mirror of
https://github.com/denoland/deno.git
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ca66978a5a
This PR introduces Wasm ops. These calls are optimized for entry from
Wasm land.
The `#[op(wasm)]` attribute is opt-in.
Last parameter `Option<&mut [u8]>` is the memory slice of the Wasm
module *when entered from a Fast API call*. Otherwise, the user is
expected to implement logic to obtain the memory if `None`
```rust
#[op(wasm)]
pub fn op_args_get(
offset: i32,
buffer_offset: i32,
memory: Option<&mut [u8]>,
) {
// ...
}
```
62 lines
1.6 KiB
Markdown
62 lines
1.6 KiB
Markdown
# deno_ops
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`proc_macro` for generating highly optimized V8 functions from Deno ops.
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```rust
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// Declare an op.
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#[op(fast)]
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pub fn op_add(_: &mut OpState, a: i32, b: i32) -> i32 {
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a + b
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}
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// Register with an extension.
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Extension::builder()
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.ops(vec![op_add::decl()])
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.build();
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```
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## Performance
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The macro can optimize away code, short circuit fast paths and generate a Fast
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API impl.
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Cases where code is optimized away:
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- `-> ()` skips serde_v8 and `rv.set` calls.
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- `-> Result<(), E>` skips serde_v8 and `rv.set` calls for `Ok()` branch.
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- `-> ResourceId` or `-> [int]` types will use specialized method like
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`v8::ReturnValue::set_uint32`. A fast path for SMI.
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- `-> Result<ResourceId, E>` or `-> Result<[int], E>` types will be optimized
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like above for the `Ok()` branch.
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### Fast calls
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The macro will infer and try to auto generate V8 fast API call trait impl for
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`sync` ops with:
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- arguments: integers, bool, `&mut OpState`, `&[u8]`, `&mut [u8]`, `&[u32]`,
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`&mut [u32]`
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- return_type: integers, bool
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The `#[op(fast)]` attribute should be used to enforce fast call generation at
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compile time.
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Trait gen for `async` ops & a ZeroCopyBuf equivalent type is planned and will be
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added soon.
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### Wasm calls
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The `#[op(wasm)]` attribute should be used for calls expected to be called from
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Wasm. This enables the fast call generation and allows seamless `WasmMemory`
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integration for generic and fast calls.
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```rust
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#[op(wasm)]
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pub fn op_args_get(
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offset: i32,
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buffer_offset: i32,
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memory: Option<&[u8]>, // Must be last parameter. Some(..) when entered from Wasm.
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) {
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// ...
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}
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```
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