[Bug c++/68023] New: 4.8.4 generates good code where 5.2 generates bad code

["barto at cambridgesemantics dot com" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68023

            Bug ID: 68023
           Summary: 4.8.4 generates good code where 5.2 generates bad code
           Product: gcc
           Version: 5.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: barto at cambridgesemantics dot com
  Target Milestone: ---

Created attachment 36543
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=36543&action=edit
Configuration for GCC 4.8.4

The following code:
template <class T>
 inline
 SPORef<T>::SPORef
  /// Constructor: increment pointed to T's reference count.
  ( T* p                ///< Pointer to the T to be managed
  )
  : rep_(p)
{
  badcode();
  if (rep_)
    rep_->incReferences();
}

template <class T>
 inline
 SPORef<T>::~SPORef
  /// Destructor: decrement pointed to T's reference count, possibly
  /// triggering its destruction.
  ()
{
  badcode();
  if (rep_) {
    rep_->decReferences();
    rep_ = 0;
  }
}

when compiled optimized with GCC 4.8.4 runs properly when compiled -O3.
Changing the compiler (and associated tool chain) from 4.8 to 5.2 causes the
code generated from these functions to cause the system to crash. Changing the
optimization around these 2 methods only by using:

#pragma GCC push_options
#pragma GCC optimize("O0")
<failing code>
#pragma GCC pop_options

and the gcc 5.2 compiler will successfully compile the code.

Attached are the .ii files for 4.8 and 5.2 as well as the configuration files
for 4.8 and 5.2.