[llvm] [Coroutines] Make CoroElide actually work for (trivial) C++ coroutines (PR #92969)

[Wei Wang via llvm-commits]

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@@ -193,23 +195,51 @@ CoroIdElider::CoroIdElider(CoroIdInst *CoroId, FunctionElideInfo &FEI,
       CoroAllocs.push_back(CA);
   }
 
+  DenseMap<AllocaInst *, CoroBeginInst *> Writes;
+  for (CoroBeginInst *CB : CoroBegins) {
+    for (User *U : CB->users()) {
+      if (auto *Store = dyn_cast<StoreInst>(U)) {
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apolloww wrote:

Have we seen case of the alloca stores into another alloca?

I think we can use a worklist here to catch all the allocas that alias with the corobegin.  

https://github.com/llvm/llvm-project/pull/92969