Re: [RFC] ipa bitwise constant propagation

[kugan <kugan dot vivekanandarajah at linaro dot org>]

Hi Honza,

On 04/08/16 23:05, Jan Hubicka wrote:
> > I didn't look at the propagation part but eventually the IPA-CP
> > lattice gets quite big.  Also the alignment lattice is very
> > similar to the bits lattice so why not merge those two?  But
>
> This was always the original idea to replace alignment propagation by bitwise
> ccp.  I suppose we only have issue here because nonzero bits are not tracked for
> pointers so we need to feed the original lattices by hand?

I also raised this one with Prathamesh off line. With the early-vrp, we 
should have nonzero_bits for non pointers. For pointers we should feed 
the lattices with get_pointer_alignment_1 as it is done in 
ipa-cpalignment propagation.

> We could also make use of VR ranges and bits while evaultaing predicates
> in ipa-inline-analysis. I can look into it after returning from Leeds.

Indeed. With ealrly dom based VRP (non iterative at this point), some of 
the ranges can be pessimistic and can impact the estimation. Let me have 
a look at this.

Thanks,
Kugan