Merge branch 'ported-moebius'

Remove GCZeal code from Spidermonkey.
This resolves #8

36 files changed, 10 insertions, 1831 deletions

diff --git a/js/src/builtin/TestingFunctions.cpp b/js/src/builtin/TestingFunctions.cpp
index 5bc69a3467..acf449b7e5 100644
--- a/js/src/builtin/TestingFunctions.cpp
+++ b/js/src/builtin/TestingFunctions.cpp
@@ -188,14 +188,6 @@ GetBuildConfiguration(JSContext* cx, unsigned argc, Value* vp)
     if (!JS_SetProperty(cx, info, "tsan", value))
         return false;
 
-#ifdef JS_GC_ZEAL
-    value = BooleanValue(true);
-#else
-    value = BooleanValue(false);
-#endif
-    if (!JS_SetProperty(cx, info, "has-gczeal", value))
-        return false;
-
 #ifdef JS_MORE_DETERMINISTIC
     value = BooleanValue(true);
 #else
@@ -731,171 +723,6 @@ GCPreserveCode(JSContext* cx, unsigned argc, Value* vp)
     return true;
 }
 
-#ifdef JS_GC_ZEAL
-static bool
-GCZeal(JSContext* cx, unsigned argc, Value* vp)
-{
-    CallArgs args = CallArgsFromVp(argc, vp);
-
-    if (args.length() > 2) {
-        RootedObject callee(cx, &args.callee());
-        ReportUsageErrorASCII(cx, callee, "Too many arguments");
-        return false;
-    }
-
-    uint32_t zeal;
-    if (!ToUint32(cx, args.get(0), &zeal))
-        return false;
-
-    if (zeal > uint32_t(gc::ZealMode::Limit)) {
-        JS_ReportErrorASCII(cx, "gczeal argument out of range");
-        return false;
-    }
-
-    uint32_t frequency = JS_DEFAULT_ZEAL_FREQ;
-    if (args.length() >= 2) {
-        if (!ToUint32(cx, args.get(1), &frequency))
-            return false;
-    }
-
-    JS_SetGCZeal(cx, (uint8_t)zeal, frequency);
-    args.rval().setUndefined();
-    return true;
-}
-
-static bool
-ScheduleGC(JSContext* cx, unsigned argc, Value* vp)
-{
-    CallArgs args = CallArgsFromVp(argc, vp);
-
-    if (args.length() > 1) {
-        RootedObject callee(cx, &args.callee());
-        ReportUsageErrorASCII(cx, callee, "Too many arguments");
-        return false;
-    }
-
-    if (args.length() == 0) {
-        /* Fetch next zeal trigger only. */
-    } else if (args[0].isInt32()) {
-        /* Schedule a GC to happen after |arg| allocations. */
-        JS_ScheduleGC(cx, args[0].toInt32());
-    } else if (args[0].isObject()) {
-        /* Ensure that |zone| is collected during the next GC. */
-        Zone* zone = UncheckedUnwrap(&args[0].toObject())->zone();
-        PrepareZoneForGC(zone);
-    } else if (args[0].isString()) {
-        /* This allows us to schedule the atoms zone for GC. */
-        Zone* zone = args[0].toString()->zoneFromAnyThread();
-        if (!CurrentThreadCanAccessZone(zone)) {
-            RootedObject callee(cx, &args.callee());
-            ReportUsageErrorASCII(cx, callee, "Specified zone not accessible for GC");
-            return false;
-        }
-        PrepareZoneForGC(zone);
-    } else {
-        RootedObject callee(cx, &args.callee());
-        ReportUsageErrorASCII(cx, callee, "Bad argument - expecting integer, object or string");
-        return false;
-    }
-
-    uint32_t zealBits;
-    uint32_t freq;
-    uint32_t next;
-    JS_GetGCZealBits(cx, &zealBits, &freq, &next);
-    args.rval().setInt32(next);
-    return true;
-}
-
-static bool
-SelectForGC(JSContext* cx, unsigned argc, Value* vp)
-{
-    CallArgs args = CallArgsFromVp(argc, vp);
-
-    /*
-     * The selectedForMarking set is intended to be manually marked at slice
-     * start to detect missing pre-barriers. It is invalid for nursery things
-     * to be in the set, so evict the nursery before adding items.
-     */
-    JSRuntime* rt = cx->runtime();
-    rt->gc.evictNursery();
-
-    for (unsigned i = 0; i < args.length(); i++) {
-        if (args[i].isObject()) {
-            if (!rt->gc.selectForMarking(&args[i].toObject()))
-                return false;
-        }
-    }
-
-    args.rval().setUndefined();
-    return true;
-}
-
-static bool
-VerifyPreBarriers(JSContext* cx, unsigned argc, Value* vp)
-{
-    CallArgs args = CallArgsFromVp(argc, vp);
-
-    if (args.length() > 0) {
-        RootedObject callee(cx, &args.callee());
-        ReportUsageErrorASCII(cx, callee, "Too many arguments");
-        return false;
-    }
-
-    gc::VerifyBarriers(cx->runtime(), gc::PreBarrierVerifier);
-    args.rval().setUndefined();
-    return true;
-}
-
-static bool
-VerifyPostBarriers(JSContext* cx, unsigned argc, Value* vp)
-{
-    // This is a no-op since the post barrier verifier was removed.
-    CallArgs args = CallArgsFromVp(argc, vp);
-    if (args.length()) {
-        RootedObject callee(cx, &args.callee());
-        ReportUsageErrorASCII(cx, callee, "Too many arguments");
-        return false;
-    }
-    args.rval().setUndefined();
-    return true;
-}
-
-static bool
-GCState(JSContext* cx, unsigned argc, Value* vp)
-{
-    CallArgs args = CallArgsFromVp(argc, vp);
-
-    if (args.length() != 0) {
-        RootedObject callee(cx, &args.callee());
-        ReportUsageErrorASCII(cx, callee, "Too many arguments");
-        return false;
-    }
-
-    const char* state = StateName(cx->runtime()->gc.state());
-    JSString* str = JS_NewStringCopyZ(cx, state);
-    if (!str)
-        return false;
-    args.rval().setString(str);
-    return true;
-}
-
-static bool
-DeterministicGC(JSContext* cx, unsigned argc, Value* vp)
-{
-    CallArgs args = CallArgsFromVp(argc, vp);
-
-    if (args.length() != 1) {
-        RootedObject callee(cx, &args.callee());
-        ReportUsageErrorASCII(cx, callee, "Wrong number of arguments");
-        return false;
-    }
-
-    cx->runtime()->gc.setDeterministic(ToBoolean(args[0]));
-    args.rval().setUndefined();
-    return true;
-}
-#endif /* JS_GC_ZEAL */
-
 static bool
 StartGC(JSContext* cx, unsigned argc, Value* vp)
 {
@@ -1437,8 +1264,6 @@ OOMTest(JSContext* cx, unsigned argc, Value* vp)
     MOZ_ASSERT(!cx->isExceptionPending());
     rt->hadOutOfMemory = false;
 
-    JS_SetGCZeal(cx, 0, JS_DEFAULT_ZEAL_FREQ);
-
     for (unsigned thread = threadStart; thread < threadEnd; thread++) {
         if (verbose)
             fprintf(stderr, "thread %d\n", thread);
@@ -4387,39 +4212,6 @@ JS_FN_HELP("rejectPromise", RejectPromise, 2, 0,
 "gcPreserveCode()",
 "  Preserve JIT code during garbage collections."),
 
-#ifdef JS_GC_ZEAL
-    JS_FN_HELP("gczeal", GCZeal, 2, 0,
-"gczeal(level, [N])",
-gc::ZealModeHelpText),
-
-    JS_FN_HELP("schedulegc", ScheduleGC, 1, 0,
-"schedulegc([num | obj | string])",
-"  If num is given, schedule a GC after num allocations.\n"
-"  If obj is given, schedule a GC of obj's zone.\n"
-"  If string is given, schedule a GC of the string's zone if possible.\n"
-"  Returns the number of allocations before the next trigger."),
-
-    JS_FN_HELP("selectforgc", SelectForGC, 0, 0,
-"selectforgc(obj1, obj2, ...)",
-"  Schedule the given objects to be marked in the next GC slice."),
-
-    JS_FN_HELP("verifyprebarriers", VerifyPreBarriers, 0, 0,
-"verifyprebarriers()",
-"  Start or end a run of the pre-write barrier verifier."),
-
-    JS_FN_HELP("verifypostbarriers", VerifyPostBarriers, 0, 0,
-"verifypostbarriers()",
-"  Does nothing (the post-write barrier verifier has been remove)."),
-
-    JS_FN_HELP("gcstate", GCState, 0, 0,
-"gcstate()",
-"  Report the global GC state."),
-
-    JS_FN_HELP("deterministicgc", DeterministicGC, 1, 0,
-"deterministicgc(true|false)",
-"  If true, only allow determinstic GCs to run."),
-#endif
-
     JS_FN_HELP("startgc", StartGC, 1, 0,
 "startgc([n [, 'shrinking']])",
 "  Start an incremental GC and run a slice that processes about n objects.\n"
diff --git a/js/src/devtools/automation/variants/compacting b/js/src/devtools/automation/variants/compacting
index cd1891bfe4..2ffade6acd 100644
--- a/js/src/devtools/automation/variants/compacting
+++ b/js/src/devtools/automation/variants/compacting
@@ -3,7 +3,6 @@
     "optimize": true,
     "debug": true,
     "env": {
-        "JS_GC_ZEAL": "Compact",
         "JITTEST_EXTRA_ARGS": "--jitflags=debug --ignore-timeouts={DIR}/cgc-jittest-timeouts.txt",
         "JSTESTS_EXTRA_ARGS": "--exclude-file={DIR}/cgc-jstests-slow.txt"
     },
diff --git a/js/src/devtools/automation/variants/rootanalysis b/js/src/devtools/automation/variants/rootanalysis
index c5ed4dfcd1..508e1e2db2 100644
--- a/js/src/devtools/automation/variants/rootanalysis
+++ b/js/src/devtools/automation/variants/rootanalysis
@@ -3,7 +3,6 @@
     "optimize": true,
     "debug": true,
     "env": {
-        "JS_GC_ZEAL": "GenerationalGC",
         "JSTESTS_EXTRA_ARGS": "--jitflags=debug"
     }
 }
diff --git a/js/src/gc/Allocator.cpp b/js/src/gc/Allocator.cpp
index f7dc50d02b..3994d5a5b2 100644
--- a/js/src/gc/Allocator.cpp
+++ b/js/src/gc/Allocator.cpp
@@ -190,7 +190,7 @@ GCRuntime::checkAllocatorState(JSContext* cx, AllocKind kind)
             return false;
     }
 
-#if defined(JS_GC_ZEAL) || defined(DEBUG)
+#if defined(DEBUG)
     MOZ_ASSERT_IF(cx->compartment()->isAtomsCompartment(),
                   kind == AllocKind::ATOM ||
                   kind == AllocKind::FAT_INLINE_ATOM ||
@@ -223,11 +223,6 @@ GCRuntime::checkAllocatorState(JSContext* cx, AllocKind kind)
 bool
 GCRuntime::gcIfNeededPerAllocation(JSContext* cx)
 {
-#ifdef JS_GC_ZEAL
-    if (needZealousGC())
-        runDebugGC();
-#endif
-
     // Invoking the interrupt callback can fail and we can't usefully
     // handle that here. Just check in case we need to collect instead.
     if (rt->hasPendingInterrupt())
diff --git a/js/src/gc/GCInternals.h b/js/src/gc/GCInternals.h
index 722539e1ca..4919b87a54 100644
--- a/js/src/gc/GCInternals.h
+++ b/js/src/gc/GCInternals.h
@@ -61,51 +61,6 @@ class MOZ_RAII AutoPrepareForTracing
 AbortReason
 IsIncrementalGCUnsafe(JSRuntime* rt);
 
-#ifdef JS_GC_ZEAL
-
-class MOZ_RAII AutoStopVerifyingBarriers
-{
-    GCRuntime* gc;
-    bool restartPreVerifier;
-
-  public:
-    AutoStopVerifyingBarriers(JSRuntime* rt, bool isShutdown)
-      : gc(&rt->gc)
-    {
-        if (gc->isVerifyPreBarriersEnabled()) {
-            gc->endVerifyPreBarriers();
-            restartPreVerifier = !isShutdown;
-        } else {
-            restartPreVerifier = false;
-        }
-    }
-
-    ~AutoStopVerifyingBarriers() {
-        // Nasty special case: verification runs a minor GC, which *may* nest
-        // inside of an outer minor GC. This is not allowed by the
-        // gc::Statistics phase tree. So we pause the "real" GC, if in fact one
-        // is in progress.
-        gcstats::Phase outer = gc->stats.currentPhase();
-        if (outer != gcstats::PHASE_NONE)
-            gc->stats.endPhase(outer);
-        MOZ_ASSERT((gc->stats.currentPhase() == gcstats::PHASE_NONE) ||
-                   (gc->stats.currentPhase() == gcstats::PHASE_GC_BEGIN) ||
-                   (gc->stats.currentPhase() == gcstats::PHASE_GC_END));
-
-        if (restartPreVerifier)
-            gc->startVerifyPreBarriers();
-
-        if (outer != gcstats::PHASE_NONE)
-            gc->stats.beginPhase(outer);
-    }
-};
-#else
-struct MOZ_RAII AutoStopVerifyingBarriers
-{
-    AutoStopVerifyingBarriers(JSRuntime*, bool) {}
-};
-#endif /* JS_GC_ZEAL */
-
 #ifdef JSGC_HASH_TABLE_CHECKS
 void CheckHashTablesAfterMovingGC(JSRuntime* rt);
 void CheckHeapAfterGC(JSRuntime* rt);
diff --git a/js/src/gc/GCRuntime.h b/js/src/gc/GCRuntime.h
index 8c93228492..19737c9ee5 100644
--- a/js/src/gc/GCRuntime.h
+++ b/js/src/gc/GCRuntime.h
@@ -600,11 +600,6 @@ class GCRuntime
     void finishRoots();
     void finish();
 
-    inline bool hasZealMode(ZealMode mode);
-    inline void clearZealMode(ZealMode mode);
-    inline bool upcomingZealousGC();
-    inline bool needZealousGC();
-
     MOZ_MUST_USE bool addRoot(Value* vp, const char* name);
     void removeRoot(Value* vp);
     void setMarkStackLimit(size_t limit, AutoLockGC& lock);
@@ -638,7 +633,6 @@ class GCRuntime
         MOZ_RELEASE_ASSERT(triggerGC(JS::gcreason::ALLOC_TRIGGER));
     }
 
-    void runDebugGC();
     inline void poke();
 
     enum TraceOrMarkRuntime {
@@ -653,19 +647,6 @@ class GCRuntime
     void onOutOfMallocMemory();
     void onOutOfMallocMemory(const AutoLockGC& lock);
 
-#ifdef JS_GC_ZEAL
-    const void* addressOfZealModeBits() { return &zealModeBits; }
-    void getZealBits(uint32_t* zealBits, uint32_t* frequency, uint32_t* nextScheduled);
-    void setZeal(uint8_t zeal, uint32_t frequency);
-    bool parseAndSetZeal(const char* str);
-    void setNextScheduled(uint32_t count);
-    void verifyPreBarriers();
-    void maybeVerifyPreBarriers(bool always);
-    bool selectForMarking(JSObject* object);
-    void clearSelectedForMarking();
-    void setDeterministic(bool enable);
-#endif
-
     size_t maxMallocBytesAllocated() { return maxMallocBytes; }
 
     uint64_t nextCellUniqueId() {
@@ -851,15 +832,6 @@ class GCRuntime
                            AutoMaybeStartBackgroundAllocation& maybeStartBGAlloc);
     void recycleChunk(Chunk* chunk, const AutoLockGC& lock);
 
-#ifdef JS_GC_ZEAL
-    void startVerifyPreBarriers();
-    void endVerifyPreBarriers();
-    void finishVerifier();
-    bool isVerifyPreBarriersEnabled() const { return !!verifyPreData; }
-#else
-    bool isVerifyPreBarriersEnabled() const { return false; }
-#endif
-
     // Free certain LifoAlloc blocks when it is safe to do so.
     void freeUnusedLifoBlocksAfterSweeping(LifoAlloc* lifo);
     void freeAllLifoBlocksAfterSweeping(LifoAlloc* lifo);
@@ -948,7 +920,6 @@ class GCRuntime
     void incrementalCollectSlice(SliceBudget& budget, JS::gcreason::Reason reason,
                                  AutoLockForExclusiveAccess& lock);
 
-    void pushZealSelectedObjects();
     void purgeRuntime(AutoLockForExclusiveAccess& lock);
     MOZ_MUST_USE bool beginMarkPhase(JS::gcreason::Reason reason, AutoLockForExclusiveAccess& lock);
     bool shouldPreserveJITCode(JSCompartment* comp, int64_t currentTime,
@@ -1004,10 +975,6 @@ class GCRuntime
     void releaseRelocatedArenasWithoutUnlocking(Arena* arenaList, const AutoLockGC& lock);
     void finishCollection(JS::gcreason::Reason reason);
 
-    void computeNonIncrementalMarkingForValidation(AutoLockForExclusiveAccess& lock);
-    void validateIncrementalMarking();
-    void finishMarkingValidation();
-
 #ifdef DEBUG
     void checkForCompartmentMismatches();
 #endif
@@ -1219,10 +1186,6 @@ class GCRuntime
     ZoneList zonesToMaybeCompact;
     Arena* relocatedArenasToRelease;
 
-#ifdef JS_GC_ZEAL
-    MarkingValidator* markingValidator;
-#endif
-
     /*
      * Indicates that a GC slice has taken place in the middle of an animation
      * frame, rather than at the beginning. In this case, the next slice will be
@@ -1274,40 +1237,6 @@ class GCRuntime
 
     bool poked;
 
-    /*
-     * These options control the zealousness of the GC. At every allocation,
-     * nextScheduled is decremented. When it reaches zero we do a full GC.
-     *
-     * At this point, if zeal_ is one of the types that trigger periodic
-     * collection, then nextScheduled is reset to the value of zealFrequency.
-     * Otherwise, no additional GCs take place.
-     *
-     * You can control these values in several ways:
-     *   - Set the JS_GC_ZEAL environment variable
-     *   - Call gczeal() or schedulegc() from inside shell-executed JS code
-     *     (see the help for details)
-     *
-     * If gcZeal_ == 1 then we perform GCs in select places (during MaybeGC and
-     * whenever a GC poke happens). This option is mainly useful to embedders.
-     *
-     * We use zeal_ == 4 to enable write barrier verification. See the comment
-     * in jsgc.cpp for more information about this.
-     *
-     * zeal_ values from 8 to 10 periodically run different types of
-     * incremental GC.
-     *
-     * zeal_ value 14 performs periodic shrinking collections.
-     */
-#ifdef JS_GC_ZEAL
-    uint32_t zealModeBits;
-    int zealFrequency;
-    int nextScheduled;
-    bool deterministicOnly;
-    int incrementalLimit;
-
-    Vector<JSObject*, 0, SystemAllocPolicy> selectedForMarking;
-#endif
-
     bool fullCompartmentChecks;
 
     Callback<JSGCCallback> gcCallback;
@@ -1415,51 +1344,6 @@ class MOZ_RAII AutoMaybeStartBackgroundAllocation
     }
 };
 
-#ifdef JS_GC_ZEAL
-
-inline bool
-GCRuntime::hasZealMode(ZealMode mode)
-{
-    static_assert(size_t(ZealMode::Limit) < sizeof(zealModeBits) * 8,
-                  "Zeal modes must fit in zealModeBits");
-    return zealModeBits & (1 << uint32_t(mode));
-}
-
-inline void
-GCRuntime::clearZealMode(ZealMode mode)
-{
-    zealModeBits &= ~(1 << uint32_t(mode));
-    MOZ_ASSERT(!hasZealMode(mode));
-}
-
-inline bool
-GCRuntime::upcomingZealousGC() {
-    return nextScheduled == 1;
-}
-
-inline bool
-GCRuntime::needZealousGC() {
-    if (nextScheduled > 0 && --nextScheduled == 0) {
-        if (hasZealMode(ZealMode::Alloc) ||
-            hasZealMode(ZealMode::GenerationalGC) ||
-            hasZealMode(ZealMode::IncrementalRootsThenFinish) ||
-            hasZealMode(ZealMode::IncrementalMarkAllThenFinish) ||
-            hasZealMode(ZealMode::IncrementalMultipleSlices) ||
-            hasZealMode(ZealMode::Compact))
-        {
-            nextScheduled = zealFrequency;
-        }
-        return true;
-    }
-    return false;
-}
-#else
-inline bool GCRuntime::hasZealMode(ZealMode mode) { return false; }
-inline void GCRuntime::clearZealMode(ZealMode mode) { }
-inline bool GCRuntime::upcomingZealousGC() { return false; }
-inline bool GCRuntime::needZealousGC() { return false; }
-#endif
-
 } /* namespace gc */
 
 } /* namespace js */
diff --git a/js/src/gc/Heap.h b/js/src/gc/Heap.h
index 2a9390e91a..6978033809 100644
--- a/js/src/gc/Heap.h
+++ b/js/src/gc/Heap.h
@@ -1322,22 +1322,6 @@ TenuredCell::writeBarrierPre(TenuredCell* thing)
     if (!thing)
         return;
 
-#ifdef JS_GC_ZEAL
-    // When verifying pre barriers we need to switch on all barriers, even
-    // those on the Atoms Zone. Normally, we never enter a parse task when
-    // collecting in the atoms zone, so will filter out atoms below.
-    // Unfortuantely, If we try that when verifying pre-barriers, we'd never be
-    // able to handle OMT parse tasks at all as we switch on the verifier any
-    // time we're not doing GC. This would cause us to deadlock, as OMT parsing
-    // is meant to resume after GC work completes. Instead we filter out any
-    // OMT barriers that reach us and assert that they would normally not be
-    // possible.
-    if (!CurrentThreadCanAccessRuntime(thing->runtimeFromAnyThread())) {
-        AssertSafeToSkipBarrier(thing);
-        return;
-    }
-#endif
-
     JS::shadow::Zone* shadowZone = thing->shadowZoneFromAnyThread();
     if (shadowZone->needsIncrementalBarrier()) {
         MOZ_ASSERT(!RuntimeFromMainThreadIsHeapMajorCollecting(shadowZone));
diff --git a/js/src/gc/Nursery.cpp b/js/src/gc/Nursery.cpp
index 2c402fe0b9..bce2b74aa5 100644
--- a/js/src/gc/Nursery.cpp
+++ b/js/src/gc/Nursery.cpp
@@ -74,14 +74,6 @@ struct js::Nursery::SweepAction
 #endif
 };
 
-#ifdef JS_GC_ZEAL
-struct js::Nursery::Canary
-{
-    uintptr_t magicValue;
-    Canary* next;
-};
-#endif
-
 inline void
 js::Nursery::NurseryChunk::poisonAndInit(JSRuntime* rt, uint8_t poison)
 {
@@ -124,9 +116,6 @@ js::Nursery::Nursery(JSRuntime* rt)
   , minorGcCount_(0)
   , freeMallocedBuffersTask(nullptr)
   , sweepActions_(nullptr)
-#ifdef JS_GC_ZEAL
-  , lastCanary_(nullptr)
-#endif
 {}
 
 bool
@@ -199,7 +188,6 @@ void
 js::Nursery::enable()
 {
     MOZ_ASSERT(isEmpty());
-    MOZ_ASSERT(!runtime()->gc.isVerifyPreBarriersEnabled());
     if (isEnabled())
         return;
 
@@ -209,10 +197,6 @@ js::Nursery::enable()
 
     setCurrentChunk(0);
     setStartPosition();
-#ifdef JS_GC_ZEAL
-    if (runtime()->hasZealMode(ZealMode::GenerationalGC))
-        enterZealMode();
-#endif
 
     MOZ_ALWAYS_TRUE(runtime()->gc.storeBuffer.enable());
     return;
@@ -235,31 +219,11 @@ js::Nursery::isEmpty() const
     MOZ_ASSERT(runtime_);
     if (!isEnabled())
         return true;
-
-    if (!runtime_->hasZealMode(ZealMode::GenerationalGC)) {
-        MOZ_ASSERT(currentStartChunk_ == 0);
-        MOZ_ASSERT(currentStartPosition_ == chunk(0).start());
-    }
+    MOZ_ASSERT(currentStartChunk_ == 0);
+    MOZ_ASSERT(currentStartPosition_ == chunk(0).start());
     return position() == currentStartPosition_;
 }
 
-#ifdef JS_GC_ZEAL
-void
-js::Nursery::enterZealMode() {
-    if (isEnabled())
-        updateNumChunks(maxNurseryChunks_);
-}
-
-void
-js::Nursery::leaveZealMode() {
-    if (isEnabled()) {
-        MOZ_ASSERT(isEmpty());
-        setCurrentChunk(0);
-        setStartPosition();
-    }
-}
-#endif // JS_GC_ZEAL
-
 JSObject*
 js::Nursery::allocateObject(JSContext* cx, size_t size, size_t numDynamic, const js::Class* clasp)
 {
@@ -305,12 +269,6 @@ js::Nursery::allocate(size_t size)
     MOZ_ASSERT(position() % gc::CellSize == 0);
     MOZ_ASSERT(size % gc::CellSize == 0);
 
-#ifdef JS_GC_ZEAL
-    static const size_t CanarySize = (sizeof(Nursery::Canary) + CellSize - 1) & ~CellMask;
-    if (runtime()->gc.hasZealMode(ZealMode::CheckNursery))
-        size += CanarySize;
-#endif
-
     if (currentEnd() < position() + size) {
         if (currentChunk_ + 1 == numChunks())
             return nullptr;
@@ -322,19 +280,6 @@ js::Nursery::allocate(size_t size)
 
     JS_EXTRA_POISON(thing, JS_ALLOCATED_NURSERY_PATTERN, size);
 
-#ifdef JS_GC_ZEAL
-    if (runtime()->gc.hasZealMode(ZealMode::CheckNursery)) {
-        auto canary = reinterpret_cast<Canary*>(position() - CanarySize);
-        canary->magicValue = CanaryMagicValue;
-        canary->next = nullptr;
-        if (lastCanary_) {
-            MOZ_ASSERT(!lastCanary_->next);
-            lastCanary_->next = canary;
-        }
-        lastCanary_ = canary;
-    }
-#endif
-
     MemProfiler::SampleNursery(reinterpret_cast<void*>(thing), size);
     return thing;
 }
@@ -561,14 +506,6 @@ js::Nursery::collect(JSRuntime* rt, JS::gcreason::Reason reason)
 
     rt->gc.incMinorGcNumber();
 
-#ifdef JS_GC_ZEAL
-    if (rt->gc.hasZealMode(ZealMode::CheckNursery)) {
-        for (auto canary = lastCanary_; canary; canary = canary->next)
-            MOZ_ASSERT(canary->magicValue == CanaryMagicValue);
-    }
-    lastCanary_ = nullptr;
-#endif
-
     rt->gc.stats.beginNurseryCollection(reason);
     TraceMinorGCStart();
 
@@ -659,7 +596,6 @@ js::Nursery::doCollection(JSRuntime* rt, JS::gcreason::Reason reason,
 {
     AutoTraceSession session(rt, JS::HeapState::MinorCollecting);
     AutoSetThreadIsPerformingGC performingGC;
-    AutoStopVerifyingBarriers av(rt, false);
     AutoDisableProxyCheck disableStrictProxyChecking(rt);
     mozilla::DebugOnly<AutoEnterOOMUnsafeRegion> oomUnsafeRegion;
 
@@ -752,10 +688,6 @@ js::Nursery::doCollection(JSRuntime* rt, JS::gcreason::Reason reason,
 
     // Make sure hashtables have been updated after the collection.
     maybeStartProfile(ProfileKey::CheckHashTables);
-#ifdef JS_GC_ZEAL
-    if (rt->hasZealMode(ZealMode::CheckHashTablesOnMinorGC))
-        CheckHashTablesAfterMovingGC(rt);
-#endif
     maybeEndProfile(ProfileKey::CheckHashTables);
 
     // Calculate and return the promotion rate.
@@ -828,17 +760,6 @@ js::Nursery::sweep()
     runSweepActions();
     sweepDictionaryModeObjects();
 
-#ifdef JS_GC_ZEAL
-    /* Poison the nursery contents so touching a freed object will crash. */
-    for (unsigned i = 0; i < numChunks(); i++)
-        chunk(i).poisonAndInit(runtime(), JS_SWEPT_NURSERY_PATTERN);
-
-    if (runtime()->hasZealMode(ZealMode::GenerationalGC)) {
-        /* Only reset the alloc point when we are close to the end. */
-        if (currentChunk_ + 1 == numChunks())
-            setCurrentChunk(0);
-    } else
-#endif
     {
 #ifdef JS_CRASH_DIAGNOSTICS
         for (unsigned i = 0; i < numChunks(); ++i)
@@ -916,20 +837,12 @@ js::Nursery::growAllocableSpace()
 void
 js::Nursery::shrinkAllocableSpace()
 {
-#ifdef JS_GC_ZEAL
-    if (runtime()->hasZealMode(ZealMode::GenerationalGC))
-        return;
-#endif
     updateNumChunks(Max(numChunks() - 1, 1u));
 }
 
 void
 js::Nursery::minimizeAllocableSpace()
 {
-#ifdef JS_GC_ZEAL
-    if (runtime()->hasZealMode(ZealMode::GenerationalGC))
-        return;
-#endif
     updateNumChunks(1);
 }
 
diff --git a/js/src/gc/Nursery.h b/js/src/gc/Nursery.h
index 69fb66b7a4..0d215d9975 100644
--- a/js/src/gc/Nursery.h
+++ b/js/src/gc/Nursery.h
@@ -58,8 +58,6 @@ class NativeObject;
 class Nursery;
 class HeapSlot;
 
-void SetGCZeal(JSRuntime*, uint8_t, uint32_t);
-
 namespace gc {
 class AutoMaybeStartBackgroundAllocation;
 struct Cell;
@@ -252,11 +250,6 @@ class Nursery
                (numChunks() - currentChunk_ - 1) * NurseryChunkUsableSize;
     }
 
-#ifdef JS_GC_ZEAL
-    void enterZealMode();
-    void leaveZealMode();
-#endif
-
     /* Print total profile times on shutdown. */
     void printTotalProfileTimes();
 
@@ -374,11 +367,6 @@ class Nursery
     using NativeObjectVector = Vector<NativeObject*, 0, SystemAllocPolicy>;
     NativeObjectVector dictionaryModeObjects_;
 
-#ifdef JS_GC_ZEAL
-    struct Canary;
-    Canary* lastCanary_;
-#endif
-
     NurseryChunk* allocChunk();
 
     NurseryChunk& chunk(unsigned index) const {
diff --git a/js/src/gc/Verifier.cpp b/js/src/gc/Verifier.cpp
index dd40316061..3ebbbb4f67 100644
--- a/js/src/gc/Verifier.cpp
+++ b/js/src/gc/Verifier.cpp
@@ -26,420 +26,6 @@
 using namespace js;
 using namespace js::gc;
 
-#ifdef JS_GC_ZEAL
-
-/*
- * Write barrier verification
- *
- * The next few functions are for write barrier verification.
- *
- * The VerifyBarriers function is a shorthand. It checks if a verification phase
- * is currently running. If not, it starts one. Otherwise, it ends the current
- * phase and starts a new one.
- *
- * The user can adjust the frequency of verifications, which causes
- * VerifyBarriers to be a no-op all but one out of N calls. However, if the
- * |always| parameter is true, it starts a new phase no matter what.
- *
- * Pre-Barrier Verifier:
- *   When StartVerifyBarriers is called, a snapshot is taken of all objects in
- *   the GC heap and saved in an explicit graph data structure. Later,
- *   EndVerifyBarriers traverses the heap again. Any pointer values that were in
- *   the snapshot and are no longer found must be marked; otherwise an assertion
- *   triggers. Note that we must not GC in between starting and finishing a
- *   verification phase.
- */
-
-struct EdgeValue
-{
-    void* thing;
-    JS::TraceKind kind;
-    const char* label;
-};
-
-struct VerifyNode
-{
-    void* thing;
-    JS::TraceKind kind;
-    uint32_t count;
-    EdgeValue edges[1];
-};
-
-typedef HashMap<void*, VerifyNode*, DefaultHasher<void*>, SystemAllocPolicy> NodeMap;
-
-/*
- * The verifier data structures are simple. The entire graph is stored in a
- * single block of memory. At the beginning is a VerifyNode for the root
- * node. It is followed by a sequence of EdgeValues--the exact number is given
- * in the node. After the edges come more nodes and their edges.
- *
- * The edgeptr and term fields are used to allocate out of the block of memory
- * for the graph. If we run out of memory (i.e., if edgeptr goes beyond term),
- * we just abandon the verification.
- *
- * The nodemap field is a hashtable that maps from the address of the GC thing
- * to the VerifyNode that represents it.
- */
-class js::VerifyPreTracer final : public JS::CallbackTracer
-{
-    JS::AutoDisableGenerationalGC noggc;
-
-    void onChild(const JS::GCCellPtr& thing) override;
-
-  public:
-    /* The gcNumber when the verification began. */
-    uint64_t number;
-
-    /* This counts up to gcZealFrequency to decide whether to verify. */
-    int count;
-
-    /* This graph represents the initial GC "snapshot". */
-    VerifyNode* curnode;
-    VerifyNode* root;
-    char* edgeptr;
-    char* term;
-    NodeMap nodemap;
-
-    explicit VerifyPreTracer(JSRuntime* rt)
-      : JS::CallbackTracer(rt), noggc(rt), number(rt->gc.gcNumber()), count(0), curnode(nullptr),
-        root(nullptr), edgeptr(nullptr), term(nullptr)
-    {}
-
-    ~VerifyPreTracer() {
-        js_free(root);
-    }
-};
-
-/*
- * This function builds up the heap snapshot by adding edges to the current
- * node.
- */
-void
-VerifyPreTracer::onChild(const JS::GCCellPtr& thing)
-{
-    MOZ_ASSERT(!IsInsideNursery(thing.asCell()));
-
-    // Skip things in other runtimes.
-    if (thing.asCell()->asTenured().runtimeFromAnyThread() != runtime())
-        return;
-
-    edgeptr += sizeof(EdgeValue);
-    if (edgeptr >= term) {
-        edgeptr = term;
-        return;
-    }
-
-    VerifyNode* node = curnode;
-    uint32_t i = node->count;
-
-    node->edges[i].thing = thing.asCell();
-    node->edges[i].kind = thing.kind();
-    node->edges[i].label = contextName();
-    node->count++;
-}
-
-static VerifyNode*
-MakeNode(VerifyPreTracer* trc, void* thing, JS::TraceKind kind)
-{
-    NodeMap::AddPtr p = trc->nodemap.lookupForAdd(thing);
-    if (!p) {
-        VerifyNode* node = (VerifyNode*)trc->edgeptr;
-        trc->edgeptr += sizeof(VerifyNode) - sizeof(EdgeValue);
-        if (trc->edgeptr >= trc->term) {
-            trc->edgeptr = trc->term;
-            return nullptr;
-        }
-
-        node->thing = thing;
-        node->count = 0;
-        node->kind = kind;
-        if (!trc->nodemap.add(p, thing, node)) {
-            trc->edgeptr = trc->term;
-            return nullptr;
-        }
-
-        return node;
-    }
-    return nullptr;
-}
-
-static VerifyNode*
-NextNode(VerifyNode* node)
-{
-    if (node->count == 0)
-        return (VerifyNode*)((char*)node + sizeof(VerifyNode) - sizeof(EdgeValue));
-    else
-        return (VerifyNode*)((char*)node + sizeof(VerifyNode) +
-                             sizeof(EdgeValue)*(node->count - 1));
-}
-
-void
-gc::GCRuntime::startVerifyPreBarriers()
-{
-    if (verifyPreData || isIncrementalGCInProgress())
-        return;
-
-    if (IsIncrementalGCUnsafe(rt) != AbortReason::None)
-        return;
-
-    number++;
-
-    VerifyPreTracer* trc = js_new<VerifyPreTracer>(rt);
-    if (!trc)
-        return;
-
-    AutoPrepareForTracing prep(rt->contextFromMainThread(), WithAtoms);
-
-    for (auto chunk = allNonEmptyChunks(); !chunk.done(); chunk.next())
-        chunk->bitmap.clear();
-
-    gcstats::AutoPhase ap(stats, gcstats::PHASE_TRACE_HEAP);
-
-    const size_t size = 64 * 1024 * 1024;
-    trc->root = (VerifyNode*)js_malloc(size);
-    if (!trc->root)
-        goto oom;
-    trc->edgeptr = (char*)trc->root;
-    trc->term = trc->edgeptr + size;
-
-    if (!trc->nodemap.init())
-        goto oom;
-
-    /* Create the root node. */
-    trc->curnode = MakeNode(trc, nullptr, JS::TraceKind(0));
-
-    incrementalState = State::MarkRoots;
-
-    /* Make all the roots be edges emanating from the root node. */
-    traceRuntime(trc, prep.session().lock);
-
-    VerifyNode* node;
-    node = trc->curnode;
-    if (trc->edgeptr == trc->term)
-        goto oom;
-
-    /* For each edge, make a node for it if one doesn't already exist. */
-    while ((char*)node < trc->edgeptr) {
-        for (uint32_t i = 0; i < node->count; i++) {
-            EdgeValue& e = node->edges[i];
-            VerifyNode* child = MakeNode(trc, e.thing, e.kind);
-            if (child) {
-                trc->curnode = child;
-                js::TraceChildren(trc, e.thing, e.kind);
-            }
-            if (trc->edgeptr == trc->term)
-                goto oom;
-        }
-
-        node = NextNode(node);
-    }
-
-    verifyPreData = trc;
-    incrementalState = State::Mark;
-    marker.start();
-
-    for (ZonesIter zone(rt, WithAtoms); !zone.done(); zone.next()) {
-        PurgeJITCaches(zone);
-        if (!zone->usedByExclusiveThread) {
-            zone->setNeedsIncrementalBarrier(true, Zone::UpdateJit);
-            zone->arenas.purge();
-        }
-    }
-
-    return;
-
-oom:
-    incrementalState = State::NotActive;
-    js_delete(trc);
-    verifyPreData = nullptr;
-}
-
-static bool
-IsMarkedOrAllocated(TenuredCell* cell)
-{
-    return cell->isMarked() || cell->arena()->allocatedDuringIncremental;
-}
-
-struct CheckEdgeTracer : public JS::CallbackTracer {
-    VerifyNode* node;
-    explicit CheckEdgeTracer(JSRuntime* rt) : JS::CallbackTracer(rt), node(nullptr) {}
-    void onChild(const JS::GCCellPtr& thing) override;
-};
-
-static const uint32_t MAX_VERIFIER_EDGES = 1000;
-
-/*
- * This function is called by EndVerifyBarriers for every heap edge. If the edge
- * already existed in the original snapshot, we "cancel it out" by overwriting
- * it with nullptr. EndVerifyBarriers later asserts that the remaining
- * non-nullptr edges (i.e., the ones from the original snapshot that must have
- * been modified) must point to marked objects.
- */
-void
-CheckEdgeTracer::onChild(const JS::GCCellPtr& thing)
-{
-    // Skip things in other runtimes.
-    if (thing.asCell()->asTenured().runtimeFromAnyThread() != runtime())
-        return;
-
-    /* Avoid n^2 behavior. */
-    if (node->count > MAX_VERIFIER_EDGES)
-        return;
-
-    for (uint32_t i = 0; i < node->count; i++) {
-        if (node->edges[i].thing == thing.asCell()) {
-            MOZ_ASSERT(node->edges[i].kind == thing.kind());
-            node->edges[i].thing = nullptr;
-            return;
-        }
-    }
-}
-
-void
-js::gc::AssertSafeToSkipBarrier(TenuredCell* thing)
-{
-    Zone* zone = thing->zoneFromAnyThread();
-    MOZ_ASSERT(!zone->needsIncrementalBarrier() || zone->isAtomsZone());
-}
-
-static bool
-IsMarkedOrAllocated(const EdgeValue& edge)
-{
-    if (!edge.thing || IsMarkedOrAllocated(TenuredCell::fromPointer(edge.thing)))
-        return true;
-
-    // Permanent atoms and well-known symbols aren't marked during graph traversal.
-    if (edge.kind == JS::TraceKind::String && static_cast<JSString*>(edge.thing)->isPermanentAtom())
-        return true;
-    if (edge.kind == JS::TraceKind::Symbol && static_cast<JS::Symbol*>(edge.thing)->isWellKnownSymbol())
-        return true;
-
-    return false;
-}
-
-void
-gc::GCRuntime::endVerifyPreBarriers()
-{
-    VerifyPreTracer* trc = verifyPreData;
-
-    if (!trc)
-        return;
-
-    MOZ_ASSERT(!JS::IsGenerationalGCEnabled(rt));
-
-    AutoPrepareForTracing prep(rt->contextFromMainThread(), SkipAtoms);
-
-    bool compartmentCreated = false;
-
-    /* We need to disable barriers before tracing, which may invoke barriers. */
-    for (ZonesIter zone(rt, WithAtoms); !zone.done(); zone.next()) {
-        if (!zone->needsIncrementalBarrier())
-            compartmentCreated = true;
-
-        zone->setNeedsIncrementalBarrier(false, Zone::UpdateJit);
-        PurgeJITCaches(zone);
-    }
-
-    /*
-     * We need to bump gcNumber so that the methodjit knows that jitcode has
-     * been discarded.
-     */
-    MOZ_ASSERT(trc->number == number);
-    number++;
-
-    verifyPreData = nullptr;
-    incrementalState = State::NotActive;
-
-    if (!compartmentCreated && IsIncrementalGCUnsafe(rt) == AbortReason::None) {
-        CheckEdgeTracer cetrc(rt);
-
-        /* Start after the roots. */
-        VerifyNode* node = NextNode(trc->root);
-        while ((char*)node < trc->edgeptr) {
-            cetrc.node = node;
-            js::TraceChildren(&cetrc, node->thing, node->kind);
-
-            if (node->count <= MAX_VERIFIER_EDGES) {
-                for (uint32_t i = 0; i < node->count; i++) {
-                    EdgeValue& edge = node->edges[i];
-                    if (!IsMarkedOrAllocated(edge)) {
-                        char msgbuf[1024];
-                        SprintfLiteral(msgbuf,
-                                       "[barrier verifier] Unmarked edge: %s %p '%s' edge to %s %p",
-                                       JS::GCTraceKindToAscii(node->kind), node->thing,
-                                       edge.label,
-                                       JS::GCTraceKindToAscii(edge.kind), edge.thing);
-                        MOZ_ReportAssertionFailure(msgbuf, __FILE__, __LINE__);
-                        MOZ_CRASH();
-                    }
-                }
-            }
-
-            node = NextNode(node);
-        }
-    }
-
-    marker.reset();
-    marker.stop();
-
-    js_delete(trc);
-}
-
-/*** Barrier Verifier Scheduling ***/
-
-void
-gc::GCRuntime::verifyPreBarriers()
-{
-    if (verifyPreData)
-        endVerifyPreBarriers();
-    else
-        startVerifyPreBarriers();
-}
-
-void
-gc::VerifyBarriers(JSRuntime* rt, VerifierType type)
-{
-    if (type == PreBarrierVerifier)
-        rt->gc.verifyPreBarriers();
-}
-
-void
-gc::GCRuntime::maybeVerifyPreBarriers(bool always)
-{
-    if (!hasZealMode(ZealMode::VerifierPre))
-        return;
-
-    if (rt->mainThread.suppressGC)
-        return;
-
-    if (verifyPreData) {
-        if (++verifyPreData->count < zealFrequency && !always)
-            return;
-
-        endVerifyPreBarriers();
-    }
-
-    startVerifyPreBarriers();
-}
-
-void
-js::gc::MaybeVerifyBarriers(JSContext* cx, bool always)
-{
-    GCRuntime* gc = &cx->runtime()->gc;
-    gc->maybeVerifyPreBarriers(always);
-}
-
-void
-js::gc::GCRuntime::finishVerifier()
-{
-    if (verifyPreData) {
-        js_delete(verifyPreData);
-        verifyPreData = nullptr;
-    }
-}
-
-#endif /* JS_GC_ZEAL */
-
 #ifdef JSGC_HASH_TABLE_CHECKS
 
 class CheckHeapTracer : public JS::CallbackTracer
diff --git a/js/src/gc/Zone.h b/js/src/gc/Zone.h
index a3a6dc07f0..50d06319db 100644
--- a/js/src/gc/Zone.h
+++ b/js/src/gc/Zone.h
@@ -253,12 +253,6 @@ struct Zone : public JS::shadow::Zone,
     // possibly at other times too.
     uint64_t gcNumber();
 
-    bool compileBarriers() const { return compileBarriers(needsIncrementalBarrier()); }
-    bool compileBarriers(bool needsIncrementalBarrier) const {
-        return needsIncrementalBarrier ||
-               runtimeFromMainThread()->hasZealMode(js::gc::ZealMode::VerifierPre);
-    }
-
     enum ShouldUpdateJit { DontUpdateJit, UpdateJit };
     void setNeedsIncrementalBarrier(bool needs, ShouldUpdateJit updateJit);
     const bool* addressOfNeedsIncrementalBarrier() const { return &needsIncrementalBarrier_; }
diff --git a/js/src/jit-test/tests/ion/bug730152.js b/js/src/jit-test/tests/ion/bug730152.js
deleted file mode 100644
index fe4ecfe14f..0000000000
--- a/js/src/jit-test/tests/ion/bug730152.js
+++ /dev/null
@@ -1,4 +0,0 @@
-if (typeof verifybarriers !== "undefined") {
-    for (var i = 0; i < 30; i++) {}
-    for (i in Function("gc(verifybarriers()); yield")()) {}
-}
diff --git a/js/src/jit-test/tests/ion/bug732758.js b/js/src/jit-test/tests/ion/bug732758.js
index 91da521c79..8196c3e034 100644
--- a/js/src/jit-test/tests/ion/bug732758.js
+++ b/js/src/jit-test/tests/ion/bug732758.js
@@ -38,5 +38,4 @@ tryItOut("{t:g}");
 tryItOut("r");
 tryItOut("p");
 tryItOut("gc()");
-tryItOut("verifybarriers()");
 tryItOut("/**/yield");
diff --git a/js/src/jit/CompileWrappers.h b/js/src/jit/CompileWrappers.h
index bbec9ffa34..ccded4f13b 100644
--- a/js/src/jit/CompileWrappers.h
+++ b/js/src/jit/CompileWrappers.h
@@ -51,10 +51,6 @@ class CompileRuntime
     // &runtime()->activation_
     const void* addressOfActivation();
 
-#ifdef JS_GC_ZEAL
-    const void* addressOfGCZealModeBits();
-#endif
-
     const void* addressOfInterruptUint32();
 
     // We have to bake JSContext* into JIT code, but this pointer shouldn't be
diff --git a/js/src/jit/VMFunctions.cpp b/js/src/jit/VMFunctions.cpp
index 628b31fae4..4edbc3c836 100644
--- a/js/src/jit/VMFunctions.cpp
+++ b/js/src/jit/VMFunctions.cpp
@@ -135,7 +135,6 @@ CheckOverRecursed(JSContext* cx)
 #else
     JS_CHECK_RECURSION(cx, return false);
 #endif
-    gc::MaybeVerifyBarriers(cx);
     return cx->runtime()->handleInterrupt(cx);
 }
 
@@ -180,7 +179,6 @@ CheckOverRecursedWithExtra(JSContext* cx, BaselineFrame* frame,
     JS_CHECK_RECURSION_WITH_SP(cx, checkSp, return false);
 #endif
 
-    gc::MaybeVerifyBarriers(cx);
     return cx->runtime()->handleInterrupt(cx);
 }
 
@@ -465,8 +463,6 @@ SetProperty(JSContext* cx, HandleObject obj, HandlePropertyName name, HandleValu
 bool
 InterruptCheck(JSContext* cx)
 {
-    gc::MaybeVerifyBarriers(cx);
-
     {
         JSRuntime* rt = cx->runtime();
         JitRuntime::AutoPreventBackedgePatching apbp(rt);
@@ -627,11 +623,7 @@ PostWriteElementBarrier(JSRuntime* rt, JSObject* obj, int32_t index)
     if (obj->is<NativeObject>() &&
         !obj->as<NativeObject>().isInWholeCellBuffer() &&
         uint32_t(index) < obj->as<NativeObject>().getDenseInitializedLength() &&
-        (obj->as<NativeObject>().getDenseInitializedLength() > MAX_WHOLE_CELL_BUFFER_SIZE
-#ifdef JS_GC_ZEAL
-         || rt->hasZealMode(gc::ZealMode::ElementsBarrier)
-#endif
-        ))
+        (obj->as<NativeObject>().getDenseInitializedLength() > MAX_WHOLE_CELL_BUFFER_SIZE))
     {
         rt->gc.storeBuffer.putSlot(&obj->as<NativeObject>(), HeapSlot::Element, index, 1);
         return;
diff --git a/js/src/js-config.h.in b/js/src/js-config.h.in
index f2ce93e122..779446fd75 100644
--- a/js/src/js-config.h.in
+++ b/js/src/js-config.h.in
@@ -38,10 +38,6 @@
 /* Define to 1 if SpiderMonkey should include ctypes support.  */
 #undef JS_HAS_CTYPES
 
-/* Define to 1 if SpiderMonkey should support the ability to perform
-   entirely too much GC.  */
-#undef JS_GC_ZEAL
-
 /* Define to 1 if SpiderMonkey should use small chunks. */
 #undef JS_GC_SMALL_CHUNK_SIZE
 
diff --git a/js/src/jsapi-tests/testGCFinalizeCallback.cpp b/js/src/jsapi-tests/testGCFinalizeCallback.cpp
index 48003ab0ce..a8f7ba7f88 100644
--- a/js/src/jsapi-tests/testGCFinalizeCallback.cpp
+++ b/js/src/jsapi-tests/testGCFinalizeCallback.cpp
@@ -94,36 +94,6 @@ BEGIN_TEST(testGCFinalizeCallback)
     CHECK(checkFinalizeStatus());
     CHECK(checkFinalizeIsZoneGC(true));
 
-#ifdef JS_GC_ZEAL
-
-    /* Full GC with reset due to new zone, becoming zone GC. */
-
-    FinalizeCalls = 0;
-    JS_SetGCZeal(cx, 9, 1000000);
-    JS::PrepareForFullGC(cx);
-    js::SliceBudget budget(js::WorkBudget(1));
-    cx->gc.startDebugGC(GC_NORMAL, budget);
-    CHECK(cx->gc.state() == js::gc::State::Mark);
-    CHECK(cx->gc.isFullGc());
-
-    JS::RootedObject global4(cx, createTestGlobal());
-    budget = js::SliceBudget(js::WorkBudget(1));
-    cx->gc.debugGCSlice(budget);
-    while (cx->gc.isIncrementalGCInProgress())
-        cx->gc.debugGCSlice(budget);
-    CHECK(!cx->gc.isIncrementalGCInProgress());
-    CHECK(!cx->gc.isFullGc());
-    CHECK(checkMultipleGroups());
-    CHECK(checkFinalizeStatus());
-
-    for (unsigned i = 0; i < FinalizeCalls - 1; ++i)
-        CHECK(!IsZoneGCBuffer[i]);
-    CHECK(IsZoneGCBuffer[FinalizeCalls - 1]);
-
-    JS_SetGCZeal(cx, 0, 0);
-
-#endif
-
     /*
      * Make some use of the globals here to ensure the compiler doesn't optimize
      * them away in release builds, causing the zones to be collected and
diff --git a/js/src/jsapi-tests/testGCHeapPostBarriers.cpp b/js/src/jsapi-tests/testGCHeapPostBarriers.cpp
index 74512a53fa..00d47f1118 100644
--- a/js/src/jsapi-tests/testGCHeapPostBarriers.cpp
+++ b/js/src/jsapi-tests/testGCHeapPostBarriers.cpp
@@ -40,10 +40,6 @@ JSFunction* CreateGCThing(JSContext* cx)
 
 BEGIN_TEST(testGCHeapPostBarriers)
 {
-#ifdef JS_GC_ZEAL
-    AutoLeaveZeal nozeal(cx);
-#endif /* JS_GC_ZEAL */
-
     /* Sanity check - objects start in the nursery and then become tenured. */
     JS_GC(cx);
     JS::RootedObject obj(cx, CreateGCThing<JSObject>(cx));
diff --git a/js/src/jsapi-tests/testGCMarking.cpp b/js/src/jsapi-tests/testGCMarking.cpp
index 6843973921..b475c2d696 100644
--- a/js/src/jsapi-tests/testGCMarking.cpp
+++ b/js/src/jsapi-tests/testGCMarking.cpp
@@ -101,10 +101,6 @@ class CCWTestTracer : public JS::CallbackTracer {
 
 BEGIN_TEST(testTracingIncomingCCWs)
 {
-#ifdef JS_GC_ZEAL
-    // Disable zeal modes because this test needs to control exactly when the GC happens.
-    JS_SetGCZeal(cx, 0, 100);
-#endif
     JS_GC(cx);
 
     JS::RootedObject global1(cx, JS::CurrentGlobalOrNull(cx));
@@ -146,10 +142,6 @@ countWrappers(JSCompartment* comp)
 
 BEGIN_TEST(testDeadNurseryCCW)
 {
-#ifdef JS_GC_ZEAL
-    // Disable zeal modes because this test needs to control exactly when the GC happens.
-    JS_SetGCZeal(cx, 0, 100);
-#endif
     JS_GC(cx);
 
     JS::RootedObject global1(cx, JS::CurrentGlobalOrNull(cx));
@@ -177,10 +169,6 @@ END_TEST(testDeadNurseryCCW)
 
 BEGIN_TEST(testLiveNurseryCCW)
 {
-#ifdef JS_GC_ZEAL
-    // Disable zeal modes because this test needs to control exactly when the GC happens.
-    JS_SetGCZeal(cx, 0, 100);
-#endif
     JS_GC(cx);
 
     JS::RootedObject global1(cx, JS::CurrentGlobalOrNull(cx));
@@ -208,10 +196,6 @@ END_TEST(testLiveNurseryCCW)
 
 BEGIN_TEST(testLiveNurseryWrapperCCW)
 {
-#ifdef JS_GC_ZEAL
-    // Disable zeal modes because this test needs to control exactly when the GC happens.
-    JS_SetGCZeal(cx, 0, 100);
-#endif
     JS_GC(cx);
 
     JS::RootedObject global1(cx, JS::CurrentGlobalOrNull(cx));
@@ -244,10 +228,6 @@ END_TEST(testLiveNurseryWrapperCCW)
 
 BEGIN_TEST(testLiveNurseryWrappeeCCW)
 {
-#ifdef JS_GC_ZEAL
-    // Disable zeal modes because this test needs to control exactly when the GC happens.
-    JS_SetGCZeal(cx, 0, 100);
-#endif
     JS_GC(cx);
 
     JS::RootedObject global1(cx, JS::CurrentGlobalOrNull(cx));
@@ -280,11 +260,6 @@ BEGIN_TEST(testIncrementalRoots)
 {
     JSRuntime* rt = cx->runtime();
 
-#ifdef JS_GC_ZEAL
-    // Disable zeal modes because this test needs to control exactly when the GC happens.
-    JS_SetGCZeal(cx, 0, 100);
-#endif
-
     // Construct a big object graph to mark. In JS, the resulting object graph
     // is equivalent to:
     //
diff --git a/js/src/jsapi-tests/testGCUniqueId.cpp b/js/src/jsapi-tests/testGCUniqueId.cpp
index 71d66b7221..d03d51b045 100644
--- a/js/src/jsapi-tests/testGCUniqueId.cpp
+++ b/js/src/jsapi-tests/testGCUniqueId.cpp
@@ -23,10 +23,6 @@ MinimizeHeap(JSContext* cx)
 
 BEGIN_TEST(testGCUID)
 {
-#ifdef JS_GC_ZEAL
-    AutoLeaveZeal nozeal(cx);
-#endif /* JS_GC_ZEAL */
-
     uint64_t uid = 0;
     uint64_t tmp = 0;
 
diff --git a/js/src/jsapi-tests/tests.h b/js/src/jsapi-tests/tests.h
index 9955621ef1..7f7309c161 100644
--- a/js/src/jsapi-tests/tests.h
+++ b/js/src/jsapi-tests/tests.h
@@ -418,39 +418,4 @@ class TestJSPrincipals : public JSPrincipals
     }
 };
 
-#ifdef JS_GC_ZEAL
-/*
- * Temporarily disable the GC zeal setting. This is only useful in tests that
- * need very explicit GC behavior and should not be used elsewhere.
- */
-class AutoLeaveZeal
-{
-    JSContext* cx_;
-    uint32_t zealBits_;
-    uint32_t frequency_;
-
-  public:
-    explicit AutoLeaveZeal(JSContext* cx) : cx_(cx) {
-        uint32_t dummy;
-        JS_GetGCZealBits(cx_, &zealBits_, &frequency_, &dummy);
-        JS_SetGCZeal(cx_, 0, 0);
-        JS::PrepareForFullGC(cx_);
-        JS::GCForReason(cx_, GC_SHRINK, JS::gcreason::DEBUG_GC);
-    }
-    ~AutoLeaveZeal() {
-        for (size_t i = 0; i < sizeof(zealBits_) * 8; i++) {
-            if (zealBits_ & (1 << i))
-                JS_SetGCZeal(cx_, i, frequency_);
-        }
-
-#ifdef DEBUG
-        uint32_t zealBitsAfter, frequencyAfter, dummy;
-        JS_GetGCZealBits(cx_, &zealBitsAfter, &frequencyAfter, &dummy);
-        MOZ_ASSERT(zealBitsAfter == zealBits_);
-        MOZ_ASSERT(frequencyAfter == frequency_);
-#endif
-    }
-};
-#endif /* JS_GC_ZEAL */
-
 #endif /* jsapi_tests_tests_h */
diff --git a/js/src/jsapi.cpp b/js/src/jsapi.cpp
index e4e86effac..ee9c610594 100644
--- a/js/src/jsapi.cpp
+++ b/js/src/jsapi.cpp
@@ -6263,26 +6263,6 @@ JS_AbortIfWrongThread(JSContext* cx)
         MOZ_CRASH();
 }
 
-#ifdef JS_GC_ZEAL
-JS_PUBLIC_API(void)
-JS_GetGCZealBits(JSContext* cx, uint32_t* zealBits, uint32_t* frequency, uint32_t* nextScheduled)
-{
-    cx->runtime()->gc.getZealBits(zealBits, frequency, nextScheduled);
-}
-
-JS_PUBLIC_API(void)
-JS_SetGCZeal(JSContext* cx, uint8_t zeal, uint32_t frequency)
-{
-    cx->gc.setZeal(zeal, frequency);
-}
-
-JS_PUBLIC_API(void)
-JS_ScheduleGC(JSContext* cx, uint32_t count)
-{
-    cx->runtime()->gc.setNextScheduled(count);
-}
-#endif
-
 JS_PUBLIC_API(void)
 JS_SetParallelParsingEnabled(JSContext* cx, bool enabled)
 {
diff --git a/js/src/jsapi.h b/js/src/jsapi.h
index 6700a6c514..9ad3e757ff 100644
--- a/js/src/jsapi.h
+++ b/js/src/jsapi.h
@@ -5761,19 +5761,6 @@ JS_NewObjectForConstructor(JSContext* cx, const JSClass* clasp, const JS::CallAr
 
 /************************************************************************/
 
-#ifdef JS_GC_ZEAL
-#define JS_DEFAULT_ZEAL_FREQ 100
-
-extern JS_PUBLIC_API(void)
-JS_GetGCZealBits(JSContext* cx, uint32_t* zealBits, uint32_t* frequency, uint32_t* nextScheduled);
-
-extern JS_PUBLIC_API(void)
-JS_SetGCZeal(JSContext* cx, uint8_t zeal, uint32_t frequency);
-
-extern JS_PUBLIC_API(void)
-JS_ScheduleGC(JSContext* cx, uint32_t count);
-#endif
-
 extern JS_PUBLIC_API(void)
 JS_SetParallelParsingEnabled(JSContext* cx, bool enabled);
 
diff --git a/js/src/jsgc.cpp b/js/src/jsgc.cpp
index 42d10283c4..45301dac87 100644
--- a/js/src/jsgc.cpp
+++ b/js/src/jsgc.cpp
@@ -844,9 +844,6 @@ GCRuntime::GCRuntime(JSRuntime* rt) :
     arenasAllocatedDuringSweep(nullptr),
     startedCompacting(false),
     relocatedArenasToRelease(nullptr),
-#ifdef JS_GC_ZEAL
-    markingValidator(nullptr),
-#endif
     interFrameGC(false),
     defaultTimeBudget_(SliceBudget::UnlimitedTimeBudget),
     incrementalAllowed(true),
@@ -856,13 +853,6 @@ GCRuntime::GCRuntime(JSRuntime* rt) :
     manipulatingDeadZones(false),
     objectsMarkedInDeadZones(0),
     poked(false),
-#ifdef JS_GC_ZEAL
-    zealModeBits(0),
-    zealFrequency(0),
-    nextScheduled(0),
-    deterministicOnly(false),
-    incrementalLimit(0),
-#endif
     fullCompartmentChecks(false),
     mallocBytesUntilGC(0),
     mallocGCTriggered(false),
@@ -881,147 +871,6 @@ GCRuntime::GCRuntime(JSRuntime* rt) :
     setGCMode(JSGC_MODE_GLOBAL);
 }
 
-#ifdef JS_GC_ZEAL
-
-void
-GCRuntime::getZealBits(uint32_t* zealBits, uint32_t* frequency, uint32_t* scheduled)
-{
-    *zealBits = zealModeBits;
-    *frequency = zealFrequency;
-    *scheduled = nextScheduled;
-}
-
-const char* gc::ZealModeHelpText =
-    "  Specifies how zealous the garbage collector should be. Some of these modes can\n"
-    "  be set simultaneously, by passing multiple level options, e.g. \"2;4\" will activate\n"
-    "  both modes 2 and 4. Modes can be specified by name or number.\n"
-    "  \n"
-    "  Values:\n"
-    "    0: (None) Normal amount of collection (resets all modes)\n"
-    "    1: (Poke) Collect when roots are added or removed\n"
-    "    2: (Alloc) Collect when every N allocations (default: 100)\n"
-    "    3: (FrameGC) Collect when the window paints (browser only)\n"
-    "    4: (VerifierPre) Verify pre write barriers between instructions\n"
-    "    5: (FrameVerifierPre) Verify pre write barriers between paints\n"
-    "    6: (StackRooting) Verify stack rooting\n"
-    "    7: (GenerationalGC) Collect the nursery every N nursery allocations\n"
-    "    8: (IncrementalRootsThenFinish) Incremental GC in two slices: 1) mark roots 2) finish collection\n"
-    "    9: (IncrementalMarkAllThenFinish) Incremental GC in two slices: 1) mark all 2) new marking and finish\n"
-    "   10: (IncrementalMultipleSlices) Incremental GC in multiple slices\n"
-    "   11: (IncrementalMarkingValidator) Verify incremental marking\n"
-    "   12: (ElementsBarrier) Always use the individual element post-write barrier, regardless of elements size\n"
-    "   13: (CheckHashTablesOnMinorGC) Check internal hashtables on minor GC\n"
-    "   14: (Compact) Perform a shrinking collection every N allocations\n"
-    "   15: (CheckHeapAfterGC) Walk the heap to check its integrity after every GC\n"
-    "   16: (CheckNursery) Check nursery integrity on minor GC\n";
-
-void
-GCRuntime::setZeal(uint8_t zeal, uint32_t frequency)
-{
-    MOZ_ASSERT(zeal <= unsigned(ZealMode::Limit));
-
-    if (verifyPreData)
-        VerifyBarriers(rt, PreBarrierVerifier);
-
-    if (zeal == 0 && hasZealMode(ZealMode::GenerationalGC)) {
-        evictNursery(JS::gcreason::DEBUG_GC);
-        nursery.leaveZealMode();
-    }
-
-    ZealMode zealMode = ZealMode(zeal);
-    if (zealMode == ZealMode::GenerationalGC)
-        nursery.enterZealMode();
-
-    // Zeal modes 8-10 are mutually exclusive. If we're setting one of those,
-    // we first reset all of them.
-    if (zealMode >= ZealMode::IncrementalRootsThenFinish &&
-        zealMode <= ZealMode::IncrementalMultipleSlices)
-    {
-        clearZealMode(ZealMode::IncrementalRootsThenFinish);
-        clearZealMode(ZealMode::IncrementalMarkAllThenFinish);
-        clearZealMode(ZealMode::IncrementalMultipleSlices);
-    }
-
-    bool schedule = zealMode >= ZealMode::Alloc;
-    if (zeal != 0)
-        zealModeBits |= 1 << unsigned(zeal);
-    else
-        zealModeBits = 0;
-    zealFrequency = frequency;
-    nextScheduled = schedule ? frequency : 0;
-}
-
-void
-GCRuntime::setNextScheduled(uint32_t count)
-{
-    nextScheduled = count;
-}
-
-bool
-GCRuntime::parseAndSetZeal(const char* str)
-{
-    int frequency = -1;
-    bool foundFrequency = false;
-    mozilla::Vector<int, 0, SystemAllocPolicy> zeals;
-
-    static const struct {
-        const char* const zealMode;
-        size_t length;
-        uint32_t zeal;
-    } zealModes[] = {
-#define ZEAL_MODE(name, value) {#name, sizeof(#name) - 1, value},
-        JS_FOR_EACH_ZEAL_MODE(ZEAL_MODE)
-#undef ZEAL_MODE
-        {"None", 4, 0}
-    };
-
-    do {
-        int zeal = -1;
-
-        const char* p = nullptr;
-        if (isdigit(str[0])) {
-            zeal = atoi(str);
-
-            size_t offset = strspn(str, "0123456789");
-            p = str + offset;
-        } else {
-            for (auto z : zealModes) {
-                if (!strncmp(str, z.zealMode, z.length)) {
-                    zeal = z.zeal;
-                    p = str + z.length;
-                    break;
-                }
-            }
-        }
-        if (p) {
-            if (!*p || *p == ';') {
-                frequency = JS_DEFAULT_ZEAL_FREQ;
-            } else if (*p == ',') {
-                frequency = atoi(p + 1);
-                foundFrequency = true;
-            }
-        }
-
-        if (zeal < 0 || zeal > int(ZealMode::Limit) || frequency <= 0) {
-            fprintf(stderr, "Format: JS_GC_ZEAL=level(;level)*[,N]\n");
-            fputs(ZealModeHelpText, stderr);
-            return false;
-        }
-
-        if (!zeals.emplaceBack(zeal)) {
-            return false;
-        }
-    } while (!foundFrequency &&
-             (str = strchr(str, ';')) != nullptr &&
-             str++);
-
-    for (auto z : zeals)
-        setZeal(z, frequency);
-    return true;
-}
-
-#endif
-
 /*
  * Lifetime in number of major GCs for type sets attached to scripts containing
  * observed types.
@@ -1063,12 +912,6 @@ GCRuntime::init(uint32_t maxbytes, uint32_t maxNurseryBytes)
         }
     }
 
-#ifdef JS_GC_ZEAL
-    const char* zealSpec = getenv("JS_GC_ZEAL");
-    if (zealSpec && zealSpec[0] && !parseAndSetZeal(zealSpec))
-        return false;
-#endif
-
     if (!InitTrace(*this))
         return false;
 
@@ -1094,11 +937,6 @@ GCRuntime::finish()
     allocTask.cancel(GCParallelTask::CancelAndWait);
     decommitTask.cancel(GCParallelTask::CancelAndWait);
 
-#ifdef JS_GC_ZEAL
-    /* Free memory associated with GC verification. */
-    finishVerifier();
-#endif
-
     /* Delete all remaining zones. */
     if (rt->gcInitialized) {
         AutoSetThreadIsSweeping threadIsSweeping;
@@ -1315,7 +1153,6 @@ GCRuntime::setMarkStackLimit(size_t limit, AutoLockGC& lock)
 {
     MOZ_ASSERT(!rt->isHeapBusy());
     AutoUnlockGC unlock(lock);
-    AutoStopVerifyingBarriers pauseVerification(rt, false);
     marker.setMaxCapacity(limit);
 }
 
@@ -2635,7 +2472,7 @@ GCRuntime::releaseRelocatedArenasWithoutUnlocking(Arena* arenaList, const AutoLo
         // Mark arena as empty
         arena->setAsFullyUnused();
 
-#if defined(JS_CRASH_DIAGNOSTICS) || defined(JS_GC_ZEAL)
+#if defined(JS_CRASH_DIAGNOSTICS)
         JS_POISON(reinterpret_cast<void*>(arena->thingsStart()),
                   JS_MOVED_TENURED_PATTERN, arena->getThingsSpan());
 #endif
@@ -3048,13 +2885,6 @@ GCRuntime::triggerZoneGC(Zone* zone, JS::gcreason::Reason reason)
     if (rt->isHeapCollecting())
         return false;
 
-#ifdef JS_GC_ZEAL
-    if (hasZealMode(ZealMode::Alloc)) {
-        MOZ_RELEASE_ASSERT(triggerGC(reason));
-        return true;
-    }
-#endif
-
     if (zone->isAtomsZone()) {
         /* We can't do a zone GC of the atoms compartment. */
         if (rt->keepAtoms()) {
@@ -3077,14 +2907,6 @@ GCRuntime::maybeGC(Zone* zone)
 {
     MOZ_ASSERT(CurrentThreadCanAccessRuntime(rt));
 
-#ifdef JS_GC_ZEAL
-    if (hasZealMode(ZealMode::Alloc) || hasZealMode(ZealMode::Poke)) {
-        JS::PrepareForFullGC(rt->contextFromMainThread());
-        gc(GC_NORMAL, JS::gcreason::DEBUG_GC);
-        return;
-    }
-#endif
-
     if (gcIfRequested())
         return;
 
@@ -3418,11 +3240,6 @@ GCRuntime::shouldReleaseObservedTypes()
 {
     bool releaseTypes = false;
 
-#ifdef JS_GC_ZEAL
-    if (zealModeBits != 0)
-        releaseTypes = true;
-#endif
-
     /* We may miss the exact target GC due to resets. */
     if (majorGCNumber >= jitReleaseNumber)
         releaseTypes = true;
@@ -4068,292 +3885,6 @@ GCRuntime::markAllGrayReferences(gcstats::Phase phase)
     markGrayReferences<GCZonesIter, GCCompartmentsIter>(phase);
 }
 
-#ifdef JS_GC_ZEAL
-
-struct GCChunkHasher {
-    typedef gc::Chunk* Lookup;
-
-    /*
-     * Strip zeros for better distribution after multiplying by the golden
-     * ratio.
-     */
-    static HashNumber hash(gc::Chunk* chunk) {
-        MOZ_ASSERT(!(uintptr_t(chunk) & gc::ChunkMask));
-        return HashNumber(uintptr_t(chunk) >> gc::ChunkShift);
-    }
-
-    static bool match(gc::Chunk* k, gc::Chunk* l) {
-        MOZ_ASSERT(!(uintptr_t(k) & gc::ChunkMask));
-        MOZ_ASSERT(!(uintptr_t(l) & gc::ChunkMask));
-        return k == l;
-    }
-};
-
-class js::gc::MarkingValidator
-{
-  public:
-    explicit MarkingValidator(GCRuntime* gc);
-    ~MarkingValidator();
-    void nonIncrementalMark(AutoLockForExclusiveAccess& lock);
-    void validate();
-
-  private:
-    GCRuntime* gc;
-    bool initialized;
-
-    typedef HashMap<Chunk*, ChunkBitmap*, GCChunkHasher, SystemAllocPolicy> BitmapMap;
-    BitmapMap map;
-};
-
-js::gc::MarkingValidator::MarkingValidator(GCRuntime* gc)
-  : gc(gc),
-    initialized(false)
-{}
-
-js::gc::MarkingValidator::~MarkingValidator()
-{
-    if (!map.initialized())
-        return;
-
-    for (BitmapMap::Range r(map.all()); !r.empty(); r.popFront())
-        js_delete(r.front().value());
-}
-
-void
-js::gc::MarkingValidator::nonIncrementalMark(AutoLockForExclusiveAccess& lock)
-{
-    /*
-     * Perform a non-incremental mark for all collecting zones and record
-     * the results for later comparison.
-     *
-     * Currently this does not validate gray marking.
-     */
-
-    if (!map.init())
-        return;
-
-    JSRuntime* runtime = gc->rt;
-    GCMarker* gcmarker = &gc->marker;
-
-    gc->waitBackgroundSweepEnd();
-
-    /* Save existing mark bits. */
-    for (auto chunk = gc->allNonEmptyChunks(); !chunk.done(); chunk.next()) {
-        ChunkBitmap* bitmap = &chunk->bitmap;
-	ChunkBitmap* entry = js_new<ChunkBitmap>();
-        if (!entry)
-            return;
-
-        memcpy((void*)entry->bitmap, (void*)bitmap->bitmap, sizeof(bitmap->bitmap));
-        if (!map.putNew(chunk, entry))
-            return;
-    }
-
-    /*
-     * Temporarily clear the weakmaps' mark flags for the compartments we are
-     * collecting.
-     */
-
-    WeakMapSet markedWeakMaps;
-    if (!markedWeakMaps.init())
-        return;
-
-    /*
-     * For saving, smush all of the keys into one big table and split them back
-     * up into per-zone tables when restoring.
-     */
-    gc::WeakKeyTable savedWeakKeys(SystemAllocPolicy(), runtime->randomHashCodeScrambler());
-    if (!savedWeakKeys.init())
-        return;
-
-    for (GCZonesIter zone(runtime); !zone.done(); zone.next()) {
-        if (!WeakMapBase::saveZoneMarkedWeakMaps(zone, markedWeakMaps))
-            return;
-
-        AutoEnterOOMUnsafeRegion oomUnsafe;
-        for (gc::WeakKeyTable::Range r = zone->gcWeakKeys.all(); !r.empty(); r.popFront()) {
-            if (!savedWeakKeys.put(Move(r.front().key), Move(r.front().value)))
-                oomUnsafe.crash("saving weak keys table for validator");
-        }
-
-        if (!zone->gcWeakKeys.clear())
-            oomUnsafe.crash("clearing weak keys table for validator");
-    }
-
-    /*
-     * After this point, the function should run to completion, so we shouldn't
-     * do anything fallible.
-     */
-    initialized = true;
-
-    /* Re-do all the marking, but non-incrementally. */
-    js::gc::State state = gc->incrementalState;
-    gc->incrementalState = State::MarkRoots;
-
-    {
-        gcstats::AutoPhase ap(gc->stats, gcstats::PHASE_MARK);
-
-        {
-            gcstats::AutoPhase ap(gc->stats, gcstats::PHASE_UNMARK);
-
-            for (GCZonesIter zone(runtime); !zone.done(); zone.next())
-                WeakMapBase::unmarkZone(zone);
-
-            MOZ_ASSERT(gcmarker->isDrained());
-            gcmarker->reset();
-
-            for (auto chunk = gc->allNonEmptyChunks(); !chunk.done(); chunk.next())
-                chunk->bitmap.clear();
-        }
-
-        gc->traceRuntimeForMajorGC(gcmarker, lock);
-
-        gc->incrementalState = State::Mark;
-        auto unlimited = SliceBudget::unlimited();
-        MOZ_RELEASE_ASSERT(gc->marker.drainMarkStack(unlimited));
-    }
-
-    gc->incrementalState = State::Sweep;
-    {
-        gcstats::AutoPhase ap1(gc->stats, gcstats::PHASE_SWEEP);
-        gcstats::AutoPhase ap2(gc->stats, gcstats::PHASE_SWEEP_MARK);
-
-        gc->markAllWeakReferences(gcstats::PHASE_SWEEP_MARK_WEAK);
-
-        /* Update zone state for gray marking. */
-        for (GCZonesIter zone(runtime); !zone.done(); zone.next()) {
-            MOZ_ASSERT(zone->isGCMarkingBlack());
-            zone->setGCState(Zone::MarkGray);
-        }
-        gc->marker.setMarkColorGray();
-
-        gc->markAllGrayReferences(gcstats::PHASE_SWEEP_MARK_GRAY);
-        gc->markAllWeakReferences(gcstats::PHASE_SWEEP_MARK_GRAY_WEAK);
-
-        /* Restore zone state. */
-        for (GCZonesIter zone(runtime); !zone.done(); zone.next()) {
-            MOZ_ASSERT(zone->isGCMarkingGray());
-            zone->setGCState(Zone::Mark);
-        }
-        MOZ_ASSERT(gc->marker.isDrained());
-        gc->marker.setMarkColorBlack();
-    }
-
-    /* Take a copy of the non-incremental mark state and restore the original. */
-    for (auto chunk = gc->allNonEmptyChunks(); !chunk.done(); chunk.next()) {
-        ChunkBitmap* bitmap = &chunk->bitmap;
-        ChunkBitmap* entry = map.lookup(chunk)->value();
-        Swap(*entry, *bitmap);
-    }
-
-    for (GCZonesIter zone(runtime); !zone.done(); zone.next()) {
-        WeakMapBase::unmarkZone(zone);
-        AutoEnterOOMUnsafeRegion oomUnsafe;
-        if (!zone->gcWeakKeys.clear())
-            oomUnsafe.crash("clearing weak keys table for validator");
-    }
-
-    WeakMapBase::restoreMarkedWeakMaps(markedWeakMaps);
-
-    for (gc::WeakKeyTable::Range r = savedWeakKeys.all(); !r.empty(); r.popFront()) {
-        AutoEnterOOMUnsafeRegion oomUnsafe;
-        Zone* zone = gc::TenuredCell::fromPointer(r.front().key.asCell())->zone();
-        if (!zone->gcWeakKeys.put(Move(r.front().key), Move(r.front().value)))
-            oomUnsafe.crash("restoring weak keys table for validator");
-    }
-
-    gc->incrementalState = state;
-}
-
-void
-js::gc::MarkingValidator::validate()
-{
-    /*
-     * Validates the incremental marking for a single compartment by comparing
-     * the mark bits to those previously recorded for a non-incremental mark.
-     */
-
-    if (!initialized)
-        return;
-
-    gc->waitBackgroundSweepEnd();
-
-    for (auto chunk = gc->allNonEmptyChunks(); !chunk.done(); chunk.next()) {
-        BitmapMap::Ptr ptr = map.lookup(chunk);
-        if (!ptr)
-            continue;  /* Allocated after we did the non-incremental mark. */
-
-        ChunkBitmap* bitmap = ptr->value();
-        ChunkBitmap* incBitmap = &chunk->bitmap;
-
-        for (size_t i = 0; i < ArenasPerChunk; i++) {
-            if (chunk->decommittedArenas.get(i))
-                continue;
-            Arena* arena = &chunk->arenas[i];
-            if (!arena->allocated())
-                continue;
-            if (!arena->zone->isGCSweeping())
-                continue;
-            if (arena->allocatedDuringIncremental)
-                continue;
-
-            AllocKind kind = arena->getAllocKind();
-            uintptr_t thing = arena->thingsStart();
-            uintptr_t end = arena->thingsEnd();
-            while (thing < end) {
-                Cell* cell = (Cell*)thing;
-
-                /*
-                 * If a non-incremental GC wouldn't have collected a cell, then
-                 * an incremental GC won't collect it.
-                 */
-                MOZ_ASSERT_IF(bitmap->isMarked(cell, BLACK), incBitmap->isMarked(cell, BLACK));
-
-                /*
-                 * If the cycle collector isn't allowed to collect an object
-                 * after a non-incremental GC has run, then it isn't allowed to
-                 * collected it after an incremental GC.
-                 */
-                MOZ_ASSERT_IF(!bitmap->isMarked(cell, GRAY), !incBitmap->isMarked(cell, GRAY));
-
-                thing += Arena::thingSize(kind);
-            }
-        }
-    }
-}
-
-#endif // JS_GC_ZEAL
-
-void
-GCRuntime::computeNonIncrementalMarkingForValidation(AutoLockForExclusiveAccess& lock)
-{
-#ifdef JS_GC_ZEAL
-    MOZ_ASSERT(!markingValidator);
-    if (isIncremental && hasZealMode(ZealMode::IncrementalMarkingValidator))
-        markingValidator = js_new<MarkingValidator>(this);
-    if (markingValidator)
-        markingValidator->nonIncrementalMark(lock);
-#endif
-}
-
-void
-GCRuntime::validateIncrementalMarking()
-{
-#ifdef JS_GC_ZEAL
-    if (markingValidator)
-        markingValidator->validate();
-#endif
-}
-
-void
-GCRuntime::finishMarkingValidation()
-{
-#ifdef JS_GC_ZEAL
-    js_delete(markingValidator);
-    markingValidator = nullptr;
-#endif
-}
-
 static void
 DropStringWrappers(JSRuntime* rt)
 {
@@ -4988,8 +4519,6 @@ GCRuntime::beginSweepingZoneGroup(AutoLockForExclusiveAccess& lock)
 #endif
     }
 
-    validateIncrementalMarking();
-
     FreeOp fop(rt);
     SweepAtomsTask sweepAtomsTask(rt);
     SweepCCWrappersTask sweepCCWrappersTask(rt);
@@ -5215,8 +4744,6 @@ GCRuntime::beginSweepPhase(bool destroyingRuntime, AutoLockForExclusiveAccess& l
 
     releaseHeldRelocatedArenas();
 
-    computeNonIncrementalMarkingForValidation(lock);
-
     gcstats::AutoPhase ap(stats, gcstats::PHASE_SWEEP);
 
     sweepOnBackgroundThread =
@@ -5462,8 +4989,6 @@ GCRuntime::endSweepPhase(bool destroyingRuntime, AutoLockForExclusiveAccess& loc
             rt->setGCGrayBitsValid(true);
     }
 
-    finishMarkingValidation();
-
 #ifdef DEBUG
     for (ZonesIter zone(rt, WithAtoms); !zone.done(); zone.next()) {
         for (auto i : AllAllocKinds()) {
@@ -5782,16 +5307,6 @@ AutoGCSlice::~AutoGCSlice()
     }
 }
 
-void
-GCRuntime::pushZealSelectedObjects()
-{
-#ifdef JS_GC_ZEAL
-    /* Push selected objects onto the mark stack and clear the list. */
-    for (JSObject** obj = selectedForMarking.begin(); obj != selectedForMarking.end(); obj++)
-        TraceManuallyBarrieredEdge(&marker, obj, "selected obj");
-#endif
-}
-
 static bool
 IsShutdownGC(JS::gcreason::Reason reason)
 {
@@ -5817,31 +5332,9 @@ GCRuntime::incrementalCollectSlice(SliceBudget& budget, JS::gcreason::Reason rea
 
     gc::State initialState = incrementalState;
 
-    bool useZeal = false;
-#ifdef JS_GC_ZEAL
-    if (reason == JS::gcreason::DEBUG_GC && !budget.isUnlimited()) {
-        /*
-         * Do the incremental collection type specified by zeal mode if the
-         * collection was triggered by runDebugGC() and incremental GC has not
-         * been cancelled by resetIncrementalGC().
-         */
-        useZeal = true;
-    }
-#endif
-
     MOZ_ASSERT_IF(isIncrementalGCInProgress(), isIncremental);
     isIncremental = !budget.isUnlimited();
 
-    if (useZeal && (hasZealMode(ZealMode::IncrementalRootsThenFinish) ||
-                    hasZealMode(ZealMode::IncrementalMarkAllThenFinish)))
-    {
-        /*
-         * Yields between slices occurs at predetermined points in these modes;
-         * the budget is not used.
-         */
-        budget.makeUnlimited();
-    }
-
     switch (incrementalState) {
       case State::NotActive:
         initialReason = reason;
@@ -5859,14 +5352,8 @@ GCRuntime::incrementalCollectSlice(SliceBudget& budget, JS::gcreason::Reason rea
             return;
         }
 
-        if (!destroyingRuntime)
-            pushZealSelectedObjects();
-
         incrementalState = State::Mark;
 
-        if (isIncremental && useZeal && hasZealMode(ZealMode::IncrementalRootsThenFinish))
-            break;
-
         MOZ_FALLTHROUGH;
 
       case State::Mark:
@@ -5895,10 +5382,7 @@ GCRuntime::incrementalCollectSlice(SliceBudget& budget, JS::gcreason::Reason rea
          * We will need to mark anything new on the stack when we resume, so
          * we stay in Mark state.
          */
-        if (!lastMarkSlice && isIncremental &&
-            ((initialState == State::Mark &&
-              !(useZeal && hasZealMode(ZealMode::IncrementalRootsThenFinish))) ||
-             (useZeal && hasZealMode(ZealMode::IncrementalMarkAllThenFinish))))
+        if (!lastMarkSlice && isIncremental && initialState == State::Mark)
         {
             lastMarkSlice = true;
             break;
@@ -5914,13 +5398,6 @@ GCRuntime::incrementalCollectSlice(SliceBudget& budget, JS::gcreason::Reason rea
         if (budget.isOverBudget())
             break;
 
-        /*
-         * Always yield here when running in incremental multi-slice zeal
-         * mode, so RunDebugGC can reset the slice buget.
-         */
-        if (isIncremental && useZeal && hasZealMode(ZealMode::IncrementalMultipleSlices))
-            break;
-
         MOZ_FALLTHROUGH;
 
       case State::Sweep:
@@ -6202,11 +5679,6 @@ GCRuntime::gcCycle(bool nonincrementalByAPI, SliceBudget& budget, JS::gcreason::
 
     chunkAllocationSinceLastGC = false;
 
-#ifdef JS_GC_ZEAL
-    /* Keeping these around after a GC is dangerous. */
-    clearSelectedForMarking();
-#endif
-
     /* Clear gcMallocBytes for all zones. */
     for (ZonesIter zone(rt, WithAtoms); !zone.done(); zone.next())
         zone->resetGCMallocBytes();
@@ -6218,23 +5690,6 @@ GCRuntime::gcCycle(bool nonincrementalByAPI, SliceBudget& budget, JS::gcreason::
     return false;
 }
 
-#ifdef JS_GC_ZEAL
-static bool
-IsDeterministicGCReason(JS::gcreason::Reason reason)
-{
-    if (reason > JS::gcreason::DEBUG_GC &&
-        reason != JS::gcreason::CC_FORCED && reason != JS::gcreason::SHUTDOWN_CC)
-    {
-        return false;
-    }
-
-    if (reason == JS::gcreason::EAGER_ALLOC_TRIGGER)
-        return false;
-
-    return true;
-}
-#endif
-
 gcstats::ZoneGCStats
 GCRuntime::scanZonesBeforeGC()
 {
@@ -6300,11 +5755,6 @@ GCRuntime::checkIfGCAllowedInCurrentState(JS::gcreason::Reason reason)
     if (rt->isBeingDestroyed() && !IsShutdownGC(reason))
         return false;
 
-#ifdef JS_GC_ZEAL
-    if (deterministicOnly && !IsDeterministicGCReason(reason))
-        return false;
-#endif
-
     return true;
 }
 
@@ -6319,7 +5769,6 @@ GCRuntime::collect(bool nonincrementalByAPI, SliceBudget budget, JS::gcreason::R
         return;
 
     AutoTraceLog logGC(TraceLoggerForMainThread(rt), TraceLogger_GC);
-    AutoStopVerifyingBarriers av(rt, IsShutdownGC(reason));
     AutoEnqueuePendingParseTasksAfterGC aept(*this);
     AutoScheduleZonesForGC asz(rt);
 
@@ -6360,13 +5809,6 @@ GCRuntime::collect(bool nonincrementalByAPI, SliceBudget budget, JS::gcreason::R
 
     if (reason == JS::gcreason::COMPARTMENT_REVIVED)
         maybeDoCycleCollection();
-
-#ifdef JS_GC_ZEAL
-    if (rt->hasZealMode(ZealMode::CheckHeapAfterGC)) {
-        gcstats::AutoPhase ap(rt->gc.stats, gcstats::PHASE_TRACE_HEAP);
-        CheckHeapAfterGC(rt);
-    }
-#endif
 }
 
 js::AutoEnqueuePendingParseTasksAfterGC::~AutoEnqueuePendingParseTasksAfterGC()
@@ -6442,7 +5884,6 @@ GCRuntime::abortGC()
     checkCanCallAPI();
     MOZ_ASSERT(!rt->mainThread.suppressGC);
 
-    AutoStopVerifyingBarriers av(rt, false);
     AutoEnqueuePendingParseTasksAfterGC aept(*this);
 
     gcstats::AutoGCSlice agc(stats, scanZonesBeforeGC(), invocationKind,
@@ -6460,17 +5901,6 @@ GCRuntime::notifyDidPaint()
 {
     MOZ_ASSERT(CurrentThreadCanAccessRuntime(rt));
 
-#ifdef JS_GC_ZEAL
-    if (hasZealMode(ZealMode::FrameVerifierPre))
-        verifyPreBarriers();
-
-    if (hasZealMode(ZealMode::FrameGC)) {
-        JS::PrepareForFullGC(rt->contextFromMainThread());
-        gc(GC_NORMAL, JS::gcreason::REFRESH_FRAME);
-        return;
-    }
-#endif
-
     if (isIncrementalGCInProgress() && !interFrameGC && tunables.areRefreshFrameSlicesEnabled()) {
         JS::PrepareForIncrementalGC(rt->contextFromMainThread());
         gcSlice(JS::gcreason::REFRESH_FRAME);
@@ -6566,11 +5996,6 @@ GCRuntime::minorGC(JS::gcreason::Reason reason, gcstats::Phase phase)
 
     blocksToFreeAfterMinorGC.freeAll();
 
-#ifdef JS_GC_ZEAL
-    if (rt->hasZealMode(ZealMode::CheckHeapAfterGC))
-        CheckHeapAfterGC(rt);
-#endif
-
     {
         AutoLockGC lock(rt);
         for (ZonesIter zone(rt, WithAtoms); !zone.done(); zone.next())
@@ -6754,92 +6179,12 @@ gc::MergeCompartments(JSCompartment* source, JSCompartment* target)
 }
 
 void
-GCRuntime::runDebugGC()
-{
-#ifdef JS_GC_ZEAL
-    if (rt->mainThread.suppressGC)
-        return;
-
-    if (hasZealMode(ZealMode::GenerationalGC))
-        return minorGC(JS::gcreason::DEBUG_GC);
-
-    PrepareForDebugGC(rt);
-
-    auto budget = SliceBudget::unlimited();
-    if (hasZealMode(ZealMode::IncrementalRootsThenFinish) ||
-        hasZealMode(ZealMode::IncrementalMarkAllThenFinish) ||
-        hasZealMode(ZealMode::IncrementalMultipleSlices))
-    {
-        js::gc::State initialState = incrementalState;
-        if (hasZealMode(ZealMode::IncrementalMultipleSlices)) {
-            /*
-             * Start with a small slice limit and double it every slice. This
-             * ensure that we get multiple slices, and collection runs to
-             * completion.
-             */
-            if (!isIncrementalGCInProgress())
-                incrementalLimit = zealFrequency / 2;
-            else
-                incrementalLimit *= 2;
-            budget = SliceBudget(WorkBudget(incrementalLimit));
-        } else {
-            // This triggers incremental GC but is actually ignored by IncrementalMarkSlice.
-            budget = SliceBudget(WorkBudget(1));
-        }
-
-        if (!isIncrementalGCInProgress())
-            invocationKind = GC_SHRINK;
-        collect(false, budget, JS::gcreason::DEBUG_GC);
-
-        /*
-         * For multi-slice zeal, reset the slice size when we get to the sweep
-         * or compact phases.
-         */
-        if (hasZealMode(ZealMode::IncrementalMultipleSlices)) {
-            if ((initialState == State::Mark && incrementalState == State::Sweep) ||
-                (initialState == State::Sweep && incrementalState == State::Compact))
-            {
-                incrementalLimit = zealFrequency / 2;
-            }
-        }
-    } else if (hasZealMode(ZealMode::Compact)) {
-        gc(GC_SHRINK, JS::gcreason::DEBUG_GC);
-    } else {
-        gc(GC_NORMAL, JS::gcreason::DEBUG_GC);
-    }
-
-#endif
-}
-
-void
 GCRuntime::setFullCompartmentChecks(bool enabled)
 {
     MOZ_ASSERT(!rt->isHeapMajorCollecting());
     fullCompartmentChecks = enabled;
 }
 
-#ifdef JS_GC_ZEAL
-bool
-GCRuntime::selectForMarking(JSObject* object)
-{
-    MOZ_ASSERT(!rt->isHeapMajorCollecting());
-    return selectedForMarking.append(object);
-}
-
-void
-GCRuntime::clearSelectedForMarking()
-{
-    selectedForMarking.clearAndFree();
-}
-
-void
-GCRuntime::setDeterministic(bool enabled)
-{
-    MOZ_ASSERT(!rt->isHeapMajorCollecting());
-    deterministicOnly = enabled;
-}
-#endif
-
 #ifdef DEBUG
 
 /* Should only be called manually under gdb */
@@ -7337,7 +6682,7 @@ JS::IsIncrementalGCEnabled(JSContext* cx)
 JS_PUBLIC_API(bool)
 JS::IsIncrementalGCInProgress(JSContext* cx)
 {
-    return cx->gc.isIncrementalGCInProgress() && !cx->gc.isVerifyPreBarriersEnabled();
+    return cx->gc.isIncrementalGCInProgress();
 }
 
 JS_PUBLIC_API(bool)
diff --git a/js/src/jsgc.h b/js/src/jsgc.h
index 79ac9596c5..7ad176d84e 100644
--- a/js/src/jsgc.h
+++ b/js/src/jsgc.h
@@ -1264,31 +1264,6 @@ enum VerifierType {
     PreBarrierVerifier
 };
 
-#ifdef JS_GC_ZEAL
-
-extern const char* ZealModeHelpText;
-
-/* Check that write barriers have been used correctly. See jsgc.cpp. */
-void
-VerifyBarriers(JSRuntime* rt, VerifierType type);
-
-void
-MaybeVerifyBarriers(JSContext* cx, bool always = false);
-
-#else
-
-static inline void
-VerifyBarriers(JSRuntime* rt, VerifierType type)
-{
-}
-
-static inline void
-MaybeVerifyBarriers(JSContext* cx, bool always = false)
-{
-}
-
-#endif
-
 /*
  * Instances of this class set the |JSRuntime::suppressGC| flag for the duration
  * that they are live. Use of this class is highly discouraged. Please carefully
diff --git a/js/src/jsgcinlines.h b/js/src/jsgcinlines.h
index 9cebb03a4d..c6988d7af4 100644
--- a/js/src/jsgcinlines.h
+++ b/js/src/jsgcinlines.h
@@ -42,12 +42,6 @@ inline void
 GCRuntime::poke()
 {
     poked = true;
-
-#ifdef JS_GC_ZEAL
-    /* Schedule a GC to happen "soon" after a GC poke. */
-    if (hasZealMode(ZealMode::Poke))
-        nextScheduled = 1;
-#endif
 }
 
 class ArenaIter
diff --git a/js/src/jspubtd.h b/js/src/jspubtd.h
index 309b9d7466..20ea1ef8b1 100644
--- a/js/src/jspubtd.h
+++ b/js/src/jspubtd.h
@@ -22,7 +22,7 @@
 #include "js/TraceKind.h"
 #include "js/TypeDecls.h"
 
-#if defined(JS_GC_ZEAL) || defined(DEBUG)
+#if defined(DEBUG)
 # define JSGC_HASH_TABLE_CHECKS
 #endif
 
diff --git a/js/src/jsutil.h b/js/src/jsutil.h
index 790b97ddca..8ef4cac908 100644
--- a/js/src/jsutil.h
+++ b/js/src/jsutil.h
@@ -368,7 +368,7 @@ Poison(void* ptr, uint8_t value, size_t num)
 #endif
 
 /* Enable poisoning in crash-diagnostics and zeal builds. */
-#if defined(JS_CRASH_DIAGNOSTICS) || defined(JS_GC_ZEAL)
+#if defined(JS_CRASH_DIAGNOSTICS)
 # define JS_POISON(p, val, size) Poison(p, val, size)
 #else
 # define JS_POISON(p, val, size) ((void) 0)
diff --git a/js/src/old-configure.in b/js/src/old-configure.in
index 1c5c9e2145..e4589b951b 100644
--- a/js/src/old-configure.in
+++ b/js/src/old-configure.in
@@ -1806,17 +1806,6 @@ if test -n "$MOZ_DEBUG"; then
 fi
 
 dnl ========================================================
-dnl Zealous JavaScript GC
-dnl ========================================================
-MOZ_ARG_ENABLE_BOOL(gczeal,
-[  --enable-gczeal         Enable zealous GCing],
-    JS_GC_ZEAL=1,
-    JS_GC_ZEAL= )
-if test -n "$JS_GC_ZEAL" -o -n "$MOZ_DEBUG"; then
-    AC_DEFINE(JS_GC_ZEAL)
-fi
-
-dnl ========================================================
 dnl Enable breakpoint for artificial OOMs
 dnl ========================================================
 MOZ_ARG_ENABLE_BOOL(oom-breakpoint,
diff --git a/js/src/shell/js.cpp b/js/src/shell/js.cpp
index 00a4a503ce..88d482a238 100644
--- a/js/src/shell/js.cpp
+++ b/js/src/shell/js.cpp
@@ -323,10 +323,6 @@ static bool enableNativeRegExp = false;
 static bool enableUnboxedArrays = false;
 static bool enableSharedMemory = SHARED_MEMORY_DEFAULT;
 static bool enableWasmAlwaysBaseline = false;
-#ifdef JS_GC_ZEAL
-static uint32_t gZealBits = 0;
-static uint32_t gZealFrequency = 0;
-#endif
 static bool printTiming = false;
 static const char* jsCacheDir = nullptr;
 static const char* jsCacheAsmJSPath = nullptr;
@@ -7517,16 +7513,6 @@ SetContextOptions(JSContext* cx, const OptionParser& op)
     dumpEntrainedVariables = op.getBoolOption("dump-entrained-variables");
 #endif
 
-#ifdef JS_GC_ZEAL
-    const char* zealStr = op.getStringOption("gc-zeal");
-    if (zealStr) {
-        if (!cx->gc.parseAndSetZeal(zealStr))
-            return false;
-        uint32_t nextScheduled;
-        cx->gc.getZealBits(&gZealBits, &gZealFrequency, &nextScheduled);
-    }
-#endif
-
     return true;
 }
 
@@ -7544,16 +7530,6 @@ SetWorkerContextOptions(JSContext* cx)
     cx->setOffthreadIonCompilationEnabled(offthreadCompilation);
     cx->profilingScripts = enableCodeCoverage || enableDisassemblyDumps;
 
-#ifdef JS_GC_ZEAL
-    if (gZealBits && gZealFrequency) {
-#define ZEAL_MODE(_, value)                        \
-        if (gZealBits & (1 << value))              \
-            cx->gc.setZeal(value, gZealFrequency);
-        JS_FOR_EACH_ZEAL_MODE(ZEAL_MODE)
-#undef ZEAL_MODE
-    }
-#endif
-
     JS_SetNativeStackQuota(cx, gMaxStackSize);
 }
 
@@ -7838,9 +7814,6 @@ main(int argc, char** argv, char** envp)
                             "NUMBER of instructions.", -1)
 #endif
         || !op.addIntOption('\0', "nursery-size", "SIZE-MB", "Set the maximum nursery size in MB", 16)
-#ifdef JS_GC_ZEAL
-        || !op.addStringOption('z', "gc-zeal", "LEVEL(;LEVEL)*[,N]", gc::ZealModeHelpText)
-#endif
         || !op.addStringOption('\0', "module-load-path", "DIR", "Set directory to load modules from")
     )
     {
diff --git a/js/src/tests/shell.js b/js/src/tests/shell.js
index 36dbc79dae..c7a57953ee 100644
--- a/js/src/tests/shell.js
+++ b/js/src/tests/shell.js
@@ -32,8 +32,6 @@
     // Certain cached functionality only exists (and is only needed) when
     // running in the browser.  Segregate that caching here.
 
-    var SpecialPowersSetGCZeal =
-      global.SpecialPowers ? global.SpecialPowers.setGCZeal : undefined;
   }
 
   var runningInShell = typeof window === "undefined";
@@ -205,19 +203,6 @@
     global.quit = quit;
   }
 
-  var gczeal = global.gczeal;
-  if (typeof gczeal !== "function") {
-    if (typeof SpecialPowersSetGCZeal === "function") {
-      gczeal = function gczeal(z) {
-        SpecialPowersSetGCZeal(z);
-      };
-    } else {
-      gczeal = function() {}; // no-op if not available
-    }
-
-    global.gczeal = gczeal;
-  }
-
   /******************************************************
    * TEST METADATA EXPORTS (these are of dubious value) *
    ******************************************************/
diff --git a/js/src/vm/Caches-inl.h b/js/src/vm/Caches-inl.h
index 4eb8ecaa63..56e69a0d99 100644
--- a/js/src/vm/Caches-inl.h
+++ b/js/src/vm/Caches-inl.h
@@ -57,9 +57,6 @@ NewObjectCache::newObjectFromHit(JSContext* cx, EntryIndex entryIndex, gc::Initi
     if (group->shouldPreTenure())
         heap = gc::TenuredHeap;
 
-    if (cx->runtime()->gc.upcomingZealousGC())
-        return nullptr;
-
     NativeObject* obj = static_cast<NativeObject*>(Allocate<JSObject, NoGC>(cx, entry->kind, 0,
                                                                             heap, group->clasp()));
     if (!obj)
diff --git a/js/src/vm/EnvironmentObject.h b/js/src/vm/EnvironmentObject.h
index 6bdaac89e8..d457ca8392 100644
--- a/js/src/vm/EnvironmentObject.h
+++ b/js/src/vm/EnvironmentObject.h
@@ -930,9 +930,6 @@ class DebugEnvironments
     void mark(JSTracer* trc);
     void sweep(JSRuntime* rt);
     void finish();
-#ifdef JS_GC_ZEAL
-    void checkHashTablesAfterMovingGC(JSRuntime* rt);
-#endif
 
     // If a live frame has a synthesized entry in missingEnvs, make sure it's not
     // collected.
diff --git a/js/src/vm/Interpreter.cpp b/js/src/vm/Interpreter.cpp
index 3ca379d018..fbf526ae5b 100644
--- a/js/src/vm/Interpreter.cpp
+++ b/js/src/vm/Interpreter.cpp
@@ -1647,7 +1647,6 @@ Interpret(JSContext* cx, RunState& state)
 #define ADVANCE_AND_DISPATCH(N)                                               \
     JS_BEGIN_MACRO                                                            \
         REGS.pc += (N);                                                       \
-        SANITY_CHECKS();                                                      \
         DISPATCH_TO(*REGS.pc | activation.opMask());                          \
     JS_END_MACRO
 
@@ -1727,12 +1726,6 @@ Interpret(JSContext* cx, RunState& state)
             activation.enableInterruptsUnconditionally();                     \
     JS_END_MACRO
 
-#define SANITY_CHECKS()                                                       \
-    JS_BEGIN_MACRO                                                            \
-        js::gc::MaybeVerifyBarriers(cx);                                      \
-    JS_END_MACRO
-
-    gc::MaybeVerifyBarriers(cx, true);
     MOZ_ASSERT(!cx->zone()->types.activeAnalysis);
 
     InterpreterFrame* entryFrame = state.pushInterpreterFrame(cx);
@@ -1863,7 +1856,6 @@ CASE(EnableInterruptsPseudoOpcode)
         activation.clearInterruptsMask();
 
     /* Commence executing the actual opcode. */
-    SANITY_CHECKS();
     DISPATCH_TO(op);
 }
 
@@ -4184,8 +4176,6 @@ DEFAULT()
         REGS.fp()->epilogue(cx, REGS.pc);
     }
 
-    gc::MaybeVerifyBarriers(cx, true);
-
     TraceLogStopEvent(logger, TraceLogger_Engine);
     TraceLogStopEvent(logger, scriptEvent);
 
diff --git a/js/src/vm/Runtime.cpp b/js/src/vm/Runtime.cpp
index 646d48299b..0d6a3922c4 100644
--- a/js/src/vm/Runtime.cpp
+++ b/js/src/vm/Runtime.cpp
@@ -868,8 +868,7 @@ bool
 JSRuntime::activeGCInAtomsZone()
 {
     Zone* zone = atomsCompartment_->zone();
-    return (zone->needsIncrementalBarrier() && !gc.isVerifyPreBarriersEnabled()) ||
-           zone->wasGCStarted();
+    return zone->needsIncrementalBarrier() || zone->wasGCStarted();
 }
 
 void
diff --git a/js/src/vm/Runtime.h b/js/src/vm/Runtime.h
index 4f7755b9d7..734543c4e3 100644
--- a/js/src/vm/Runtime.h
+++ b/js/src/vm/Runtime.h
@@ -866,8 +866,6 @@ struct JSRuntime : public JS::shadow::Runtime,
     /* Garbage collector state has been successfully initialized. */
     bool                gcInitialized;
 
-    bool hasZealMode(js::gc::ZealMode mode) { return gc.hasZealMode(mode); }
-
     void lockGC() {
         gc.lockGC();
     }