llvm dev - Jul 2019 - RFC: changing variable naming rules in LLVM codebase

Good point, too. I believe I can find lines starting with `@parameter` and
apply the same name conversion rules to identifiers after `@parameter`.
Since lld doesn't use doxygen comments, it is fine for now, but before
moving forward, I'll address that. Thank you for pointing that out.

On Wed, Jul 10, 2019 at 8:20 PM Alex Brachet-Mialot <
alexbrachetmialot at gmail.com> wrote:
> Also, now that I think about it, I believe doxygen will fail to build if
> the @parameter comments aren't changed to match the new names, my guess
is
> it case sensitive. So perhaps we will need to find a way to manually change
> these names for doxygen comments?
>
> On Wed, Jul 10, 2019 at 7:12 AM 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 at 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
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> _______________________________________________
>>>>>>> LLVM Developers mailing list
>>>>>>> llvm-dev at lists.llvm.org
>>>>>>>
https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>>>>>>
>>>>>>>
>>>>> _______________________________________________
>>>> LLVM Developers mailing list
>>>> llvm-dev at lists.llvm.org
>>>> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>>>
>>>> _______________________________________________
>>> LLVM Developers mailing list
>>> llvm-dev at lists.llvm.org
>>> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>>
>>
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So, I submitted a few patches to rename all variables in lld. If you are
interested in how it looks like, pick up any .cpp or .h file from
https://github.com/llvm/llvm-project/tree/master/lld.

I learned a few things by doing this which will help me do the same thing
to other LLVM (sub-)projects.

 - Overall a batch tool to rename variables worked reasonably well, so the
coding style change is doable.

 - There were a few classes that have a member variable Foo and a function
foo(), which would conflict after renaming. I rename variables manually
before renaming them. That's not a scalable solution, though. For a larger
codebase, I'd probably need to automate it by, for example, renaming foo()
to getFoo() if there's Foo variable already.

 - There were a few variables that would become a reserved word such as
`new` or `private` after renaming. I renamed them manually before
mass-renaming. For scalability, it probably have to be automated by
appending `_` at the end, for example.

 - My clang-based tool didn't work for #ifdef'ed-out code, which caused
unexpected failures on buildbots after submitting. I don't know how to fix
the tool so that the tool can handle code containing #ifdefs, but at least
we need to keep it in mind so that we can check it manually.

 - LLVM's `/*foo=*/`-style comment to annotate function arguments need to
be handled automatically to make the tool scalable. So is the
doxygen @parameter.

 - Since a variable rename change virtually touches every line of codebase,
that would cause massive merge conflicts to downstream repos if we don't do
anything to support them. We need to provide a tool and guidance as to how
to apply the tool to a out-of-tree repo so that a renaming change is merged
smoothly.

On Wed, Jul 10, 2019 at 8:24 PM Rui Ueyama <ruiu at google.com> wrote:
> Good point, too. I believe I can find lines starting with `@parameter` and
> apply the same name conversion rules to identifiers after `@parameter`.
> Since lld doesn't use doxygen comments, it is fine for now, but before
> moving forward, I'll address that. Thank you for pointing that out.
>
> On Wed, Jul 10, 2019 at 8:20 PM Alex Brachet-Mialot <
> alexbrachetmialot at gmail.com> wrote:
>
>> Also, now that I think about it, I believe doxygen will fail to build
if
>> the @parameter comments aren't changed to match the new names, my
guess is
>> it case sensitive. So perhaps we will need to find a way to manually
change
>> these names for doxygen comments?
>>
>> On Wed, Jul 10, 2019 at 7:12 AM 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 at 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
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>> _______________________________________________
>>>>>>>> LLVM Developers mailing list
>>>>>>>> llvm-dev at lists.llvm.org
>>>>>>>>
https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>>>>>>>
>>>>>>>>
>>>>>> _______________________________________________
>>>>> LLVM Developers mailing list
>>>>> llvm-dev at lists.llvm.org
>>>>> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>>>>
>>>>> _______________________________________________
>>>> LLVM Developers mailing list
>>>> llvm-dev at lists.llvm.org
>>>> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>>>
>>>
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On Fri, Jul 12, 2019 at 7:06 AM Rui Ueyama via llvm-dev
<llvm-dev at lists.llvm.org> wrote:
>  - LLVM's `/*foo=*/`-style comment to annotate function arguments need
to be handled automatically to make the tool scalable. So is the doxygen
@parameter.
There is also @p for "inline" references to parameters.

Cheers,
Nicolai

Hi Rui, all,

Yesterday I brought the variable-renaming commits in to Sony's 
downstream LLD. We have a merge-based flow rather than continually 
rebasing our patch set, but it went reasonably smoothly nevertheless.

The one snag I hit is that the tool initially missed variables mentioned 
in assert()s. I didn't put much time in to investigating this, but I 
presume it's because my compile_commands.json was build with assert()s 
disabled and so the names mentioned in the predicates were invisible to 
clang-llvm-rename. The result was that I ended up with something that 
built cleanly with NDEBUG, but not otherwise. I guess this is 
essentially the same as the #ifdef'd-out code issue you mentioned, but 
its effect is probably more widespread.

It was easily remedied by building in another configuration and 
reapplying to tool, but it's something others might want to watch out 
for.

Thanks,
Edd

On 2019-07-12 06:05, Rui Ueyama via llvm-dev wrote:
> So, I submitted a few patches to rename all variables in lld. If you
> are interested in how it looks like, pick up any .cpp or .h file from
> https://github.com/llvm/llvm-project/tree/master/lld.
> 
> I learned a few things by doing this which will help me do the same
> thing to other LLVM (sub-)projects.
> 
>  - Overall a batch tool to rename variables worked reasonably well, so
> the coding style change is doable.
> 
>  - There were a few classes that have a member variable Foo and a
> function foo(), which would conflict after renaming. I rename
> variables manually before renaming them. That's not a scalable
> solution, though. For a larger codebase, I'd probably need to automate
> it by, for example, renaming foo() to getFoo() if there's Foo variable
> already.
> 
>  - There were a few variables that would become a reserved word such
> as `new` or `private` after renaming. I renamed them manually before
> mass-renaming. For scalability, it probably have to be automated by
> appending `_` at the end, for example.
> 
>  - My clang-based tool didn't work for #ifdef'ed-out code, which
> caused unexpected failures on buildbots after submitting. I don't know
> how to fix the tool so that the tool can handle code containing
> #ifdefs, but at least we need to keep it in mind so that we can check
> it manually.
> 
>  - LLVM's `/*foo=*/`-style comment to annotate function arguments need
> to be handled automatically to make the tool scalable. So is the
> doxygen @parameter.
> 
>  - Since a variable rename change virtually touches every line of
> codebase, that would cause massive merge conflicts to downstream repos
> if we don't do anything to support them. We need to provide a tool and
> guidance as to how to apply the tool to a out-of-tree repo so that a
> renaming change is merged smoothly.
> 
> On Wed, Jul 10, 2019 at 8:24 PM Rui Ueyama <ruiu at google.com>
wrote:
> 
>> Good point, too. I believe I can find lines starting with
>> `@parameter` and apply the same name conversion rules to identifiers
>> after `@parameter`. Since lld doesn't use doxygen comments, it is
>> fine for now, but before moving forward, I'll address that. Thank
>> you for pointing that out.
>> 
>> On Wed, Jul 10, 2019 at 8:20 PM Alex Brachet-Mialot
>> <alexbrachetmialot at gmail.com> wrote:
>> 
>> Also, now that I think about it, I believe doxygen will fail to
>> build if the @parameter comments aren't changed to match the new
>> names, my guess is it case sensitive. So perhaps we will need to
>> find a way to manually change these names for doxygen comments?
>> 
>> On Wed, Jul 10, 2019 at 7:12 AM 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 [1] 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]
>> 
>> [2]
>> 
> https://public-inbox.org/git/20190515214503.77162-8-brho at google.com/T/
>> [3]
>> 
>> 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 [4] 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
>> [5], here is another [6], here is an example header [7].
>> 
>> 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 [8]
>> 
>> 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
>> [9]
>> _______________________________________________
>> LLVM Developers mailing list
>> llvm-dev at lists.llvm.org
>> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>> 
>> _______________________________________________
>> LLVM Developers mailing list
>> llvm-dev at lists.llvm.org
>> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
> 
>> _______________________________________________
>> LLVM Developers mailing list
>> llvm-dev at lists.llvm.org
>> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>  _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
> 
> 
> Links:
> ------
> [1] https://reviews.llvm.org/D64123
> [2] https://llvm.org/docs/Proposals/VariableNames.html#provisional-plan
> [3] 
> https://public-inbox.org/git/20190515214503.77162-8-brho at google.com/T/
> [4] https://github.com/tensorflow/mlir
> [5]
>
https://github.com/tensorflow/mlir/blob/master/lib/Transforms/LoopUnrollAndJam.cpp
> [6] 
> https://github.com/tensorflow/mlir/blob/master/lib/Parser/Parser.cpp
> [7] 
> https://github.com/tensorflow/mlir/blob/master/include/mlir/IR/Location.h
> [8] https://github.com/mplatings/git/releases/tag/ignore-rev
> [9]
>
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
-- 
Edd Dawson
SN Systems - Sony Interactive Entertainment
http://www.snsystems.com

Rui Ueyama via llvm-dev <llvm-dev at lists.llvm.org> writes:
>  - LLVM's `/*foo=*/`-style comment to annotate function arguments need
>  to be handled automatically to make the tool scalable. So is the
>  doxygen @parameter.
This is a bit of a side note, but in my own work I've more recently
tried to move from this style:

foo.h

int foo(int a, bool doSomething);

foo.cpp

x = foo(a, /*doSomething=*/true);
y = foo(a, /*doSomething=*/false);

to something like:

foo.h

inline constexpr DoDoSomething   = true;
inline constexpr DontDoSomething = false;

int foo(int a, bool doSomething);

foo.cpp

x = foo(a, DoDoSomething);
y = foo(a, DontDoSomething);

One doesn't need the inline variable (and thus not C++17) if one uses
macros or enums or something else less elegant.

This kind of thing is slightly more cumbersome to do if the parameter
takes a wide range of values, but the most common place I see the former
style is for Boolean arguments.  Nevertheless, the wide-ranging case can
be handled:

bar.h

inline int Threshold(int x) { return x; }

int bar(int a, int threshold);

bar.cpp

x = bar(a, Threshold(1000));
y = bar(a, Threshold(100));

With either technique the "named values" could be wrapped in their own
namespaces to avoid collisions.

I wonder if there is any appetite for doing something similar in LLVM.

                       -David