base: Add support for resolving stats within groups by name

This change adds a member function to the Group class that returns a
stat given its name. The function will go through all stats in the
group and its subgroups and will return the stat that matches the
name. For example, if g is the Group system.bigCluster.cpus then a
call to

p = g.resolveStat("ipc")

will return a pointer to the stat system.bigCluster.cpus.ipc.

Change-Id: I5af8401b38b41aee611728f6d1a595f99d22d9de
Signed-off-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/27890
Reviewed-by: Bobby R. Bruce <bbruce@ucdavis.edu>
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>
Tested-by: kokoro <noreply+kokoro@google.com>

src/base/stats/group.cc

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2019 Arm Limited
+ * Copyright (c) 2019, 2020 Arm Limited
  * All rights reserved
  *
  * The license below extends only to copyright in the software and shall
@@ -117,6 +117,38 @@ Group::addStatGroup(const char *name, Group *block)
     statGroups[name] = block;
 }
 
+const Info *
+Group::resolveStat(std::string name) const
+{
+    auto pos = name.find(".");
+    if (pos == std::string::npos) {
+        // look for the stat in this group
+        for (auto &info : stats) {
+            if (info->name == name) {
+                return info;
+            }
+        }
+    } else {
+        // look for the stat in subgroups
+        const std::string gname = name.substr(0, pos);
+        for (auto &g : statGroups) {
+            if (g.first == gname) {
+                return g.second->resolveStat(name.substr(pos + 1));
+            }
+        }
+    }
+
+    // finally look for the stat in groups that have been merged
+    for (auto &g : mergedStatGroups) {
+        auto info = g->resolveStat(name);
+        if (info) {
+            return info;
+        }
+    }
+
+    return nullptr;
+}
+
 void
 Group::mergeStatGroup(Group *block)
 {

src/base/stats/group.hh

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2019 Arm Limited
+ * Copyright (c) 2019, 2020 Arm Limited
  * All rights reserved
  *
  * The license below extends only to copyright in the software and shall
@@ -157,6 +157,22 @@ class Group
      */
     void addStatGroup(const char *name, Group *block);
 
+    /**
+     * Resolve a stat by its name within this group.
+     *
+     * This method goes through the stats in this group and sub-groups
+     * and returns a pointer to the the stat that matches the provided
+     * name. The input name has to be relative to the name of this
+     * group. For example, if this group is the SimObject
+     * system.bigCluster.cpus and we want the stat
+     * system.bigCluster.cpus.ipc, the input param should be the
+     * string "ipc".
+     *
+     * @param name Name of the desired stat
+     * @return Pointer to the stat with the provided name
+     */
+    const Info * resolveStat(std::string name) const;
+
   private:
     /**
      * Merge the contents (stats & children) of a block to this block.

src/python/pybind11/stats.cc

@@ -128,5 +128,6 @@ pybind_init_stats(py::module &m_native)
         .def("getStats", &Stats::Group::getStats)
         .def("getStatGroups", &Stats::Group::getStatGroups)
         .def("addStatGroup", &Stats::Group::addStatGroup)
+        .def("resolveStat", &Stats::Group::resolveStat)
         ;
 }