[clang] [CIR] Add coroutine cleanup handling and update co_return semantics (PR #189281)

[via cfe-commits]

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@@ -110,6 +109,66 @@ struct ParamReferenceReplacerRAII {
 };
 } // namespace
 
+namespace {
+// Make sure to call coro.delete on scope exit.
+struct CallCoroDelete final : public EHScopeStack::Cleanup {
+  Stmt *deallocate;
+
+  // Emit "if (coro.free(CoroId, CoroBegin)) Deallocate;"
+
+  // Note: That deallocation will be emitted twice: once for a normal exit and
+  // once for exceptional exit. This usage is safe because Deallocate does not
+  // contain any declarations. The SubStmtBuilder::makeNewAndDeleteExpr()
+  // builds a single call to a deallocation function which is safe to emit
+  // multiple times.
+  void emit(CIRGenFunction &cgf, Flags) override {
+    // Remember the current point, as we are going to emit deallocation code
+    // first to get to coro.free instruction that is an argument to a delete
+    // call.
+
+    if (cgf.emitStmt(deallocate, /*useCurrentScope=*/true).failed()) {
+      cgf.cgm.error(deallocate->getBeginLoc(),
+                    "failed to emit coroutine deallocation expression");
+      return;
+    }
+
+    CIRGenBuilderTy &builder = cgf.getBuilder();
+    mlir::Location loc = cgf.getLoc(deallocate->getSourceRange());
+    cir::CallOp coroFree = cgf.curCoro.data->lastCoroFree;
+
+    if (!coroFree) {
+      cgf.cgm.error(deallocate->getBeginLoc(),
+                    "Deallocation expressoin does not refer to coro.free");
+      return;
+    }
+
+    builder.setInsertionPointAfter(coroFree);
+    cir::ConstantOp nullPtrCst = builder.getNullPtr(cgf.voidPtrTy, loc);
+    auto cmp = cir::CmpOp::create(builder, loc, cir::CmpOpKind::ne,
+                                  coroFree.getResult(), nullPtrCst);
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Andres-Salamanca wrote:

Done, I ended up using `createPtrIsNotNull` because we should not destroy the coroutine frame when `coro.free` returns a non-null pointer.

https://github.com/llvm/llvm-project/pull/189281