[llvm-dev] LLVM deprecation policy

[Nicolai Hähnle via llvm-dev]

On Fri, Aug 7, 2020 at 10:12 PM Paul C. Anagnostopoulos via llvm-dev
<llvm-dev at lists.llvm.org> wrote:
> Oh yes, I am diffing the output of some of the tests in order to be sure everything is the same. And running the tests, too.

Don't just diff the tests -- diff the .inc files that are generated as
part of the real LLVM build. Or take hashes (shaXsum or whatever)
before and after. This really isn't too difficult to do, by the way:

find $builddir -name \*.inc -exec sha256sum {} \;

Do that before and after your change, and diff it -- you really should
be seeing zero changes for a frontend-only change to TableGen like
that.

Cheers,
Nicolai


>
> I have a question about the release notes. The current version of LLVM is 10. There are release notes for 12. What happened to poor old version 11?
>
>
> At 8/7/2020 02:55 PM, David Blaikie wrote:
> >On Fri, Aug 7, 2020 at 11:47 AM Paul C. Anagnostopoulos
> ><paul at windfall.com> wrote:
> >>
> >> I think I could stomach changing the tests over time, although at least one should be left with the old punctuator. It's the "real" .td files that scare me.
> >
> >Yeah, I was mostly talking about the real .td files.
> >
> >> Tell me more abut diffing the test files.
> >
> >Oh, sorry - I was mostly talking about diffing the real output of
> >llvm-tblgen given the production .td files.
> >
> >>  I assume that the CHECK: lines are checking the important results of each .td file, and so if all the tests still pass, things are good. Are you suggesting some way of automating the comparison of the full outputs as part of the build, or just in my personal workspace?
> >
> >I mean, sure - can do the same thing for the test files I guess. But
> >yeah, I meant diffing locally as a way to validate that your changes
> >to .td files had no effect in the results.
> >
> >>
> >> At 8/7/2020 02:30 PM, David Blaikie wrote:
> >> >On Fri, Aug 7, 2020 at 11:17 AM Paul C. Anagnostopoulos
> >> ><paul at windfall.com> wrote:
> >> >>
> >> >> Oh my. You think I should patch every .td file in the system?
> >> >
> >> >Potentially, yes. If it's worth changing, important to figure out the
> >> >long-term migration strategy/technical debt of having two ways of
> >> >doing things, etc.
> >> >
> >> >If this is a pure .td feature that doesn't change the resulting output
> >> >- you could validate the change (maybe updating one .td at a time) by
> >> >diffing the output of tblgen given old/new .td syntax & show that they
> >> >produce exactly the same output.
> >> >
> >> >> That sounds a bit scary. I wrote a new test for range lists that tests the old and new range punctuator. And a release note is certainly in order. But I wasn't planning to patch all 600 .td files.
> >> >
> >> >If it's not practical to automate (with sed, etc) and would be a very
> >> >long manual process (like 10s of hours) then - yeah, probably not
> >> >worth migrating everything up-front & just leave it as-is.
> >> >
> >> >>
> >> >> At 8/7/2020 01:56 PM, David Blaikie wrote:
> >> >> >Fine by me to say the old thing's deprecated.
> >> >> >
> >> >> >Ideally, if it's not too painful - would be good if you could do a
> >> >> >complete migration to the new thing & remove the old thing, to help
> >> >> >keep things streamlined. (over multiple patches, with some
> >> >> >notification to llvm-dev and in release notes about the old thing
> >> >> >being deprecated and encouraging folks to move to the new thing ahead
> >> >> >of the removal of the old thing)
> >> >> >
> >> >> >On Fri, Aug 7, 2020 at 9:47 AM Paul C. Anagnostopoulos via llvm-dev
> >> >> ><llvm-dev at lists.llvm.org> wrote:
> >> >> >>
> >> >> >> I checked the Developer Policy and Coding Standards but couldn't find anything about deprecation. If I were to replace a simple bit of syntax in TableGen, what would I say in the documentation? Was the old syntax "deprecated"; or the new syntax "preferred"; or the old syntax simply not documented?
> >> >>
> >>
>
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