Write barrier for storing a code entry, and usage in CompileLazy builtin.

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.
 
 #if V8_TARGET_ARCH_IA32
 
 #include "src/base/bits.h"
 #include "src/base/division-by-constant.h"
 #include "src/bootstrapper.h"
 #include "src/codegen.h"
@@ skipping 553 matching lines @@
   IncrementCounter(isolate()->counters()->write_barriers_dynamic(), 1);
 
   // Clobber clobbered registers when running with the debug-code flag
   // turned on to provoke errors.
   if (emit_debug_code()) {
     mov(address, Immediate(bit_cast<int32_t>(kZapValue)));
     mov(value, Immediate(bit_cast<int32_t>(kZapValue)));
   }
 }
 
+void MacroAssembler::RecordWriteCodeEntryField(Register js_function,
+                                               Register code_entry,
+                                               Register dst) {

[ulan, 2016/02/01 17:20:49]

Let's keep argument names consistent with the header file (dst -> scratch).

[mvstanton, 2016/02/03 14:23:17]

Done.

+  const int offset = JSFunction::kCodeEntryOffset;
+
+  // Since a code entry (value) is always in old space, we don't need to update
+  // remembered set. If incremental marking is off, there is nothing for us to
+  // do.
+  if (!FLAG_incremental_marking) return;
+
+  lea(dst, FieldOperand(js_function, offset));
+
+  DCHECK(!js_function.is(code_entry));
+  DCHECK(!js_function.is(dst));
+  DCHECK(!code_entry.is(dst));
+  AssertNotSmi(js_function);
+
+  if (emit_debug_code()) {
+    Label ok;
+    cmp(code_entry, Operand(dst, 0));
+    j(equal, &ok, Label::kNear);
+    int3();
+    bind(&ok);
+  }
+
+  // First, check if a write barrier is even needed. The tests below
+  // catch stores of Smis and stores into young gen.
+  Label done;
+
+  CheckPageFlag(code_entry,
+                code_entry,  // Used as scratch.
+                MemoryChunk::kPointersToHereAreInterestingMask, zero, &done,
+                Label::kNear);
+  CheckPageFlag(js_function,
+                code_entry,  // Used as scratch.
+                MemoryChunk::kPointersFromHereAreInterestingMask, zero, &done,
+                Label::kNear);
+
+  // Save input registers.
+  push(js_function);
+  push(code_entry);

[ulan, 2016/02/01 17:20:49]

At this point the code_entry is already clobbered by CheckPageFlag.

[mvstanton, 2016/02/03 14:23:17]

I changed things so that we don't clobber code_entry anymore...it's useful at
the call site.

+
+  // Save caller-saved registers.
+  if (!js_function.is(eax) && !code_entry.is(eax)) push(eax);

[ulan, 2016/02/01 17:20:49]

Since this sequence is now used in two places. Should we extract it into
separate macro asm instructions PushCallerSaved, PopCallerSaved?

[mvstanton, 2016/02/03 14:23:17]

Absolutely, done.

+  if (!js_function.is(ecx) && !code_entry.is(ecx)) push(ecx);
+  if (!js_function.is(edx) && !code_entry.is(edx)) push(edx);
+
+  int argument_count = 3;
+  PrepareCallCFunction(argument_count, code_entry);
+  mov(Operand(esp, 0 * kPointerSize), js_function);
+  mov(Operand(esp, 1 * kPointerSize), dst);  // Slot.
+  mov(Operand(esp, 2 * kPointerSize),
+      Immediate(ExternalReference::isolate_address(isolate())));
+
+  {
+    AllowExternalCallThatCantCauseGC scope(this);
+    CallCFunction(
+        ExternalReference::incremental_marking_record_write_code_entry_function(
+            isolate()),
+        argument_count);
+  }
+
+  // Restore caller-saved registers.
+  if (!js_function.is(edx) && !code_entry.is(edx)) pop(edx);
+  if (!js_function.is(ecx) && !code_entry.is(ecx)) pop(ecx);
+  if (!js_function.is(eax) && !code_entry.is(eax)) pop(eax);
+
+  // Restore input registers.
+  pop(code_entry);
+  pop(js_function);
+
+  bind(&done);
+}
 
 void MacroAssembler::DebugBreak() {
   Move(eax, Immediate(0));
   mov(ebx, Immediate(ExternalReference(Runtime::kHandleDebuggerStatement,
                                        isolate())));
   CEntryStub ces(isolate(), 1);
   call(ces.GetCode(), RelocInfo::DEBUGGER_STATEMENT);
 }
 
 
@@ skipping 2520 matching lines @@
   mov(eax, dividend);
   shr(eax, 31);
   add(edx, eax);
 }
 
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_IA32