two dfa problems

[David S. Miller]

   From: Richard Henderson <rth@redhat.com>
   Date: Fri, 3 May 2002 15:39:52 -0700
   
       While compiling (iirc) iqtest_, we have 18 instructions ready at
       the beginning of the block, which as far as I can see causes us
       to try 2**18 alternatives.  Certainly the compiler hangs for 
       longer than I cared to wait.
   
       I think the algorithm here is wrong, but I don't know how to fix
       it exactly.  The hack attached prevents the exponential runaway,
       but I think we should not be trying alternatives with instructions
       of the same type.  That is, once we've tried an instruction of 
       type TYPE_IADD at position 0, we should not try a different insn
       of type TYPE_IADD there, since it won't help produce a better
       sloting.

Your analysis is right... but what the heck are you setting
DFA lookahead to on Alpha? :-)