[clang] [clang][CodeGen] Promote point of GRO(CWG2563) (PR #151067)

[Chuanqi Xu via cfe-commits]

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@@ -973,8 +1028,27 @@ void CodeGenFunction::EmitCoroutineBody(const CoroutineBodyStmt &S) {
     // shouldn't change the AST.
     if (PreviousRetValue)
       cast<ReturnStmt>(Ret)->setRetValue(PreviousRetValue);
-  }
 
+    if (!GroManager.DirectEmit) {
+      // Send GRO conversion to ConvBB
+      auto *ConvBB =
+          cast<llvm::BranchInst>(PreConvBB->getTerminator())->getSuccessor(0);
+      auto FromIt = ++RetBB->getFirstInsertionPt();
+      auto ToIt = RetBB->getTerminator()->getIterator();
+      ConvBB->splice(ConvBB->getFirstNonPHIIt(), RetBB, FromIt, ToIt);
+
+      // After gro conversion, destroy the coroutine if it finishes execution.
+      BasicBlock *AfterConvBB =
+          cast<llvm::BranchInst>(PreConvBB->getTerminator())->getSuccessor(1);
+      BasicBlock *CleanupBB = AfterConvBB->getSingleSuccessor();
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ChuanqiXu9 wrote:

This is not obvious. How can we know its successor is Cleanup? And please make it explicit.

https://github.com/llvm/llvm-project/pull/151067