[llvm-dev] Suggestion for TableGen ranges

[Nicolai Hähnle via llvm-dev]

On Thu, Jul 30, 2020 at 7:04 PM Paul C. Anagnostopoulos via llvm-dev
<llvm-dev at lists.llvm.org> wrote:
> The is a syntax quirk in TableGen. A leading plus or minus sign on a decimal integer is considered part of the integer token. Coupled with this, the hyphen (-) is used to indicate integer ranges, as in '1-5'. But the compiler lexes '1-5' as '1' followed by '-5', so a special rule is required to treat that as a range. It is documented as follows:
>
> "The peculiar last form of RangePiece is due to the fact that the "-" is included in the TokInteger, hence 1-5 gets lexed as two consecutive TokInteger’s, with values 1 and -5, instead of "1", "-", and "5"."
>
> I propose that we add '..' as a new punctuation token and use it to indicate ranges: 1..5, -10..-5. Then we can deprecate the hyphen range construct.

I like this proposal. Feel free to ping me if you need a review.

Cheers,
Nicolai


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