base-stats,python: Expose FormulaInfo via PyBind11

Change-Id: If7d3e7a386e138d5f4e05bb1ec4b920d6caef836
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/39300
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Maintainer: Jason Lowe-Power <power.jg@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>

src/python/pybind11/stats.cc

@@ -67,6 +67,11 @@ cast_stat_info(const Stats::Info *info)
     } while (0)
 
     TRY_CAST(Stats::ScalarInfo);
+    /* FormulaInfo is a subclass of VectorInfo. Therefore, a cast to
+     * FormulaInfo must be attempted before a cast to VectorInfo. Otherwise
+     * instances of ForumlaInfo will be cast to VectorInfo.
+     */
+    TRY_CAST(Stats::FormulaInfo);
     TRY_CAST(Stats::VectorInfo);
     TRY_CAST(Stats::DistInfo);
 
@@ -168,6 +173,14 @@ pybind_init_stats(py::module_ &m_native)
             })
         ;
 
+    py::class_<Stats::FormulaInfo, Stats::VectorInfo,
+               std::unique_ptr<Stats::FormulaInfo, py::nodelete>>(
+                      m, "FormulaInfo")
+        .def_property_readonly("str", [](const Stats::FormulaInfo &info) {
+                return info.str();
+            })
+        ;
+
     py::class_<Stats::DistInfo, Stats::Info,
                 std::unique_ptr<Stats::DistInfo, py::nodelete>>(
                     m, "DistInfo")