Concurrent sweep on x64.

runtime/vm/stub_code_x64.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"
 #if defined(TARGET_ARCH_X64)
 
 #include "vm/assembler.h"
 #include "vm/compiler.h"
 #include "vm/dart_entry.h"
@@ skipping 910 matching lines @@
   // Restore the frame pointer.
   __ LeaveStubFrame();
   __ ret();
 }
 
 
 DECLARE_LEAF_RUNTIME_ENTRY(void, StoreBufferBlockProcess, Isolate* isolate);
 
 // Helper stub to implement Assembler::StoreIntoObject.
 // Input parameters:
-//   RAX: Address being stored
+//   RDX: Address being stored
 void StubCode::GenerateUpdateStoreBufferStub(Assembler* assembler) {
   // Save registers being destroyed.
-  __ pushq(RDX);
+  __ pushq(RAX);
   __ pushq(RCX);
 
   Label add_to_buffer;
   // Check whether this object has already been remembered. Skip adding to the
   // store buffer if the object is in the store buffer already.
-  // Spilled: RDX, RCX
-  // RAX: Address being stored
-  __ movq(RCX, FieldAddress(RAX, Object::tags_offset()));
+  // Spilled: RAX, RCX
+  // RDX: Address being stored
+  Label reload;
+  __ Bind(&reload);
+  __ movq(RCX, FieldAddress(RDX, Object::tags_offset()));
   __ testq(RCX, Immediate(1 << RawObject::kRememberedBit));
   __ j(EQUAL, &add_to_buffer, Assembler::kNearJump);
   __ popq(RCX);
-  __ popq(RDX);
+  __ popq(RAX);
   __ ret();
 
+  // Update the tags that this object has been remembered.
+  // RDX: Address being stored
+  // RAX: Current tag value
   __ Bind(&add_to_buffer);
+  __ movq(RCX, RAX);
   __ orq(RCX, Immediate(1 << RawObject::kRememberedBit));
-  __ movq(FieldAddress(RAX, Object::tags_offset()), RCX);
+  // Compare the tag word with RAX, update to RCX if unchanged.
+  __ LockCmpxchgq(FieldAddress(RDX, Object::tags_offset()), RCX);
+  __ j(NOT_EQUAL, &reload);
 
   // Load the isolate.
-  // RAX: Address being stored
-  __ LoadIsolate(RDX);
+  // RDX: Address being stored
+  __ LoadIsolate(RAX);
 
   // Load the StoreBuffer block out of the isolate. Then load top_ out of the
   // StoreBufferBlock and add the address to the pointers_.
-  // RAX: Address being stored
-  // RDX: Isolate
-  __ movq(RDX, Address(RDX, Isolate::store_buffer_offset()));
-  __ movl(RCX, Address(RDX, StoreBufferBlock::top_offset()));
-  __ movq(Address(RDX, RCX, TIMES_8, StoreBufferBlock::pointers_offset()), RAX);
+  // RDX: Address being stored
+  // RAX: Isolate
+  __ movq(RAX, Address(RAX, Isolate::store_buffer_offset()));
+  __ movl(RCX, Address(RAX, StoreBufferBlock::top_offset()));
+  __ movq(Address(RAX, RCX, TIMES_8, StoreBufferBlock::pointers_offset()), RDX);
 
   // Increment top_ and check for overflow.
   // RCX: top_
-  // RDX: StoreBufferBlock
+  // RAX: StoreBufferBlock
   Label L;
   __ incq(RCX);
-  __ movl(Address(RDX, StoreBufferBlock::top_offset()), RCX);
+  __ movl(Address(RAX, StoreBufferBlock::top_offset()), RCX);
   __ cmpl(RCX, Immediate(StoreBufferBlock::kSize));
   // Restore values.
   __ popq(RCX);
-  __ popq(RDX);
+  __ popq(RAX);
   __ j(EQUAL, &L, Assembler::kNearJump);
   __ ret();
 
   // Handle overflow: Call the runtime leaf function.
   __ Bind(&L);
   // Setup frame, push callee-saved registers.
   __ EnterCallRuntimeFrame(0);
   __ LoadIsolate(CallingConventions::kArg1Reg);
   __ CallRuntime(kStoreBufferBlockProcessRuntimeEntry, 1);
   __ LeaveCallRuntimeFrame();
@@ skipping 966 matching lines @@
 
   __ movq(left, Address(RSP, 2 * kWordSize));
   __ movq(right, Address(RSP, 1 * kWordSize));
   GenerateIdenticalWithNumberCheckStub(assembler, left, right);
   __ ret();
 }
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_X64