wasmtime: Enable {extern,func}ref globals in the API

Author: fitzgen

crates/runtime/src/lib.rs

@@ -67,3 +67,14 @@ pub fn ref_type() -> wasmtime_environ::ir::Type {
         unreachable!()
     }
 }
+
+/// The Cranelift IR type used for pointer types for this target architecture.
+pub fn pointer_type() -> wasmtime_environ::ir::Type {
+    if cfg!(target_pointer_width = "32") {
+        wasmtime_environ::ir::types::I32
+    } else if cfg!(target_pointer_width = "64") {
+        wasmtime_environ::ir::types::I64
+    } else {
+        unreachable!()
+    }
+}

crates/runtime/src/sig_registry.rs

@@ -65,4 +65,18 @@ impl SignatureRegistry {
     pub fn lookup_wasm(&self, idx: VMSharedSignatureIndex) -> Option<WasmFuncType> {
         self.index2wasm.get(&idx).cloned()
     }
+
+    /// Looks up both a shared Wasm function signature and its associated native
+    /// `ir::Signature` within this registry.
+    ///
+    /// Note that for this operation to be semantically correct the `idx` must
+    /// have previously come from a call to `register` of this same object.
+    pub fn lookup_wasm_and_native_signatures(
+        &self,
+        idx: VMSharedSignatureIndex,
+    ) -> Option<(WasmFuncType, ir::Signature)> {
+        let wasm = self.lookup_wasm(idx)?;
+        let native = self.lookup_native(idx)?;
+        Some((wasm, native))
+    }
 }

crates/wasmtime/src/func.rs

@@ -9,7 +9,8 @@ use std::panic::{self, AssertUnwindSafe};
 use std::ptr::{self, NonNull};
 use std::rc::Weak;
 use wasmtime_runtime::{
-    raise_user_trap, Export, InstanceHandle, VMContext, VMFunctionBody, VMTrampoline,
+    raise_user_trap, Export, InstanceHandle, VMContext, VMFunctionBody, VMSharedSignatureIndex,
+    VMTrampoline,
 };
 
 /// A WebAssembly function which can be called.
@@ -486,19 +487,20 @@ impl Func {
         func.into_func(store)
     }
 
+    pub(crate) fn sig_index(&self) -> VMSharedSignatureIndex {
+        unsafe { self.export.anyfunc.as_ref().type_index }
+    }
+
     /// Returns the underlying wasm type that this `Func` has.
     pub fn ty(&self) -> FuncType {
         // Signatures should always be registered in the store's registry of
         // shared signatures, so we should be able to unwrap safely here.
-        let sig = self
-            .instance
-            .store
-            .lookup_signature(unsafe { self.export.anyfunc.as_ref().type_index });
+        let wft = self.instance.store.lookup_signature(self.sig_index());
 
         // This is only called with `Export::Function`, and since it's coming
         // from wasmtime_runtime itself we should support all the types coming
         // out of it, so assert such here.
-        FuncType::from_wasm_func_type(&sig).expect("core wasm signature should be supported")
+        FuncType::from_wasm_func_type(&wft).expect("core wasm signature should be supported")
     }
 
     /// Returns the number of parameters that this function takes.

crates/wasmtime/src/runtime.rs

@@ -900,6 +900,17 @@ impl Store {
             .expect("failed to lookup signature")
     }
 
+    pub(crate) fn lookup_wasm_and_native_signatures(
+        &self,
+        sig_index: VMSharedSignatureIndex,
+    ) -> (wasm::WasmFuncType, ir::Signature) {
+        self.inner
+            .signatures
+            .borrow()
+            .lookup_wasm_and_native_signatures(sig_index)
+            .expect("failed to lookup signature")
+    }
+
     pub(crate) fn register_signature(
         &self,
         wasm_sig: wasm::WasmFuncType,

crates/wasmtime/src/trampoline/create_handle.rs

@@ -7,11 +7,11 @@ use std::any::Any;
 use std::collections::HashMap;
 use std::sync::Arc;
 use wasmtime_environ::entity::PrimaryMap;
-use wasmtime_environ::wasm::DefinedFuncIndex;
+use wasmtime_environ::wasm::{DefinedFuncIndex, FuncIndex};
 use wasmtime_environ::Module;
 use wasmtime_runtime::{
     Imports, InstanceHandle, StackMapRegistry, VMExternRefActivationsTable, VMFunctionBody,
-    VMSharedSignatureIndex, VMTrampoline,
+    VMFunctionImport, VMSharedSignatureIndex, VMTrampoline,
 };
 
 pub(crate) fn create_handle(
@@ -20,9 +20,10 @@ pub(crate) fn create_handle(
     finished_functions: PrimaryMap<DefinedFuncIndex, *mut [VMFunctionBody]>,
     trampolines: HashMap<VMSharedSignatureIndex, VMTrampoline>,
     state: Box<dyn Any>,
+    func_imports: PrimaryMap<FuncIndex, VMFunctionImport>,
 ) -> Result<StoreInstanceHandle> {
     let imports = Imports::new(
-        PrimaryMap::new(),
+        func_imports,
         PrimaryMap::new(),
         PrimaryMap::new(),
         PrimaryMap::new(),

crates/wasmtime/src/trampoline/func.rs

@@ -3,7 +3,7 @@
 use super::create_handle::create_handle;
 use crate::trampoline::StoreInstanceHandle;
 use crate::{FuncType, Store, Trap};
-use anyhow::{bail, Result};
+use anyhow::Result;
 use std::any::Any;
 use std::cmp;
 use std::collections::HashMap;
@@ -211,10 +211,7 @@ pub fn create_handle_with_function(
     let isa = store.engine().config().target_isa();
 
     let pointer_type = isa.pointer_type();
-    let sig = match ft.get_wasmtime_signature(pointer_type) {
-        Some(sig) => sig,
-        None => bail!("not a supported core wasm signature {:?}", ft),
-    };
+    let sig = ft.get_wasmtime_signature(pointer_type);
 
     let mut fn_builder_ctx = FunctionBuilderContext::new();
     let mut module = Module::new();
@@ -259,6 +256,7 @@ pub fn create_handle_with_function(
         finished_functions,
         trampolines,
         Box::new(trampoline_state),
+        PrimaryMap::new(),
     )
     .map(|instance| (instance, trampoline))
 }
@@ -277,10 +275,7 @@ pub unsafe fn create_handle_with_raw_function(
     };
 
     let pointer_type = isa.pointer_type();
-    let sig = match ft.get_wasmtime_signature(pointer_type) {
-        Some(sig) => sig,
-        None => bail!("not a supported core wasm signature {:?}", ft),
-    };
+    let sig = ft.get_wasmtime_signature(pointer_type);
 
     let mut module = Module::new();
     let mut finished_functions = PrimaryMap::new();
@@ -298,5 +293,12 @@ pub unsafe fn create_handle_with_raw_function(
     let sig_id = store.register_signature(ft.to_wasm_func_type(), sig);
     trampolines.insert(sig_id, trampoline);
 
-    create_handle(module, store, finished_functions, trampolines, state)
+    create_handle(
+        module,
+        store,
+        finished_functions,
+        trampolines,
+        state,
+        PrimaryMap::new(),
+    )
 }

crates/wasmtime/src/trampoline/global.rs

@@ -1,17 +1,19 @@
 use super::create_handle::create_handle;
 use crate::trampoline::StoreInstanceHandle;
 use crate::{GlobalType, Mutability, Store, Val};
-use anyhow::{bail, Result};
+use anyhow::Result;
 use wasmtime_environ::entity::PrimaryMap;
 use wasmtime_environ::{wasm, EntityIndex, Module};
+use wasmtime_runtime::VMFunctionImport;
 
 pub fn create_global(store: &Store, gt: &GlobalType, val: Val) -> Result<StoreInstanceHandle> {
+    let mut module = Module::new();
+    let mut func_imports = PrimaryMap::new();
+    let mut externref_init = None;
+
     let global = wasm::Global {
         wasm_ty: gt.content().to_wasm_type(),
-        ty: match gt.content().get_wasmtime_type() {
-            Some(t) => t,
-            None => bail!("cannot support {:?} as a wasm global type", gt.content()),
-        },
+        ty: gt.content().get_wasmtime_type(),
         mutability: match gt.mutability() {
             Mutability::Const => false,
             Mutability::Var => true,
@@ -21,10 +23,42 @@ pub fn create_global(store: &Store, gt: &GlobalType, val: Val) -> Result<StoreIn
             Val::I64(i) => wasm::GlobalInit::I64Const(i),
             Val::F32(f) => wasm::GlobalInit::F32Const(f),
             Val::F64(f) => wasm::GlobalInit::F64Const(f),
+            Val::ExternRef(None) | Val::FuncRef(None) => wasm::GlobalInit::RefNullConst,
+            Val::ExternRef(Some(x)) => {
+                // There is no `GlobalInit` variant for using an existing
+                // `externref` that isn't an import (because Wasm can't create
+                // an `externref` by itself). Therefore, initialize the global
+                // as null, and then monkey patch it after instantiation below.
+                externref_init = Some(x);
+                wasm::GlobalInit::RefNullConst
+            }
+            Val::FuncRef(Some(f)) => {
+                // Add a function import to the stub module, and then initialize
+                // our global with a `ref.func` to grab that imported function.
+                let shared_sig_index = f.sig_index();
+                let local_sig_index = module
+                    .local
+                    .signatures
+                    .push(store.lookup_wasm_and_native_signatures(shared_sig_index));
+                let func_index = module.local.functions.push(local_sig_index);
+                module.local.num_imported_funcs = 1;
+                module
+                    .imports
+                    .push(("".into(), "".into(), EntityIndex::Function(func_index)));
+
+                let f = f.caller_checked_anyfunc();
+                let f = unsafe { f.as_ref() };
+                func_imports.push(VMFunctionImport {
+                    body: f.func_ptr,
+                    vmctx: f.vmctx,
+                });
+
+                wasm::GlobalInit::RefFunc(func_index)
+            }
             _ => unimplemented!("create_global for {:?}", gt),
         },
     };
-    let mut module = Module::new();
+
     let global_id = module.local.globals.push(global);
     module
         .exports
@@ -35,6 +69,17 @@ pub fn create_global(store: &Store, gt: &GlobalType, val: Val) -> Result<StoreIn
         PrimaryMap::new(),
         Default::default(),
         Box::new(()),
+        func_imports,
     )?;
+
+    if let Some(x) = externref_init {
+        match handle.lookup("global").unwrap() {
+            wasmtime_runtime::Export::Global(g) => unsafe {
+                *(*g.definition).as_externref_mut() = Some(x.inner);
+            },
+            _ => unreachable!(),
+        }
+    }
+
     Ok(handle)
 }

crates/wasmtime/src/trampoline/memory.rs

@@ -35,6 +35,7 @@ pub fn create_handle_with_memory(
         PrimaryMap::new(),
         Default::default(),
         Box::new(()),
+        PrimaryMap::new(),
     )
 }
 

crates/wasmtime/src/trampoline/table.rs

@@ -32,5 +32,6 @@ pub fn create_handle_with_table(store: &Store, table: &TableType) -> Result<Stor
         PrimaryMap::new(),
         Default::default(),
         Box::new(()),
+        PrimaryMap::new(),
     )
 }

crates/wasmtime/src/types.rs

@@ -99,15 +99,15 @@ impl ValType {
         }
     }
 
-    pub(crate) fn get_wasmtime_type(&self) -> Option<ir::Type> {
+    pub(crate) fn get_wasmtime_type(&self) -> ir::Type {
         match self {
-            ValType::I32 => Some(ir::types::I32),
-            ValType::I64 => Some(ir::types::I64),
-            ValType::F32 => Some(ir::types::F32),
-            ValType::F64 => Some(ir::types::F64),
-            ValType::V128 => Some(ir::types::I8X16),
-            ValType::ExternRef => Some(wasmtime_runtime::ref_type()),
-            _ => None,
+            ValType::I32 => ir::types::I32,
+            ValType::I64 => ir::types::I64,
+            ValType::F32 => ir::types::F32,
+            ValType::F64 => ir::types::F64,
+            ValType::V128 => ir::types::I8X16,
+            ValType::ExternRef => wasmtime_runtime::ref_type(),
+            ValType::FuncRef => wasmtime_runtime::pointer_type(),
         }
     }
 
@@ -248,34 +248,32 @@ impl FuncType {
         }
     }
 
-    /// Returns `Some` if this function signature was compatible with cranelift,
-    /// or `None` if one of the types/results wasn't supported or compatible
-    /// with cranelift.
-    pub(crate) fn get_wasmtime_signature(&self, pointer_type: ir::Type) -> Option<ir::Signature> {
+    /// Get the Cranelift-compatible function signature.
+    pub(crate) fn get_wasmtime_signature(&self, pointer_type: ir::Type) -> ir::Signature {
         use wasmtime_environ::ir::{AbiParam, ArgumentPurpose, Signature};
         use wasmtime_jit::native;
         let call_conv = native::call_conv();
         let mut params = self
             .params
             .iter()
-            .map(|p| p.get_wasmtime_type().map(AbiParam::new))
-            .collect::<Option<Vec<_>>>()?;
+            .map(|p| AbiParam::new(p.get_wasmtime_type()))
+            .collect::<Vec<_>>();
         let returns = self
             .results
             .iter()
-            .map(|p| p.get_wasmtime_type().map(AbiParam::new))
-            .collect::<Option<Vec<_>>>()?;
+            .map(|p| AbiParam::new(p.get_wasmtime_type()))
+            .collect::<Vec<_>>();
         params.insert(
             0,
             AbiParam::special(pointer_type, ArgumentPurpose::VMContext),
         );
         params.insert(1, AbiParam::new(pointer_type));
 
-        Some(Signature {
+        Signature {
             params,
             returns,
             call_conv,
-        })
+        }
     }
 
     /// Returns `None` if any types in the signature can't be converted to the