Merge pull request #40 from thisac/fix/qir-load-midfunc-return

Fix QIR load mid-function return

dwave/gate/qir/loader.py

@@ -91,10 +91,16 @@ def _module_to_circuit(module: Module, circuit: Optional[Circuit] = None) -> Cir
     meas_bits = []
 
     for func in module.functions:
+        ret_set = False
         for block in func.basic_blocks:
+            # if return has been set, then ignore rest of blocks
+            if ret_set:
+                break
+
             for instr in block.instructions:
-                if instr.opcode is Opcode.RET:
+                if instr.opcode == Opcode.RET:
                     # break block on return code
+                    ret_set = True
                     break
 
                 if instr.opcode == Opcode.CALL:

releasenotes/notes/fix-qir-load-midfunc-return-b0f952734e3c6f2a.yaml

@@ -0,0 +1,3 @@
+---
+fixes:
+  - Fixes loading QIR scripts with a return mid-function.

tests/test_qir/test_load.py

@@ -225,3 +225,35 @@ def test_load_QIR_into_circuit(self):
         circuit.append(ops.Z(circuit.qubits[0]))
 
         assert [op.name for op in circuit.circuit] == ["X", "Y", "Z"]
+
+    def test_early_ret(self):
+        """Test setting a return in an earlier block."""
+        qir_string = inspect.cleandoc(
+            r"""
+            ; ModuleID = 'Citrus'
+            source_filename = "Citrus"
+
+            %Qubit = type opaque
+
+            define void @main() {
+              entry:
+              call void @__quantum__rt__initialize(i8* null)
+              call void @__quantum__qis__x__body(%Qubit* null)
+              ret void
+
+              body:                                             ; preds = %entry
+              call void @__quantum__qis__y__body(%Qubit* null)
+              ret void
+            }
+
+            declare void @__quantum__rt__initialize(i8*)
+            declare void @__quantum__qis__x__body(%Qubit*)
+            declare void @__quantum__qis__y__body(%Qubit*)
+        """
+        )
+        circuit = Circuit(2)
+
+        circuit = load_qir_string(qir_string, circuit=circuit)
+
+        assert len(circuit.circuit) == 1
+        assert [op.name for op in circuit.circuit] == ["X"]