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

Wed May 19 11:26:21 PDT 2021

mstorsjo added a comment.

In D102568#2769053 <https://reviews.llvm.org/D102568#2769053>, @nickdesaulniers wrote:

>> But this change did break my build in these places:
>> https://code.videolan.org/videolan/x264/-/blob/b684ebe04a6f80f8207a57940a1fa00e25274f81/configure#L855
>> https://chromium.googlesource.com/webm/libvpx/+/66c1ff6850fd53bcf5c17247569bea1d700d6247/build/make/configure.sh#1012
>> https://github.com/cisco/openh264/blob/089d6c6d83ab6e5d451ef18808bb6c46faf553a2/build/platform-mingw_nt.mk#L23
>
> Thanks for the links; @MaskRay I think you should file some issues in those projects to help them move to the assembler option before we try to remove it again.

Well I already started doing that, I had made one PR, when CI tests there informed me that the new form of the option didn't work out with the version of Clang in use there (10.0 fwiw).

>>> Should be an easy fix either way (replace `-mimplicit-it=always` with `-Wa,-wmimplicit-it=always`).
>>
>> No, it's not an easy fix as no existing releases of Clang support it.
>
> Well, these projects linked above will need to implement either feature detection for the command line flag options before hard coding them, or compiler version checks.

I really think it's silly to demand multiple projects to implement detection for this option. Just let's revert this change, let both option forms coexist in a couple public stable releases, until it's acceptable to raise the minimum required tool version for those build configurations to Clang 13 (it's a quite niche configuration, but upgrading CI systems always takes some time), and then after that drop the old form (e.g. in Clang 15). Maybe we could add a deprecation warning to the one that we're going to remove in the future?

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