[Bug rtl-optimization/66626] [4.9/5/6 Regression] gcc.dg/torture/stackalign/non-local-goto-5.c segfaults w/ -mregparm=3

[hjl.tools at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66626

--- Comment #12 from H.J. Lu <hjl.tools at gmail dot com> ---
lra-eliminations.c has

       {
          /* See if this is setting the replacement hard register for
             an elimination.

             If DEST is the hard frame pointer, we do nothing because
             we assume that all assignments to the frame pointer are
             for non-local gotos and are being done at a time when
             they are valid and do not disturb anything else.  Some
             machines want to eliminate a fake argument pointer (or
             even a fake frame pointer) with either the real frame
             pointer or the stack pointer.  Assignments to the hard
             frame pointer must not prevent this elimination.  */
          for (ep = reg_eliminate;
               ep < &reg_eliminate[NUM_ELIMINABLE_REGS];
               ep++)
            if (ep->to_rtx == SET_DEST (x)
                && SET_DEST (x) != hard_frame_pointer_rtx)
              setup_can_eliminate (ep, false);
        }

It explicitly allows elimination with the hard frame pointer even when
it is used by non-local gotos.