Write-barrier verification on ARM.

runtime/vm/intermediate_language_arm.cc

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/globals.h"  // Needed here to get TARGET_ARCH_ARM.
 #if defined(TARGET_ARCH_ARM)
 
 #include "vm/intermediate_language.h"
 
 #include "vm/cpu.h"
@@ skipping 2195 matching lines @@
   // Set the length field.
   __ StoreIntoObjectNoBarrier(R0,
                               FieldAddress(R0, Array::length_offset()),
                               kLengthReg);
 
   // Initialize all array elements to raw_null.
   // R0: new object start as a tagged pointer.
   // R3: new object end address.
   // R8: iterator which initially points to the start of the variable
   // data area to be initialized.
-  // R6, R7: null
+  // R6: null
   if (num_elements > 0) {
     const intptr_t array_size = instance_size - sizeof(RawArray);
     __ LoadImmediate(R6, reinterpret_cast<intptr_t>(Object::null()));
-    __ mov(R7, Operand(R6));
+    if (num_elements >= 2) {
+      __ mov(R7, Operand(R6));
+    }

[Ivan Posva, 2014/12/08 19:27:56]

Can you make sure to clobber R7 with RAW_NULL (0x1) in debug builds?

[koda, 2014/12/08 22:23:42]

Done.

     __ AddImmediate(R8, R0, sizeof(RawArray) - kHeapObjectTag);
     if (array_size < (kInlineArraySize * kWordSize)) {
-      __ InitializeFieldsNoBarrierUnrolled(R0, R8, num_elements, R6, R7);
+      __ InitializeFieldsNoBarrierUnrolled(R0, R8, 0, num_elements * kWordSize,
+                                           R6, R7);
     } else {
       __ InitializeFieldsNoBarrier(R0, R8, R3, R6, R7);
     }
   }
   __ b(done);
 }
 
 
 void CreateArrayInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
   const Register kLengthReg = R2;
@@ skipping 4502 matching lines @@
   compiler->GenerateCall(token_pos(), &label, stub_kind_, locs());
 #if defined(DEBUG)
   __ LoadImmediate(R4, kInvalidObjectPointer);
   __ LoadImmediate(R5, kInvalidObjectPointer);
 #endif
 }
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_ARM