Implement the remaining valid spec tests.

And lots of other miscellaneous changes. Rename InstanceWorld to
InstancePlus and reorganize its contents. This still isn't a great name,
but at least now it has a clear purpose.

lib/runtime/src/export.rs

@@ -0,0 +1,89 @@
+use cranelift_codegen::ir;
+use cranelift_wasm::Global;
+use vmcontext::{
+    VMContext, VMFunctionBody, VMGlobalDefinition, VMMemoryDefinition, VMTableDefinition,
+};
+use wasmtime_environ::{MemoryPlan, TablePlan};
+
+/// The value of an export passed from one instance to another.
+pub enum Export {
+    /// A function export value.
+    Function {
+        /// The address of the native-code function.
+        address: *const VMFunctionBody,
+        /// The function signature declaration, used for compatibilty checking.
+        signature: ir::Signature,
+        /// Pointer to the containing VMContext.
+        vmctx: *mut VMContext,
+    },
+
+    /// A table export value.
+    Table {
+        /// The address of the table descriptor.
+        address: *mut VMTableDefinition,
+        /// Pointer to the containing VMContext.
+        vmctx: *mut VMContext,
+        /// The table declaration, used for compatibilty checking.
+        table: TablePlan,
+    },
+
+    /// A memory export value.
+    Memory {
+        /// The address of the memory descriptor.
+        address: *mut VMMemoryDefinition,
+        /// Pointer to the containing VMContext.
+        vmctx: *mut VMContext,
+        /// The memory declaration, used for compatibilty checking.
+        memory: MemoryPlan,
+    },
+
+    /// A global export value.
+    Global {
+        /// The address of the global storage.
+        address: *mut VMGlobalDefinition,
+        /// The global declaration, used for compatibilty checking.
+        global: Global,
+    },
+}
+
+impl Export {
+    /// Construct a function export value.
+    pub fn function(
+        address: *const VMFunctionBody,
+        signature: ir::Signature,
+        vmctx: *mut VMContext,
+    ) -> Self {
+        Export::Function {
+            address,
+            signature,
+            vmctx,
+        }
+    }
+
+    /// Construct a table export value.
+    pub fn table(address: *mut VMTableDefinition, vmctx: *mut VMContext, table: TablePlan) -> Self {
+        Export::Table {
+            address,
+            vmctx,
+            table,
+        }
+    }
+
+    /// Construct a memory export value.
+    pub fn memory(
+        address: *mut VMMemoryDefinition,
+        vmctx: *mut VMContext,
+        memory: MemoryPlan,
+    ) -> Self {
+        Export::Memory {
+            address,
+            vmctx,
+            memory,
+        }
+    }
+
+    /// Construct a global export value.
+    pub fn global(address: *mut VMGlobalDefinition, global: Global) -> Self {
+        Export::Global { address, global }
+    }
+}