[PATCH] D119571: [funcattrs] check reachability to improve noreturn

[Reid Kleckner via Phabricator via llvm-commits]

rnk accepted this revision.
rnk added a comment.

In D119571#3320553 <https://reviews.llvm.org/D119571#3320553>, @nickdesaulniers wrote:

> In D119571#3320199 <https://reviews.llvm.org/D119571#3320199>, @rnk wrote:
>
>> Do we know which pass introduces unreachable code without cleaning it up? That seems like a missed optimization, possibly a phase ordering issue, or we could tack on a `removeUnreachableBlocks` to whichever pass is modifying the CFG in the first place.
>
> In this particular case, there is no pass introducing an unreachable; the unreachable is explicit in the source.

It sounds like the phase ordering issue is that functionattrs runs before simplifycfg, and the frontend emits unreachable basic blocks. Of course, simplifycfg also benefits from functionattrs, so it's not trivial to fix. I think this is a known issue, no need to do anything about it now.


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