wasm: Add support for passive data and element segments (#1389)

This is part of the bulk memory and reference types proposals.

cranelift/wasm/src/environ/spec.rs

@@ -8,7 +8,8 @@
 
 use crate::state::{FuncTranslationState, ModuleTranslationState};
 use crate::translation_utils::{
-    FuncIndex, Global, GlobalIndex, Memory, MemoryIndex, SignatureIndex, Table, TableIndex,
+    FuncIndex, Global, GlobalIndex, Memory, MemoryIndex, PassiveDataIndex, PassiveElemIndex,
+    SignatureIndex, Table, TableIndex,
 };
 use core::convert::From;
 use cranelift_codegen::cursor::FuncCursor;
@@ -600,6 +601,29 @@ pub trait ModuleEnvironment<'data>: TargetEnvironment {
         elements: Box<[FuncIndex]>,
     ) -> WasmResult<()>;
 
+    /// Declare a passive element segment.
+    fn declare_passive_element(
+        &mut self,
+        index: PassiveElemIndex,
+        elements: Box<[FuncIndex]>,
+    ) -> WasmResult<()>;
+
+    /// Provides the number of passive data segments up front.
+    ///
+    /// By default this does nothing, but implementations may use this to
+    /// pre-allocate memory if desired.
+    fn reserve_passive_data(&mut self, count: u32) -> WasmResult<()> {
+        let _ = count;
+        Ok(())
+    }
+
+    /// Declare a passive data segment.
+    fn declare_passive_data(
+        &mut self,
+        data_index: PassiveDataIndex,
+        data: &'data [u8],
+    ) -> WasmResult<()>;
+
     /// Provides the contents of a function body.
     ///
     /// Note there's no `reserve_function_bodies` function because the number of