MIPS: port Block scoped const variables.

src/mips/full-codegen-mips.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 260 matching lines @@
     Comment cmnt(masm_, "[ Declarations");
     scope()->VisitIllegalRedeclaration(this);
 
   } else {
     PrepareForBailoutForId(AstNode::kFunctionEntryId, NO_REGISTERS);
     { Comment cmnt(masm_, "[ Declarations");
       // For named function expressions, declare the function name as a
       // constant.
       if (scope()->is_function_scope() && scope()->function() != NULL) {
         int ignored = 0;
-        EmitDeclaration(scope()->function(), CONST, NULL, &ignored);
+        VariableProxy* proxy = scope()->function();
+        ASSERT(proxy->var()->mode() == CONST ||
+               proxy->var()->mode() == CONST_HARMONY);
+        EmitDeclaration(proxy, proxy->var()->mode(), NULL, &ignored);
       }
       VisitDeclarations(scope()->declarations());
     }
 
     { Comment cmnt(masm_, "[ Stack check");
       PrepareForBailoutForId(AstNode::kDeclarationsId, NO_REGISTERS);
       Label ok;
       __ LoadRoot(t0, Heap::kStackLimitRootIndex);
       __ Branch(&ok, hs, sp, Operand(t0));
       StackCheckStub stub;
@@ skipping 429 matching lines @@
 
 
 void FullCodeGenerator::EmitDeclaration(VariableProxy* proxy,
                                         VariableMode mode,
                                         FunctionLiteral* function,
                                         int* global_count) {
   // If it was not possible to allocate the variable at compile time, we
   // need to "declare" it at runtime to make sure it actually exists in the
   // local context.
   Variable* variable = proxy->var();
+  bool binding_needs_init =
+      mode == CONST || mode == CONST_HARMONY || mode == LET;
   switch (variable->location()) {
     case Variable::UNALLOCATED:
       ++(*global_count);
       break;
 
     case Variable::PARAMETER:
     case Variable::LOCAL:
       if (function != NULL) {
         Comment cmnt(masm_, "[ Declaration");
         VisitForAccumulatorValue(function);
         __ sw(result_register(), StackOperand(variable));
-      } else if (mode == CONST || mode == LET) {
+      } else if (binding_needs_init) {
           Comment cmnt(masm_, "[ Declaration");
           __ LoadRoot(t0, Heap::kTheHoleValueRootIndex);
           __ sw(t0, StackOperand(variable));
       }
       break;
 
       case Variable::CONTEXT:
       // The variable in the decl always resides in the current function
       // context.
       ASSERT_EQ(0, scope()->ContextChainLength(variable->scope()));
@@ skipping 15 matching lines @@
         // We know that we have written a function, which is not a smi.
         __ RecordWriteContextSlot(cp,
                                   offset,
                                   result_register(),
                                   a2,
                                   kRAHasBeenSaved,
                                   kDontSaveFPRegs,
                                   EMIT_REMEMBERED_SET,
                                   OMIT_SMI_CHECK);
         PrepareForBailoutForId(proxy->id(), NO_REGISTERS);
-      } else if (mode == CONST || mode == LET) {
+      } else if (binding_needs_init) {
           Comment cmnt(masm_, "[ Declaration");
           __ LoadRoot(at, Heap::kTheHoleValueRootIndex);
           __ sw(at, ContextOperand(cp, variable->index()));
           // No write barrier since the_hole_value is in old space.
           PrepareForBailoutForId(proxy->id(), NO_REGISTERS);
       }
       break;
 
     case Variable::LOOKUP: {
       Comment cmnt(masm_, "[ Declaration");
       __ li(a2, Operand(variable->name()));
-      // Declaration nodes are always introduced in one of three modes.
-      ASSERT(mode == VAR || mode == CONST || mode == LET);
-      PropertyAttributes attr = (mode == CONST) ? READ_ONLY : NONE;
+      // Declaration nodes are always introduced in one of four modes.
+      ASSERT(mode == VAR ||
+             mode == CONST ||
+             mode == CONST_HARMONY ||
+             mode == LET);
+      PropertyAttributes attr = (mode == CONST || mode == CONST_HARMONY)
+        ? READ_ONLY : NONE;
       __ li(a1, Operand(Smi::FromInt(attr)));
       // Push initial value, if any.
       // Note: For variables we must not push an initial value (such as
       // 'undefined') because we may have a (legal) redeclaration and we
       // must not destroy the current value.
       if (function != NULL) {
         __ Push(cp, a2, a1);
         // Push initial value for function declaration.
         VisitForStackValue(function);
-      } else if (mode == CONST || mode == LET) {
+      } else if (binding_needs_init) {
           __ LoadRoot(a0, Heap::kTheHoleValueRootIndex);
           __ Push(cp, a2, a1, a0);
       } else {
         ASSERT(Smi::FromInt(0) == 0);
         __ mov(a0, zero_reg);  // Smi::FromInt(0) indicates no initial value.
         __ Push(cp, a2, a1, a0);
       }
       __ CallRuntime(Runtime::kDeclareContextSlot, 4);
       break;
     }
@@ skipping 408 matching lines @@
   // introducing variables.  In those cases, we do not want to
   // perform a runtime call for all variables in the scope
   // containing the eval.
   if (var->mode() == DYNAMIC_GLOBAL) {
     EmitLoadGlobalCheckExtensions(var, typeof_state, slow);
     __ Branch(done);
   } else if (var->mode() == DYNAMIC_LOCAL) {
     Variable* local = var->local_if_not_shadowed();
     __ lw(v0, ContextSlotOperandCheckExtensions(local, slow));
     if (local->mode() == CONST ||
+        local->mode() == CONST_HARMONY ||
         local->mode() == LET) {
       __ LoadRoot(at, Heap::kTheHoleValueRootIndex);
       __ subu(at, v0, at);  // Sub as compare: at == 0 on eq.
       if (local->mode() == CONST) {
         __ LoadRoot(a0, Heap::kUndefinedValueRootIndex);
         __ movz(v0, a0, at);  // Conditional move: return Undefined if TheHole.
-      } else {  // LET
+      } else {  // LET || CONST_HARMONY
         __ Branch(done, ne, at, Operand(zero_reg));
         __ li(a0, Operand(var->name()));
         __ push(a0);
         __ CallRuntime(Runtime::kThrowReferenceError, 1);
       }
     }
     __ Branch(done);
   }
 }
 
@@ skipping 17 matching lines @@
       context()->Plug(v0);
       break;
     }
 
     case Variable::PARAMETER:
     case Variable::LOCAL:
     case Variable::CONTEXT: {
       Comment cmnt(masm_, var->IsContextSlot()
                               ? "Context variable"
                               : "Stack variable");
-      if (var->mode() != LET && var->mode() != CONST) {
+      if (!var->binding_needs_init()) {
         context()->Plug(var);
       } else {
         // Let and const need a read barrier.
         GetVar(v0, var);
         __ LoadRoot(at, Heap::kTheHoleValueRootIndex);
         __ subu(at, v0, at);  // Sub as compare: at == 0 on eq.
-        if (var->mode() == LET) {
+        if (var->mode() == LET || var->mode() == CONST_HARMONY) {
+          // Throw a reference error when using an uninitialized let/const
+          // binding in harmony mode.
           Label done;
           __ Branch(&done, ne, at, Operand(zero_reg));
           __ li(a0, Operand(var->name()));
           __ push(a0);
           __ CallRuntime(Runtime::kThrowReferenceError, 1);
           __ bind(&done);
         } else {
+          // Uninitalized const bindings outside of harmony mode are unholed.
+          ASSERT(var->mode() == CONST);
           __ LoadRoot(a0, Heap::kUndefinedValueRootIndex);
           __ movz(v0, a0, at);  // Conditional move: Undefined if TheHole.
         }
         context()->Plug(v0);
       }
       break;
     }
 
     case Variable::LOOKUP: {
       Label done, slow;
@@ skipping 657 matching lines @@
       __ sw(result_register(), location);
       if (var->IsContextSlot()) {
         // RecordWrite may destroy all its register arguments.
         __ mov(a3, result_register());
         int offset = Context::SlotOffset(var->index());
         __ RecordWriteContextSlot(
             a1, offset, a3, a2, kRAHasBeenSaved, kDontSaveFPRegs);
       }
     }
 
-  } else if (var->mode() != CONST) {
-    // Assignment to var or initializing assignment to let.
+  } else if (!var->is_const_mode() || op == Token::INIT_CONST_HARMONY) {
+    // Assignment to var or initializing assignment to let/const
+    // in harmony mode.
     if (var->IsStackAllocated() || var->IsContextSlot()) {
       MemOperand location = VarOperand(var, a1);
       if (FLAG_debug_code && op == Token::INIT_LET) {
         // Check for an uninitialized let binding.
         __ lw(a2, location);
         __ LoadRoot(t0, Heap::kTheHoleValueRootIndex);
         __ Check(eq, "Let binding re-initialization.", a2, Operand(t0));
       }
       // Perform the assignment.
       __ sw(v0, location);
@@ skipping 2357 matching lines @@
   *context_length = 0;
   return previous_;
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_MIPS