[PATCH] D102812: [clang] Don't pass multiple backend options if mixing -mimplicit-it and -Wa,-mimplicit-it

[David Spickett via Phabricator via cfe-commits]

DavidSpickett added a comment.

> If case 3 would mean that -mimplicit-it= is ignored when compiling assembly files, that would indeed break existing use cases. If using the input file type to disambiguate cases when there's conflicts, then that's fine, although I'm not sure if there's need for it really.

Yes, I mis-stated that one. Let me try again.

You have both options: use the one that applies to the input type
You have 2 of one option: choose the last one
You have 2 of each option: choose the last one that applies to the input type

I think that would accommodate the C with inline asm case. I only suggest it because that's what I did in the past, I don't have specific use cases to support it.

That said we've had issues downstream with `-mcpu` and `-march` options that conflict, or should conflict, and they don't warn in any way. I would like to avoid another situation like that.

Given that using both options currently crashes clang and GCC doesn't have `-mimplicit-it` I think what you have is actually the best way to go. If the two options agree, fine, if they don't, error. Let's not make it more complicated than it has to be.


Repository:
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https://reviews.llvm.org/D102812