readability check to convert numerical constants to std::numeric_limits

[EugeneZelenko]

Bugzilla Link	35086
Version	unspecified
OS	All
CC	@JonasToth

Extended Description

It'll be great to have readability check with will convert ~0, -1 for unsigned integer types to std::numeric_limits::max().

[JonasToth]

That one should be a fairly easy one. Could we tag this as a 'Beginner' (or how the tag was called for new contributors)?

[llvmbot]

Is this still needed/desired? Can I volunteer to look at it?

If so, any advice before I start digging in :) ? Thanks.

[EugeneZelenko]

Yes, I think it's reasonable code transformation.

You could try to reach Jonas Toth and Aaron Ballman for advises.

[JonasToth]

Hi Wesley, I wrote you a mail (with the mail from your account here).

I am happy to help out for any questions and give you some starting advice!
We can chat in IRC as well (irc.oftc.net #llvm) which is faster than mail ;)

[JonasToth]

Hi everyone,

idrissrio pinged me on IRC that he worked on this check already, but did not mention it here.
@​Wesley and @​idissrio please coordinate :)

[llvmbot]

Hi!

This issue may be a good introductory issue for people new to working on LLVM. If you would like to work on this issue, your first steps are:

1. Assign the issue to you.
2. Fix the issue locally.
3. Run the test suite locally.
   3.1) Remember that the subdirectories under test/ create fine-grained testing targets, so you can
   e.g. use make check-clang-ast to only run Clang's AST tests.
4. Create a git commit
5. Run git clang-format HEAD~1 to format your changes.
6. Submit the patch to Phabricator.
   6.1) Detailed instructions can be found here

For more instructions on how to submit a patch to LLVM, see our documentation.

If you have any further questions about this issue, don't hesitate to ask via a comment on this Github issue.

@llvm/issue-subscribers-good-first-issue

[Endilll]

@PiotrZSL can you provide some analysis and points of entry into codebase?

[PiotrZSL]

Create new check, call it readability-use-math-constants or something else.

You may base on this:
https://reviews.llvm.org/D65912 (note that this one work only floatLiteral)

Just add support for min/max int, just hardcode all those values (use integerLiteral).
You may create this as separate check just for integers, as an configuration option, or put all into same check.
If this would be different, then it could be readability-use-numeric-constants or readability-use-integer-constants

[eoan-ermine]

I'll try it