[PATCH] D154658: Optimize emission of `dynamic_cast` to final classes.

[Richard Smith - zygoloid via Phabricator via cfe-commits]

rsmith added a comment.

In D154658#4490468 <https://reviews.llvm.org/D154658#4490468>, @rjmccall wrote:

> Oh, this does matter on platforms using pointer authentication, because each vptr field is signed with a constant discriminator derived from the name of the class that introduced it.

Oh, hm. I guess you have an out-of-tree patch for that? I've switched back to passing types into `GetVTablePtr`, and stopped using that from `emitExactDynamicCast` in favor of directly loading the vtpr after the `dynamic_cast<void*>`. You would need to disable the exact `dynamic_cast` optimization when pointer authentication is enabled for vptrs, but that should be a small patch.


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https://reviews.llvm.org/D154658