wasi-nn: update upstream specification (bytecodealliance#6853)

This change removes the temporary `*.wit` files and bumps the `spec`
directory to the latest [wasi-nn] commit. This is now possible because
the upstream `spec` repository has all of the updated WIT and WITX bits.
The `load_by_name` implementations are left as TODOs for now and will be
included in a subsequent PR.

One other change is a refactoring: we wrap up some types--`Graph` and
`ExecutionContext`--to avoid passing around `Box<dyn ...>`. This
simplifies some of the code but should not change behavior.

Run all tests: prtest:full

[wasi-nn]: https://github.com/WebAssembly/wasi-nn.

crates/wasi-nn/src/backend/mod.rs

@@ -6,33 +6,30 @@ mod openvino;
 
 use self::openvino::OpenvinoBackend;
 use crate::wit::types::{ExecutionTarget, Tensor};
+use crate::{ExecutionContext, Graph};
 use thiserror::Error;
 use wiggle::GuestError;
 
 /// Return a list of all available backend frameworks.
-pub(crate) fn list() -> Vec<(BackendKind, Box<dyn Backend>)> {
+pub fn list() -> Vec<(BackendKind, Box<dyn Backend>)> {
     vec![(BackendKind::OpenVINO, Box::new(OpenvinoBackend::default()))]
 }
 
 /// A [Backend] contains the necessary state to load [BackendGraph]s.
-pub(crate) trait Backend: Send + Sync {
+pub trait Backend: Send + Sync {
     fn name(&self) -> &str;
-    fn load(
-        &mut self,
-        builders: &[&[u8]],
-        target: ExecutionTarget,
-    ) -> Result<Box<dyn BackendGraph>, BackendError>;
+    fn load(&mut self, builders: &[&[u8]], target: ExecutionTarget) -> Result<Graph, BackendError>;
 }
 
 /// A [BackendGraph] can create [BackendExecutionContext]s; this is the backing
 /// implementation for a [crate::witx::types::Graph].
-pub(crate) trait BackendGraph: Send + Sync {
-    fn init_execution_context(&mut self) -> Result<Box<dyn BackendExecutionContext>, BackendError>;
+pub trait BackendGraph: Send + Sync {
+    fn init_execution_context(&mut self) -> Result<ExecutionContext, BackendError>;
 }
 
 /// A [BackendExecutionContext] performs the actual inference; this is the
 /// backing implementation for a [crate::witx::types::GraphExecutionContext].
-pub(crate) trait BackendExecutionContext: Send + Sync {
+pub trait BackendExecutionContext: Send + Sync {
     fn set_input(&mut self, index: u32, tensor: &Tensor) -> Result<(), BackendError>;
     fn compute(&mut self) -> Result<(), BackendError>;
     fn get_output(&mut self, index: u32, destination: &mut [u8]) -> Result<u32, BackendError>;
@@ -52,7 +49,7 @@ pub enum BackendError {
     NotEnoughMemory(usize),
 }
 
-#[derive(Hash, PartialEq, Eq, Clone, Copy)]
-pub(crate) enum BackendKind {
+#[derive(Hash, PartialEq, Debug, Eq, Clone, Copy)]
+pub enum BackendKind {
     OpenVINO,
 }

crates/wasi-nn/src/backend/openvino.rs

@@ -2,6 +2,7 @@
 
 use super::{Backend, BackendError, BackendExecutionContext, BackendGraph};
 use crate::wit::types::{ExecutionTarget, Tensor, TensorType};
+use crate::{ExecutionContext, Graph};
 use openvino::{InferenceError, Layout, Precision, SetupError, TensorDesc};
 use std::sync::Arc;
 
@@ -15,11 +16,7 @@ impl Backend for OpenvinoBackend {
         "openvino"
     }
 
-    fn load(
-        &mut self,
-        builders: &[&[u8]],
-        target: ExecutionTarget,
-    ) -> Result<Box<dyn BackendGraph>, BackendError> {
+    fn load(&mut self, builders: &[&[u8]], target: ExecutionTarget) -> Result<Graph, BackendError> {
         if builders.len() != 2 {
             return Err(BackendError::InvalidNumberOfBuilders(2, builders.len()).into());
         }
@@ -54,8 +51,9 @@ impl Backend for OpenvinoBackend {
 
         let exec_network =
             core.load_network(&cnn_network, map_execution_target_to_string(target))?;
-
-        Ok(Box::new(OpenvinoGraph(Arc::new(cnn_network), exec_network)))
+        let box_: Box<dyn BackendGraph> =
+            Box::new(OpenvinoGraph(Arc::new(cnn_network), exec_network));
+        Ok(box_.into())
     }
 }
 
@@ -65,12 +63,11 @@ unsafe impl Send for OpenvinoGraph {}
 unsafe impl Sync for OpenvinoGraph {}
 
 impl BackendGraph for OpenvinoGraph {
-    fn init_execution_context(&mut self) -> Result<Box<dyn BackendExecutionContext>, BackendError> {
+    fn init_execution_context(&mut self) -> Result<ExecutionContext, BackendError> {
         let infer_request = self.1.create_infer_request()?;
-        Ok(Box::new(OpenvinoExecutionContext(
-            self.0.clone(),
-            infer_request,
-        )))
+        let box_: Box<dyn BackendExecutionContext> =
+            Box::new(OpenvinoExecutionContext(self.0.clone(), infer_request));
+        Ok(box_.into())
     }
 }
 
@@ -145,5 +142,6 @@ fn map_tensor_type_to_precision(tensor_type: TensorType) -> openvino::Precision
         TensorType::Fp32 => Precision::FP32,
         TensorType::U8 => Precision::U8,
         TensorType::I32 => Precision::I32,
+        TensorType::Bf16 => todo!("not yet supported in `openvino` bindings"),
     }
 }

crates/wasi-nn/src/ctx.rs

@@ -1,36 +1,36 @@
 //! Implements the host state for the `wasi-nn` API: [WasiNnCtx].
 
-use crate::backend::{
-    self, Backend, BackendError, BackendExecutionContext, BackendGraph, BackendKind,
-};
+use crate::backend::{self, Backend, BackendError, BackendKind};
 use crate::wit::types::GraphEncoding;
-use std::collections::HashMap;
-use std::hash::Hash;
+use crate::{ExecutionContext, Graph};
+use std::{collections::HashMap, hash::Hash};
 use thiserror::Error;
 use wiggle::GuestError;
 
+type Backends = HashMap<BackendKind, Box<dyn Backend>>;
 type GraphId = u32;
 type GraphExecutionContextId = u32;
 
 /// Capture the state necessary for calling into the backend ML libraries.
 pub struct WasiNnCtx {
-    pub(crate) backends: HashMap<BackendKind, Box<dyn Backend>>,
-    pub(crate) graphs: Table<GraphId, Box<dyn BackendGraph>>,
-    pub(crate) executions: Table<GraphExecutionContextId, Box<dyn BackendExecutionContext>>,
+    pub(crate) backends: Backends,
+    pub(crate) graphs: Table<GraphId, Graph>,
+    pub(crate) executions: Table<GraphExecutionContextId, ExecutionContext>,
 }
 
 impl WasiNnCtx {
     /// Make a new context from the default state.
-    pub fn new() -> WasiNnResult<Self> {
-        let mut backends = HashMap::new();
-        for (kind, backend) in backend::list() {
-            backends.insert(kind, backend);
-        }
-        Ok(Self {
+    pub fn new(backends: Backends) -> Self {
+        Self {
             backends,
             graphs: Table::default(),
             executions: Table::default(),
-        })
+        }
+    }
+}
+impl Default for WasiNnCtx {
+    fn default() -> Self {
+        WasiNnCtx::new(backend::list().into_iter().collect())
     }
 }
 
@@ -59,6 +59,8 @@ pub enum UsageError {
     InvalidExecutionContextHandle,
     #[error("Not enough memory to copy tensor data of size: {0}")]
     NotEnoughMemory(u32),
+    #[error("No graph found with name: {0}")]
+    NotFound(String),
 }
 
 pub(crate) type WasiNnResult<T> = std::result::Result<T, WasiNnError>;
@@ -105,6 +107,6 @@ mod test {
 
     #[test]
     fn instantiate() {
-        WasiNnCtx::new().unwrap();
+        WasiNnCtx::default();
     }
 }

crates/wasi-nn/src/lib.rs

@@ -4,3 +4,41 @@ mod ctx;
 pub use ctx::WasiNnCtx;
 pub mod wit;
 pub mod witx;
+
+/// A backend-defined graph (i.e., ML model).
+pub struct Graph(Box<dyn backend::BackendGraph>);
+impl From<Box<dyn backend::BackendGraph>> for Graph {
+    fn from(value: Box<dyn backend::BackendGraph>) -> Self {
+        Self(value)
+    }
+}
+impl std::ops::Deref for Graph {
+    type Target = dyn backend::BackendGraph;
+    fn deref(&self) -> &Self::Target {
+        self.0.as_ref()
+    }
+}
+impl std::ops::DerefMut for Graph {
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        self.0.as_mut()
+    }
+}
+
+/// A backend-defined execution context.
+pub struct ExecutionContext(Box<dyn backend::BackendExecutionContext>);
+impl From<Box<dyn backend::BackendExecutionContext>> for ExecutionContext {
+    fn from(value: Box<dyn backend::BackendExecutionContext>) -> Self {
+        Self(value)
+    }
+}
+impl std::ops::Deref for ExecutionContext {
+    type Target = dyn backend::BackendExecutionContext;
+    fn deref(&self) -> &Self::Target {
+        self.0.as_ref()
+    }
+}
+impl std::ops::DerefMut for ExecutionContext {
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        self.0.as_mut()
+    }
+}

crates/wasi-nn/src/wit.rs

@@ -17,23 +17,29 @@
 
 use crate::{backend::BackendKind, ctx::UsageError, WasiNnCtx};
 
-pub use gen::types;
-pub use gen_::Ml as ML;
-
 /// Generate the traits and types from the `wasi-nn` WIT specification.
 mod gen_ {
-    wasmtime::component::bindgen!("ml");
+    wasmtime::component::bindgen!("ml" in "spec/wit/wasi-nn.wit");
 }
 use gen_::wasi::nn as gen; // Shortcut to the module containing the types we need.
 
-impl gen::inference::Host for WasiNnCtx {
+// Export the `types` used in this crate as well as `ML::add_to_linker`.
+pub mod types {
+    use super::gen;
+    pub use gen::graph::{ExecutionTarget, Graph, GraphEncoding};
+    pub use gen::inference::GraphExecutionContext;
+    pub use gen::tensor::{Tensor, TensorType};
+}
+pub use gen_::Ml as ML;
+
+impl gen::graph::Host for WasiNnCtx {
     /// Load an opaque sequence of bytes to use for inference.
     fn load(
         &mut self,
-        builders: gen::types::GraphBuilderArray,
-        encoding: gen::types::GraphEncoding,
-        target: gen::types::ExecutionTarget,
-    ) -> wasmtime::Result<Result<gen::types::Graph, gen::types::Error>> {
+        builders: Vec<gen::graph::GraphBuilder>,
+        encoding: gen::graph::GraphEncoding,
+        target: gen::graph::ExecutionTarget,
+    ) -> wasmtime::Result<Result<gen::graph::Graph, gen::errors::Error>> {
         let backend_kind: BackendKind = encoding.try_into()?;
         let graph = if let Some(backend) = self.backends.get_mut(&backend_kind) {
             let slices = builders.iter().map(|s| s.as_slice()).collect::<Vec<_>>();
@@ -45,13 +51,22 @@ impl gen::inference::Host for WasiNnCtx {
         Ok(Ok(graph_id))
     }
 
+    fn load_by_name(
+        &mut self,
+        _name: String,
+    ) -> wasmtime::Result<Result<gen::graph::Graph, gen::errors::Error>> {
+        todo!()
+    }
+}
+
+impl gen::inference::Host for WasiNnCtx {
     /// Create an execution instance of a loaded graph.
     ///
     /// TODO: remove completely?
     fn init_execution_context(
         &mut self,
-        graph_id: gen::types::Graph,
-    ) -> wasmtime::Result<Result<gen::types::GraphExecutionContext, gen::types::Error>> {
+        graph_id: gen::graph::Graph,
+    ) -> wasmtime::Result<Result<gen::inference::GraphExecutionContext, gen::errors::Error>> {
         let exec_context = if let Some(graph) = self.graphs.get_mut(graph_id) {
             graph.init_execution_context()?
         } else {
@@ -65,10 +80,10 @@ impl gen::inference::Host for WasiNnCtx {
     /// Define the inputs to use for inference.
     fn set_input(
         &mut self,
-        exec_context_id: gen::types::GraphExecutionContext,
+        exec_context_id: gen::inference::GraphExecutionContext,
         index: u32,
-        tensor: gen::types::Tensor,
-    ) -> wasmtime::Result<Result<(), gen::types::Error>> {
+        tensor: gen::tensor::Tensor,
+    ) -> wasmtime::Result<Result<(), gen::errors::Error>> {
         if let Some(exec_context) = self.executions.get_mut(exec_context_id) {
             exec_context.set_input(index, &tensor)?;
             Ok(Ok(()))
@@ -82,8 +97,8 @@ impl gen::inference::Host for WasiNnCtx {
     /// TODO: refactor to compute(list<tensor>) -> result<list<tensor>, error>
     fn compute(
         &mut self,
-        exec_context_id: gen::types::GraphExecutionContext,
-    ) -> wasmtime::Result<Result<(), gen::types::Error>> {
+        exec_context_id: gen::inference::GraphExecutionContext,
+    ) -> wasmtime::Result<Result<(), gen::errors::Error>> {
         if let Some(exec_context) = self.executions.get_mut(exec_context_id) {
             exec_context.compute()?;
             Ok(Ok(()))
@@ -95,9 +110,9 @@ impl gen::inference::Host for WasiNnCtx {
     /// Extract the outputs after inference.
     fn get_output(
         &mut self,
-        exec_context_id: gen::types::GraphExecutionContext,
+        exec_context_id: gen::inference::GraphExecutionContext,
         index: u32,
-    ) -> wasmtime::Result<Result<gen::types::TensorData, gen::types::Error>> {
+    ) -> wasmtime::Result<Result<gen::tensor::TensorData, gen::errors::Error>> {
         if let Some(exec_context) = self.executions.get_mut(exec_context_id) {
             // Read the output bytes. TODO: this involves a hard-coded upper
             // limit on the tensor size that is necessary because there is no
@@ -113,11 +128,11 @@ impl gen::inference::Host for WasiNnCtx {
     }
 }
 
-impl TryFrom<gen::types::GraphEncoding> for crate::backend::BackendKind {
+impl TryFrom<gen::graph::GraphEncoding> for crate::backend::BackendKind {
     type Error = UsageError;
-    fn try_from(value: gen::types::GraphEncoding) -> Result<Self, Self::Error> {
+    fn try_from(value: gen::graph::GraphEncoding) -> Result<Self, Self::Error> {
         match value {
-            gen::types::GraphEncoding::Openvino => Ok(crate::backend::BackendKind::OpenVINO),
+            gen::graph::GraphEncoding::Openvino => Ok(crate::backend::BackendKind::OpenVINO),
             _ => Err(UsageError::InvalidEncoding(value.into())),
         }
     }