MIPS: new classes: special construct stub for derived classs and TDZ for `this`.

src/mips64/full-codegen-mips64.cc

Index: src/mips64/full-codegen-mips64.cc
diff --git a/src/mips64/full-codegen-mips64.cc b/src/mips64/full-codegen-mips64.cc
index eccd1f9238e06b444e387c423032d51525193106..3c6dc54e8ab6b3f14c5aa8ccc6f645ce82b5fa87 100644
--- a/src/mips64/full-codegen-mips64.cc
+++ b/src/mips64/full-codegen-mips64.cc
@@ -1518,6 +1518,10 @@ void FullCodeGenerator::EmitVariableLoad(VariableProxy* proxy) {
         bool skip_init_check;
         if (var->scope()->DeclarationScope() != scope()->DeclarationScope()) {
           skip_init_check = false;
+        } else if (var->is_this()) {
+          CHECK((info_->shared_info()->kind() & kSubclassConstructor) != 0);
+          // TODO(dslomov): implement 'this' hole check elimination.
+          skip_init_check = false;
         } else {
           // Check that we always have valid source position.
           DCHECK(var->initializer_position() != RelocInfo::kNoPosition);
@@ -3220,6 +3224,17 @@ void FullCodeGenerator::EmitSuperConstructorCall(Call* expr) {
   EmitLoadSuperConstructor(super_ref);
   __ push(result_register());
 
+  Variable* this_var = super_ref->this_var()->var();
+
+  GetVar(a0, this_var);
+  __ LoadRoot(at, Heap::kTheHoleValueRootIndex);
+  Label uninitialized_this;
+  __ Branch(&uninitialized_this, eq, a0, Operand(at));
+  __ li(a0, Operand(this_var->name()));
+  __ Push(a0);
+  __ CallRuntime(Runtime::kThrowReferenceError, 1);
+  __ bind(&uninitialized_this);
+
   // Push the arguments ("left-to-right") on the stack.
   ZoneList<Expression*>* args = expr->arguments();
   int arg_count = args->length();
@@ -3254,8 +3269,7 @@ void FullCodeGenerator::EmitSuperConstructorCall(Call* expr) {
 
   RecordJSReturnSite(expr);
 
-  // TODO(dslomov): implement TDZ for `this`.
-  EmitVariableAssignment(super_ref->this_var()->var(), Token::ASSIGN);
+  EmitVariableAssignment(this_var, Token::INIT_CONST);
   context()->Plug(v0);
 }