[PATCH] D37112: [coroutines] Always place escaped allocas into the coroutine frame

[Lewis Baker via Phabricator via llvm-commits]

lewissbaker added inline comments.


================
Comment at: lib/Transforms/Coroutines/CoroFrame.cpp:889
     for (User *U : I.users())
-      if (Checker.isDefinitionAcrossSuspend(I, U)) {
+      if (Checker.isDefinitionAcrossSuspend(I, U) || allocaEscapes(&I)) {
         // We cannot spill a token.
----------------
Does this mean that passing the address of any `alloca`d memory to a function call will cause it to be spilled even if its lifetime does not extend past a suspension point?

I'm thinking of cases where we have:
```
{
  co_await something;
  {
    int x = 123;
    escapes(&x);
  }
  co_await somethingElse;
}
```

Am I correct in understanding that with the proposed logic that `x` would be spilled to the frame even thought its lifetime does not cross a suspension-point? Can we avoid that?

Should we be checking for `llvm.lifetime.start` / `llvm.lifetime.end` intrinsics and if found only considering the result of `allocaEscapes(&I)` if the lifetime start/end span contains a suspension point?



https://reviews.llvm.org/D37112