Bug fix in HighLevelSynthesis fast-return mechanism (#14349) (#14358)

* HLS early termination bug fix

* adding test

* release notes: remove extra space

(cherry picked from commit de41d1a)

Co-authored-by: Alexander Ivrii <[email protected]>

Author: mergify[bot]

crates/accelerate/src/high_level_synthesis.rs

@@ -332,7 +332,7 @@ fn all_instructions_supported(
     data: &Bound<HighLevelSynthesisData>,
     dag: &DAGCircuit,
 ) -> PyResult<bool> {
-    let ops = dag.count_ops(py, false)?;
+    let ops = dag.count_ops(py, true)?;
     let mut op_keys = ops.keys();
 
     let borrowed_data = data.borrow();

releasenotes/notes/fix-hls-fast-return-6daff39a5eba40ce.yaml

@@ -0,0 +1,7 @@
+---
+fixes:
+  - |
+    Fixed a problem in :class:`.HighLevelSynthesis` transpiler pass that caused
+    it to erroneously terminate early on certain circuits with control flow
+    operations.
+    Fixed `#14338 <https://github.com/Qiskit/qiskit-terra/issues/14338>`__

test/python/transpiler/test_high_level_synthesis.py

@@ -732,6 +732,21 @@ def test_track_global_phase(self):
             expected_block.cx(0, 1)
             self.assertEqual(transpiled_block, expected_block)
 
+    def test_control_flow(self):
+        """Test that the pass recurses into control-flow ops."""
+        clifford_circuit = QuantumCircuit(3)
+        clifford_circuit.cx(1, 0)
+        clifford_circuit.cz(0, 2)
+        cliff = Clifford(clifford_circuit)
+
+        qc = QuantumCircuit(5, 5)
+        with qc.for_loop(range(3)):
+            qc.append(cliff, [0, 1, 4])
+
+        transpiled = HighLevelSynthesis(basis_gates=["cx", "u", "for_loop"])(qc)
+        transpiled_block = transpiled[0].operation.blocks[0]
+        self.assertNotIn("clifford", transpiled_block.count_ops())
+
 
 class TestPMHSynthesisLinearFunctionPlugin(QiskitTestCase):
     """Tests for the PMHSynthesisLinearFunction plugin for synthesizing linear functions."""