public inbox for gcc-bugs@sourceware.org help / color / mirror / Atom feed
From: "pinskia at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug tree-optimization/85234] missed optimisation opportunity for (x >> CST)!=0 is not optimized to (((unsigned)x) >= (1<<CST) Date: Sun, 28 May 2023 23:05:40 +0000 [thread overview] Message-ID: <bug-85234-4-xZLt7jCBC0@http.gcc.gnu.org/bugzilla/> (raw) In-Reply-To: <bug-85234-4@http.gcc.gnu.org/bugzilla/> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85234 --- Comment #5 from Andrew Pinski <pinskia at gcc dot gnu.org> --- Here is the testcase for the constants besides 0:L ``` #define N 3 #define unsigned int #define cmp == #define M 0xf0000000u _Bool f(unsigned x, int t) { return (x << N) cmp (M << N); } _Bool f1(unsigned x, int t) { return ((x^M) & (-1u>>N)) cmp 0; } _Bool f2(unsigned x, int t) { return (x & (-1u>>N)) cmp (M & (-1u>>N)); } _Bool g(unsigned x, int t) { return (x >> N) cmp M; } _Bool g2(unsigned x, int t) { _Bool tttt = 0; if (tttt) return 0; return (x & (-1u<<N)) cmp (M << N); } #if M==0 _Bool g1(unsigned x, int t) { return (x >= (1u<<N)) cmp M; } #endif ``` The tttt is defined somehow but I can't figure it out right now. Note for f, The bottom N bits need not to be set, that is basically what (M << N) specifies.
prev parent reply other threads:[~2023-05-28 23:05 UTC|newest] Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top [not found] <bug-85234-4@http.gcc.gnu.org/bugzilla/> 2021-07-20 23:33 ` [Bug middle-end/85234] missed optimisation opportunity for (~x >> n) ? a : b with n, a, b constants pinskia at gcc dot gnu.org 2021-07-20 23:44 ` [Bug tree-optimization/85234] missed optimisation opportunity for (~x >> CST)!=0 is not optimized to (((unsigned)x) < ~((1<<CST) - 1)) pinskia at gcc dot gnu.org 2023-05-28 2:26 ` [Bug tree-optimization/85234] missed optimisation opportunity for (x >> CST)!=0 is not optimized to (((unsigned)x) >= (1<<CST) pinskia at gcc dot gnu.org 2023-05-28 22:10 ` pinskia at gcc dot gnu.org 2023-05-28 23:05 ` pinskia at gcc dot gnu.org [this message]
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-85234-4-xZLt7jCBC0@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: 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).