Bug 1533755 - Use RefPtr for SharedScriptData pointers. r=jandem

Leave manual refcounting in the ScriptDataTable for now since it
requires a bit of care to make the automatic types do the right thing
when sweeping.

Differential Revision: https://phabricator.services.mozilla.com/D22718

--HG--
extra : moz-landing-system : lando

js/src/vm/JSScript.cpp

@@ -2908,40 +2908,17 @@ SharedScriptData* js::SharedScriptData::new_(JSContext* cx, uint32_t codeLength,
 
 inline js::ScriptBytecodeHasher::Lookup::Lookup(SharedScriptData* data)
     : scriptData(data),
-      hash(mozilla::HashBytes(scriptData->data(), scriptData->dataLength())) {
-  scriptData->incRefCount();
-}
-
-inline js::ScriptBytecodeHasher::Lookup::~Lookup() {
-  scriptData->decRefCount();
-}
+      hash(mozilla::HashBytes(scriptData->data(), scriptData->dataLength())) {}
 
 bool JSScript::createSharedScriptData(JSContext* cx, uint32_t codeLength,
                                       uint32_t noteLength, uint32_t natoms) {
-  MOZ_ASSERT(!scriptData());
-  SharedScriptData* ssd =
-      SharedScriptData::new_(cx, codeLength, noteLength, natoms);
-  if (!ssd) {
-    return false;
-  }
-
-  setScriptData(ssd);
-  return true;
-}
-
-void JSScript::freeScriptData() {
-  if (scriptData_) {
-    scriptData_->decRefCount();
-    scriptData_ = nullptr;
-  }
-}
-
-void JSScript::setScriptData(js::SharedScriptData* data) {
   MOZ_ASSERT(!scriptData_);
-  scriptData_ = data;
-  scriptData_->incRefCount();
+  scriptData_ = SharedScriptData::new_(cx, codeLength, noteLength, natoms);
+  return !!scriptData_;
 }
 
+void JSScript::freeScriptData() { scriptData_ = nullptr; }
+
 /*
  * Takes ownership of its *ssd parameter and either adds it into the runtime's
  * ScriptDataTable or frees it if a matching entry already exists.
@@ -2962,20 +2939,20 @@ bool JSScript::shareScriptData(JSContext* cx) {
   ScriptDataTable::AddPtr p = cx->scriptDataTable(lock).lookupForAdd(lookup);
   if (p) {
     MOZ_ASSERT(ssd != *p);
-    freeScriptData();
-    setScriptData(*p);
+    scriptData_ = *p;
   } else {
     if (!cx->scriptDataTable(lock).add(p, ssd)) {
-      freeScriptData();
       ReportOutOfMemory(cx);
       return false;
     }
 
     // Being in the table counts as a reference on the script data.
-    scriptData()->incRefCount();
+    ssd->AddRef();
   }
 
-  MOZ_ASSERT(scriptData()->refCount() >= 2);
+  // Refs: JSScript, Lookup, ScriptDataTable
+  MOZ_ASSERT(scriptData()->refCount() >= 3);
+
   return true;
 }
 
@@ -2989,7 +2966,7 @@ void js::SweepScriptData(JSRuntime* rt) {
   for (ScriptDataTable::Enum e(table); !e.empty(); e.popFront()) {
     SharedScriptData* scriptData = e.front();
     if (scriptData->refCount() == 1) {
-      scriptData->decRefCount();
+      scriptData->Release();
       e.removeFront();
     }
   }
@@ -3740,9 +3717,7 @@ void JSScript::finalize(FreeOp* fop) {
     fop->free_(data_);
   }
 
-  if (scriptData_) {
-    scriptData_->decRefCount();
-  }
+  freeScriptData();
 
   // In most cases, our LazyScript's script pointer will reference this
   // script, and thus be nulled out by normal weakref processing. However, if
@@ -4243,7 +4218,7 @@ JSScript* js::detail::CopyScript(JSContext* cx, HandleScript src,
   if (cx->zone() != src->zoneFromAnyThread()) {
     src->scriptData()->markForCrossZone(cx);
   }
-  dst->setScriptData(src->scriptData());
+  dst->scriptData_ = src->scriptData();
 
   return dst;
 }

js/src/vm/JSScript.h

@@ -14,6 +14,7 @@
 #include "mozilla/Maybe.h"
 #include "mozilla/MaybeOneOf.h"
 #include "mozilla/MemoryReporting.h"
+#include "mozilla/RefPtr.h"
 #include "mozilla/Span.h"
 #include "mozilla/UniquePtr.h"
 #include "mozilla/Utf8.h"
@@ -1478,8 +1479,8 @@ class SharedScriptData {
                                 uint32_t srcnotesLength, uint32_t natoms);
 
   uint32_t refCount() const { return refCount_; }
-  void incRefCount() { refCount_++; }
-  void decRefCount() {
+  void AddRef() { refCount_++; }
+  void Release() {
     MOZ_ASSERT(refCount_ != 0);
     uint32_t remain = --refCount_;
     if (remain == 0) {
@@ -1543,12 +1544,11 @@ struct ScriptBytecodeHasher {
   class Lookup {
     friend struct ScriptBytecodeHasher;
 
-    SharedScriptData* scriptData;
+    RefPtr<SharedScriptData> scriptData;
     HashNumber hash;
 
    public:
     explicit Lookup(SharedScriptData* data);
-    ~Lookup();
   };
 
   static HashNumber hash(const Lookup& l) { return l.hash; }
@@ -1598,7 +1598,7 @@ class JSScript : public js::gc::TenuredCell {
   uint8_t* jitCodeSkipArgCheck_ = nullptr;
 
   // Shareable script data
-  js::SharedScriptData* scriptData_ = nullptr;
+  RefPtr<js::SharedScriptData> scriptData_ = {};
 
   // Unshared variable-length data
   js::PrivateScriptData* data_ = nullptr;
@@ -2537,7 +2537,6 @@ class JSScript : public js::gc::TenuredCell {
                               uint32_t noteLength, uint32_t natoms);
   bool shareScriptData(JSContext* cx);
   void freeScriptData();
-  void setScriptData(js::SharedScriptData* data);
 
  public:
   uint32_t getWarmUpCount() const { return warmUpCount; }