llvm dev - Aug 2020 - LLVM deprecation policy

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.

Tell me more abut diffing the test 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?

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?
>>

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?
> >>
>

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.

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?
>> >>
>>