Improve array to string conversion.

src/x64/codegen-x64.cc

 // Copyright 2012 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 588 matching lines @@
   // Load the byte into the result register.
   __ bind(&ascii);
   __ movzxbl(result, FieldOperand(string,
                                   index,
                                   times_1,
                                   SeqOneByteString::kHeaderSize));
   __ bind(&done);
 }
 
 
+void SeqStringSetCharGenerator::Generate(MacroAssembler* masm,
+                                         bool one_byte_string,
+                                         Register string,
+                                         Register index,
+                                         Register value) {
+  if (FLAG_debug_code) {
+    __ Check(masm->CheckSmi(index), "Non-smi index");
+    __ Check(masm->CheckSmi(value), "Non-smi value");
+
+    __ SmiCompare(index, FieldOperand(string, String::kLengthOffset));
+    __ Check(less, "Index is too large");
+
+    __ SmiCompare(index, Smi::FromInt(0));
+    __ Check(greater_equal, "Index is negative");
+
+    __ push(value);
+    __ movq(value, FieldOperand(string, HeapObject::kMapOffset));
+    __ movzxbq(value, FieldOperand(value, Map::kInstanceTypeOffset));
+
+    __ andb(value, Immediate(kStringRepresentationMask | kStringEncodingMask));
+    static const uint32_t one_byte_seq_type = kSeqStringTag | kOneByteStringTag;
+    static const uint32_t two_byte_seq_type = kSeqStringTag | kTwoByteStringTag;
+    __ cmpq(value, Immediate(one_byte_string ? one_byte_seq_type
+                                             : two_byte_seq_type));
+    __ Check(equal, "Unexpected string type");
+    __ pop(value);
+  }
+
+  __ SmiToInteger32(value, value);
+  __ SmiToInteger32(index, index);
+  if (one_byte_string) {
+    __ movb(FieldOperand(string, index, times_1, SeqString::kHeaderSize),
+            value);
+  } else {
+    __ movw(FieldOperand(string, index, times_2, SeqString::kHeaderSize),
+            value);
+  }
+}
+
+
 void MathExpGenerator::EmitMathExp(MacroAssembler* masm,
                                    XMMRegister input,
                                    XMMRegister result,
                                    XMMRegister double_scratch,
                                    Register temp1,
                                    Register temp2) {
   ASSERT(!input.is(result));
   ASSERT(!input.is(double_scratch));
   ASSERT(!result.is(double_scratch));
   ASSERT(!temp1.is(temp2));
@@ skipping 99 matching lines @@
     CodePatcher patcher(sequence, young_length);
     patcher.masm()->call(stub->instruction_start());
     patcher.masm()->nop();
   }
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64