The cited testcase ICEs gcc 4.6/4.7/4.8/4.9 for me on sparc64-linux, another STRICT_ALIGNMENT target.  gcc 4.5 and older don't ICE.

Started with r163189.

Confirmed as a regression by Michael.

typedef struct {
  char pad;
  int arr[0];
} __attribute__((packed)) str;

str *
foo (int* src)
{
  str *s = __builtin_malloc (sizeof (str) + sizeof (int));
  s->arr[0] = 0x12345678;
  return s;
}


as said elsewhere - IMHO the mode on op0 should not be that of the
base object (QImode) but that of the access (SImode).

Author: edlinger
Date: Wed Dec 11 17:09:17 2013
New Revision: 205898

URL: http://gcc.gnu.org/viewcvs?rev=205898&root=gcc&view=rev
Log:
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:
    trunk/gcc/testsuite/gcc.c-torture/compile/pr59134.c
    trunk/gcc/testsuite/gnat.dg/misaligned_volatile.adb
Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/expmed.c
    trunk/gcc/testsuite/ChangeLog

Should be fixed by Bernd's fix on the trunk.

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