- Remove extra jumps from store barrier on x64.

runtime/vm/assembler_x64.cc

Index: runtime/vm/assembler_x64.cc
===================================================================
--- runtime/vm/assembler_x64.cc	(revision 9013)
+++ runtime/vm/assembler_x64.cc	(working copy)
@@ -879,6 +879,15 @@
 }
 
 
+void Assembler::adcl(Register dst, Register src) {

[Vyacheslav Egorov (Google), 2012/06/22 10:36:28]

please add a test for this instruction in assembler tests

+  AssemblerBuffer::EnsureCapacity ensured(&buffer_);
+  Operand operand(src);
+  EmitOperandREX(dst, operand, REX_NONE);
+  EmitUint8(0x13);
+  EmitOperand(dst & 7, operand);
+}
+
+
 void Assembler::subl(Register dst, Register src) {
   AssemblerBuffer::EnsureCapacity ensured(&buffer_);
   Operand operand(src);
@@ -1405,14 +1414,11 @@
 void Assembler::StoreIntoObjectFilter(Register object,
                                       Register value,
                                       Label* no_update) {
-  // 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(PARITY_ODD, no_update, Assembler::kNearJump);
-  j(ZERO, no_update, 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(kNewObjectAlignmentOffset));
+  andl(value, Immediate(0x5));
+  shrl(value, Immediate(1));
+  adcl(value, object);
+  andl(value, Immediate(0x7));
+  cmpl(value, Immediate(0x4));
   j(NOT_ZERO, no_update, Assembler::kNearJump);
 }
 
@@ -1423,13 +1429,15 @@
   movq(dest, value);
 
   Label done;
+  pushq(value);
   StoreIntoObjectFilter(object, value, &done);
   // A store buffer update is required.
-  pushq(RAX);
+  if (value != RAX) pushq(RAX);
   leaq(RAX, dest);
   call(&StubCode::UpdateStoreBufferLabel());
-  popq(RAX);
+  if (value != RAX) popq(RAX);
   Bind(&done);
+  popq(value);
 }
 
 
@@ -1439,9 +1447,11 @@
   movq(dest, value);
 #if defined(DEBUG)
   Label done;
+  pushq(value);
   StoreIntoObjectFilter(object, value, &done);
   Stop("Store buffer update is required");
   Bind(&done);
+  popq(value);
 #endif  // defined(DEBUG)
   // No store buffer update.
 }