X87: [builtins] Unify the String constructor.

src/x87/builtins-x87.cc

Index: src/x87/builtins-x87.cc
diff --git a/src/x87/builtins-x87.cc b/src/x87/builtins-x87.cc
index be973c8995de16f1b21739892010ff8878781925..1294eed15def87667e563e9156fe8aa6f15f4d7e 100644
--- a/src/x87/builtins-x87.cc
+++ b/src/x87/builtins-x87.cc
@@ -1251,7 +1251,68 @@ void Builtins::Generate_ArrayCode(MacroAssembler* masm) {
 }
 
 
-void Builtins::Generate_StringConstructCode(MacroAssembler* masm) {
+// static
+void Builtins::Generate_StringConstructor(MacroAssembler* masm) {
+  // ----------- S t a t e -------------
+  //  -- eax                 : number of arguments
+  //  -- edi                 : constructor function
+  //  -- esp[0]              : return address
+  //  -- esp[(argc - n) * 4] : arg[n] (zero-based)
+  //  -- esp[(argc + 1) * 4] : receiver
+  // -----------------------------------
+
+  // 1. Load the first argument into eax and get rid of the rest (including the
+  // receiver).
+  Label no_arguments;
+  {
+    __ test(eax, eax);
+    __ j(zero, &no_arguments, Label::kNear);
+    __ mov(ebx, Operand(esp, eax, times_pointer_size, 0));
+    __ PopReturnAddressTo(ecx);
+    __ lea(esp, Operand(esp, eax, times_pointer_size, kPointerSize));
+    __ PushReturnAddressFrom(ecx);
+    __ mov(eax, ebx);
+  }
+
+  // 2a. At least one argument, return eax if it's a string, otherwise
+  // dispatch to appropriate conversion.
+  Label to_string, symbol_descriptive_string;
+  {
+    __ JumpIfSmi(eax, &to_string, Label::kNear);
+    STATIC_ASSERT(FIRST_NONSTRING_TYPE == SYMBOL_TYPE);
+    __ CmpObjectType(eax, FIRST_NONSTRING_TYPE, edx);
+    __ j(above, &to_string, Label::kNear);
+    __ j(equal, &symbol_descriptive_string, Label::kNear);
+    __ Ret();
+  }
+
+  // 2b. No arguments, return the empty string (and pop the receiver).
+  __ bind(&no_arguments);
+  {
+    __ LoadRoot(eax, Heap::kempty_stringRootIndex);
+    __ ret(1 * kPointerSize);
+  }
+
+  // 3a. Convert eax to a string.
+  __ bind(&to_string);
+  {
+    ToStringStub stub(masm->isolate());
+    __ TailCallStub(&stub);
+  }
+
+  // 3b. Convert symbol in eax to a string.
+  __ bind(&symbol_descriptive_string);
+  {
+    __ PopReturnAddressTo(ecx);
+    __ Push(eax);
+    __ PushReturnAddressFrom(ecx);
+    __ TailCallRuntime(Runtime::kSymbolDescriptiveString, 1, 1);
+  }
+}
+
+
+// static
+void Builtins::Generate_StringConstructor_ConstructStub(MacroAssembler* masm) {
   // ----------- S t a t e -------------
   //  -- eax                 : number of arguments
   //  -- edi                 : constructor function