[Coroutines] Fix PR45130

For now, when final suspend can be simplified by simplifySuspendPoint,
handleFinalSuspend is executed as well to remove last case in switch
instruction. This patch fixes it.

Differential Revision: https://reviews.llvm.org/D76345

(cherry picked from commit 032251e34d17c1cbf21e7571514bb775ed5cdf30)

1 files changed, 4 insertions, 1 deletions

diff --git a/llvm/lib/Transforms/Coroutines/CoroSplit.cpp b/llvm/lib/Transforms/Coroutines/CoroSplit.cpp
index 66cb3e74e53..1e067a45d01 100644
--- a/llvm/lib/Transforms/Coroutines/CoroSplit.cpp
+++ b/llvm/lib/Transforms/Coroutines/CoroSplit.cpp
@@ -1155,7 +1155,10 @@ static void simplifySuspendPoints(coro::Shape &Shape) {
   if (N == 0)
     return;
   while (true) {
-    if (simplifySuspendPoint(cast<CoroSuspendInst>(S[I]), Shape.CoroBegin)) {
+    auto SI = cast<CoroSuspendInst>(S[I]);
+    // Leave final.suspend to handleFinalSuspend since it is undefined behavior
+    // to resume a coroutine suspended at the final suspend point.
+    if (!SI->isFinal() && simplifySuspendPoint(SI, Shape.CoroBegin)) {
       if (--N == I)
         break;
       std::swap(S[I], S[N]);