Improve write barriers in optimized code.

src/x64/macro-assembler-x64.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/v8.h"
 
 #if V8_TARGET_ARCH_X64
 
 #include "src/bootstrapper.h"
 #include "src/codegen.h"
@@ skipping 274 matching lines @@
 }
 
 
 void MacroAssembler::RecordWriteField(
     Register object,
     int offset,
     Register value,
     Register dst,
     SaveFPRegsMode save_fp,
     RememberedSetAction remembered_set_action,
-    SmiCheck smi_check) {
+    SmiCheck smi_check,
+    PointersToHereCheck pointers_to_here_check_for_value) {
   // First, check if a write barrier is even needed. The tests below
   // catch stores of Smis.
   Label done;
 
   // Skip barrier if writing a smi.
   if (smi_check == INLINE_SMI_CHECK) {
     JumpIfSmi(value, &done);
   }
 
   // Although the object register is tagged, the offset is relative to the start
   // of the object, so so offset must be a multiple of kPointerSize.
   ASSERT(IsAligned(offset, kPointerSize));
 
   leap(dst, FieldOperand(object, offset));
   if (emit_debug_code()) {
     Label ok;
     testb(dst, Immediate((1 << kPointerSizeLog2) - 1));
     j(zero, &ok, Label::kNear);
     int3();
     bind(&ok);
   }
 
-  RecordWrite(
-      object, dst, value, save_fp, remembered_set_action, OMIT_SMI_CHECK);
+  RecordWrite(object, dst, value, save_fp, remembered_set_action,
+              OMIT_SMI_CHECK, pointers_to_here_check_for_value);
 
   bind(&done);
 
   // Clobber clobbered input registers when running with the debug-code flag
   // turned on to provoke errors.
   if (emit_debug_code()) {
     Move(value, kZapValue, Assembler::RelocInfoNone());
     Move(dst, kZapValue, Assembler::RelocInfoNone());
   }
 }
 
 
-void MacroAssembler::RecordWriteArray(Register object,
-                                      Register value,
-                                      Register index,
-                                      SaveFPRegsMode save_fp,
-                                      RememberedSetAction remembered_set_action,
-                                      SmiCheck smi_check) {
+void MacroAssembler::RecordWriteArray(
+    Register object,
+    Register value,
+    Register index,
+    SaveFPRegsMode save_fp,
+    RememberedSetAction remembered_set_action,
+    SmiCheck smi_check,
+    PointersToHereCheck pointers_to_here_check_for_value) {
   // First, check if a write barrier is even needed. The tests below
   // catch stores of Smis.
   Label done;
 
   // Skip barrier if writing a smi.
   if (smi_check == INLINE_SMI_CHECK) {
     JumpIfSmi(value, &done);
   }
 
   // Array access: calculate the destination address. Index is not a smi.
   Register dst = index;
   leap(dst, Operand(object, index, times_pointer_size,
                    FixedArray::kHeaderSize - kHeapObjectTag));
 
-  RecordWrite(
-      object, dst, value, save_fp, remembered_set_action, OMIT_SMI_CHECK);
+  RecordWrite(object, dst, value, save_fp, remembered_set_action,
+              OMIT_SMI_CHECK, pointers_to_here_check_for_value);
 
   bind(&done);
 
   // Clobber clobbered input registers when running with the debug-code flag
   // turned on to provoke errors.
   if (emit_debug_code()) {
     Move(value, kZapValue, Assembler::RelocInfoNone());
     Move(index, kZapValue, Assembler::RelocInfoNone());
   }
 }
 
 
-void MacroAssembler::RecordWrite(Register object,
-                                 Register address,
-                                 Register value,
-                                 SaveFPRegsMode fp_mode,
-                                 RememberedSetAction remembered_set_action,
-                                 SmiCheck smi_check) {
+void MacroAssembler::RecordWriteForMap(Register object,
+                                       Register map,
+                                       Register dst,
+                                       SaveFPRegsMode fp_mode) {
+  ASSERT(!object.is(kScratchRegister));
+  ASSERT(!object.is(map));
+  ASSERT(!object.is(dst));
+  ASSERT(!map.is(dst));
+  AssertNotSmi(object);
+
+  if (emit_debug_code()) {
+    Label ok;
+    if (map.is(kScratchRegister)) pushq(map);
+    CompareMap(map, isolate()->factory()->meta_map());
+    if (map.is(kScratchRegister)) popq(map);
+    j(equal, &ok, Label::kNear);
+    int3();
+    bind(&ok);
+  }
+
+  if (!FLAG_incremental_marking) {
+    return;
+  }
+
+  if (emit_debug_code()) {
+    Label ok;
+    if (map.is(kScratchRegister)) pushq(map);
+    cmpp(map, FieldOperand(object, HeapObject::kMapOffset));
+    if (map.is(kScratchRegister)) popq(map);
+    j(equal, &ok, Label::kNear);
+    int3();
+    bind(&ok);
+  }
+
+  // Compute the address.
+  leap(dst, FieldOperand(object, HeapObject::kMapOffset));
+
+  // Count number of write barriers in generated code.
+  isolate()->counters()->write_barriers_static()->Increment();
+  IncrementCounter(isolate()->counters()->write_barriers_dynamic(), 1);
+
+  // First, check if a write barrier is even needed. The tests below
+  // catch stores of smis and stores into the young generation.
+  Label done;
+
+  // A single check of the map's pages interesting flag suffices, since it is
+  // only set during incremental collection, and then it's also guaranteed that
+  // the from object's page's interesting flag is also set.  This optimization
+  // relies on the fact that maps can never be in new space.
+  CheckPageFlag(map,
+                map,  // Used as scratch.
+                MemoryChunk::kPointersToHereAreInterestingMask,
+                zero,
+                &done,
+                Label::kNear);
+
+  RecordWriteStub stub(isolate(), object, map, dst, OMIT_REMEMBERED_SET,
+                       fp_mode);
+  CallStub(&stub);
+
+  bind(&done);
+
+  // Clobber clobbered registers when running with the debug-code flag
+  // turned on to provoke errors.
+  if (emit_debug_code()) {
+    Move(dst, kZapValue, Assembler::RelocInfoNone());
+    Move(map, kZapValue, Assembler::RelocInfoNone());
+  }
+}
+
+
+void MacroAssembler::RecordWrite(
+    Register object,
+    Register address,
+    Register value,
+    SaveFPRegsMode fp_mode,
+    RememberedSetAction remembered_set_action,
+    SmiCheck smi_check,
+    PointersToHereCheck pointers_to_here_check_for_value) {
   ASSERT(!object.is(value));
   ASSERT(!object.is(address));
   ASSERT(!value.is(address));
   AssertNotSmi(object);
 
   if (remembered_set_action == OMIT_REMEMBERED_SET &&
       !FLAG_incremental_marking) {
     return;
   }
 
@@ skipping 11 matching lines @@
 
   // First, check if a write barrier is even needed. The tests below
   // catch stores of smis and stores into the young generation.
   Label done;
 
   if (smi_check == INLINE_SMI_CHECK) {
     // Skip barrier if writing a smi.
     JumpIfSmi(value, &done);
   }
 
-  CheckPageFlag(value,
-                value,  // Used as scratch.
-                MemoryChunk::kPointersToHereAreInterestingMask,
-                zero,
-                &done,
-                Label::kNear);
+  if (pointers_to_here_check_for_value != kPointersToHereAreAlwaysInteresting) {
+    CheckPageFlag(value,
+                  value,  // Used as scratch.
+                  MemoryChunk::kPointersToHereAreInterestingMask,
+                  zero,
+                  &done,
+                  Label::kNear);
+  }
 
   CheckPageFlag(object,
                 value,  // Used as scratch.
                 MemoryChunk::kPointersFromHereAreInterestingMask,
                 zero,
                 &done,
                 Label::kNear);
 
   RecordWriteStub stub(isolate(), object, value, address, remembered_set_action,
                        fp_mode);
@@ skipping 4758 matching lines @@
   if (ms.shift() > 0) sarl(rdx, Immediate(ms.shift()));
   movl(rax, dividend);
   shrl(rax, Immediate(31));
   addl(rdx, rax);
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64