[Bug debug/53948] New: [4.8 Regression] Assignment line missing for -O0 -g

["jan.kratochvil at redhat dot com" <gcc-bugzilla@gcc.gnu.org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53948

             Bug #: 53948
           Summary: [4.8 Regression] Assignment line missing for -O0 -g
    Classification: Unclassified
           Product: gcc
           Version: 4.8.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: debug
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: jan.kratochvil@redhat.com
                CC: aoliva@gcc.gnu.org
            Target: x86_64-unknown-linux-gnu


Nothing serious but it broke gdb.base/store.exp and I believe -O0 -g should not
"optimize out" source statements.

int f (register int a, register int b) {
  register int x = b, y = a;
  return x + y; }
gcc -g

PASS: gcc (GCC) 4.7.2 20120713 (prerelease)
   7:    89 f8                    mov    %edi,%eax
   9:    89 f2                    mov    %esi,%edx
  register int x = b, y = a;
   b:    41 89 d4                 mov    %edx,%r12d
   e:    89 c3                    mov    %eax,%ebx
  return x + y; }
  10:    41 8d 04 1c              lea    (%r12,%rbx,1),%eax

FAIL: gcc (GCC) 4.8.0 20120713 (experimental)
   7:    89 fb                    mov    %edi,%ebx
   9:    41 89 f4                 mov    %esi,%r12d
  register int x = b, y = a;
  return x + y; }
   c:    41 8d 04 1c              lea    (%r12,%rbx,1),%eax

GDB no longer stops on the 'register int x = b, y = a;' line during 'step'.
.debug_info is correct in both cases.

I can update the GDB testsuite but still I believe 'int var = val;' source line
should have its instruction during -O0 -g, even if it is just a 'nop'.