Re: Stickiness of TYPE_MIN_VALUE/TYPE_MAX_VALUE

[Diego Novillo <dnovillo at redhat dot com>]

On Mon, May 30, 2005 at 09:59:12PM +0200, Florian Weimer wrote:
> How sticky are TYPE_MIN_VALUE and TYPE_MAX_VALUE?  Is it possible to
> get rid of their effect using a NOP_EXPR, CONVERT_EXPR or
> VIEW_CONVERT_EXPR?
> 
> If this is impossible, the Ada front end should probably stop setting
> these fields because it assumes that it can use values outside that
> range:
> 
> <http://gcc.gnu.org/onlinedocs/gcc-4.0.0/gnat_ugn_unw/Validity-Checking.html>
> 
> Current mainline does not optimize array range checks away (even with
> -ftree-vrp), but I'm not sure if this is just a missed optimization
> opportunity as far as the optimizers are concerned, or something which
> is guaranteed to work in the future.
>
Missed on purpose because of the bootstrap bug I worked-around a
few weeks ago.  See the comment in tree-vrp.c:extract_range_from_assert
regarding integral types with super-types.

http://gcc.gnu.org/ml/gcc-patches/2005-05/msg00127.html

If this is not what's biting you, send me a test case?  I've got
some local VRP changes that address a few of the limitations of
the existing implementation.


Diego.