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diff --git a/Source/JavaScriptCore/b3/B3StackmapGenerationParams.h b/Source/JavaScriptCore/b3/B3StackmapGenerationParams.h
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+++ b/Source/JavaScriptCore/b3/B3StackmapGenerationParams.h
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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. 
+ */
+
+#pragma once
+
+#if ENABLE(B3_JIT)
+
+#include "AirGenerationContext.h"
+#include "B3ValueRep.h"
+#include "CCallHelpers.h"
+#include "RegisterSet.h"
+#include <wtf/Box.h>
+
+namespace JSC { namespace B3 {
+
+class CheckSpecial;
+class PatchpointSpecial;
+class Procedure;
+class StackmapValue;
+
+// NOTE: It's possible to capture StackmapGenerationParams by value, but not all of the methods will
+// work if you do that.
+class StackmapGenerationParams {
+public:
+    // This is the stackmap value that we're generating.
+    StackmapValue* value() const { return m_value; }
+    
+    // This tells you the actual value representations that were chosen. This is usually different
+    // from the constraints we supplied.
+    const Vector<ValueRep>& reps() const { return m_reps; };
+
+    // Usually we wish to access the reps. We make this easy by making ourselves appear to be a
+    // collection of reps.
+    unsigned size() const { return m_reps.size(); }
+    const ValueRep& at(unsigned index) const { return m_reps[index]; }
+    const ValueRep& operator[](unsigned index) const { return at(index); }
+    Vector<ValueRep>::const_iterator begin() const { return m_reps.begin(); }
+    Vector<ValueRep>::const_iterator end() const { return m_reps.end(); }
+    
+    // This tells you the registers that were used.
+    const RegisterSet& usedRegisters() const;
+
+    // This is a useful helper if you want to do register allocation inside of a patchpoint. The
+    // usedRegisters() set is not directly useful for this purpose because:
+    //
+    // - You can only use callee-save registers for scratch if they were saved in the prologue. So,
+    //   if a register is callee-save, it's not enough that it's not in usedRegisters().
+    //
+    // - Scratch registers are going to be in usedRegisters() at the patchpoint. So, if you want to
+    //   find one of your requested scratch registers using usedRegisters(), you'll have a bad time.
+    //
+    // This gives you the used register set that's useful for allocating scratch registers. This set
+    // is defined as:
+    //
+    //     (usedRegisters() | (RegisterSet::calleeSaveRegisters() - proc.calleeSaveRegisters()))
+    //     - gpScratchRegisters - fpScratchRegisters
+    //
+    // I.e. it is like usedRegisters() but also includes unsaved callee-saves and excludes scratch
+    // registers.
+    JS_EXPORT_PRIVATE RegisterSet unavailableRegisters() const;
+
+    GPRReg gpScratch(unsigned index) const { return m_gpScratch[index]; }
+    FPRReg fpScratch(unsigned index) const { return m_fpScratch[index]; }
+    
+    // This is computed lazily, so it won't work if you capture StackmapGenerationParams by value.
+    // These labels will get populated before any late paths or link tasks execute.
+    JS_EXPORT_PRIVATE Vector<Box<CCallHelpers::Label>> successorLabels() const;
+    
+    // This is computed lazily, so it won't work if you capture StackmapGenerationParams by value.
+    // Returns true if the successor at the given index is going to be emitted right after the
+    // patchpoint.
+    JS_EXPORT_PRIVATE bool fallsThroughToSuccessor(unsigned successorIndex) const;
+
+    // This is provided for convenience; it means that you don't have to capture it if you don't want to.
+    JS_EXPORT_PRIVATE Procedure& proc() const;
+    
+    // The Air::GenerationContext gives you even more power.
+    Air::GenerationContext& context() const { return m_context; };
+
+    template<typename Functor>
+    void addLatePath(const Functor& functor) const
+    {
+        context().latePaths.append(
+            createSharedTask<Air::GenerationContext::LatePathFunction>(
+                [=] (CCallHelpers& jit, Air::GenerationContext&) {
+                    functor(jit);
+                }));
+    }
+
+private:
+    friend class CheckSpecial;
+    friend class PatchpointSpecial;
+    
+    StackmapGenerationParams(StackmapValue*, const Vector<ValueRep>& reps, Air::GenerationContext&);
+
+    StackmapValue* m_value;
+    Vector<ValueRep> m_reps;
+    Vector<GPRReg> m_gpScratch;
+    Vector<FPRReg> m_fpScratch;
+    Air::GenerationContext& m_context;
+};
+
+} } // namespace JSC::B3
+
+#endif // ENABLE(B3_JIT)