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diff --git a/Source/JavaScriptCore/b3/air/AirReportUsedRegisters.cpp b/Source/JavaScriptCore/b3/air/AirReportUsedRegisters.cpp
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+++ b/Source/JavaScriptCore/b3/air/AirReportUsedRegisters.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 "AirReportUsedRegisters.h"
+
+#if ENABLE(B3_JIT)
+
+#include "AirArgInlines.h"
+#include "AirCode.h"
+#include "AirInstInlines.h"
+#include "AirLiveness.h"
+#include "AirPhaseScope.h"
+
+namespace JSC { namespace B3 { namespace Air {
+
+void reportUsedRegisters(Code& code)
+{
+    PhaseScope phaseScope(code, "reportUsedRegisters");
+
+    RegLiveness liveness(code);
+
+    for (BasicBlock* block : code) {
+        RegLiveness::LocalCalc localCalc(liveness, block);
+
+        for (unsigned instIndex = block->size(); instIndex--;) {
+            Inst& inst = block->at(instIndex);
+
+            // Kill dead assignments to registers. For simplicity we say that a store is killable if
+            // it has only late defs and those late defs are to registers that are dead right now.
+            if (!inst.hasNonArgEffects()) {
+                bool canDelete = true;
+                inst.forEachArg(
+                    [&] (Arg& arg, Arg::Role role, Arg::Type, Arg::Width) {
+                        if (Arg::isEarlyDef(role)) {
+                            canDelete = false;
+                            return;
+                        }
+                        if (!Arg::isLateDef(role))
+                            return;
+                        if (!arg.isReg()) {
+                            canDelete = false;
+                            return;
+                        }
+                        if (localCalc.isLive(arg.reg())) {
+                            canDelete = false;
+                            return;
+                        }
+                    });
+                if (canDelete)
+                    inst = Inst();
+            }
+            
+            if (inst.kind.opcode == Patch) {
+                RegisterSet registerSet;
+                for (Reg reg : localCalc.live())
+                    registerSet.set(reg);
+                inst.reportUsedRegisters(registerSet);
+            }
+            localCalc.execute(instIndex);
+        }
+        
+        block->insts().removeAllMatching(
+            [&] (const Inst& inst) -> bool {
+                return !inst;
+            });
+    }
+}
+
+} } } // namespace JSC::B3::Air
+
+#endif // ENABLE(B3_JIT)
+
+