[Interpreter] Add support for loading literals from the constant pool.

src/compiler/interpreter-assembler.h

Index: src/compiler/interpreter-assembler.h
diff --git a/src/compiler/interpreter-assembler.h b/src/compiler/interpreter-assembler.h
index 3dc0c96ee61eacd43921245558854a8d75dc589f..0f8996d7006c844d0fa38546d3f1f14d0f37e821 100644
--- a/src/compiler/interpreter-assembler.h
+++ b/src/compiler/interpreter-assembler.h
@@ -37,6 +37,9 @@ class InterpreterAssembler {
 
   Handle<Code> GenerateCode();
 
+  // Returns the Idx immediate for bytecode operand |operand_index| in the
+  // current bytecode.
+  Node* BytecodeOperandIdx(int operand_index);
   // Returns the Imm8 immediate for bytecode operand |operand_index| in the
   // current bytecode.
   Node* BytecodeOperandImm8(int operand_index);
@@ -62,6 +65,9 @@ class InterpreterAssembler {
   Node* SmiTag(Node* value);
   Node* SmiUntag(Node* value);
 
+  // Load constant at |index| in the constant pool.
+  Node* LoadConstantPoolEntry(Node* index);
+
   // Load a field from an object on the heap.
   Node* LoadObjectField(Node* object, int offset);