[Bug target/55218] New: armv6 doesn't use unaligned access for packed structures

[Bug target/55218] New: armv6 doesn't use unaligned access for packed structures

[michael.hope at linaro dot org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55218

             Bug #: 55218
           Summary: armv6 doesn't use unaligned access for packed
                    structures
    Classification: Unclassified
           Product: gcc
           Version: 4.7.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: michael.hope@linaro.org


Created attachment 28622
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=28622
Test case

The GCC ARM target uses the armv6 and above unaligned loads for packed
structures and block copies.  This works correctly for -march=armv7-a and
-march=armv6t2, but generates the old byte-by-byte field access for
-march=armv6.

The block copy is fine.  readelf -A shows that the compiler intended to use
unaligned access.  I'm suspicious that GCC is using the extv pattern to extract
the field, and this pattern is only available on cores with Thumb-2 support.

[Bug target/55218] armv6 doesn't use unaligned access for packed structures

[michael.hope at linaro dot org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55218

Michael Hope <michael.hope at linaro dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Target|                            |arm

--- Comment #1 from Michael Hope <michael.hope at linaro dot org> 2012-11-05 22:04:03 UTC ---
See also:
 http://lists.linaro.org/pipermail/linaro-toolchain/2012-November/002921.html

[Bug target/55218] armv6 doesn't use unaligned access for packed structures

[hp at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55218

--- Comment #2 from Hans-Peter Nilsson <hp at gcc dot gnu.org> 2012-11-07 02:13:32 UTC ---
(After reading the linked post.)  Somewhat related: maybe the changes.html text
should say "bootloader" or "startup code" instead of kernel because everyone
just thinks it just means "Linux".  Patches welcome.

[Bug target/55218] armv6 doesn't use unaligned access for packed structures

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=55218

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2023-02-25
     Ever confirmed|0                           |1

--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Confirmed. very similar to PR 51709 if not the same.