[interpreter] Use hashmap for ConstantArrayBuilder's constant map

src/interpreter/constant-array-builder.h

 // Copyright 2015 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_INTERPRETER_CONSTANT_ARRAY_BUILDER_H_
 #define V8_INTERPRETER_CONSTANT_ARRAY_BUILDER_H_
 
 #include "src/identity-map.h"
+#include "src/inline-hash-map.h"
 #include "src/interpreter/bytecodes.h"
 #include "src/zone-containers.h"
 
 namespace v8 {
 namespace internal {
 
 class Isolate;
 
 namespace interpreter {
 
+// Hashing function specifically for addresses
+struct AddressHash {
+  size_t operator()(Address address) const {
+    // Divide by 8, then knuth multiplicative hash

[rmcilroy, 2016/09/12 14:17:31]

Should we divide 8 or by kPointerSize? 

+    return (bit_cast<size_t>(address) >> 3) * 2654435761;
+  }
+};
+
 // A helper class for constructing constant arrays for the
 // interpreter. Each instance of this class is intended to be used to
 // generate exactly one FixedArray of constants via the ToFixedArray
 // method.
 class ConstantArrayBuilder final BASE_EMBEDDED {
  public:
   // Capacity of the 8-bit operand slice.
   static const size_t k8BitCapacity = 1u << kBitsPerByte;
 
   // Capacity of the 16-bit operand slice.
@@ skipping 72 matching lines @@
 
     DISALLOW_COPY_AND_ASSIGN(ConstantArraySlice);
   };
 
   ConstantArraySlice* IndexToSlice(size_t index) const;
   ConstantArraySlice* OperandSizeToSlice(OperandSize operand_size) const;
 
   Handle<Object> the_hole_value() const { return the_hole_value_; }
 
   ConstantArraySlice* idx_slice_[3];
-  ZoneMap<Address, index_t> constants_map_;
+  ZoneInlineHashMap<Address, index_t, AddressHash> constants_map_;
   ZoneMap<Smi*, index_t> smi_map_;
   ZoneVector<std::pair<Smi*, index_t>> smi_pairs_;
   Handle<Object> the_hole_value_;
 };
 
 }  // namespace interpreter
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_INTERPRETER_CONSTANT_ARRAY_BUILDER_H_