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<dt>Revision</dt> <dd><a href="http://trac.webkit.org/projects/webkit/changeset/236018">236018</a></dd>
<dt>Author</dt> <dd>mark.lam@apple.com</dd>
<dt>Date</dt> <dd>2018-09-14 14:00:21 -0700 (Fri, 14 Sep 2018)</dd>
</dl>

<h3>Log Message</h3>
<pre>Refactor some ForInContext code for better encapsulation.
https://bugs.webkit.org/show_bug.cgi?id=189626
<rdar://problem/44466415>

Reviewed by Keith Miller.

1. Add a ForInContext::m_type field to store the context type.  This does not
   increase the class size, but eliminates the need for a virtual call to get the
   type.

   Note: we still need a virtual destructor because we'll be mingling
   IndexedForInContexts and StructureForInContexts in the BytecodeGenerator::m_forInContextStack.

2. Add ForInContext::isIndexedForInContext() and ForInContext::isStructureForInContext()
   convenience methods.

3. Add ForInContext::asIndexedForInContext() and ForInContext::asStructureForInContext()
   to do the casting to the subclass types.  This ensures that we'll properly
   assert that the casting is legal.

* bytecompiler/BytecodeGenerator.cpp:
(JSC::BytecodeGenerator::emitGetByVal):
(JSC::BytecodeGenerator::popIndexedForInScope):
(JSC::BytecodeGenerator::popStructureForInScope):
* bytecompiler/BytecodeGenerator.h:
(JSC::ForInContext::type const):
(JSC::ForInContext::isIndexedForInContext const):
(JSC::ForInContext::isStructureForInContext const):
(JSC::ForInContext::asIndexedForInContext):
(JSC::ForInContext::asStructureForInContext):
(JSC::ForInContext::ForInContext):
(JSC::StructureForInContext::StructureForInContext):
(JSC::IndexedForInContext::IndexedForInContext):
(JSC::ForInContext::~ForInContext): Deleted.</pre>

<h3>Modified Paths</h3>
<ul>
<li><a href="#trunkSourceJavaScriptCoreChangeLog">trunk/Source/JavaScriptCore/ChangeLog</a></li>
<li><a href="#trunkSourceJavaScriptCorebytecompilerBytecodeGeneratorcpp">trunk/Source/JavaScriptCore/bytecompiler/BytecodeGenerator.cpp</a></li>
<li><a href="#trunkSourceJavaScriptCorebytecompilerBytecodeGeneratorh">trunk/Source/JavaScriptCore/bytecompiler/BytecodeGenerator.h</a></li>
</ul>

</div>
<div id="patch">
<h3>Diff</h3>
<a id="trunkSourceJavaScriptCoreChangeLog"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/ChangeLog (236017 => 236018)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/ChangeLog    2018-09-14 20:36:45 UTC (rev 236017)
+++ trunk/Source/JavaScriptCore/ChangeLog       2018-09-14 21:00:21 UTC (rev 236018)
</span><span class="lines">@@ -1,3 +1,40 @@
</span><ins>+2018-09-14  Mark Lam  <mark.lam@apple.com>
+
+        Refactor some ForInContext code for better encapsulation.
+        https://bugs.webkit.org/show_bug.cgi?id=189626
+        <rdar://problem/44466415>
+
+        Reviewed by Keith Miller.
+
+        1. Add a ForInContext::m_type field to store the context type.  This does not
+           increase the class size, but eliminates the need for a virtual call to get the
+           type.
+
+           Note: we still need a virtual destructor because we'll be mingling
+           IndexedForInContexts and StructureForInContexts in the BytecodeGenerator::m_forInContextStack.
+
+        2. Add ForInContext::isIndexedForInContext() and ForInContext::isStructureForInContext()
+           convenience methods.
+
+        3. Add ForInContext::asIndexedForInContext() and ForInContext::asStructureForInContext()
+           to do the casting to the subclass types.  This ensures that we'll properly
+           assert that the casting is legal.
+
+        * bytecompiler/BytecodeGenerator.cpp:
+        (JSC::BytecodeGenerator::emitGetByVal):
+        (JSC::BytecodeGenerator::popIndexedForInScope):
+        (JSC::BytecodeGenerator::popStructureForInScope):
+        * bytecompiler/BytecodeGenerator.h:
+        (JSC::ForInContext::type const):
+        (JSC::ForInContext::isIndexedForInContext const):
+        (JSC::ForInContext::isStructureForInContext const):
+        (JSC::ForInContext::asIndexedForInContext):
+        (JSC::ForInContext::asStructureForInContext):
+        (JSC::ForInContext::ForInContext):
+        (JSC::StructureForInContext::StructureForInContext):
+        (JSC::IndexedForInContext::IndexedForInContext):
+        (JSC::ForInContext::~ForInContext): Deleted.
+
</ins><span class="cx"> 2018-09-14  Devin Rousso  <webkit@devinrousso.com>
</span><span class="cx"> 
</span><span class="cx">         Web Inspector: Record actions performed on ImageBitmapRenderingContext
</span></span></pre></div>
<a id="trunkSourceJavaScriptCorebytecompilerBytecodeGeneratorcpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/bytecompiler/BytecodeGenerator.cpp (236017 => 236018)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/bytecompiler/BytecodeGenerator.cpp   2018-09-14 20:36:45 UTC (rev 236017)
+++ trunk/Source/JavaScriptCore/bytecompiler/BytecodeGenerator.cpp      2018-09-14 21:00:21 UTC (rev 236018)
</span><span class="lines">@@ -2912,14 +2912,14 @@
</span><span class="cx"> 
</span><span class="cx">         unsigned instIndex = instructions().size();
</span><span class="cx"> 
</span><del>-        if (context.type() == ForInContext::IndexedForInContextType) {
-            static_cast<IndexedForInContext&>(context).addGetInst(instIndex, property->index());
-            property = static_cast<IndexedForInContext&>(context).index();
</del><ins>+        if (context.isIndexedForInContext()) {
+            auto& indexedContext = context.asIndexedForInContext();
+            indexedContext.addGetInst(instIndex, property->index());
+            property = indexedContext.index();
</ins><span class="cx">             break;
</span><span class="cx">         }
</span><span class="cx"> 
</span><del>-        ASSERT(context.type() == ForInContext::StructureForInContextType);
-        StructureForInContext& structureContext = static_cast<StructureForInContext&>(context);
</del><ins>+        StructureForInContext& structureContext = context.asStructureForInContext();
</ins><span class="cx">         UnlinkedValueProfile profile = emitProfiledOpcode(op_get_direct_pname);
</span><span class="cx">         instructions().append(kill(dst));
</span><span class="cx">         instructions().append(base->index());
</span><span class="lines">@@ -4631,9 +4631,7 @@
</span><span class="cx"> {
</span><span class="cx">     if (!localRegister)
</span><span class="cx">         return;
</span><del>-
-    ASSERT(m_forInContextStack.last()->type() == ForInContext::IndexedForInContextType);
-    static_cast<IndexedForInContext&>(m_forInContextStack.last().get()).finalize(*this);
</del><ins>+    m_forInContextStack.last()->asIndexedForInContext().finalize(*this);
</ins><span class="cx">     m_forInContextStack.removeLast();
</span><span class="cx"> }
</span><span class="cx"> 
</span><span class="lines">@@ -4743,8 +4741,7 @@
</span><span class="cx"> {
</span><span class="cx">     if (!localRegister)
</span><span class="cx">         return;
</span><del>-    ASSERT(m_forInContextStack.last()->type() == ForInContext::StructureForInContextType);
-    static_cast<StructureForInContext&>(m_forInContextStack.last().get()).finalize(*this);
</del><ins>+    m_forInContextStack.last()->asStructureForInContext().finalize(*this);
</ins><span class="cx">     m_forInContextStack.removeLast();
</span><span class="cx"> }
</span><span class="cx"> 
</span></span></pre></div>
<a id="trunkSourceJavaScriptCorebytecompilerBytecodeGeneratorh"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/bytecompiler/BytecodeGenerator.h (236017 => 236018)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/bytecompiler/BytecodeGenerator.h     2018-09-14 20:36:45 UTC (rev 236017)
+++ trunk/Source/JavaScriptCore/bytecompiler/BytecodeGenerator.h        2018-09-14 21:00:21 UTC (rev 236018)
</span><span class="lines">@@ -56,6 +56,8 @@
</span><span class="cx"> 
</span><span class="cx">     class JSImmutableButterfly;
</span><span class="cx">     class Identifier;
</span><ins>+    class IndexedForInContext;
+    class StructureForInContext;
</ins><span class="cx"> 
</span><span class="cx">     enum ExpectedFunction {
</span><span class="cx">         NoExpectedFunction,
</span><span class="lines">@@ -180,30 +182,44 @@
</span><span class="cx">         WTF_MAKE_FAST_ALLOCATED;
</span><span class="cx">         WTF_MAKE_NONCOPYABLE(ForInContext);
</span><span class="cx">     public:
</span><del>-        ForInContext(RegisterID* localRegister)
-            : m_localRegister(localRegister)
-            , m_isValid(true)
</del><ins>+        virtual ~ForInContext() = default;
+
+        bool isValid() const { return m_isValid; }
+        void invalidate() { m_isValid = false; }
+
+        enum class Type : uint8_t {
+            IndexedForIn,
+            StructureForIn
+        };
+
+        Type type() const { return m_type; }
+        bool isIndexedForInContext() const { return m_type == Type::IndexedForIn; }
+        bool isStructureForInContext() const { return m_type == Type::StructureForIn; }
+
+        IndexedForInContext& asIndexedForInContext()
</ins><span class="cx">         {
</span><ins>+            ASSERT(isIndexedForInContext());
+            return *reinterpret_cast<IndexedForInContext*>(this);
</ins><span class="cx">         }
</span><span class="cx"> 
</span><del>-        virtual ~ForInContext()
</del><ins>+        StructureForInContext& asStructureForInContext()
</ins><span class="cx">         {
</span><ins>+            ASSERT(isStructureForInContext());
+            return *reinterpret_cast<StructureForInContext*>(this);
</ins><span class="cx">         }
</span><span class="cx"> 
</span><del>-        bool isValid() const { return m_isValid; }
-        void invalidate() { m_isValid = false; }
</del><ins>+        RegisterID* local() const { return m_localRegister.get(); }
</ins><span class="cx"> 
</span><del>-        enum ForInContextType {
-            StructureForInContextType,
-            IndexedForInContextType
-        };
-        virtual ForInContextType type() const = 0;
</del><ins>+    protected:
+        ForInContext(RegisterID* localRegister, Type type)
+            : m_localRegister(localRegister)
+            , m_type(type)
+        { }
</ins><span class="cx"> 
</span><del>-        RegisterID* local() const { return m_localRegister.get(); }
-
</del><span class="cx">     private:
</span><span class="cx">         RefPtr<RegisterID> m_localRegister;
</span><del>-        bool m_isValid;
</del><ins>+        bool m_isValid { true };
+        Type m_type;
</ins><span class="cx">     };
</span><span class="cx"> 
</span><span class="cx">     class StructureForInContext : public ForInContext {
</span><span class="lines">@@ -211,7 +227,7 @@
</span><span class="cx">         using GetInst = std::tuple<unsigned, int, UnlinkedValueProfile>;
</span><span class="cx"> 
</span><span class="cx">         StructureForInContext(RegisterID* localRegister, RegisterID* indexRegister, RegisterID* propertyRegister, RegisterID* enumeratorRegister)
</span><del>-            : ForInContext(localRegister)
</del><ins>+            : ForInContext(localRegister, Type::StructureForIn)
</ins><span class="cx">             , m_indexRegister(indexRegister)
</span><span class="cx">             , m_propertyRegister(propertyRegister)
</span><span class="cx">             , m_enumeratorRegister(enumeratorRegister)
</span><span class="lines">@@ -218,11 +234,6 @@
</span><span class="cx">         {
</span><span class="cx">         }
</span><span class="cx"> 
</span><del>-        ForInContextType type() const override
-        {
-            return StructureForInContextType;
-        }
-
</del><span class="cx">         RegisterID* index() const { return m_indexRegister.get(); }
</span><span class="cx">         RegisterID* property() const { return m_propertyRegister.get(); }
</span><span class="cx">         RegisterID* enumerator() const { return m_enumeratorRegister.get(); }
</span><span class="lines">@@ -244,16 +255,11 @@
</span><span class="cx">     class IndexedForInContext : public ForInContext {
</span><span class="cx">     public:
</span><span class="cx">         IndexedForInContext(RegisterID* localRegister, RegisterID* indexRegister)
</span><del>-            : ForInContext(localRegister)
</del><ins>+            : ForInContext(localRegister, Type::IndexedForIn)
</ins><span class="cx">             , m_indexRegister(indexRegister)
</span><span class="cx">         {
</span><span class="cx">         }
</span><span class="cx"> 
</span><del>-        ForInContextType type() const override
-        {
-            return IndexedForInContextType;
-        }
-
</del><span class="cx">         RegisterID* index() const { return m_indexRegister.get(); }
</span><span class="cx"> 
</span><span class="cx">         void finalize(BytecodeGenerator&);
</span></span></pre>
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