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From: "arjun.is at lostca dot se" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/95185] Failure to optimize specific kind of sign comparison check
Date: Mon, 04 Oct 2021 23:02:38 +0000	[thread overview]
Message-ID: <bug-95185-4-yu0oeuIPyR@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-95185-4@http.gcc.gnu.org/bugzilla/>

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95185

Arjun Shankar <arjun.is at lostca dot se> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |arjun.is at lostca dot se

--- Comment #3 from Arjun Shankar <arjun.is at lostca dot se> ---
If the code is compiled as C, gcc produces essentially the same code as clang
with some differences in the schedule of instructions:
https://godbolt.org/z/8nsq16Pen

It's when the code is compiled as C++ that gcc does worse:
https://godbolt.org/z/dK8hTEhjr

The difference lies in the front-ends. The C front-end already appears to know
that this is a XOR. testcase.c.004t.original looks like:

  return (int) (x < 0 ^ y <= 0);

On the other hand, g++ outputs:

  return <retval> = x >= 0 == y <= 0;

  parent reply	other threads:[~2021-10-04 23:02 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-18 12:05 [Bug tree-optimization/95185] New: " gabravier at gmail dot com
2020-05-18 13:15 ` [Bug tree-optimization/95185] " rguenth at gcc dot gnu.org
2020-05-18 13:16 ` rguenth at gcc dot gnu.org
2021-10-04 23:02 ` arjun.is at lostca dot se [this message]
2021-10-04 23:12 ` pinskia at gcc dot gnu.org
2023-06-18 19:24 ` pinskia at gcc dot gnu.org
2023-08-28 20:36 ` pinskia at gcc dot gnu.org
2023-08-28 21:08 ` pinskia at gcc dot gnu.org
2023-08-29  4:04 ` pinskia at gcc dot gnu.org
2023-09-11 22:14 ` [Bug tree-optimization/95185] [11/12/13/14 Regression] " pinskia at gcc dot gnu.org
2024-03-22 14:09 ` law at gcc dot gnu.org

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