public inbox for gcc-bugs@sourceware.org help / color / mirror / Atom feed
From: "pinskia at gcc dot gnu dot org" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug middle-end/23664] New: fold does not change (a&C1)+(b&C2) to (a&C1)|(b&C2) iff (C1 & C2) == 0 Date: Thu, 01 Sep 2005 00:40:00 -0000 [thread overview] Message-ID: <20050901004014.23664.pinskia@gcc.gnu.org> (raw) These two functions should produce the same asm: int f(int a, int b) { return (a&0xF)+(b&0xF0); } int f1(int a, int b) { return (a&0xF)|(b&0xF0); } For PPC, we get: _f: rlwinm r4,r4,0,24,27 rlwinm r3,r3,0,28,31 add r3,r3,r4 blr _f1: rlwinm r4,r4,0,24,27 rlwimi r3,r4,0,0,27 blr Which shows the | is more efficient than the + one. -- Summary: fold does not change (a&C1)+(b&C2) to (a&C1)|(b&C2) iff (C1 & C2) == 0 Product: gcc Version: 4.1.0 Status: UNCONFIRMED Keywords: missed-optimization Severity: enhancement Priority: P2 Component: middle-end AssignedTo: unassigned at gcc dot gnu dot org ReportedBy: pinskia at gcc dot gnu dot org CC: gcc-bugs at gcc dot gnu dot org GCC target triplet: powerpc-*-* OtherBugsDependingO 19987 nThis: http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23664
next reply other threads:[~2005-09-01 0:40 UTC|newest] Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top 2005-09-01 0:40 pinskia at gcc dot gnu dot org [this message] 2005-09-01 0:42 ` [Bug middle-end/23664] " pinskia at gcc dot gnu dot org 2005-09-17 2:12 ` pinskia at gcc dot gnu dot 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=20050901004014.23664.pinskia@gcc.gnu.org \ --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: linkBe 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).