[llvm-dev] [RFC] Deprecating the legacy pass manager for the optimization pipeline

[Arthur Eubanks via llvm-dev]

Are https://reviews.llvm.org/D108789 and https://reviews.llvm.org/D108775
sufficient if we cherrypick them into 13?

On Wed, Aug 25, 2021 at 11:22 AM Philip Reames <listmail at philipreames.com>
wrote:

> I'd vote for immediate removal.  I don't have much sympathy for downstream
> consumers who haven't moved.  This effort has been underway for literal
> years.  Many - though not by any means all - downstream projects moved
> *before* upstream finally switched.  Let's put a nail in this coffin, and
> remove code aggressively.
>
> Supporting both has serious ongoing costs.  As a real example, I have
> twice spent time in the last two weeks tracking down some odd quirk of the
> unrolling implementation to find it supports some quirk of the legacy pass.
> That slows down development, compromises quality, and is generally a "bad
> thing".
>
> We might want to wait a couple of weeks/months to ensure stability, but we
> should only consider the needs to the upstream project itself when doing
> so.  Giving downstream projects time to react should be an explicit
> non-goal.
>
> Philip
>
> p.s. I don't expect this to be the actual decision reached, but since I
> only see opinions down-thread arguing for migration windows, I wanted to
> make a point of sharing the opposite opinion.  Fair warning, I probably
> won't reply to this thread further.  I don't have sufficient interest in
> the topic to make it worthwhile.
> On 8/24/21 10:44 AM, Arthur Eubanks via llvm-dev wrote:
>
> The new pass manager has been on by default since the 13 branch. Now that
> we've branched for 14, I'd like to start the process of deprecating and
> removing legacy pass manager support for the optimization pipeline. This
> includes clang, opt, and lld LTO support.
>
> Note that this doesn't apply to the codegen pipeline since there's no new
> pass manager support for that yet.
>
> Are there any objections?
>
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