[Bug c/56341] New: GCC produces unaligned data access

[Bug c/56341] New: GCC produces unaligned data access

[bernd.edlinger at hotmail dot de]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56341

             Bug #: 56341
           Summary: GCC produces unaligned data access
    Classification: Unclassified
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: major
          Priority: P3
         Component: c
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: bernd.edlinger@hotmail.de


Created attachment 29464
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=29464
test program produces alignment faults

Hello,

The attached test program causes two problems when compiled with GCC 4.6.3 for
ARM:

1. test() fails to write the high word of an unaligned volatile struct member.

2. test1() crashes because it uses an unaligned word access.

This code did compile and execute correctly with GCC 4.3.2

As a workaround, the bug goes away if the code is compiled with
-fno-strict-volatile-bitfields,
but this is probably less efficient code.


The attached patch is a backport of the following patch, and seems to resolve
this issue:

http://gcc.gnu.org/ml/gcc-patches/2012-08/msg01449.html

the original patch ignored the alignment of the target, and fixed only the
first test case, but not the crash in the second test case.

Regards
Bernd Edlinger

[Bug c/56341] GCC produces unaligned data access

[bernd.edlinger at hotmail dot de]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56341

--- Comment #1 from Bernd Edlinger <bernd.edlinger at hotmail dot de> 2013-02-15 13:12:56 UTC ---
Created attachment 29465
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=29465
proposed patch

attached is a patch for gcc-4.6.3 that should resolve this issue.
volatile packed struct members are accessed in words if structure
is aligned by 2 and in bytes if structure is aligned by 1.

[Bug c/56341] GCC produces unaligned data access

[mikpe at it dot uu.se]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56341

Mikael Pettersson <mikpe at it dot uu.se> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |mikpe at it dot uu.se

--- Comment #2 from Mikael Pettersson <mikpe at it dot uu.se> 2013-02-15 14:19:28 UTC ---
The test case causes alignment exceptions for me on armv5tel-linux-gnueabi,
when compiled with any one of gcc 4.8, 4.7, or 4.6.  Was Sandra's patch ever
applied?

[Bug c/56341] GCC produces unaligned data access

[bernd.edlinger at hotmail dot de]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56341

--- Comment #3 from Bernd Edlinger <bernd.edlinger at hotmail dot de> 2013-02-15 14:46:39 UTC ---
(In reply to comment #2)
> The test case causes alignment exceptions for me on armv5tel-linux-gnueabi,
> when compiled with any one of gcc 4.8, 4.7, or 4.6.  Was Sandra's patch ever
> applied?

apparently not. not in 4.6.x not in 4.7.2.

When I used the original patch the assignment in test() was fixed,
but the crash in test1() was still there, because the patch
did not pay attention to the alignment of the structure.

Therefore I added a check for the alignment in both read and
write instructions.

Regards,
Bernd Edlinger.

[Bug middle-end/56341] GCC produces unaligned data access

[pinskia at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56341

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Target|                            |arm*-*-*
          Component|c                           |middle-end
            Version|unknown                     |4.6.3
           Severity|major                       |normal

[Bug middle-end/56341] GCC produces unaligned data access

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56341

--- Comment #4 from Richard Biener <rguenth at gcc dot gnu.org> 2013-02-18 11:20:43 UTC ---
There is now better ways of implementing -fstrict-volatile-bitfields which
I repeatedly told the arm people.  Not for 4.6, but for 4.7 and trunk.

[Bug middle-end/56341] GCC produces unaligned data access

[sandra at codesourcery dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56341

Sandra Loosemore <sandra at codesourcery dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |sandra at codesourcery dot
                   |                            |com

--- Comment #5 from Sandra Loosemore <sandra at codesourcery dot com> 2013-02-18 15:30:16 UTC ---
The patch linked from the initial message was rejected.  I did not (and still
do not) have the time to rewrite it; if someone else can figure out how to fix
this in a way that's acceptable to the maintainers, that would be great.

[Bug middle-end/56341] GCC produces unaligned data access

[bernd.edlinger at hotmail dot de]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56341

--- Comment #6 from Bernd Edlinger <bernd.edlinger at hotmail dot de> 2013-02-18 18:41:55 UTC ---
hhmm...

could some one give an example where packedp would be false but the value
is packed or unaligned?

[Bug middle-end/56341] GCC produces unaligned data access

[bernd.edlinger at hotmail dot de]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56341

Bernd Edlinger <bernd.edlinger at hotmail dot de> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
  Attachment #29465|0                           |1
        is obsolete|                            |

--- Comment #7 from Bernd Edlinger <bernd.edlinger at hotmail dot de> 2013-02-20 01:38:04 UTC ---
Created attachment 29506
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=29506
proposed patch

this patch uses packedp only for the warn_misaligned_bitfield()
but does always use multiple load or stores. So even if the
packedp may be unreliable it will only have influence on the warning text.

reason:
if packedp == false the code will always use a single but mis-aligned
instruction which is known to abort at runtime. So that is always wrong.

note: there are two almost identical formula used for packedp.

packedp as it is used in extract_bit_field (old code):
        if (TYPE_PACKED (TREE_TYPE (TREE_OPERAND (exp, 0)))
            || (TREE_CODE (TREE_OPERAND (exp, 1)) == FIELD_DECL
                && DECL_PACKED (TREE_OPERAND (exp, 1))))
          packedp = true;

packedp as it is used in store_field (new code):
        if (TREE_CODE(to) == COMPONENT_REF
            && (TYPE_PACKED (TREE_TYPE (TREE_OPERAND (to, 0)))
                || (TREE_CODE (TREE_OPERAND (to, 1)) == FIELD_DECL
                    && DECL_PACKED (TREE_OPERAND (to, 1)))))
          packedp = true;

However if we can not trust the second one why should we trust the first one?

Therefore the packedp should not have influence on the code generation at all.
That would only take unnecessary risks.

Well, I think that should resolve your objections... Right?

[Bug middle-end/56341] GCC produces unaligned data access

[bernd.edlinger at hotmail dot de]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56341

Bernd Edlinger <bernd.edlinger at hotmail dot de> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
  Attachment #29506|0                           |1
        is obsolete|                            |

--- Comment #8 from Bernd Edlinger <bernd.edlinger at hotmail dot de> 2013-02-26 18:24:58 UTC ---
Created attachment 29546
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=29546
proposed patch, cleaned up

in the last version of this patch the packedp parameter had only an
impact on the generated warning.

if packedp==true the warning is:
"multiple accesses to volatile structure member/bitfield
 because of packed attribute"

if packedp==false the warning is:
"mis-aligned access used for structure member/bitfield
 when a volatile object spans multiple type-sized locations,
 the compiler must choose between using a single mis-aligned access to
 preserve the volatility, or using multiple aligned accesses to avoid
 runtime faults; this code may fail at runtime if the hardware does
 not allow this access"

The second warning says in short:
"I am going to generate mis-aligned code, and I know it will fail at runtime."

However this patch is supposed to avoid mis-aligned code, at least for ARM.
Therefore it is only natural that the second warning is no longer needed.

Now I removed all packedp code in extract_bit_field and store_bit_field,
including the second warning. Fortunately that makes the patch much smaller.

I did boot-strap the patched compiler several times, and everything looks good.

TODO: remove translations of the obsolete warnings. (I dont know how to)

[Bug middle-end/56341] GCC produces unaligned data access

[bernd.edlinger at hotmail dot de]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56341

--- Comment #9 from Bernd Edlinger <bernd.edlinger at hotmail dot de> 2013-03-27 10:36:48 UTC ---
Hello GCC-Maintainers,

what do you think? Should'nt this patch be in the 4.6.4 release?

[Bug middle-end/56341] GCC produces unaligned data access

[sandra at codesourcery dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56341

--- Comment #10 from Sandra Loosemore <sandra at codesourcery dot com> ---
I'm working on a new patch that addresses the first problem, the failure in
test().

I think the second failure is not in test1() at all, and has nothing to do with
-fstrict-volatile-bitfields.  Looks to me like problem is that the expression
"&x1->t1" is returning an unaligned pointer due to the packed attribute on
struct test2.  It should probably not be allowed to take the address of a
packed struct field, at least on targets that require strict alignment.

Hmmmm, that bug is already filed as PR 41809.

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41809

[Bug middle-end/56341] GCC produces unaligned data access

[bernd.edlinger at hotmail dot de]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56341

--- Comment #11 from Bernd Edlinger <bernd.edlinger at hotmail dot de> ---
Created attachment 30248
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=30248&action=edit
another example of the alignment faults

Hello Sandra,

good that you continue to work on that bug again.

I agree that there may be two completely different aspects of this bug.
Attached you'll find a new test program that came in my mind when I
looked at PR 41809, the structure s is aligned 2 and packed.
If you make it an array of size 10, each second call of f is given
an odd pointer. But the compiler should know that because of the
aligned(2) attribute.

What is the difference to PR 41809 is this:
1. PR 41809 is not a correct C-program at all, and has never been.
   While this attached new test program is correct C program.
   previous GCC versions did compile that correctly, current GCC does not even
   emit a warning.

2. PR 41809 is not about volatile at all.
   However if you remove the "volatile" in the test program(s),
   the code is correct and does no longer use unaligned addresses.

On the other hand, "volatile" might mean that the compiler
should try not to optimize the read instructions, for instance in loops.
But of course not to an extent that the generated code is no longer valid.

[Bug middle-end/56341] GCC produces unaligned data access

[sandra at codesourcery dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56341

--- Comment #12 from Sandra Loosemore <sandra at codesourcery dot com> ---
Patch for the first problem posted here:

http://gcc.gnu.org/ml/gcc-patches/2013-06/msg00750.html

[Bug middle-end/56341] GCC produces unaligned data access

[sandra at codesourcery dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56341

--- Comment #13 from Sandra Loosemore <sandra at codesourcery dot com> ---
Updated patch series:

http://gcc.gnu.org/ml/gcc-patches/2013-09/msg02057.html
http://gcc.gnu.org/ml/gcc-patches/2013-09/msg02058.html
http://gcc.gnu.org/ml/gcc-patches/2013-09/msg02059.html

Unfortunately, it seems that fixing bugs with -fstrict-volatile-bitfields has
been blocked by disagreement between global reviewers and target maintainers
who can't agree on whether the C/C++11 memory model should take precedence over
target-specific ABIs by default.  :-(

[Bug middle-end/56341] GCC produces unaligned data access

[ramana at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56341

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |wrong-code
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2013-10-30
                 CC|                            |ramana at gcc dot gnu.org
     Ever confirmed|0                           |1
      Known to fail|                            |4.7.3, 4.8.0, 4.8.1, 4.9.0

--- Comment #14 from Ramana Radhakrishnan <ramana at gcc dot gnu.org> ---
well, confirmed.

[Bug middle-end/56341] GCC produces unaligned data access

[edlinger at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56341

--- Comment #15 from edlinger at gcc dot gnu.org ---
Author: edlinger
Date: Wed Dec 11 16:50:05 2013
New Revision: 205896

URL: http://gcc.gnu.org/viewcvs?rev=205896&root=gcc&view=rev
Log:
2013-12-11  Sandra Loosemore  <sandra@codesourcery.com>

        PR middle-end/23623
        PR middle-end/48784
        PR middle-end/56341
        PR middle-end/56997

        gcc/
        * expmed.c (strict_volatile_bitfield_p): New function.
        (store_bit_field_1): Don't special-case strict volatile
        bitfields here.
        (store_bit_field): Handle strict volatile bitfields here instead.
        (store_fixed_bit_field): Don't special-case strict volatile
        bitfields here.
        (extract_bit_field_1): Don't special-case strict volatile
        bitfields here.
        (extract_bit_field): Handle strict volatile bitfields here instead.
        (extract_fixed_bit_field): Don't special-case strict volatile
        bitfields here.  Simplify surrounding code to resemble that in
        store_fixed_bit_field.
        * doc/invoke.texi (Code Gen Options): Update
        -fstrict-volatile-bitfields description.

        gcc/testsuite/
        * gcc.dg/pr23623.c: New test.
        * gcc.dg/pr48784-1.c: New test.
        * gcc.dg/pr48784-2.c: New test.
        * gcc.dg/pr56341-1.c: New test.
        * gcc.dg/pr56341-2.c: New test.
        * gcc.dg/pr56997-1.c: New test.
        * gcc.dg/pr56997-2.c: New test.
        * gcc.dg/pr56997-3.c: New test.

Added:
    trunk/gcc/testsuite/gcc.dg/pr23623.c
    trunk/gcc/testsuite/gcc.dg/pr48784-1.c
    trunk/gcc/testsuite/gcc.dg/pr48784-2.c
    trunk/gcc/testsuite/gcc.dg/pr56341-1.c
    trunk/gcc/testsuite/gcc.dg/pr56341-2.c
    trunk/gcc/testsuite/gcc.dg/pr56997-1.c
    trunk/gcc/testsuite/gcc.dg/pr56997-2.c
    trunk/gcc/testsuite/gcc.dg/pr56997-3.c
Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/doc/invoke.texi
    trunk/gcc/expmed.c
    trunk/gcc/testsuite/ChangeLog

[Bug middle-end/56341] GCC produces unaligned data access

[edlinger at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56341

--- Comment #16 from edlinger at gcc dot gnu.org ---
Author: edlinger
Date: Wed Dec 11 16:59:24 2013
New Revision: 205897

URL: http://gcc.gnu.org/viewcvs?rev=205897&root=gcc&view=rev
Log:
2013-12-11  Bernd Edlinger  <bernd.edlinger@hotmail.de>
            Sandra Loosemore  <sandra@codesourcery.com>

        PR middle-end/23623
        PR middle-end/48784
        PR middle-end/56341
        PR middle-end/56997
        * expmed.c (strict_volatile_bitfield_p): Add bitregion_start
        and bitregion_end parameters.  Test for compliance with C++
        memory model.
        (store_bit_field): Adjust call to strict_volatile_bitfield_p.
        Add fallback logic for cases where -fstrict-volatile-bitfields
        is supposed to apply, but cannot.
        (extract_bit_field): Likewise. Use narrow_bit_field_mem and
        extract_fixed_bit_field_1 to do the extraction.
        (extract_fixed_bit_field): Revert to previous mode selection algorithm.
        Call extract_fixed_bit_field_1 to do the real work.
        (extract_fixed_bit_field_1): New function.

testsuite:        
        * gcc.dg/pr23623.c: Update to test interaction with C++
        memory model.

Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/expmed.c
    trunk/gcc/testsuite/ChangeLog
    trunk/gcc/testsuite/gcc.dg/pr23623.c

[Bug middle-end/56341] GCC produces unaligned data access

[bernd.edlinger at hotmail dot de]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56341

Bernd Edlinger <bernd.edlinger at hotmail dot de> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|---                         |FIXED

--- Comment #17 from Bernd Edlinger <bernd.edlinger at hotmail dot de> ---
fixed on trunk

[Bug middle-end/56341] GCC produces unaligned data access

[jye2 at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56341

--- Comment #18 from jye2 at gcc dot gnu.org ---
Author: jye2
Date: Thu Feb 27 07:28:06 2014
New Revision: 208195

URL: http://gcc.gnu.org/viewcvs?rev=208195&root=gcc&view=rev
Log:
2014-02-27  Joey Ye  <joey.ye@arm.com>

        Backport mainline strict-volatile-bitfields fixes
    2013-09-28  Sandra Loosemore  <sandra@codesourcery.com>

        gcc/
        * expr.h (extract_bit_field): Remove packedp parameter.
        * expmed.c (extract_fixed_bit_field): Remove packedp parameter
        from forward declaration.
        (store_split_bit_field): Remove packedp arg from calls to
        extract_fixed_bit_field.
        (extract_bit_field_1): Remove packedp parameter and packedp
        argument from recursive calls and calls to extract_fixed_bit_field.
        (extract_bit_field): Remove packedp parameter and corresponding
        arg to extract_bit_field_1.
        (extract_fixed_bit_field): Remove packedp parameter.  Remove code
        to issue warnings.
        (extract_split_bit_field): Remove packedp arg from call to
        extract_fixed_bit_field.
        * expr.c (emit_group_load_1): Adjust calls to extract_bit_field.
        (copy_blkmode_from_reg): Likewise.
        (copy_blkmode_to_reg): Likewise.
        (read_complex_part): Likewise.
        (store_field): Likewise.
        (expand_expr_real_1): Likewise.
        * calls.c (store_unaligned_arguments_into_pseudos): Adjust call
        to extract_bit_field.
        * config/tilegx/tilegx.c (tilegx_expand_unaligned_load): Adjust
        call to extract_bit_field.
        * config/tilepro/tilepro.c (tilepro_expand_unaligned_load): Adjust
        call to extract_bit_field.
        * doc/invoke.texi (Code Gen Options): Remove mention of warnings
        and special packedp behavior from -fstrict-volatile-bitfields
        documentation.

2013-12-11  Bernd Edlinger  <bernd.edlinger@hotmail.de>

        * expr.c (expand_assignment): Remove dependency on 
        flag_strict_volatile_bitfields. Always set the memory
        access mode.
        (expand_expr_real_1): Likewise.

2013-12-11  Sandra Loosemore  <sandra@codesourcery.com>

        PR middle-end/23623
        PR middle-end/48784
        PR middle-end/56341
        PR middle-end/56997

        gcc/
        * expmed.c (strict_volatile_bitfield_p): New function.
        (store_bit_field_1): Don't special-case strict volatile
        bitfields here.
        (store_bit_field): Handle strict volatile bitfields here instead.
        (store_fixed_bit_field): Don't special-case strict volatile
        bitfields here.
        (extract_bit_field_1): Don't special-case strict volatile
        bitfields here.
        (extract_bit_field): Handle strict volatile bitfields here instead.
        (extract_fixed_bit_field): Don't special-case strict volatile
        bitfields here.  Simplify surrounding code to resemble that in
        store_fixed_bit_field.
        * doc/invoke.texi (Code Gen Options): Update
        -fstrict-volatile-bitfields description.

        gcc/testsuite/
        * gcc.dg/pr23623.c: New test.
        * gcc.dg/pr48784-1.c: New test.
        * gcc.dg/pr48784-2.c: New test.
        * gcc.dg/pr56341-1.c: New test.
        * gcc.dg/pr56341-2.c: New test.
        * gcc.dg/pr56997-1.c: New test.
        * gcc.dg/pr56997-2.c: New test.
        * gcc.dg/pr56997-3.c: New test.

2013-12-11  Bernd Edlinger  <bernd.edlinger@hotmail.de>
             Sandra Loosemore  <sandra@codesourcery.com>

        PR middle-end/23623
        PR middle-end/48784
        PR middle-end/56341
        PR middle-end/56997
        * expmed.c (strict_volatile_bitfield_p): Add bitregion_start
        and bitregion_end parameters.  Test for compliance with C++
        memory model.
        (store_bit_field): Adjust call to strict_volatile_bitfield_p.
        Add fallback logic for cases where -fstrict-volatile-bitfields
        is supposed to apply, but cannot.
        (extract_bit_field): Likewise. Use narrow_bit_field_mem and
        extract_fixed_bit_field_1 to do the extraction.
        (extract_fixed_bit_field): Revert to previous mode selection
algorithm.
        Call extract_fixed_bit_field_1 to do the real work.
        (extract_fixed_bit_field_1): New function.

testsuite:
        * gcc.dg/pr23623.c: Update to test interaction with C++
        memory model.

2013-12-11  Bernd Edlinger  <bernd.edlinger@hotmail.de>

        PR middle-end/59134
        * expmed.c (store_bit_field): Use narrow_bit_field_mem and
        store_fixed_bit_field_1 for -fstrict-volatile-bitfields.
        (store_fixed_bit_field): Split up.  Call store_fixed_bit_field_1
        to do the real work.
        (store_fixed_bit_field_1): New function. 
        (store_split_bit_field): Limit the unit size to the memory mode
size,
        to prevent recursion.

testsuite:
        * gcc.c-torture/compile/pr59134.c: New test.
        * gnat.dg/misaligned_volatile.adb: New test.

Added:
   
branches/ARM/embedded-4_8-branch/gcc/testsuite/gcc.c-torture/compile/pr59134.c
    branches/ARM/embedded-4_8-branch/gcc/testsuite/gcc.dg/pr23623.c
    branches/ARM/embedded-4_8-branch/gcc/testsuite/gcc.dg/pr48784-1.c
    branches/ARM/embedded-4_8-branch/gcc/testsuite/gcc.dg/pr48784-2.c
    branches/ARM/embedded-4_8-branch/gcc/testsuite/gcc.dg/pr56341-1.c
    branches/ARM/embedded-4_8-branch/gcc/testsuite/gcc.dg/pr56341-2.c
    branches/ARM/embedded-4_8-branch/gcc/testsuite/gcc.dg/pr56997-1.c
    branches/ARM/embedded-4_8-branch/gcc/testsuite/gcc.dg/pr56997-2.c
    branches/ARM/embedded-4_8-branch/gcc/testsuite/gcc.dg/pr56997-3.c
   
branches/ARM/embedded-4_8-branch/gcc/testsuite/gnat.dg/misaligned_volatile.adb
Modified:
    branches/ARM/embedded-4_8-branch/gcc/ChangeLog.arm
    branches/ARM/embedded-4_8-branch/gcc/calls.c
    branches/ARM/embedded-4_8-branch/gcc/config/tilegx/tilegx.c
    branches/ARM/embedded-4_8-branch/gcc/config/tilepro/tilepro.c
    branches/ARM/embedded-4_8-branch/gcc/doc/invoke.texi
    branches/ARM/embedded-4_8-branch/gcc/expmed.c
    branches/ARM/embedded-4_8-branch/gcc/expr.c
    branches/ARM/embedded-4_8-branch/gcc/expr.h
    branches/ARM/embedded-4_8-branch/gcc/testsuite/ChangeLog.arm