[clang] [CIR] Add support for normal cleanups (PR #149948)

[Henrich Lauko via cfe-commits]

================
@@ -235,46 +247,93 @@ void CIRGenFunction::LexicalScope::cleanup() {
     (void)emitReturn(*returnLoc);
   }
 
-  mlir::Block *curBlock = builder.getBlock();
-  if (isGlobalInit() && !curBlock)
-    return;
-  if (curBlock->mightHaveTerminator() && curBlock->getTerminator())
-    return;
-
-  // Get rid of any empty block at the end of the scope.
-  bool entryBlock = builder.getInsertionBlock()->isEntryBlock();
-  if (!entryBlock && curBlock->empty()) {
-    curBlock->erase();
-    if (returnBlock != nullptr && returnBlock->getUses().empty())
-      returnBlock->erase();
-    return;
-  }
-
-  // Reached the end of the scope.
-  {
+  auto insertCleanupAndLeave = [&](mlir::Block *insPt) {
     mlir::OpBuilder::InsertionGuard guard(builder);
-    builder.setInsertionPointToEnd(curBlock);
+    builder.setInsertionPointToEnd(insPt);
+
+    // If we still don't have a cleanup block, it means that `applyCleanup`
+    // below might be able to get us one.
+    mlir::Block *cleanupBlock = localScope->getCleanupBlock(builder);
+
+    // Leverage and defers to RunCleanupsScope's dtor and scope handling.
+    applyCleanup();
+
+    // If we now have one after `applyCleanup`, hook it up properly.
+    if (!cleanupBlock && localScope->getCleanupBlock(builder)) {
+      cleanupBlock = localScope->getCleanupBlock(builder);
+      builder.create<cir::BrOp>(insPt->back().getLoc(), cleanupBlock);
+      if (!cleanupBlock->mightHaveTerminator()) {
+        mlir::OpBuilder::InsertionGuard guard(builder);
+        builder.setInsertionPointToEnd(cleanupBlock);
+        builder.create<cir::YieldOp>(localScope->endLoc);
+      }
+    }
 
     if (localScope->depth == 0) {
       // Reached the end of the function.
       if (returnBlock != nullptr) {
-        if (returnBlock->getUses().empty())
+        if (returnBlock->getUses().empty()) {
           returnBlock->erase();
-        else {
+        } else {
+          // Thread return block via cleanup block.
+          if (cleanupBlock) {
+            for (mlir::BlockOperand &blockUse : returnBlock->getUses()) {
+              cir::BrOp brOp = cast<cir::BrOp>(blockUse.getOwner());
----------------
xlauko wrote:

```suggestion
              cir::BrOp brOp = mlir::cast<cir::BrOp>(blockUse.getOwner());
```

https://github.com/llvm/llvm-project/pull/149948