* [Bug tree-optimization/18241] linux kernel loop gets miscompiled
2004-10-31 1:03 [Bug tree-optimization/18241] New: linux kernel loop gets miscompiled ak at muc dot de
@ 2004-10-31 1:07 ` ak at muc dot de
2004-10-31 4:41 ` [Bug tree-optimization/18241] [4.0 Regression] " pinskia at gcc dot gnu dot org
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From: ak at muc dot de @ 2004-10-31 1:07 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From ak at muc dot de 2004-10-31 01:07 -------
Created an attachment (id=7440)
--> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=7440&action=view)
miscompiled function
Compiled with -O2 -fno-reorder-blocks -mno-redzone -mcmodel=kernel
It crashes eventually in this loop
do {
int idx;
tag_clear(pathp[0].node, tag, pathp[0].offset);
for (idx = 0; idx < (((1UL << 6) + 64 - 1) / 64); idx++) {
if (pathp[0].node->tags[tag][idx])
goto out;
}
pathp--;
} while (pathp[0].node);
when accessing pathp[0].node. I suspect it is overrunning the array on the
stack. With -O0 this crash doesn't happen.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18241
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2004-10-31 1:03 [Bug tree-optimization/18241] New: linux kernel loop gets miscompiled ak at muc dot de
2004-10-31 1:07 ` [Bug tree-optimization/18241] " ak at muc dot de
@ 2004-10-31 4:41 ` pinskia at gcc dot gnu dot org
2004-11-01 2:26 ` giovannibajo at libero dot it
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From: pinskia at gcc dot gnu dot org @ 2004-10-31 4:41 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From pinskia at gcc dot gnu dot org 2004-10-31 04:41 -------
Does -fno-ivopts produce a correct code?
--
What |Removed |Added
----------------------------------------------------------------------------
Keywords| |wrong-code
Summary|linux kernel loop gets |[4.0 Regression] linux
|miscompiled |kernel loop gets miscompiled
Target Milestone|--- |4.0.0
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18241
^ permalink raw reply [flat|nested] 39+ messages in thread* [Bug tree-optimization/18241] [4.0 Regression] linux kernel loop gets miscompiled
2004-10-31 1:03 [Bug tree-optimization/18241] New: linux kernel loop gets miscompiled ak at muc dot de
2004-10-31 1:07 ` [Bug tree-optimization/18241] " ak at muc dot de
2004-10-31 4:41 ` [Bug tree-optimization/18241] [4.0 Regression] " pinskia at gcc dot gnu dot org
@ 2004-11-01 2:26 ` giovannibajo at libero dot it
2004-11-01 2:29 ` giovannibajo at libero dot it
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From: giovannibajo at libero dot it @ 2004-11-01 2:26 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From giovannibajo at libero dot it 2004-11-01 02:26 -------
The final tree dump of the loop with -O1 -fno-ivopts looks like this:
<L15>:;
nr = pathp->offset;
node = pathp->node;
D.7834 = &node->tags;
addr.9 = (volatile long int *) ((long unsigned int *) D.7834 + D.7838);
__asm__ __volatile__("btrl %1,%0":"=m" *addr.9:"dIr" nr);
D.7823 = node->tags[tag][0];
if (D.7823 != 0) goto out; else goto <L10>;
<L10>:;
pathp = pathp - 12B;
if (pathp->node != 0B) goto <L15>; else goto out;
With IV-OPTS, it is like this:
<L15>:;
nr = *ivtmp.124;
node = *((struct radix_tree_node * *) ivtmp.124 + -8B);
D.7834 = &node->tags;
addr.9 = (volatile long int *) ((long unsigned int *) D.7834 + D.7838);
__asm__ __volatile__("btrl %1,%0":"=m" *addr.9:"dIr" nr);
D.7823 = node->tags[tag][0];
if (D.7823 != 0) goto out; else goto <L10>;
Invalid sum of incoming frequencies 9667, should be 9550
<L10>:;
D.7820 = *ivtmp.128;
ivtmp.124 = ivtmp.124 - 12B;
ivtmp.128 = ivtmp.128 - 12B;
if (D.7820 != 0B) goto <L15>; else goto out;
It looks like the end condition is now checked on the pointer BEFORE
decrementing it, unless I am mistaken.
Zdenek, two questions:
- Aren't ivtmp.128 and ivtmp.124 duplicates?
- Since they behave exactly like pathp, there is a way to at least preserve the
variable name so that the code is easier to read?
--
What |Removed |Added
----------------------------------------------------------------------------
CC| |rakdver at gcc dot gnu dot
| |org, giovannibajo at libero
| |dot it
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18241
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2004-10-31 1:03 [Bug tree-optimization/18241] New: linux kernel loop gets miscompiled ak at muc dot de
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From: giovannibajo at libero dot it @ 2004-11-01 2:29 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From giovannibajo at libero dot it 2004-11-01 02:29 -------
(In reply to comment #3)
> Zdenek, two questions:
> - Aren't ivtmp.128 and ivtmp.124 duplicates?
Uhm, forget about this :)
> - Since ivtmp.128 behaves exactly like pathp, there is a way to at least
preserve the
> variable name so that the code is easier to read?
This would be still cool
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18241
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2004-10-31 1:03 [Bug tree-optimization/18241] New: linux kernel loop gets miscompiled ak at muc dot de
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From: pinskia at gcc dot gnu dot org @ 2004-11-01 2:34 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From pinskia at gcc dot gnu dot org 2004-11-01 02:34 -------
Also for the first loop, we look we do much worse code with -fivopts at least on powerpc64:
With -fno-ivopts:
offset = (int) (unsigned int) (index >> (int) shift) & 63;
pathp = pathp.109 + 24B;
pathp->offset = offset;
temp.107 = *pathp.109->slot;
pathp->node = temp.107;
D.7848 = (struct radix_tree_node * *) &temp.107->slots + (void * *) ((long unsigned int) offset * 8);
pathp->slot = D.7848;
shift = shift - 6;
height = height - 1;
without:
offset = (int) (unsigned int) (index >> (int) (shift + (unsigned int) ivtmp.126 * 4294967290)) & 63;
<--- here why not keep the shift decrementing
pathp.155 = ivtmp.137 + &path + 24B;
D.8017 = &path + 24B;
*((int *) ivtmp.137 + &D.8017->offset) = offset;
D.8020 = (struct radix_tree_node * * *) ivtmp.137;
temp.162 = **(D.8020 + &path[0].slot);
*((struct radix_tree_node * *) ivtmp.137 + &D.8017->node) = temp.162;
D.7848 = (struct radix_tree_node * *) &temp.162->slots + (void * *) ((long unsigned int) offset * 8);
*(D.8020 + &D.8017->slot) = D.7848;
height = height + 4294967295;
--
What |Removed |Added
----------------------------------------------------------------------------
CC| |pinskia at gcc dot gnu dot
| |org
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18241
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2004-10-31 1:03 [Bug tree-optimization/18241] New: linux kernel loop gets miscompiled ak at muc dot de
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From: pinskia at gcc dot gnu dot org @ 2004-11-01 2:36 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From pinskia at gcc dot gnu dot org 2004-11-01 02:36 -------
The corresponding asm for the loop:
with -fno-ivopts:
L11:
ld r11,8(r10)
srd r2,r4,r7
addi r0,r7,-6
rldicl r2,r2,0,58
rldicl r7,r0,0,32
ld r9,0(r11)
sldi r6,r2,3
addi r11,r10,24
stw r2,16(r11)
addi r8,r9,8
std r9,24(r10)
mr r10,r11
add r0,r8,r6
std r0,8(r11)
bdnz L8
without:
L11:
add r11,r8,r30
mulli r0,r3,-6 <--- this is really not a good idea inside the loop
add r10,r5,r8
addi r3,r3,1
ld r2,8(r11)
addi r7,r11,24
add r0,r0,r12
ld r9,0(r2)
srd r0,r4,r0
rldicl r0,r0,0,58
addi r6,r9,8
sldi r11,r0,3
stdx r9,r8,r5
stw r0,16(r10)
addi r8,r8,24
add r2,r6,r11
std r2,8(r10
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18241
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2004-10-31 1:03 [Bug tree-optimization/18241] New: linux kernel loop gets miscompiled ak at muc dot de
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From: ak at muc dot de @ 2004-11-01 3:07 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From ak at muc dot de 2004-11-01 03:07 -------
I must correct myself slightly - the kernel oops I see is not the second
loop, but in the check before:
ret = *pathp[0].slot; <--- references either NULL or a bogus pointer
if (ret == NULL)
goto out;
I tried various options, but only -O0 resolves it. -O1, -O2 -fno-ivopts or -O1
-fno-tree-loop-ivcanon doesn't (depending on the options the crash
is a NULL pointer or a bogus non NULL pointer)
It's hard unfortunately to construct a run time test because it would
need to create a simulated radixtree.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18241
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2004-10-31 1:03 [Bug tree-optimization/18241] New: linux kernel loop gets miscompiled ak at muc dot de
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@ 2004-11-01 3:08 ` ak at muc dot de
2004-11-16 17:54 ` pinskia at gcc dot gnu dot org
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From: ak at muc dot de @ 2004-11-01 3:08 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From ak at muc dot de 2004-11-01 03:08 -------
To clarify the previous comment means that the problem is likely in the
first loop in the function, not in the second
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18241
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2004-10-31 1:03 [Bug tree-optimization/18241] New: linux kernel loop gets miscompiled ak at muc dot de
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From: pinskia at gcc dot gnu dot org @ 2004-11-16 17:54 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From pinskia at gcc dot gnu dot org 2004-11-16 17:54 -------
Does this still happen?
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18241
^ permalink raw reply [flat|nested] 39+ messages in thread* [Bug tree-optimization/18241] [4.0 Regression] linux kernel loop gets miscompiled
2004-10-31 1:03 [Bug tree-optimization/18241] New: linux kernel loop gets miscompiled ak at muc dot de
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From: ak at muc dot de @ 2004-11-25 0:22 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From ak at muc dot de 2004-11-25 00:22 -------
Problem still happens as of HEAD 041125
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18241
^ permalink raw reply [flat|nested] 39+ messages in thread* [Bug tree-optimization/18241] [4.0 Regression] linux kernel loop gets miscompiled
2004-10-31 1:03 [Bug tree-optimization/18241] New: linux kernel loop gets miscompiled ak at muc dot de
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From: pinskia at gcc dot gnu dot org @ 2004-11-27 23:07 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From pinskia at gcc dot gnu dot org 2004-11-27 23:07 -------
Can you try with -fno-tree-ch (or -Os)?
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18241
^ permalink raw reply [flat|nested] 39+ messages in thread* [Bug tree-optimization/18241] [4.0 Regression] linux kernel loop gets miscompiled
2004-10-31 1:03 [Bug tree-optimization/18241] New: linux kernel loop gets miscompiled ak at muc dot de
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From: ak at muc dot de @ 2004-11-28 0:17 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From ak at muc dot de 2004-11-28 00:17 -------
Tried -fno-tree-ch. Didn't help.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18241
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2004-10-31 1:03 [Bug tree-optimization/18241] New: linux kernel loop gets miscompiled ak at muc dot de
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From: ak at muc dot de @ 2004-11-28 1:05 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From ak at muc dot de 2004-11-28 01:05 -------
-O1 -fno-tree-dominator-opts seems to avoid the problem
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18241
^ permalink raw reply [flat|nested] 39+ messages in thread* [Bug tree-optimization/18241] [4.0 Regression] linux kernel loop gets miscompiled
2004-10-31 1:03 [Bug tree-optimization/18241] New: linux kernel loop gets miscompiled ak at muc dot de
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From: ak at muc dot de @ 2004-11-28 1:21 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From ak at muc dot de 2004-11-28 01:21 -------
When I comment out the first pass_dominator in tree-optimize.c and compile
with -O1 it works too.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18241
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2004-10-31 1:03 [Bug tree-optimization/18241] New: linux kernel loop gets miscompiled ak at muc dot de
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From: pinskia at gcc dot gnu dot org @ 2004-11-28 1:28 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From pinskia at gcc dot gnu dot org 2004-11-28 01:28 -------
Confirmed, this looks like a jump threading bug.
Before we have:
goto <bb 9> (<L10>);
<L8>:;
D.7815_42 = pathp_2->node;
tag_43 = tag_27;
idx_44 = idx_6;
D.7819_45 = D.7815_42->tags[tag_43][idx_44];
if (D.7819_45 != 0) goto out; else goto <L9>;
<L9>:;
idx_46 = idx_6 + 1;
# idx_6 = PHI <idx_39(6), idx_46(8)>;
<L10>:;
if (idx_6 == 0) goto <L8>; else goto <L11>;
But after:
goto <bb 8> (<L10>);
<L9>:;
idx_46 = 1;
goto <bb 10> (<L15>);
# idx_57 = PHI <0(6)>;
<L10>:;
D.7815_42 = pathp_2->node;
tag_43 = tag_27;
idx_44 = 0; <---- this is just plainly wrong.
D.7819_45 = D.7815_42->tags[tag_27][0];
if (D.7819_45 != 0) goto out; else goto <L9>;
--
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |NEW
Ever Confirmed| |1
Last reconfirmed|0000-00-00 00:00:00 |2004-11-28 01:28:23
date| |
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18241
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2004-10-31 1:03 [Bug tree-optimization/18241] New: linux kernel loop gets miscompiled ak at muc dot de
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From: ak at muc dot de @ 2004-11-28 1:33 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From ak at muc dot de 2004-11-28 01:33 -------
Hmm, the oops was in the test before the second loop, but idx is in the second
loop. But maybe I misread it.
--
What |Removed |Added
----------------------------------------------------------------------------
Component|tree-optimization |web
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18241
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From: rakdver at atrey dot karlin dot mff dot cuni dot cz @ 2004-11-28 9:17 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From rakdver at atrey dot karlin dot mff dot cuni dot cz 2004-11-28 09:17 -------
Subject: Re: [4.0 Regression] linux kernel loop gets miscompiled
>
> ------- Additional Comments From pinskia at gcc dot gnu dot org 2004-11-28 01:28 -------
> Confirmed, this looks like a jump threading bug.
> Before we have:
> goto <bb 9> (<L10>);
>
> <L8>:;
> D.7815_42 = pathp_2->node;
> tag_43 = tag_27;
> idx_44 = idx_6;
> D.7819_45 = D.7815_42->tags[tag_43][idx_44];
> if (D.7819_45 != 0) goto out; else goto <L9>;
>
> <L9>:;
> idx_46 = idx_6 + 1;
>
> # idx_6 = PHI <idx_39(6), idx_46(8)>;
> <L10>:;
> if (idx_6 == 0) goto <L8>; else goto <L11>;
>
>
> But after:
> goto <bb 8> (<L10>);
>
> <L9>:;
> idx_46 = 1;
> goto <bb 10> (<L15>);
>
> # idx_57 = PHI <0(6)>;
> <L10>:;
> D.7815_42 = pathp_2->node;
> tag_43 = tag_27;
> idx_44 = 0; <---- this is just plainly wrong.
this seems OK to me (note the "weird" condition that
ends the loop -- this loops iterates exactly once, with idx being 0).
> D.7819_45 = D.7815_42->tags[tag_27][0];
> if (D.7819_45 != 0) goto out; else goto <L9>;
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18241
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2004-10-31 1:03 [Bug tree-optimization/18241] New: linux kernel loop gets miscompiled ak at muc dot de
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From: law at redhat dot com @ 2004-12-13 20:46 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From law at redhat dot com 2004-12-13 20:46 -------
I see no evidence that 18241 has the same root case as 18694.
--
What |Removed |Added
----------------------------------------------------------------------------
OtherBugsDependingO|18694 |
nThis| |
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18241
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From: law at redhat dot com @ 2004-12-13 21:01 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From law at redhat dot com 2004-12-13 21:01 -------
(In reply to comment #15)
> Confirmed, this looks like a jump threading bug.
> Before we have:
> goto <bb 9> (<L10>);
>
> <L8>:;
> D.7815_42 = pathp_2->node;
> tag_43 = tag_27;
> idx_44 = idx_6;
> D.7819_45 = D.7815_42->tags[tag_43][idx_44];
> if (D.7819_45 != 0) goto out; else goto <L9>;
>
> <L9>:;
> idx_46 = idx_6 + 1;
>
> # idx_6 = PHI <idx_39(6), idx_46(8)>;
> <L10>:;
> if (idx_6 == 0) goto <L8>; else goto <L11>;
>
>
> But after:
> goto <bb 8> (<L10>);
>
> <L9>:;
> idx_46 = 1;
> goto <bb 10> (<L15>);
>
> # idx_57 = PHI <0(6)>;
> <L10>:;
> D.7815_42 = pathp_2->node;
> tag_43 = tag_27;
> idx_44 = 0; <---- this is just plainly wrong.
> D.7819_45 = D.7815_42->tags[tag_27][0];
> if (D.7819_45 != 0) goto out; else goto <L9>;
Huh? idx_44 must be zero, I don't see how any other value can be correct here.
THe only way to get to L8 (block #7) is when idx_6 == 0 and idx_44 is set
unconditionally from idx_6.
So what about that assignment do you think is wrong?
Note that we also know that idx_46 must have the value 1 because it's only
reachable from block #7 where we know that idx_6 == 0 and thus idx_46 must
have the value 1.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18241
^ permalink raw reply [flat|nested] 39+ messages in thread* [Bug tree-optimization/18241] [4.0 Regression] linux kernel loop gets miscompiled
2004-10-31 1:03 [Bug tree-optimization/18241] New: linux kernel loop gets miscompiled ak at muc dot de
` (18 preceding siblings ...)
2004-12-13 21:01 ` law at redhat dot com
@ 2004-12-13 22:16 ` law at redhat dot com
2004-12-15 15:14 ` steven at gcc dot gnu dot org
` (17 subsequent siblings)
37 siblings, 0 replies; 39+ messages in thread
From: law at redhat dot com @ 2004-12-13 22:16 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From law at redhat dot com 2004-12-13 22:15 -------
FWIW, I've walked through all the actions of DOM1 and AFAICT every change it
makes is correct. I would have to strongly suspect that DOM1 is not the problem
here, but is instead changing things in such a way as to expose some downstream
issue.
I've also looked pretty closely at the later tree optimizer dumps. If indeed
the problem is the ret = *pathp[0].slot statement blowing up, I would strongly
suggest some printf debugging of the first loop. Namely, how many times does
it iterate and what is the value of pathp before and after the loop.
Jeff
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18241
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` (19 preceding siblings ...)
2004-12-13 22:16 ` law at redhat dot com
@ 2004-12-15 15:14 ` steven at gcc dot gnu dot org
2004-12-15 15:16 ` steven at gcc dot gnu dot org
` (16 subsequent siblings)
37 siblings, 0 replies; 39+ messages in thread
From: steven at gcc dot gnu dot org @ 2004-12-15 15:14 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From steven at gcc dot gnu dot org 2004-12-15 15:14 -------
methinks the bug is in this code:
/* ??? This bit ought not be needed. For any element not present
in the initializer, we should simply set them to zero. Except
we'd need to *find* the elements that are not present, and that
requires trickery to avoid quadratic compile-time behavior in
large cases or excessive memory use in small cases. */
else
{
HOST_WIDE_INT len = list_length (elt_list);
if (TREE_CODE (type) == ARRAY_TYPE)
{
tree nelts = array_type_nelts (type);
if (!host_integerp (nelts, 1)
|| tree_low_cst (nelts, 1) + 1 != len)
cleared = true;
}
else if (len != fields_length (type))
cleared = true;
}
We have this expr:
objD.1485 = {{.sD.1468=(const charD.1 *) (charD.1 *) "m0"}, {}}
The type of the constructor is an ARRAY_TYPE, nelts == 1, and len (the length
of the constructor) is 2. So nelts+1 == 2, and we set cleared = true. But
we ignore the fact that the second element of the constructor is empty, and
that the first one is incomplete.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18241
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2004-10-31 1:03 [Bug tree-optimization/18241] New: linux kernel loop gets miscompiled ak at muc dot de
` (20 preceding siblings ...)
2004-12-15 15:14 ` steven at gcc dot gnu dot org
@ 2004-12-15 15:16 ` steven at gcc dot gnu dot org
2004-12-18 12:03 ` steven at gcc dot gnu dot org
` (15 subsequent siblings)
37 siblings, 0 replies; 39+ messages in thread
From: steven at gcc dot gnu dot org @ 2004-12-15 15:16 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From steven at gcc dot gnu dot org 2004-12-15 15:16 -------
My last comment of course does not concern this bug, oops sorry :-)
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18241
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2004-10-31 1:03 [Bug tree-optimization/18241] New: linux kernel loop gets miscompiled ak at muc dot de
` (21 preceding siblings ...)
2004-12-15 15:16 ` steven at gcc dot gnu dot org
@ 2004-12-18 12:03 ` steven at gcc dot gnu dot org
2004-12-19 15:55 ` ak at muc dot de
` (14 subsequent siblings)
37 siblings, 0 replies; 39+ messages in thread
From: steven at gcc dot gnu dot org @ 2004-12-18 12:03 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From steven at gcc dot gnu dot org 2004-12-18 12:03 -------
We have reason to believe this bug is now fixed, but it is kind of
hard to test... Can you please retry with CVS HEAD?
--
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |WAITING
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18241
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2004-10-31 1:03 [Bug tree-optimization/18241] New: linux kernel loop gets miscompiled ak at muc dot de
` (22 preceding siblings ...)
2004-12-18 12:03 ` steven at gcc dot gnu dot org
@ 2004-12-19 15:55 ` ak at muc dot de
2005-01-03 13:41 ` arend dot bayer at web dot de
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37 siblings, 0 replies; 39+ messages in thread
From: ak at muc dot de @ 2004-12-19 15:55 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From ak at muc dot de 2004-12-19 15:55 -------
Problem still happens with 4.0.0 20041219
--
What |Removed |Added
----------------------------------------------------------------------------
Status|WAITING |NEW
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18241
^ permalink raw reply [flat|nested] 39+ messages in thread* [Bug tree-optimization/18241] [4.0 Regression] linux kernel loop gets miscompiled
2004-10-31 1:03 [Bug tree-optimization/18241] New: linux kernel loop gets miscompiled ak at muc dot de
` (23 preceding siblings ...)
2004-12-19 15:55 ` ak at muc dot de
@ 2005-01-03 13:41 ` arend dot bayer at web dot de
2005-01-03 13:44 ` giovannibajo at libero dot it
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37 siblings, 0 replies; 39+ messages in thread
From: arend dot bayer at web dot de @ 2005-01-03 13:41 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From arend dot bayer at web dot de 2005-01-03 13:41 -------
Happens on x86 too (symptom is an oops on boot in radix_tree_tag_clear).
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18241
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2004-10-31 1:03 [Bug tree-optimization/18241] New: linux kernel loop gets miscompiled ak at muc dot de
` (24 preceding siblings ...)
2005-01-03 13:41 ` arend dot bayer at web dot de
@ 2005-01-03 13:44 ` giovannibajo at libero dot it
2005-01-03 13:55 ` arend dot bayer at web dot de
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37 siblings, 0 replies; 39+ messages in thread
From: giovannibajo at libero dot it @ 2005-01-03 13:44 UTC (permalink / raw)
To: gcc-bugs
--
What |Removed |Added
----------------------------------------------------------------------------
Severity|normal |critical
Priority|P2 |P1
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18241
^ permalink raw reply [flat|nested] 39+ messages in thread* [Bug tree-optimization/18241] [4.0 Regression] linux kernel loop gets miscompiled
2004-10-31 1:03 [Bug tree-optimization/18241] New: linux kernel loop gets miscompiled ak at muc dot de
` (25 preceding siblings ...)
2005-01-03 13:44 ` giovannibajo at libero dot it
@ 2005-01-03 13:55 ` arend dot bayer at web dot de
2005-01-03 19:12 ` pinskia at gcc dot gnu dot org
` (10 subsequent siblings)
37 siblings, 0 replies; 39+ messages in thread
From: arend dot bayer at web dot de @ 2005-01-03 13:55 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From arend dot bayer at web dot de 2005-01-03 13:55 -------
Sorry, should have been a bit more specific probably:
gcc version 4.0.0 20050103 (experimental) (i686-pc-linux-gnu)
Kernel is 2.6.10, and the oops is triggered for me by the EXT3 code.
--
What |Removed |Added
----------------------------------------------------------------------------
CC| |arend dot bayer at web dot
| |de
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18241
^ permalink raw reply [flat|nested] 39+ messages in thread* [Bug tree-optimization/18241] [4.0 Regression] linux kernel loop gets miscompiled
2004-10-31 1:03 [Bug tree-optimization/18241] New: linux kernel loop gets miscompiled ak at muc dot de
` (26 preceding siblings ...)
2005-01-03 13:55 ` arend dot bayer at web dot de
@ 2005-01-03 19:12 ` pinskia at gcc dot gnu dot org
2005-01-03 20:46 ` belyshev at depni dot sinp dot msu dot ru
` (9 subsequent siblings)
37 siblings, 0 replies; 39+ messages in thread
From: pinskia at gcc dot gnu dot org @ 2005-01-03 19:12 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From pinskia at gcc dot gnu dot org 2005-01-03 19:12 -------
Hmm, the following statements don't have VOPS:
D.1145_20->offset = offset_19;
D.1146_22 = pathp_1->slot;
D.1145_21->node = D.1147_23;
D.1148_26 = D.1145_25->node;
D.1145_25->slot = D.1154_32;
D.1155_12 = pathp_1->node;
--
What |Removed |Added
----------------------------------------------------------------------------
CC| |dnovillo at gcc dot gnu dot
| |org
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18241
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2004-10-31 1:03 [Bug tree-optimization/18241] New: linux kernel loop gets miscompiled ak at muc dot de
` (27 preceding siblings ...)
2005-01-03 19:12 ` pinskia at gcc dot gnu dot org
@ 2005-01-03 20:46 ` belyshev at depni dot sinp dot msu dot ru
2005-01-03 21:07 ` law at redhat dot com
` (8 subsequent siblings)
37 siblings, 0 replies; 39+ messages in thread
From: belyshev at depni dot sinp dot msu dot ru @ 2005-01-03 20:46 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From belyshev at depni dot sinp dot msu dot ru 2005-01-03 20:46 -------
// even smaller testcase:
void abort (void);
void radix_tree_tag_clear (int *node)
{
int *path[2], **pathp = path, height;
volatile int *addr;
height = 1;
pathp[0] = node;
while (height > 0) {
pathp[1] = pathp[0];
pathp++;
height--;
}
addr = pathp[0];
*addr = 1;
}
int main ()
{
int n;
radix_tree_tag_clear (&n);
if (n != 1)
abort ();
return 0;
}
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18241
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2004-10-31 1:03 [Bug tree-optimization/18241] New: linux kernel loop gets miscompiled ak at muc dot de
` (28 preceding siblings ...)
2005-01-03 20:46 ` belyshev at depni dot sinp dot msu dot ru
@ 2005-01-03 21:07 ` law at redhat dot com
2005-01-03 21:10 ` pinskia at gcc dot gnu dot org
` (7 subsequent siblings)
37 siblings, 0 replies; 39+ messages in thread
From: law at redhat dot com @ 2005-01-03 21:07 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From law at redhat dot com 2005-01-03 21:07 -------
I'm not sure if it's the root cause yet, or just an interesting rat hole, but
we do not create any virtual operands for the *addr = <whatever> statement
(or for any statement with volatile operands).
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18241
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2004-10-31 1:03 [Bug tree-optimization/18241] New: linux kernel loop gets miscompiled ak at muc dot de
` (29 preceding siblings ...)
2005-01-03 21:07 ` law at redhat dot com
@ 2005-01-03 21:10 ` pinskia at gcc dot gnu dot org
2005-01-03 22:41 ` pinskia at gcc dot gnu dot org
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37 siblings, 0 replies; 39+ messages in thread
From: pinskia at gcc dot gnu dot org @ 2005-01-03 21:10 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From pinskia at gcc dot gnu dot org 2005-01-03 21:10 -------
(In reply to comment #30)
(In reply to comment #31)
> I'm not sure if it's the root cause yet, or just an interesting rat hole, but
> we do not create any virtual operands for the *addr = <whatever> statement
> (or for any statement with volatile operands).
Note if I remove the volatile from the example in comment #30, then it works so it looks like that is
root call because we don't know if we use the result of path[0].
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18241
^ permalink raw reply [flat|nested] 39+ messages in thread* [Bug tree-optimization/18241] [4.0 Regression] linux kernel loop gets miscompiled
2004-10-31 1:03 [Bug tree-optimization/18241] New: linux kernel loop gets miscompiled ak at muc dot de
` (30 preceding siblings ...)
2005-01-03 21:10 ` pinskia at gcc dot gnu dot org
@ 2005-01-03 22:41 ` pinskia at gcc dot gnu dot org
2005-01-03 22:59 ` steven at gcc dot gnu dot org
` (5 subsequent siblings)
37 siblings, 0 replies; 39+ messages in thread
From: pinskia at gcc dot gnu dot org @ 2005-01-03 22:41 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From pinskia at gcc dot gnu dot org 2005-01-03 22:41 -------
Here is the most reduced testcase:
void abort (void);
int f(int i1243)
{
int i[2], *i1 = i;
i[0] = 1;
volatile int *i2 = i1;
i2[1] = 1;
i1243 = 0;
return i2[1]+i2[0];
}
int main(void)
{
if( f(100) != 2)
abort ();
return 0;
}
Notice we remove i[0] = 1
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18241
^ permalink raw reply [flat|nested] 39+ messages in thread* [Bug tree-optimization/18241] [4.0 Regression] linux kernel loop gets miscompiled
2004-10-31 1:03 [Bug tree-optimization/18241] New: linux kernel loop gets miscompiled ak at muc dot de
` (31 preceding siblings ...)
2005-01-03 22:41 ` pinskia at gcc dot gnu dot org
@ 2005-01-03 22:59 ` steven at gcc dot gnu dot org
2005-01-03 23:27 ` belyshev at depni dot sinp dot msu dot ru
` (4 subsequent siblings)
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From: steven at gcc dot gnu dot org @ 2005-01-03 22:59 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From steven at gcc dot gnu dot org 2005-01-03 22:59 -------
the .t17.ssa dump:
f (i1243D.1466)
{
volatile intD.0 * i2D.1471;
intD.0 * i1D.1470;
intD.0 iD.1469[2];
intD.0 D.1475;
intD.0 D.1474;
intD.0 D.1473;
volatile intD.0 * D.1472;
# BLOCK 0
# PRED: ENTRY (fallthru)
i1D.1470_1 = &iD.1469;
# iD.1469_3 = V_MAY_DEF <iD.1469_2>;
iD.1469[0] = 1;
i2D.1471_4 = i1D.1470_1;
D.1472_5 = i2D.1471_4 + 4B;
*D.1472_5 = 1;
i1243D.1466_6 = 0;
D.1472_7 = i2D.1471_4 + 4B;
D.1474_8 = *D.1472_7;
D.1475_9 = *i2D.1471_4;
D.1473_10 = D.1474_8 + D.1475_9;
return D.1473_10;
# SUCC: EXIT
}
Shouldn't there be a VUSE for "D.1474_8 = *D.1472_7"?
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18241
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2004-10-31 1:03 [Bug tree-optimization/18241] New: linux kernel loop gets miscompiled ak at muc dot de
` (32 preceding siblings ...)
2005-01-03 22:59 ` steven at gcc dot gnu dot org
@ 2005-01-03 23:27 ` belyshev at depni dot sinp dot msu dot ru
2005-01-04 0:40 ` [Bug tree-optimization/18241] [4.0 Regression] volatile causes mis-compiling pinskia at gcc dot gnu dot org
` (3 subsequent siblings)
37 siblings, 0 replies; 39+ messages in thread
From: belyshev at depni dot sinp dot msu dot ru @ 2005-01-03 23:27 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From belyshev at depni dot sinp dot msu dot ru 2005-01-03 23:27 -------
// final version :)
void abort (void);
int main ()
{
int a;
volatile int *b = &a;
a = 1;
if (*b != 1)
abort ();
return 0;
}
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18241
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2004-10-31 1:03 [Bug tree-optimization/18241] New: linux kernel loop gets miscompiled ak at muc dot de
` (33 preceding siblings ...)
2005-01-03 23:27 ` belyshev at depni dot sinp dot msu dot ru
@ 2005-01-04 0:40 ` pinskia at gcc dot gnu dot org
2005-01-07 15:09 ` dnovillo at gcc dot gnu dot org
` (2 subsequent siblings)
37 siblings, 0 replies; 39+ messages in thread
From: pinskia at gcc dot gnu dot org @ 2005-01-04 0:40 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From pinskia at gcc dot gnu dot org 2005-01-04 00:40 -------
Changing the summary as we finnally found the problem.
--
What |Removed |Added
----------------------------------------------------------------------------
Summary|[4.0 Regression] linux |[4.0 Regression] volatile
|kernel loop gets miscompiled|causes mis-compiling
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18241
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` (34 preceding siblings ...)
2005-01-04 0:40 ` [Bug tree-optimization/18241] [4.0 Regression] volatile causes mis-compiling pinskia at gcc dot gnu dot org
@ 2005-01-07 15:09 ` dnovillo at gcc dot gnu dot org
2005-01-07 18:43 ` giovannibajo at libero dot it
2005-01-08 18:47 ` dnovillo at gcc dot gnu dot org
37 siblings, 0 replies; 39+ messages in thread
From: dnovillo at gcc dot gnu dot org @ 2005-01-07 15:09 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From dnovillo at gcc dot gnu dot org 2005-01-07 15:09 -------
BTW, the original case is no longer reproducible on mainline, but the test in
#35 still fails.
This happens when a pointer to volatile storage takes the address of a variable.
One way to fix this is by marking variables that have been aliased with
volatile tags. When adding operands for these variables, we mark the statement
as having volatile operands. While correct, this tends to pessimize code. I'm
working on a variant of this patch that would only mark variables whose address
is taken by a pointer pointing to volatile memory.
Jeff has been working on the idea of exposing volatile operands to the
optimizers and make the optimizers responsible for dealing with them properly.
This has the advantage that we would not have any magic operands hidden from us,
but it requires auditing all the optimizers to make sure that they don't mess
things up.
Given the stage that we are for 4.0, it may be better to go with the simpler
solution. But perhaps we can finish the other approach in time.
Diego.
Index: tree-flow.h
===================================================================
RCS file: /cvs/gcc/gcc/gcc/tree-flow.h,v
retrieving revision 2.75
diff -d -c -p -u -r2.75 tree-flow.h
--- tree-flow.h 10 Dec 2004 21:54:41 -0000 2.75
+++ tree-flow.h 5 Jan 2005 00:06:23 -0000
@@ -174,6 +174,9 @@ struct var_ann_d GTY(())
in the v_may_def list. */
unsigned in_v_may_def_list : 1;
+ /* Nonzero if this variable is aliased to a volatile variable. */
+ unsigned aliased_with_volatile : 1;
+
/* An artificial variable representing the memory location pointed-to by
all the pointers that TBAA (type-based alias analysis) considers
to be aliased. If the variable is not a pointer or if it is never
Index: tree-ssa-alias.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/tree-ssa-alias.c,v
retrieving revision 2.64
diff -d -c -p -u -r2.64 tree-ssa-alias.c
--- tree-ssa-alias.c 20 Dec 2004 18:18:28 -0000 2.64
+++ tree-ssa-alias.c 5 Jan 2005 00:06:24 -0000
@@ -1668,6 +1668,9 @@ add_may_alias (tree var, tree alias)
else if (is_call_clobbered (alias))
mark_call_clobbered (var);
+ if (TREE_THIS_VOLATILE (var))
+ a_ann->aliased_with_volatile = 1;
+
VARRAY_PUSH_TREE (v_ann->may_aliases, alias);
a_ann->is_alias_tag = 1;
}
Index: tree-ssa-operands.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/tree-ssa-operands.c,v
retrieving revision 2.60
diff -d -c -p -u -r2.60 tree-ssa-operands.c
--- tree-ssa-operands.c 10 Dec 2004 17:28:32 -0000 2.60
+++ tree-ssa-operands.c 5 Jan 2005 00:06:24 -0000
@@ -1528,6 +1528,9 @@ add_stmt_operand (tree *var_p, stmt_ann_
return;
}
+ if (v_ann->aliased_with_volatile && s_ann)
+ s_ann->has_volatile_ops = true;
+
if (is_real_op)
{
/* The variable is a GIMPLE register. Add it to real operands. */
--
What |Removed |Added
----------------------------------------------------------------------------
CC|dnovillo at gcc dot gnu dot |
|org |
AssignedTo|unassigned at gcc dot gnu |dnovillo at gcc dot gnu dot
|dot org |org
Status|NEW |ASSIGNED
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18241
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2004-10-31 1:03 [Bug tree-optimization/18241] New: linux kernel loop gets miscompiled ak at muc dot de
` (35 preceding siblings ...)
2005-01-07 15:09 ` dnovillo at gcc dot gnu dot org
@ 2005-01-07 18:43 ` giovannibajo at libero dot it
2005-01-08 18:47 ` dnovillo at gcc dot gnu dot org
37 siblings, 0 replies; 39+ messages in thread
From: giovannibajo at libero dot it @ 2005-01-07 18:43 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From giovannibajo at libero dot it 2005-01-07 18:43 -------
*** Bug 19316 has been marked as a duplicate of this bug. ***
--
What |Removed |Added
----------------------------------------------------------------------------
CC| |pluto at pld-linux dot org
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18241
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2004-10-31 1:03 [Bug tree-optimization/18241] New: linux kernel loop gets miscompiled ak at muc dot de
` (36 preceding siblings ...)
2005-01-07 18:43 ` giovannibajo at libero dot it
@ 2005-01-08 18:47 ` dnovillo at gcc dot gnu dot org
37 siblings, 0 replies; 39+ messages in thread
From: dnovillo at gcc dot gnu dot org @ 2005-01-08 18:47 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From dnovillo at gcc dot gnu dot org 2005-01-08 18:47 -------
Fix: http://gcc.gnu.org/ml/gcc-patches/2005-01/msg00451.html
--
What |Removed |Added
----------------------------------------------------------------------------
Status|ASSIGNED |RESOLVED
Resolution| |FIXED
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18241
^ permalink raw reply [flat|nested] 39+ messages in thread