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Chandler Carruth via llvm-dev

2017-Oct-18 06:50 UTC

[llvm-dev] RFC: Switching to the new pass manager by default

Greetings everyone!

The new pass manager is getting extremely close to the point where I'm not
aware of any significant outstanding work needed, and I'd like to see what
else would be needed to enable it by default. Here are the current
functionality I'm aware of outstanding:

1) Does not do non-trivial loop unswitching. Majority of this is in
https://reviews.llvm.org/D34200 but will need one or two small follow-ups.

2) Currently, sanitizers don't work correctly with it. Thanks to the work
of others, the missing infrastructure has been added and I'll send a patch
to wire this up this week.

3) Missing support for 'optnone'. I've been working on this, but the
existing testing wasn't as thorough as I wanted, so it is going slowly.
I've got about 1/4 of this implemented and should have patches this week or
next.

4) Missing opt-bisect (or similar) facility. This looks pretty trivial to
add, but I've not even started. If anyone is interested in it, go for it.
We might even be able to do something simpler using the generic debug
counters and get equivalent functionality.

... that's it?

Optimization quality / run-time performance:
- We've been using it at Google extensively and are very happy with the
optimization quality. Benchmarks look *very* good here.
- More data from other users would be important.
- You can try it out with `-fexperimental-new-pass-manager` to Clang

Compile-time performance:
- Sometimes *much* better due to cached analyses.
- Sometimes worse, typically due to more / different inlining in turn
running main pipeline (GVN + InstCombine) more times or over more code.
- Overall somewhat a wash, but the increased compile times typically due to
the optimizer "trying" harder, so not too concerning on our end.
- Again, more feedback from other users good:
`-fexperimental-new-pass-manager` to Clang

Once the four missing things land, I'll also happily work on collecting
some of the basics on the test-suite and CTMark. But I suspect more "in the
wild" data would really be useful here given the significance of the
change.

Thoughts? What else (beyond the four items above and feedback on run-time
and compile-time) would folks like to see?

Once this happens, I'll also be preparing some batch, mechanical updates to
the test suite to primarily use the new pass manager. Also there is lots of
documentation updates that will be needed here.

-Chandler

PS: I'll be sending a note to cfe-dev as a "heads up" about this
discussion
as in some ways, the default flip is mostly a Clang default flip. But
hopefully our doc updates will trigger this being "perceived" as the
default for other frontends, and I'll try to reach out to other major
frontends as well (Swift and Rust are on my radar, and I've already started
talking with Philip Reames about their Falcon JIT).
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ORiordan, Martin via llvm-dev

2017-Oct-18 09:28 UTC

head link

[llvm-dev] RFC: Switching to the new pass manager by default

Hi Chandler,

I don’t track the head revisions, instead I do a “Big Bang” update with each
6-month formal release of the LLVM suite, and I am now at v5.0.

Is the implementation of the new pass manager in LLVM v5.0 suitable for me to
usefully experiment with it so as to provide feedback, or should I wait and try
it out with v6.0?

Thanks,

            MartinO

From: llvm-dev [mailto:llvm-dev-bounces at lists.llvm.org] On Behalf Of Chandler
Carruth via llvm-dev
Sent: Wednesday, October 18, 2017 7:51 AM
To: llvm-dev <llvm-dev at lists.llvm.org>
Subject: [llvm-dev] RFC: Switching to the new pass manager by default

Greetings everyone!

The new pass manager is getting extremely close to the point where I'm not
aware of any significant outstanding work needed, and I'd like to see what
else would be needed to enable it by default. Here are the current functionality
I'm aware of outstanding:

1) Does not do non-trivial loop unswitching. Majority of this is in
https://reviews.llvm.org/D34200 but will need one or two small follow-ups.

2) Currently, sanitizers don't work correctly with it. Thanks to the work of
others, the missing infrastructure has been added and I'll send a patch to
wire this up this week.

3) Missing support for 'optnone'. I've been working on this, but the
existing testing wasn't as thorough as I wanted, so it is going slowly.
I've got about 1/4 of this implemented and should have patches this week or
next.

4) Missing opt-bisect (or similar) facility. This looks pretty trivial to add,
but I've not even started. If anyone is interested in it, go for it. We
might even be able to do something simpler using the generic debug counters and
get equivalent functionality.

... that's it?

Optimization quality / run-time performance:
- We've been using it at Google extensively and are very happy with the
optimization quality. Benchmarks look *very* good here.
- More data from other users would be important.
- You can try it out with `-fexperimental-new-pass-manager` to Clang

Compile-time performance:
- Sometimes *much* better due to cached analyses.
- Sometimes worse, typically due to more / different inlining in turn running
main pipeline (GVN + InstCombine) more times or over more code.
- Overall somewhat a wash, but the increased compile times typically due to the
optimizer "trying" harder, so not too concerning on our end.
- Again, more feedback from other users good: `-fexperimental-new-pass-manager`
to Clang

Once the four missing things land, I'll also happily work on collecting some
of the basics on the test-suite and CTMark. But I suspect more "in the
wild" data would really be useful here given the significance of the
change.

Thoughts? What else (beyond the four items above and feedback on run-time and
compile-time) would folks like to see?

Once this happens, I'll also be preparing some batch, mechanical updates to
the test suite to primarily use the new pass manager. Also there is lots of
documentation updates that will be needed here.

-Chandler

PS: I'll be sending a note to cfe-dev as a "heads up" about this
discussion as in some ways, the default flip is mostly a Clang default flip. But
hopefully our doc updates will trigger this being "perceived" as the
default for other frontends, and I'll try to reach out to other major
frontends as well (Swift and Rust are on my radar, and I've already started
talking with Philip Reames about their Falcon JIT).
--------------------------------------------------------------
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Registered in Ireland
Registered Office: Collinstown Industrial Park, Leixlip, County Kildare
Registered Number: 308263


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Chandler Carruth via llvm-dev

2017-Oct-18 16:36 UTC

head link

[llvm-dev] RFC: Switching to the new pass manager by default

On Wed, Oct 18, 2017 at 2:28 AM ORiordan, Martin via llvm-dev <
llvm-dev at lists.llvm.org> wrote:
> Hi Chandler,
>
>
>
> I don’t track the head revisions, instead I do a “Big Bang” update with
> each 6-month formal release of the LLVM suite, and I am now at v5.0.
>
>
>
> Is the implementation of the new pass manager in LLVM v5.0 suitable for me
> to usefully experiment with it so as to provide feedback, or should I wait
> and try it out with v6.0?
>
Unfortunately, some very important fixes landed after 5.0, and the risk was
too high to cherry-pick them to fix an off-by-default feature. LLVM since
the start of August is in a pretty stable state for testing this stuff.

-Chandler

>
>
> Thanks,
>
>
>
>             MartinO
>
>
>
> *From:* llvm-dev [mailto:llvm-dev-bounces at lists.llvm.org] *On Behalf Of
*Chandler
> Carruth via llvm-dev
> *Sent:* Wednesday, October 18, 2017 7:51 AM
> *To:* llvm-dev <llvm-dev at lists.llvm.org>
> *Subject:* [llvm-dev] RFC: Switching to the new pass manager by default
>
>
>
> Greetings everyone!
>
>
>
> The new pass manager is getting extremely close to the point where I'm
not
> aware of any significant outstanding work needed, and I'd like to see
what
> else would be needed to enable it by default. Here are the current
> functionality I'm aware of outstanding:
>
>
>
> 1) Does not do non-trivial loop unswitching. Majority of this is in
> https://reviews.llvm.org/D34200 but will need one or two small follow-ups.
>
>
>
> 2) Currently, sanitizers don't work correctly with it. Thanks to the
work
> of others, the missing infrastructure has been added and I'll send a
patch
> to wire this up this week.
>
>
>
> 3) Missing support for 'optnone'. I've been working on this,
but the
> existing testing wasn't as thorough as I wanted, so it is going slowly.
> I've got about 1/4 of this implemented and should have patches this
week or
> next.
>
>
>
> 4) Missing opt-bisect (or similar) facility. This looks pretty trivial to
> add, but I've not even started. If anyone is interested in it, go for
it.
> We might even be able to do something simpler using the generic debug
> counters and get equivalent functionality.
>
>
>
> ... that's it?
>
>
>
> Optimization quality / run-time performance:
>
> - We've been using it at Google extensively and are very happy with the
> optimization quality. Benchmarks look *very* good here.
>
> - More data from other users would be important.
>
> - You can try it out with `-fexperimental-new-pass-manager` to Clang
>
>
>
> Compile-time performance:
>
> - Sometimes *much* better due to cached analyses.
>
> - Sometimes worse, typically due to more / different inlining in turn
> running main pipeline (GVN + InstCombine) more times or over more code.
>
> - Overall somewhat a wash, but the increased compile times typically due
> to the optimizer "trying" harder, so not too concerning on our
end.
>
> - Again, more feedback from other users good:
> `-fexperimental-new-pass-manager` to Clang
>
>
>
> Once the four missing things land, I'll also happily work on collecting
> some of the basics on the test-suite and CTMark. But I suspect more
"in the
> wild" data would really be useful here given the significance of the
change.
>
>
>
> Thoughts? What else (beyond the four items above and feedback on run-time
> and compile-time) would folks like to see?
>
>
>
> Once this happens, I'll also be preparing some batch, mechanical
updates
> to the test suite to primarily use the new pass manager. Also there is lots
> of documentation updates that will be needed here.
>
>
>
> -Chandler
>
>
>
> PS: I'll be sending a note to cfe-dev as a "heads up" about
this
> discussion as in some ways, the default flip is mostly a Clang default
> flip. But hopefully our doc updates will trigger this being
"perceived" as
> the default for other frontends, and I'll try to reach out to other
major
> frontends as well (Swift and Rust are on my radar, and I've already
started
> talking with Philip Reames about their Falcon JIT).
>
> --------------------------------------------------------------
> Intel Research and Development Ireland Limited
> Registered in Ireland
> Registered Office: Collinstown Industrial Park, Leixlip, County Kildare
> Registered Number: 308263
>
> This e-mail and any attachments may contain confidential material for the
> sole use of the intended recipient(s). Any review or distribution by others
> is strictly prohibited. If you are not the intended recipient, please
> contact the sender and delete all copies.
>
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
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Joshua Cranmer 🐧 via llvm-dev

2017-Oct-19 03:28 UTC

head link

[llvm-dev] RFC: Switching to the new pass manager by default

On 10/18/2017 2:50 AM, Chandler Carruth via llvm-dev
wrote:> Thoughts? What else (beyond the four items above and feedback on 
> run-time and compile-time) would folks like to see?
I'd say the complete lack of documentation available from the 
http://llvm.org/docs landing page is something that should be remedied 
before the default gets flipped, especially if it impacts running passes 
via opt.

On a related note, what's the expected timeline for removing the old 
pass manager?

-- 
Joshua Cranmer
Thunderbird and DXR developer
Source code archæologist

Michael Kruse via llvm-dev

2017-Oct-19 06:18 UTC

head link

[llvm-dev] RFC: Switching to the new pass manager by default

2017-10-18 8:50 GMT+02:00 Chandler Carruth via llvm-dev
<llvm-dev at lists.llvm.org>:> Optimization quality / run-time performance:
> - We've been using it at Google extensively and are very happy with the
> optimization quality. Benchmarks look *very* good here.
Could you share some details/numbers?

Michael

Greg Bedwell via llvm-dev

2017-Oct-19 11:50 UTC

head link

[llvm-dev] RFC: Switching to the new pass manager by default

I just tried putting a relatively recent version of our merge branch
(r316139 + our local changes) through a small subset of the PS4 testing
with -fexperimental-new-pass-manager enabled.  In general, most tests
passed :).  There are a few failures I'd need to look at in more detail
though.  The most glaring are all our tests related to generating coverage
info:

$ cat 1.cpp
void foo(){}
$ ./build/bin/clang -c -fprofile-instr-generate -fcoverage-mapping 1.cpp
$ ./build/bin/clang -c -fprofile-instr-generate -fcoverage-mapping 1.cpp
-fexperimental-new-pass-manager
instrprof failed to lower an increment
UNREACHABLE executed at
/home/greg/public_git/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp:5893!

which I'm assuming is the same thing as was reported in
https://bugs.llvm.org/show_bug.cgi?id=33773 .  This would definitely be a
prerequisite for us to consider flipping the default.

There are a few tests looking for specific codegen that are seeing
something different.  At a glance, it looks like the output from clang's
-O2 looks roughly similar in some small examples with and without the new
PM, but clang's -O1 is producing very different output.  Whether this is an
issue, I can't say for sure (I've not tried benchmarking the -O1s
against
each other yet).  Is this expected?

I've also got an example of a specific file that shows quite a large
compile time increase with the new PM:

Old PM:
   ---User Time---   --System Time--   --User+System--   ---Wall Time---
--- Name ---
  15.8125 ( 96.0%)   0.2969 ( 95.0%)  16.1094 ( 96.0%)  16.1059 ( 96.1%)
Code Generation Time
   0.6563 (  4.0%)   0.0156 (  5.0%)   0.6719 (  4.0%)   0.6609 (  3.9%)
LLVM IR Generation Time
  16.4688 (100.0%)   0.3125 (100.0%)  16.7813 (100.0%)  16.7668 (100.0%)
Total

New PM:
   ---User Time---   --System Time--   --User+System--   ---Wall Time---
--- Name ---
  67.0781 ( 99.1%)   0.3438 ( 95.7%)  67.4219 ( 99.0%)  67.4543 ( 99.0%)
Code Generation Time
   0.6406 (  0.9%)   0.0156 (  4.3%)   0.6563 (  1.0%)   0.6644 (  1.0%)
LLVM IR Generation Time
  67.7188 (100.0%)   0.3594 (100.0%)  68.0781 (100.0%)  68.1187 (100.0%)
Total

It's not an example I can easily share (and also not one I'm easily able
to
verify in its present state on a branch without our local changes to make
sure they're not responsible somehow), but if it's of interest I can see
whether I can reduce it to something shareable and raise a bug.

If I get a chance, I'll try putting this through some PS4 game codebases to
see how build time and run time performance compare there, but I'm one of
the few manning the fort while most of the rest of the team is out having a
nice time at the Developers' Meeting this week, so I may not get that
chance for a bit.

Cheers,
-Greg


On 18 October 2017 at 07:50, Chandler Carruth via llvm-dev <
llvm-dev at lists.llvm.org> wrote:
> Greetings everyone!
>
> The new pass manager is getting extremely close to the point where I'm
not
> aware of any significant outstanding work needed, and I'd like to see
what
> else would be needed to enable it by default. Here are the current
> functionality I'm aware of outstanding:
>
> 1) Does not do non-trivial loop unswitching. Majority of this is in
> https://reviews.llvm.org/D34200 but will need one or two small follow-ups.
>
> 2) Currently, sanitizers don't work correctly with it. Thanks to the
work
> of others, the missing infrastructure has been added and I'll send a
patch
> to wire this up this week.
>
> 3) Missing support for 'optnone'. I've been working on this,
but the
> existing testing wasn't as thorough as I wanted, so it is going slowly.
> I've got about 1/4 of this implemented and should have patches this
week or
> next.
>
> 4) Missing opt-bisect (or similar) facility. This looks pretty trivial to
> add, but I've not even started. If anyone is interested in it, go for
it.
> We might even be able to do something simpler using the generic debug
> counters and get equivalent functionality.
>
> ... that's it?
>
> Optimization quality / run-time performance:
> - We've been using it at Google extensively and are very happy with the
> optimization quality. Benchmarks look *very* good here.
> - More data from other users would be important.
> - You can try it out with `-fexperimental-new-pass-manager` to Clang
>
> Compile-time performance:
> - Sometimes *much* better due to cached analyses.
> - Sometimes worse, typically due to more / different inlining in turn
> running main pipeline (GVN + InstCombine) more times or over more code.
> - Overall somewhat a wash, but the increased compile times typically due
> to the optimizer "trying" harder, so not too concerning on our
end.
> - Again, more feedback from other users good:
`-fexperimental-new-pass-manager`
> to Clang
>
> Once the four missing things land, I'll also happily work on collecting
> some of the basics on the test-suite and CTMark. But I suspect more
"in the
> wild" data would really be useful here given the significance of the
change.
>
> Thoughts? What else (beyond the four items above and feedback on run-time
> and compile-time) would folks like to see?
>
> Once this happens, I'll also be preparing some batch, mechanical
updates
> to the test suite to primarily use the new pass manager. Also there is lots
> of documentation updates that will be needed here.
>
> -Chandler
>
> PS: I'll be sending a note to cfe-dev as a "heads up" about
this
> discussion as in some ways, the default flip is mostly a Clang default
> flip. But hopefully our doc updates will trigger this being
"perceived" as
> the default for other frontends, and I'll try to reach out to other
major
> frontends as well (Swift and Rust are on my radar, and I've already
started
> talking with Philip Reames about their Falcon JIT).
>
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
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Greg Bedwell via llvm-dev

2017-Oct-19 14:39 UTC

head link

[llvm-dev] RFC: Switching to the new pass manager by default

I looked at a few more of my earlier results in more detail. In
particular, from one of our test suites that produces some interesting
compile-time and memory usage data for clang on Windows hosts.

I did a comparison between "-O2 -g" and "-O2 -g
-fexperimental-new-pass-manager". As you'll see in the attached
graphs, in
general the suite contains some relatively small compilation units, mostly
taking <5 seconds each to compile although there are a few larger ones in
there too. I'm using 64-bit clang.exe binary targeting the PS4 triple.
I've limited the test harness to run a single process at a time.
The first graph shows all of data points. I'm plotting wall time along the
X axis and PeakWorkingSetSize (see
https://msdn.microsoft.com/en-us/library/windows/desktop/ms684877%28v=vs.85%29.aspx?f=255&MSPPError=-2147217396
) along the Y axis. As you can see there are a few interesting outliers
with the new pass manager on both axes. I'd like to do more investigation
here and possibly raise some bugs if I can make shareable reproducers.

[image: Inline images 1]

The next graph is the same data, but I've zoomed right in on the bottom
left corner to see that cluster with the greatest concentration of points
in more detail:
[image: Inline images 2]

The clusters of data points generally map quite well to each other here.
There does seem to be a visible trend that the New PM is using more
memory. There's not enough data here to extrapolate any further (remember
we're talking about <2 second compiles here), but it leaves me interested
as to what the trend would be further out; in particular when applied to
large LTO workloads where paging can become a big issue. Essentially, is
this a small, relatively constant overhead, or does it scale with overall
memory usage? I guess it's quite possible I'm seeing the effects of
different inlining strategies. This isn't necessarily a blocker either
way, but it would be an interesting question to know the answer to.

-Greg

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Davide Italiano via llvm-dev

2017-Oct-19 15:48 UTC

head link

[llvm-dev] RFC: Switching to the new pass manager by default

On Thu, Oct 19, 2017 at 4:50 AM, Greg Bedwell via llvm-dev
<llvm-dev at lists.llvm.org> wrote:> I just tried putting a relatively recent version of our merge branch
> (r316139 + our local changes) through a small subset of the PS4 testing
with
> -fexperimental-new-pass-manager enabled.  In general, most tests passed :).
> There are a few failures I'd need to look at in more detail though. 
The
> most glaring are all our tests related to generating coverage info:
>
> $ cat 1.cpp
> void foo(){}
> $ ./build/bin/clang -c -fprofile-instr-generate -fcoverage-mapping 1.cpp
> $ ./build/bin/clang -c -fprofile-instr-generate -fcoverage-mapping 1.cpp
> -fexperimental-new-pass-manager
> instrprof failed to lower an increment
> UNREACHABLE executed at
>
/home/greg/public_git/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp:5893!
>
> which I'm assuming is the same thing as was reported in
> https://bugs.llvm.org/show_bug.cgi?id=33773 .  This would definitely be a
> prerequisite for us to consider flipping the default.
>
> There are a few tests looking for specific codegen that are seeing
something
> different.  At a glance, it looks like the output from clang's -O2
looks
> roughly similar in some small examples with and without the new PM, but
> clang's -O1 is producing very different output.  Whether this is an
issue, I
> can't say for sure (I've not tried benchmarking the -O1s against
each other
> yet).  Is this expected?
>
> I've also got an example of a specific file that shows quite a large
compile
> time increase with the new PM:
>
> Old PM:
>    ---User Time---   --System Time--   --User+System--   ---Wall Time---
> --- Name ---
>   15.8125 ( 96.0%)   0.2969 ( 95.0%)  16.1094 ( 96.0%)  16.1059 ( 96.1%)
> Code Generation Time
>    0.6563 (  4.0%)   0.0156 (  5.0%)   0.6719 (  4.0%)   0.6609 (  3.9%)
> LLVM IR Generation Time
>   16.4688 (100.0%)   0.3125 (100.0%)  16.7813 (100.0%)  16.7668 (100.0%)
> Total
>
> New PM:
>    ---User Time---   --System Time--   --User+System--   ---Wall Time---
> --- Name ---
>   67.0781 ( 99.1%)   0.3438 ( 95.7%)  67.4219 ( 99.0%)  67.4543 ( 99.0%)
> Code Generation Time
>    0.6406 (  0.9%)   0.0156 (  4.3%)   0.6563 (  1.0%)   0.6644 (  1.0%)
> LLVM IR Generation Time
>   67.7188 (100.0%)   0.3594 (100.0%)  68.0781 (100.0%)  68.1187 (100.0%)
> Total
>
> It's not an example I can easily share (and also not one I'm easily
able to
> verify in its present state on a branch without our local changes to make
> sure they're not responsible somehow), but if it's of interest I
can see
> whether I can reduce it to something shareable and raise a bug.
>
> If I get a chance, I'll try putting this through some PS4 game
codebases to
> see how build time and run time performance compare there, but I'm one
of
> the few manning the fort while most of the rest of the team is out having a
> nice time at the Developers' Meeting this week, so I may not get that
chance
> for a bit.
>
FWIW, I've been running with the new PM on on several PS4 codebases
(the one I have available) for the last year or such, and I didn't see
any major compile time/runtime performance increase (or decrease,
FWIW). The set of games I have access to may be slightly different
than yours, so I suppose it's still a good thing to give it a shot,
but I wanted to throw yet another datapoint on the table.

Davide Italiano via llvm-dev

2017-Oct-19 16:01 UTC

head link

[llvm-dev] RFC: Switching to the new pass manager by default

On Tue, Oct 17, 2017 at 11:50 PM, Chandler Carruth via llvm-dev
<llvm-dev at lists.llvm.org> wrote:> Greetings everyone!
>
> The new pass manager is getting extremely close to the point where I'm
not
> aware of any significant outstanding work needed, and I'd like to see
what
> else would be needed to enable it by default. Here are the current
> functionality I'm aware of outstanding:
>
> 1) Does not do non-trivial loop unswitching. Majority of this is in
> https://reviews.llvm.org/D34200 but will need one or two small follow-ups.
>
> 2) Currently, sanitizers don't work correctly with it. Thanks to the
work of
> others, the missing infrastructure has been added and I'll send a patch
to
> wire this up this week.
>
> 3) Missing support for 'optnone'. I've been working on this,
but the
> existing testing wasn't as thorough as I wanted, so it is going slowly.
I've
> got about 1/4 of this implemented and should have patches this week or
next.
>
> 4) Missing opt-bisect (or similar) facility. This looks pretty trivial to
> add, but I've not even started. If anyone is interested in it, go for
it. We
> might even be able to do something simpler using the generic debug counters
> and get equivalent functionality.
>
I discussed this yesterday with Chandler but I'm going to echo my thoughts
here.
I think we might consider doing at least one round of fuzzing before
switching the flag (in particular, as loop unswitch has been rewritten
entirely). Zhendong has already a lot of infrastructure for this, and
it seems it's just matter of changing a flag.

For the `opt-bisect` I think we could just reuse Danny's debug counter
infrastructure (and/or port the old functionality straight to the new
PM). I don't feel particularly strong about this.

Thanks,

--
Davide

Chandler Carruth via llvm-dev

2017-Oct-19 16:18 UTC

head link

[llvm-dev] RFC: Switching to the new pass manager by default

On Thu, Oct 19, 2017 at 4:50 AM Greg Bedwell <gregbedwell at gmail.com>
wrote:
> I just tried putting a relatively recent version of our merge branch
> (r316139 + our local changes) through a small subset of the PS4 testing
> with -fexperimental-new-pass-manager enabled.  In general, most tests
> passed :).  There are a few failures I'd need to look at in more detail
> though.  The most glaring are all our tests related to generating coverage
> info:
>
> $ cat 1.cpp
> void foo(){}
> $ ./build/bin/clang -c -fprofile-instr-generate -fcoverage-mapping 1.cpp
> $ ./build/bin/clang -c -fprofile-instr-generate -fcoverage-mapping 1.cpp
> -fexperimental-new-pass-manager
> instrprof failed to lower an increment
> UNREACHABLE executed at
>
/home/greg/public_git/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp:5893!
>
> which I'm assuming is the same thing as was reported in
> https://bugs.llvm.org/show_bug.cgi?id=33773 .  This would definitely be a
> prerequisite for us to consider flipping the default.
>
Yeah, this is essentially the same issue as the sanitizers and one of the
remaining things I'm poking forward.

>
>
> There are a few tests looking for specific codegen that are seeing
> something different.  At a glance, it looks like the output from
clang's
> -O2 looks roughly similar in some small examples with and without the new
> PM, but clang's -O1 is producing very different output.  Whether this
is an
> issue, I can't say for sure (I've not tried benchmarking the -O1s
against
> each other yet).  Is this expected?
>
Yeah, I've not really closely tracked the pipeline differences between the
old PM and the new PM at O1. My best guess is that the old PM uses the
always inliner and the new PM uses a full inliner.

If the compile time of O1 is regressing a lot, its easy to try and converge
these.

> It's not an example I can easily share (and also not one I'm easily
able
> to verify in its present state on a branch without our local changes to
> make sure they're not responsible somehow), but if it's of interest
I can
> see whether I can reduce it to something shareable and raise a bug.
>
FWIW, there are some things that can increase compile time. The thing we've
seen most often is when the inliner suddenly becomes more powerful and it
generates about 2x the amount of total code. Then you see the time in the
code generator go up by 2x. That seems to match your numbers, but
definitely feel free to file a bug if this is problematic with some more
information.

>
>
> If I get a chance, I'll try putting this through some PS4 game
codebases
> to see how build time and run time performance compare there, but I'm
one
> of the few manning the fort while most of the rest of the team is out
> having a nice time at the Developers' Meeting this week, so I may not
get
> that chance for a bit.
>
> Cheers,
> -Greg
>
>
> On 18 October 2017 at 07:50, Chandler Carruth via llvm-dev <
> llvm-dev at lists.llvm.org> wrote:
>
>> Greetings everyone!
>>
>> The new pass manager is getting extremely close to the point where
I'm
>> not aware of any significant outstanding work needed, and I'd like
to see
>> what else would be needed to enable it by default. Here are the current
>> functionality I'm aware of outstanding:
>>
>> 1) Does not do non-trivial loop unswitching. Majority of this is in
>> https://reviews.llvm.org/D34200 but will need one or two small
>> follow-ups.
>>
>> 2) Currently, sanitizers don't work correctly with it. Thanks to
the work
>> of others, the missing infrastructure has been added and I'll send
a patch
>> to wire this up this week.
>>
>> 3) Missing support for 'optnone'. I've been working on
this, but the
>> existing testing wasn't as thorough as I wanted, so it is going
slowly.
>> I've got about 1/4 of this implemented and should have patches this
week or
>> next.
>>
>> 4) Missing opt-bisect (or similar) facility. This looks pretty trivial
to
>> add, but I've not even started. If anyone is interested in it, go
for it.
>> We might even be able to do something simpler using the generic debug
>> counters and get equivalent functionality.
>>
>> ... that's it?
>>
>> Optimization quality / run-time performance:
>> - We've been using it at Google extensively and are very happy with
the
>> optimization quality. Benchmarks look *very* good here.
>> - More data from other users would be important.
>> - You can try it out with `-fexperimental-new-pass-manager` to Clang
>>
>> Compile-time performance:
>> - Sometimes *much* better due to cached analyses.
>> - Sometimes worse, typically due to more / different inlining in turn
>> running main pipeline (GVN + InstCombine) more times or over more code.
>> - Overall somewhat a wash, but the increased compile times typically
due
>> to the optimizer "trying" harder, so not too concerning on
our end.
>> - Again, more feedback from other users good:
>> `-fexperimental-new-pass-manager` to Clang
>>
>> Once the four missing things land, I'll also happily work on
collecting
>> some of the basics on the test-suite and CTMark. But I suspect more
"in the
>> wild" data would really be useful here given the significance of
the change.
>>
>> Thoughts? What else (beyond the four items above and feedback on
run-time
>> and compile-time) would folks like to see?
>>
>> Once this happens, I'll also be preparing some batch, mechanical
updates
>> to the test suite to primarily use the new pass manager. Also there is
lots
>> of documentation updates that will be needed here.
>>
>> -Chandler
>>
>> PS: I'll be sending a note to cfe-dev as a "heads up"
about this
>> discussion as in some ways, the default flip is mostly a Clang default
>> flip. But hopefully our doc updates will trigger this being
"perceived" as
>> the default for other frontends, and I'll try to reach out to other
major
>> frontends as well (Swift and Rust are on my radar, and I've already
started
>> talking with Philip Reames about their Falcon JIT).
>>
>> _______________________________________________
>> LLVM Developers mailing list
>> llvm-dev at lists.llvm.org
>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>
>>
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serge guelton via llvm-dev

2017-Oct-23 09:38 UTC

head link

[llvm-dev] RFC: Switching to the new pass manager by default

On Wed, Oct 18, 2017 at 06:50:54AM +0000, Chandler Carruth via llvm-dev
wrote:> Greetings everyone!
> 
> The new pass manager is getting extremely close to the point where I'm
not
> aware of any significant outstanding work needed, and I'd like to see
what
> else would be needed to enable it by default. Here are the current
> functionality I'm aware of outstanding:
Hi Chandler,

Here at QuarksLab we're also doing an update after each release so I
cannot test without significant effort, still I'm interested in the
answer to the following question:

In our compiler, we're sometime spawning a (legacy) passmanager in a pass
(so
within an exisiting passmanager) when we want some dynamic pass
scheduling based on some analysis or user input.

Legacy passmanager forces the order between function pass and module
pass, they can't be interleaved properly, so we actually had to spawn
several PM instances one after the other to get a fine grain control over
the pass ordering.

How does the new pass manager interacts with these two use cases?

Philip Pfaffe via llvm-dev

2017-Oct-23 12:23 UTC

head link

[llvm-dev] RFC: Switching to the new pass manager by default

Hi Serge,

2017-10-23 11:38 GMT+02:00 serge guelton via llvm-dev <
llvm-dev at lists.llvm.org>:
> Hi Chandler,
>
> Here at QuarksLab we're also doing an update after each release so I
> cannot test without significant effort, still I'm interested in the
> answer to the following question:
>
> In our compiler, we're sometime spawning a (legacy) passmanager in a
pass
> (so
> within an exisiting passmanager) when we want some dynamic pass
> scheduling based on some analysis or user input.
>
The PassManager absolutely supports this. In fact, a PassManager is just a
pass, so it's kind of a first class feature. There are some limitations
however. The main one is that you may not invalidate nor run analyses of
"Outer" IRUnits. E.g. a FunctionPass can not invalidate Module
analyses or
request the results of module analyses that weren't run before. As a
consequence, running for instance a module pipeline within a function
pipeline is asking for trouble.

Legacy passmanager forces the order between function pass and
module> pass, they can't be interleaved properly, so we actually had to spawn
> several PM instances one after the other to get a fine grain control over
> the pass ordering.
>Interleaving is possible. While nesting is not fully supported (see above),
you may freely compose pipelines.  E.g. a ModulePassManager is itself a
module pass. I suggest taking a look at PassBuilder and especially its the
documentation, to get a good understanding of how pipeline setup can be
done.

Cheers,
Philip

> How does the new pass manager interacts with these two use cases?
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
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Andres Freund via llvm-dev

2017-Oct-24 10:04 UTC

head link

[llvm-dev] RFC: Switching to the new pass manager by default

Hi,

On 2017-10-18 06:50:54 +0000, Chandler Carruth via llvm-dev
wrote:> The new pass manager is getting extremely close to the point where I'm
not
> aware of any significant outstanding work needed, and I'd like to see
what
> else would be needed to enable it by default. Here are the current
> functionality I'm aware of outstanding:
> ... that's it?
I'm not sure if that qualifies as an issue, but the C API seems to
solely expose the legacy pass manager. I'm using the C API to JIT parts
of postgresql (written in C) query trees, therefore it'd be nice if the
new pass manager were also in in use via the C API.

Regards,

Andres

Evgeny Astigeevich via llvm-dev

2017-Oct-25 17:10 UTC

head link

[llvm-dev] RFC: Switching to the new pass manager by default

Hi Chandler,

I ran the LNT benchmarks and SPEC2k6.train on AArch64 Cortex-A57. I used
revisions: Clang 316561, LLVM 316563.
Options: -O3 -mcpu=cortex-a57 -fomit-frame-pointer
-fexperimental-new-pass-manager

Regressions: execution time increase

LNT
MultiSource/Benchmarks/FreeBench/fourinarow/fourinarow                          
1018.58%
MultiSource/Benchmarks/Fhourstones/fhourstones                                  
9.06%
MultiSource/Benchmarks/Ptrdist/yacr2/yacr2                                      
7.23%
MultiSource/Benchmarks/Olden/perimeter/perimeter                                
6.87%
MultiSource/Benchmarks/MiBench/consumer-typeset/consumer-typeset        6.02%
MultiSource/Benchmarks/Trimaran/enc-pc1/enc-pc1                                 
5.59%
MultiSource/Benchmarks/ASC_Sequoia/AMGmk/AMGmk                                  
5.03%

SPEC2k6
453.povray           17.11%
482.sphinx3          3.44%
444.namd             2.89%

Improvements: execution time decrease

LNT
MultiSource/Benchmarks/BitBench/uudecode/uudecode                      -50.90%
SingleSource/Benchmarks/Adobe-C++/loop_unroll                                  
-27.75%
SingleSource/Benchmarks/Misc/perlin                                             
-21.35%
MultiSource/Benchmarks/Olden/em3d/em3d                                          
-19.12%
MultiSource/Benchmarks/tramp3d-v4/tramp3d-v4                                
-8.58%
SingleSource/Benchmarks/McGill/chomp                                            
-6.33%
MultiSource/Benchmarks/sim/sim                                                  
-5.41%
MultiSource/Applications/ClamAV/clamscan                                        
-3.11%
MultiSource/Benchmarks/TSVC/Symbolics-dbl/Symbolics-dbl                 -2.81%

SPEC2k6
429.mcf                 -5.18%
473.astar              -2.65%
400.perlbench     -1.90%

There are also code sizes increases/decreases. The maximum increase is 18.98%.
The maximum decrease is 25.65%.

Thanks,
Evgeny Astigeevich

From: llvm-dev <llvm-dev-bounces at lists.llvm.org> on behalf of Chandler
Carruth via llvm-dev <llvm-dev at lists.llvm.org>
Reply-To: Chandler Carruth <chandlerc at gmail.com>
Date: Wednesday, 18 October 2017 at 07:51
To: llvm-dev <llvm-dev at lists.llvm.org>
Subject: [llvm-dev] RFC: Switching to the new pass manager by default

Greetings everyone!

The new pass manager is getting extremely close to the point where I'm not
aware of any significant outstanding work needed, and I'd like to see what
else would be needed to enable it by default. Here are the current functionality
I'm aware of outstanding:

1) Does not do non-trivial loop unswitching. Majority of this is in
https://reviews.llvm.org/D34200 but will need one or two small follow-ups.

2) Currently, sanitizers don't work correctly with it. Thanks to the work of
others, the missing infrastructure has been added and I'll send a patch to
wire this up this week.

3) Missing support for 'optnone'. I've been working on this, but the
existing testing wasn't as thorough as I wanted, so it is going slowly.
I've got about 1/4 of this implemented and should have patches this week or
next.

4) Missing opt-bisect (or similar) facility. This looks pretty trivial to add,
but I've not even started. If anyone is interested in it, go for it. We
might even be able to do something simpler using the generic debug counters and
get equivalent functionality.

... that's it?

Optimization quality / run-time performance:
- We've been using it at Google extensively and are very happy with the
optimization quality. Benchmarks look *very* good here.
- More data from other users would be important.
- You can try it out with `-fexperimental-new-pass-manager` to Clang

Compile-time performance:
- Sometimes *much* better due to cached analyses.
- Sometimes worse, typically due to more / different inlining in turn running
main pipeline (GVN + InstCombine) more times or over more code.
- Overall somewhat a wash, but the increased compile times typically due to the
optimizer "trying" harder, so not too concerning on our end.
- Again, more feedback from other users good: `-fexperimental-new-pass-manager`
to Clang

Once the four missing things land, I'll also happily work on collecting some
of the basics on the test-suite and CTMark. But I suspect more "in the
wild" data would really be useful here given the significance of the
change.

Thoughts? What else (beyond the four items above and feedback on run-time and
compile-time) would folks like to see?

Once this happens, I'll also be preparing some batch, mechanical updates to
the test suite to primarily use the new pass manager. Also there is lots of
documentation updates that will be needed here.

-Chandler

PS: I'll be sending a note to cfe-dev as a "heads up" about this
discussion as in some ways, the default flip is mostly a Clang default flip. But
hopefully our doc updates will trigger this being "perceived" as the
default for other frontends, and I'll try to reach out to other major
frontends as well (Swift and Rust are on my radar, and I've already started
talking with Philip Reames about their Falcon JIT).
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Hal Finkel via llvm-dev

2017-Oct-25 17:14 UTC

head link

[llvm-dev] RFC: Switching to the new pass manager by default

On 10/25/2017 12:10 PM, Evgeny Astigeevich via llvm-dev
wrote:>
> Hi Chandler,
>
> I ran the LNT benchmarks and SPEC2k6.train on AArch64 Cortex-A57. I 
> used revisions: Clang 316561, LLVM 316563.
>
> Options: -O3 -mcpu=cortex-a57 -fomit-frame-pointer 
> -fexperimental-new-pass-manager
>
> Regressions: execution time increase
>
> LNT
>
> MultiSource/Benchmarks/FreeBench/fourinarow/fourinarow 1018.58%
>
How real is this?

  -Hal
> MultiSource/Benchmarks/Fhourstones/fhourstones 
>                                 9.06%
>
> MultiSource/Benchmarks/Ptrdist/yacr2/yacr2 
>                                 7.23%
>
> MultiSource/Benchmarks/Olden/perimeter/perimeter 
>                                 6.87%
>
> MultiSource/Benchmarks/MiBench/consumer-typeset/consumer-typeset 6.02%
>
> MultiSource/Benchmarks/Trimaran/enc-pc1/enc-pc1 
>                                 5.59%
>
> MultiSource/Benchmarks/ASC_Sequoia/AMGmk/AMGmk                 
>                 5.03%
>
> SPEC2k6
>
> 453.povray 17.11%
>
> 482.sphinx3 3.44%
>
> 444.namd 2.89%
>
> Improvements: execution time decrease
>
> LNT
>
> MultiSource/Benchmarks/BitBench/uudecode/uudecode                 -50.90%
>
> SingleSource/Benchmarks/Adobe-C++/loop_unroll 
>                                 -27.75%
>
> SingleSource/Benchmarks/Misc/perlin 
>                                                 -21.35%
>
> MultiSource/Benchmarks/Olden/em3d/em3d                                 
> -19.12%
>
> MultiSource/Benchmarks/tramp3d-v4/tramp3d-v4 
>                                 -8.58%
>
> SingleSource/Benchmarks/McGill/chomp 
>                                                 -6.33%
>
> MultiSource/Benchmarks/sim/sim 
>                                                                 -5.41%
>
> MultiSource/Applications/ClamAV/clamscan 
>                                 -3.11%
>
> MultiSource/Benchmarks/TSVC/Symbolics-dbl/Symbolics-dbl 
>                 -2.81%
>
> SPEC2k6
>
> 429.mcf -5.18%
>
> 473.astar -2.65%
>
> 400.perlbench -1.90%
>
> There are also code sizes increases/decreases. The maximum increase is 
> 18.98%. The maximum decrease is 25.65%.
>
> Thanks,
>
> Evgeny Astigeevich
>
> *From: *llvm-dev <llvm-dev-bounces at lists.llvm.org> on behalf of 
> Chandler Carruth via llvm-dev <llvm-dev at lists.llvm.org>
> *Reply-To: *Chandler Carruth <chandlerc at gmail.com>
> *Date: *Wednesday, 18 October 2017 at 07:51
> *To: *llvm-dev <llvm-dev at lists.llvm.org>
> *Subject: *[llvm-dev] RFC: Switching to the new pass manager by default
>
> Greetings everyone!
>
> The new pass manager is getting extremely close to the point where I'm 
> not aware of any significant outstanding work needed, and I'd like to 
> see what else would be needed to enable it by default. Here are the 
> current functionality I'm aware of outstanding:
>
> 1) Does not do non-trivial loop unswitching. Majority of this is in 
> https://reviews.llvm.org/D34200 but will need one or two small follow-ups.
>
> 2) Currently, sanitizers don't work correctly with it. Thanks to the 
> work of others, the missing infrastructure has been added and I'll 
> send a patch to wire this up this week.
>
> 3) Missing support for 'optnone'. I've been working on this,
but the
> existing testing wasn't as thorough as I wanted, so it is going 
> slowly. I've got about 1/4 of this implemented and should have patches 
> this week or next.
>
> 4) Missing opt-bisect (or similar) facility. This looks pretty trivial 
> to add, but I've not even started. If anyone is interested in it, go 
> for it. We might even be able to do something simpler using the 
> generic debug counters and get equivalent functionality.
>
> ... that's it?
>
> Optimization quality / run-time performance:
>
> - We've been using it at Google extensively and are very happy with 
> the optimization quality. Benchmarks look *very* good here.
>
> - More data from other users would be important.
>
> - You can try it out with `-fexperimental-new-pass-manager` to Clang
>
> Compile-time performance:
>
> - Sometimes *much* better due to cached analyses.
>
> - Sometimes worse, typically due to more / different inlining in turn 
> running main pipeline (GVN + InstCombine) more times or over more code.
>
> - Overall somewhat a wash, but the increased compile times typically 
> due to the optimizer "trying" harder, so not too concerning on
our end.
>
> - Again, more feedback from other users good: 
> `-fexperimental-new-pass-manager` to Clang
>
> Once the four missing things land, I'll also happily work on 
> collecting some of the basics on the test-suite and CTMark. But I 
> suspect more "in the wild" data would really be useful here given
the
> significance of the change.
>
> Thoughts? What else (beyond the four items above and feedback on 
> run-time and compile-time) would folks like to see?
>
> Once this happens, I'll also be preparing some batch, mechanical 
> updates to the test suite to primarily use the new pass manager. Also 
> there is lots of documentation updates that will be needed here.
>
> -Chandler
>
> PS: I'll be sending a note to cfe-dev as a "heads up" about
this
> discussion as in some ways, the default flip is mostly a Clang default 
> flip. But hopefully our doc updates will trigger this being 
> "perceived" as the default for other frontends, and I'll try
to reach
> out to other major frontends as well (Swift and Rust are on my radar, 
> and I've already started talking with Philip Reames about their Falcon 
> JIT).
>
>
>
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
-- 
Hal Finkel
Lead, Compiler Technology and Programming Languages
Leadership Computing Facility
Argonne National Laboratory

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Xinliang David Li via llvm-dev

2017-Oct-25 17:16 UTC

head link

[llvm-dev] RFC: Switching to the new pass manager by default

On Tue, Oct 17, 2017 at 11:50 PM, Chandler Carruth via llvm-dev <
llvm-dev at lists.llvm.org> wrote:
> Greetings everyone!
>
> The new pass manager is getting extremely close to the point where I'm
not
> aware of any significant outstanding work needed, and I'd like to see
what
> else would be needed to enable it by default. Here are the current
> functionality I'm aware of outstanding:
>
> 1) Does not do non-trivial loop unswitching. Majority of this is in
> https://reviews.llvm.org/D34200 but will need one or two small follow-ups.
>
> 2) Currently, sanitizers don't work correctly with it. Thanks to the
work
> of others, the missing infrastructure has been added and I'll send a
patch
> to wire this up this week.
>
> 3) Missing support for 'optnone'. I've been working on this,
but the
> existing testing wasn't as thorough as I wanted, so it is going slowly.
> I've got about 1/4 of this implemented and should have patches this
week or
> next.
>
> 4) Missing opt-bisect (or similar) facility. This looks pretty trivial to
> add, but I've not even started. If anyone is interested in it, go for
it.
> We might even be able to do something simpler using the generic debug
> counters and get equivalent functionality.
>
> ... that's it?
>

Missing support of 'print-after-all' or 'print-after-passX'  is
another
major usability loss.

Regarding the default switch, maybe do it in two steps:

1) Switch the default for PGO build first
2) Switch the default for all modes.

David



>
> Optimization quality / run-time performance:
> - We've been using it at Google extensively and are very happy with the
> optimization quality. Benchmarks look *very* good here.
> - More data from other users would be important.
> - You can try it out with `-fexperimental-new-pass-manager` to Clang
>
> Compile-time performance:
> - Sometimes *much* better due to cached analyses.
> - Sometimes worse, typically due to more / different inlining in turn
> running main pipeline (GVN + InstCombine) more times or over more code.
> - Overall somewhat a wash, but the increased compile times typically due
> to the optimizer "trying" harder, so not too concerning on our
end.
> - Again, more feedback from other users good:
`-fexperimental-new-pass-manager`
> to Clang
>
> Once the four missing things land, I'll also happily work on collecting
> some of the basics on the test-suite and CTMark. But I suspect more
"in the
> wild" data would really be useful here given the significance of the
change.
>
> Thoughts? What else (beyond the four items above and feedback on run-time
> and compile-time) would folks like to see?
>
> Once this happens, I'll also be preparing some batch, mechanical
updates
> to the test suite to primarily use the new pass manager. Also there is lots
> of documentation updates that will be needed here.
>
> -Chandler
>
> PS: I'll be sending a note to cfe-dev as a "heads up" about
this
> discussion as in some ways, the default flip is mostly a Clang default
> flip. But hopefully our doc updates will trigger this being
"perceived" as
> the default for other frontends, and I'll try to reach out to other
major
> frontends as well (Swift and Rust are on my radar, and I've already
started
> talking with Philip Reames about their Falcon JIT).
>
> _______________________________________________
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> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
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Hal Finkel via llvm-dev

2017-Oct-25 17:19 UTC

head link

[llvm-dev] RFC: Switching to the new pass manager by default

On 10/25/2017 12:16 PM, Xinliang David Li via llvm-dev
wrote:>
>
> On Tue, Oct 17, 2017 at 11:50 PM, Chandler Carruth via llvm-dev 
> <llvm-dev at lists.llvm.org <mailto:llvm-dev at
lists.llvm.org>> wrote:
>
>     Greetings everyone!
>
>     The new pass manager is getting extremely close to the point where
>     I'm not aware of any significant outstanding work needed, and
I'd
>     like to see what else would be needed to enable it by default.
>     Here are the current functionality I'm aware of outstanding:
>
>     1) Does not do non-trivial loop unswitching. Majority of this is
>     in https://reviews.llvm.org/D34200
>     <https://reviews.llvm.org/D34200> but will need one or two small
>     follow-ups.
>
>     2) Currently, sanitizers don't work correctly with it. Thanks to
>     the work of others, the missing infrastructure has been added and
>     I'll send a patch to wire this up this week.
>
>     3) Missing support for 'optnone'. I've been working on
this, but
>     the existing testing wasn't as thorough as I wanted, so it is
>     going slowly. I've got about 1/4 of this implemented and should
>     have patches this week or next.
>
>     4) Missing opt-bisect (or similar) facility. This looks pretty
>     trivial to add, but I've not even started. If anyone is interested
>     in it, go for it. We might even be able to do something simpler
>     using the generic debug counters and get equivalent functionality.
>
>     ... that's it?
>
>
>
> Missing support of 'print-after-all' or 'print-after-passX'
is
> another major usability loss.
>
> Regarding the default switch, maybe do it in two steps:
>
> 1) Switch the default for PGO build first
> 2) Switch the default for all modes.
Why?

  -Hal
>
> David
>
>
>
>     Optimization quality / run-time performance:
>     - We've been using it at Google extensively and are very happy
>     with the optimization quality. Benchmarks look *very* good here.
>     - More data from other users would be important.
>     - You can try it out with `-fexperimental-new-pass-manager` to Clang
>
>     Compile-time performance:
>     - Sometimes *much* better due to cached analyses.
>     - Sometimes worse, typically due to more / different inlining in
>     turn running main pipeline (GVN + InstCombine) more times or over
>     more code.
>     - Overall somewhat a wash, but the increased compile times
>     typically due to the optimizer "trying" harder, so not too
>     concerning on our end.
>     - Again, more feedback from other users good:
>     `-fexperimental-new-pass-manager` to Clang
>
>     Once the four missing things land, I'll also happily work on
>     collecting some of the basics on the test-suite and CTMark. But I
>     suspect more "in the wild" data would really be useful here
given
>     the significance of the change.
>
>     Thoughts? What else (beyond the four items above and feedback on
>     run-time and compile-time) would folks like to see?
>
>     Once this happens, I'll also be preparing some batch, mechanical
>     updates to the test suite to primarily use the new pass manager.
>     Also there is lots of documentation updates that will be needed here.
>
>     -Chandler
>
>     PS: I'll be sending a note to cfe-dev as a "heads up"
about this
>     discussion as in some ways, the default flip is mostly a Clang
>     default flip. But hopefully our doc updates will trigger this
>     being "perceived" as the default for other frontends, and
I'll try
>     to reach out to other major frontends as well (Swift and Rust are
>     on my radar, and I've already started talking with Philip Reames
>     about their Falcon JIT).
>
>     _______________________________________________
>     LLVM Developers mailing list
>     llvm-dev at lists.llvm.org <mailto:llvm-dev at lists.llvm.org>
>     http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>     <http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev>
>
>
>
>
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
-- 
Hal Finkel
Lead, Compiler Technology and Programming Languages
Leadership Computing Facility
Argonne National Laboratory

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Chad Rosier via llvm-dev

2017-Oct-26 20:05 UTC

head link

[llvm-dev] RFC: Switching to the new pass manager by default

Chandler/All,

We've just started testing the new pass manager this week and we ran 
into a 548x slowdown (i.e., 6.28s to 3443.83s) for one of the files from 
SPEC2017/blender.  The issue arises only in debug builds due to the 
numerous calls to RefSCC::verify() and SCC::verify() in the 
LazyCallGraph implementation.  Would it make sense to start predicating 
these calls with the EXPENSIVE_CHECKS macro, rather than NDEBUG?

  Chad


On 10/18/2017 2:50 AM, Chandler Carruth via llvm-dev
wrote:> Greetings everyone!
>
> The new pass manager is getting extremely close to the point where I'm 
> not aware of any significant outstanding work needed, and I'd like to 
> see what else would be needed to enable it by default. Here are the 
> current functionality I'm aware of outstanding:
>
> 1) Does not do non-trivial loop unswitching. Majority of this is in 
> https://reviews.llvm.org/D34200 but will need one or two small follow-ups.
>
> 2) Currently, sanitizers don't work correctly with it. Thanks to the 
> work of others, the missing infrastructure has been added and I'll 
> send a patch to wire this up this week.
>
> 3) Missing support for 'optnone'. I've been working on this,
but the
> existing testing wasn't as thorough as I wanted, so it is going 
> slowly. I've got about 1/4 of this implemented and should have patches 
> this week or next.
>
> 4) Missing opt-bisect (or similar) facility. This looks pretty trivial 
> to add, but I've not even started. If anyone is interested in it, go 
> for it. We might even be able to do something simpler using the 
> generic debug counters and get equivalent functionality.
>
> ... that's it?
>
> Optimization quality / run-time performance:
> - We've been using it at Google extensively and are very happy with 
> the optimization quality. Benchmarks look *very* good here.
> - More data from other users would be important.
> - You can try it out with `-fexperimental-new-pass-manager` to Clang
>
> Compile-time performance:
> - Sometimes *much* better due to cached analyses.
> - Sometimes worse, typically due to more / different inlining in turn 
> running main pipeline (GVN + InstCombine) more times or over more code.
> - Overall somewhat a wash, but the increased compile times typically 
> due to the optimizer "trying" harder, so not too concerning on
our end.
> - Again, more feedback from other users good: 
> `-fexperimental-new-pass-manager` to Clang
>
> Once the four missing things land, I'll also happily work on 
> collecting some of the basics on the test-suite and CTMark. But I 
> suspect more "in the wild" data would really be useful here given
the
> significance of the change.
>
> Thoughts? What else (beyond the four items above and feedback on 
> run-time and compile-time) would folks like to see?
>
> Once this happens, I'll also be preparing some batch, mechanical 
> updates to the test suite to primarily use the new pass manager. Also 
> there is lots of documentation updates that will be needed here.
>
> -Chandler
>
> PS: I'll be sending a note to cfe-dev as a "heads up" about
this
> discussion as in some ways, the default flip is mostly a Clang default 
> flip. But hopefully our doc updates will trigger this being 
> "perceived" as the default for other frontends, and I'll try
to reach
> out to other major frontends as well (Swift and Rust are on my radar, 
> and I've already started talking with Philip Reames about their Falcon 
> JIT).
>
>
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
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Chad Rosier via llvm-dev

2017-Oct-26 20:16 UTC

head link

[llvm-dev] RFC: Switching to the new pass manager by default

Sorry, by debug build I actually meant asserts enabled.  Thus, this 
issue can show up in either a debug or release build, if asserts are 
enabled.


On 10/26/2017 4:05 PM, Chad Rosier via llvm-dev wrote:>
> Chandler/All,
>
> We've just started testing the new pass manager this week and we ran 
> into a 548x slowdown (i.e., 6.28s to 3443.83s) for one of the files 
> from SPEC2017/blender.  The issue arises only in debug builds due to 
> the numerous calls to RefSCC::verify() and SCC::verify() in the 
> LazyCallGraph implementation.  Would it make sense to start 
> predicating these calls with the EXPENSIVE_CHECKS macro, rather than 
> NDEBUG?
>
>  Chad
>
>
> On 10/18/2017 2:50 AM, Chandler Carruth via llvm-dev wrote:
>> Greetings everyone!
>>
>> The new pass manager is getting extremely close to the point where 
>> I'm not aware of any significant outstanding work needed, and
I'd
>> like to see what else would be needed to enable it by default. Here 
>> are the current functionality I'm aware of outstanding:
>>
>> 1) Does not do non-trivial loop unswitching. Majority of this is in 
>> https://reviews.llvm.org/D34200 but will need one or two small 
>> follow-ups.
>>
>> 2) Currently, sanitizers don't work correctly with it. Thanks to
the
>> work of others, the missing infrastructure has been added and I'll 
>> send a patch to wire this up this week.
>>
>> 3) Missing support for 'optnone'. I've been working on
this, but the
>> existing testing wasn't as thorough as I wanted, so it is going 
>> slowly. I've got about 1/4 of this implemented and should have 
>> patches this week or next.
>>
>> 4) Missing opt-bisect (or similar) facility. This looks pretty 
>> trivial to add, but I've not even started. If anyone is interested
in
>> it, go for it. We might even be able to do something simpler using 
>> the generic debug counters and get equivalent functionality.
>>
>> ... that's it?
>>
>> Optimization quality / run-time performance:
>> - We've been using it at Google extensively and are very happy with
>> the optimization quality. Benchmarks look *very* good here.
>> - More data from other users would be important.
>> - You can try it out with `-fexperimental-new-pass-manager` to Clang
>>
>> Compile-time performance:
>> - Sometimes *much* better due to cached analyses.
>> - Sometimes worse, typically due to more / different inlining in turn 
>> running main pipeline (GVN + InstCombine) more times or over more code.
>> - Overall somewhat a wash, but the increased compile times typically 
>> due to the optimizer "trying" harder, so not too concerning
on our end.
>> - Again, more feedback from other users good: 
>> `-fexperimental-new-pass-manager` to Clang
>>
>> Once the four missing things land, I'll also happily work on 
>> collecting some of the basics on the test-suite and CTMark. But I 
>> suspect more "in the wild" data would really be useful here
given the
>> significance of the change.
>>
>> Thoughts? What else (beyond the four items above and feedback on 
>> run-time and compile-time) would folks like to see?
>>
>> Once this happens, I'll also be preparing some batch, mechanical 
>> updates to the test suite to primarily use the new pass manager. Also 
>> there is lots of documentation updates that will be needed here.
>>
>> -Chandler
>>
>> PS: I'll be sending a note to cfe-dev as a "heads up"
about this
>> discussion as in some ways, the default flip is mostly a Clang 
>> default flip. But hopefully our doc updates will trigger this being 
>> "perceived" as the default for other frontends, and I'll
try to reach
>> out to other major frontends as well (Swift and Rust are on my radar, 
>> and I've already started talking with Philip Reames about their 
>> Falcon JIT).
>>
>>
>> _______________________________________________
>> LLVM Developers mailing list
>> llvm-dev at lists.llvm.org
>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
>
>
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
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