* [Bug tree-optimization/96043] BB vectorizer costing lumps everything together
2020-07-03 9:11 [Bug tree-optimization/96043] New: BB vectorizer costing lumps everything together rguenth at gcc dot gnu.org
@ 2020-07-03 14:33 ` marxin at gcc dot gnu.org
2020-09-08 9:06 ` rguenth at gcc dot gnu.org
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From: marxin at gcc dot gnu.org @ 2020-07-03 14:33 UTC (permalink / raw)
To: gcc-bugs
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Martin Liška <marxin at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Ever confirmed|0 |1
Assignee|unassigned at gcc dot gnu.org |marxin at gcc dot gnu.org
Target Milestone|--- |11.0
Status|UNCONFIRMED |ASSIGNED
Last reconfirmed| |2020-07-03
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2020-07-03 9:11 [Bug tree-optimization/96043] New: BB vectorizer costing lumps everything together rguenth at gcc dot gnu.org
2020-07-03 14:33 ` [Bug tree-optimization/96043] " marxin at gcc dot gnu.org
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From: rguenth at gcc dot gnu.org @ 2020-09-08 9:06 UTC (permalink / raw)
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Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Assignee|marxin at gcc dot gnu.org |rguenth at gcc dot gnu.org
--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
So with BB vectorization of non-stores
double a[4];
double x, y;
void bar (double, double);
void foo(double a0, double a1, double a2, double a3)
{
double tem1 = a0 + a2 + 1.;
double tem2 = a1 + a3 + 2.;
x = tem1;
y = tem2;
}
becomes profitable by inserting an unrelated opportunity:
double a[4];
double x, y;
void bar (double, double);
void foo(double a0, double a1, double a2, double a3)
{
double tem1 = a0 + a2 + 1.;
double tem2 = a1 + a3 + 2.;
x = tem1;
y = tem2;
a[0] += a[2];
a[1] += a[3];
}
there's the "complication" that the independent SLP graph components are
not solely formed by the SLP graph nodes and edges but instead we have to
consider scalar stmts as connection between SLP graphs because of the
way scalar costing works. Also "shared" external nodes shouldn't
be considered tieing two SLP graph components together.
Mine.
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2020-07-03 9:11 [Bug tree-optimization/96043] New: BB vectorizer costing lumps everything together rguenth at gcc dot gnu.org
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--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> ---
I have a patch.
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2020-07-03 9:11 [Bug tree-optimization/96043] New: BB vectorizer costing lumps everything together rguenth at gcc dot gnu.org
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From: rguenth at gcc dot gnu.org @ 2020-09-08 14:11 UTC (permalink / raw)
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--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
Turns out gcc.dg/vect/costmodel/x86_64/costmodel-pr69297.c can be massaged to
such case.
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--- Comment #4 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:47ddf4c7b1d4471cb9534f27844ab5e4279c2168
commit r11-3095-g47ddf4c7b1d4471cb9534f27844ab5e4279c2168
Author: Richard Biener <rguenther@suse.de>
Date: Tue Sep 8 14:49:59 2020 +0200
tree-optimization/96043 - BB vectorization costing improvement
This makes the BB vectorizer cost independent SLP subgraphs
separately. While on pristine trunk and for x86_64 I failed to
distill a testcase where the vectorizer would think _any_
basic-block vectorization opportunity is not profitable I do
have pending work that would make the cost savings of a
profitable opportunity make another independently not
profitable opportunity vectorized.
2020-09-08 Richard Biener <rguenther@suse.de>
PR tree-optimization/96043
* tree-vectorizer.h (_slp_instance::cost_vec): New.
(_slp_instance::subgraph_entries): Likewise.
(BB_VINFO_TARGET_COST_DATA): Remove.
* tree-vect-slp.c (vect_free_slp_instance): Free
cost_vec and subgraph_entries.
(vect_analyze_slp_instance): Initialize them.
(vect_slp_analyze_operations): Defer passing costs to
the target, instead record them in the SLP graph entry.
(get_ultimate_leader): New helper for graph partitioning.
(vect_bb_partition_graph_r): Likewise.
(vect_bb_partition_graph): New function to partition the
SLP graph into independently costable parts.
(vect_bb_vectorization_profitable_p): Adjust to work on
a subgraph.
(vect_bb_vectorization_profitable_p): New wrapper,
discarding non-profitable vectorization of subgraphs.
(vect_slp_analyze_bb_1): Call vect_bb_partition_graph before
costing.
* gcc.dg/vect/costmodel/x86_64/costmodel-pr69297.c: Adjust.
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2020-07-03 9:11 [Bug tree-optimization/96043] New: BB vectorizer costing lumps everything together rguenth at gcc dot gnu.org
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Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Resolution|--- |FIXED
Status|ASSIGNED |RESOLVED
--- Comment #5 from Richard Biener <rguenth at gcc dot gnu.org> ---
Fixed on trunk.
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2020-07-03 9:11 [Bug tree-optimization/96043] New: BB vectorizer costing lumps everything together rguenth at gcc dot gnu.org
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From: tnfchris at gcc dot gnu.org @ 2020-09-11 9:41 UTC (permalink / raw)
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Tamar Christina <tnfchris at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |tnfchris at gcc dot gnu.org
--- Comment #6 from Tamar Christina <tnfchris at gcc dot gnu.org> ---
Hi Richi,
This change seems to have caused a few of our vectorization benchmarks to slow
down including x264 which slowed down about 7%.
I can see similar slowdowns on x86
https://lnt.opensuse.org/db_default/v4/SPEC/12977
https://lnt.opensuse.org/db_default/v4/SPEC/12978
was this expected and we should fiddle with the cost model to recover these?
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From: rguenth at gcc dot gnu.org @ 2020-09-11 9:53 UTC (permalink / raw)
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--- Comment #7 from Richard Biener <rguenth at gcc dot gnu.org> ---
(In reply to Tamar Christina from comment #6)
> Hi Richi,
>
> This change seems to have caused a few of our vectorization benchmarks to
> slow down including x264 which slowed down about 7%.
>
> I can see similar slowdowns on x86
> https://lnt.opensuse.org/db_default/v4/SPEC/12977
> https://lnt.opensuse.org/db_default/v4/SPEC/12978
>
> was this expected and we should fiddle with the cost model to recover these?
That wasn't expected - can you open a new bugreport please? Ideally we'd have
a testcase to look at of course.
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From: tnfchris at gcc dot gnu.org @ 2020-09-11 10:01 UTC (permalink / raw)
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--- Comment #8 from Tamar Christina <tnfchris at gcc dot gnu.org> ---
(In reply to Richard Biener from comment #7)
> (In reply to Tamar Christina from comment #6)
> > Hi Richi,
> >
> > This change seems to have caused a few of our vectorization benchmarks to
> > slow down including x264 which slowed down about 7%.
> >
> > I can see similar slowdowns on x86
> > https://lnt.opensuse.org/db_default/v4/SPEC/12977
> > https://lnt.opensuse.org/db_default/v4/SPEC/12978
> >
> > was this expected and we should fiddle with the cost model to recover these?
>
> That wasn't expected - can you open a new bugreport please? Ideally we'd
> have
> a testcase to look at of course.
Sure, will do, I'll try to isolate the function that changed to make a
testcase.
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