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* [Bug c/59138] New: possible packed struct miscompile
@ 2013-11-14 23:00 regehr at cs dot utah.edu
2013-11-15 9:17 ` [Bug c/59138] [4.8/4.9 Regression] " rguenth at gcc dot gnu.org
` (9 more replies)
0 siblings, 10 replies; 11+ messages in thread
From: regehr at cs dot utah.edu @ 2013-11-14 23:00 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59138
Bug ID: 59138
Summary: possible packed struct miscompile
Product: gcc
Version: 4.9.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: regehr at cs dot utah.edu
[regehr@imp test1]$ clang -O -Wall ./work17/reduce_D0DDXs/small.c ; ./a.out
0
[regehr@imp test1]$ gcc -O2 -Wall ./work17/reduce_D0DDXs/small.c ; ./a.out
0
[regehr@imp test1]$ gcc -Os -Wall ./work17/reduce_D0DDXs/small.c ; ./a.out
1
[regehr@imp test1]$ cat ./work17/reduce_D0DDXs/small.c
int printf(const char *, ...);
#pragma pack(1)
struct S0 {
int f0;
int f1;
int f2;
short f3;
};
short a = 1;
struct S0 b = { 1 }, c, d, e;
struct S0 fn1() { return c; }
void fn2() {
b = fn1();
a = 0;
d = e;
}
int main() {
fn2();
printf("%d\n", a);
return 0;
}
[regehr@imp test1]$ gcc -v
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/mnt/local/randomtest/compiler-install/gcc-r204770-install/bin/../libexec/gcc/x86_64-unknown-linux-gnu/4.9.0/lto-wrapper
Target: x86_64-unknown-linux-gnu
Configured with: /users/regehr/z/compiler-source/gcc/configure
--prefix=/users/regehr/z/compiler-install/gcc-r204770-install
--enable-languages=c,c++ --enable-multilib
Thread model: posix
gcc version 4.9.0 20131114 (experimental) (GCC)
^ permalink raw reply [flat|nested] 11+ messages in thread
* [Bug c/59138] [4.8/4.9 Regression] possible packed struct miscompile
2013-11-14 23:00 [Bug c/59138] New: possible packed struct miscompile regehr at cs dot utah.edu
@ 2013-11-15 9:17 ` rguenth at gcc dot gnu.org
2013-11-16 18:33 ` mikpelinux at gmail dot com
` (8 subsequent siblings)
9 siblings, 0 replies; 11+ messages in thread
From: rguenth at gcc dot gnu.org @ 2013-11-15 9:17 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59138
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Keywords| |wrong-code
Status|UNCONFIRMED |NEW
Last reconfirmed| |2013-11-15
Known to work| |4.7.3
Target Milestone|--- |4.8.3
Summary|possible packed struct |[4.8/4.9 Regression]
|miscompile |possible packed struct
| |miscompile
Ever confirmed|0 |1
--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
Confirmed.
^ permalink raw reply [flat|nested] 11+ messages in thread
* [Bug c/59138] [4.8/4.9 Regression] possible packed struct miscompile
2013-11-14 23:00 [Bug c/59138] New: possible packed struct miscompile regehr at cs dot utah.edu
2013-11-15 9:17 ` [Bug c/59138] [4.8/4.9 Regression] " rguenth at gcc dot gnu.org
@ 2013-11-16 18:33 ` mikpelinux at gmail dot com
2013-11-21 14:41 ` [Bug rtl-optimization/59138] " rguenth at gcc dot gnu.org
` (7 subsequent siblings)
9 siblings, 0 replies; 11+ messages in thread
From: mikpelinux at gmail dot com @ 2013-11-16 18:33 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59138
Mikael Pettersson <mikpelinux at gmail dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |mikpelinux at gmail dot com
--- Comment #2 from Mikael Pettersson <mikpelinux at gmail dot com> ---
Started with r191302, a fix for missed-optimization PR44194 "struct returned by
value generates useless stores".
^ permalink raw reply [flat|nested] 11+ messages in thread
* [Bug rtl-optimization/59138] [4.8/4.9 Regression] possible packed struct miscompile
2013-11-14 23:00 [Bug c/59138] New: possible packed struct miscompile regehr at cs dot utah.edu
2013-11-15 9:17 ` [Bug c/59138] [4.8/4.9 Regression] " rguenth at gcc dot gnu.org
2013-11-16 18:33 ` mikpelinux at gmail dot com
@ 2013-11-21 14:41 ` rguenth at gcc dot gnu.org
2013-11-21 16:27 ` ebotcazou at gcc dot gnu.org
` (6 subsequent siblings)
9 siblings, 0 replies; 11+ messages in thread
From: rguenth at gcc dot gnu.org @ 2013-11-21 14:41 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59138
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Priority|P3 |P2
CC| |ebotcazou at gcc dot gnu.org
Component|c |rtl-optimization
^ permalink raw reply [flat|nested] 11+ messages in thread
* [Bug rtl-optimization/59138] [4.8/4.9 Regression] possible packed struct miscompile
2013-11-14 23:00 [Bug c/59138] New: possible packed struct miscompile regehr at cs dot utah.edu
` (2 preceding siblings ...)
2013-11-21 14:41 ` [Bug rtl-optimization/59138] " rguenth at gcc dot gnu.org
@ 2013-11-21 16:27 ` ebotcazou at gcc dot gnu.org
2013-11-22 11:08 ` ebotcazou at gcc dot gnu.org
` (5 subsequent siblings)
9 siblings, 0 replies; 11+ messages in thread
From: ebotcazou at gcc dot gnu.org @ 2013-11-21 16:27 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59138
Eric Botcazou <ebotcazou at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |ASSIGNED
CC|ebotcazou at gcc dot gnu.org |
Assignee|unassigned at gcc dot gnu.org |ebotcazou at gcc dot gnu.org
--- Comment #3 from Eric Botcazou <ebotcazou at gcc dot gnu.org> ---
Looking into it.
^ permalink raw reply [flat|nested] 11+ messages in thread
* [Bug rtl-optimization/59138] [4.8/4.9 Regression] possible packed struct miscompile
2013-11-14 23:00 [Bug c/59138] New: possible packed struct miscompile regehr at cs dot utah.edu
` (3 preceding siblings ...)
2013-11-21 16:27 ` ebotcazou at gcc dot gnu.org
@ 2013-11-22 11:08 ` ebotcazou at gcc dot gnu.org
2013-11-22 18:30 ` ebotcazou at gcc dot gnu.org
` (4 subsequent siblings)
9 siblings, 0 replies; 11+ messages in thread
From: ebotcazou at gcc dot gnu.org @ 2013-11-22 11:08 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59138
--- Comment #4 from Eric Botcazou <ebotcazou at gcc dot gnu.org> ---
Latent issue in the alias.c machinery: output_dependence returns 0 on
(insn 21 20 22 2 (set (mem/c:DI (const:DI (plus:DI (symbol_ref:DI ("b") [flags
0x2] <var_decl 0x7ffff6e4d2f8 b>)
(const_int 8 [0x8]))) [0 +8 S8 A64])
(reg:DI 1 dx [99])) pr59138.c:20 85 {*movdi_internal}
(expr_list:REG_DEAD (reg:DI 1 dx [99])
(nil)))
(insn 22 21 23 2 (set (mem/c:HI (symbol_ref:DI ("a") [flags 0x2] <var_decl
0x7ffff6e4d260 a>) [2 a+0 S2 A16])
(const_int 0 [0])) pr59138.c:21 87 {*movhi_internal}
(nil))
because base_alias_check returns 0 for different symbols...
^ permalink raw reply [flat|nested] 11+ messages in thread
* [Bug rtl-optimization/59138] [4.8/4.9 Regression] possible packed struct miscompile
2013-11-14 23:00 [Bug c/59138] New: possible packed struct miscompile regehr at cs dot utah.edu
` (4 preceding siblings ...)
2013-11-22 11:08 ` ebotcazou at gcc dot gnu.org
@ 2013-11-22 18:30 ` ebotcazou at gcc dot gnu.org
2013-11-22 18:56 ` [Bug middle-end/59138] " ebotcazou at gcc dot gnu.org
` (3 subsequent siblings)
9 siblings, 0 replies; 11+ messages in thread
From: ebotcazou at gcc dot gnu.org @ 2013-11-22 18:30 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59138
--- Comment #5 from Eric Botcazou <ebotcazou at gcc dot gnu.org> ---
> Latent issue in the alias.c machinery: output_dependence returns 0 on
>
> (insn 21 20 22 2 (set (mem/c:DI (const:DI (plus:DI (symbol_ref:DI ("b")
> [flags 0x2] <var_decl 0x7ffff6e4d2f8 b>)
> (const_int 8 [0x8]))) [0 +8 S8 A64])
> (reg:DI 1 dx [99])) pr59138.c:20 85 {*movdi_internal}
> (expr_list:REG_DEAD (reg:DI 1 dx [99])
> (nil)))
>
> (insn 22 21 23 2 (set (mem/c:HI (symbol_ref:DI ("a") [flags 0x2] <var_decl
> 0x7ffff6e4d260 a>) [2 a+0 S2 A16])
> (const_int 0 [0])) pr59138.c:21 87 {*movhi_internal}
> (nil))
>
> because base_alias_check returns 0 for different symbols...
I guess this means that we shouldn't be accessing "a" when writing to "b" in
the first place, but get_best_mode decides otherwise. So this seems to be the
old issue with get_best_mode, visible directly on a bitfield write:
extern void abort (void);
#pragma pack(1)
struct S0 {
int f0;
int f1;
long long f2 : 48;
};
short a = 1;
struct S0 b = { 1 }, c;
long long fn1() { return c.f2; }
void fn2 (void)
{
b.f2 = fn1 ();
a = 0;
}
int main (void)
{
fn2 ();
if (a != 0)
abort ();
return 0;
}
with GCC 4.6 or earlier and presumably fixed by the implementation of the new
memory model.
^ permalink raw reply [flat|nested] 11+ messages in thread
* [Bug middle-end/59138] [4.8/4.9 Regression] possible packed struct miscompile
2013-11-14 23:00 [Bug c/59138] New: possible packed struct miscompile regehr at cs dot utah.edu
` (5 preceding siblings ...)
2013-11-22 18:30 ` ebotcazou at gcc dot gnu.org
@ 2013-11-22 18:56 ` ebotcazou at gcc dot gnu.org
2013-11-27 9:17 ` ebotcazou at gcc dot gnu.org
` (2 subsequent siblings)
9 siblings, 0 replies; 11+ messages in thread
From: ebotcazou at gcc dot gnu.org @ 2013-11-22 18:56 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59138
Eric Botcazou <ebotcazou at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Component|rtl-optimization |middle-end
--- Comment #6 from Eric Botcazou <ebotcazou at gcc dot gnu.org> ---
Recategorizing.
^ permalink raw reply [flat|nested] 11+ messages in thread
* [Bug middle-end/59138] [4.8/4.9 Regression] possible packed struct miscompile
2013-11-14 23:00 [Bug c/59138] New: possible packed struct miscompile regehr at cs dot utah.edu
` (6 preceding siblings ...)
2013-11-22 18:56 ` [Bug middle-end/59138] " ebotcazou at gcc dot gnu.org
@ 2013-11-27 9:17 ` ebotcazou at gcc dot gnu.org
2013-11-27 9:19 ` ebotcazou at gcc dot gnu.org
2013-11-27 9:49 ` ebotcazou at gcc dot gnu.org
9 siblings, 0 replies; 11+ messages in thread
From: ebotcazou at gcc dot gnu.org @ 2013-11-27 9:17 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59138
--- Comment #7 from Eric Botcazou <ebotcazou at gcc dot gnu.org> ---
Author: ebotcazou
Date: Wed Nov 27 09:17:23 2013
New Revision: 205436
URL: http://gcc.gnu.org/viewcvs?rev=205436&root=gcc&view=rev
Log:
PR middle-end/59138
* expr.c (emit_group_store): Don't write past the end of the structure.
(store_bit_field): Fix formatting.
Added:
trunk/gcc/testsuite/gcc.c-torture/execute/20131127-1.c
Modified:
trunk/gcc/ChangeLog
trunk/gcc/expr.c
trunk/gcc/testsuite/ChangeLog
^ permalink raw reply [flat|nested] 11+ messages in thread
* [Bug middle-end/59138] [4.8/4.9 Regression] possible packed struct miscompile
2013-11-14 23:00 [Bug c/59138] New: possible packed struct miscompile regehr at cs dot utah.edu
` (7 preceding siblings ...)
2013-11-27 9:17 ` ebotcazou at gcc dot gnu.org
@ 2013-11-27 9:19 ` ebotcazou at gcc dot gnu.org
2013-11-27 9:49 ` ebotcazou at gcc dot gnu.org
9 siblings, 0 replies; 11+ messages in thread
From: ebotcazou at gcc dot gnu.org @ 2013-11-27 9:19 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59138
--- Comment #8 from Eric Botcazou <ebotcazou at gcc dot gnu.org> ---
Author: ebotcazou
Date: Wed Nov 27 09:19:47 2013
New Revision: 205437
URL: http://gcc.gnu.org/viewcvs?rev=205437&root=gcc&view=rev
Log:
PR middle-end/59138
* expr.c (emit_group_store): Don't write past the end of the structure.
(store_bit_field): Fix formatting.
Added:
branches/gcc-4_8-branch/gcc/testsuite/gcc.c-torture/execute/20131127-1.c
- copied unchanged from r205436,
trunk/gcc/testsuite/gcc.c-torture/execute/20131127-1.c
Modified:
branches/gcc-4_8-branch/gcc/ChangeLog
branches/gcc-4_8-branch/gcc/expr.c
branches/gcc-4_8-branch/gcc/testsuite/ChangeLog
^ permalink raw reply [flat|nested] 11+ messages in thread
* [Bug middle-end/59138] [4.8/4.9 Regression] possible packed struct miscompile
2013-11-14 23:00 [Bug c/59138] New: possible packed struct miscompile regehr at cs dot utah.edu
` (8 preceding siblings ...)
2013-11-27 9:19 ` ebotcazou at gcc dot gnu.org
@ 2013-11-27 9:49 ` ebotcazou at gcc dot gnu.org
9 siblings, 0 replies; 11+ messages in thread
From: ebotcazou at gcc dot gnu.org @ 2013-11-27 9:49 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59138
Eric Botcazou <ebotcazou at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|ASSIGNED |RESOLVED
Resolution|--- |FIXED
--- Comment #9 from Eric Botcazou <ebotcazou at gcc dot gnu.org> ---
Thanks for reporting the problem.
^ permalink raw reply [flat|nested] 11+ messages in thread
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2013-11-14 23:00 [Bug c/59138] New: possible packed struct miscompile regehr at cs dot utah.edu
2013-11-15 9:17 ` [Bug c/59138] [4.8/4.9 Regression] " rguenth at gcc dot gnu.org
2013-11-16 18:33 ` mikpelinux at gmail dot com
2013-11-21 14:41 ` [Bug rtl-optimization/59138] " rguenth at gcc dot gnu.org
2013-11-21 16:27 ` ebotcazou at gcc dot gnu.org
2013-11-22 11:08 ` ebotcazou at gcc dot gnu.org
2013-11-22 18:30 ` ebotcazou at gcc dot gnu.org
2013-11-22 18:56 ` [Bug middle-end/59138] " ebotcazou at gcc dot gnu.org
2013-11-27 9:17 ` ebotcazou at gcc dot gnu.org
2013-11-27 9:19 ` ebotcazou at gcc dot gnu.org
2013-11-27 9:49 ` ebotcazou at gcc dot gnu.org
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