llvm dev - Aug 2020 - LLVM deprecation policy

Oh my. You think I should patch every .td file in the system? 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.

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 11:17 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?
>

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?
>>