[PATCH] D101494: [SimplifyCFG] Ignore ephemeral values when counting insts for threading

[Roman Lebedev via Phabricator via llvm-commits]

lebedev.ri added a comment.

In D101494#2726074 <https://reviews.llvm.org/D101494#2726074>, @nikic wrote:

> Unless I'm missing something, this has a cache invalidation issue and will likely lead to non-deterministic builds. Say you have a dead block with an assume, which gets added to ephemeral values. Then that block and the instructions in it are removed. Now EphValues contains dangling pointers. Then new instructions get allocated and reuse the same memory. Now EphValues claims that values are ephemeral that aren't ephemeral.

It's basically the same problem we have/had with `LoopHeaders`, yep.


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