Fix write barrier for StoreKeyedFastElements on ARM

src/arm/lithium-codegen-arm.cc

 // Copyright 2012 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 3833 matching lines @@
 }
 
 
 void LCodeGen::DoStoreKeyedFastElement(LStoreKeyedFastElement* instr) {
   Register value = ToRegister(instr->value());
   Register elements = ToRegister(instr->object());
   Register key = instr->key()->IsRegister() ? ToRegister(instr->key()) : no_reg;
   Register scratch = scratch0();
 
   // Do the store.
+  int offset = 0;
+  Register store_base = scratch;
   if (instr->key()->IsConstantOperand()) {
     ASSERT(!instr->hydrogen()->NeedsWriteBarrier());
     LConstantOperand* const_operand = LConstantOperand::cast(instr->key());
-    int offset =
-        (ToInteger32(const_operand) + instr->additional_index()) * kPointerSize
-        + FixedArray::kHeaderSize;
-    __ str(value, FieldMemOperand(elements, offset));
+    offset = (ToInteger32(const_operand) + instr->additional_index()) *

[Michael Starzinger, 2012/07/31 13:42:32]

Can we use FixedArray::OffsetOfElementAt() for this?

+        kPointerSize + FixedArray::kHeaderSize;
+    store_base = elements;
   } else {
     // Even though the HLoadKeyedFastElement instruction forces the input
     // representation for the key to be an integer, the input gets replaced
     // during bound check elimination with the index argument to the bounds
     // check, which can be tagged, so that case must be handled here, too.
     if (instr->hydrogen()->key()->representation().IsTagged()) {
       __ add(scratch, elements,
              Operand(key, LSL, kPointerSizeLog2 - kSmiTagSize));
     } else {
       __ add(scratch, elements, Operand(key, LSL, kPointerSizeLog2));
     }
-    uint32_t offset = FixedArray::kHeaderSize +
+    offset = FixedArray::kHeaderSize +
         (instr->additional_index() << kPointerSizeLog2);
-    __ str(value, FieldMemOperand(scratch, offset));
   }
+  __ str(value, FieldMemOperand(store_base, offset));
 
   if (instr->hydrogen()->NeedsWriteBarrier()) {
     HType type = instr->hydrogen()->value()->type();
     SmiCheck check_needed =
         type.IsHeapObject() ? OMIT_SMI_CHECK : INLINE_SMI_CHECK;
     // Compute address of modified element and store it into key register.
-    __ add(key, scratch, Operand(FixedArray::kHeaderSize - kHeapObjectTag));
+    __ add(key, store_base, Operand(offset - kHeapObjectTag));
     __ RecordWrite(elements,
                    key,
                    value,
                    kLRHasBeenSaved,
                    kSaveFPRegs,
                    EMIT_REMEMBERED_SET,
                    check_needed);
   }
 }
 
@@ skipping 1571 matching lines @@
   __ sub(scratch, result, Operand(index, LSL, kPointerSizeLog2 - kSmiTagSize));
   __ ldr(result, FieldMemOperand(scratch,
                                  FixedArray::kHeaderSize - kPointerSize));
   __ bind(&done);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal