[PATCH] D114122: [CMake] Add new cmake option to control adding comments in GenDAGISel

Fri Nov 19 01:37:40 PST 2021

RKSimon added a comment.

In D114122#3141755 <https://reviews.llvm.org/D114122#3141755>, @craig.topper wrote:

> In D114122#3141721 <https://reviews.llvm.org/D114122#3141721>, @MaskRay wrote:
>
>> In D114122#3139717 <https://reviews.llvm.org/D114122#3139717>, @nemanjai wrote:
>>
>>> In D114122#3139130 <https://reviews.llvm.org/D114122#3139130>, @MaskRay wrote:
>>>
>>>> Add a new CMake variable similar to `LLVM_OPTIMIZED_TABLEGEN`? I think most people don't need comments even for their `!NDEBUG` builds.
>>>
>>> I always wonder about statements about what "most people need/want". From my experience, most people in my immediate surroundings actually do use debug messages from ISEL and want them to refer to something they can find in `.inc` files rather than being meaningless. Most of those same people simply don't build debug builds because those are very slow, huge, etc. while just asserts provide enough "debuggability".
>>>
>>> While having messages that refer to indices in a file that do not exist seems like simply a bad idea (i.e. why emit meaningless messages at all), I do recognize the fact that comments in these `.inc` files slow everyone's build and are only useful to back end developers.
>>>
>>> All that being said, I am not against adding a CMake variable (perhaps `LLVM_OMIT_DAGISEL_COMMENTS`) that will be set to `true` for `Release` builds and `false` for `Debug/RelWithDebInfo` builds.
>>
>> I know that you mentioned it. "most people need/want" is anecdotal and from my observation that no other backend developer has complained about it. I could have missed something, though.
>>
>> To be productive, perhaps we can tag some backend developers. @RKSimon @craig.topper @arsenm @dmgreen
>
> These days I don't find myself using the numbers in those debug message very often. If I do need the comments in the GenDAGISel.inc, I run llvm-tblgen manually to generate a copy with the comments.

I think I'm one of the few braves souls/idiots who still uses non-optimized tablegen in debug builds when I encounter problems, either approach is fine by me. Having the LLVM_OMIT_DAGISEL_COMMENTS seems 'tidier' in general though.

Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D114122/new/

https://reviews.llvm.org/D114122