Re: Some thoughts and quetsions about the data flow infrastracture

[Paolo Bonzini]

 I even have own tool for 
this NONA http://cocom.sf.net .  Although it might be a good research to 
make it work on insns from diffrent BBs.

Of course instruction selection is usually done intra-BB.  However, some 
analyses that combine performs, such as nonzero_bits and 
num_sign_bit_copies, maybe could be extended to use the new framework.

The problem is that to use the modern approach you need another 
description of insns (with one pattern - one machine insn relation) in 
tree representation with given cost for the tree.  And it is a huge work 
to rewrite current machine descriptions even only for this.

This is not really necessary.  I have a stripped down version of NONA 
working on RTL.  It is possible to build the tree using a mechanism 
similar to subst in combine, simplify the resulting expression, and use 
NONA (which is actually the same algorithms as iburg) to split it.

Paolo