llvm dev - Aug 2021 - [RFC] Deprecating the legacy pass manager for the optimization pipeline

I probably should have said "deprecating and removing".

My intention was to remove it completely. -DLLVM_ENABLE_NEW_PASS_MANAGER
wouldn't do anything and we'd remove the
-flegacy-pass-manaager/-fexperimental-new-pass-manager flags, as well as
the corresponding lld flags.

On Tue, Aug 24, 2021 at 12:02 PM Fangrui Song <maskray at google.com>
wrote:
> On 2021-08-24, 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?
>
> "deprecating" and 'removing" are different.
>
> For 14.0.0, do you plan that -DLLVM_ENABLE_NEW_PASS_MANAGER=off will
> give a warning or will be completely unsupported?
>
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Since deprecating something is giving warning that it’s going to be removed, I
don’t think it’s fair to deprecate and remove in one step. If legacy pass
manager isn’t currently formally deprecated (as in, loudly complains when you
try to use it), then I’d personally like to see it deprecated for a release
before any steps to completely remove it are taken.

From: llvm-dev <llvm-dev-bounces at lists.llvm.org> On Behalf Of Arthur
Eubanks via llvm-dev
Sent: Tuesday, August 24, 2021 12:10 PM
To: Fangrui Song <maskray at google.com>
Cc: llvm-dev <llvm-dev at lists.llvm.org>
Subject: Re: [llvm-dev] [RFC] Deprecating the legacy pass manager for the
optimization pipeline


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I probably should have said "deprecating and removing".

My intention was to remove it completely. -DLLVM_ENABLE_NEW_PASS_MANAGER
wouldn't do anything and we'd remove the
-flegacy-pass-manaager/-fexperimental-new-pass-manager flags, as well as the
corresponding lld flags.

On Tue, Aug 24, 2021 at 12:02 PM Fangrui Song <maskray at
google.com<mailto:maskray at google.com>> wrote:
On 2021-08-24, 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?
"deprecating" and 'removing" are different.

For 14.0.0, do you plan that -DLLVM_ENABLE_NEW_PASS_MANAGER=off will
give a warning or will be completely unsupported?
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