[LLVMdev] Bang Operator

[Sean Silva]

On Thu, Jul 23, 2015 at 8:25 AM, Meador Inge <meadori at gmail.com> wrote:

> On Thu, Jul 23, 2015 at 9:53 AM, Sky Flyer <skylake007 at googlemail.com>
> wrote:
>
> > Hello all,
> >
> > I don't find anything helping me understand the llvm bang operator. In
> the
> > llvm TableGen language reference, it only says:
> >
> > 'TableGen also has “bang operators” which have a wide variety of
> meanings:'
> >
> > I would be very thankful if someone can explain it to me.
> >
> > e.g. what does "!strconcat" or "!if" mean?
>
> Those are defined in the "Language Introduction":
>
>
> http://llvm.org/docs/TableGen/LangIntro.html#tablegen-values-and-expressions
>
> Not sure why we have things split into three separate pages:
>
>   * TableGen - http://llvm.org/docs/TableGen/index.html
>
>   * Introduction - http://llvm.org/docs/TableGen/LangIntro.html
>
>   * Reference - http://llvm.org/docs/TableGen/LangRef.html
>
>
index is about TableGen as a whole (i.e. what you might use it for, why you
would use it for that, etc.).
LangIntro is about how to use the language itself (irrespective of any
particular backend).
LangRef is a dry language reference (i.e. that you would look at or update
if modifying lib/TableGen).

Unless you are hacking in lib/TableGen, you should not need to be looking
at LangRef too much, except to maybe get an idea about the precise syntax
for a construct when you get a syntax error.

LangRef currently is mostly about syntax; there remains work to be done to
fully cover the semantics of the various constructs.

-- Sean Silva


> I consistently find myself lost between those pages.
>
> -- Meador
>
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