public inbox for gcc-bugs@sourceware.org help / color / mirror / Atom feed
From: "redi at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug c++/108243] [10/11/12/13 Regression] Missed optimization for static const std::string_view(const char*) Date: Wed, 04 Jan 2023 13:20:40 +0000 [thread overview] Message-ID: <bug-108243-4-iOO5mcQ9PP@http.gcc.gnu.org/bugzilla/> (raw) In-Reply-To: <bug-108243-4@http.gcc.gnu.org/bugzilla/> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108243 Jonathan Wakely <redi at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Summary|Missed optimization for |[10/11/12/13 Regression] |static const |Missed optimization for |std::string_view(const |static const |char*) |std::string_view(const | |char*) --- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> --- And if the variable is like this it does optimize it: static constexpr string_view foo("bar"); Because then we take the constant evaluation path and calculate the length by hand. The problem seems to be that GCC considers the __builtin_is_constant_evaluated() branch to be reachable for non-constexpr and so doesn't inline as aggressively. If we have: struct traits { static constexpr unsigned long length(const char* s) { #ifndef FIX if (__builtin_is_constant_evaluated()) { unsigned long n = 0; while (*s++) ++n; return n; } #endif return __builtin_strlen(s); } }; struct string_view { constexpr string_view(const char* s) : str(s), len(traits::length(s)) { } unsigned long size() const { return len; } const char* str; unsigned long len; }; int main() { static const string_view foo("bar"); return foo.size(); } Then with -DFIX we optimize correctly, but without -DFIX we don't. That block of code should make no difference to inlining decisions, because at runtime it is always dead code.
next prev parent reply other threads:[~2023-01-04 13:20 UTC|newest] Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top 2022-12-28 16:31 [Bug c++/108243] New: " erosenberger at kinetica dot com 2023-01-04 11:42 ` [Bug c++/108243] " redi at gcc dot gnu.org 2023-01-04 13:05 ` redi at gcc dot gnu.org 2023-01-04 13:15 ` redi at gcc dot gnu.org 2023-01-04 13:20 ` redi at gcc dot gnu.org [this message] 2023-01-04 13:21 ` [Bug c++/108243] [10/11/12/13 Regression] " redi at gcc dot gnu.org 2023-01-04 16:47 ` ppalka at gcc dot gnu.org 2023-01-04 17:22 ` jakub at gcc dot gnu.org 2023-01-09 14:05 ` rguenth at gcc dot gnu.org 2023-01-27 19:13 ` ppalka at gcc dot gnu.org 2023-02-17 20:21 ` cvs-commit at gcc dot gnu.org 2023-02-20 5:23 ` de34 at live dot cn 2023-02-20 18:33 ` ppalka at gcc dot gnu.org 2023-02-21 13:38 ` rguenth at gcc dot gnu.org 2023-02-21 14:09 ` ppalka at gcc dot gnu.org 2023-03-02 19:05 ` cvs-commit at gcc dot gnu.org 2023-03-02 19:05 ` cvs-commit at gcc dot gnu.org 2023-03-02 19:51 ` [Bug c++/108243] [10/11/12 " ppalka at gcc dot gnu.org 2023-07-07 10:44 ` [Bug c++/108243] [11/12 " rguenth at gcc dot gnu.org 2023-12-13 16:48 ` cvs-commit 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-108243-4-iOO5mcQ9PP@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).