[llvm-dev] RFC: changing variable naming rules in LLVM codebase

Wed Jul 10 04:20:21 PDT 2019

Alex,

Thank you for pointing that out. I haven't thought that before. Maybe it is
not very easy to update a comment like that using Clang AST, but I guess
that a simple Perl-style regex (such as `/*[A-Z])(.*)=*/.\1`) would work
fine as the pattern is unique, and I don't think that there are too many
false positives. Let me try.

On Wed, Jul 10, 2019 at 8:12 PM Alex Brachet-Mialot <
alexbrachetmialot at gmail.com> wrote:

> Rui,
>
> I have created D64474 to change comments explicitly stating the parameter
> names for constants ( /*parameterName=*/<constant> ). I did this by hand to
> match the new variable names. Do you know if there would be a way to update
> these comments with a tool similar to what you used to change these names?
> Perhaps it would be much more difficult, I'm guessing clang's AST doesn't
> have a way to describe comments? It's obviously not a huge deal to have
> these changed it could be done over time.
>
> Best,
> Alex
>
> On Wed, Jul 10, 2019 at 12:18 AM Rui Ueyama via llvm-dev <
> llvm-dev at lists.llvm.org> wrote:
>
>> Hi Joan,
>>
>> On Tue, Jul 9, 2019 at 9:46 PM Joan Lluch <joan.lluch at icloud.com> wrote:
>>
>>> Hi Rui,
>>>
>>> I’m totally positive on switching to camelCase convention. In fact I
>>> have been always uncomfortable with the current naming approach.
>>>
>>> My only suggestion/concern is that we should provide a transition path
>>> not only for the trunk code in the repository, but for eventual
>>> out-of-trunk code with implementations of custom architectures. I have
>>> currently a custom backend implemented on top of LLVM 9 and therefore this
>>> change will surely break my code. I assume that developers affected by this
>>> will be able to run the converting tools to fix their own code.
>>>
>>
>> The tool that I wrote for lld's style conversion should work for
>> out-of-trunk code, so as I described in the previous email, third-party
>> code maintainer should be able to use the tool to convert the style first
>> in their repositories and then rebase in order to avoid large merge
>> conflicts.
>>
>> The tool needs to be polished to convert other subprojects such as clang,
>> but I'll keep your request in mind. I'll try my best to provide a smooth
>> transition path for out-of-trunk code for any change that I'll submit for
>> the style change.
>>
>> John
>>>
>>> On 9 Jul 2019, at 09:23, Rui Ueyama via llvm-dev <
>>> llvm-dev at lists.llvm.org> wrote:
>>>
>>> Thanks, Chris.
>>>
>>> Looks like everybody is at least mildly comfortable with my variable
>>> name renaming change, so I'll to submit that change to lld subdirectory
>>> soon. If you have any objections, please let me know. Note that this is not
>>> the end of my effort but actually the beginning of it. As Chris said, I
>>> believe we should do this to the entire LLVM codebase. I'm planning to do
>>> that directory-by-directory basis.
>>>
>>> On Tue, Jul 9, 2019 at 2:03 PM Chris Lattner <clattner at nondot.org>
>>> wrote:
>>>
>>>> This looks really great to me Rui, and I’m also pleased to see the
>>>> positive comments on the review thread.  Thank you for driving this forward!
>>>>
>>>> -Chris
>>>>
>>>>
>>>> On Jul 4, 2019, at 9:50 PM, Rui Ueyama <ruiu at google.com> wrote:
>>>>
>>>> Hi all,
>>>>
>>>> I wrote a tool <https://reviews.llvm.org/D64123> to batch-rename
>>>> variable names so that they are in camelCase, and I applied the tool to lld
>>>> subdirectory. You can see my change at https://reviews.llvm.org/D64121.
>>>> If you have any comments, please reply.
>>>>
>>>> If people are happy about this change, I can do the same thing for
>>>> other directories including LLVM itself and Clang.
>>>>
>>>> On Mon, Jun 10, 2019 at 6:34 PM Rui Ueyama <ruiu at google.com> wrote:
>>>>
>>>>> On Mon, Jun 10, 2019 at 6:27 PM Michael Platings <
>>>>> Michael.Platings at arm.com> wrote:
>>>>>
>>>>>> Hi Rui,
>>>>>>
>>>>>>
>>>>>>
>>>>>> As per the provisional plan [1] we’re still at step 1: improving git
>>>>>> blame. The status of this is that there are some fairly mature patches in
>>>>>> the Git project’s queue [2], and I’m hopeful that it will be accepted in
>>>>>> something close to its current form.
>>>>>>
>>>>>>
>>>>>>
>>>>>> But if you can get started on steps 2 & 3 i.e. making forks available
>>>>>> with the possible changes applied then that would be great. My hope is that
>>>>>> once everyone can see what the options really look like then it will be
>>>>>> easier to reach consensus.
>>>>>>
>>>>>
>>>>> Sure, I'll try to do that. I'll probably start with finding
>>>>> identifiers and typenames that will conflict after the naming scheme change
>>>>> and rename them so that they won't conflict. The number of such symbols
>>>>> would hopefully be small, and submitting such renaming changes wouldn't be
>>>>> distracting. After that, I think I can create a mechanical change to rename
>>>>> variables to see how it will look like.
>>>>>
>>>>>
>>>>>>
>>>>>> Thanks,
>>>>>>
>>>>>> -Michael
>>>>>>
>>>>>>
>>>>>>
>>>>>> [1]
>>>>>> https://llvm.org/docs/Proposals/VariableNames.html#provisional-plan
>>>>>>
>>>>>> [2]
>>>>>> https://public-inbox.org/git/20190515214503.77162-8-brho@google.com/T/
>>>>>>
>>>>>>
>>>>>>
>>>>>> *From:* Rui Ueyama <ruiu at google.com>
>>>>>> *Sent:* 07 June 2019 08:42
>>>>>> *To:* Chris Lattner <clattner at nondot.org>
>>>>>> *Cc:* Michael Platings <Michael.Platings at arm.com>;
>>>>>> llvm-dev at lists.llvm.org; nd <nd at arm.com>
>>>>>> *Subject:* Re: [llvm-dev] RFC: changing variable naming rules in
>>>>>> LLVM codebase
>>>>>>
>>>>>>
>>>>>>
>>>>>> This thread is not active for a while, but I'm still interested in
>>>>>> seeing a change.
>>>>>>
>>>>>>
>>>>>>
>>>>>> Reading through this thread, looks like we can agree that we want to
>>>>>> change the local variable naming scheme so that they start with a lowercase
>>>>>> letter. Besides that, there were discussions about lower_case, camelCase,
>>>>>> m_ prefix, and each argument seems as convincing as others. I'm not sure
>>>>>> what is the decision making process in a situation like this.
>>>>>>
>>>>>>
>>>>>>
>>>>>> I'd personally vote for changing local variables to start with a
>>>>>> lowercase letter and keep other naming conventions as-is to make it a
>>>>>> minimum change.
>>>>>>
>>>>>>
>>>>>>
>>>>>> As I stated before, I'm happy to make a change to lld to see how a
>>>>>> naming convention change will look like, but in order to do that I need to
>>>>>> get at least a rough consensus to do that. What is a way to proceed?
>>>>>>
>>>>>>
>>>>>>
>>>>>> On Sat, May 25, 2019 at 3:00 PM Chris Lattner via llvm-dev <
>>>>>> llvm-dev at lists.llvm.org> wrote:
>>>>>>
>>>>>> Hi Michael,
>>>>>>
>>>>>>
>>>>>>
>>>>>> I’m still very interested in seeing a change here.  If someone is
>>>>>> interested in seeing a codebase using the proposed camelBack convention for
>>>>>> variables names, the MLIR codebase is public
>>>>>> <https://github.com/tensorflow/mlir> and uses it.
>>>>>>
>>>>>>
>>>>>>
>>>>>> If you’re curious to see what this looks like in practice, there are
>>>>>> lots of examples in the codebase, here is an example .cpp file
>>>>>> <https://github.com/tensorflow/mlir/blob/master/lib/Transforms/LoopUnrollAndJam.cpp>
>>>>>> , here is another
>>>>>> <https://github.com/tensorflow/mlir/blob/master/lib/Parser/Parser.cpp>,
>>>>>> here is an example header
>>>>>> <https://github.com/tensorflow/mlir/blob/master/include/mlir/IR/Location.h>
>>>>>> .
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>> We are still working our way through open sourcing logistics (not all
>>>>>> the code is out yet), but we would still like to contribute at least parts
>>>>>> of this to LLVM if the project is interested.  [[This is just an FYI, not
>>>>>> itself a proposal yet - one will be coming when we’re ready.]]
>>>>>>
>>>>>>
>>>>>>
>>>>>> -Chris
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>> On May 21, 2019, at 3:01 AM, Michael Platings via llvm-dev <
>>>>>> llvm-dev at lists.llvm.org> wrote:
>>>>>>
>>>>>>
>>>>>>
>>>>>> Hi folks,
>>>>>>
>>>>>> Git is on its way to learning how to ignore commits, allowing us to
>>>>>> do variable renaming and other small refactorings without breaking git
>>>>>> blame.
>>>>>>
>>>>>> It's like git-hyper-blame [1] but significantly more powerful as it
>>>>>> uses fuzzy matching to match lines, including lines that may have been
>>>>>> split or joined.
>>>>>>
>>>>>> A preview release of Git with this new feature is at:
>>>>>> https://github.com/mplatings/git/releases/tag/ignore-rev
>>>>>>
>>>>>> Some of you have told me that you already have to spend time running
>>>>>> git blame multiple times to look past uninteresting commits so I'd love for
>>>>>> you to give this feature a try and see if it helps you. Your feedback will
>>>>>> be very valuable.
>>>>>>
>>>>>> Thanks,
>>>>>> -Michael
>>>>>>
>>>>>> [1]
>>>>>> https://commondatastorage.googleapis.com/chrome-infra-docs/flat/depot_tools/docs/html/git-hyper-blame.html
>>>>>> _______________________________________________
>>>>>> LLVM Developers mailing list
>>>>>> llvm-dev at lists.llvm.org
>>>>>> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>>>>>
>>>>>>
>>>>>>
>>>>>> _______________________________________________
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>>>>>>
>>>>>>
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