From: Jakub Jelinek <jakub@redhat.com>
To: Aldy Hernandez <aldyh@redhat.com>
Cc: GCC patches <gcc-patches@gcc.gnu.org>,
Richard Biener <richard.guenther@gmail.com>,
Andrew MacLeod <amacleod@redhat.com>
Subject: Re: [PATCH] Handle > INF and < INF correctly in range-op-float.cc
Date: Tue, 6 Sep 2022 09:35:49 +0200 [thread overview]
Message-ID: <Yxb4VcSp1La/sm74@tucnak> (raw)
In-Reply-To: <20220906072901.3472801-1-aldyh@redhat.com>
On Tue, Sep 06, 2022 at 09:29:01AM +0200, Aldy Hernandez wrote:
> The gfortran.dg/minlocval*.f90 tests are generating conditionals past
> the infinities. For example:
>
> if (x <= +Inf)
> foo (x);
> else
> bar (x);
>
> It seems to me that the only possible value for x on the false side is
> either NAN or undefined (for !HONOR_NANS).
No, none of the ==, <, <=, >, >= comparisons are ever true if one
or both operands are NaN (only != will be true in those cases from the
standard comparisons, when not counting UNORDERED_EXPR and the likes).
So, x < -Inf or x > +Inf are always false, we just can't optimize those
away without -ffast-math because they could raise an exception on sNaN.
But I think not optimizing such operations away if we care about exceptions
is the duty of DCE etc.
Jakub
next prev parent reply other threads:[~2022-09-06 7:36 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-06 7:29 Aldy Hernandez
2022-09-06 7:35 ` Jakub Jelinek [this message]
2022-09-06 7:40 ` Aldy Hernandez
2022-09-06 7:44 ` Jakub Jelinek
2022-09-06 7:49 ` Aldy Hernandez
2022-09-06 7:59 ` Jakub Jelinek
2022-09-06 11:47 ` Aldy Hernandez
2022-09-06 12:06 ` Jakub Jelinek
2022-09-06 12:17 ` Richard Biener
2022-09-06 12:32 ` Aldy Hernandez
2022-09-06 12:38 ` Koning, Paul
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