Bug 1505690 - Replace JSScript::vtuneMethodId_ with a HashMap. r=sstangl

MOZ_VTUNE is defined on Nightly (because of --enable-profiling). With the HashMap
we only have some memory/perf overhead when we're actually using VTune's JIT code
profiler.

Differential Revision: https://phabricator.services.mozilla.com/D11292

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

js/src/vm/JSScript.cpp

@@ -3172,10 +3172,6 @@ JSScript::JSScript(JS::Realm* realm, uint8_t* stubEntry, HandleObject sourceObje
     MOZ_ASSERT(sourceStart <= sourceEnd);
     MOZ_ASSERT(sourceEnd <= toStringEnd);
 
-#ifdef MOZ_VTUNE
-    vtuneMethodId_ = vtune::GenerateUniqueMethodID();
-#endif
-
     setSourceObject(sourceObject);
 }
 
@@ -3225,6 +3221,33 @@ JSScript::Create(JSContext* cx, const ReadOnlyCompileOptions& options,
     return script;
 }
 
+#ifdef MOZ_VTUNE
+uint32_t
+JSScript::vtuneMethodID()
+{
+    if (!realm()->scriptVTuneIdMap) {
+        auto map = MakeUnique<ScriptVTuneIdMap>();
+        if (!map) {
+            MOZ_CRASH("Failed to allocate ScriptVTuneIdMap");
+        }
+
+        realm()->scriptVTuneIdMap = std::move(map);
+    }
+
+    ScriptVTuneIdMap::AddPtr p = realm()->scriptVTuneIdMap->lookupForAdd(this);
+    if (p) {
+        return p->value();
+    }
+
+    uint32_t id = vtune::GenerateUniqueMethodID();
+    if (!realm()->scriptVTuneIdMap->add(p, this, id)) {
+        MOZ_CRASH("Failed to add vtune method id");
+    }
+
+    return id;
+}
+#endif
+
 bool
 JSScript::initScriptName(JSContext* cx)
 {
@@ -3614,6 +3637,13 @@ JSScript::finalize(FreeOp* fop)
     destroyScriptCounts();
     destroyDebugScript(fop);
 
+#ifdef MOZ_VTUNE
+    if (realm()->scriptVTuneIdMap) {
+        // Note: we should only get here if the VTune JIT profiler is running.
+        realm()->scriptVTuneIdMap->remove(this);
+    }
+#endif
+
     if (data_) {
         JS_POISON(data_, 0xdb, computedSizeOfData(), MemCheckKind::MakeNoAccess);
         fop->free_(data_);

js/src/vm/JSScript.h

@@ -219,6 +219,13 @@ using ScriptNameMap = HashMap<JSScript*,
                               DefaultHasher<JSScript*>,
                               SystemAllocPolicy>;
 
+#ifdef MOZ_VTUNE
+using ScriptVTuneIdMap = HashMap<JSScript*,
+                                 uint32_t,
+                                 DefaultHasher<JSScript*>,
+                                 SystemAllocPolicy>;
+#endif
+
 class DebugScript
 {
     friend class ::JSScript;
@@ -1626,12 +1633,6 @@ class JSScript : public js::gc::TenuredCell
     uint32_t toStringStart_ = 0;
     uint32_t toStringEnd_ = 0;
 
-#ifdef MOZ_VTUNE
-    // Unique Method ID passed to the VTune profiler, or 0 if unset.
-    // Allows attribution of different jitcode to the same source script.
-    uint32_t vtuneMethodId_ = 0;
-#endif
-
     // Number of times the script has been called or has had backedges taken.
     // When running in ion, also increased for any inlined scripts. Reset if
     // the script's JIT code is forcibly discarded.
@@ -1705,6 +1706,8 @@ class JSScript : public js::gc::TenuredCell
         // See comments below.
         ArgsHasVarBinding = 1 << 21,
     };
+    // Note: don't make this a bitfield! It makes it hard to read these flags
+    // from JIT code.
     uint32_t immutableFlags_ = 0;
 
     // Mutable flags typically store information about runtime or deoptimization
@@ -1775,6 +1778,8 @@ class JSScript : public js::gc::TenuredCell
         HideScriptFromDebugger = 1 << 19,
     };
   private:
+    // Note: don't make this a bitfield! It makes it hard to read these flags
+    // from JIT code.
     uint32_t mutableFlags_ = 0;
 
     // 16-bit fields.
@@ -2394,7 +2399,9 @@ class JSScript : public js::gc::TenuredCell
     const char* maybeForwardedFilename() const { return maybeForwardedScriptSource()->filename(); }
 
 #ifdef MOZ_VTUNE
-    uint32_t vtuneMethodID() const { return vtuneMethodId_; }
+    // Unique Method ID passed to the VTune profiler. Allows attribution of
+    // different jitcode to the same source script.
+    uint32_t vtuneMethodID();
 #endif
 
   public:

js/src/vm/Realm.cpp

@@ -405,6 +405,10 @@ Realm::finishRoots()
 
     clearScriptCounts();
     clearScriptNames();
+
+#ifdef MOZ_VTUNE
+    scriptVTuneIdMap.reset();
+#endif
 }
 
 void
@@ -588,6 +592,17 @@ Realm::fixupScriptMapsAfterMovingGC()
             }
         }
     }
+
+#ifdef MOZ_VTUNE
+    if (scriptVTuneIdMap) {
+        for (ScriptVTuneIdMap::Enum e(*scriptVTuneIdMap); !e.empty(); e.popFront()) {
+            JSScript* script = e.front().key();
+            if (!IsAboutToBeFinalizedUnbarriered(&script) && script != e.front().key()) {
+                e.rekeyFront(script);
+            }
+        }
+    }
+#endif
 }
 
 #ifdef JSGC_HASH_TABLE_CHECKS
@@ -630,6 +645,18 @@ Realm::checkScriptMapsAfterMovingGC()
             MOZ_RELEASE_ASSERT(ptr.found() && &*ptr == &r.front());
         }
     }
+
+# ifdef MOZ_VTUNE
+    if (scriptVTuneIdMap) {
+        for (auto r = scriptVTuneIdMap->all(); !r.empty(); r.popFront()) {
+            JSScript* script = r.front().key();
+            MOZ_ASSERT(script->realm() == this);
+            CheckGCThingAfterMovingGC(script);
+            auto ptr = scriptVTuneIdMap->lookup(script);
+            MOZ_RELEASE_ASSERT(ptr.found() && &*ptr == &r.front());
+        }
+    }
+# endif // MOZ_VTUNE
 }
 #endif
 

js/src/vm/Realm.h

@@ -421,6 +421,9 @@ class JS::Realm : public JS::shadow::Realm
     js::UniquePtr<js::ScriptCountsMap> scriptCountsMap;
     js::UniquePtr<js::ScriptNameMap> scriptNameMap;
     js::UniquePtr<js::DebugScriptMap> debugScriptMap;
+#ifdef MOZ_VTUNE
+    js::UniquePtr<js::ScriptVTuneIdMap> scriptVTuneIdMap;
+#endif
 
     /*
      * Lazily initialized script source object to use for scripts cloned

js/src/vtune/VTuneWrapper.cpp

@@ -119,7 +119,7 @@ MarkRegExp(const js::jit::JitCode* code, bool match_only)
 }
 
 void
-MarkScript(const js::jit::JitCode* code, const JSScript* script, const char* module)
+MarkScript(const js::jit::JitCode* code, JSScript* script, const char* module)
 {
     if (!IsProfilingActive())
         return;

js/src/vtune/VTuneWrapper.h

@@ -33,7 +33,7 @@ void MarkStub(const js::jit::JitCode* code, const char* name);
 void MarkRegExp(const js::jit::JitCode* code, bool match_only);
 
 void MarkScript(const js::jit::JitCode* code,
-                const JSScript* script,
+                JSScript* script,
                 const char* module);
 
 void MarkWasm(unsigned methodId,