public inbox for gcc-bugs@sourceware.org
help / color / mirror / Atom feed
From: "pavel.morozkin at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c/103193] New: gcc for x86_64: wrong code generation: ucomiss instead of comiss
Date: Thu, 11 Nov 2021 15:19:56 +0000	[thread overview]
Message-ID: <bug-103193-4@http.gcc.gnu.org/bugzilla/> (raw)

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

            Bug ID: 103193
           Summary: gcc for x86_64: wrong code generation: ucomiss instead
                    of comiss
           Product: gcc
           Version: 11.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: pavel.morozkin at gmail dot com
  Target Milestone: ---

This code:
#pragma STDC FENV_ACCESS ON
float f;
_Bool b;
f = NAN;
b = f >= f; // ucomiss (wrong), comiss (correct)

results in:
ucomiss xmm0, DWORD PTR [rbp-4]


Per IEEE 754-2008 the ">=" is compareSignalingGreaterEqual, which can be
implemented using comiss.

Notes:
1. Yes, the #pragma STDC FENV_ACCESS ON is not yet supported. Just wanted to
point out that under #pragma STDC FENV_ACCESS ON gcc needs to generate comiss
(not ucomiss).
2. Adding volatile to float f; results in generation of comiss (expected).

             reply	other threads:[~2021-11-11 15:19 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-11-11 15:19 pavel.morozkin at gmail dot com [this message]
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
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

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=bug-103193-4@http.gcc.gnu.org/bugzilla/ \
    --to=gcc-bugzilla@gcc.gnu.org \
    --cc=gcc-bugs@gcc.gnu.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).