MIPS: Fix exception for assignment to uninitialised const.

src/mips/full-codegen-mips.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/v8.h"
 
 #if V8_TARGET_ARCH_MIPS
 
 // Note on Mips implementation:
 //
@@ skipping 2689 matching lines @@
 
 
 void FullCodeGenerator::EmitVariableAssignment(Variable* var, Token::Value op) {
   if (var->IsUnallocated()) {
     // Global var, const, or let.
     __ mov(StoreDescriptor::ValueRegister(), result_register());
     __ li(StoreDescriptor::NameRegister(), Operand(var->name()));
     __ lw(StoreDescriptor::ReceiverRegister(), GlobalObjectOperand());
     CallStoreIC();
 
-  } else if (op == Token::INIT_CONST_LEGACY) {
-    // Const initializers need a write barrier.
-    DCHECK(!var->IsParameter());  // No const parameters.
-    if (var->IsLookupSlot()) {
-      __ li(a0, Operand(var->name()));
-      __ Push(v0, cp, a0);  // Context and name.
-      __ CallRuntime(Runtime::kInitializeLegacyConstLookupSlot, 3);
-    } else {
-      DCHECK(var->IsStackAllocated() || var->IsContextSlot());
-      Label skip;
-      MemOperand location = VarOperand(var, a1);
-      __ lw(a2, location);
-      __ LoadRoot(at, Heap::kTheHoleValueRootIndex);
-      __ Branch(&skip, ne, a2, Operand(at));
-      EmitStoreToStackLocalOrContextSlot(var, location);
-      __ bind(&skip);
-    }
-
   } else if (var->mode() == LET && op != Token::INIT_LET) {
     // Non-initializing assignment to let variable needs a write barrier.
     DCHECK(!var->IsLookupSlot());
     DCHECK(var->IsStackAllocated() || var->IsContextSlot());
     Label assign;
     MemOperand location = VarOperand(var, a1);
     __ lw(a3, location);
     __ LoadRoot(t0, Heap::kTheHoleValueRootIndex);
     __ Branch(&assign, ne, a3, Operand(t0));
     __ li(a3, Operand(var->name()));
     __ push(a3);
     __ CallRuntime(Runtime::kThrowReferenceError, 1);
     // Perform the assignment.
     __ bind(&assign);
     EmitStoreToStackLocalOrContextSlot(var, location);
+
+  } else if (var->mode() == CONST && op != Token::INIT_CONST) {
+    // Assignment to const variable needs a write barrier.
+    DCHECK(!var->IsLookupSlot());
+    DCHECK(var->IsStackAllocated() || var->IsContextSlot());
+    Label const_error;
+    MemOperand location = VarOperand(var, a1);
+    __ lw(a3, location);
+    __ LoadRoot(at, Heap::kTheHoleValueRootIndex);
+    __ Branch(&const_error, ne, a3, Operand(at));
+    __ li(a3, Operand(var->name()));
+    __ push(a3);
+    __ CallRuntime(Runtime::kThrowReferenceError, 1);
+    __ bind(&const_error);
+    __ CallRuntime(Runtime::kThrowConstAssignError, 0);
+
   } else if (!var->is_const_mode() || op == Token::INIT_CONST) {
     if (var->IsLookupSlot()) {
       // Assignment to var.
       __ li(a1, Operand(var->name()));
       __ li(a0, Operand(Smi::FromInt(language_mode())));
       __ Push(v0, cp, a1, a0);  // Value, context, name, language mode.
       __ CallRuntime(Runtime::kStoreLookupSlot, 4);
     } else {
       // Assignment to var or initializing assignment to let/const in harmony
       // mode.
       DCHECK((var->IsStackAllocated() || var->IsContextSlot()));
       MemOperand location = VarOperand(var, a1);
       if (generate_debug_code_ && op == Token::INIT_LET) {
         // Check for an uninitialized let binding.
         __ lw(a2, location);
         __ LoadRoot(t0, Heap::kTheHoleValueRootIndex);
         __ Check(eq, kLetBindingReInitialization, a2, Operand(t0));
       }
       EmitStoreToStackLocalOrContextSlot(var, location);
     }
-  } else if (IsSignallingAssignmentToConst(var, op, language_mode())) {
-    __ CallRuntime(Runtime::kThrowConstAssignError, 0);
+
+  } else if (op == Token::INIT_CONST_LEGACY) {
+    // Const initializers need a write barrier.
+    DCHECK(!var->IsParameter());  // No const parameters.
+    if (var->IsLookupSlot()) {
+      __ li(a0, Operand(var->name()));
+      __ Push(v0, cp, a0);  // Context and name.
+      __ CallRuntime(Runtime::kInitializeLegacyConstLookupSlot, 3);
+    } else {
+      DCHECK(var->IsStackAllocated() || var->IsContextSlot());
+      Label skip;
+      MemOperand location = VarOperand(var, a1);
+      __ lw(a2, location);
+      __ LoadRoot(at, Heap::kTheHoleValueRootIndex);
+      __ Branch(&skip, ne, a2, Operand(at));
+      EmitStoreToStackLocalOrContextSlot(var, location);
+      __ bind(&skip);
+    }
+
+  } else {
+    DCHECK(var->mode() == CONST_LEGACY && op != Token::INIT_CONST_LEGACY);
+    if (is_strict(language_mode())) {
+      __ CallRuntime(Runtime::kThrowConstAssignError, 0);
+    }
+    // Silently ignore store in sloppy mode.
   }
 }
 
 
 void FullCodeGenerator::EmitNamedPropertyAssignment(Assignment* expr) {
   // Assignment to a property, using a named store IC.
   Property* prop = expr->target()->AsProperty();
   DCHECK(prop != NULL);
   DCHECK(prop->key()->IsLiteral());
 
@@ skipping 2670 matching lines @@
       Assembler::target_address_at(pc_immediate_load_address)) ==
          reinterpret_cast<uint32_t>(
              isolate->builtins()->OsrAfterStackCheck()->entry()));
   return OSR_AFTER_STACK_CHECK;
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_MIPS