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* [Bug middle-end/62103] New: Incorrect folding of bitfield in a union on big endian targets
@ 2014-08-12  2:14 thopre01 at gcc dot gnu.org
  2014-08-12  2:16 ` [Bug middle-end/62103] " thopre01 at gcc dot gnu.org
                   ` (11 more replies)
  0 siblings, 12 replies; 13+ messages in thread
From: thopre01 at gcc dot gnu.org @ 2014-08-12  2:14 UTC (permalink / raw)
  To: gcc-bugs

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=62103

            Bug ID: 62103
           Summary: Incorrect folding of bitfield in a union on big endian
                    targets
           Product: gcc
           Version: 4.8.3
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: middle-end
          Assignee: unassigned at gcc dot gnu.org
          Reporter: thopre01 at gcc dot gnu.org

Folding of bitfield in a union is incorrect on big endian targets. Consider the
testcase given in attachment, u.b would be folded to 0x45678 instead of
0x12345.


^ permalink raw reply	[flat|nested] 13+ messages in thread
* [Bug middle-end/62103] Incorrect folding of bitfield in a union on big endian targets
  2014-08-12  2:14 [Bug middle-end/62103] New: Incorrect folding of bitfield in a union on big endian targets thopre01 at gcc dot gnu.org
@ 2014-08-12  2:16 ` thopre01 at gcc dot gnu.org
  2014-08-12  2:21 ` thopre01 at gcc dot gnu.org
                   ` (10 subsequent siblings)
  11 siblings, 0 replies; 13+ messages in thread
From: thopre01 at gcc dot gnu.org @ 2014-08-12  2:16 UTC (permalink / raw)
  To: gcc-bugs

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=62103

thopre01 at gcc dot gnu.org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |ASSIGNED
   Last reconfirmed|                            |2014-08-12
           Assignee|unassigned at gcc dot gnu.org      |thopre01 at gcc dot gnu.org
     Ever confirmed|0                           |1

--- Comment #1 from thopre01 at gcc dot gnu.org ---
Created attachment 33298
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=33298&action=edit
Testcase: bitfield in a union


^ permalink raw reply	[flat|nested] 13+ messages in thread
* [Bug middle-end/62103] Incorrect folding of bitfield in a union on big endian targets
  2014-08-12  2:14 [Bug middle-end/62103] New: Incorrect folding of bitfield in a union on big endian targets thopre01 at gcc dot gnu.org
  2014-08-12  2:16 ` [Bug middle-end/62103] " thopre01 at gcc dot gnu.org
@ 2014-08-12  2:21 ` thopre01 at gcc dot gnu.org
  2014-08-12  2:37 ` thopre01 at gcc dot gnu.org
                   ` (9 subsequent siblings)
  11 siblings, 0 replies; 13+ messages in thread
From: thopre01 at gcc dot gnu.org @ 2014-08-12  2:21 UTC (permalink / raw)
  To: gcc-bugs

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=62103

--- Comment #2 from thopre01 at gcc dot gnu.org ---
I forgot to mention the flag to use: -O1 and whatever flag is necessary to
select a big endian target (for instance -mbig-endian if the target is arm
little endian by default).


^ permalink raw reply	[flat|nested] 13+ messages in thread
* [Bug middle-end/62103] Incorrect folding of bitfield in a union on big endian targets
  2014-08-12  2:14 [Bug middle-end/62103] New: Incorrect folding of bitfield in a union on big endian targets thopre01 at gcc dot gnu.org
  2014-08-12  2:16 ` [Bug middle-end/62103] " thopre01 at gcc dot gnu.org
  2014-08-12  2:21 ` thopre01 at gcc dot gnu.org
@ 2014-08-12  2:37 ` thopre01 at gcc dot gnu.org
  2014-08-14  6:17 ` thopre01 at gcc dot gnu.org
                   ` (8 subsequent siblings)
  11 siblings, 0 replies; 13+ messages in thread
From: thopre01 at gcc dot gnu.org @ 2014-08-12  2:37 UTC (permalink / raw)
  To: gcc-bugs

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=62103

--- Comment #3 from thopre01 at gcc dot gnu.org ---
Author: thopre01
Date: Tue Aug 12 02:36:37 2014
New Revision: 213846

URL: https://gcc.gnu.org/viewcvs?rev=213846&root=gcc&view=rev
Log:
2014-08-12  Thomas Preud'homme  <thomas.preudhomme@arm.com>

    gcc/
    PR middle-end/62103
    * gimple-fold.c (fold_ctor_reference): Don't fold in presence of
    bitfields, that is when size doesn't match the size of type or the
    size of the constructor.

    gcc/testsuite/
    PR middle-end/62103
    * gcc.c-torture/execute/bitfld-6.c: New test.

Added:
    trunk/gcc/testsuite/gcc.c-torture/execute/bitfld-6.c
Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/gimple-fold.c
    trunk/gcc/testsuite/ChangeLog


^ permalink raw reply	[flat|nested] 13+ messages in thread
* [Bug middle-end/62103] Incorrect folding of bitfield in a union on big endian targets
  2014-08-12  2:14 [Bug middle-end/62103] New: Incorrect folding of bitfield in a union on big endian targets thopre01 at gcc dot gnu.org
                   ` (2 preceding siblings ...)
  2014-08-12  2:37 ` thopre01 at gcc dot gnu.org
@ 2014-08-14  6:17 ` thopre01 at gcc dot gnu.org
  2014-12-17 11:52 ` thopre01 at gcc dot gnu.org
                   ` (7 subsequent siblings)
  11 siblings, 0 replies; 13+ messages in thread
From: thopre01 at gcc dot gnu.org @ 2014-08-14  6:17 UTC (permalink / raw)
  To: gcc-bugs

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=62103

--- Comment #5 from thopre01 at gcc dot gnu.org ---
Author: thopre01
Date: Thu Aug 14 06:16:56 2014
New Revision: 213941

URL: https://gcc.gnu.org/viewcvs?rev=213941&root=gcc&view=rev
Log:
2014-08-14  Thomas Preud'homme  <thomas.preudhomme@arm.com>

    Backport from mainline
    2014-08-12  Thomas Preud'homme  <thomas.preudhomme@arm.com>

    gcc/
    PR middle-end/62103
    * gimple-fold.c (fold_ctor_reference): Don't fold in presence of
    bitfields, that is when size doesn't match the size of type or the
    size of the constructor.

    gcc/testsuite/
    PR middle-end/62103
    * gcc.c-torture/execute/bitfld-6.c: New test.

Added:
    branches/gcc-4_9-branch/gcc/testsuite/gcc.c-torture/execute/bitfld-6.c
Modified:
    branches/gcc-4_9-branch/gcc/ChangeLog
    branches/gcc-4_9-branch/gcc/gimple-fold.c
    branches/gcc-4_9-branch/gcc/testsuite/ChangeLog


^ permalink raw reply	[flat|nested] 13+ messages in thread
* [Bug middle-end/62103] Incorrect folding of bitfield in a union on big endian targets
  2014-08-12  2:14 [Bug middle-end/62103] New: Incorrect folding of bitfield in a union on big endian targets thopre01 at gcc dot gnu.org
                   ` (3 preceding siblings ...)
  2014-08-14  6:17 ` thopre01 at gcc dot gnu.org
@ 2014-12-17 11:52 ` thopre01 at gcc dot gnu.org
  2015-01-27 22:31 ` jiwang at gcc dot gnu.org
                   ` (6 subsequent siblings)
  11 siblings, 0 replies; 13+ messages in thread
From: thopre01 at gcc dot gnu.org @ 2014-12-17 11:52 UTC (permalink / raw)
  To: gcc-bugs

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=62103

thopre01 at gcc dot gnu.org changed:

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

--- Comment #6 from thopre01 at gcc dot gnu.org ---
Fixed in all the branch currently supported


^ permalink raw reply	[flat|nested] 13+ messages in thread
* [Bug middle-end/62103] Incorrect folding of bitfield in a union on big endian targets
  2014-08-12  2:14 [Bug middle-end/62103] New: Incorrect folding of bitfield in a union on big endian targets thopre01 at gcc dot gnu.org
                   ` (4 preceding siblings ...)
  2014-12-17 11:52 ` thopre01 at gcc dot gnu.org
@ 2015-01-27 22:31 ` jiwang at gcc dot gnu.org
  2015-01-27 22:32 ` jiwang at gcc dot gnu.org
                   ` (5 subsequent siblings)
  11 siblings, 0 replies; 13+ messages in thread
From: jiwang at gcc dot gnu.org @ 2015-01-27 22:31 UTC (permalink / raw)
  To: gcc-bugs

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=62103

Jiong Wang <jiwang at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jiwang at gcc dot gnu.org

--- Comment #7 from Jiong Wang <jiwang at gcc dot gnu.org> ---
*** Bug 64822 has been marked as a duplicate of this bug. ***


^ permalink raw reply	[flat|nested] 13+ messages in thread
* [Bug middle-end/62103] Incorrect folding of bitfield in a union on big endian targets
  2014-08-12  2:14 [Bug middle-end/62103] New: Incorrect folding of bitfield in a union on big endian targets thopre01 at gcc dot gnu.org
                   ` (5 preceding siblings ...)
  2015-01-27 22:31 ` jiwang at gcc dot gnu.org
@ 2015-01-27 22:32 ` jiwang at gcc dot gnu.org
  2015-01-27 22:34 ` jiwang at gcc dot gnu.org
                   ` (4 subsequent siblings)
  11 siblings, 0 replies; 13+ messages in thread
From: jiwang at gcc dot gnu.org @ 2015-01-27 22:32 UTC (permalink / raw)
  To: gcc-bugs

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=62103

--- Comment #8 from Jiong Wang <jiwang at gcc dot gnu.org> ---
looks like this fix is too conservative. it will disable const fold for
bit-field completely. for bitfld-6/little-endian, previously, we can generated

main:
        mov     w0, 0
        ret

while after this patch, we always load from memory. any specific reason for
this?

shouldn't we fix the code to let big-endian get correct folded constant?


^ permalink raw reply	[flat|nested] 13+ messages in thread
* [Bug middle-end/62103] Incorrect folding of bitfield in a union on big endian targets
  2014-08-12  2:14 [Bug middle-end/62103] New: Incorrect folding of bitfield in a union on big endian targets thopre01 at gcc dot gnu.org
                   ` (6 preceding siblings ...)
  2015-01-27 22:32 ` jiwang at gcc dot gnu.org
@ 2015-01-27 22:34 ` jiwang at gcc dot gnu.org
  2015-01-28  2:58 ` thopre01 at gcc dot gnu.org
                   ` (3 subsequent siblings)
  11 siblings, 0 replies; 13+ messages in thread
From: jiwang at gcc dot gnu.org @ 2015-01-27 22:34 UTC (permalink / raw)
  To: gcc-bugs

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=62103

Jiong Wang <jiwang at gcc dot gnu.org> changed:

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

--- Comment #9 from Jiong Wang <jiwang at gcc dot gnu.org> ---
(In reply to Jiong Wang from comment #8)
> 
> while after this patch, we always load from memory. any specific reason for
> this?
> 
> shouldn't we fix the code to let big-endian get correct folded constant?

and similar bug still exist as 64822


^ permalink raw reply	[flat|nested] 13+ messages in thread
* [Bug middle-end/62103] Incorrect folding of bitfield in a union on big endian targets
  2014-08-12  2:14 [Bug middle-end/62103] New: Incorrect folding of bitfield in a union on big endian targets thopre01 at gcc dot gnu.org
                   ` (7 preceding siblings ...)
  2015-01-27 22:34 ` jiwang at gcc dot gnu.org
@ 2015-01-28  2:58 ` thopre01 at gcc dot gnu.org
  2015-01-28  9:30 ` thopre01 at gcc dot gnu.org
                   ` (2 subsequent siblings)
  11 siblings, 0 replies; 13+ messages in thread
From: thopre01 at gcc dot gnu.org @ 2015-01-28  2:58 UTC (permalink / raw)
  To: gcc-bugs

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=62103

--- Comment #10 from Thomas Preud'homme <thopre01 at gcc dot gnu.org> ---
(In reply to Jiong Wang from comment #8)
> looks like this fix is too conservative. it will disable const fold for
> bit-field completely. for bitfld-6/little-endian, previously, we can
> generated
> 
> main:
>         mov     w0, 0
>         ret
> 
> while after this patch, we always load from memory. any specific reason for
> this?
> 
> shouldn't we fix the code to let big-endian get correct folded constant?

We only disable const folding for initialization of bitfields in a union. The
rationale was that the fix was much simpler (and could thus be backported) and
accessing a bitfield in a union that was initialized with a constant rare
enough that it wasn't worth the extra effort anyway. If this latter assumption
proves to be wrong I have the beginning of a patch that make
double_int::from_buffer and wi::from_buffer work at the bit level. It would
need to be extended to do the same to ::to_buffer.


^ permalink raw reply	[flat|nested] 13+ messages in thread
* [Bug middle-end/62103] Incorrect folding of bitfield in a union on big endian targets
  2014-08-12  2:14 [Bug middle-end/62103] New: Incorrect folding of bitfield in a union on big endian targets thopre01 at gcc dot gnu.org
                   ` (8 preceding siblings ...)
  2015-01-28  2:58 ` thopre01 at gcc dot gnu.org
@ 2015-01-28  9:30 ` thopre01 at gcc dot gnu.org
  2015-02-04  8:23 ` thopre01 at gcc dot gnu.org
  2015-05-18  2:03 ` thopre01 at gcc dot gnu.org
  11 siblings, 0 replies; 13+ messages in thread
From: thopre01 at gcc dot gnu.org @ 2015-01-28  9:30 UTC (permalink / raw)
  To: gcc-bugs

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=62103

--- Comment #11 from Thomas Preud'homme <thopre01 at gcc dot gnu.org> ---
Ok, I have a local fix. The existing testcase didn't catch it because the
precision of the bitfield is not a multiple of CHAR_BITS.


^ permalink raw reply	[flat|nested] 13+ messages in thread
* [Bug middle-end/62103] Incorrect folding of bitfield in a union on big endian targets
  2014-08-12  2:14 [Bug middle-end/62103] New: Incorrect folding of bitfield in a union on big endian targets thopre01 at gcc dot gnu.org
                   ` (9 preceding siblings ...)
  2015-01-28  9:30 ` thopre01 at gcc dot gnu.org
@ 2015-02-04  8:23 ` thopre01 at gcc dot gnu.org
  2015-05-18  2:03 ` thopre01 at gcc dot gnu.org
  11 siblings, 0 replies; 13+ messages in thread
From: thopre01 at gcc dot gnu.org @ 2015-02-04  8:23 UTC (permalink / raw)
  To: gcc-bugs

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=62103

--- Comment #12 from Thomas Preud'homme <thopre01 at gcc dot gnu.org> ---
Author: thopre01
Date: Wed Feb  4 08:22:45 2015
New Revision: 220390

URL: https://gcc.gnu.org/viewcvs?rev=220390&root=gcc&view=rev
Log:
2015-02-04  Thomas Preud'homme  <thomas.preudhomme@arm.com>

    gcc/
    PR middle-end/62103
    * tree-ssa-sccvn.c (fully_constant_vn_reference_p): Use TYPE_PRECISION
    to compute size of referenced value in the constant case.

    gcc/testsuite/
    PR middle-end/62103
    * gcc.c-torture/execute/bitfld-7.c: New test adapted from bitfld-6.c
    to use 24 bits for bitfield b.

Added:
    trunk/gcc/testsuite/gcc.c-torture/execute/bitfld-7.c
Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/testsuite/ChangeLog
    trunk/gcc/tree-ssa-sccvn.c


^ permalink raw reply	[flat|nested] 13+ messages in thread
* [Bug middle-end/62103] Incorrect folding of bitfield in a union on big endian targets
  2014-08-12  2:14 [Bug middle-end/62103] New: Incorrect folding of bitfield in a union on big endian targets thopre01 at gcc dot gnu.org
                   ` (10 preceding siblings ...)
  2015-02-04  8:23 ` thopre01 at gcc dot gnu.org
@ 2015-05-18  2:03 ` thopre01 at gcc dot gnu.org
  11 siblings, 0 replies; 13+ messages in thread
From: thopre01 at gcc dot gnu.org @ 2015-05-18  2:03 UTC (permalink / raw)
  To: gcc-bugs

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=62103

Thomas Preud'homme <thopre01 at gcc dot gnu.org> changed:

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

--- Comment #13 from Thomas Preud'homme <thopre01 at gcc dot gnu.org> ---
Fixed in all maintained branches.


^ permalink raw reply	[flat|nested] 13+ messages in thread
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2014-08-12  2:16 ` [Bug middle-end/62103] " thopre01 at gcc dot gnu.org
2014-08-12  2:21 ` thopre01 at gcc dot gnu.org
2014-08-12  2:37 ` thopre01 at gcc dot gnu.org
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2014-12-17 11:52 ` thopre01 at gcc dot gnu.org
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