[enhancement] Print the performance reference tuple while running only if defined

docs/tutorial.rst

@@ -163,6 +163,13 @@ The :ref:`logging` section article describes how logging can be configured in mo
 Once a performance test finishes, its figures of merit are printed immediately using the ``P:`` prefix.
 This can be suppressed by increasing the level at which this information is logged using the :envvar:`RFM_PERF_INFO_LEVEL` environment variable.
 
+.. note::
+
+   .. versionchanged:: 4.9
+
+      If the test sets no references, then the reference tuples are not printed in the ``P:`` line.
+
+
 .. _run-reports-and-performance-logging:
 
 Run reports and performance logging

reframe/frontend/executors/policies.py

@@ -50,7 +50,13 @@ def _print_perf(task):
     for key, info in perfvars.items():
         val, ref, lower, upper, unit, result = info
         name = key.split(':')[-1]
-        msg = f'P: {name}: {val} {unit} (r:{ref}, l:{lower}, u:{upper})'
+
+        # Build reference info string only if reference is defined
+        if ref == 0 and lower is None and upper is None:
+            msg = f'P: {name}: {val} {unit}'
+        else:
+            msg = f'P: {name}: {val} {unit} (r:{ref}, l:{lower}, u:{upper})'
+
         if result == 'xfail':
             msg = color.colorize(msg, color.MAGENTA)
         elif result == 'fail' or result == 'xpass':