Implement data.drop and memory.init and get the rest of the bulk memory spec tests passing (#1264)

* Enable the already-passing `bulk-memoryoperations/imports.wast` test

* Implement support for the `memory.init` instruction and passive data

This adds support for passive data segments and the `memory.init` instruction
from the bulk memory operations proposal. Passive data segments are stored on
the Wasm module and then `memory.init` instructions copy their contents into
memory.

* Implement the `data.drop` instruction

This allows wasm modules to deallocate passive data segments that it doesn't
need anymore. We keep track of which segments have not been dropped on an
`Instance` and when dropping them, remove the entry from the instance's hash
map. The module always needs all of the segments for new instantiations.

* Enable final bulk memory operations spec test

This requires special casing an expected error message for an `assert_trap`,
since the expected error message contains the index of an uninitialized table
element, but our trap implementation doesn't save that diagnostic information
and shepherd it out.

crates/environ/src/module.rs

@@ -5,13 +5,17 @@ use crate::WASM_MAX_PAGES;
 use cranelift_codegen::ir;
 use cranelift_entity::{EntityRef, PrimaryMap};
 use cranelift_wasm::{
-    DefinedFuncIndex, DefinedGlobalIndex, DefinedMemoryIndex, DefinedTableIndex, ElemIndex,
-    FuncIndex, Global, GlobalIndex, Memory, MemoryIndex, SignatureIndex, Table, TableIndex,
+    DataIndex, DefinedFuncIndex, DefinedGlobalIndex, DefinedMemoryIndex, DefinedTableIndex,
+    ElemIndex, FuncIndex, Global, GlobalIndex, Memory, MemoryIndex, SignatureIndex, Table,
+    TableIndex,
 };
 use indexmap::IndexMap;
 use more_asserts::assert_ge;
 use std::collections::HashMap;
-use std::sync::atomic::{AtomicUsize, Ordering::SeqCst};
+use std::sync::{
+    atomic::{AtomicUsize, Ordering::SeqCst},
+    Arc,
+};
 
 /// A WebAssembly table initializer.
 #[derive(Clone, Debug, Hash)]
@@ -168,6 +172,9 @@ pub struct Module {
     /// WebAssembly passive elements.
     pub passive_elements: HashMap<ElemIndex, Box<[FuncIndex]>>,
 
+    /// WebAssembly passive data segments.
+    pub passive_data: HashMap<DataIndex, Arc<[u8]>>,
+
     /// WebAssembly table initializers.
     pub func_names: HashMap<FuncIndex, String>,
 }
@@ -223,6 +230,7 @@ impl Module {
             start_func: None,
             table_elements: Vec::new(),
             passive_elements: HashMap::new(),
+            passive_data: HashMap::new(),
             func_names: HashMap::new(),
             local: ModuleLocal {
                 num_imported_funcs: 0,