[PATCH] D102568: [Driver] Delete -mimplicit-it=

[Fangrui Song via Phabricator via cfe-commits]

MaskRay added a comment.

In D102568#2769389 <https://reviews.llvm.org/D102568#2769389>, @dblaikie wrote:

> In D102568#2769341 <https://reviews.llvm.org/D102568#2769341>, @MaskRay wrote:
>
>> I think libvpx's ASFLAGS usage is about GNU as, not the driver option.
>>
>> In D102568#2769296 <https://reviews.llvm.org/D102568#2769296>, @dblaikie wrote:
>>
>>>> I think "waiting for a few releases" is too much and doesn't improve things (they will notice issues until you remove the option). I can accept "waiting for one major release".
>>>
>>> Having fairly broad windows of not breaking backwards compatibility is a fairly reasonable request. Take LLVM itself, for instance - which supports building with Clang back as far as 3.5. (not suggesting we need to have a window that large for every feature/piece of surface area - but that there is scope for fairly wide windows)
>>
>> I understand the broad Windows and I also strive for this portability.
>>
>> However, reverting this patch is now a trade-off. It would make x264/openh264's mingw build happy but break musl's arm build (2018-09 ~ ).
>> There can be other projects doing detection on both -mimplicit-it and -Wa,-mimplicit-it and will be broken by reverting this patch.
>
> Not sure I follow - presumably musl's arm build wasn't working with clang before this patch? Or something changed there after this patch landed?

musl's arm build has always been working with clang. It stopped working after the driver option -mimplicit-it= was added earlier this year.
This patch dropped the driver option/fixed the musl build but broke some mingw arm projects.

> It's not OK to say "this patch fixed a bug for someone, so now reverting it is on equal footing with the regressions the patch caused" - if a patch broke an existing use case that's different from fixing a use case that wasn't working to begin with & reverting to the known/existing failures would be where things tend to lean (not absolute by any means - there are cases where we tradeoff adding a new bug to fix an existing bug) if all other things are equal.




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https://reviews.llvm.org/D102568