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Re: patch to canonize small wide-ints.


On Tue, 24 Sep 2013, Kenneth Zadeck wrote:

> On 09/24/2013 09:39 AM, Richard Biener wrote:
> > On Tue, 17 Sep 2013, Kenneth Zadeck wrote:
> > 
> > > Richi,
> > > 
> > > This patch canonizes the bits above the precision for wide ints with types
> > > or
> > > modes that are not a perfect multiple of HOST_BITS_PER_WIDE_INT.
> > > 
> > > I expect that most of the changes in rtl.h will go away.   in particular,
> > > when
> > > we decide that we can depend on richard's patch to clean up rtl constants,
> > > then the only thing that will be left will be the addition of the
> > > TARGET_SUPPORTS_WIDE_INT test.
> > > 
> > > I do believe that there is one more conserved force in the universe than
> > > what
> > > physicist's generally consider: it is uglyness.  There is a lot of truth
> > > and
> > > beauty in the patch but in truth there is a lot of places where the
> > > uglyness
> > > is just moved someplace else.
> > > 
> > > in the pushing the ugly around dept, trees and wide-ints are not canonized
> > > the
> > > same way.    I spent several days going down the road where it tried to
> > > have
> > > them be the same, but it got very ugly having 32 bit unsigned int csts
> > > have
> > > the upper 32 bits set.   So now wide_int_to_tree and the wide-int
> > > constructors
> > > from tree-cst are now more complex.
> > > 
> > > i think that i am in favor of this patch, especially in conjunction with
> > > richards cleanup, but only mildly.
> > > 
> > > There is also some cleanup where richard wanted the long lines addressed.
> > > 
> > > Ok to commit to the wide-int branch?
> > Looks good to me.
> > 
> > I'll be doing a separate review of the to/from tree parts when I
> > find time to do that, but that's unrelated to this patch.
> > 
> > Thanks,
> > Richard.
> as i said on irc, after i check in a cleaned up version of this (for ppc) i
> will change the rep for unsiged tree-csts so that they have an extra block of
> zeros if their top bit is set.   this will clean that up somewhat.

Yes, this will give wide-ints a sign (as I originally proposed).  For
RTL constants we're going to "lie" and make all constants negative
that have their MSB set.

Richard.


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