[clang] [llvm] [coroutine] Implement llvm.coro.await.suspend intrinsic (PR #79712)

[via llvm-commits]

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@@ -1513,6 +1580,11 @@ static void handleNoSuspendCoroutine(coro::Shape &Shape) {
 // the coroutine and if that is the case we cannot eliminate the suspend point.
 static bool hasCallsInBlockBetween(Instruction *From, Instruction *To) {
   for (Instruction *I = From; I != To; I = I->getNextNode()) {
+    // This one could resume the coroutine,
+    // but additional analysis before the check should ensure,
+    // that it can't happen
+    if (isa<CoroAwaitSuspendInst>(I))
+      continue;
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fpasserby wrote:

No, because `CoroAwaitSuspendInst` is not a proper `IntrinsicInst`, because it can be invoked. I'm not sure what else could be done about it (aside from deriving `IntrinisicInst` from `CallBase` instead of `CallInst`). Also it seems like special handling for it should be added to `InlineCost.cpp` and this intrinisic should return true in `mayLowerToFunctionCall`. Callback metadata should probabply be attached to the intrinsic, but I wasn't able to find a way to do it. 

https://github.com/llvm/llvm-project/pull/79712