Re: [ping][PATCH][1 of 2] Add value range info to SSA_NAME for zero sign extension elimination in RTL

[Richard Biener <rguenther@suse.de>]

On Wed, 11 Sep 2013, Kugan wrote:

> Thanks Jakub for the review.
> 
> On 10/09/13 23:10, Jakub Jelinek wrote:
> > On Tue, Sep 10, 2013 at 03:17:50PM +0200, Richard Biener wrote:
> > > > unsigned short s;
> > > > s.1_3 = (short unsigned int) l.0_2;
> > > > l.0_2: VARYING
> > > > s.1_3: [0, +INF]
> > > 
> > > Note that [0, +INF] is the same as VARYING and [-INF, +INF] and VARYING
> > > for
> > > l.0_2 is the same as [-INF, +INF].
> > 
> > Yeah, I don't see much value in differentiating between VR_VARYING and
> > VR_RANGE [TYPE_MIN_VALUE, TYPE_MAX_VALUE] (perhaps a question is what to do
> > for types with precisions different from TYPE_MODE's bitsize, if we should
> > store for VARYING/UNDEFINED a range of all possible values in the mode).
> > Unsigned type will be always >= 0, even if it is VARYING or UNDEFINED.
> > What is the valid bit good for?  Is it meant just for integrals with >
> > 2*HOST_BITS_PER_WIDE_INT precision, which we can't represent in double_int?
> > I'd say we just don't want to keep track on the value ranges for those.
> 
> Ok, I will remove the valid.
> 
> > And, do we need to distinguish between VR_RANGE and VR_ANTI_RANGE?
> > I mean, can't we always store the range in VR_RANGE format?  Instead of
> > -[3,7] we'd store [8,2] and define that if the min double_int is bigger than
> > max double_int, then it is [min,+infinity] merged with [-infinity,max] range
> > (i.e. -[max+1,min-1])?
> > 
> 
> Ok, I will change this too.

Make sure to add a predicate that can tell whether its an anti-range
then.

Richard.