This is the mail archive of the
mailing list for the GCC project.
Re: [PATCH 1/8] Document signaling for min, max and ltgt operations
> Am 20.08.2019 um 19:13 schrieb Segher Boessenkool <email@example.com>:
> On Tue, Aug 20, 2019 at 06:13:00PM +0200, Ilya Leoshkevich wrote:
>>> Am 20.08.2019 um 17:50 schrieb Segher Boessenkool <firstname.lastname@example.org>:
>>> There is currently no way to say (in trees or gimple or rtl) whether
>>> comparisons are signaling ("ordered", generate a trap on an unordered
>>> result). I am working on this, but :-)
>> Isn't there? This whole series is based on the following assumption:
>> LT, LE, GT, GE are definitely signaling; LTGT is most likely signaling
>> as well; the rest are not signaling. This is based on gccint 11.6.3:
>> Unary and Binary Expressions.
> There is currently no way to implement, say, iseqsig. And whether an
> operation is signaling should be determined by the language frontend,
> not separately by each backend!
Wouldn't expressing it as ((x <= y) && (x >= y)) work?
In any case, I'll need to check whether my patch series handles iseqsig
in at least remotely sane way..
> (There should be a signaling and a non-signaling version of every float
> comparison that can be unordered).
I wholeheartedly agree. I had to write quite a few ugly patterns to
work around the lack of e.g. non-signaling GT.