7041789: 30% perf regression with c2/arm following 7017732

Implement a more accurate is_scavengable()

Reviewed-by: stefank, jcoomes, ysr

hotspot/src/share/vm/gc_implementation/parallelScavenge/parallelScavengeHeap.cpp

@@ -339,6 +339,21 @@ bool ParallelScavengeHeap::is_in_reserved(const void* p) const {
   return false;
 }
 
+bool ParallelScavengeHeap::is_scavengable(const void* addr) {
+  return is_in_young((oop)addr);
+}
+
+#ifdef ASSERT
+// Don't implement this by using is_in_young().  This method is used
+// in some cases to check that is_in_young() is correct.
+bool ParallelScavengeHeap::is_in_partial_collection(const void *p) {
+  assert(is_in_reserved(p) || p == NULL,
+    "Does not work if address is non-null and outside of the heap");
+  // The order of the generations is perm (low addr), old, young (high addr)
+  return p >= old_gen()->reserved().end();
+}
+#endif
+
 // There are two levels of allocation policy here.
 //
 // When an allocation request fails, the requesting thread must invoke a VM