public inbox for gcc-bugs@sourceware.org
help / color / mirror / Atom feed
From: "pskocik at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c/107831] New: Missed optimization: -fclash-stack-protection causes unnecessary code generation for dynamic stack allocations that are clearly less than a page
Date: Wed, 23 Nov 2022 10:09:46 +0000	[thread overview]
Message-ID: <bug-107831-4@http.gcc.gnu.org/bugzilla/> (raw)

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107831

            Bug ID: 107831
           Summary: Missed optimization: -fclash-stack-protection causes
                    unnecessary code generation for dynamic stack
                    allocations that are clearly less than a page
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: pskocik at gmail dot com
  Target Milestone: ---

I'm talking allocations such as

char buf [ (uint8_t)size ];

The resulting code for this should ideally be the same with or without
-fstack-clash-protection as this can clearly never skip a whole page.

But gcc generates a big loop trying to touch every page-sized subpart of that
allocation.

https://godbolt.org/z/G8EbzbshK

             reply	other threads:[~2022-11-23 10:09 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-11-23 10:09 pskocik at gmail dot com [this message]
2022-11-23 12:34 ` [Bug c/107831] " pskocik at gmail dot com
2022-11-23 17:01 ` jakub at gcc dot gnu.org
2022-11-23 17:05 ` jakub at gcc dot gnu.org
2022-11-23 17:37 ` jakub at gcc dot gnu.org
2022-11-23 17:57 ` law at gcc dot gnu.org
2022-11-23 21:27 ` pskocik at gmail dot com
2022-11-24 19:16 ` pskocik at gmail dot com
2022-11-24 19:31 ` jakub at gcc dot gnu.org
2022-12-17 19:51 ` pskocik at gmail dot com

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-107831-4@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: link
Be 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).