Some thoughts and quetsions about the data flow infrastracture

Paolo Bonzini paolo.bonzini@lu.unisi.ch
Tue Feb 13 20:02:00 GMT 2007


>  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



More information about the Gcc mailing list