Reload bug

[Andreas Schwab <schwab@suse.de>]

The following function generates a compiler crash in final:

$ cat random.c
unsigned int GetRandom (void);

long long
Default_RandInt (long long Max)
{
  long long f, m, r, a, b;
  long long s;

  do
    {
      m = Max;
      s = 0;
      f = 1;
      while (m > 1)
	{
	  if (m >= 4294967296)
	    r = GetRandom ();
	  else
	    {
	      a = 4294967296 - 4294967296 % m;
	      do
		b = GetRandom ();
	      while (!(b < a));
	      r = b % m;
	    }
	  s += r * f;
	  f = f * 4294967296;
	  m = (m - 1) / 4294967296 + 1;
	}
    }
  while (!(s < Max || Max == 0));

  return s;
}
$ b=/cvs/test/i686-linux/egcs/gcc; $b/xgcc -B$b/ -O2 -fpic -S random.c -da
random.c: In function `Default_RandInt':
random.c:34: Internal compiler error in `change_address', at emit-rtl.c:1516
Please submit a full bug report.
See <URL: http://www.gnu.org/software/gcc/faq.html#bugreport > for instructions.

The problem is in the following two insns:

(insn 256 254 10 (set (reg:DI 31)
        (mem/u:DI (plus:SI (reg:SI 3 %ebx)
                (const (unspec[ 
                            (symbol_ref/u:SI ("*.LC0"))
                        ]  7))) 0)) 79 {movdi+1} (nil)
    (expr_list:REG_EQUIV (const_double (mem/u:DI (symbol_ref/u:SI ("*.LC0")) 0) 0 [0x0] 1 [0x1] 0 [0x0])
        (nil)))

(insn 83 77 85 (parallel[ 
            (set (reg/v:DI 26)
                (minus:DI (reg:DI 31)
                    (reg:DI 38)))
            (clobber (scratch:SI))
        ] ) 215 {subdi3} (insn_list 77 (nil))
    (expr_list:REG_DEAD (reg:DI 38)
        (expr_list:REG_UNUSED (scratch:SI)
            (nil))))

During global alloc register 31 is replaced by (mem:DI (symbol_ref)), but
a symbol_ref is not a valid memory operand due to PIC.  In other words,
register 31 is _not_ equivalent to what insn 256 claims.

-- 
Andreas Schwab                                  "And now for something
schwab@suse.de                                   completely different."
SuSE GmbH, Schanzäckerstr. 10, D-90443 Nürnberg