Bug 1824904 - part 3: add some division markers to WasmTypeDef.h. r=rhunt.

WasmTypeDef.h contains all the key data types for the wasm-gc extension.
These are arranged more or less in a def-before-use ordering, which is good.
But the file is still a bit hard to navigate.  This patch adds dividing
comments, and a few in WasmTypeDef.cpp too.  No functional change.

Differential Revision: https://phabricator.services.mozilla.com/D174062

js/src/wasm/WasmTypeDef.cpp

@@ -70,6 +70,9 @@ using mozilla::IsPowerOfTwo;
 // to the pointer representation.
 //
 
+//=========================================================================
+// ImmediateType
+
 // ImmediateType is 32-bits to ensure it's easy to materialize the constant
 // on all platforms.
 using ImmediateType = uint32_t;
@@ -212,6 +215,9 @@ static ImmediateType EncodeImmediateFuncType(const FuncType& funcType) {
   return immediate;
 }
 
+//=========================================================================
+// FuncType
+
 void FuncType::initImmediateTypeId() {
   if (!IsImmediateFuncType(*this)) {
     immediateTypeId_ = NO_IMMEDIATE_TYPE_ID;
@@ -237,6 +243,9 @@ size_t FuncType::sizeOfExcludingThis(MallocSizeOf mallocSizeOf) const {
   return args_.sizeOfExcludingThis(mallocSizeOf);
 }
 
+//=========================================================================
+// StructType and StructLayout
+
 static inline CheckedInt32 RoundUpToAlignment(CheckedInt32 address,
                                               uint32_t align) {
   MOZ_ASSERT(IsPowerOfTwo(align));
@@ -352,6 +361,9 @@ size_t TypeDef::sizeOfExcludingThis(MallocSizeOf mallocSizeOf) const {
   return 0;
 }
 
+//=========================================================================
+// SuperTypeVector
+
 /* static */
 size_t SuperTypeVector::offsetOfTypeDefInVector(uint32_t typeDefDepth) {
   return offsetof(SuperTypeVector, types_) + sizeof(void*) * typeDefDepth;
@@ -439,6 +451,9 @@ const SuperTypeVector* SuperTypeVector::createMultipleForRecGroup(
   return firstVector;
 }
 
+//=========================================================================
+// TypeIdSet and TypeContext
+
 struct RecGroupHashPolicy {
   using Lookup = const SharedRecGroup&;
 

js/src/wasm/WasmTypeDef.h

@@ -39,6 +39,9 @@ using mozilla::MallocSizeOf;
 
 class RecGroup;
 
+//=========================================================================
+// Function types
+
 // The FuncType class represents a WebAssembly function signature which takes a
 // list of value types and returns an expression type. The engine uses two
 // in-memory representations of the argument Vector's memory (when elements do
@@ -220,8 +223,9 @@ class FuncType {
   WASM_DECLARE_FRIEND_SERIALIZE(FuncType);
 };
 
-// Structure type.
+//=========================================================================
-//
+// Structure types
+
 // The Module owns a dense array of StructType values that represent the
 // structure types that the module knows about.  It is created from the sparse
 // array of types in the ModuleEnvironment when the Module is created.
@@ -377,7 +381,8 @@ class StructLayout {
   CheckedInt32 close();
 };
 
-// Array type
+//=========================================================================
+// Array types
 
 class ArrayType {
  public:
@@ -446,6 +451,9 @@ WASM_DECLARE_CACHEABLE_POD(ArrayType);
 
 using ArrayTypeVector = Vector<ArrayType, 0, SystemAllocPolicy>;
 
+//=========================================================================
+// SuperTypeVector
+
 // [SMDOC] Super type vector
 //
 // A super type vector is a vector representation of the linked list of super
@@ -552,6 +560,9 @@ class SuperTypeVector {
 // `types_[0]`.
 static_assert(offsetof(SuperTypeVector, types_) == sizeof(SuperTypeVector));
 
+//=========================================================================
+// TypeDef and supporting types
+
 // A tagged container for the various types that can be present in a wasm
 // module's type section.
 
@@ -827,6 +838,9 @@ using TypeDefPtrToIndexMap =
     HashMap<const TypeDef*, uint32_t, PointerHasher<const TypeDef*>,
             SystemAllocPolicy>;
 
+//=========================================================================
+// RecGroup
+
 // A recursion group is a set of type definitions that may refer to each other
 // or to type definitions in another recursion group. There is an ordering
 // restriction on type references such that references across recursion groups
@@ -1032,6 +1046,9 @@ using SharedRecGroup = RefPtr<const RecGroup>;
 using MutableRecGroup = RefPtr<RecGroup>;
 using SharedRecGroupVector = Vector<SharedRecGroup, 0, SystemAllocPolicy>;
 
+//=========================================================================
+// TypeContext
+
 // A type context holds the recursion groups and corresponding type definitions
 // defined in a module.
 class TypeContext : public AtomicRefCounted<TypeContext> {
@@ -1167,6 +1184,9 @@ class TypeContext : public AtomicRefCounted<TypeContext> {
 using SharedTypeContext = RefPtr<const TypeContext>;
 using MutableTypeContext = RefPtr<TypeContext>;
 
+//=========================================================================
+// TypeHandle
+
 // An unambiguous strong reference to a type definition in a specific type
 // context.
 class TypeHandle {
@@ -1190,6 +1210,9 @@ class TypeHandle {
   const TypeDef& def() const { return context_->type(index_); }
 };
 
+//=========================================================================
+// misc
+
 /* static */
 inline uintptr_t TypeDef::forMatch(const TypeDef* typeDef,
                                    const RecGroup* recGroup) {
@@ -1274,6 +1297,7 @@ inline bool RefType::isSubTypeOf(RefType subType, RefType superType) {
   return false;
 }
 
+//=========================================================================
 // [SMDOC] Signatures and runtime types
 //
 // TypeIdDesc describes the runtime representation of a TypeDef suitable for