* [Bug tree-optimization/54031] [4.8 Regression] Revision 189607 miscompiles Linux kernel
2012-07-19 13:09 [Bug tree-optimization/54031] New: [4.8 Regression] Revision 189607 miscompiles Linux kernel markus at trippelsdorf dot de
@ 2012-07-19 13:17 ` rguenth at gcc dot gnu.org
2012-07-19 13:36 ` rguenth at gcc dot gnu.org
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From: rguenth at gcc dot gnu.org @ 2012-07-19 13:17 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54031
Richard Guenther <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |WAITING
Last reconfirmed| |2012-07-19
CC| |rguenth at gcc dot gnu.org
Target Milestone|--- |4.8.0
Ever Confirmed|0 |1
--- Comment #1 from Richard Guenther <rguenth at gcc dot gnu.org> 2012-07-19 13:17:13 UTC ---
Please narrow down the issue, like check where it hangs and attach preprocessed
source of the compilation unit involved.
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2012-07-19 13:09 [Bug tree-optimization/54031] New: [4.8 Regression] Revision 189607 miscompiles Linux kernel markus at trippelsdorf dot de
2012-07-19 13:17 ` [Bug tree-optimization/54031] " rguenth at gcc dot gnu.org
@ 2012-07-19 13:36 ` rguenth at gcc dot gnu.org
2012-07-19 14:06 ` markus at trippelsdorf dot de
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From: rguenth at gcc dot gnu.org @ 2012-07-19 13:36 UTC (permalink / raw)
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--- Comment #2 from Richard Guenther <rguenth at gcc dot gnu.org> 2012-07-19 13:36:34 UTC ---
I have spotted an error in the patch, can you try
Index: gcc/builtins.c
===================================================================
--- gcc/builtins.c (revision 189656)
+++ gcc/builtins.c (working copy)
@@ -346,12 +346,10 @@ get_object_alignment_2 (tree exp, unsign
known_alignment
= get_pointer_alignment_1 (addr, &ptr_align, &ptr_bitpos);
- bitpos += ptr_bitpos;
align = MAX (ptr_align, align);
- if (TREE_CODE (exp) == MEM_REF
- || TREE_CODE (exp) == TARGET_MEM_REF)
- bitpos += mem_ref_offset (exp).low * BITS_PER_UNIT;
+ /* The alignment of the pointer operand in a TARGET_MEM_REF
+ has to take the variable offset parts into account. */
if (TREE_CODE (exp) == TARGET_MEM_REF)
{
if (TMR_INDEX (exp))
@@ -369,9 +367,19 @@ get_object_alignment_2 (tree exp, unsign
/* When EXP is an actual memory reference then we can use
TYPE_ALIGN of a pointer indirection to derive alignment.
Do so only if get_pointer_alignment_1 did not reveal absolute
- alignment knowledge. */
- if (!addr_p && !known_alignment)
- align = MAX (TYPE_ALIGN (TREE_TYPE (exp)), align);
+ alignment knowledge and if using that alignment would
+ improve the situation. */
+ if (!addr_p && !known_alignment
+ && TYPE_ALIGN (TREE_TYPE (exp)) > align)
+ align = TYPE_ALIGN (TREE_TYPE (exp));
+ else
+ {
+ /* Else adjust bitpos accordingly. */
+ bitpos += ptr_bitpos;
+ if (TREE_CODE (exp) == MEM_REF
+ || TREE_CODE (exp) == TARGET_MEM_REF)
+ bitpos += mem_ref_offset (exp).low * BITS_PER_UNIT;
+ }
}
else if (TREE_CODE (exp) == STRING_CST)
{
^ permalink raw reply [flat|nested] 10+ messages in thread* [Bug tree-optimization/54031] [4.8 Regression] Revision 189607 miscompiles Linux kernel
2012-07-19 13:09 [Bug tree-optimization/54031] New: [4.8 Regression] Revision 189607 miscompiles Linux kernel markus at trippelsdorf dot de
2012-07-19 13:17 ` [Bug tree-optimization/54031] " rguenth at gcc dot gnu.org
2012-07-19 13:36 ` rguenth at gcc dot gnu.org
@ 2012-07-19 14:06 ` markus at trippelsdorf dot de
2012-07-19 17:28 ` markus at trippelsdorf dot de
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From: markus at trippelsdorf dot de @ 2012-07-19 14:06 UTC (permalink / raw)
To: gcc-bugs
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--- Comment #3 from Markus Trippelsdorf <markus at trippelsdorf dot de> 2012-07-19 14:06:14 UTC ---
(In reply to comment #2)
> I have spotted an error in the patch, can you try
Unfortunately it doesn't fix the issue. I will try to narrow it down tomorrow.
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2012-07-19 13:09 [Bug tree-optimization/54031] New: [4.8 Regression] Revision 189607 miscompiles Linux kernel markus at trippelsdorf dot de
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2012-07-19 14:06 ` markus at trippelsdorf dot de
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From: markus at trippelsdorf dot de @ 2012-07-19 17:28 UTC (permalink / raw)
To: gcc-bugs
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--- Comment #4 from Markus Trippelsdorf <markus at trippelsdorf dot de> 2012-07-19 17:28:26 UTC ---
Created attachment 27835
--> http://gcc.gnu.org/bugzilla/attachment.cgi?id=27835
preprocessed source of the compilation unit involved
I've narrowed it down to a single compilation unit kernel/time/clocksource.c.
The function __clocksource_register_scale causes the hang.
(When I compile clocksource.c with an older compiler and copy the object file
into the kernel tree compiled with the latest gcc-4.8 then the kernel works
fine.)
These are the options:
--save-temps -Wp,-MD,kernel/time/.clocksource.o.d -nostdinc -isystem
/usr/lib/gcc/x86_64-pc-linux-gnu/4.8.0/include -I/usr/src/linux/arch/x86/includ
e -Iarch/x86/include/generated -Iinclude -include
/usr/src/linux/include/linux/kconfig.h -D__KERNEL__ -Wall -Wundef
-Wstrict-prototypes -Wno-trigrap
hs -fno-strict-aliasing -fno-common -Werror-implicit-function-declaration
-Wno-format-security -fno-delete-null-pointer-checks -O2 -m64 -march=native
-mno-red-zone -mcmodel=kernel -funit-at-a-time -maccumulate-outgoing-args
-DCONFIG_X86_X32_ABI -DCONFIG_AS_CFI=1 -DCONFIG_AS_CFI_SIGNAL_FRAME=1 -DCO
NFIG_AS_CFI_SECTIONS=1 -DCONFIG_AS_FXSAVEQ=1 -DCONFIG_AS_AVX=1 -pipe
-Wno-sign-compare -fno-asynchronous-unwind-tables -mno-sse -mno-mmx -mno-sse2
-m
no-3dnow -mno-avx -Wframe-larger-than=1024 -fno-stack-protector
-Wno-unused-but-set-variable -fomit-frame-pointer -Wdeclaration-after-statement
-Wno-
pointer-sign -fno-strict-overflow -fconserve-stack -DCC_HAVE_ASM_GOTO
-D"KBUILD_STR(s)=\#s" -D"KBUILD_BASENAME=KBUILD_STR(clocksource)" -D"KBUILD
_MODNAME=KBUILD_STR(clocksource)" -c -o kernel/time/clocksource.o
kernel/time/clocksource.c
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2012-07-19 13:09 [Bug tree-optimization/54031] New: [4.8 Regression] Revision 189607 miscompiles Linux kernel markus at trippelsdorf dot de
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2012-07-19 17:28 ` markus at trippelsdorf dot de
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2012-07-20 9:00 ` rguenth at gcc dot gnu.org
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From: markus at trippelsdorf dot de @ 2012-07-19 18:01 UTC (permalink / raw)
To: gcc-bugs
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--- Comment #5 from Markus Trippelsdorf <markus at trippelsdorf dot de> 2012-07-19 18:01:16 UTC ---
Function clocksource_enqueue is compiled to an endless loop:
static void clocksource_enqueue(struct clocksource *cs)
{
struct list_head *entry = &clocksource_list;
struct clocksource *tmp;
for (tmp = ({ const typeof( ((typeof(*tmp) *)0)->list ) *__mptr =
((&clocksource_list)->next); (typeof(*tmp) *)( (char *)__mptr -
__builtin_offsetof(typeof(*tmp),list) );}); &tmp->list != (&clocksource_list);
tmp = ({ const typeof( ((typeof(*tmp) *)0)->list ) *__mptr = (tmp->list.next);
(typeof(*tmp) *)( (char *)__mptr - __builtin_offsetof(typeof(*tmp),list) );}))
if (tmp->rating >= cs->rating)
entry = &tmp->list;
list_add(&cs->list, entry);
}
>From clocksource.s:
.type clocksource_enqueue.isra.3, @function
clocksource_enqueue.isra.3:
.p2align 5,,24
.p2align 3
.L35:
jmp .L35
.size clocksource_enqueue.isra.3, .-clocksource_enqueue.isra.3
.section .rodata.str1.8,"aMS",@progbits,1
.align 8
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2012-07-19 13:09 [Bug tree-optimization/54031] New: [4.8 Regression] Revision 189607 miscompiles Linux kernel markus at trippelsdorf dot de
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2012-07-19 18:01 ` markus at trippelsdorf dot de
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From: rguenth at gcc dot gnu.org @ 2012-07-20 9:00 UTC (permalink / raw)
To: gcc-bugs
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Richard Guenther <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|WAITING |NEW
--- Comment #6 from Richard Guenther <rguenth at gcc dot gnu.org> 2012-07-20 09:00:26 UTC ---
Mine.
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2012-07-19 13:09 [Bug tree-optimization/54031] New: [4.8 Regression] Revision 189607 miscompiles Linux kernel markus at trippelsdorf dot de
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2012-07-20 11:25 ` rguenth at gcc dot gnu.org
2012-07-20 11:26 ` rguenth at gcc dot gnu.org
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From: rguenth at gcc dot gnu.org @ 2012-07-20 9:28 UTC (permalink / raw)
To: gcc-bugs
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--- Comment #7 from Richard Guenther <rguenth at gcc dot gnu.org> 2012-07-20 09:27:48 UTC ---
There are several issues in CCP exposed. First, we compute
bit_value_binop_1 (NE_EXPR, ...,
{low = 0x38, high = 0x0}, {low = 0xffffffffffffffc0, high = 0x0},
{low = 0x0, high = 0x0}, {low = 0xfffffffffffffff0, high = 0x0})
as false because in
D.16870_8 = &tmp_3->list;
if (D.16870_8 != &clocksource_list)
we see that clocksource_list is aligned to 128 and &tmp_3->list refers
to the type clocksource via tmp_3 which has a user alignment of 512,
so the resulting pointer is misaligned by 448 bits (the offset of the
list member). That makes the equality test never true unless the
types involved do not have their specified alignment.
Which makes this an invalid source. I didn't investigate in detail
but certainly the code uses the aligned type for pointers that are
not suitably aligned.
Now, we didn't want to extract this elaborated alignment information
from addresses (only from actual accesses), which is the real bug fixed
as follows:
Index: gcc/tree-ssa-ccp.c
===================================================================
--- gcc/tree-ssa-ccp.c (revision 189704)
+++ gcc/tree-ssa-ccp.c (working copy)
@@ -510,7 +510,7 @@ get_value_from_alignment (tree expr)
gcc_assert (TREE_CODE (expr) == ADDR_EXPR);
- get_object_alignment_1 (TREE_OPERAND (expr, 0), &align, &bitpos);
+ get_pointer_alignment_1 (expr, &align, &bitpos);
val.mask
= double_int_and_not (POINTER_TYPE_P (type) || TYPE_UNSIGNED (type)
? double_int_mask (TYPE_PRECISION (type))
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2012-07-19 13:09 [Bug tree-optimization/54031] New: [4.8 Regression] Revision 189607 miscompiles Linux kernel markus at trippelsdorf dot de
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@ 2012-07-20 11:25 ` rguenth at gcc dot gnu.org
2012-07-20 11:26 ` rguenth at gcc dot gnu.org
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From: rguenth at gcc dot gnu.org @ 2012-07-20 11:25 UTC (permalink / raw)
To: gcc-bugs
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--- Comment #8 from Richard Guenther <rguenth at gcc dot gnu.org> 2012-07-20 11:25:01 UTC ---
Author: rguenth
Date: Fri Jul 20 11:24:55 2012
New Revision: 189715
URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=189715
Log:
2012-07-20 Richard Guenther <rguenther@suse.de>
PR tree-optimization/54031
* tree-ssa-ccp.c (get_value_from_alignment): Use
get_pointer_alignment_1.
Modified:
trunk/gcc/ChangeLog
trunk/gcc/tree-ssa-ccp.c
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2012-07-19 13:09 [Bug tree-optimization/54031] New: [4.8 Regression] Revision 189607 miscompiles Linux kernel markus at trippelsdorf dot de
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2012-07-20 11:25 ` rguenth at gcc dot gnu.org
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From: rguenth at gcc dot gnu.org @ 2012-07-20 11:26 UTC (permalink / raw)
To: gcc-bugs
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Richard Guenther <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |RESOLVED
Resolution| |FIXED
--- Comment #9 from Richard Guenther <rguenth at gcc dot gnu.org> 2012-07-20 11:26:00 UTC ---
Fixed.
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