From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: by sourceware.org (Postfix, from userid 48) id 6FAA6385DC10; Tue, 14 Apr 2020 13:20:53 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 6FAA6385DC10 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org; s=default; t=1586870453; bh=XDN2JzAwNrIG0JQx28Ka0forRGb2lG2swo0grShtU3o=; h=From:To:Subject:Date:In-Reply-To:References:From; b=a5+dJ1z4mQoUt3C/6rUFqSGJDyJ8x7pQxn03QHHcYSzEK8MuR7koL+IQMBlxiYr/h qrM8TzO3G2vUN2INW8g+EGIa6YbtgyML465W1MsLG9XwEOOmreWbqZvtbgL+u2EkqK kNmsX5KqsDjz416QorQeNo8VNYEj8/AlafqEless= From: "law at redhat dot com" To: gcc-bugs@gcc.gnu.org Subject: [Bug target/94567] [10 Regression] wrong code at -O2 and -O3 on x86_64-linux-gnu Date: Tue, 14 Apr 2020 13:20:53 +0000 X-Bugzilla-Reason: CC X-Bugzilla-Type: changed X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: gcc X-Bugzilla-Component: target X-Bugzilla-Version: 10.0 X-Bugzilla-Keywords: wrong-code X-Bugzilla-Severity: normal X-Bugzilla-Who: law at redhat dot com X-Bugzilla-Status: ASSIGNED X-Bugzilla-Resolution: X-Bugzilla-Priority: P1 X-Bugzilla-Assigned-To: law at redhat dot com X-Bugzilla-Target-Milestone: 10.0 X-Bugzilla-Flags: X-Bugzilla-Changed-Fields: Message-ID: In-Reply-To: References: 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 X-BeenThere: gcc-bugs@gcc.gnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Gcc-bugs mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 14 Apr 2020 13:20:53 -0000 https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D94567 --- Comment #7 from Jeffrey A. Law --- I think it's trying to use smaller modes because the encodings can be small= er.=20 In other cases it changes the mode to avoid partial register stalls. It's a bit of a mess. WRT the fragment you mentioned, I looked at that repeatedly trying to ascer= tain the real motivation and whether or not that code needed generalization to handle this case or was a misguided attempt to fix another instance of this issue. The conclusion I came to was that hunk of code may well be working around another instance of this same problem, but it was neither generalizable to = this BZ nor would my approach totally fix that instance. We may be able to remove the hack in the testqi_ext_3 pattern, but I think = the corresponding hack in testdi_1 would have to stay unless we found a way to merge testdi_1 into the more general test_1 pattern. Neither of those seems terribly appropriate right now.=