public inbox for gcc-bugs@sourceware.org
help / color / mirror / Atom feed
From: "arnd at linaro dot org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c/94986] New: missing diagnostic on ARM thumb2 compilation with -pg when using r7 in inline asm
Date: Thu, 07 May 2020 15:59:46 +0000	[thread overview]
Message-ID: <bug-94986-4@http.gcc.gnu.org/bugzilla/> (raw)

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94986

            Bug ID: 94986
           Summary: missing diagnostic on ARM thumb2 compilation with -pg
                    when using r7 in inline asm
           Product: gcc
           Version: 10.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: arnd at linaro dot org
  Target Milestone: ---

I reported a bug against clang for a Linux kernel failure, but 
 it was suggested that the clang behavior is probably correct in this corner
case while gcc gets it wrong, see https://bugs.llvm.org/show_bug.cgi?id=45826

echo 'void f(void) { asm("mov r7, #0" ::: "r7"); }' | arm-linux-gnueabi-gcc
-march=armv7-a -O2  -mthumb -pg -S -xc -

silently accepts an inline asm statement that clobbers the frame pointer, but
gcc rejects the same code if any of '-O0', '-fomit-frame-pointer' or
'fno-omit-frame-pointer' are used:

<stdin>: In function 'f':
<stdin>:1:44: error: r7 cannot be used in 'asm' here

If using r7 in this case is indeed invalid, we need to ensure the kernel does
not do this, and having gcc reject it would be helpful.

             reply	other threads:[~2020-05-07 15:59 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-07 15:59 arnd at linaro dot org [this message]
2020-06-03 16:37 ` [Bug target/94986] " wilco at gcc dot gnu.org
2020-06-03 16:49 ` nsz at gcc dot gnu.org
2020-06-03 17:00 ` wilco at gcc dot gnu.org
2020-06-03 17:16 ` ndesaulniers at google dot com
2020-06-03 17:23 ` nsz 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-94986-4@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).