[Bug middle-end/51200] New: Wrong code sequence to store restrict volatile bitfield

[joey.ye at arm dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51200

             Bug #: 51200
           Summary: Wrong code sequence to store restrict volatile
                    bitfield
    Classification: Unclassified
           Product: gcc
           Version: 4.7.0
            Status: UNCONFIRMED
          Severity: major
          Priority: P3
         Component: middle-end
        AssignedTo: unassig...@gcc.gnu.org
        ReportedBy: joey...@arm.com


Trunk 179074 generates wrong code sequence with -fstrict-volatile-bitfields on
ARM and x86. 

ARM AAPCS default enable strict volatile bitfields so it is critical on ARM:

/* { dg-do run } */
/* { dg-options "-fstrict-volatile-bitfields" } */

extern void abort(void);
struct thing {
  volatile unsigned short a: 8;
  volatile unsigned short b: 8;
} t = {1,2};

int main()
{
  t.a = 3;
  if (t.a !=3 || t.b !=2) abort();
  return 0;
}