Reland of [heap] Simplify marking of JSFunction and SFI (patchset #1 id:1 of...

Reland of [heap] Simplify marking of JSFunction and SFI (patchset #1 id:1 of https://codereview.chromium.org/2389963007/ )

Reason for revert:
Wrong culprit as this was already broken before.

Original issue's description:
> Revert of [heap] Simplify marking of JSFunction and SFI (patchset #3 id:40001 of https://codereview.chromium.org/2389183002/ )
>
> Reason for revert:
> Broke GCStress.
>
> Original issue's description:
> > [heap] Simplify marking of JSFunction and SFI
> >
> > BUG=chromium:651828
> >
> > Committed: https://crrev.com/4d45ed4597d537cf9624cb6683dc4bd646d11242
> > Cr-Commit-Position: refs/heads/master@{#39975}
>
> TBR=hpayer@chromium.org,mlippautz@chromium.org
> # Skipping CQ checks because original CL landed less than 1 days ago.
> NOPRESUBMIT=true
> NOTREECHECKS=true
> NOTRY=true
> BUG=chromium:651828
>
> Committed: https://crrev.com/5295d7a463cbcc78a4b694a7fb84af8e8e400303
> Cr-Commit-Position: refs/heads/master@{#39983}

TBR=hpayer@chromium.org,epertoso@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=chromium:651828

Review-Url: https://codereview.chromium.org/2390373004
Cr-Commit-Position: refs/heads/master@{#39990}

src/heap/objects-visiting-inl.h

@@ -449,11 +449,11 @@ void StaticMarkingVisitor<StaticVisitor>::VisitSharedFunctionInfo(
       // optimized code.
       collector->code_flusher()->AddCandidate(shared);
       // Treat the reference to the code object weakly.
-      VisitSharedFunctionInfoWeakCode(heap, object);
+      VisitSharedFunctionInfoWeakCode(map, object);
       return;
     }
   }
-  VisitSharedFunctionInfoStrongCode(heap, object);
+  VisitSharedFunctionInfoStrongCode(map, object);
 }
 
 
@@ -621,39 +621,23 @@ bool StaticMarkingVisitor<StaticVisitor>::IsFlushable(
   return true;
 }
 
-
 template <typename StaticVisitor>
 void StaticMarkingVisitor<StaticVisitor>::VisitSharedFunctionInfoStrongCode(
-    Heap* heap, HeapObject* object) {
-  Object** start_slot = HeapObject::RawField(
-      object, SharedFunctionInfo::BodyDescriptor::kStartOffset);
-  Object** end_slot = HeapObject::RawField(
-      object, SharedFunctionInfo::BodyDescriptor::kEndOffset);
-  StaticVisitor::VisitPointers(heap, object, start_slot, end_slot);
+    Map* map, HeapObject* object) {
+  FixedBodyVisitor<StaticVisitor, SharedFunctionInfo::BodyDescriptor,
+                   void>::Visit(map, object);
 }
 
-
 template <typename StaticVisitor>
 void StaticMarkingVisitor<StaticVisitor>::VisitSharedFunctionInfoWeakCode(
-    Heap* heap, HeapObject* object) {
-  Object** name_slot =
-      HeapObject::RawField(object, SharedFunctionInfo::kNameOffset);
-  StaticVisitor::VisitPointer(heap, object, name_slot);
-
+    Map* map, HeapObject* object) {
   // Skip visiting kCodeOffset as it is treated weakly here.
-  STATIC_ASSERT(SharedFunctionInfo::kNameOffset + kPointerSize ==
-                SharedFunctionInfo::kCodeOffset);
-  STATIC_ASSERT(SharedFunctionInfo::kCodeOffset + kPointerSize ==
-                SharedFunctionInfo::kOptimizedCodeMapOffset);
-
-  Object** start_slot =
-      HeapObject::RawField(object, SharedFunctionInfo::kOptimizedCodeMapOffset);
-  Object** end_slot = HeapObject::RawField(
-      object, SharedFunctionInfo::BodyDescriptor::kEndOffset);
-  StaticVisitor::VisitPointers(heap, object, start_slot, end_slot);
+  STATIC_ASSERT(SharedFunctionInfo::kCodeOffset <
+                SharedFunctionInfo::BodyDescriptorWeakCode::kStartOffset);
+  FixedBodyVisitor<StaticVisitor, SharedFunctionInfo::BodyDescriptorWeakCode,
+                   void>::Visit(map, object);
 }
 
-
 template <typename StaticVisitor>
 void StaticMarkingVisitor<StaticVisitor>::VisitJSFunctionStrongCode(
     Map* map, HeapObject* object) {

src/heap/objects-visiting.h

@@ -386,8 +386,8 @@ class StaticMarkingVisitor : public StaticVisitorBase {
 
   // Helpers used by code flushing support that visit pointer fields and treat
   // references to code objects either strongly or weakly.
-  static void VisitSharedFunctionInfoStrongCode(Heap* heap, HeapObject* object);
-  static void VisitSharedFunctionInfoWeakCode(Heap* heap, HeapObject* object);
+  static void VisitSharedFunctionInfoStrongCode(Map* map, HeapObject* object);
+  static void VisitSharedFunctionInfoWeakCode(Map* map, HeapObject* object);
   static void VisitJSFunctionStrongCode(Map* map, HeapObject* object);
   static void VisitJSFunctionWeakCode(Map* map, HeapObject* object);
 

src/objects.h

@@ -7543,9 +7543,9 @@ class SharedFunctionInfo: public HeapObject {
 
   // Layout description.
   // Pointer fields.
-  static const int kNameOffset = HeapObject::kHeaderSize;
-  static const int kCodeOffset = kNameOffset + kPointerSize;
-  static const int kOptimizedCodeMapOffset = kCodeOffset + kPointerSize;
+  static const int kCodeOffset = HeapObject::kHeaderSize;
+  static const int kNameOffset = kCodeOffset + kPointerSize;
+  static const int kOptimizedCodeMapOffset = kNameOffset + kPointerSize;
   static const int kScopeInfoOffset = kOptimizedCodeMapOffset + kPointerSize;
   static const int kOuterScopeInfoOffset = kScopeInfoOffset + kPointerSize;
   static const int kConstructStubOffset = kOuterScopeInfoOffset + kPointerSize;
@@ -7670,9 +7670,12 @@ class SharedFunctionInfo: public HeapObject {
 
   static const int kAlignedSize = POINTER_SIZE_ALIGN(kSize);
 
+  typedef FixedBodyDescriptor<kCodeOffset,
+                              kLastPointerFieldOffset + kPointerSize, kSize>
+      BodyDescriptor;
   typedef FixedBodyDescriptor<kNameOffset,
-                              kLastPointerFieldOffset + kPointerSize,
-                              kSize> BodyDescriptor;
+                              kLastPointerFieldOffset + kPointerSize, kSize>
+      BodyDescriptorWeakCode;
 
   // Bit positions in start_position_and_type.
   // The source code start position is in the 30 most significant bits of