Generate code for store buffer updates in open-coded object field stores.

runtime/vm/assembler_ia32.cc

Index: runtime/vm/assembler_ia32.cc
diff --git a/runtime/vm/assembler_ia32.cc b/runtime/vm/assembler_ia32.cc
index 72bd938eb74664c3e0133b0228d395cd6284556c..04534c7814e9ef0521c587c1ff7c2272c388574e 100644
--- a/runtime/vm/assembler_ia32.cc
+++ b/runtime/vm/assembler_ia32.cc
@@ -13,6 +13,8 @@
 
 namespace dart {
 
+DECLARE_RUNTIME_ENTRY(StoreBuffer);
+
 DEFINE_FLAG(bool, print_stop_message, true, "Print stop message.");
 DEFINE_FLAG(bool, code_comments, false,
             "Include comments into code and disassembly");
@@ -1365,8 +1367,58 @@ void Assembler::CompareObject(Register reg, const Object& object) {
 void Assembler::StoreIntoObject(Register object,
                                 const FieldAddress& dest,
                                 Register value) {
-  // TODO(iposva): Add write barrier.
   movl(dest, value);
+  Label done;
+  // Check that 'value' is a new object.  Store buffer updates are not
+  // required when storing a smi or an old object.
+  testl(value, Immediate(kNewObjectAlignmentOffset | kHeapObjectTag));
+  j(NOT_EQUAL, &done, Assembler::kNearJump);
+  // Check that 'object' is an old object.  A store buffer update is
+  // not required when storing into a new object.
+  testl(object, Immediate(kOldObjectAlignmentOffset | kHeapObjectTag));
+  j(NOT_EQUAL, &done, Assembler::kNearJump);
+  // A store buffer update is required.
+  pushl(object);  // Save 'object' register
+  pushl(value);  // Save 'value' register
+  pushl(dest);  // Push argument
+  CallRuntime(kStoreBufferRuntimeEntry);

[srdjan, 2012/06/15 21:12:08]

I'd rather have a CallLeafRuntime which would store/restore all caller saved
registers. This way, the compiler has to spill all caller-saved registers across
each StoreIntoObject.

[cshapiro, 2012/06/15 23:17:32]

Per our off-line discussion, I have added a pushal and popal around the
CallRuntime invocation.

+  popl(value);  // Pop argument
+  popl(value);  // Restore 'value' register
+  popl(object);  // Restore 'object' register
+  Bind(&done);
+}
+
+
+void Assembler::StoreIntoObjectNoBarrier(Register object,
+                                         const FieldAddress& dest,
+                                         Register value) {
+  movl(dest, value);
+#if defined(DEBUG)
+  Label done;
+  testl(value, Immediate(kNewObjectAlignmentOffset | kHeapObjectTag));
+  j(NOT_EQUAL, &done, Assembler::kNearJump);
+  testl(object, Immediate(kOldObjectAlignmentOffset | kHeapObjectTag));
+  j(NOT_EQUAL, &done, Assembler::kNearJump);
+  Stop("Store buffer update is required");
+  Bind(&done);
+#endif
+  // No store buffer update.
+}
+
+
+void Assembler::StoreIntoObjectNoBarrier(Register object,
+                                         const FieldAddress& dest,
+                                         const Object& value) {
+  if (value.IsSmi()) {
+    movl(dest, Immediate(reinterpret_cast<int32_t>(value.raw())));
+  } else {
+    ASSERT(value.IsOld());
+    AssemblerBuffer::EnsureCapacity ensured(&buffer_);
+    EmitUint8(0xC7);
+    EmitOperand(0, dest);
+    buffer_.EmitObject(value);
+  }
+  // No store buffer update.
 }