MIPS: Add initial hydrogenized NewStringAddStub.

Port r17635 (14180b1)

Original commit message:
The new stub is enabled via the --new-string-add flag, which is
disabled by default. For now, it's only a stripped down version
of the native StringAddStub, it's still work-in-progress.

BUG=v8:2990
R=plind44@gmail.com

Review URL: https://codereview.chromium.org/69953005

Patch from Balazs Kilvady <kilvadyb@homejinni.com>.

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@17664 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/mips/code-stubs-mips.cc

@@ -291,6 +291,17 @@ void ElementsTransitionAndStoreStub::InitializeInterfaceDescriptor(
 }
 
 
+void NewStringAddStub::InitializeInterfaceDescriptor(
+    Isolate* isolate,
+    CodeStubInterfaceDescriptor* descriptor) {
+  static Register registers[] = { a1, a0 };
+  descriptor->register_param_count_ = 2;
+  descriptor->register_params_ = registers;
+  descriptor->deoptimization_handler_ =
+      Runtime::FunctionForId(Runtime::kStringAdd)->entry;
+}
+
+
 #define __ ACCESS_MASM(masm)
 
 

src/mips/full-codegen-mips.cc

@@ -3740,11 +3740,20 @@ void FullCodeGenerator::EmitStringCharAt(CallRuntime* expr) {
 void FullCodeGenerator::EmitStringAdd(CallRuntime* expr) {
   ZoneList<Expression*>* args = expr->arguments();
   ASSERT_EQ(2, args->length());
+  if (FLAG_new_string_add) {
+    VisitForStackValue(args->at(0));
+    VisitForAccumulatorValue(args->at(1));
+
+    __ pop(a1);
+    NewStringAddStub stub(STRING_ADD_CHECK_BOTH, NOT_TENURED);
+    __ CallStub(&stub);
+  } else {
     VisitForStackValue(args->at(0));
     VisitForStackValue(args->at(1));
 
     StringAddStub stub(STRING_ADD_CHECK_BOTH);
     __ CallStub(&stub);
+  }
   context()->Plug(v0);
 }
 

src/mips/lithium-codegen-mips.cc

@@ -4480,10 +4480,18 @@ void LCodeGen::DoTrapAllocationMemento(LTrapAllocationMemento* instr) {
 
 void LCodeGen::DoStringAdd(LStringAdd* instr) {
   ASSERT(ToRegister(instr->context()).is(cp));
+  if (FLAG_new_string_add) {
+    ASSERT(ToRegister(instr->left()).is(a1));
+    ASSERT(ToRegister(instr->right()).is(a0));
+    NewStringAddStub stub(instr->hydrogen()->flags(),
+                          isolate()->heap()->GetPretenureMode());
+    CallCode(stub.GetCode(isolate()), RelocInfo::CODE_TARGET, instr);
+  } else {
     __ push(ToRegister(instr->left()));
     __ push(ToRegister(instr->right()));
     StringAddStub stub(instr->hydrogen()->flags());
     CallCode(stub.GetCode(isolate()), RelocInfo::CODE_TARGET, instr);
+  }
 }
 
 

src/mips/lithium-mips.cc

@@ -2335,8 +2335,12 @@ LInstruction* LChunkBuilder::DoStoreNamedGeneric(HStoreNamedGeneric* instr) {
 
 LInstruction* LChunkBuilder::DoStringAdd(HStringAdd* instr) {
   LOperand* context = UseFixed(instr->context(), cp);
-  LOperand* left = UseRegisterAtStart(instr->left());
-  LOperand* right = UseRegisterAtStart(instr->right());
+  LOperand* left = FLAG_new_string_add
+      ? UseFixed(instr->left(), a1)
+      : UseRegisterAtStart(instr->left());
+  LOperand* right = FLAG_new_string_add
+      ? UseFixed(instr->right(), a0)
+      : UseRegisterAtStart(instr->right());
   return MarkAsCall(
       DefineFixed(new(zone()) LStringAdd(context, left, right), v0),
       instr);