RFR: [backport] overflow integer during size calculation

[Roman Kennke]

Applied cleanly, except for usual source path changes.

Ok?

# HG changeset patch
# User zgu
# Date 1529419060 14400
#      Tue Jun 19 10:37:40 2018 -0400
# Node ID eef4ccd8af8b7062c40f0d5415a60d4256dbb68e
# Parent  5945161251d848a91a3cba7241600e959f92cd77
[backport] overflow integer during size calculation

diff --git
a/src/share/vm/gc_implementation/shenandoah/shenandoahConcurrentMark.inline.hpp
b/src/share/vm/gc_implementation/shenandoah/shenandoahConcurrentMark.inline.hpp
---
a/src/share/vm/gc_implementation/shenandoah/shenandoahConcurrentMark.inline.hpp
+++
b/src/share/vm/gc_implementation/shenandoah/shenandoahConcurrentMark.inline.hpp
@@ -95,10 +95,12 @@
 inline void ShenandoahConcurrentMark::count_liveness_humongous(oop obj) {
   shenandoah_assert_in_correct_region(NULL, obj);
   size_t region_idx = _heap->heap_region_index_containing(obj);
-  int size = obj->size() + BrooksPointer::word_size();
+  size_t size = obj->size() + BrooksPointer::word_size();
   size_t num_regions = ShenandoahHeapRegion::required_regions(size *
HeapWordSize);
+
   for (size_t i = region_idx; i < region_idx + num_regions; i++) {
     ShenandoahHeapRegion* chain_reg = _heap->get_region(i);
+    assert(chain_reg->is_humongous(), "Expecting a humongous region");
     chain_reg->increase_live_data_gc_words(chain_reg->used() >>
LogHeapWordSize);
   }
 }