[runtime] Add %ToString and %_ToString and remove the TO_STRING builtin.

src/mips64/code-stubs-mips64.cc

Index: src/mips64/code-stubs-mips64.cc
diff --git a/src/mips64/code-stubs-mips64.cc b/src/mips64/code-stubs-mips64.cc
index bff8717d48dfdbf5ff35d814a98e5fafb8e765c4..49647a42069474f7b959f24c732cbe5198aad776 100644
--- a/src/mips64/code-stubs-mips64.cc
+++ b/src/mips64/code-stubs-mips64.cc
@@ -3449,6 +3449,38 @@ void ToNumberStub::Generate(MacroAssembler* masm) {
 }
 
 
+void ToStringStub::Generate(MacroAssembler* masm) {
+  // The ToString stub takes on argument in a0.
+  Label is_number;
+  __ JumpIfSmi(a0, &is_number);
+
+  Label not_string;
+  __ GetObjectType(a0, a1, a1);
+  // a0: receiver
+  // a1: receiver instance type
+  __ Branch(&not_string, ge, a1, Operand(FIRST_NONSTRING_TYPE));
+  __ Ret(USE_DELAY_SLOT);
+  __ mov(v0, a0);
+  __ bind(&not_string);
+
+  Label not_heap_number;
+  __ Branch(&not_heap_number, ne, a1, Operand(HEAP_NUMBER_TYPE));
+  __ bind(&is_number);
+  NumberToStringStub stub(isolate());
+  __ TailCallStub(&stub);
+  __ bind(&not_heap_number);
+
+  Label not_oddball;
+  __ Branch(&not_oddball, ne, a1, Operand(ODDBALL_TYPE));
+  __ Ret(USE_DELAY_SLOT);
+  __ ld(v0, FieldMemOperand(a0, Oddball::kToStringOffset));
+  __ bind(&not_oddball);
+
+  __ push(a0);  // Push argument.
+  __ TailCallRuntime(Runtime::kToString, 1, 1);
+}
+
+
 void StringHelper::GenerateFlatOneByteStringEquals(
     MacroAssembler* masm, Register left, Register right, Register scratch1,
     Register scratch2, Register scratch3) {