combiner bug and fix

[Richard Kenner]

    #1  0x08379f8f in gen_binary (code=EQ, mode=VOIDmode, op0=0x4012a538, 
        op1=0x4012a540) at ../../cvs/gcc/gcc/combine.c:10193

I'd recommend doing the fix here and having it say very early:

	if (GET_CODE (op0) == CLOBBER)
	  return op0;
        else if (GET_CODE (op1) == CLOBBER)
	  return op1;