Improve write barriers in optimized code.

src/ia32/macro-assembler-ia32.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 "v8.h"
 
 #if V8_TARGET_ARCH_IA32
 
 #include "bootstrapper.h"
 #include "codegen.h"
@@ skipping 419 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,
+    bool value_is_in_new_space) {
   // 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, Label::kNear);
   }
 
   // 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));
 
   lea(dst, FieldOperand(object, offset));
   if (emit_debug_code()) {
     Label ok;
     test_b(dst, (1 << kPointerSizeLog2) - 1);
     j(zero, &ok, Label::kNear);
     int3();
     bind(&ok);
   }
 
   RecordWrite(
-      object, dst, value, save_fp, remembered_set_action, OMIT_SMI_CHECK);
+      object, dst, value, save_fp, remembered_set_action, OMIT_SMI_CHECK,
+      value_is_in_new_space);
 
   bind(&done);
 
   // Clobber clobbered input registers when running with the debug-code flag
   // turned on to provoke errors.
   if (emit_debug_code()) {
     mov(value, Immediate(BitCast<int32_t>(kZapValue)));
     mov(dst, Immediate(BitCast<int32_t>(kZapValue)));
   }
 }
@@ skipping 20 matching lines @@
 
   ASSERT(!object.is(value));
   ASSERT(!object.is(address));
   ASSERT(!value.is(address));
   AssertNotSmi(object);
 
   if (!FLAG_incremental_marking) {
     return;
   }
 
+  // Compute the address.
+  lea(address, 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);
 
   // 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.
   ASSERT(!isolate()->heap()->InNewSpace(*map));
   CheckPageFlagForMap(map,
                       MemoryChunk::kPointersToHereAreInterestingMask,
                       zero,
                       &done,
                       Label::kNear);
 
-  // Delay the initialization of |address| and |value| for the stub until it's
-  // known that the will be needed. Up until this point their values are not
-  // needed since they are embedded in the operands of instructions that need
-  // them.
-  lea(address, FieldOperand(object, HeapObject::kMapOffset));
-  mov(value, Immediate(map));
   RecordWriteStub stub(isolate(), object, value, address, OMIT_REMEMBERED_SET,
                        save_fp);
   CallStub(&stub);
 
   bind(&done);
 
   // Clobber clobbered input registers when running with the debug-code flag
   // turned on to provoke errors.
   if (emit_debug_code()) {
     mov(value, Immediate(BitCast<int32_t>(kZapValue)));
     mov(scratch1, Immediate(BitCast<int32_t>(kZapValue)));
     mov(scratch2, Immediate(BitCast<int32_t>(kZapValue)));
   }
 }
 
 
 void MacroAssembler::RecordWrite(Register object,
                                  Register address,
                                  Register value,
                                  SaveFPRegsMode fp_mode,
                                  RememberedSetAction remembered_set_action,
-                                 SmiCheck smi_check) {
+                                 SmiCheck smi_check,
+                                 bool value_is_in_new_space) {
   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 young gen.
   Label done;
 
   if (smi_check == INLINE_SMI_CHECK) {
     // Skip barrier if writing a smi.
     JumpIfSmi(value, &done, Label::kNear);
   }
 
-  CheckPageFlag(value,
-                value,  // Used as scratch.
-                MemoryChunk::kPointersToHereAreInterestingMask,
-                zero,
-                &done,
-                Label::kNear);
+  if (!value_is_in_new_space) {
+    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);
   CallStub(&stub);
@@ skipping 2841 matching lines @@
   if (ms.shift() > 0) sar(edx, ms.shift());
   mov(eax, dividend);
   shr(eax, 31);
   add(edx, eax);
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_IA32