[cfe-dev] Option -mtune

David Blaikie via cfe-dev cfe-dev at lists.llvm.org
Sun Apr 19 12:58:33 PDT 2020

On Sun, Apr 19, 2020 at 12:55 PM Sjoerd Meijer via cfe-dev <
cfe-dev at lists.llvm.org> wrote:

> Hello,
> Quick question what you think we should be doing with option -mtune.
> Problem is that it looks like we support it because it is documented, it
> can be supplied on the command line, but it is silently ignored:
>   // FIXME: Handle -mtune=.
>   (void)Args.hasArg(options::OPT_mtune_EQ);
> giving the false impression to users it is doing something is probably the
> worst of options we have

Not /the worst/ as such, many options are added to Clang so it's command
line compatible (in the sense that you'll get a running program that
behaves correctly) with GCC - I imagine the commit history of this feature
probably justifies the addition with that sort of reason.

Seems quite reasonable for --help and web documentation to mention that
it's a no-op/supported-for-compatibility flag.

As for adding a warning for these sort of no-op flags, maybe? Probably
opt-in, though.

> (we get regularly questions about this).
> We could simply remove it, or if this is too radical, issue a diagnostic
> that this is an unsupported option? Any thoughts/preferences?
> Cheers,
> Sjoerd.
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> cfe-dev at lists.llvm.org
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