Serializer: attach alignment to deferred objects.

R=jkummerow@chromium.org
BUG=chromium:523919
LOG=N

Review URL: https://codereview.chromium.org/1440983002

Cr-Commit-Position: refs/heads/master@{#31956}

src/snapshot/serialize.cc

@@ -636,6 +636,13 @@ void Deserializer::VisitPointers(Object** start, Object** end) {
 
 void Deserializer::DeserializeDeferredObjects() {
   for (int code = source_.Get(); code != kSynchronize; code = source_.Get()) {
+    switch (code) {
+      case kAlignmentPrefix:
+      case kAlignmentPrefix + 1:
+      case kAlignmentPrefix + 2:
+        SetAlignment(code);
+        break;
+      default: {
         int space = code & kSpaceMask;
         DCHECK(space <= kNumberOfSpaces);
         DCHECK(code - space == kNewObject);
@@ -649,6 +656,8 @@ void Deserializer::DeserializeDeferredObjects() {
         DCHECK(CanBeDeferred(object));
         PostProcessNewObject(object, space);
       }
+    }
+  }
 }
 
 
@@ -1188,12 +1197,9 @@ bool Deserializer::ReadData(Object** current, Object** limit, int source_space,
 
       case kAlignmentPrefix:
       case kAlignmentPrefix + 1:
-      case kAlignmentPrefix + 2: {
-        DCHECK_EQ(kWordAligned, next_alignment_);
-        next_alignment_ =
-            static_cast<AllocationAlignment>(data - (kAlignmentPrefix - 1));
+      case kAlignmentPrefix + 2:
+        SetAlignment(data);
         break;
-      }
 
       STATIC_ASSERT(kNumberOfRootArrayConstants == Heap::kOldSpaceRoots);
       STATIC_ASSERT(kNumberOfRootArrayConstants == 32);
@@ -2057,6 +2063,7 @@ void Serializer::ObjectSerializer::SerializeDeferred() {
   CHECK_EQ(0, bytes_processed_so_far_);
   bytes_processed_so_far_ = kPointerSize;
 
+  serializer_->PutAlignmentPrefix(object_);
   sink_->Put(kNewObject + reference.space(), "deferred object");
   serializer_->PutBackReference(object_, reference);
   sink_->PutInt(size >> kPointerSizeLog2, "deferred object size");

src/snapshot/serialize.h

@@ -403,6 +403,14 @@ class Deserializer: public SerializerDeserializer {
     memcpy(dest, src, sizeof(*src));
   }
 
+  void SetAlignment(byte data) {
+    DCHECK_EQ(kWordAligned, next_alignment_);
+    int alignment = data - (kAlignmentPrefix - 1);
+    DCHECK_LE(kWordAligned, alignment);
+    DCHECK_LE(alignment, kSimd128Unaligned);
+    next_alignment_ = static_cast<AllocationAlignment>(alignment);
+  }
+
   void DeserializeDeferredObjects();
 
   void FlushICacheForNewIsolate();

test/mjsunit/regress/regress-crbug-523919.js

+// Copyright 2015 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.
+
+// Flags: --cache=code
+
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+[2.5,
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+[12.5,
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+[14.5,
+[15.5,
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+[17.5,
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+[23.5,
+[24.5,
+[25.5]]]]]]]]]]]]]]]]]]]]]]]]];