[llvm] [DSE] Defer alloca store elimination for CoroSplit (PR #133918)

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NewSigma wrote:

> Could you elaborate this? e.g, give a example to describe why it is problematic. I didn't understand it.

It seems that DSE does not recognize that the coro frame is visible to the caller. It incorrectly eliminates stores right before returning to the caller, even though these values will be used upon resumption."

> While I didn't understand the problem, my instinct reaction is, even if we want to do something like this, maybe we can only do this for special allocas, like the promise alloca.

Yes, this is a safer choice.

https://github.com/llvm/llvm-project/pull/133918