patch: alpha haifa abort

[Jeffrey A Law]

  In message < 9801042320.AA31188@rios1.watson.ibm.com >you write:
  > years.  Michael Tiemann and I discussed this many years ago, but GCC
  > combine pass does not see enough RTL patterns at one time.
Note that it is possible to get combine to look at more than 3
instructions.

The "trick" is to define an intermediate pattern so that combine
will do a 2/3 -> 1 to create the intermediate pattern.  If that
is successful combine will then try to combine the intermediate
pattern with the 4th insn.

The first example that comes to mind would be "mac" support on
the H8 series.  Another would be combiner patterns to improve
array/pointer access on the mn10200.

It's non-trivial, but possible to write C code to use "mac" on
the H8/S to see the example "in action".



jeff