Backout 483210d830f0 (bug 984537) for memory regressions.

js/src/jit/IonFrames.cpp

@@ -1238,14 +1238,6 @@ MarkJitActivations(JSRuntime *rt, JSTracer *trc)
         MarkJitActivation(trc, activations);
 }
 
-JSCompartment *
-TopmostJitActivationCompartment(JSRuntime *rt)
-{
-    for (JitActivationIterator activations(rt); !activations.done(); ++activations)
-        return activations.activation()->compartment();
-    return nullptr;
-}
-
 #ifdef JSGC_GENERATIONAL
 void
 UpdateJitActivationsForMinorGC(JSRuntime *rt, JSTracer *trc)

js/src/jit/IonFrames.h

@@ -268,9 +268,6 @@ void EnsureExitFrame(IonCommonFrameLayout *frame);
 void MarkJitActivations(JSRuntime *rt, JSTracer *trc);
 void MarkIonCompilerRoots(JSTracer *trc);
 
-JSCompartment *
-TopmostJitActivationCompartment(JSRuntime *rt);
-
 #ifdef JSGC_GENERATIONAL
 void UpdateJitActivationsForMinorGC(JSRuntime *rt, JSTracer *trc);
 #endif

js/src/jsgc.cpp

@@ -2852,13 +2852,6 @@ BeginMarkPhase(JSRuntime *rt)
             c->zone()->setPreservingCode(true);
     }
 
-    if (!rt->gc.shouldCleanUpEverything) {
-#ifdef JS_ION
-        if (JSCompartment *comp = jit::TopmostJitActivationCompartment(rt))
-            comp->zone()->setPreservingCode(true);
-#endif
-    }
-
     /*
      * Atoms are not in the cross-compartment map. So if there are any
      * zones that are not being collected, we are not allowed to collect