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diff --git a/Source/JavaScriptCore/b3/B3StackmapValue.h b/Source/JavaScriptCore/b3/B3StackmapValue.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 "B3ConstrainedValue.h"
+#include "B3Value.h"
+#include "B3ValueRep.h"
+#include "CCallHelpers.h"
+#include "RegisterSet.h"
+#include <wtf/SharedTask.h>
+
+namespace JSC { namespace B3 {
+
+class StackmapGenerationParams;
+
+typedef void StackmapGeneratorFunction(CCallHelpers&, const StackmapGenerationParams&);
+typedef SharedTask<StackmapGeneratorFunction> StackmapGenerator;
+
+class JS_EXPORT_PRIVATE StackmapValue : public Value {
+public:
+    static bool accepts(Kind kind)
+    {
+        // This needs to include opcodes of all subclasses.
+        switch (kind.opcode()) {
+        case CheckAdd:
+        case CheckSub:
+        case CheckMul:
+        case Check:
+        case Patchpoint:
+            return true;
+        default:
+            return false;
+        }
+    }
+
+    ~StackmapValue();
+
+    // Use this to add children. Note that you could also add children by doing
+    // children().append(). That will work fine, but it's not recommended.
+    void append(const ConstrainedValue& value)
+    {
+        append(value.value(), value.rep());
+    }
+
+    void append(Value*, const ValueRep&);
+
+    template<typename VectorType>
+    void appendVector(const VectorType& vector)
+    {
+        for (const auto& value : vector)
+            append(value);
+    }
+
+    // Helper for appending a bunch of values with some ValueRep.
+    template<typename VectorType>
+    void appendVectorWithRep(const VectorType& vector, const ValueRep& rep)
+    {
+        for (Value* value : vector)
+            append(value, rep);
+    }
+
+    // Helper for appending cold any's. This often used by clients to implement OSR.
+    template<typename VectorType>
+    void appendColdAnys(const VectorType& vector)
+    {
+        appendVectorWithRep(vector, ValueRep::ColdAny);
+    }
+    template<typename VectorType>
+    void appendLateColdAnys(const VectorType& vector)
+    {
+        appendVectorWithRep(vector, ValueRep::LateColdAny);
+    }
+
+    // This is a helper for something you might do a lot of: append a value that should be constrained
+    // to SomeRegister.
+    void appendSomeRegister(Value*);
+
+    const Vector<ValueRep>& reps() const { return m_reps; }
+
+    // Stackmaps allow you to specify that the operation may clobber some registers. Clobbering a register
+    // means that the operation appears to store a value into the register, but the compiler doesn't
+    // assume to know anything about what kind of value might have been stored. In B3's model of
+    // execution, registers are read or written at instruction boundaries rather than inside the
+    // instructions themselves. A register could be read or written immediately before the instruction
+    // executes, or immediately after. Note that at a boundary between instruction A and instruction B we
+    // simultaneously look at what A does after it executes and what B does before it executes. This is
+    // because when the compiler considers what happens to registers, it views the boundary between two
+    // instructions as a kind of atomic point where the late effects of A happen at the same time as the
+    // early effects of B.
+    //
+    // The compiler views a stackmap as a single instruction, even though of course the stackmap may be
+    // composed of any number of instructions (if it's a Patchpoint). You can claim that a stackmap value
+    // clobbers a set of registers before the stackmap's instruction or after. Clobbering before is called
+    // early clobber, while clobbering after is called late clobber.
+    //
+    // This is quite flexible but it has its limitations. Any register listed as an early clobber will
+    // interfere with all uses of the stackmap. Any register listed as a late clobber will interfere with
+    // all defs of the stackmap (i.e. the result). This means that it's currently not possible to claim
+    // to clobber a register while still allowing that register to be used for both an input and an output
+    // of the instruction. It just so happens that B3's sole client (the FTL) currently never wants to
+    // convey such a constraint, but it will want it eventually (FIXME:
+    // https://bugs.webkit.org/show_bug.cgi?id=151823).
+    //
+    // Note that a common use case of early clobber sets is to indicate that this is the set of registers
+    // that shall not be used for inputs to the value. But B3 supports two different ways of specifying
+    // this, the other being LateUse in combination with late clobber (not yet available to stackmaps
+    // directly, FIXME: https://bugs.webkit.org/show_bug.cgi?id=151335). A late use makes the use of that
+    // value appear to happen after the instruction. This means that a late use cannot use the same
+    // register as the result and it cannot use the same register as either early or late clobbered
+    // registers. Late uses are usually a better way of saying that a clobbered register cannot be used
+    // for an input. Early clobber means that some register(s) interfere with *all* inputs, while LateUse
+    // means that some value interferes with whatever is live after the instruction. Below is a list of
+    // examples of how the FTL can handle its various kinds of scenarios using a combination of early
+    // clobber, late clobber, and late use. These examples are for X86_64, w.l.o.g.
+    //
+    // Basic ById patchpoint: Early and late clobber of r11. Early clobber prevents any inputs from using
+    // r11 since that would mess with the MacroAssembler's assumptions when we
+    // AllowMacroScratchRegisterUsage. Late clobber tells B3 that the patchpoint may overwrite r11.
+    //
+    // ById patchpoint in a try block with some live state: This might throw an exception after already
+    // assigning to the result. So, this should LateUse all stackmap values to ensure that the stackmap
+    // values don't interfere with the result. Note that we do not LateUse the non-OSR inputs of the ById
+    // since LateUse implies that the use is cold: the register allocator will assume that the use is not
+    // important for the critical path. Also, early and late clobber of r11.
+    //
+    // Basic ByIdFlush patchpoint: We could do Flush the same way we did it with LLVM: ignore it and let
+    // PolymorphicAccess figure it out. Or, we could add internal clobber support (FIXME:
+    // https://bugs.webkit.org/show_bug.cgi?id=151823). Or, we could do it by early clobbering r11, late
+    // clobbering all volatile registers, and constraining the result to some register. Or, we could do
+    // that but leave the result constrained to SomeRegister, which will cause it to use a callee-save
+    // register. Internal clobber support would allow us to use SomeRegister while getting the result into
+    // a volatile register.
+    //
+    // ByIdFlush patchpoint in a try block with some live state: LateUse all for-OSR stackmap values,
+    // early clobber of r11 to prevent the other inputs from using r11, and late clobber of all volatile
+    // registers to make way for the call. To handle the result, we could do any of what is listed in the
+    // previous paragraph.
+    //
+    // Basic JS call: Force all non-OSR inputs into specific locations (register, stack, whatever).
+    // All volatile registers are late-clobbered. The output is constrained to a register as well.
+    //
+    // JS call in a try block with some live state: LateUse all for-OSR stackmap values, fully constrain
+    // all non-OSR inputs and the result, and late clobber all volatile registers.
+    //
+    // JS tail call: Pass all inputs as a warm variant of Any (FIXME:
+    // https://bugs.webkit.org/show_bug.cgi?id=151811).
+    //
+    // Note that we cannot yet do all of these things because although Air already supports all of these
+    // various forms of uses (LateUse and warm unconstrained use), B3 doesn't yet expose all of it. The
+    // bugs are:
+    // https://bugs.webkit.org/show_bug.cgi?id=151335 (LateUse)
+    // https://bugs.webkit.org/show_bug.cgi?id=151811 (warm Any)
+    void clobberEarly(const RegisterSet& set)
+    {
+        m_earlyClobbered.merge(set);
+    }
+
+    void clobberLate(const RegisterSet& set)
+    {
+        m_lateClobbered.merge(set);
+    }
+
+    void clobber(const RegisterSet& set)
+    {
+        clobberEarly(set);
+        clobberLate(set);
+    }
+
+    RegisterSet& earlyClobbered() { return m_earlyClobbered; }
+    RegisterSet& lateClobbered() { return m_lateClobbered; }
+    const RegisterSet& earlyClobbered() const { return m_earlyClobbered; }
+    const RegisterSet& lateClobbered() const { return m_lateClobbered; }
+
+    void setGenerator(RefPtr<StackmapGenerator> generator)
+    {
+        m_generator = generator;
+    }
+
+    template<typename Functor>
+    void setGenerator(const Functor& functor)
+    {
+        m_generator = createSharedTask<StackmapGeneratorFunction>(functor);
+    }
+
+    RefPtr<StackmapGenerator> generator() const { return m_generator; }
+
+    ConstrainedValue constrainedChild(unsigned index) const
+    {
+        return ConstrainedValue(child(index), index < m_reps.size() ? m_reps[index] : ValueRep::ColdAny);
+    }
+
+    void setConstrainedChild(unsigned index, const ConstrainedValue&);
+    
+    void setConstraint(unsigned index, const ValueRep&);
+
+    class ConstrainedValueCollection {
+    public:
+        ConstrainedValueCollection(const StackmapValue& value)
+            : m_value(value)
+        {
+        }
+
+        unsigned size() const { return m_value.numChildren(); }
+        
+        ConstrainedValue at(unsigned index) const { return m_value.constrainedChild(index); }
+
+        ConstrainedValue operator[](unsigned index) const { return at(index); }
+
+        class iterator {
+        public:
+            iterator()
+                : m_collection(nullptr)
+                , m_index(0)
+            {
+            }
+
+            iterator(const ConstrainedValueCollection& collection, unsigned index)
+                : m_collection(&collection)
+                , m_index(index)
+            {
+            }
+
+            ConstrainedValue operator*() const
+            {
+                return m_collection->at(m_index);
+            }
+
+            iterator& operator++()
+            {
+                m_index++;
+                return *this;
+            }
+
+            bool operator==(const iterator& other) const
+            {
+                ASSERT(m_collection == other.m_collection);
+                return m_index == other.m_index;
+            }
+
+            bool operator!=(const iterator& other) const
+            {
+                return !(*this == other);
+            }
+            
+        private:
+            const ConstrainedValueCollection* m_collection;
+            unsigned m_index;
+        };
+
+        iterator begin() const { return iterator(*this, 0); }
+        iterator end() const { return iterator(*this, size()); }
+
+    private:
+        const StackmapValue& m_value;
+    };
+
+    ConstrainedValueCollection constrainedChildren() const
+    {
+        return ConstrainedValueCollection(*this);
+    }
+
+protected:
+    void dumpChildren(CommaPrinter&, PrintStream&) const override;
+    void dumpMeta(CommaPrinter&, PrintStream&) const override;
+
+    StackmapValue(CheckedOpcodeTag, Kind, Type, Origin);
+
+private:
+    friend class CheckSpecial;
+    friend class PatchpointSpecial;
+    friend class StackmapGenerationParams;
+    friend class StackmapSpecial;
+    
+    Vector<ValueRep> m_reps;
+    RefPtr<StackmapGenerator> m_generator;
+    RegisterSet m_earlyClobbered;
+    RegisterSet m_lateClobbered;
+    RegisterSet m_usedRegisters; // Stackmaps could be further duplicated by Air, but that's unlikely, so we just merge the used registers sets if that were to happen.
+};
+
+} } // namespace JSC::B3
+
+#endif // ENABLE(B3_JIT)