From 5fd4b87267ba8f3c667533b0336554a7cc008876 Mon Sep 17 00:00:00 2001
From: wolfbeast <mcwerewolf@wolfbeast.com>
Date: Wed, 15 May 2019 19:37:25 +0000
Subject: Remove unboxed objects from GC

---
 js/src/gc/Tracer.cpp | 69 ++--------------------------------------------------
 1 file changed, 2 insertions(+), 67 deletions(-)

(limited to 'js/src/gc/Tracer.cpp')

diff --git a/js/src/gc/Tracer.cpp b/js/src/gc/Tracer.cpp
index 63cd9b08a..3416464dd 100644
--- a/js/src/gc/Tracer.cpp
+++ b/js/src/gc/Tracer.cpp
@@ -201,80 +201,15 @@ gc::TraceCycleCollectorChildren(JS::CallbackTracer* trc, Shape* shape)
     } while (shape);
 }
 
-// Object groups can point to other object groups via an UnboxedLayout or the
-// the original unboxed group link. There can potentially be deep or cyclic
-// chains of such groups to trace through without going through a thing that
-// participates in cycle collection. These need to be handled iteratively to
-// avoid blowing the stack when running the cycle collector's callback tracer.
-struct ObjectGroupCycleCollectorTracer : public JS::CallbackTracer
-{
-    explicit ObjectGroupCycleCollectorTracer(JS::CallbackTracer* innerTracer)
-        : JS::CallbackTracer(innerTracer->runtime(), DoNotTraceWeakMaps),
-          innerTracer(innerTracer)
-    {}
-
-    void onChild(const JS::GCCellPtr& thing) override;
-
-    JS::CallbackTracer* innerTracer;
-    Vector<ObjectGroup*, 4, SystemAllocPolicy> seen, worklist;
-};
-
-void
-ObjectGroupCycleCollectorTracer::onChild(const JS::GCCellPtr& thing)
-{
-    if (thing.is<BaseShape>()) {
-        // The CC does not care about BaseShapes, and no additional GC things
-        // will be reached by following this edge.
-        return;
-    }
-
-    if (thing.is<JSObject>() || thing.is<JSScript>()) {
-        // Invoke the inner cycle collector callback on this child. It will not
-        // recurse back into TraceChildren.
-        innerTracer->onChild(thing);
-        return;
-    }
-
-    if (thing.is<ObjectGroup>()) {
-        // If this group is required to be in an ObjectGroup chain, trace it
-        // via the provided worklist rather than continuing to recurse.
-        ObjectGroup& group = thing.as<ObjectGroup>();
-        if (group.maybeUnboxedLayout()) {
-            for (size_t i = 0; i < seen.length(); i++) {
-                if (seen[i] == &group)
-                    return;
-            }
-            if (seen.append(&group) && worklist.append(&group)) {
-                return;
-            } else {
-                // If append fails, keep tracing normally. The worst that will
-                // happen is we end up overrecursing.
-            }
-        }
-    }
-
-    TraceChildren(this, thing.asCell(), thing.kind());
-}
-
 void
 gc::TraceCycleCollectorChildren(JS::CallbackTracer* trc, ObjectGroup* group)
 {
     MOZ_ASSERT(trc->isCallbackTracer());
 
-    // Early return if this group is not required to be in an ObjectGroup chain.
-    if (!group->maybeUnboxedLayout())
-        return group->traceChildren(trc);
-
-    ObjectGroupCycleCollectorTracer groupTracer(trc->asCallbackTracer());
-    group->traceChildren(&groupTracer);
-
-    while (!groupTracer.worklist.empty()) {
-        ObjectGroup* innerGroup = groupTracer.worklist.popCopy();
-        innerGroup->traceChildren(&groupTracer);
-    }
+    group->traceChildren(trc);
 }
 
-
+
 /*** Traced Edge Printer *************************************************************************/
 
 static size_t
-- 
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