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* [Bug tree-optimization/97760] New: GCC outputs wrong values when compiling the testcase with -O3
@ 2020-11-09 2:58 yangyang305 at huawei dot com
2020-11-09 3:01 ` [Bug tree-optimization/97760] " yangyang305 at huawei dot com
` (8 more replies)
0 siblings, 9 replies; 10+ messages in thread
From: yangyang305 at huawei dot com @ 2020-11-09 2:58 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97760
Bug ID: 97760
Summary: GCC outputs wrong values when compiling the testcase
with -O3
Product: gcc
Version: 11.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: yangyang305 at huawei dot com
Target Milestone: ---
Hi, gcc-trunk outputs wrong values when compiling the attached testcase with
-O3.
gcc -O0 test.c -w && ./a.out
159,150,150
150
gcc -O3 test.c -w && ./a.out
159,123,123
123
GCC version: 11.0.0 20201106 (experimental)
^ permalink raw reply [flat|nested] 10+ messages in thread
* [Bug tree-optimization/97760] GCC outputs wrong values when compiling the testcase with -O3
2020-11-09 2:58 [Bug tree-optimization/97760] New: GCC outputs wrong values when compiling the testcase with -O3 yangyang305 at huawei dot com
@ 2020-11-09 3:01 ` yangyang305 at huawei dot com
2020-11-09 8:13 ` [Bug tree-optimization/97760] [10/11 Regression] GCC outputs wrong values when compiling the testcase with -O3 since r10-4200-gb7ff7cef5005721e marxin at gcc dot gnu.org
` (7 subsequent siblings)
8 siblings, 0 replies; 10+ messages in thread
From: yangyang305 at huawei dot com @ 2020-11-09 3:01 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97760
--- Comment #1 from yangyang <yangyang305 at huawei dot com> ---
Created attachment 49521
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=49521&action=edit
testcase
^ permalink raw reply [flat|nested] 10+ messages in thread
* [Bug tree-optimization/97760] [10/11 Regression] GCC outputs wrong values when compiling the testcase with -O3 since r10-4200-gb7ff7cef5005721e
2020-11-09 2:58 [Bug tree-optimization/97760] New: GCC outputs wrong values when compiling the testcase with -O3 yangyang305 at huawei dot com
2020-11-09 3:01 ` [Bug tree-optimization/97760] " yangyang305 at huawei dot com
@ 2020-11-09 8:13 ` marxin at gcc dot gnu.org
2020-11-09 8:17 ` rguenth at gcc dot gnu.org
` (6 subsequent siblings)
8 siblings, 0 replies; 10+ messages in thread
From: marxin at gcc dot gnu.org @ 2020-11-09 8:13 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97760
Martin Liška <marxin at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Ever confirmed|0 |1
Summary|GCC outputs wrong values |[10/11 Regression] GCC
|when compiling the testcase |outputs wrong values when
|with -O3 |compiling the testcase with
| |-O3 since
| |r10-4200-gb7ff7cef5005721e
Priority|P3 |P1
Status|UNCONFIRMED |NEW
CC| |marxin at gcc dot gnu.org,
| |rguenth at gcc dot gnu.org
Target Milestone|--- |10.3
Keywords| |wrong-code
Last reconfirmed| |2020-11-09
--- Comment #2 from Martin Liška <marxin at gcc dot gnu.org> ---
Confirmed, started with r10-4200-gb7ff7cef5005721e.
^ permalink raw reply [flat|nested] 10+ messages in thread
* [Bug tree-optimization/97760] [10/11 Regression] GCC outputs wrong values when compiling the testcase with -O3 since r10-4200-gb7ff7cef5005721e
2020-11-09 2:58 [Bug tree-optimization/97760] New: GCC outputs wrong values when compiling the testcase with -O3 yangyang305 at huawei dot com
2020-11-09 3:01 ` [Bug tree-optimization/97760] " yangyang305 at huawei dot com
2020-11-09 8:13 ` [Bug tree-optimization/97760] [10/11 Regression] GCC outputs wrong values when compiling the testcase with -O3 since r10-4200-gb7ff7cef5005721e marxin at gcc dot gnu.org
@ 2020-11-09 8:17 ` rguenth at gcc dot gnu.org
2020-11-09 13:38 ` rguenth at gcc dot gnu.org
` (5 subsequent siblings)
8 siblings, 0 replies; 10+ messages in thread
From: rguenth at gcc dot gnu.org @ 2020-11-09 8:17 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97760
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Assignee|unassigned at gcc dot gnu.org |rguenth at gcc dot gnu.org
Status|NEW |ASSIGNED
Priority|P1 |P2
--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
Mine.
^ permalink raw reply [flat|nested] 10+ messages in thread
* [Bug tree-optimization/97760] [10/11 Regression] GCC outputs wrong values when compiling the testcase with -O3 since r10-4200-gb7ff7cef5005721e
2020-11-09 2:58 [Bug tree-optimization/97760] New: GCC outputs wrong values when compiling the testcase with -O3 yangyang305 at huawei dot com
` (2 preceding siblings ...)
2020-11-09 8:17 ` rguenth at gcc dot gnu.org
@ 2020-11-09 13:38 ` rguenth at gcc dot gnu.org
2020-11-09 14:19 ` rguenth at gcc dot gnu.org
` (4 subsequent siblings)
8 siblings, 0 replies; 10+ messages in thread
From: rguenth at gcc dot gnu.org @ 2020-11-09 13:38 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97760
--- Comment #4 from Richard Biener <rguenth at gcc dot gnu.org> ---
int b=1;
static int *g = &b;
void __attribute__((noipa))
h (unsigned int n)
{
int i = 3;
int f = 3;
for (; f <= 50; f += 4) {
i += 4;
*g = i;
i += n;
}
}
int main ()
{
h (9);
if (*g != 150 || b != 150)
__builtin_abort ();
return 0;
}
^ permalink raw reply [flat|nested] 10+ messages in thread
* [Bug tree-optimization/97760] [10/11 Regression] GCC outputs wrong values when compiling the testcase with -O3 since r10-4200-gb7ff7cef5005721e
2020-11-09 2:58 [Bug tree-optimization/97760] New: GCC outputs wrong values when compiling the testcase with -O3 yangyang305 at huawei dot com
` (3 preceding siblings ...)
2020-11-09 13:38 ` rguenth at gcc dot gnu.org
@ 2020-11-09 14:19 ` rguenth at gcc dot gnu.org
2020-11-10 9:18 ` cvs-commit at gcc dot gnu.org
` (3 subsequent siblings)
8 siblings, 0 replies; 10+ messages in thread
From: rguenth at gcc dot gnu.org @ 2020-11-09 14:19 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97760
--- Comment #5 from Richard Biener <rguenth at gcc dot gnu.org> ---
t.c:9:12: note: worklist: examine stmt: i_16 = PHI <i_11(5), 3(2)>
t.c:9:12: note: vect_is_simple_use: operand (int) _3, type of def: reduction
t.c:9:12: note: reduc-stmt defining reduc-phi in the same nest.
t.c:9:12: note: mark relevant 1, live 1: i_11 = (int) _3;
so reduc PHI defs are marked live magically - that's obviously wrong here,
the live stmt is one in the middle of the reduction path (which _is_ marked
live). What happens is that we generate two vectorized epilogues and depending
on the order we end up with the wrong result in b.
Now, what's _also_ wrong is that we cannot handle this situation since
the epilogue of the middle stmt fails to account for the all-but-the-last
lane effect of the _not_ live stmt.
While the former bug is easy to fix the latter is not.
I have a patch.
^ permalink raw reply [flat|nested] 10+ messages in thread
* [Bug tree-optimization/97760] [10/11 Regression] GCC outputs wrong values when compiling the testcase with -O3 since r10-4200-gb7ff7cef5005721e
2020-11-09 2:58 [Bug tree-optimization/97760] New: GCC outputs wrong values when compiling the testcase with -O3 yangyang305 at huawei dot com
` (4 preceding siblings ...)
2020-11-09 14:19 ` rguenth at gcc dot gnu.org
@ 2020-11-10 9:18 ` cvs-commit at gcc dot gnu.org
2020-11-10 9:22 ` [Bug tree-optimization/97760] [10 " rguenth at gcc dot gnu.org
` (2 subsequent siblings)
8 siblings, 0 replies; 10+ messages in thread
From: cvs-commit at gcc dot gnu.org @ 2020-11-10 9:18 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97760
--- Comment #6 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Richard Biener <rguenth@gcc.gnu.org>:
https://gcc.gnu.org/g:2686de5617bfb572343933be2883e8274c9735b5
commit r11-4865-g2686de5617bfb572343933be2883e8274c9735b5
Author: Richard Biener <rguenther@suse.de>
Date: Mon Nov 9 15:19:56 2020 +0100
tree-optimization/97760 - reduction paths with unhandled live stmt
This makes sure we reject reduction paths with a live stmt that
is not the last one altering the value. This is because we do not
handle this in the epilogue unless there's a scalar epilogue loop.
2020-11-09 Richard Biener <rguenther@suse.de>
PR tree-optimization/97760
* tree-vect-loop.c (check_reduction_path): Reject
reduction paths we do not handle in epilogue generation.
* gcc.dg/vect/pr97760.c: New testcase.
^ permalink raw reply [flat|nested] 10+ messages in thread
* [Bug tree-optimization/97760] [10 Regression] GCC outputs wrong values when compiling the testcase with -O3 since r10-4200-gb7ff7cef5005721e
2020-11-09 2:58 [Bug tree-optimization/97760] New: GCC outputs wrong values when compiling the testcase with -O3 yangyang305 at huawei dot com
` (5 preceding siblings ...)
2020-11-10 9:18 ` cvs-commit at gcc dot gnu.org
@ 2020-11-10 9:22 ` rguenth at gcc dot gnu.org
2020-12-01 15:44 ` cvs-commit at gcc dot gnu.org
2020-12-01 15:45 ` rguenth at gcc dot gnu.org
8 siblings, 0 replies; 10+ messages in thread
From: rguenth at gcc dot gnu.org @ 2020-11-10 9:22 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97760
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Summary|[10/11 Regression] GCC |[10 Regression] GCC outputs
|outputs wrong values when |wrong values when compiling
|compiling the testcase with |the testcase with -O3 since
|-O3 since |r10-4200-gb7ff7cef5005721e
|r10-4200-gb7ff7cef5005721e |
Known to fail|11.0 |
Known to work| |11.0
--- Comment #7 from Richard Biener <rguenth at gcc dot gnu.org> ---
Fixed on trunk sofar.
^ permalink raw reply [flat|nested] 10+ messages in thread
* [Bug tree-optimization/97760] [10 Regression] GCC outputs wrong values when compiling the testcase with -O3 since r10-4200-gb7ff7cef5005721e
2020-11-09 2:58 [Bug tree-optimization/97760] New: GCC outputs wrong values when compiling the testcase with -O3 yangyang305 at huawei dot com
` (6 preceding siblings ...)
2020-11-10 9:22 ` [Bug tree-optimization/97760] [10 " rguenth at gcc dot gnu.org
@ 2020-12-01 15:44 ` cvs-commit at gcc dot gnu.org
2020-12-01 15:45 ` rguenth at gcc dot gnu.org
8 siblings, 0 replies; 10+ messages in thread
From: cvs-commit at gcc dot gnu.org @ 2020-12-01 15:44 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97760
--- Comment #8 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-10 branch has been updated by Richard Biener
<rguenth@gcc.gnu.org>:
https://gcc.gnu.org/g:7b523f3dff5d7bf49294fe5b794f63cae28d5c5b
commit r10-9102-g7b523f3dff5d7bf49294fe5b794f63cae28d5c5b
Author: Richard Biener <rguenther@suse.de>
Date: Mon Nov 9 15:19:56 2020 +0100
tree-optimization/97760 - reduction paths with unhandled live stmt
This makes sure we reject reduction paths with a live stmt that
is not the last one altering the value. This is because we do not
handle this in the epilogue unless there's a scalar epilogue loop.
2020-11-09 Richard Biener <rguenther@suse.de>
PR tree-optimization/97760
* tree-vect-loop.c (check_reduction_path): Reject
reduction paths we do not handle in epilogue generation.
* gcc.dg/vect/pr97760.c: New testcase.
(cherry picked from commit 2686de5617bfb572343933be2883e8274c9735b5)
^ permalink raw reply [flat|nested] 10+ messages in thread
* [Bug tree-optimization/97760] [10 Regression] GCC outputs wrong values when compiling the testcase with -O3 since r10-4200-gb7ff7cef5005721e
2020-11-09 2:58 [Bug tree-optimization/97760] New: GCC outputs wrong values when compiling the testcase with -O3 yangyang305 at huawei dot com
` (7 preceding siblings ...)
2020-12-01 15:44 ` cvs-commit at gcc dot gnu.org
@ 2020-12-01 15:45 ` rguenth at gcc dot gnu.org
8 siblings, 0 replies; 10+ messages in thread
From: rguenth at gcc dot gnu.org @ 2020-12-01 15:45 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97760
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Known to work| |10.2.1
Resolution|--- |FIXED
Status|ASSIGNED |RESOLVED
--- Comment #9 from Richard Biener <rguenth at gcc dot gnu.org> ---
Fixed.
^ permalink raw reply [flat|nested] 10+ messages in thread
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2020-11-09 2:58 [Bug tree-optimization/97760] New: GCC outputs wrong values when compiling the testcase with -O3 yangyang305 at huawei dot com
2020-11-09 3:01 ` [Bug tree-optimization/97760] " yangyang305 at huawei dot com
2020-11-09 8:13 ` [Bug tree-optimization/97760] [10/11 Regression] GCC outputs wrong values when compiling the testcase with -O3 since r10-4200-gb7ff7cef5005721e marxin at gcc dot gnu.org
2020-11-09 8:17 ` rguenth at gcc dot gnu.org
2020-11-09 13:38 ` rguenth at gcc dot gnu.org
2020-11-09 14:19 ` rguenth at gcc dot gnu.org
2020-11-10 9:18 ` cvs-commit at gcc dot gnu.org
2020-11-10 9:22 ` [Bug tree-optimization/97760] [10 " rguenth at gcc dot gnu.org
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