Deletion barrier: Distinguish+verify field initialization in ia32 generated code.

runtime/vm/assembler_ia32.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_IA32_H_
 #define VM_ASSEMBLER_IA32_H_
 
 #ifndef VM_ASSEMBLER_H_
 #error Do not include assembler_ia32.h directly; use assembler.h instead.
 #endif
@@ skipping 518 matching lines @@
   void cmpl(Register reg, const Immediate& imm);
   void cmpl(Register reg0, Register reg1);
   void cmpl(Register reg, const Address& address);
 
   void cmpl(const Address& address, Register reg);
   void cmpl(const Address& address, const Immediate& imm);
   void cmpb(const Address& address, const Immediate& imm);
 
   void testl(Register reg1, Register reg2);
   void testl(Register reg, const Immediate& imm);
+  void testb(const Address& address, const Immediate& imm);
 
   void andl(Register dst, const Immediate& imm);
   void andl(Register dst, Register src);
   void andl(Register dst, const Address& address);
 
   void orl(Register dst, const Immediate& imm);
   void orl(Register dst, Register src);
   void orl(Register dst, const Address& address);
   void orl(const Address& address, Register dst);
 
@@ skipping 112 matching lines @@
   void LoadObject(Register dst, const Object& object);
 
   // If 'object' is a large Smi, xor it with a per-assembler cookie value to
   // prevent user-controlled immediates from appearing in the code stream.
   void LoadObjectSafely(Register dst, const Object& object);
 
   void PushObject(const Object& object);
   void CompareObject(Register reg, const Object& object);
   void LoadDoubleConstant(XmmRegister dst, double value);
 
+  // When storing into a heap object field, knowledge of the previous content
+  // is expressed through these constants.
+  enum FieldContent {
+    kEmptySmiOrNull,  // Empty = garbage/zapped in release/debug mode.

[Ivan Posva, 2015/01/08 19:34:51]

Does this mean an empty Smi or kEmptyOrSmiOrNull?

[koda, 2015/01/08 20:25:34]

Renamed to clarify.

+    kHeapObjectOrSmi,
+    kOnlySmi,
+  };
+
   void StoreIntoObject(Register object,  // Object we are storing into.
                        const Address& dest,  // Where we are storing into.
                        Register value,  // Value we are storing.
                        bool can_value_be_smi = true);
 
   void StoreIntoObjectNoBarrier(Register object,
                                 const Address& dest,
-                                Register value);
+                                Register value,
+                                FieldContent old_content = kHeapObjectOrSmi);
+  void InitializeFieldNoBarrier(Register object,
+                                const Address& dest,
+                                Register value) {
+    return StoreIntoObjectNoBarrier(object, dest, value, kEmptySmiOrNull);
+  }
   void StoreIntoObjectNoBarrier(Register object,
                                 const Address& dest,
-                                const Object& value);
+                                const Object& value,
+                                FieldContent old_content = kHeapObjectOrSmi);
+  void InitializeFieldNoBarrier(Register object,
+                                const Address& dest,
+                                const Object& value) {
+    return StoreIntoObjectNoBarrier(object, dest, value, kEmptySmiOrNull);
+  }
 
   // Stores a Smi value into a heap object field that always contains a Smi.
   void StoreIntoSmiField(const Address& dest, Register value);
   void ZeroSmiField(const Address& dest);
   // Increments a Smi field. Leaves flags in same state as an 'addl'.
   void IncrementSmiField(const Address& dest, int32_t increment);
 
   void DoubleNegate(XmmRegister d);
   void FloatNegate(XmmRegister f);
 
@@ skipping 246 matching lines @@
 
   void EmitGenericShift(int rm, Register reg, const Immediate& imm);
   void EmitGenericShift(int rm, const Operand& operand, Register shifter);
 
   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);
-
-  // Analogous to VerifiedMemory::Verify(address, kWordSize).
-  void VerifyHeapWord(const Address& address);
-  // Analogous to VerifiedMemory::Write.
-  void VerifiedWrite(const Address& dest, Register value);
+#if defined(DEBUG)
+  void VerifyUninitialized(const Address& address);
+  void VerifyObjectOrSmi(const Address& address);
+  void VerifySmi(const Address& address, const char* stop_msg = "Expected Smi");
+#endif  // DEBUG
+  // Like VerifiedMemory::Verify(address, kWordSize) and ::Write, but also,
+  // in DEBUG mode, verifies that 'address' has content of type 'old_content'.
+  void VerifyHeapWord(const Address& address, FieldContent old_content);
+  void VerifiedWrite(const Address& dest,
+                     Register value,
+                     FieldContent old_content);
   void UnverifiedStoreOldObject(const Address& dest, const Object& value);
 
   int32_t jit_cookie();
 
   AssemblerBuffer buffer_;
   GrowableObjectArray& object_pool_;  // Object pool is not used on ia32.
   intptr_t prologue_offset_;
   int32_t jit_cookie_;
   GrowableArray<CodeComment*> comments_;
 
@@ skipping 28 matching lines @@
 }
 
 
 inline void Assembler::EmitOperandSizeOverride() {
   EmitUint8(0x66);
 }
 
 }  // namespace dart
 
 #endif  // VM_ASSEMBLER_IA32_H_