[llvm-dev] Need guidance to work on NEW PASS managers bugs

Wed May 2 12:04:33 PDT 2018

As a point of clarification, optnone is already being handled by the pass itself in the legacy implementation. The skip[IR unit] functions are provided by the pass base classes, and the attribute is checked there. This happens any time the legacy wrapper is run, no matter how it is run.

Regarding the opt-bisect design, I’m not particularly fond of the managed static either, but I do want to mention a couple of things that I don’t want to lose about the current solution. First, it is important that we continue to print out information about the passes and the IR units as they are run or skipped. Our QA team uses this information as a first step in identifying the source of failures. Second, a change was recently introduced to generalizing the opt bisect interface (as obtained through the LLVMContext) so that clients can plug in other mechanism that use other criteria for stopping compilation.

-Andy

From: Philip Pfaffe [mailto:philip.pfaffe at gmail.com]
Sent: Wednesday, May 02, 2018 3:57 AM
To: vivek pandya <vivekvpandya at gmail.com>
Cc: Kaylor, Andrew <andrew.kaylor at intel.com>; llvm-dev at lists.llvm.org
Subject: Re: [llvm-dev] Need guidance to work on NEW PASS managers bugs

Hi Vivek,

bisect and optnone are certainly low hanging fruit in terms of implementation. On the other hand they need a cleaner design than they have now. E.g., OptBisect today is a managed static, which we absolutely should get rid of. Instead, bisect functionality can be much more cleanly implemented on top of the debug counters!

While the function call for optnone doesn't strike me as similarly bad, there is another angle there. I think optnone should be handled by the passes, and not the manager. Considering running the pass outside of a manager, you'd probably expect it to respect optnone.

In summary, while easy to implement, these things need reconsidering and a solid RFC. So if you want to work on this, you should draft such a design document and post it to the list to collect comments and requests from the community.

Cheers,
Philip

2018-05-01 21:01 GMT+02:00 vivek pandya via llvm-dev <llvm-dev at lists.llvm.org<mailto:llvm-dev at lists.llvm.org>>:

On Tue, May 1, 2018 at 10:52 PM, Kaylor, Andrew <andrew.kaylor at intel.com<mailto:andrew.kaylor at intel.com>> wrote:
Hi Vivek,

Have you read the mailing list threads on this topic? I don’t believe we’re quite ready to make the switch yet. There was a discussion last October about what was left to be done. I’m sure it has been discussed since then too. Here’s a link to the start of the October discussion.

http://lists.llvm.org/pipermail/llvm-dev/2017-October/118280.html
Yes I have gone through that mail chain. One thing mentioned in that was Code Generation does not use new PM so I wanted to start working in that direction.

If you’d like to get involved, one possible area you could contribute is adding optbisect/optnone support as mentioned in this bug:

https://bugs.llvm.org/show_bug.cgi?id=28316

If that looks like something you’re interested in I can offer some guidance with it.
Sure I am happy to work on it. Could you please update the bug with your thoughts on how that needs to be done?

-Vivek

Thanks,
Andy

From: llvm-dev [mailto:llvm-dev-bounces at lists.llvm.org<mailto:llvm-dev-bounces at lists.llvm.org>] On Behalf Of vivek pandya via llvm-dev
Sent: Saturday, April 28, 2018 9:23 AM
To: llvm-dev <llvm-dev at lists.llvm.org<mailto:llvm-dev at lists.llvm.org>>
Subject: [llvm-dev] Need guidance to work on NEW PASS managers bugs

Hello LLVM-Devs,

I am trying to get some starting points for working on following new pass manager related bugs:

https://bugs.llvm.org/show_bug.cgi?id=28322 [PM] Remove use of old PM in the middle-end.

https://bugs.llvm.org/show_bug.cgi?id=28323 [PM] Use new PM in production for Clang, LLD, libLTO, etc. middle-end
https://bugs.llvm.org/show_bug.cgi?id=28321 [PM] Remove use of old PM in the backend

I read related code but did not get a good starting point.
Can someone guide me through this? Can we add more details to these bugs? Or can we further divide these bugs to smaller workable items?

Any help will be appreciated.

Thanks,
Vivek

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