[LLVMdev] [RFC] New command line parsing/generating framework for clang and lld.

[James Molloy]

Hi Michael,

On Sat, 2012-08-11 at 17:37 +0100, Chris Lattner wrote:
> On Aug 11, 2012, at 12:03 AM, Michael Spencer <bigcheesegs at gmail.com> wrote:
>
> > On Fri, Aug 10, 2012 at 6:28 PM, Chris Lattner <clattner at apple.com> wrote:
> >>
> >> On Aug 9, 2012, at 1:26 PM, Michael Spencer <bigcheesegs at gmail.com> wrote:
> >>
> >>>> Attached is a patch that adds tools/llvm-cltest. This currently contains code
> >>>> that should be in a library and will not exist in the final version. This is a
> >>>> proof of concept for what TableGen would actually generate. It does not contain
> >>>> the actual TableGen implementation.
> >>>>
> >>>> - Michael Spencer
> >>>
> >>> ping.
> >>
> >> Are you proposing that clang switch over to this, or that this be used solely by lld?
> >>
> >> -Chris
> >
> > Both clang and lld.
>
> Ok, please chat with Daniel Dunbar and Chad Rosier about this.  They'll definitely have opinions :)
>
> -Chris
>
>

Sorry for the late response. I don't feel I'm the best person to comment
on this because of my aborted attempts and broken promises at improving
the driver, but you did add me on cc... :)

I like the general idea. But why is this idea so removed from the
current (rather heavyweight) Clang argument parsing library that it
needs a full rewrite?

I get that moving the argparse stuff out of the driver is a good idea so
other tools can use it, but does it need to be reengineered so heavily?

For example, 4/5 of your "scope" points can be handled by the current
library architecture with perhaps a few implementation additions (typo
correction, for example).

It's just transforming arguments from one tool to another that isn't
implemented.

How do transformations fit in with CompilerInvocation?

As a sidenote, I've never understood why we distinguish between joined
and separate arguments. Are there situations where is it useful to
disambiguate between them? I'm always annoyed that clang will accept
"-mcpu=X" but not "-mcpu X". It seems a pointless feature to me.

Many tools take very similar arguments. For example, GCC, Clang, As and
Ld all take the "-mcpu" option. Does this need to be specified again for
every tool? There doesn't seem to be a method of inheritance of options.

I like your transformation idea though - I had a similar idea back last
January but it was more along the lines of a compiler "pass" like
architecture than fully tablegenned. I like it.

These are my initial comments from a quick scan-read - apologies if I've
misunderstood anything significant :)

Cheers,

James

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