[PATCH][GCC 7] Remove broken path in extract_bit_field_1

[Richard Biener]

On Mon, 4 Apr 2016, Jakub Jelinek wrote:

> On Mon, Apr 04, 2016 at 03:10:34PM +0200, Richard Biener wrote:
> > On Mon, 4 Apr 2016, Jakub Jelinek wrote:
> > 
> > > On Mon, Apr 04, 2016 at 02:56:51PM +0200, Richard Biener wrote:
> > > > The testcase gcc.target/i386/pr37870.c will already ICE with that
> > > > patch, so no additional testcase.
> > > 
> > > In theory you could validate_subreg first and use that code if validation
> > > went ok, otherwise go through memory.
> > > But I admit I don't have anything in particular in mind where it would
> > > trigger this code and the subreg would successfully validate.
> > 
> > Not sure if it would help as that has
> > 
> >   /* ??? Similarly, e.g. with (subreg:DF (reg:TI)).  Though 
> > store_bit_field
> >      is the culprit here, and not the backends.  */
> >   else if (osize >= UNITS_PER_WORD && isize >= osize)
> >     ;
> > 
> > and thus we'd return true anyway for (subreg:XF (reg:TI) 0)
> 
> If XFmode subreg of TImode reg passes validation, where does it ICE then?

It ICEs in

/space/rguenther/src/svn/trunk/gcc/testsuite/gcc.target/i386/pr37870.c:19:1: 
internal compiler error: in subreg_get_info, at rtlanal.c:3695
0xddee5a subreg_get_info(unsigned int, machine_mode, unsigned int, 
machine_mode, subreg_info*)
        /space/rguenther/src/svn/trunk/gcc/rtlanal.c:3695
0xddf12b simplify_subreg_regno(unsigned int, machine_mode, unsigned int, 
machine_mode)
        /space/rguenther/src/svn/trunk/gcc/rtlanal.c:3808
0xd8bc7a simplifiable_subregs(subreg_shape const&)
        /space/rguenther/src/svn/trunk/gcc/reginfo.c:1234
0xd8be1d record_subregs_of_mode
        /space/rguenther/src/svn/trunk/gcc/reginfo.c:1294
0xd8c246 init_subregs_of_mode()
        /space/rguenther/src/svn/trunk/gcc/reginfo.c:1348
0xc1a55c init_costs
        /space/rguenther/src/svn/trunk/gcc/ira-costs.c:2187

which is

  /* This should always pass, otherwise we don't know how to verify
     the constraint.  These conditions may be relaxed but
     subreg_regno_offset would need to be redesigned.  */
  gcc_assert ((GET_MODE_SIZE (xmode) % GET_MODE_SIZE (ymode)) == 0);

Richard.