MIPS: Improve write barriers in optimized code.

src/mips/macro-assembler-mips.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 <limits.h>  // For LONG_MIN, LONG_MAX.
 
 #include "src/v8.h"
 
 #if V8_TARGET_ARCH_MIPS
 
@@ skipping 176 matching lines @@
 
 
 void MacroAssembler::RecordWriteField(
     Register object,
     int offset,
     Register value,
     Register dst,
     RAStatus ra_status,
     SaveFPRegsMode save_fp,
     RememberedSetAction remembered_set_action,
-    SmiCheck smi_check) {
+    SmiCheck smi_check,
+    PointersToHereCheck pointers_to_here_check_for_value) {
   ASSERT(!AreAliased(value, dst, t8, object));
   // 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));
 
   Addu(dst, object, Operand(offset - kHeapObjectTag));
   if (emit_debug_code()) {
     Label ok;
     And(t8, dst, Operand((1 << kPointerSizeLog2) - 1));
     Branch(&ok, eq, t8, Operand(zero_reg));
     stop("Unaligned cell in write barrier");
     bind(&ok);
   }
 
   RecordWrite(object,
               dst,
               value,
               ra_status,
               save_fp,
               remembered_set_action,
-              OMIT_SMI_CHECK);
+              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()) {
     li(value, Operand(BitCast<int32_t>(kZapValue + 4)));
     li(dst, Operand(BitCast<int32_t>(kZapValue + 8)));
   }
 }
 
 
+// Will clobber 4 registers: object, map, dst, ip.  The
+// register 'object' contains a heap object pointer.
+void MacroAssembler::RecordWriteForMap(Register object,
+                                       Register map,
+                                       Register dst,
+                                       RAStatus ra_status,
+                                       SaveFPRegsMode fp_mode) {
+  if (emit_debug_code()) {
+    ASSERT(!dst.is(at));
+    lw(dst, FieldMemOperand(map, HeapObject::kMapOffset));
+    Check(eq,
+          kWrongAddressOrValuePassedToRecordWrite,
+          dst,
+          Operand(isolate()->factory()->meta_map()));
+  }
+
+  if (!FLAG_incremental_marking) {
+    return;
+  }
+
+  // Count number of write barriers in generated code.
+  isolate()->counters()->write_barriers_static()->Increment();
+  // TODO(mstarzinger): Dynamic counter missing.
+
+  if (emit_debug_code()) {
+    lw(at, FieldMemOperand(object, HeapObject::kMapOffset));
+    Check(eq,
+          kWrongAddressOrValuePassedToRecordWrite,
+          map,
+          Operand(at));
+  }
+
+  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,
+                eq,
+                &done);
+
+  Addu(dst, object, Operand(HeapObject::kMapOffset - kHeapObjectTag));
+  if (emit_debug_code()) {
+    Label ok;
+    And(at, dst, Operand((1 << kPointerSizeLog2) - 1));
+    Branch(&ok, eq, at, Operand(zero_reg));
+    stop("Unaligned cell in write barrier");
+    bind(&ok);
+  }
+
+  // Record the actual write.
+  if (ra_status == kRAHasNotBeenSaved) {
+    push(ra);
+  }
+  RecordWriteStub stub(isolate(), object, map, dst, OMIT_REMEMBERED_SET,
+                       fp_mode);
+  CallStub(&stub);
+  if (ra_status == kRAHasNotBeenSaved) {
+    pop(ra);
+  }
+
+  bind(&done);
+
+  // Clobber clobbered registers when running with the debug-code flag
+  // turned on to provoke errors.
+  if (emit_debug_code()) {
+    li(dst, Operand(BitCast<int32_t>(kZapValue + 12)));
+    li(map, Operand(BitCast<int32_t>(kZapValue + 16)));
+  }
+}
+
+
 // Will clobber 4 registers: object, address, scratch, ip.  The
 // register 'object' contains a heap object pointer.  The heap object
 // tag is shifted away.
-void MacroAssembler::RecordWrite(Register object,
-                                 Register address,
-                                 Register value,
-                                 RAStatus ra_status,
-                                 SaveFPRegsMode fp_mode,
-                                 RememberedSetAction remembered_set_action,
-                                 SmiCheck smi_check) {
+void MacroAssembler::RecordWrite(
+    Register object,
+    Register address,
+    Register value,
+    RAStatus ra_status,
+    SaveFPRegsMode fp_mode,
+    RememberedSetAction remembered_set_action,
+    SmiCheck smi_check,
+    PointersToHereCheck pointers_to_here_check_for_value) {
   ASSERT(!AreAliased(object, address, value, t8));
   ASSERT(!AreAliased(object, address, value, t9));
 
   if (emit_debug_code()) {
     lw(at, MemOperand(address));
     Assert(
         eq, kWrongAddressOrValuePassedToRecordWrite, at, Operand(value));
   }
 
+  if (remembered_set_action == OMIT_REMEMBERED_SET &&
+      !FLAG_incremental_marking) {
+    return;
+  }
+
   // Count number of write barriers in generated code.
   isolate()->counters()->write_barriers_static()->Increment();
   // TODO(mstarzinger): Dynamic counter missing.
 
   // 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) {
     ASSERT_EQ(0, kSmiTag);
     JumpIfSmi(value, &done);
   }
 
-  CheckPageFlag(value,
-                value,  // Used as scratch.
-                MemoryChunk::kPointersToHereAreInterestingMask,
-                eq,
-                &done);
+  if (pointers_to_here_check_for_value != kPointersToHereAreAlwaysInteresting) {
+    CheckPageFlag(value,
+                  value,  // Used as scratch.
+                  MemoryChunk::kPointersToHereAreInterestingMask,
+                  eq,
+                  &done);
+  }
   CheckPageFlag(object,
                 value,  // Used as scratch.
                 MemoryChunk::kPointersFromHereAreInterestingMask,
                 eq,
                 &done);
 
   // Record the actual write.
   if (ra_status == kRAHasNotBeenSaved) {
     push(ra);
   }
@@ skipping 5383 matching lines @@
   }
   if (ms.shift() > 0) sra(result, result, ms.shift());
   srl(at, dividend, 31);
   Addu(result, result, Operand(at));
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_MIPS