[PATCH][4.8] Backport strict-volatile-bitfields fixes to 4.8

["Joey Ye" <joey dot ye at arm dot com>]

4.8 has a number of strict-volatile-bitfields issues that can be fixed by
following patches. 
trunk@205899, 205898, 205897, 205896, 203003

Tested on x86_64 and arm without regression.

OK to 4.8?

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.

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