From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <gcc-bugzilla@gcc.gnu.org>
Received: by sourceware.org (Postfix, from userid 48)
	id 10A993858416; Fri, 26 Apr 2024 12:54:59 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 10A993858416
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org;
	s=default; t=1714136100;
	bh=sq3ziZeapobFuRpIa1RGh6+lDUlnYgc3Au9gCSh7NaI=;
	h=From:To:Subject:Date:In-Reply-To:References:From;
	b=MM4zgJh3BwbsBuN44nL7LLwjAHjlfiaM2LMALkOPAX0J6MUM/uWgvPDUA7qRNYT8N
	 TG1bMngwDMZ6yvnqw3EFpepH+GYzjkJ494DJJ2ybIPrx8V3q6et+eO/tr1adIyihVp
	 298xaiI+cb9yoLWotLbhY9Y8pF5E9djokh0Nkqwc=
From: "roger at nextmovesoftware dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug rtl-optimization/97756] [11/12/13 Regression] Inefficient
 handling of 128-bit arguments
Date: Fri, 26 Apr 2024 12:54:58 +0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: changed
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: rtl-optimization
X-Bugzilla-Version: 11.0
X-Bugzilla-Keywords: missed-optimization, ra
X-Bugzilla-Severity: normal
X-Bugzilla-Who: roger at nextmovesoftware dot com
X-Bugzilla-Status: NEW
X-Bugzilla-Resolution: 
X-Bugzilla-Priority: P2
X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org
X-Bugzilla-Target-Milestone: 11.5
X-Bugzilla-Flags: 
X-Bugzilla-Changed-Fields: cf_known_to_work short_desc
Message-ID: <bug-97756-4-zR5DVvQuIL@http.gcc.gnu.org/bugzilla/>
In-Reply-To: <bug-97756-4@http.gcc.gnu.org/bugzilla/>
References: <bug-97756-4@http.gcc.gnu.org/bugzilla/>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/
Auto-Submitted: auto-generated
MIME-Version: 1.0
List-Id: <gcc-bugs.sourceware.org>

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D97756

Roger Sayle <roger at nextmovesoftware dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
      Known to work|                            |14.0
            Summary|[11/12/13/14/15 Regression] |[11/12/13 Regression]
                   |Inefficient handling of     |Inefficient handling of
                   |128-bit arguments           |128-bit arguments

--- Comment #17 from Roger Sayle <roger at nextmovesoftware dot com> ---
I believe this issue is now fixed on mainline (i.e. for both GCC 14 and GCC
15).
Firstly, many thanks to Jakub for correcting the error in my patch. We now
generate optimal code sequences for the code in comments #3 and #5, and use
generate fewer instructions than described in the original description.

The final remaining issue is that with -O3 GCC still uses more instructions
than clang and icc (see Thomas' comments in comments #12 and #13).  The good
news is that this is intentional, compiling with -Os (to optimize for size)
generates the same number of instructions as clang and icc [in fact, using =
icc
-Os generates larger code!?].  So when optimizing for performance, GCC is
taking the opportunity to use more (cheap) instructions to execute faster (=
or
that's the theory).=