Bug 1540105 - Remove some unnecessary uses of PreBarriered<> and tidy Barrier.h r=sfink

This removes a couple of unnecessary uses of Prebarriered<> and improves comments in places where it is required. I removed a bunch of unused typesdefs from Barrier.h and tidied up.

js/src/builtin/MapObject.h

@@ -25,6 +25,8 @@ namespace js {
  * All values except ropes are hashable as-is.
  */
 class HashableValue {
+  // This is used for map and set keys. We use OrderedHashTableRef to update all
+  // nursery keys on minor GC, so a post barrier is not required here.
   PreBarrieredValue value;
 
  public:

js/src/gc/Barrier.h

@@ -195,37 +195,10 @@
  */
 
 class JSFlatString;
-class JSLinearString;
 
 namespace js {
 
-class AccessorShape;
-class ArrayObject;
-class ArgumentsObject;
-class ArrayBufferObjectMaybeShared;
-class ArrayBufferObject;
-class ArrayBufferViewObject;
-class SharedArrayBufferObject;
-class BaseShape;
-class DebugEnvironmentProxy;
-class GlobalObject;
-class LazyScript;
-class ModuleObject;
-class ModuleEnvironmentObject;
-class ModuleNamespaceObject;
 class NativeObject;
-class PlainObject;
-class PropertyName;
-class SavedFrame;
-class EnvironmentObject;
-class ScriptSourceObject;
-class Shape;
-class UnownedBaseShape;
-class ObjectGroup;
-
-namespace jit {
-class JitCode;
-}  // namespace jit
 
 #ifdef DEBUG
 
@@ -399,7 +372,10 @@ class WriteBarrieredBase
  * PreBarriered only automatically handles pre-barriers. Post-barriers must be
  * manually implemented when using this class. GCPtr and HeapPtr should be used
  * in all cases that do not require explicit low-level control of moving
- * behavior, e.g. for HashMap keys.
+ * behavior.
+ *
+ * This class is useful for example for HashMap keys where automatically
+ * updating a moved nursery pointer would break the hash table.
  */
 template <class T>
 class PreBarriered : public WriteBarrieredBase<T> {
@@ -911,9 +887,12 @@ struct DefaultHasher<js::ReadBarriered<T>> : js::ReadBarrieredHasher<T> {};
 
 namespace js {
 
+
 class ArrayObject;
-class ArrayBufferObject;
+class DebugEnvironmentProxy;
 class GlobalObject;
+class ObjectGroup;
+class PropertyName;
 class Scope;
 class ScriptSourceObject;
 class Shape;
@@ -921,63 +900,49 @@ class BaseShape;
 class UnownedBaseShape;
 class WasmInstanceObject;
 class WasmTableObject;
+
 namespace jit {
 class JitCode;
 }  // namespace jit
 
-typedef PreBarriered<JSObject*> PreBarrieredObject;
-typedef PreBarriered<JSScript*> PreBarrieredScript;
-typedef PreBarriered<jit::JitCode*> PreBarrieredJitCode;
-typedef PreBarriered<JSString*> PreBarrieredString;
-typedef PreBarriered<JSAtom*> PreBarrieredAtom;
+using PreBarrieredObject = PreBarriered<JSObject*>;
+using PreBarrieredValue = PreBarriered<Value>;
 
-typedef GCPtr<NativeObject*> GCPtrNativeObject;
-typedef GCPtr<ArrayObject*> GCPtrArrayObject;
-typedef GCPtr<ArrayBufferObjectMaybeShared*> GCPtrArrayBufferObjectMaybeShared;
-typedef GCPtr<ArrayBufferObject*> GCPtrArrayBufferObject;
-typedef GCPtr<BaseShape*> GCPtrBaseShape;
-typedef GCPtr<JSAtom*> GCPtrAtom;
-typedef GCPtr<JSFlatString*> GCPtrFlatString;
-typedef GCPtr<JSFunction*> GCPtrFunction;
-typedef GCPtr<JSLinearString*> GCPtrLinearString;
-typedef GCPtr<JSObject*> GCPtrObject;
-typedef GCPtr<JSScript*> GCPtrScript;
-typedef GCPtr<JSString*> GCPtrString;
-typedef GCPtr<ModuleObject*> GCPtrModuleObject;
-typedef GCPtr<ModuleEnvironmentObject*> GCPtrModuleEnvironmentObject;
-typedef GCPtr<ModuleNamespaceObject*> GCPtrModuleNamespaceObject;
-typedef GCPtr<PlainObject*> GCPtrPlainObject;
-typedef GCPtr<PropertyName*> GCPtrPropertyName;
-typedef GCPtr<Shape*> GCPtrShape;
-typedef GCPtr<UnownedBaseShape*> GCPtrUnownedBaseShape;
-typedef GCPtr<jit::JitCode*> GCPtrJitCode;
-typedef GCPtr<ObjectGroup*> GCPtrObjectGroup;
-typedef GCPtr<Scope*> GCPtrScope;
+using GCPtrNativeObject = GCPtr<NativeObject*>;
+using GCPtrArrayObject = GCPtr<ArrayObject*>;
+using GCPtrBaseShape = GCPtr<BaseShape*>;
+using GCPtrAtom = GCPtr<JSAtom*>;
+using GCPtrFlatString = GCPtr<JSFlatString*>;
+using GCPtrFunction = GCPtr<JSFunction*>;
+using GCPtrObject = GCPtr<JSObject*>;
+using GCPtrScript = GCPtr<JSScript*>;
+using GCPtrString = GCPtr<JSString*>;
+using GCPtrShape = GCPtr<Shape*>;
+using GCPtrUnownedBaseShape = GCPtr<UnownedBaseShape*>;
+using GCPtrObjectGroup = GCPtr<ObjectGroup*>;
+using GCPtrScope = GCPtr<Scope*>;
+using GCPtrValue = GCPtr<Value>;
+using GCPtrId = GCPtr<jsid>;
 
-typedef PreBarriered<Value> PreBarrieredValue;
-typedef GCPtr<Value> GCPtrValue;
+using ImmutablePropertyNamePtr = ImmutableTenuredPtr<PropertyName*>;
+using ImmutableSymbolPtr = ImmutableTenuredPtr<JS::Symbol*>;
 
-typedef PreBarriered<jsid> PreBarrieredId;
-typedef GCPtr<jsid> GCPtrId;
+using ReadBarrieredDebugEnvironmentProxy =
+    ReadBarriered<DebugEnvironmentProxy*>;
+using ReadBarrieredGlobalObject = ReadBarriered<GlobalObject*>;
+using ReadBarrieredObject = ReadBarriered<JSObject*>;
+using ReadBarrieredScript = ReadBarriered<JSScript*>;
+using ReadBarrieredScriptSourceObject = ReadBarriered<ScriptSourceObject*>;
+using ReadBarrieredShape = ReadBarriered<Shape*>;
+using ReadBarrieredJitCode = ReadBarriered<jit::JitCode*>;
+using ReadBarrieredObjectGroup = ReadBarriered<ObjectGroup*>;
+using ReadBarrieredSymbol = ReadBarriered<JS::Symbol*>;
+using ReadBarrieredWasmInstanceObject = ReadBarriered<WasmInstanceObject*>;
+using ReadBarrieredWasmTableObject = ReadBarriered<WasmTableObject*>;
 
-typedef ImmutableTenuredPtr<PropertyName*> ImmutablePropertyNamePtr;
-typedef ImmutableTenuredPtr<JS::Symbol*> ImmutableSymbolPtr;
-
-typedef ReadBarriered<DebugEnvironmentProxy*>
-    ReadBarrieredDebugEnvironmentProxy;
-typedef ReadBarriered<GlobalObject*> ReadBarrieredGlobalObject;
-typedef ReadBarriered<JSObject*> ReadBarrieredObject;
-typedef ReadBarriered<JSFunction*> ReadBarrieredFunction;
-typedef ReadBarriered<JSScript*> ReadBarrieredScript;
-typedef ReadBarriered<ScriptSourceObject*> ReadBarrieredScriptSourceObject;
-typedef ReadBarriered<Shape*> ReadBarrieredShape;
-typedef ReadBarriered<jit::JitCode*> ReadBarrieredJitCode;
-typedef ReadBarriered<ObjectGroup*> ReadBarrieredObjectGroup;
-typedef ReadBarriered<JS::Symbol*> ReadBarrieredSymbol;
-typedef ReadBarriered<WasmInstanceObject*> ReadBarrieredWasmInstanceObject;
-typedef ReadBarriered<WasmTableObject*> ReadBarrieredWasmTableObject;
-
-typedef ReadBarriered<Value> ReadBarrieredValue;
+using HeapPtrJitCode = HeapPtr<jit::JitCode*>;
+using HeapPtrRegExpShared = HeapPtr<RegExpShared*>;
+using HeapPtrValue = HeapPtr<Value>;
 
 namespace detail {
 

js/src/jit/IonCode.h

@@ -150,7 +150,7 @@ class IonIC;
 struct IonScript {
  private:
   // Code pointer containing the actual method.
-  PreBarrieredJitCode method_;
+  HeapPtrJitCode method_;
 
   // Entrypoint for OSR, or nullptr.
   jsbytecode* osrPc_;
@@ -257,6 +257,8 @@ struct IonScript {
     return (SnapshotOffset*)&bottomBuffer()[bailoutTable_];
   }
   PreBarrieredValue* constants() {
+    // Nursery constants are manually barriered in CodeGenerator::link() so a
+    // post barrier is not required..
     return (PreBarrieredValue*)&bottomBuffer()[constantTable_];
   }
   const SafepointIndex* safepointIndices() const {

js/src/jit/JSJitFrameIter.h

@@ -16,6 +16,9 @@
 #include "vm/JSScript.h"
 
 namespace js {
+
+class ArgumentsObject;
+
 namespace jit {
 
 typedef void* CalleeToken;

js/src/vm/ArgumentsObject.h

@@ -15,6 +15,7 @@
 namespace js {
 
 class AbstractFramePtr;
+class ArgumentsObject;
 class ScriptFrameIter;
 
 namespace jit {

js/src/vm/Debugger.h

@@ -1951,7 +1951,10 @@ class Breakpoint {
   BreakpointSite* const site;
 
  private:
-  /* |handler| is marked unconditionally during minor GC. */
+  /*
+   * |handler| is marked unconditionally during minor GC so a post barrier is
+   * not required.
+   */
   js::PreBarrieredObject handler;
 
   /**
@@ -1969,7 +1972,7 @@ class Breakpoint {
 
   Breakpoint* nextInDebugger();
   Breakpoint* nextInSite();
-  const PreBarrieredObject& getHandler() const { return handler; }
+  JSObject* getHandler() const { return handler; }
   PreBarrieredObject& getHandlerRef() { return handler; }
 
   inline WasmBreakpoint* asWasm();

js/src/vm/RegExpObject.h

@@ -153,9 +153,9 @@ class RegExpObject : public NativeObject {
     sharedRef().init(&shared);
   }
 
-  PreBarriered<RegExpShared*>& sharedRef() {
+  HeapPtrRegExpShared& sharedRef() {
     auto& ref = NativeObject::privateRef(PRIVATE_SLOT);
-    return reinterpret_cast<PreBarriered<RegExpShared*>&>(ref);
+    return reinterpret_cast<HeapPtrRegExpShared&>(ref);
   }
 
   static void trace(JSTracer* trc, JSObject* obj);

js/src/vm/Shape.h

@@ -912,7 +912,7 @@ class Shape : public gc::TenuredCell {
 
  protected:
   GCPtrBaseShape base_;
-  PreBarrieredId propid_;
+  GCPtrId propid_;
 
   // Flags that are not modified after the Shape is created. Off-thread Ion
   // compilation can access the immutableFlags word, so we don't want any
@@ -1287,12 +1287,12 @@ class Shape : public gc::TenuredCell {
     mutableFlags = (mutableFlags & ~LINEAR_SEARCHES_MASK) | (count + 1);
   }
 
-  const PreBarrieredId& propid() const {
+  const GCPtrId& propid() const {
     MOZ_ASSERT(!isEmptyShape());
     MOZ_ASSERT(!JSID_IS_VOID(propid_));
     return propid_;
   }
-  PreBarrieredId& propidRef() {
+  GCPtrId& propidRef() {
     MOZ_ASSERT(!JSID_IS_VOID(propid_));
     return propid_;
   }

js/src/wasm/WasmJS.h

@@ -25,6 +25,7 @@
 
 namespace js {
 
+class ArrayBufferObjectMaybeShared;
 class GlobalObject;
 class StructTypeDescr;
 class TypedArrayObject;