[turbofan] Move {Code} flag setting into allocator.

This makes sure flags on newly allocated {Code} objects are initialized
from within the allocator itself instead of after the object has been
created. It essentially makes these flags immutable.

R=jarin@chromium.org
BUG=v8:6792

Change-Id: I6bef183a25508faf1fec28d347956e766e65aecf
Reviewed-on: https://chromium-review.googlesource.com/737633
Commit-Queue: Michael Starzinger <mstarzinger@chromium.org>
Reviewed-by: Jaroslav Sevcik <jarin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#48933}

src/compiler/code-generator.cc

@@ -304,14 +304,12 @@ Handle<Code> CodeGenerator::FinalizeCode() {
     unwinding_info_writer_.eh_frame_writer()->GetEhFrame(&desc);
   }
 
-  Handle<Code> result =
-      isolate()->factory()->NewCode(desc, info()->code_kind(), Handle<Object>(),
-                                    table, source_positions, deopt_data, false);
+  Handle<Code> result = isolate()->factory()->NewCode(
+      desc, info()->code_kind(), Handle<Object>(), table, source_positions,
+      deopt_data, false, true, frame()->GetTotalFrameSlotCount(),
+      safepoints()->GetCodeOffset());
   isolate()->counters()->total_compiled_code_size()->Increment(
       result->instruction_size());
-  result->set_is_turbofanned(true);
-  result->set_stack_slots(frame()->GetTotalFrameSlotCount());
-  result->set_safepoint_table_offset(safepoints()->GetCodeOffset());
 
   LOG_CODE_EVENT(isolate(),
                  CodeLinePosInfoRecordEvent(*Handle<AbstractCode>::cast(result),

src/factory.cc

@@ -1794,7 +1794,8 @@ Handle<Code> Factory::NewCode(
     const CodeDesc& desc, Code::Kind kind, Handle<Object> self_ref,
     MaybeHandle<HandlerTable> maybe_handler_table,
     MaybeHandle<ByteArray> maybe_source_position_table,
-    MaybeHandle<DeoptimizationData> maybe_deopt_data, bool immovable) {
+    MaybeHandle<DeoptimizationData> maybe_deopt_data, bool immovable,
+    bool is_turbofanned, int stack_slots, int safepoint_table_offset) {
   Handle<ByteArray> reloc_info = NewByteArray(desc.reloc_size, TENURED);
   Handle<CodeDataContainer> data_container = NewCodeDataContainer(0);
 
@@ -1836,7 +1837,9 @@ Handle<Code> Factory::NewCode(
   code->set_relocation_info(*reloc_info);
   code->initialize_flags(kind);
   code->set_has_unwinding_info(has_unwinding_info);
-  code->set_safepoint_table_offset(0);
+  code->set_is_turbofanned(is_turbofanned);
+  code->set_stack_slots(stack_slots);
+  code->set_safepoint_table_offset(safepoint_table_offset);
   code->set_code_data_container(*data_container);
   code->set_has_tagged_params(true);
   code->set_deoptimization_data(*deopt_data);

src/factory.h

@@ -685,7 +685,8 @@ class V8_EXPORT_PRIVATE Factory final {
                            MaybeHandle<ByteArray>(),
                        MaybeHandle<DeoptimizationData> maybe_deopt_data =
                            MaybeHandle<DeoptimizationData>(),
-                       bool immovable = false);
+                       bool immovable = false, bool is_turbofanned = false,
+                       int stack_slots = 0, int safepoint_table_offset = 0);
 
   // Allocates a new, empty code object for use by builtin deserialization. The
   // given {size} argument specifies the size of the entire code object.

src/objects/code-inl.h

@@ -420,7 +420,7 @@ unsigned Code::stack_slots() const {
 
 void Code::set_stack_slots(unsigned slots) {
   CHECK(slots <= StackSlotsField::kMax);
-  DCHECK(is_turbofanned());
+  DCHECK(is_turbofanned() || slots == 0);  // Allow zero initialization.
   int previous = READ_UINT32_FIELD(this, kFlagsOffset);
   int updated = StackSlotsField::update(previous, slots);
   WRITE_UINT32_FIELD(this, kFlagsOffset, updated);