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

[Jakub Jelinek <jakub@redhat.com>]

On Mon, Apr 04, 2016 at 03:27:23PM +0200, Richard Biener wrote:
> 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);

So perhaps either validate_subreg should check the same thing, or
the extraction could check this.
Anyway, I don't have anything against removing that hunk from
extract_bit_field_1 for GCC7.

	Jakub