new g77 x86 ICE in 19990328

[Jeffrey A Law]

  In message <19990328181544.10702.qmail@deer>you write:
  > This is a new ICE -- no ICE in previous snapshots.  Could someone
  > currently working on the x86 backend look into it, and let me know
  > if it turns out to be a g77 front-end bug, e.g. a latent one uncovered
  > by recent improvements to the x86?
  > 
  > --------
  > [craig@deer play]$ /develop/egcs/19990328/bin/g77 -O2 -v -c ice.f 
  > g77 version egcs-2.93.14 19990328 (gcc2 ss-980929 experimental) (from FSF-g
  > 77 version 0.5.24-19990313)
  > Reading specs from /develop/egcs/19990328/lib/gcc-lib/i686-pc-linux-gnu/egc
  > s-2.93.14/specs
  > gcc version egcs-2.93.14 19990328 (gcc2 ss-980929 experimental)
  >  /develop/egcs/19990328/lib/gcc-lib/i686-pc-linux-gnu/egcs-2.93.14/f771 ice
  > .f -quiet -dumpbase ice.f -O2 -version -fversion -o /tmp/ccsUcaaa.s
  > GNU F77 version egcs-2.93.14 19990328 (gcc2 ss-980929 experimental) (i686-p
  > c-linux-gnu) compiled by GNU C version egcs-2.93.14 19990328 (gcc2 ss-98092
  > 9 experimental).
  > GNU Fortran Front End version 0.5.24-19990313
  > ../../egcs-19990328/gcc/config/i386/i386.c:3697: Internal compiler error in
  >  function print_operand
  > Please submit a full bug report to `egcs-bugs@egcs.cygnus.com'.
  > See <URL: http://egcs.cygnus.com/faq.html#bugreport > for details.
  > [craig@deer play]$
Got it.  It's an obscure latent bug.

I'll buy a beer at LinuxExpo for the first person that can spot the problem in
this code from emit-rtl.c::operand_subword.  You've got until I get back from
skiing tomorrow afternoon :-)

  /* If OP is a REG or SUBREG, we can handle it very simply.  */
  if (GET_CODE (op) == REG)
    {
      /* If the register is not valid for MODE, return 0.  If we don't
         do this, there is no way to fix up the resulting REG later.  */
      if (REGNO (op) < FIRST_PSEUDO_REGISTER
          && ! HARD_REGNO_MODE_OK (REGNO (op) + i, word_mode))
        return 0;
      else if (REGNO (op) >= FIRST_PSEUDO_REGISTER
               || (REG_FUNCTION_VALUE_P (op)
                   && rtx_equal_function_value_matters)
               /* We want to keep the stack, frame, and arg pointers
                  special.  */
               || op == frame_pointer_rtx
#if FRAME_POINTER_REGNUM != ARG_POINTER_REGNUM
               || op == arg_pointer_rtx
#endif
               || op == stack_pointer_rtx)
        return gen_rtx_SUBREG (word_mode, op, i);
      else
        return gen_rtx_REG (word_mode, REGNO (op) + i);
    }


A hint, OP is the last register in the FP stack register class on the x86.

jeff