Enum wasmtime_environ::component::Trampoline

pub enum Trampoline {
    LowerImport {
        index: LoweredIndex,
        lower_ty: TypeFuncIndex,
        options: CanonicalOptions,
    },
    Transcoder {
        op: Transcode,
        from: RuntimeMemoryIndex,
        from64: bool,
        to: RuntimeMemoryIndex,
        to64: bool,
    },
    AlwaysTrap,
    ResourceNew(TypeResourceTableIndex),
    ResourceRep(TypeResourceTableIndex),
    ResourceDrop(TypeResourceTableIndex),
    ResourceTransferOwn,
    ResourceTransferBorrow,
    ResourceEnterCall,
    ResourceExitCall,
}

A list of all possible trampolines that may be required to compile a component completely.

These trampolines are used often as core wasm definitions and require Cranelift support to generate these functions. Each trampoline serves a different purpose for implementing bits and pieces of the component model.

All trampolines have a core wasm function signature associated with them which is stored in the Component::trampolines array.

Note that this type does not implement Serialize or Deserialize and that’s intentional as this isn’t stored in the final compilation artifact.

Variants

LowerImport

Description of a lowered import used in conjunction with GlobalInitializer::LowerImport.

Fields

index: LoweredIndex

The runtime lowering state that this trampoline will access.

lower_ty: TypeFuncIndex

The type of the function that is being lowered, as perceived by the component doing the lowering.

options: CanonicalOptions

The canonical ABI options used when lowering this function specified in the original component.

Transcoder

Information about a string transcoding function required by an adapter module.

A transcoder is used when strings are passed between adapter modules, optionally changing string encodings at the same time. The transcoder is implemented in a few different layers:

• Each generated adapter module has some glue around invoking the transcoder represented by this item. This involves bounds-checks and handling realloc for example.
• Each transcoder gets a cranelift-generated trampoline which has the appropriate signature for the adapter module in question. Existence of this initializer indicates that this should be compiled by Cranelift.
• The cranelift-generated trampoline will invoke a “transcoder libcall” which is implemented natively in Rust that has a signature independent of memory64 configuration options for example.

Fields

op: Transcode

The transcoding operation being performed.

from: RuntimeMemoryIndex

The linear memory that the string is being read from.

from64: bool

Whether or not the source linear memory is 64-bit or not.

to: RuntimeMemoryIndex

The linear memory that the string is being written to.

to64: bool

Whether or not the destination linear memory is 64-bit or not.

AlwaysTrap

A small adapter which simply traps, used for degenerate lift/lower combinations.

ResourceNew(TypeResourceTableIndex)

A resource.new intrinsic which will inject a new resource into the table specified.

ResourceRep(TypeResourceTableIndex)

Same as ResourceNew, but for the resource.rep intrinsic.

ResourceDrop(TypeResourceTableIndex)

Same as ResourceNew, but for the resource.drop intrinsic.

ResourceTransferOwn

An intrinsic used by FACT-generated modules which will transfer an owned resource from one table to another. Used in component-to-component adapter trampolines.

ResourceTransferBorrow

Same as ResourceTransferOwn but for borrows.

ResourceEnterCall

An intrinsic used by FACT-generated modules which indicates that a call is being entered and resource-related metadata needs to be configured.

Note that this is currently only invoked when borrowed resources are detected, otherwise this is “optimized out”.

ResourceExitCall

Same as ResourceEnterCall except for when exiting a call.

Implementations

impl Trampoline

pub fn symbol_name(&self) -> String

Returns the name to use for the symbol of this trampoline in the final compiled artifact