[CIR] Upstream Try block with only noexcept calls (llvm#165153)

Upstream try block with only noexcept calls inside, which doesn't need
to be converted to TryCallOp

Issue llvm#154992

Author: AmrDeveloper

clang/lib/CIR/Dialect/Transforms/FlattenCFG.cpp

@@ -606,10 +606,12 @@ class CIRTryOpFlattening : public mlir::OpRewritePattern<cir::TryOp> {
     // `cir.try_call`.
     llvm::SmallVector<cir::CallOp, 4> callsToRewrite;
     tryOp.getTryRegion().walk([&](CallOp op) {
+      if (op.getNothrow())
+        return;
+
       // Only grab calls within immediate closest TryOp scope.
       if (op->getParentOfType<cir::TryOp>() != tryOp)
         return;
-      assert(!cir::MissingFeatures::opCallExceptionAttr());
       callsToRewrite.push_back(op);
     });
 

clang/test/CIR/CodeGen/try-catch.cpp

@@ -164,3 +164,33 @@ void try_catch_with_alloca() {
 // OGCG: %[[TMP_B:.*]] = load i32, ptr %[[B_ADDR]], align 4
 // OGCG: %[[RESULT:.*]] = add nsw i32 %[[TMP_A]], %[[TMP_B]]
 // OGCG: store i32 %[[RESULT]], ptr %[[C_ADDR]], align 4
+
+void function_with_noexcept() noexcept;
+
+void calling_noexcept_function_inside_try_block() {
+  try {
+    function_with_noexcept();
+  } catch (...) {
+  }
+}
+
+// CIR: cir.scope {
+// CIR:   cir.try {
+// CIR:     cir.call @_Z22function_with_noexceptv() nothrow : () -> ()
+// CIR:     cir.yield
+// CIR:   }
+// CIR: }
+
+// LLVM:   br label %[[LABEL_1:.*]]
+// LLVM: [[LABEL_1]]:
+// LLVM:   br label %[[LABEL_2:.*]]
+// LLVM: [[LABEL_2]]:
+// LLVM:   call void @_Z22function_with_noexceptv()
+// LLVM:   br label %[[LABEL_3:.*]]
+// LLVM: [[LABEL_3]]:
+// LLVM:   br label %[[LABEL_4:.*]]
+// LLVM: [[LABEL_4]]:
+// LLVM:   ret void
+
+// OGCG: call void @_Z22function_with_noexceptv()
+// OGCG: ret void