Added reboxing tests

In D146487#4209196, @luporl wrote:

Shouldn't the title of this patch be "HLFIR to FIR ..."?

Thank you for the feedback, Jean. I'll keep looking into this.

Something to note is that this patch currently doesn't support expressions like array%im + 3 because arith.fadd will complain that fir.real isn't floating-point-like. It also seems like hlfir.designate expects a fir.real designation type, so I'm not really sure how to reconcile this. I don't know if this is issue with this patch or if its a problem outside of the scope of this task, but I figured it was worth bringing up.

In D143301#4143241, @PeteSteinfeld wrote:

In D143301#4143108, @vzakhari wrote:

The new tests fail to link:

That is, these new tests cause check-flang to fail. @elmcdonough, can you please fix things so that check-flang no longer fails?

Comment edit + exhuastive testing

Clang format + documentation update

In D143301#4135301, @awarzynski wrote:

@elmcdonough , let me rephrase this (should've been clearer before, sorry):

One thing that's not clear to me - how come "-Wextra" is not treated as an error and "-Wblah" is?

Where's the logic that makes sure that -Wextra (and other flags that you redefine here) is reported as unused? That's not clear from this definition:

multiclass FlangIgnoredDiagOpt<string name> {
  def unsupported_warning_w#NAME : Flag<["-", "--"], "W"#name>, Group<flang_ignored_w_Group>;
}

In particular, I don't see anything that would check whether a particular option is in this group: flang_ignored_w_Group.

Change multiclass name for the sake of clarity.

Ping

Thanks for the feedback everyone. This is my current understanding on what I should do: I am to rename gfortran_unsupported_Group to flang_ignored_w_Group and move the non W group gfortran options into another patch. I have these changes locally and am currently building + testing. Please let me know if I'm misinterpreting these instructions.

This update adds other unsupported gfortran options to Options.td.

In D143301#4110914, @jdoerfert wrote:

Let's do (= @elmcdonough, please do) two things:

1. Fix the tests and get this in (assuming it's reasonable)
2. Start a discourse thread with the different options we discussed so far. My vote is to do what clang does. If that is not properly defined we can do categories of ignored options for other compilers and emit warnings under a common flag (-Wgfortran-only, -Wifx-only, ...).

I fixed the formatting and test.

In D143301#4109632, @awarzynski wrote:

In D143301#4109568, @jdoerfert wrote:

Squash your commits into a single one before uploading it to Phabricator. We don't do multi-commit pull requests but one commit changes that contain the entire feature (basically we don't care how we arrived at the final commit).

The test should check for the diagnosis, thus that we emit a warning when we expect it, and none otherwise.

@awarzynski other thoughts?

Thanks for sending this, @elmcdonough !

I appreciate that in your case you are only concerned with -Wextra, but what are we meant to do with other flags like this (either diagnostic or non-diagnostic option that's used in GFortran, but unavailable in LLVM Flang)? I think that we should agree to treat all unsupported GFortran options like this (for consistency) and take a bit more generic approach. I see at least a couple of options:

• Add another flag in Options.td to clearly document such options (something akin FlangOnlyOption), e.g. GFortranFlag. This way, adding a new "unsupported" option would boil down to decorating it with this new flag in Options.td,
• Create something similar to e.g. LangOptions.def to define such unsupported options.

Also, this is effectively changing the design of the driver (and the user-visible behavior). I would appreciate a note in:

• the release notes,
• driver documentation.

It's fine if you only add -Wextra for now, but I think that it would be good for the long term health of Flang if we had a clear mechanism for such flags that others can use in the future. WDYT?

Add tests for change as requested by reviewer