GCC build failed with your patch on 2001-02-17T20:05:01Z.

[Jeffrey A Law]

  In message < 10102172208.AA10841@vlsi1.ultra.nyu.edu >you write:
  > OK, I see what's wrong.  GCSE will, in some cases, emit an insn without
  > verifying that it's valid.
There is one case.  When cprop can turn a conditional jump into an
unconditional jump, we make the substitution and force a run of
the jump optimizer to clean things up.

That significantly simplifies gcse since if we tried to eliminate a
nop jump we need to rebuild the cfg and recompute all the local
properies, etc in gcse.c

I'd love a way to do that in a cleaner manner.
jeff