Implement heap poisoning in ART's Optimizing compiler.

- Instrument ARM, ARM64, x86 and x86-64 code generators.
- Note: To turn heap poisoning on in Optimizing, set the
  environment variable `ART_HEAP_POISONING' to "true"
  before compiling ART.

Bug: 12687968
Change-Id: Ib3120b38cf805a8a50207a314b9ccc90c8d93740
diff --git a/compiler/utils/x86_64/assembler_x86_64.h b/compiler/utils/x86_64/assembler_x86_64.h
index 6b2b65d..61ffeab 100644
--- a/compiler/utils/x86_64/assembler_x86_64.h
+++ b/compiler/utils/x86_64/assembler_x86_64.h
@@ -669,7 +669,7 @@
   void LoadRef(ManagedRegister dest, FrameOffset  src) OVERRIDE;
 
   void LoadRef(ManagedRegister dest, ManagedRegister base, MemberOffset offs,
-               bool poison_reference) OVERRIDE;
+               bool unpoison_reference) OVERRIDE;
 
   void LoadRawPtr(ManagedRegister dest, ManagedRegister base, Offset offs) OVERRIDE;
 
@@ -767,6 +767,21 @@
   // Is the constant area empty? Return true if there are no literals in the constant area.
   bool IsConstantAreaEmpty() const { return constant_area_.GetSize() == 0; }
 
+  //
+  // Heap poisoning.
+  //
+
+  // Poison a heap reference contained in `reg`.
+  void PoisonHeapReference(CpuRegister reg) { negl(reg); }
+  // Unpoison a heap reference contained in `reg`.
+  void UnpoisonHeapReference(CpuRegister reg) { negl(reg); }
+  // Unpoison a heap reference contained in `reg` if heap poisoning is enabled.
+  void MaybeUnpoisonHeapReference(CpuRegister reg) {
+    if (kPoisonHeapReferences) {
+      UnpoisonHeapReference(reg);
+    }
+  }
+
  private:
   void EmitUint8(uint8_t value);
   void EmitInt32(int32_t value);