Write-barrier verification on ARM.

runtime/vm/assembler_arm.h

 // 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.
 
 #ifndef VM_ASSEMBLER_ARM_H_
 #define VM_ASSEMBLER_ARM_H_
 
 #ifndef VM_ASSEMBLER_H_
 #error Do not include assembler_arm.h directly; use assembler.h instead.
 #endif
@@ skipping 179 matching lines @@
 class Address : public ValueObject {
  public:
   enum OffsetKind {
     Immediate,
     IndexRegister,
     ScaledIndexRegister,
   };
 
   // Memory operand addressing mode
   enum Mode {
+    kModeMask    = (8|4|1) << 21,
     // bit encoding P U W
     Offset       = (8|4|0) << 21,  // offset (w/o writeback to base)
     PreIndex     = (8|4|1) << 21,  // pre-indexed addressing with writeback
     PostIndex    = (0|4|0) << 21,  // post-indexed addressing with writeback
     NegOffset    = (8|0|0) << 21,  // negative offset (w/o writeback to base)
     NegPreIndex  = (8|0|1) << 21,  // negative pre-indexed with writeback
     NegPostIndex = (0|0|0) << 21   // negative post-indexed with writeback
   };
 
   Address(const Address& other)
@@ skipping 46 matching lines @@
                                 int32_t offset,
                                 int32_t* offset_mask);
   static bool CanHoldStoreOffset(OperandSize size,
                                  int32_t offset,
                                  int32_t* offset_mask);
   static bool CanHoldImmediateOffset(bool is_load,
                                      intptr_t cid,
                                      int64_t offset);
 
  private:
+  Register rn() const {
+    return Instr::At(reinterpret_cast<uword>(&encoding_))->RnField();
+  }
+
+  Register rm() const {
+    return ((kind() == IndexRegister) || (kind() == ScaledIndexRegister)) ?
+        Instr::At(reinterpret_cast<uword>(&encoding_))->RmField() :
+        kNoRegister;
+  }
+
+  Mode mode() const { return static_cast<Mode>(encoding() & kModeMask); }
+
   uint32_t encoding() const { return encoding_; }
 
   // Encoding for addressing mode 3.
   uint32_t encoding3() const;
 
   // Encoding for vfp load/store addressing.
   uint32_t vencoding() const;
 
   OffsetKind kind() const { return kind_; }
 
@@ skipping 50 matching lines @@
   const ZoneGrowableArray<intptr_t>& GetPointerOffsets() const {
     ASSERT(buffer_.pointer_offsets().length() == 0);  // No pointers in code.
     return buffer_.pointer_offsets();
   }
   const GrowableObjectArray& object_pool() const { return object_pool_; }
 
   bool use_far_branches() const {
     return FLAG_use_far_branches || use_far_branches_;
   }
 
+#if defined(TESTING) || defined(DEBUG)
+  // Used in unit tests and to ensure predictable verification code size in
+  // FlowGraphCompiler::EmitEdgeCounter.
   void set_use_far_branches(bool b) {
-    ASSERT(buffer_.Size() == 0);
     use_far_branches_ = b;
   }
+#endif  // TESTING || DEBUG
 
   void FinalizeInstructions(const MemoryRegion& region) {
     buffer_.FinalizeInstructions(region);
   }
 
   // Debugging and bringup support.
   void Stop(const char* message);
   void Unimplemented(const char* message);
   void Untested(const char* message);
   void Unreachable(const char* message);
@@ skipping 321 matching lines @@
   // Store value_even, value_odd, value_even, ... into the words in the address
   // range [begin, end), assumed to be uninitialized fields in object (tagged).
   // The stores must not need a generational store barrier (e.g., smi/null),
   // and (value_even, value_odd) must be a valid register pair.
   // Destroys register 'begin'.
   void InitializeFieldsNoBarrier(Register object,
                                  Register begin,
                                  Register end,
                                  Register value_even,
                                  Register value_odd);
-  // Like above, for the range [begin, begin+count*kWordSize), unrolled.
+  // Like above, for the range [base+begin_offset, base+end_offset), unrolled.
   void InitializeFieldsNoBarrierUnrolled(Register object,
-                                         Register begin,
-                                         intptr_t count,
+                                         Register base,
+                                         intptr_t begin_offset,
+                                         intptr_t end_offset,
                                          Register value_even,
                                          Register value_odd);
 
+  // Stores a Smi value into a heap object field that always contains a Smi.
+  void StoreIntoSmiField(const Address& dest, Register value);
+
   void LoadClassId(Register result, Register object, Condition cond = AL);
   void LoadClassById(Register result, Register class_id);
   void LoadClass(Register result, Register object, Register scratch);
   void CompareClassId(Register object, intptr_t class_id, Register scratch);
   void LoadTaggedClassIdMayBeSmi(Register result, Register object);
 
   void LoadWordFromPoolOffset(Register rd, int32_t offset, Condition cond = AL);
   void LoadFromOffset(OperandSize type,
                       Register reg,
                       Register base,
@@ skipping 343 matching lines @@
   int32_t EncodeTstOffset(int32_t offset, int32_t inst);
   int32_t DecodeTstOffset(int32_t inst);
 
   void StoreIntoObjectFilter(Register object, Register value, Label* no_update);
 
   // Shorter filtering sequence that assumes that value is not a smi.
   void StoreIntoObjectFilterNoSmi(Register object,
                                   Register value,
                                   Label* no_update);
 
+  // Helpers for write-barrier verification.
+
+  // Returns VerifiedMemory::offset() as an Operand.
+  Operand GetVerifiedMemoryShadow();
+  // Writes value to [base + offset] and also its shadow location, if enabled.
+  void WriteShadowedField(Register base,
+                          intptr_t offset,
+                          Register value,
+                          Condition cond = AL);
+  void WriteShadowedFieldPair(Register base,
+                              intptr_t offset,
+                              Register value_even,
+                              Register value_odd,
+                              Condition cond = AL);
+  // Writes new_value to address and its shadow location, if enabled, after
+  // verifying that its old value matches its shadow.
+  void VerifiedWrite(const Address& address, Register new_value);
+
   DISALLOW_ALLOCATION();
   DISALLOW_COPY_AND_ASSIGN(Assembler);
 };
 
 }  // namespace dart
 
 #endif  // VM_ASSEMBLER_ARM_H_