to be conservative.
                    if !matches!(instantiations[*module], dfg::AbstractInstantiations::One(_)) {
                        for arg in args.iter() {
                            mark(arg);
                        }
                    }
                }

                // We cannot see through an imported module's exports, so an
                // entity we pass into one and that comes back out to a module
                // whose imports we do know would be accessed via two different
                // alias regions.
                InstantiateModule::Import(_, args) => {
                    for arg in args.values().flat_map(|args| args.values()) {
                        mark(arg);
                    }
                }
            },

            // The remaining initializers do not involve the global/table/memory
            // alias regions.
            GlobalInitializer::ExtractMemory(_)
            | GlobalInitializer::ExtractTable(_)
            | GlobalInitializer::ExtractRealloc(_)
            | GlobalInitializer::ExtractCallback(_)
            | GlobalInitializer::ExtractPostReturn(_)
            | GlobalInitializer::Resource(_)
            | GlobalInitializer::LowerImport { .. } => {}
        }
    }

    ambiguous
}