[Bug target/45886] New: [ARM] support for __ARM_PCS_VFP predefined symbol in gcc 4.5.x would be very nice

[Bug target/45886] New: [ARM] support for __ARM_PCS_VFP predefined symbol in gcc 4.5.x would be very nice

[siarhei.siamashka at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45886

           Summary: [ARM] support for __ARM_PCS_VFP predefined symbol in
                    gcc 4.5.x would be very nice
           Product: gcc
           Version: 4.5.1
               URL: http://gcc.gnu.org/ml/gcc-patches/2010-07/msg02186.htm
                    l
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: P3
         Component: target
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: siarhei.siamashka@gmail.com
                CC: rearnsha@arm.com
              Host: arm-unknown-linux-gnueabi
            Target: arm-unknown-linux-gnueabi
             Build: arm-unknown-linux-gnueabi


This is quite important for JIT code when we want so support all ABI variants
properly. Because now gcc 4.5.x supports -mfloat-abi=hard, being able to
identify its use is also needed.

[Bug target/45886] [ARM] support for __ARM_PCS_VFP predefined symbol in gcc 4.5.x would be very nice

[ramana at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45886

Ramana Radhakrishnan <ramana at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2010.10.07 08:15:57
                 CC|                            |ramana at gcc dot gnu.org
      Known to work|                            |4.6.0
   Target Milestone|---                         |4.5.2
     Ever Confirmed|0                           |1
      Known to fail|                            |4.5.0, 4.5.1
           Severity|enhancement                 |normal

--- Comment #1 from Ramana Radhakrishnan <ramana at gcc dot gnu.org> 2010-10-07 08:15:57 UTC ---
Confirmed though I think this isn't an "enhancement" but more a bug because
code can't identify whether -mfloat-abi=hard is chosen by use of a
pre-processor directive.

Ramana

[Bug target/45886] [ARM] support for __ARM_PCS_VFP predefined symbol in gcc 4.5.x would be very nice

[siarhei.siamashka at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45886

--- Comment #2 from Siarhei Siamashka <siarhei.siamashka at gmail dot com> 2010-10-11 14:31:29 UTC ---
(In reply to comment #1)
> Confirmed though I think this isn't an "enhancement" but more a bug because
> code can't identify whether -mfloat-abi=hard is chosen by use of a
> pre-processor directive.

Thanks. Can we expect this problem to be fixed in gcc 4.5.2 (backported from
trunk)?

For now I'm going to use the following guard code to make sure that using
unpatched gcc will result in compilation problem instead of runtime failure:

#if defined(__GNUC__) && (__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >=
5)) \
    && defined(__ARM_EABI__) && !defined(__ARM_PCS_VFP) && !defined(__ARM_PCS)
#error "Can't identify floating point calling conventions.\nPlease ensure that
your toolchain defines __ARM_PCS or __ARM_PCS_VFP."
#endif

[Bug target/45886] [ARM] support for __ARM_PCS_VFP predefined symbol in gcc 4.5.x would be very nice

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45886

Richard Guenther <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|4.5.2                       |---

[Bug target/45886] [ARM] support for __ARM_PCS_VFP predefined symbol in gcc 4.5.x would be very nice

[siarhei.siamashka at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45886

--- Comment #3 from Siarhei Siamashka <siarhei.siamashka at gmail dot com> 2010-11-12 15:30:24 UTC ---
Richard, what would be the appropriate target milestone to get this bug fixed?

This needs just a backport of a trivial patch from trunk to 4.5 branch, but
delaying this fix increases the chances of penetration of problematic gcc into
various linux distributions.

[Bug target/45886] [ARM] support for __ARM_PCS_VFP predefined symbol in gcc 4.5.x would be very nice

[siarhei.siamashka at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45886

Siarhei Siamashka <siarhei.siamashka at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |toolchain at gentoo dot org

--- Comment #4 from Siarhei Siamashka <siarhei.siamashka at gmail dot com> 2010-12-18 17:23:04 UTC ---
I'm sorry for asking again, but what is the status of this issue? Is it even
feasible to get it resolved in upstream gcc 4.5.x? Previously this issue had a
target milestone set to 4.5.2, but then is was simply removed.

While this is not strictly a regression compared to the previous releases, it
makes the use of the new major feature for arm (-mfloat-abi=hard option)
introduced in gcc 4.5 rather problematic. Just a few examples of the affected
software are the upcoming mozilla firefox4 and libffi library which use
__ARM_PCS_VFP define to identify floating point calling conventions.

The trivial fewliner patch which fixes the issue has been already adopted by
linaro gcc [1]. It is also used by ubuntu [2] and probably some other linux
distributions for the obvious pragmatic reasons.

So I wonder what is the current recommendation from your side? Make it a
responsibility of each linux distribution to patch gcc themselves? Or maybe add
some ugly hacks to the affected applications and libraries to identify floating
point calling conventions in some other way specifically for gcc 4.5.x?


1. https://wiki.linaro.org/WorkingGroups/ToolChain/Changelogs/LinaroGCC4.5
2. http://packages.ubuntu.com/natty/gcc-4.5-multilib

[Bug target/45886] [ARM] support for __ARM_PCS_VFP predefined symbol in gcc 4.5.x would be very nice

[koen at dominion dot thruhere.net]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45886

Koen Kooi <koen at dominion dot thruhere.net> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |koen at dominion dot
                   |                            |thruhere.net

--- Comment #5 from Koen Kooi <koen at dominion dot thruhere.net> 2011-01-16 15:18:04 UTC ---
I just ran into this problem while trying to fix mplayer and ffmpeg. To quote
the person who fixed that bug with __ARM_PCS_VFP:

"how the hell am I supposed to detect hardfp then?"