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Thanks for your reply, and I can see that this is the only benefit of this no-op: if your move to Clang and if you still have -mtune set in your build environment, you don't get an "unknown option" error. But for me personally, silently ignoring things and
giving the impression it works is worse than a simple Makefile fix, but maybe I am wrong, which is why I checked here on the list. I was guessing that a diagnostic in this case would only be value if it's enabled by default as I'm afraid many users won't enable
it? And if you need to add a flag to get this diagnostic, you might as well get rid of -mtune?</div>
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Cheers.<br>
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<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt" color="#000000"><b>From:</b> David Blaikie <dblaikie@gmail.com><br>
<b>Sent:</b> 19 April 2020 20:58<br>
<b>To:</b> Sjoerd Meijer <Sjoerd.Meijer@arm.com><br>
<b>Cc:</b> cfe-dev@lists.llvm.org Developers <cfe-dev@lists.llvm.org><br>
<b>Subject:</b> Re: [cfe-dev] Option -mtune</font>
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<div dir="ltr">On Sun, Apr 19, 2020 at 12:55 PM Sjoerd Meijer via cfe-dev <<a href="mailto:cfe-dev@lists.llvm.org">cfe-dev@lists.llvm.org</a>> wrote:<br>
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Hello,</div>
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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:</div>
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<span> // FIXME: Handle -mtune=.<br>
</span><span> (void)Args.hasArg(options::OPT_mtune_EQ);</span></div>
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giving the false impression to users it is doing something is probably the worst of options we have
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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.<br>
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Seems quite reasonable for --help and web documentation to mention that it's a no-op/supported-for-compatibility flag.<br>
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As for adding a warning for these sort of no-op flags, maybe? Probably opt-in, though.<br>
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(we get regularly questions about this).</div>
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We could simply remove it, or if this is too radical, issue a diagnostic that this is an unsupported option? Any thoughts/preferences?</div>
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Cheers,</div>
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Sjoerd.<br>
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