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diff --git a/Source/JavaScriptCore/b3/air/AirEliminateDeadCode.cpp b/Source/JavaScriptCore/b3/air/AirEliminateDeadCode.cpp
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+/*
+ * Copyright (C) 2015-2016 Apple Inc. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
+ * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE INC. OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+ * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+ * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+ * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
+ * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 
+ */
+
+#include "config.h"
+#include "AirEliminateDeadCode.h"
+
+#if ENABLE(B3_JIT)
+
+#include "AirCode.h"
+#include "AirInstInlines.h"
+#include "AirPhaseScope.h"
+#include <wtf/IndexSet.h>
+
+namespace JSC { namespace B3 { namespace Air {
+
+bool eliminateDeadCode(Code& code)
+{
+    PhaseScope phaseScope(code, "eliminateDeadCode");
+
+    HashSet<Tmp> liveTmps;
+    IndexSet<StackSlot> liveStackSlots;
+    bool changed;
+
+    auto isArgLive = [&] (const Arg& arg) -> bool {
+        switch (arg.kind()) {
+        case Arg::Tmp:
+            if (arg.isReg())
+                return true;
+            return liveTmps.contains(arg.tmp());
+        case Arg::Stack:
+            if (arg.stackSlot()->isLocked())
+                return true;
+            return liveStackSlots.contains(arg.stackSlot());
+        default:
+            return true;
+        }
+    };
+
+    auto addLiveArg = [&] (const Arg& arg) -> bool {
+        switch (arg.kind()) {
+        case Arg::Tmp:
+            if (arg.isReg())
+                return false;
+            return liveTmps.add(arg.tmp()).isNewEntry;
+        case Arg::Stack:
+            if (arg.stackSlot()->isLocked())
+                return false;
+            return liveStackSlots.add(arg.stackSlot());
+        default:
+            return false;
+        }
+    };
+
+    auto isInstLive = [&] (Inst& inst) -> bool {
+        if (inst.hasNonArgEffects())
+            return true;
+
+        // This instruction should be presumed dead, if its Args are all dead.
+        bool storesToLive = false;
+        inst.forEachArg(
+            [&] (Arg& arg, Arg::Role role, Arg::Type, Arg::Width) {
+                if (!Arg::isAnyDef(role))
+                    return;
+                if (role == Arg::Scratch)
+                    return;
+                storesToLive |= isArgLive(arg);
+            });
+        return storesToLive;
+    };
+
+    auto handleInst = [&] (Inst& inst) {
+        if (!isInstLive(inst))
+            return;
+
+        // We get here if the Inst is live. For simplicity we say that a live instruction forces
+        // liveness upon everything it mentions.
+        for (Arg& arg : inst.args) {
+            changed |= addLiveArg(arg);
+            arg.forEachTmpFast(
+                [&] (Tmp& tmp) {
+                    changed |= addLiveArg(tmp);
+                });
+        }
+    };
+
+    auto runForward = [&] () -> bool {
+        changed = false;
+        for (BasicBlock* block : code) {
+            for (Inst& inst : *block)
+                handleInst(inst);
+        }
+        return changed;
+    };
+
+    auto runBackward = [&] () -> bool {
+        changed = false;
+        for (unsigned blockIndex = code.size(); blockIndex--;) {
+            BasicBlock* block = code[blockIndex];
+            for (unsigned instIndex = block->size(); instIndex--;)
+                handleInst(block->at(instIndex));
+        }
+        return changed;
+    };
+
+    for (;;) {
+        // Propagating backward is most likely to be profitable.
+        if (!runBackward())
+            break;
+        if (!runBackward())
+            break;
+
+        // Occasionally propagating forward greatly reduces the likelihood of pathologies.
+        if (!runForward())
+            break;
+    }
+
+    unsigned removedInstCount = 0;
+    for (BasicBlock* block : code) {
+        removedInstCount += block->insts().removeAllMatching(
+            [&] (Inst& inst) -> bool {
+                return !isInstLive(inst);
+            });
+    }
+
+    return !!removedInstCount;
+}
+
+} } } // namespace JSC::B3::Air
+
+#endif // ENABLE(B3_JIT)
+