[PATCH] D106030: [Clang] add support for error+warning fn attrs

[Nick Desaulniers via Phabricator via llvm-commits]

nickdesaulniers added a comment.

In D106030#2878897 <https://reviews.llvm.org/D106030#2878897>, @arsenm wrote:

> Adding something to the IR for the sole purpose of producing a diagnostic feels really weird. I'm not sure I see why the frontend can't see this attribute and directly warn

I interpreted this differently than @efriedma or @george.burgess.iv I think.  Rephrasing the question as:

> Do we really need to keep the diagnostic itself in the IR?

The answer is no; we can keep it strictly in the frontend, and reconstitute there; we have access to the FunctionDecl which has the attribute.  So I can rework this instead of `"user-diagnostic"="oh no"` IR Fn Attr, to be just `dontcall` (in IR) then have the frontend check the FunctionDecl for the text of the user provided diagnostic.

But if the question was more so:

> Why do we need this?

Then I think @efriedma and @george.burgess.iv provided adequate reasoning. Perhaps I can reuse some of their thoughts in the commit message / patch description?


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