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* [Bug tree-optimization/43423] gcc should vectorize this loop through if-conversion
[not found] <bug-43423-4@http.gcc.gnu.org/bugzilla/>
@ 2021-07-20 2:47 ` pinskia at gcc dot gnu.org
2021-09-14 6:34 ` pinskia at gcc dot gnu.org
1 sibling, 0 replies; 8+ messages in thread
From: pinskia at gcc dot gnu.org @ 2021-07-20 2:47 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=43423
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |ASSIGNED
Severity|normal |enhancement
CC| |pinskia at gcc dot gnu.org
--- Comment #13 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
The improvement in comment #12 is something which I am working on.
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug tree-optimization/43423] gcc should vectorize this loop through if-conversion
[not found] <bug-43423-4@http.gcc.gnu.org/bugzilla/>
2021-07-20 2:47 ` [Bug tree-optimization/43423] gcc should vectorize this loop through if-conversion pinskia at gcc dot gnu.org
@ 2021-09-14 6:34 ` pinskia at gcc dot gnu.org
1 sibling, 0 replies; 8+ messages in thread
From: pinskia at gcc dot gnu.org @ 2021-09-14 6:34 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=43423
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Resolution|--- |FIXED
Target Milestone|--- |7.0
Status|ASSIGNED |RESOLVED
--- Comment #14 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
So GCC 7 is able to optimize this loop fully and split it into two at -O3
(r7-3966) after my comment #12.
Also starting with GCC 7, we were able to vectorize the loop at -O2
-ftree-vectorize since tree-if-conv.c can do the ifconversion (I don't have the
revision).
So this is all fixed anyways.
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug tree-optimization/43423] gcc should vectorize this loop through if-conversion
2010-03-18 18:01 [Bug c/43423] New: gcc should vectorize this loop through "iteration range splitting" changpeng dot fang at amd dot com
` (4 preceding siblings ...)
2010-05-24 23:02 ` spop at gcc dot gnu dot org
@ 2010-05-25 23:33 ` spop at gcc dot gnu dot org
5 siblings, 0 replies; 8+ messages in thread
From: spop at gcc dot gnu dot org @ 2010-05-25 23:33 UTC (permalink / raw)
To: gcc-bugs
------- Comment #11 from spop at gcc dot gnu dot org 2010-05-25 23:33 -------
This is not a IV type problem: the number of iterations may be zero when mid ==
0 or mid == n, so the number of iterations analysis has a condition under which
niter may_be_zero.
I sent out a patch that makes niter return a COND_EXPR
instead of a chrec_dont_know:
http://gcc.gnu.org/ml/gcc-patches/2010-05/msg01927.html
With that patch I now get
note: not vectorized: data ref analysis failed D.2726_51 = a[var.9_55];
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43423
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug tree-optimization/43423] gcc should vectorize this loop through if-conversion
2010-03-18 18:01 [Bug c/43423] New: gcc should vectorize this loop through "iteration range splitting" changpeng dot fang at amd dot com
` (3 preceding siblings ...)
2010-05-24 22:47 ` changpeng dot fang at amd dot com
@ 2010-05-24 23:02 ` spop at gcc dot gnu dot org
2010-05-25 23:33 ` spop at gcc dot gnu dot org
5 siblings, 0 replies; 8+ messages in thread
From: spop at gcc dot gnu dot org @ 2010-05-24 23:02 UTC (permalink / raw)
To: gcc-bugs
------- Comment #10 from spop at gcc dot gnu dot org 2010-05-24 23:02 -------
note: not vectorized: number of iterations cannot be computed.
Graphite has a problem with the generation of induction variables types
that makes the code harder to analyze after Graphite. I will try to get this
fixed to make this loop vectorized with the iteration range splitting that
Graphite does by default.
Sebastian
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43423
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug tree-optimization/43423] gcc should vectorize this loop through if-conversion
2010-03-18 18:01 [Bug c/43423] New: gcc should vectorize this loop through "iteration range splitting" changpeng dot fang at amd dot com
` (2 preceding siblings ...)
2010-05-24 22:44 ` spop at gcc dot gnu dot org
@ 2010-05-24 22:47 ` changpeng dot fang at amd dot com
2010-05-24 23:02 ` spop at gcc dot gnu dot org
2010-05-25 23:33 ` spop at gcc dot gnu dot org
5 siblings, 0 replies; 8+ messages in thread
From: changpeng dot fang at amd dot com @ 2010-05-24 22:47 UTC (permalink / raw)
To: gcc-bugs
------- Comment #9 from changpeng dot fang at amd dot com 2010-05-24 22:47 -------
(In reply to comment #8)
> -fgraphite-identity does iteration splitting for this case.
Do you know why it could not be vectorized after iteration
range splitting?
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43423
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug tree-optimization/43423] gcc should vectorize this loop through if-conversion
2010-03-18 18:01 [Bug c/43423] New: gcc should vectorize this loop through "iteration range splitting" changpeng dot fang at amd dot com
2010-04-08 17:47 ` [Bug tree-optimization/43423] gcc should vectorize this loop through if-conversion spop at gcc dot gnu dot org
2010-05-07 21:41 ` changpeng dot fang at amd dot com
@ 2010-05-24 22:44 ` spop at gcc dot gnu dot org
2010-05-24 22:47 ` changpeng dot fang at amd dot com
` (2 subsequent siblings)
5 siblings, 0 replies; 8+ messages in thread
From: spop at gcc dot gnu dot org @ 2010-05-24 22:44 UTC (permalink / raw)
To: gcc-bugs
------- Comment #8 from spop at gcc dot gnu dot org 2010-05-24 22:44 -------
-fgraphite-identity does iteration splitting for this case.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43423
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug tree-optimization/43423] gcc should vectorize this loop through if-conversion
2010-03-18 18:01 [Bug c/43423] New: gcc should vectorize this loop through "iteration range splitting" changpeng dot fang at amd dot com
2010-04-08 17:47 ` [Bug tree-optimization/43423] gcc should vectorize this loop through if-conversion spop at gcc dot gnu dot org
@ 2010-05-07 21:41 ` changpeng dot fang at amd dot com
2010-05-24 22:44 ` spop at gcc dot gnu dot org
` (3 subsequent siblings)
5 siblings, 0 replies; 8+ messages in thread
From: changpeng dot fang at amd dot com @ 2010-05-07 21:41 UTC (permalink / raw)
To: gcc-bugs
------- Comment #7 from changpeng dot fang at amd dot com 2010-05-07 21:41 -------
(In reply to comment #4)
> (In reply to comment #3)
> > Subject: Re: gcc should vectorize this loop
> > through "iteration range splitting"
> > You mean that the problem is the if-conversion of the stores
> > "a[i] = ..."
>
> If we rewrite the code like:
> int a[100], b[100], c[100];
>
> void foo(int n, int mid)
> {
> int i;
> for(i=0; i<n; i++)
> {
> int t;
> int ai = a[i], bi = b[i], ci = c[i];
> if (i < mid)
> t = ai + bi;
> else
> t = ai + ci;
> a[i] = t;
> }
> }
>
> --- CUT ---
> This gets vectorized as we produce an if-cvt first.
>
There are both correctness and performance issues in the re-written code.
b[i] or c[i] may not be executed in the original loop.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43423
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug tree-optimization/43423] gcc should vectorize this loop through if-conversion
2010-03-18 18:01 [Bug c/43423] New: gcc should vectorize this loop through "iteration range splitting" changpeng dot fang at amd dot com
@ 2010-04-08 17:47 ` spop at gcc dot gnu dot org
2010-05-07 21:41 ` changpeng dot fang at amd dot com
` (4 subsequent siblings)
5 siblings, 0 replies; 8+ messages in thread
From: spop at gcc dot gnu dot org @ 2010-04-08 17:47 UTC (permalink / raw)
To: gcc-bugs
------- Comment #6 from spop at gcc dot gnu dot org 2010-04-08 17:47 -------
I changed the title of this bug to match the comments in the PR:
we should vectorize this loop using if-conversion, and not "iteration
range splitting".
Also note that in general, by doing an "iteration range splitting" the data
locality in the two loops could be worse than in the if-converted loop.
--
spop at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
Summary|gcc should vectorize this |gcc should vectorize this
|loop through "iteration |loop through if-conversion
|range splitting" |
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43423
^ permalink raw reply [flat|nested] 8+ messages in thread
end of thread, other threads:[~2021-09-14 6:34 UTC | newest]
Thread overview: 8+ messages (download: mbox.gz / follow: Atom feed)
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[not found] <bug-43423-4@http.gcc.gnu.org/bugzilla/>
2021-07-20 2:47 ` [Bug tree-optimization/43423] gcc should vectorize this loop through if-conversion pinskia at gcc dot gnu.org
2021-09-14 6:34 ` pinskia at gcc dot gnu.org
2010-03-18 18:01 [Bug c/43423] New: gcc should vectorize this loop through "iteration range splitting" changpeng dot fang at amd dot com
2010-04-08 17:47 ` [Bug tree-optimization/43423] gcc should vectorize this loop through if-conversion spop at gcc dot gnu dot org
2010-05-07 21:41 ` changpeng dot fang at amd dot com
2010-05-24 22:44 ` spop at gcc dot gnu dot org
2010-05-24 22:47 ` changpeng dot fang at amd dot com
2010-05-24 23:02 ` spop at gcc dot gnu dot org
2010-05-25 23:33 ` spop at gcc dot gnu dot org
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