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From: "joseph at codesourcery dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug middle-end/103193] gcc for x86_64: wrong code generation: ucomiss instead of comiss
Date: Fri, 12 Nov 2021 23:35:37 +0000	[thread overview]
Message-ID: <bug-103193-4-70mFpWj33U@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-103193-4@http.gcc.gnu.org/bugzilla/>

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103193

--- Comment #5 from joseph at codesourcery dot com <joseph at codesourcery dot com> ---
On Fri, 12 Nov 2021, rguenth at gcc dot gnu.org via Gcc-bugs wrote:

> /* Simplify comparison of something with itself.  For IEEE
>    floating-point, we can only do some of these simplifications.  */
> (for cmp (eq ge le)
>  (simplify
>   (cmp @0 @0)
>   (if (! FLOAT_TYPE_P (TREE_TYPE (@0))
>        || ! HONOR_NANS (@0))
>    { constant_boolean_node (true, type); }
>    (if (cmp != EQ_EXPR)
>     (eq @0 @0)))))
> 
> does this.  The folding to == happens unconditionally.  As I understand you
> the condition that applies to the constant folding should apply to the
> folding to EQ as well, which means we effectively need to remove the
> canonicalization to EQ (since when it would be valid we can fold to constant
> true)?

It's invalid with -ftrapping-math because it loses an exception.  With 
-fno-trapping-math, but NaNs supported, you can convert to EQ but can't 
fold to constant true.

  parent reply	other threads:[~2021-11-12 23:35 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-11-11 15:19 [Bug c/103193] New: " pavel.morozkin at gmail dot com
2021-11-11 17:41 ` [Bug target/103193] " joseph at codesourcery dot com
2021-11-11 20:07 ` ubizjak at gmail dot com
2021-11-11 21:29 ` joseph at codesourcery dot com
2021-11-12  7:35 ` [Bug middle-end/103193] " rguenth at gcc dot gnu.org
2021-11-12 23:35 ` joseph at codesourcery dot com [this message]
2021-11-15 10:12 ` rguenth at gcc dot gnu.org
2021-11-24 10:02 ` cvs-commit at gcc dot gnu.org
2021-11-24 10:07 ` rguenth at gcc dot gnu.org
2022-07-22 11:21 ` cvs-commit at gcc dot gnu.org
2022-07-22 11:23 ` rguenth at gcc dot gnu.org

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