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

src/arm/code-stubs-arm.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_ARM
 
 #include "src/base/bits.h"
 #include "src/bootstrapper.h"
@@ skipping 5102 matching lines @@
   // Go up the context chain to the script context.
   for (int i = 0; i < depth(); i++) {
     __ ldr(context_temp, ContextOperand(context, Context::PREVIOUS_INDEX));
     context = context_temp;
   }
 
   // Load the PropertyCell at the specified slot.
   __ add(cell, context, Operand(slot, LSL, kPointerSizeLog2));
   __ ldr(cell, ContextOperand(cell));
 
-  // Check that cell value is not the_hole.
-  __ ldr(cell_value, FieldMemOperand(cell, PropertyCell::kValueOffset));
-  __ CompareRoot(cell_value, Heap::kTheHoleValueRootIndex);
-  __ b(eq, &slow_case);
-
   // Load PropertyDetails for the cell (actually only the cell_type and kind).
   __ ldr(cell_details, FieldMemOperand(cell, PropertyCell::kDetailsOffset));
   __ SmiUntag(cell_details);
   __ and_(cell_details, cell_details,
           Operand(PropertyDetails::PropertyCellTypeField::kMask |
-                  PropertyDetails::KindField::kMask));
+                  PropertyDetails::KindField::kMask |
+                  PropertyDetails::kAttributesReadOnlyMask));
 
   // Check if PropertyCell holds mutable data.
   Label not_mutable_data;
   __ cmp(cell_details, Operand(PropertyDetails::PropertyCellTypeField::encode(
                                    PropertyCellType::kMutable) |
                                PropertyDetails::KindField::encode(kData)));
   __ b(ne, &not_mutable_data);
   __ JumpIfSmi(value, &fast_smi_case);
 
   __ bind(&fast_heapobject_case);
   __ str(value, FieldMemOperand(cell, PropertyCell::kValueOffset));
   // RecordWriteField clobbers the value register, so we copy it before the
   // call.
   __ mov(r4, Operand(value));
   __ RecordWriteField(cell, PropertyCell::kValueOffset, r4, scratch,
                       kLRHasNotBeenSaved, kDontSaveFPRegs, EMIT_REMEMBERED_SET,
                       OMIT_SMI_CHECK);
   __ Ret();
 
   __ bind(&not_mutable_data);
   // Check if PropertyCell value matches the new value (relevant for Constant,
   // ConstantType and Undefined cells).
   Label not_same_value;
+  __ ldr(cell_value, FieldMemOperand(cell, PropertyCell::kValueOffset));
   __ cmp(cell_value, value);
   __ b(ne, &not_same_value);
 
+  // Make sure the PropertyCell is not marked READ_ONLY.
+  __ tst(cell_details, Operand(PropertyDetails::kAttributesReadOnlyMask));
+  __ b(ne, &slow_case);
+
   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.
     __ cmp(cell_details, Operand(PropertyDetails::PropertyCellTypeField::encode(
                                      PropertyCellType::kConstant) |
                                  PropertyDetails::KindField::encode(kData)));
     __ b(eq, &done);
     __ cmp(cell_details, Operand(PropertyDetails::PropertyCellTypeField::encode(
                                      PropertyCellType::kConstantType) |
                                  PropertyDetails::KindField::encode(kData)));
     __ b(eq, &done);
     __ cmp(cell_details, Operand(PropertyDetails::PropertyCellTypeField::encode(
                                      PropertyCellType::kUndefined) |
                                  PropertyDetails::KindField::encode(kData)));
     __ Check(eq, kUnexpectedValue);
     __ 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).
   __ cmp(cell_details, Operand(PropertyDetails::PropertyCellTypeField::encode(
                                    PropertyCellType::kConstantType) |
                                PropertyDetails::KindField::encode(kData)));
   __ b(ne, &slow_case);
 
   // 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, &value_is_heap_object);
   __ JumpIfNotSmi(cell_value, &slow_case);
@@ skipping 338 matching lines @@
                            MemOperand(fp, 6 * kPointerSize), NULL);
 }
 
 
 #undef __
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_ARM