X64: Implement StringCharAtStub which is used from lithium codegen....

src/x64/code-stubs-x64.cc

 // Copyright 2011 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 4815 matching lines @@
   __ addq(rsp, Immediate(2 * kPointerSize));
   __ push(rcx);
   GenerateCompareFlatAsciiStrings(masm, rdx, rax, rcx, rbx, rdi, r8);
 
   // Call the runtime; it returns -1 (less), 0 (equal), or 1 (greater)
   // tagged as a small integer.
   __ bind(&runtime);
   __ TailCallRuntime(Runtime::kStringCompare, 2, 1);
 }
 
+
+void StringCharAtStub::Generate(MacroAssembler* masm) {
+  // Expects two arguments (object, index) on the stack:
+
+  // Stack frame on entry.
+  //  rsp[0]: return address
+  //  rsp[8]: index
+  //  rsp[16]: object
+
+  Register object = rbx;
+  Register index = rax;
+  Register scratch1 = rcx;
+  Register scratch2 = rdx;
+  Register result = rax;
+
+  __ pop(scratch1);  // Return address.
+  __ pop(index);
+  __ pop(object);
+  __ push(scratch1);
+
+  Label need_conversion;
+  Label index_out_of_range;
+  Label done;
+  StringCharAtGenerator generator(object,
+                                  index,
+                                  scratch1,
+                                  scratch2,
+                                  result,
+                                  &need_conversion,
+                                  &need_conversion,
+                                  &index_out_of_range,
+                                  STRING_INDEX_IS_NUMBER);
+  generator.GenerateFast(masm);
+  __ jmp(&done);
+
+  __ bind(&index_out_of_range);
+  // When the index is out of range, the spec requires us to return
+  // the empty string.
+  __ Move(result, Factory::empty_string());
+  __ jmp(&done);
+
+  __ bind(&need_conversion);
+  // Move smi zero into the result register, which will trigger
+  // conversion.
+  __ Move(result, Smi::FromInt(0));
+  __ jmp(&done);
+
+  StubRuntimeCallHelper call_helper;
+  generator.GenerateSlow(masm, call_helper);
+
+  __ bind(&done);
+  __ ret(0);
+}
+
+
 void ICCompareStub::GenerateSmis(MacroAssembler* masm) {
   ASSERT(state_ == CompareIC::SMIS);
   NearLabel miss;
   __ JumpIfNotBothSmi(rdx, rax, &miss);
 
   if (GetCondition() == equal) {
     // For equality we do not care about the sign of the result.
     __ subq(rax, rdx);
   } else {
     NearLabel done;
@@ skipping 240 matching lines @@
           FieldOperand(elements, PixelArray::kExternalPointerOffset));
   __ movb(Operand(external_pointer, untagged_key, times_1, 0), untagged_value);
   __ ret(0);  // Return value in eax.
 }
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64