[llvm-dev] Renaming passes

[Roman Lebedev via llvm-dev]

On Thu, Jun 25, 2020 at 7:48 PM Arthur Eubanks via llvm-dev
<llvm-dev at lists.llvm.org> wrote:
>
> After talking with some NPM people, I believe the ultimate goal after NPM is enabled by default is to only support `-passes=`, and remove support for `-foo-pass`.
Hm, is there any written rationale behind such a decision?
I would have thought that -passes= is the temporary solution, not the
other way around.

> However, until NPM is enabled by default, we still want tests using opt to use the legacy PM by default.
> We could attempt to make `-passes=` work with the legacy PM and have a legacy vs new PM flag, but given the design/syntax of `-passes=` I don't think that's feasible (see llvm/include/llvm/Passes/PassBuilder.h).
> So for making sure everything works with NPM, I think we need to support `-foo-pass` in NPM to be able to run all opt tests against NPM. Then at some point after NPM is enabled by default we can attempt to migrate everything to `-passes=`.

Roman.

> On Thu, Jun 25, 2020 at 9:22 AM Hiroshi Yamauchi <yamauchi at google.com> wrote:
>>
>>
>>
>> On Wed, Jun 24, 2020 at 11:13 AM Arthur Eubanks via llvm-dev <llvm-dev at lists.llvm.org> wrote:
>>>
>>> Hi,
>>>
>>> As part of new pass manager work, I've been trying to get something like `opt -foo` working under the NPM, where `foo` is the name of a pass.
>>>
>>> In the past there's been no reason to keep the names of passes consistent between NPM and legacy PM. But now there is a reason to make them match, so that we don't have to touch every single test that uses `opt`.
>>
>>
>> What's the goal here? Does it include removing the -passes option used by the NPM?
>>
>>>
>>>
>>> There are a couple of names that don't match though, for example the "basic alias analysis" pass is named "basicaa" under the legacy PM
>>> INITIALIZE_PASS_BEGIN(BasicAAWrapperPass, "basicaa",
>>>                       "Basic Alias Analysis (stateless AA impl)", true, true)
>>> but named "basic-aa" under the NPM
>>> FUNCTION_ALIAS_ANALYSIS("basic-aa", BasicAA())
>>> . Almost all the other AA passes have a dash in them so I think it makes sense to rename "basicaa" -> "basic-aa".
>>>
>>> Is there accepted wisdom on renaming pass names? Is a pass name a stable interface? When is it ok to rename a pass? If there are 800 usages of a flag, should I rename them atomically?
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>
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