Re: [PATCH] range-op-float: Fix up -ffinite-math-only range extension and don't extend into infinities [PR109008]

[Aldy Hernandez <aldyh@redhat.com>]

On 3/21/23 14:39, Jakub Jelinek wrote:
> On Tue, Mar 21, 2023 at 02:28:31PM +0100, Aldy Hernandez wrote:
>>>    /* Temporarily disable -ffinite-math-only, so that frange::set doesn't
>>>       reduce the range back to real_min_representable (type) as lower bound
>>>       or real_max_representable (type) as upper bound.  */
>>>    bool save_flag_finite_math_only = flag_finite_math_only;
>>>    flag_finite_math_only = false;
>>>    ret.set (type, lb, ub);
>>>    if (lhs.kind () != VR_VARYING)
>>>      {
>>>        ret.clear_nan ();
>>>        ret.union_ (lhs);
>>>      }
>>>    flag_finite_math_only = save_flag_finite_math_only;
>>
>> It looks like what you want to do is be able to create a range with a known
>> NAN state, but without the setter reducing the range to
>> min/max_representable.
>>
>> How about we enhance the API to provide:
>>
>> 1. Constructor with a known NAN state.
>> 2. Setter with a flag to keep it from canonicalizing into
>> min/max_representable.
>>
>> The flag in 2 could in the future be saved in the frange object to keep
>> union and friends from further canonicalization.
>>
>> So the above could be written as:
>>
>> 	// Construct [lb, ub] with a known NAN state.
>> 	frange tmp (lb, ub, lhs.get_nan_state ());
>>
>> 	// Set RET without dropping/reducing the range to MIN/MAX.
>> 	ret.set (tmp, FRANGE_FLAG_NO_REPRESENTABLE_REDUCTION);
>>
>> An alternative is to allow the setter to set everything:
>>
>> 	ret.set (type, lb, ub,
>> 		lhs.get_nan_state (),
>> 		FRANGE_FLAG_NO_REPRESENTABLE_REDUCTION);
>>
>> Would this work?  I'd be happy to whip up something this week, or if
>> preferred, leave it to the next release.
> 
> The latter would be better, I really don't need a temporary range in that
> spot, the union_ is only to copy the NaN state.
> Though, I think right now set actually doesn't do reduction to representable
> at all, all it does is equality compare bounds against the applicable
> boundaries and if both are equal and NaN state is appropriate, change it
> into VR_VARYING.
> So maybe for now all we need is the 4 argument set.

So, this?

frange::set (tree type,
	const REAL_VALUE_TYPE &min,
	const REAL_VALUE_TYPE &max,
	const nan_state &,
	value_range_kind kind = VR_RANGE)

If so, I'll start poking at it.

Aldy