[stubs] Properly handle read-only properties in StoreGlobalViaContextStub.

src/mips/code-stubs-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
 
 #include "src/base/bits.h"
 #include "src/bootstrapper.h"
@@ skipping 5313 matching lines @@
     __ lw(cell_reg, ContextOperand(context_reg, Context::PREVIOUS_INDEX));
     context_reg = cell_reg;
   }
 
   // Load the PropertyCell at the specified slot.
   __ sll(at, slot_reg, kPointerSizeLog2);
   __ Addu(at, at, Operand(context_reg));
   __ Addu(at, at, Context::SlotOffset(0));
   __ lw(cell_reg, MemOperand(at));
 
-  // Check that cell value is not the_hole.
-  __ lw(cell_value_reg, FieldMemOperand(cell_reg, PropertyCell::kValueOffset));
-  __ LoadRoot(at, Heap::kTheHoleValueRootIndex);
-  __ Branch(&slow_case, eq, cell_value_reg, Operand(at));
-
   // Load PropertyDetails for the cell (actually only the cell_type and kind).
   __ lw(cell_details_reg,
         FieldMemOperand(cell_reg, PropertyCell::kDetailsOffset));
   __ SmiUntag(cell_details_reg);
   __ And(cell_details_reg, cell_details_reg,
          PropertyDetails::PropertyCellTypeField::kMask |
-             PropertyDetails::KindField::kMask);
+             PropertyDetails::KindField::kMask |
+             PropertyDetails::kAttributesReadOnlyMask);
 
   // Check if PropertyCell holds mutable data.
   Label not_mutable_data;
   __ Branch(&not_mutable_data, ne, cell_details_reg,
             Operand(PropertyDetails::PropertyCellTypeField::encode(
                         PropertyCellType::kMutable) |
                     PropertyDetails::KindField::encode(kData)));
   __ JumpIfSmi(value_reg, &fast_smi_case);
   __ bind(&fast_heapobject_case);
   __ sw(value_reg, FieldMemOperand(cell_reg, PropertyCell::kValueOffset));
   __ RecordWriteField(cell_reg, PropertyCell::kValueOffset, value_reg,
                       cell_details_reg, kRAHasNotBeenSaved, kDontSaveFPRegs,
                       EMIT_REMEMBERED_SET, OMIT_SMI_CHECK);
   // RecordWriteField clobbers the value register, so we need to reload.
   __ Ret(USE_DELAY_SLOT);
   __ lw(value_reg, FieldMemOperand(cell_reg, PropertyCell::kValueOffset));
   __ bind(&not_mutable_data);
 
   // Check if PropertyCell value matches the new value (relevant for Constant,
   // ConstantType and Undefined cells).
   Label not_same_value;
+  __ lw(cell_value_reg, FieldMemOperand(cell_reg, PropertyCell::kValueOffset));
   __ Branch(&not_same_value, ne, value_reg, Operand(cell_value_reg));
+  // Make sure the PropertyCell is not marked READ_ONLY.
+  __ And(at, cell_details_reg, PropertyDetails::kAttributesReadOnlyMask);
+  __ Branch(&slow_case, ne, at, Operand(zero_reg));
   if (FLAG_debug_code) {
     Label done;
     // This can only be true for Constant, ConstantType and Undefined cells,
     // because we never store the_hole via this stub.
     __ Branch(&done, eq, cell_details_reg,
               Operand(PropertyDetails::PropertyCellTypeField::encode(
                           PropertyCellType::kConstant) |
                       PropertyDetails::KindField::encode(kData)));
     __ Branch(&done, eq, cell_details_reg,
               Operand(PropertyDetails::PropertyCellTypeField::encode(
                           PropertyCellType::kConstantType) |
                       PropertyDetails::KindField::encode(kData)));
     __ Check(eq, kUnexpectedValue, cell_details_reg,
              Operand(PropertyDetails::PropertyCellTypeField::encode(
                          PropertyCellType::kUndefined) |
                      PropertyDetails::KindField::encode(kData)));
     __ bind(&done);
   }
   __ Ret();
   __ bind(&not_same_value);
 
-  // Check if PropertyCell contains data with constant type.
+  // Check if PropertyCell contains data with constant type (and is not
+  // READ_ONLY).
   __ Branch(&slow_case, ne, cell_details_reg,
             Operand(PropertyDetails::PropertyCellTypeField::encode(
                         PropertyCellType::kConstantType) |
                     PropertyDetails::KindField::encode(kData)));
 
   // Now either both old and new values must be SMIs or both must be heap
   // objects with same map.
   Label value_is_heap_object;
   __ JumpIfNotSmi(value_reg, &value_is_heap_object);
   __ JumpIfNotSmi(cell_value_reg, &slow_case);
@@ skipping 322 matching lines @@
                            MemOperand(fp, 6 * kPointerSize), NULL);
 }
 
 
 #undef __
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_MIPS