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Re: VRP: abstract out wide int CONVERT_EXPR_P code




On 08/28/2018 05:27 AM, Richard Biener wrote:
On Mon, Aug 27, 2018 at 2:24 PM Aldy Hernandez <aldyh@redhat.com> wrote:

Howdy!

Phew, I think this is the last abstraction.  This handles the unary
CONVERT_EXPR_P code.

It's the usual story-- normalize the symbolics to [-MIN,+MAX] and handle
everything generically.

Normalizing the symbolics brought about some nice surprises.  We now
handle a few things we were punting on before, which I've documented in
the patch, but can remove if so desired.  I wrote them mainly for myself:

/* NOTES: Previously we were returning VARYING for all symbolics, but
     we can do better by treating them as [-MIN, +MAX].  For
     example, converting [SYM, SYM] from INT to LONG UNSIGNED,
     we can return: ~[0x8000000, 0xffffffff7fffffff].

     We were also failing to convert ~[0,0] from char* to unsigned,
     instead choosing to return VR_VARYING.  Now we return ~[0,0].  */

Tested on x86-64 by the usual bootstrap and regtest gymnastics,
including --enable-languages=all, because my past sins are still
haunting me.

OK?

The new wide_int_range_convert_tree looks odd given it returns
tree's.  I'd have expected an API that does the conversion resulting
in a wide_int range and the VRP code adapting to that by converting
the result to trees.

Hmmm, yeah. I agree. I'll think about this some more and see what I can come up with.

Thanks.
Aldy


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