[llvm] [CodeGenPrepare] Make sure instruction get from SunkAddrs is before MemoryInst (PR #139303)

[Reid Kleckner via llvm-commits]

rnk wrote:

> In the second iteration of the loop, MemoryInst2 may use the same address 

This sounds like an ABA problem, like use-after-free. The use of ValueMap should prevent this, right? Is the problem really address reuse? I just want to make sure that we don't have stale entries in the ValueMap.

https://github.com/llvm/llvm-project/pull/139303