[PATCH] Remove VRPs use of TYPE_MIN/MAX_VALUE

[Eric Botcazou]

> The middle-end treats conversions between integral types that differ
> in TYPE_MIN/MAX_VALUE but not in TYPE_PRECISION or signedness as useless.
> This is inconsistent with VRP extracting range information from such
> types (and it is not clear how NOP conversions behave here anyway).

IIRC we agreed, by the time I fixed the Ada compiler, that the IL shouldn't 
contain types with non-canonical bounds, except for constructs that don't 
generate code like the TYPE_DOMAIN of arrays.  My understanding is that this 
has been the case (modulo bugs) for some time now, so I don't understand your 
remark about NOP conversions.

> The following patch thus simply removes VRPs looking at TYPE_MIN/MAX_VALUE
> in favor of using a canonical min/max value based on signedness and
> precision.  This exposes a latent bug in upper_bound_in_type and
> lower_bound_in_type which do not properly sign-extend sizetype constants.

Wouldn't it be better performance-wise to keep using TYPE_MIN/MAX_VALUE and add 
an appropriate check for non-standard types at the end of gimplification?

-- 
Eric Botcazou