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* [Bug middle-end/23623] volatile keyword changes bitfield access size from 32bit to 8bit
[not found] <bug-23623-4@http.gcc.gnu.org/bugzilla/>
@ 2013-06-08 19:57 ` sandra at codesourcery dot com
2013-06-14 2:59 ` sandra at codesourcery dot com
` (4 subsequent siblings)
5 siblings, 0 replies; 23+ messages in thread
From: sandra at codesourcery dot com @ 2013-06-08 19:57 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23623
Sandra Loosemore <sandra at codesourcery dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |sandra at codesourcery dot com
--- Comment #15 from Sandra Loosemore <sandra at codesourcery dot com> ---
This bug regressed sometime around GCC 4.7, when the C++ bitfield range support
was added. I'm working on a fix that makes it work again in conjunction with
-fstrict-volatile-bitfields.
^ permalink raw reply [flat|nested] 23+ messages in thread
* [Bug middle-end/23623] volatile keyword changes bitfield access size from 32bit to 8bit
[not found] <bug-23623-4@http.gcc.gnu.org/bugzilla/>
2013-06-08 19:57 ` [Bug middle-end/23623] volatile keyword changes bitfield access size from 32bit to 8bit sandra at codesourcery dot com
@ 2013-06-14 2:59 ` sandra at codesourcery dot com
2013-10-07 15:40 ` sandra at codesourcery dot com
` (3 subsequent siblings)
5 siblings, 0 replies; 23+ messages in thread
From: sandra at codesourcery dot com @ 2013-06-14 2:59 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23623
--- Comment #16 from Sandra Loosemore <sandra at codesourcery dot com> ---
Patch that fixes regression posted here:
http://gcc.gnu.org/ml/gcc-patches/2013-06/msg00750.html
^ permalink raw reply [flat|nested] 23+ messages in thread
* [Bug middle-end/23623] volatile keyword changes bitfield access size from 32bit to 8bit
[not found] <bug-23623-4@http.gcc.gnu.org/bugzilla/>
2013-06-08 19:57 ` [Bug middle-end/23623] volatile keyword changes bitfield access size from 32bit to 8bit sandra at codesourcery dot com
2013-06-14 2:59 ` sandra at codesourcery dot com
@ 2013-10-07 15:40 ` sandra at codesourcery dot com
2013-12-11 16:50 ` edlinger at gcc dot gnu.org
` (2 subsequent siblings)
5 siblings, 0 replies; 23+ messages in thread
From: sandra at codesourcery dot com @ 2013-10-07 15:40 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23623
--- Comment #17 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. :-(
^ permalink raw reply [flat|nested] 23+ messages in thread
* [Bug middle-end/23623] volatile keyword changes bitfield access size from 32bit to 8bit
[not found] <bug-23623-4@http.gcc.gnu.org/bugzilla/>
` (2 preceding siblings ...)
2013-10-07 15:40 ` sandra at codesourcery dot com
@ 2013-12-11 16:50 ` edlinger at gcc dot gnu.org
2013-12-11 16:59 ` edlinger at gcc dot gnu.org
2014-02-27 7:28 ` jye2 at gcc dot gnu.org
5 siblings, 0 replies; 23+ messages in thread
From: edlinger at gcc dot gnu.org @ 2013-12-11 16:50 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23623
--- Comment #18 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
^ permalink raw reply [flat|nested] 23+ messages in thread
* [Bug middle-end/23623] volatile keyword changes bitfield access size from 32bit to 8bit
[not found] <bug-23623-4@http.gcc.gnu.org/bugzilla/>
` (3 preceding siblings ...)
2013-12-11 16:50 ` edlinger at gcc dot gnu.org
@ 2013-12-11 16:59 ` edlinger at gcc dot gnu.org
2014-02-27 7:28 ` jye2 at gcc dot gnu.org
5 siblings, 0 replies; 23+ messages in thread
From: edlinger at gcc dot gnu.org @ 2013-12-11 16:59 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23623
--- Comment #19 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
^ permalink raw reply [flat|nested] 23+ messages in thread
* [Bug middle-end/23623] volatile keyword changes bitfield access size from 32bit to 8bit
[not found] <bug-23623-4@http.gcc.gnu.org/bugzilla/>
` (4 preceding siblings ...)
2013-12-11 16:59 ` edlinger at gcc dot gnu.org
@ 2014-02-27 7:28 ` jye2 at gcc dot gnu.org
5 siblings, 0 replies; 23+ messages in thread
From: jye2 at gcc dot gnu.org @ 2014-02-27 7:28 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23623
--- Comment #20 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
^ permalink raw reply [flat|nested] 23+ messages in thread
* [Bug middle-end/23623] volatile keyword changes bitfield access size from 32bit to 8bit
[not found] <bug-23623-11259@http.gcc.gnu.org/bugzilla/>
` (6 preceding siblings ...)
2009-01-13 10:42 ` frikkie at zitera dot co dot za
@ 2009-01-13 15:52 ` frikkie at zitera dot co dot za
7 siblings, 0 replies; 23+ messages in thread
From: frikkie at zitera dot co dot za @ 2009-01-13 15:52 UTC (permalink / raw)
To: gcc-bugs
------- Comment #14 from frikkie at zitera dot co dot za 2009-01-13 15:51 -------
Created an attachment (id=17087)
--> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=17087&action=view)
GCC 4.3.2 patch for volatile bitfields
The following patches help to honour the container type of the volatile
bitfield when the GCC internal: TARGET_NARROW_VOLATILE_BITFIELD is false.
The patch is for GCC 4.3.2
Included in the tgz-file is the whole project, GCC patches and disassembly for
the application when using the original GCC 4.3.2 source and the patched
source.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23623
^ permalink raw reply [flat|nested] 23+ messages in thread
* [Bug middle-end/23623] volatile keyword changes bitfield access size from 32bit to 8bit
[not found] <bug-23623-11259@http.gcc.gnu.org/bugzilla/>
` (5 preceding siblings ...)
2009-01-13 10:12 ` frikkie at zitera dot co dot za
@ 2009-01-13 10:42 ` frikkie at zitera dot co dot za
2009-01-13 15:52 ` frikkie at zitera dot co dot za
7 siblings, 0 replies; 23+ messages in thread
From: frikkie at zitera dot co dot za @ 2009-01-13 10:42 UTC (permalink / raw)
To: gcc-bugs
------- Comment #13 from frikkie at zitera dot co dot za 2009-01-13 10:42 -------
Please note: The patch was for GCC 4.4.0, not GCC 4.0.0 as mentioned in the
previous post.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23623
^ permalink raw reply [flat|nested] 23+ messages in thread
* [Bug middle-end/23623] volatile keyword changes bitfield access size from 32bit to 8bit
[not found] <bug-23623-11259@http.gcc.gnu.org/bugzilla/>
` (4 preceding siblings ...)
2006-08-02 11:30 ` jason dot morgan at vpnsolutions dot uk dot com
@ 2009-01-13 10:12 ` frikkie at zitera dot co dot za
2009-01-13 10:42 ` frikkie at zitera dot co dot za
2009-01-13 15:52 ` frikkie at zitera dot co dot za
7 siblings, 0 replies; 23+ messages in thread
From: frikkie at zitera dot co dot za @ 2009-01-13 10:12 UTC (permalink / raw)
To: gcc-bugs
------- Comment #12 from frikkie at zitera dot co dot za 2009-01-13 10:12 -------
Created an attachment (id=17085)
--> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=17085&action=view)
patch_for_volatile_bitfields_gcc400.tgz
The following patches help to honour the container type of the volatile
bitfield when the GCC internal: TARGET_NARROW_VOLATILE_BITFIELD is false.
The patch is for GCC 4.0.0
Included in the tgz-file is the disassembly for the application: main.c, with
the original GCC 4.0.0 source and the patched source.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23623
^ permalink raw reply [flat|nested] 23+ messages in thread
* [Bug middle-end/23623] volatile keyword changes bitfield access size from 32bit to 8bit
[not found] <bug-23623-11259@http.gcc.gnu.org/bugzilla/>
` (3 preceding siblings ...)
2006-05-16 17:15 ` pinskia at gcc dot gnu dot org
@ 2006-08-02 11:30 ` jason dot morgan at vpnsolutions dot uk dot com
2009-01-13 10:12 ` frikkie at zitera dot co dot za
` (2 subsequent siblings)
7 siblings, 0 replies; 23+ messages in thread
From: jason dot morgan at vpnsolutions dot uk dot com @ 2006-08-02 11:30 UTC (permalink / raw)
To: gcc-bugs
------- Comment #11 from jason dot morgan at vpnsolutions dot uk dot com 2006-08-02 11:30 -------
*** Bug 28568 has been marked as a duplicate of this bug. ***
--
jason dot morgan at vpnsolutions dot uk dot com changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |jason dot morgan at
| |vpnsolutions dot uk dot com
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23623
^ permalink raw reply [flat|nested] 23+ messages in thread
* [Bug middle-end/23623] volatile keyword changes bitfield access size from 32bit to 8bit
[not found] <bug-23623-11259@http.gcc.gnu.org/bugzilla/>
` (2 preceding siblings ...)
2006-03-29 17:44 ` pbrook at gcc dot gnu dot org
@ 2006-05-16 17:15 ` pinskia at gcc dot gnu dot org
2006-08-02 11:30 ` jason dot morgan at vpnsolutions dot uk dot com
` (3 subsequent siblings)
7 siblings, 0 replies; 23+ messages in thread
From: pinskia at gcc dot gnu dot org @ 2006-05-16 17:15 UTC (permalink / raw)
To: gcc-bugs
--
pinskia at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
Target Milestone|--- |4.2.0
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23623
^ permalink raw reply [flat|nested] 23+ messages in thread
* [Bug middle-end/23623] volatile keyword changes bitfield access size from 32bit to 8bit
[not found] <bug-23623-11259@http.gcc.gnu.org/bugzilla/>
2006-03-28 18:03 ` pbrook at gcc dot gnu dot org
2006-03-29 15:22 ` pbrook at gcc dot gnu dot org
@ 2006-03-29 17:44 ` pbrook at gcc dot gnu dot org
2006-05-16 17:15 ` pinskia at gcc dot gnu dot org
` (4 subsequent siblings)
7 siblings, 0 replies; 23+ messages in thread
From: pbrook at gcc dot gnu dot org @ 2006-03-29 17:44 UTC (permalink / raw)
To: gcc-bugs
------- Comment #10 from pbrook at gcc dot gnu dot org 2006-03-29 17:44 -------
Should be fixed now.
--
pbrook at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |RESOLVED
Resolution| |FIXED
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23623
^ permalink raw reply [flat|nested] 23+ messages in thread
* [Bug middle-end/23623] volatile keyword changes bitfield access size from 32bit to 8bit
[not found] <bug-23623-11259@http.gcc.gnu.org/bugzilla/>
2006-03-28 18:03 ` pbrook at gcc dot gnu dot org
@ 2006-03-29 15:22 ` pbrook at gcc dot gnu dot org
2006-03-29 17:44 ` pbrook at gcc dot gnu dot org
` (5 subsequent siblings)
7 siblings, 0 replies; 23+ messages in thread
From: pbrook at gcc dot gnu dot org @ 2006-03-29 15:22 UTC (permalink / raw)
To: gcc-bugs
------- Comment #9 from pbrook at gcc dot gnu dot org 2006-03-29 15:21 -------
Subject: Bug 23623
Author: pbrook
Date: Wed Mar 29 15:21:13 2006
New Revision: 112493
URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=112493
Log:
2006-03-29 Paul Brook <paul@codesourcery.com>
PR middle-end/23623
* targhooks.c (default_narrow_bitfield): New fuction.
* targhooks.h (default_narrow_bitfield): add prototype.
* target.h (gcc_target): Add narrow_volatile_bitfield.
* target-def.h (TARGET_NARROW_VOLATILE_BITFIELD): Define.
* stor-layout.c (get_best_mode): Use targetm.narrow_volatile_bitfield.
* doc/tm.texi: Document TARGET_NARROW_VOLATILE_BITFIELDS.
* config/arm/arm.c (TARGET_NARROW_VOLATILE_BITFIELD): Define.
Modified:
trunk/gcc/ChangeLog
trunk/gcc/config/arm/arm.c
trunk/gcc/doc/tm.texi
trunk/gcc/stor-layout.c
trunk/gcc/target-def.h
trunk/gcc/target.h
trunk/gcc/targhooks.c
trunk/gcc/targhooks.h
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23623
^ permalink raw reply [flat|nested] 23+ messages in thread
* [Bug middle-end/23623] volatile keyword changes bitfield access size from 32bit to 8bit
[not found] <bug-23623-11259@http.gcc.gnu.org/bugzilla/>
@ 2006-03-28 18:03 ` pbrook at gcc dot gnu dot org
2006-03-29 15:22 ` pbrook at gcc dot gnu dot org
` (6 subsequent siblings)
7 siblings, 0 replies; 23+ messages in thread
From: pbrook at gcc dot gnu dot org @ 2006-03-28 18:03 UTC (permalink / raw)
To: gcc-bugs
------- Comment #8 from pbrook at gcc dot gnu dot org 2006-03-28 18:03 -------
Subject: Bug 23623
Author: pbrook
Date: Tue Mar 28 18:03:06 2006
New Revision: 112460
URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=112460
Log:
2006-03-28 Paul Brook <paul@codesourcery.com>
PR middle-end/23623
* gcc/targhooks.c (default_narrow_bitfield): New fuction.
* gcc/targhooks.h (default_narrow_bitfield): add prototype.
* gcc/target-def.h (TARGET_NARROW_VOLATILE_BITFIELD): Define.
* gcc/doc/tm.texi: Document TARGET_NARROW_VOLATILE_BITFIELDS.
* gcc/config/arm/arm.c (TARGET_NARROW_VOLATILE_BITFIELD): Define.
Modified:
branches/csl/sourcerygxx-4_1/ChangeLog.csl
branches/csl/sourcerygxx-4_1/gcc/config/arm/arm.c
branches/csl/sourcerygxx-4_1/gcc/doc/tm.texi
branches/csl/sourcerygxx-4_1/gcc/stor-layout.c
branches/csl/sourcerygxx-4_1/gcc/target-def.h
branches/csl/sourcerygxx-4_1/gcc/target.h
branches/csl/sourcerygxx-4_1/gcc/targhooks.c
branches/csl/sourcerygxx-4_1/gcc/targhooks.h
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23623
^ permalink raw reply [flat|nested] 23+ messages in thread
* [Bug middle-end/23623] volatile keyword changes bitfield access size from 32bit to 8bit
2005-08-29 14:11 [Bug c/23623] New: " m dot reszat at kostal dot com
` (7 preceding siblings ...)
2005-08-30 14:06 ` rearnsha at gcc dot gnu dot org
@ 2005-09-08 15:12 ` m dot reszat at kostal dot com
8 siblings, 0 replies; 23+ messages in thread
From: m dot reszat at kostal dot com @ 2005-09-08 15:12 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From m dot reszat at kostal dot com 2005-09-08 15:12 -------
(In reply to comment #6)
> (In reply to comment #5)
> > I will try and dig up the EABI for PowerPC
> > > Note this also happens on ARM where (in the EABI) it is definitely a bug
None of the documents I found makes a statement as clear as the ARM EABI does.
Can someone point me to the source file where the "narrowing" is done, to maybe
simply "comment it out"?; I don't feel capable of providing a real fix, see
below, but I also don't want to rewrite large portions of my code when migrating
to GCC.
Having given more thought to the problem, isn't the "narrowing" an optimization
which should not be a fixed property of the compiler, given that even for the
same type of machine ("target") there can exist various different memory
interfaces? Hence, shouldn't it be an optimization option, "on" by default to be
backwards compatible?
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23623
^ permalink raw reply [flat|nested] 23+ messages in thread
* [Bug middle-end/23623] volatile keyword changes bitfield access size from 32bit to 8bit
2005-08-29 14:11 [Bug c/23623] New: " m dot reszat at kostal dot com
` (6 preceding siblings ...)
2005-08-30 13:42 ` m dot reszat at kostal dot com
@ 2005-08-30 14:06 ` rearnsha at gcc dot gnu dot org
2005-09-08 15:12 ` m dot reszat at kostal dot com
8 siblings, 0 replies; 23+ messages in thread
From: rearnsha at gcc dot gnu dot org @ 2005-08-30 14:06 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From rearnsha at gcc dot gnu dot org 2005-08-30 14:00 -------
(In reply to comment #5)
> I will try and dig up the EABI for PowerPC, but it's not just about sticking to
> a paper. It simply does not work for me (and probably others) the way it is.
Saying that because it doesn't work for you is not really addressing the issue.
The point of specifications like this are so that they create a level playing
field for all to start from (and thus avoid 'arguments' as to which one is
correct). Ultimately, if your code doesn't work with the prescribed model, then
you have to find another way of expressing the problem.
Note, I'm not trying to judge here whether your expectations of the PPC ABI are
right or wrong, I'm trying to set the rational for having ABI specifications and
then trying to stick to them.
> I can't quite see what can be gained by minimizing access size, but not knowing
> the complete rationale (why are non-bitfields NOT minimized, e.g. volatile int x
> |= 1), how about a command line switch to let the user select?
I suspect it's historical. On a machine that can do arbitrary alignment (eg,
traditional CISC processors) then a common layout rule for a bit-field is to
place it as close as possible to the previous field such that it all fits in one
'access' (but probably multiple memory fetches -- afterall, the memory bus is
still aligned). If that access happens to be volatile, then you still don't
want the memory system to be accessed twice (even transparently) and you can
normally guarantee that by 'narrowing' the object.
For RISC processors the alignment tends to be more critical in the normal case,
so bit-fields are generally laid out with more padding. In this situation it
then makes more sense to say that the bit-field's type governs the nature of the
memory access.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23623
^ permalink raw reply [flat|nested] 23+ messages in thread
* [Bug middle-end/23623] volatile keyword changes bitfield access size from 32bit to 8bit
2005-08-29 14:11 [Bug c/23623] New: " m dot reszat at kostal dot com
` (5 preceding siblings ...)
2005-08-30 12:51 ` rearnsha at gcc dot gnu dot org
@ 2005-08-30 13:42 ` m dot reszat at kostal dot com
2005-08-30 14:06 ` rearnsha at gcc dot gnu dot org
2005-09-08 15:12 ` m dot reszat at kostal dot com
8 siblings, 0 replies; 23+ messages in thread
From: m dot reszat at kostal dot com @ 2005-08-30 13:42 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From m dot reszat at kostal dot com 2005-08-30 13:40 -------
(In reply to comment #4)
> Note this also happens on ARM where (in the EABI) it is definitely a bug
I will try and dig up the EABI for PowerPC, but it's not just about sticking to
a paper. It simply does not work for me (and probably others) the way it is. My
system traps out on me or, worce, writes garbage to the 'untouched' register
parts for some peripherals. NEC V850 and, I think, MIPS do the same.
I can't quite see what can be gained by minimizing access size, but not knowing
the complete rationale (why are non-bitfields NOT minimized, e.g. volatile int x
|= 1), how about a command line switch to let the user select?
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23623
^ permalink raw reply [flat|nested] 23+ messages in thread
* [Bug middle-end/23623] volatile keyword changes bitfield access size from 32bit to 8bit
2005-08-29 14:11 [Bug c/23623] New: " m dot reszat at kostal dot com
` (4 preceding siblings ...)
2005-08-30 12:44 ` falk at debian dot org
@ 2005-08-30 12:51 ` rearnsha at gcc dot gnu dot org
2005-08-30 13:42 ` m dot reszat at kostal dot com
` (2 subsequent siblings)
8 siblings, 0 replies; 23+ messages in thread
From: rearnsha at gcc dot gnu dot org @ 2005-08-30 12:51 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From rearnsha at gcc dot gnu dot org 2005-08-30 12:43 -------
Note this also happens on ARM where (in the EABI) it is definitely a bug becuase
the procedure call standard says it is.
Quoting from the AAPCS:
7.1.7.5 Volatile bit-fieldspreserving number and width of container accesses
When a volatile bit-field is read, its container must be read exactly once using
the access width appropriate to the type of the container.
When a volatile bit-field is written, its container must be read exactly once
and written exactly once using the access width appropriate to the type of the
container. The two accesses are not atomic.
--
What |Removed |Added
----------------------------------------------------------------------------
CC| |rearnsha at gcc dot gnu dot
| |org
Status|UNCONFIRMED |NEW
Ever Confirmed| |1
Last reconfirmed|0000-00-00 00:00:00 |2005-08-30 12:43:25
date| |
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23623
^ permalink raw reply [flat|nested] 23+ messages in thread
* [Bug middle-end/23623] volatile keyword changes bitfield access size from 32bit to 8bit
2005-08-29 14:11 [Bug c/23623] New: " m dot reszat at kostal dot com
` (3 preceding siblings ...)
2005-08-30 7:59 ` m dot reszat at kostal dot com
@ 2005-08-30 12:44 ` falk at debian dot org
2005-08-30 12:51 ` rearnsha at gcc dot gnu dot org
` (3 subsequent siblings)
8 siblings, 0 replies; 23+ messages in thread
From: falk at debian dot org @ 2005-08-30 12:44 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From falk at debian dot org 2005-08-30 12:26 -------
(In reply to comment #2)
> (In reply to comment #1)
> > (In reply to comment #0)
> When dealing with peripherals in embedded systems, the use of bitfields makes
> the code much more readable.
I can see that.
> Most (admittedly not all) modern peripherals allow the bitfield approach, but
> correct access size is a must (misalignment traps, access triggered buffering
> etc.).
I can see that too, but I don't see what it has to do with this PR.
> IMHO the compiler/code generator should always use the basic type when a
> variable is declared as volatile, i.e. volatile unsigned int ps:3; should
> enforce 32-bit-access, probably even for non-bitfields.
OK, but why? You still haven't explained. What exactly is the problem with
your code the way gcc does things currently?
> All compilers for
> embedded systems I know of act this way, so I assumed this was a bug.
The only other compiler I have around (DEC C) behaves the same way as gcc
(which is, to take the narrowest possible access that can be still done
in one instruction).
In any case, even if the current behavior isn't perfect, we would need an
extremely and utterly good reason to change it, lest we screw over lots
of users relying on the current behavior.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23623
^ permalink raw reply [flat|nested] 23+ messages in thread
* [Bug middle-end/23623] volatile keyword changes bitfield access size from 32bit to 8bit
2005-08-29 14:11 [Bug c/23623] New: " m dot reszat at kostal dot com
` (2 preceding siblings ...)
2005-08-29 21:27 ` falk at debian dot org
@ 2005-08-30 7:59 ` m dot reszat at kostal dot com
2005-08-30 12:44 ` falk at debian dot org
` (4 subsequent siblings)
8 siblings, 0 replies; 23+ messages in thread
From: m dot reszat at kostal dot com @ 2005-08-30 7:59 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From m dot reszat at kostal dot com 2005-08-30 07:43 -------
(In reply to comment #1)
> (In reply to comment #0)
>
> > Access to bf1.b is correctly done as 32-bits (lwz/stw opcodes), bf2.b is
> > accessed as 8-bits (lbz/stb opcodes). GCC3.4.3 shows the same behaviour, can't
> > go back any further. The same happens when the bitfield itself is made volatile,
> > not the whole struct.
>
> This is intentional. The idea is not to touch any more of that volatile stuff
> than absolutely needed. Why do you think it is a bug?
When dealing with peripherals in embedded systems, the use of bitfields makes
the code much more readable.
Ex.: 3 bits of a peripheral register define a timer prescaler
It can be s.th. like
#define PS_VAL_05 0x00140000
#define PS_MASK 0x001c0000
...
per_reg = (per_reg & ~PS_MASK) | PS_VAL_05;
But could be as simple as
per_reg.ps = 5;, or even per_reg.ps = func(...);
Try to set up the latter w/o bitfields and you end up
per_reg = (per_reg & ~PS_MASK) | (func(...) << PS_SHIFT);
Most (admittedly not all) modern peripherals allow the bitfield approach, but
correct access size is a must (misalignment traps, access triggered buffering
etc.).
IMHO the compiler/code generator should always use the basic type when a
variable is declared as volatile, i.e. volatile unsigned int ps:3; should
enforce 32-bit-access, probably even for non-bitfields. All compilers for
embedded systems I know of act this way, so I assumed this was a bug.
In other cases, e.g. communicating between threads through memory, access size
is not an issue and even if so, could be enforced by appropriate declaration or,
god help me, typecasting as a last resort.
Unfortunately, C does not provide a qualifier for access size enforcement,
"volatile" seems to be the closest friend. The current implementation puts me
between a rock and a hard place, as the "core volatile functionality" is needed
as well.
What do you think?
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23623
^ permalink raw reply [flat|nested] 23+ messages in thread
* [Bug middle-end/23623] volatile keyword changes bitfield access size from 32bit to 8bit
2005-08-29 14:11 [Bug c/23623] New: " m dot reszat at kostal dot com
2005-08-29 15:39 ` [Bug middle-end/23623] " pinskia at gcc dot gnu dot org
2005-08-29 16:21 ` pinskia at gcc dot gnu dot org
@ 2005-08-29 21:27 ` falk at debian dot org
2005-08-30 7:59 ` m dot reszat at kostal dot com
` (5 subsequent siblings)
8 siblings, 0 replies; 23+ messages in thread
From: falk at debian dot org @ 2005-08-29 21:27 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From falk at debian dot org 2005-08-29 21:10 -------
(In reply to comment #0)
> Access to bf1.b is correctly done as 32-bits (lwz/stw opcodes), bf2.b is
> accessed as 8-bits (lbz/stb opcodes). GCC3.4.3 shows the same behaviour, can't
> go back any further. The same happens when the bitfield itself is made volatile,
> not the whole struct.
This is intentional. The idea is not to touch any more of that volatile stuff
than absolutely needed. Why do you think it is a bug?
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23623
^ permalink raw reply [flat|nested] 23+ messages in thread
* [Bug middle-end/23623] volatile keyword changes bitfield access size from 32bit to 8bit
2005-08-29 14:11 [Bug c/23623] New: " m dot reszat at kostal dot com
2005-08-29 15:39 ` [Bug middle-end/23623] " pinskia at gcc dot gnu dot org
@ 2005-08-29 16:21 ` pinskia at gcc dot gnu dot org
2005-08-29 21:27 ` falk at debian dot org
` (6 subsequent siblings)
8 siblings, 0 replies; 23+ messages in thread
From: pinskia at gcc dot gnu dot org @ 2005-08-29 16:21 UTC (permalink / raw)
To: gcc-bugs
--
What |Removed |Added
----------------------------------------------------------------------------
Known to fail| |3.1 3.3 4.1.0 4.0.0
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23623
^ permalink raw reply [flat|nested] 23+ messages in thread
* [Bug middle-end/23623] volatile keyword changes bitfield access size from 32bit to 8bit
2005-08-29 14:11 [Bug c/23623] New: " m dot reszat at kostal dot com
@ 2005-08-29 15:39 ` pinskia at gcc dot gnu dot org
2005-08-29 16:21 ` pinskia at gcc dot gnu dot org
` (7 subsequent siblings)
8 siblings, 0 replies; 23+ messages in thread
From: pinskia at gcc dot gnu dot org @ 2005-08-29 15:39 UTC (permalink / raw)
To: gcc-bugs
--
What |Removed |Added
----------------------------------------------------------------------------
Component|c |middle-end
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23623
^ permalink raw reply [flat|nested] 23+ messages in thread
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