Add new HSeqStringGetChar instruction.

src/x64/lithium-codegen-x64.cc

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * 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
@@ skipping 1632 matching lines @@
     STATIC_ASSERT(kCharSize == 1);
     return FieldOperand(string, SeqString::kHeaderSize + offset);
   }
   return FieldOperand(
       string, ToRegister(index),
       encoding == String::ONE_BYTE_ENCODING ? times_1 : times_2,
       SeqString::kHeaderSize);
 }
 
 
+void LCodeGen::DoSeqStringGetChar(LSeqStringGetChar* instr) {
+  String::Encoding encoding = instr->hydrogen()->encoding();
+  Register result = ToRegister(instr->result());
+  Register string = ToRegister(instr->string());
+
+  if (FLAG_debug_code) {
+    __ push(string);
+    __ movq(string, FieldOperand(string, HeapObject::kMapOffset));
+    __ movzxbq(string, FieldOperand(string, Map::kInstanceTypeOffset));
+
+    __ andb(string, Immediate(kStringRepresentationMask | kStringEncodingMask));
+    static const uint32_t one_byte_seq_type = kSeqStringTag | kOneByteStringTag;
+    static const uint32_t two_byte_seq_type = kSeqStringTag | kTwoByteStringTag;
+    __ cmpq(string, Immediate(encoding == String::ONE_BYTE_ENCODING
+                              ? one_byte_seq_type : two_byte_seq_type));
+    __ Check(equal, kUnexpectedStringType);
+    __ pop(string);
+  }
+
+  Operand operand = BuildSeqStringOperand(string, instr->index(), encoding);
+  if (encoding == String::ONE_BYTE_ENCODING) {
+    __ movzxbl(result, operand);
+  } else {
+    __ movzxwl(result, operand);
+  }
+}
+
+
 void LCodeGen::DoSeqStringSetChar(LSeqStringSetChar* instr) {
   String::Encoding encoding = instr->hydrogen()->encoding();
   Register string = ToRegister(instr->string());
 
   if (FLAG_debug_code) {
     __ push(string);
     __ movq(string, FieldOperand(string, HeapObject::kMapOffset));
     __ movzxbq(string, FieldOperand(string, Map::kInstanceTypeOffset));
 
     __ andb(string, Immediate(kStringRepresentationMask | kStringEncodingMask));
@@ skipping 3835 matching lines @@
                                FixedArray::kHeaderSize - kPointerSize));
   __ bind(&done);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64