[stubs] Add a utility class to generate code to access builtin arguments

src/code-stub-assembler.h

 // Copyright 2016 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_CODE_STUB_ASSEMBLER_H_
 #define V8_CODE_STUB_ASSEMBLER_H_
 
 #include <functional>
 
 #include "src/compiler/code-assembler.h"
@@ skipping 1090 matching lines @@
 
   compiler::Node* Typeof(compiler::Node* value, compiler::Node* context);
 
   compiler::Node* InstanceOf(compiler::Node* object, compiler::Node* callable,
                              compiler::Node* context);
 
   // TypedArray/ArrayBuffer helpers
   compiler::Node* IsDetachedBuffer(compiler::Node* buffer);
 
  private:
+  friend class CodeStubArguments;
+
   enum ElementSupport { kOnlyProperties, kSupportElements };
 
   void DescriptorLookupLinear(compiler::Node* unique_name,
                               compiler::Node* descriptors, compiler::Node* nof,
                               Label* if_found, Variable* var_name_index,
                               Label* if_not_found);
   compiler::Node* CallGetterIfAccessor(compiler::Node* value,
                                        compiler::Node* details,
                                        compiler::Node* context,
                                        compiler::Node* receiver,
@@ skipping 80 matching lines @@
 
   compiler::Node* AllocateConsString(Heap::RootListIndex map_root_index,
                                      compiler::Node* length,
                                      compiler::Node* first,
                                      compiler::Node* second,
                                      AllocationFlags flags);
 
   static const int kElementLoopUnrollThreshold = 8;
 };
 
+class CodeStubArguments {
+ public:
+  // |argc| specifies the number of arguments passed to the builtin excluding
+  // the receiver.
+  CodeStubArguments(CodeStubAssembler* assembler, compiler::Node* argc,
+                    CodeStubAssembler::ParameterMode mode =
+                        CodeStubAssembler::INTPTR_PARAMETERS);
+
+  compiler::Node* GetReceiver();
+
+  // |index| is zero-based and does not include the receiver
+  compiler::Node* AtIndex(compiler::Node* index,
+                          CodeStubAssembler::ParameterMode mode =
+                              CodeStubAssembler::INTPTR_PARAMETERS);
+
+  compiler::Node* AtIndex(int index);
+
+  typedef std::function<void(CodeStubAssembler* assembler, compiler::Node* arg)>
+      ForEachBodyFunction;
+
+  // Iteration doesn't include the receiver. |first| and |last| are zero-based.
+  void ForEach(ForEachBodyFunction body, compiler::Node* first = nullptr,
+               compiler::Node* last = nullptr,
+               CodeStubAssembler::ParameterMode mode =
+                   CodeStubAssembler::INTPTR_PARAMETERS) {
+    CodeStubAssembler::VariableList list(0, assembler_->zone());
+    ForEach(list, body, first, last);
+  }
+
+  // Iteration doesn't include the receiver. |first| and |last| are zero-based.
+  void ForEach(const CodeStubAssembler::VariableList& vars,
+               ForEachBodyFunction body, compiler::Node* first = nullptr,
+               compiler::Node* last = nullptr,
+               CodeStubAssembler::ParameterMode mode =
+                   CodeStubAssembler::INTPTR_PARAMETERS);
+
+  void PopAndReturn(compiler::Node* value);
+
+ private:
+  compiler::Node* GetArguments();
+
+  CodeStubAssembler* assembler_;
+  compiler::Node* argc_;
+  compiler::Node* arguments_;
+  compiler::Node* fp_;
+};
+
 #define CSA_ASSERT(x) Assert((x), #x, __FILE__, __LINE__)
 #ifdef ENABLE_SLOW_DCHECKS
 #define CSA_SLOW_ASSERT(x)               \
   if (FLAG_enable_slow_asserts) {        \
     Assert((x), #x, __FILE__, __LINE__); \
   }
 #else
 #define CSA_SLOW_ASSERT(x)
 #endif
 
 DEFINE_OPERATORS_FOR_FLAGS(CodeStubAssembler::AllocationFlags);
 
 }  // namespace internal
 }  // namespace v8
 #endif  // V8_CODE_STUB_ASSEMBLER_H_