Refactor the compilation and instantiation pipeline.

wasmtime-execute is now wasmtime-jit. Move `JITCode` and the TargetIsa
into a new `Compiler` type. `InstancePlus` is no more, with trampoline
functionality now handled by `Compiler`.

lib/jit/src/instantiate.rs

@@ -0,0 +1,199 @@
+//! Define the `instantiate` function, which takes a byte array containing an
+//! encoded wasm module and returns a live wasm instance. Also, define
+//! `CompiledModule` to allow compiling and instantiating to be done as separate
+//! steps.
+
+use compiler::Compiler;
+use cranelift_entity::{BoxedSlice, PrimaryMap};
+use cranelift_wasm::DefinedFuncIndex;
+use link::link_module;
+use resolver::Resolver;
+use std::boxed::Box;
+use std::rc::Rc;
+use std::string::String;
+use std::vec::Vec;
+use wasmtime_environ::{
+    CompileError, DataInitializer, DataInitializerLocation, Module, ModuleEnvironment,
+};
+use wasmtime_runtime::{Imports, Instance, InstantiationError, VMFunctionBody};
+
+/// An error condition while setting up a wasm instance, be it validation,
+/// compilation, or instantiation.
+#[derive(Fail, Debug)]
+pub enum SetupError {
+    /// The module did not pass validation.
+    #[fail(display = "Validation error: {}", _0)]
+    Validate(String),
+
+    /// A wasm translation error occured.
+    #[fail(display = "WebAssembly compilation error: {}", _0)]
+    Compile(CompileError),
+
+    /// Some runtime resource was unavailable or insufficient, or the start function
+    /// trapped.
+    #[fail(display = "Instantiation error: {}", _0)]
+    Instantiate(InstantiationError),
+}
+
+/// This is similar to `CompiledModule`, but references the data initializers
+/// from the wasm buffer rather than holding its own copy.
+struct RawCompiledModule<'data> {
+    module: Module,
+    finished_functions: BoxedSlice<DefinedFuncIndex, *const VMFunctionBody>,
+    imports: Imports,
+    data_initializers: Box<[DataInitializer<'data>]>,
+}
+
+impl<'data> RawCompiledModule<'data> {
+    /// Create a new `RawCompiledModule` by compiling the wasm module in `data` and instatiating it.
+    fn new(
+        compiler: &mut Compiler,
+        data: &'data [u8],
+        resolver: &mut Resolver,
+    ) -> Result<Self, SetupError> {
+        let environ = ModuleEnvironment::new(compiler.frontend_config(), compiler.tunables());
+
+        let translation = environ
+            .translate(data)
+            .map_err(|error| SetupError::Compile(CompileError::Wasm(error)))?;
+
+        let (allocated_functions, relocations) =
+            compiler.compile(&translation.module, translation.function_body_inputs)?;
+
+        let imports = link_module(
+            &translation.module,
+            &allocated_functions,
+            relocations,
+            resolver,
+        )
+        .map_err(|err| SetupError::Instantiate(InstantiationError::Link(err)))?;
+
+        // Gather up the pointers to the compiled functions.
+        let finished_functions: BoxedSlice<DefinedFuncIndex, *const VMFunctionBody> =
+            allocated_functions
+                .into_iter()
+                .map(|(_index, allocated)| {
+                    let fatptr: *const [VMFunctionBody] = *allocated;
+                    fatptr as *const VMFunctionBody
+                })
+                .collect::<PrimaryMap<_, _>>()
+                .into_boxed_slice();
+
+        // Make all code compiled thus far executable.
+        compiler.publish_compiled_code();
+
+        Ok(Self {
+            module: translation.module,
+            finished_functions,
+            imports,
+            data_initializers: translation.data_initializers.into_boxed_slice(),
+        })
+    }
+}
+
+/// A compiled wasm module, ready to be instantiated.
+pub struct CompiledModule {
+    module: Rc<Module>,
+    finished_functions: BoxedSlice<DefinedFuncIndex, *const VMFunctionBody>,
+    imports: Imports,
+    data_initializers: Box<[OwnedDataInitializer]>,
+}
+
+impl CompiledModule {
+    /// Compile a data buffer into a `CompiledModule`, which may then be instantiated.
+    pub fn new<'data>(
+        compiler: &mut Compiler,
+        data: &'data [u8],
+        resolver: &mut Resolver,
+    ) -> Result<Self, SetupError> {
+        let raw = RawCompiledModule::<'data>::new(compiler, data, resolver)?;
+
+        Ok(Self {
+            module: Rc::new(raw.module),
+            finished_functions: raw.finished_functions,
+            imports: raw.imports,
+            data_initializers: raw
+                .data_initializers
+                .iter()
+                .map(OwnedDataInitializer::new)
+                .collect::<Vec<_>>()
+                .into_boxed_slice(),
+        })
+    }
+
+    /// Construct a `CompiledModule` from component parts.
+    pub fn from_parts(
+        module: Module,
+        finished_functions: BoxedSlice<DefinedFuncIndex, *const VMFunctionBody>,
+        imports: Imports,
+        data_initializers: Box<[OwnedDataInitializer]>,
+    ) -> Self {
+        Self {
+            module: Rc::new(module),
+            finished_functions,
+            imports,
+            data_initializers,
+        }
+    }
+
+    /// Crate an `Instance` from this `CompiledModule`.
+    ///
+    /// Note that if only one instance of this module is needed, it may be more
+    /// efficient to call the top-level `instantiate`, since that avoids copying
+    /// the data initializers.
+    pub fn instantiate(&mut self) -> Result<Box<Instance>, InstantiationError> {
+        let data_initializers = self
+            .data_initializers
+            .iter()
+            .map(|init| DataInitializer {
+                location: init.location.clone(),
+                data: &*init.data,
+            })
+            .collect::<Vec<_>>();
+        Instance::new(
+            Rc::clone(&self.module),
+            self.finished_functions.clone(),
+            self.imports.clone(),
+            &data_initializers,
+        )
+    }
+}
+
+/// Similar to `DataInitializer`, but owns its own copy of the data rather
+/// than holding a slice of the original module.
+pub struct OwnedDataInitializer {
+    /// The location where the initialization is to be performed.
+    location: DataInitializerLocation,
+
+    /// The initialization data.
+    data: Box<[u8]>,
+}
+
+impl OwnedDataInitializer {
+    fn new(borrowed: &DataInitializer) -> Self {
+        Self {
+            location: borrowed.location.clone(),
+            data: borrowed.data.to_vec().into_boxed_slice(),
+        }
+    }
+}
+
+/// Create a new `Instance` by compiling the wasm module in `data` and instatiating it.
+///
+/// This is equivalent to createing a `CompiledModule` and calling `instantiate()` on it,
+/// but avoids creating an intermediate copy of the data initializers.
+pub fn instantiate(
+    compiler: &mut Compiler,
+    data: &[u8],
+    resolver: &mut Resolver,
+) -> Result<Box<Instance>, SetupError> {
+    let raw = RawCompiledModule::new(compiler, data, resolver)?;
+
+    Instance::new(
+        Rc::new(raw.module),
+        raw.finished_functions,
+        raw.imports,
+        &*raw.data_initializers,
+    )
+    .map_err(SetupError::Instantiate)
+}