Bug 1525579 - Add pref for unboxed objects r=jandem

Differential Revision: https://phabricator.services.mozilla.com/D18870

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

js/src/jsapi.cpp

@@ -5565,6 +5565,9 @@ JS_PUBLIC_API void JS_SetGlobalJitCompilerOption(JSContext* cx,
     case JSJITCOMPILER_TRACK_OPTIMIZATIONS:
       jit::JitOptions.disableOptimizationTracking = !value;
       break;
+    case JSJITCOMPILER_UNBOXED_OBJECTS:
+      jit::JitOptions.disableUnboxedObjects = !value;
+      break;
     case JSJITCOMPILER_SPECTRE_INDEX_MASKING:
       jit::JitOptions.spectreIndexMasking = !!value;
       break;

js/src/jsapi.h

@@ -3393,6 +3393,7 @@ extern JS_PUBLIC_API void JS_SetOffthreadIonCompilationEnabled(JSContext* cx,
   Register(FULL_DEBUG_CHECKS, "jit.full-debug-checks") \
   Register(JUMP_THRESHOLD, "jump-threshold") \
   Register(TRACK_OPTIMIZATIONS, "jit.track-optimizations")\
+  Register(UNBOXED_OBJECTS, "unboxed_objects") \
   Register(SIMULATOR_ALWAYS_INTERRUPT, "simulator.always-interrupt") \
   Register(SPECTRE_INDEX_MASKING, "spectre.index-masking") \
   Register(SPECTRE_OBJECT_MITIGATIONS_BARRIERS, "spectre.object-mitigations.barriers") \

js/xpconnect/src/XPCJSContext.cpp

@@ -837,6 +837,9 @@ static void ReloadPrefsCallback(const char* pref, XPCJSContext* xpccx) {
   bool spectreJitToCxxCalls =
       Preferences::GetBool(JS_OPTIONS_DOT_STR "spectre.jit_to_C++_calls");
 
+  bool unboxedObjects =
+      Preferences::GetBool(JS_OPTIONS_DOT_STR "unboxed_objects");
+
   sSharedMemoryEnabled =
       Preferences::GetBool(JS_OPTIONS_DOT_STR "shared_memory");
   sStreamsEnabled = Preferences::GetBool(JS_OPTIONS_DOT_STR "streams");
@@ -922,6 +925,9 @@ static void ReloadPrefsCallback(const char* pref, XPCJSContext* xpccx) {
                                 spectreValueMasking);
   JS_SetGlobalJitCompilerOption(cx, JSJITCOMPILER_SPECTRE_JIT_TO_CXX_CALLS,
                                 spectreJitToCxxCalls);
+
+  JS_SetGlobalJitCompilerOption(cx, JSJITCOMPILER_UNBOXED_OBJECTS,
+                                unboxedObjects);
 }
 
 XPCJSContext::~XPCJSContext() {

modules/libpref/init/all.js

@@ -1458,6 +1458,7 @@ pref("javascript.options.strict",           false);
 #ifdef DEBUG
 pref("javascript.options.strict.debug",     false);
 #endif
+pref("javascript.options.unboxed_objects",  true);
 pref("javascript.options.baselinejit",      true);
 //Duplicated in JitOptions - ensure both match.
 pref("javascript.options.baselinejit.threshold", 10);