[PATCHv2 2/2] gdb/python: Reuse gdb.RegisterGroup objects where possible
Andrew Burgess
andrew.burgess@embecosm.com
Tue Jul 14 17:14:31 GMT 2020
Only create one gdb.RegisterGroup Python object for each of GDB's
reggroup objects.
I could have added a field into the reggroup object to hold the Python
object pointer for each reggroup, however, as reggroups are never
deleted within GDB, and are global (not per-architecture) a simpler
solution seemed to be just to hold a single global map from reggroup
pointer to a Python object representing the reggroup. Then we can
reuse the objects out of this map.
After this commit it is possible for a user to tell that two
gdb.RegisterGroup objects are now identical when previously they were
unique, however, as both these objects are read-only I don't think
this should be a problem.
There should be no other user visible changes after this commit.
gdb/ChangeLog:
* python/py-registers.c : Add 'unordered_map' include.
(gdbpy_new_reggroup): Renamed to...
(gdbpy_get_reggroup): ...this. Update to only create register
group descriptors when needed.
(gdbpy_reggroup_iter_next): Update.
gdb/testsuite/ChangeLog:
* gdb.python/py-arch-reg-groups.exp: Additional tests.
---
gdb/ChangeLog | 8 ++++
gdb/python/py-registers.c | 41 ++++++++++++++-----
gdb/testsuite/ChangeLog | 4 ++
.../gdb.python/py-arch-reg-groups.exp | 19 +++++++++
4 files changed, 61 insertions(+), 11 deletions(-)
diff --git a/gdb/python/py-registers.c b/gdb/python/py-registers.c
index 8e22a919d87..9396498cc34 100644
--- a/gdb/python/py-registers.c
+++ b/gdb/python/py-registers.c
@@ -23,6 +23,7 @@
#include "disasm.h"
#include "reggroups.h"
#include "python-internal.h"
+#include <unordered_map>
/* Token to access per-gdbarch data related to register descriptors. */
static struct gdbarch_data *gdbpy_register_object_data = NULL;
@@ -95,18 +96,36 @@ gdbpy_register_object_data_init (struct gdbarch *gdbarch)
return (void *) vec;
}
-/* Create a new gdb.RegisterGroup object wrapping REGGROUP. */
+/* Return a gdb.RegisterGroup object wrapping REGGROUP. The register
+ group objects are cached, and the same Python object will always be
+ returned for the same REGGROUP pointer. */
-static PyObject *
-gdbpy_new_reggroup (struct reggroup *reggroup)
+static gdbpy_ref<>
+gdbpy_get_reggroup (struct reggroup *reggroup)
{
- /* Create a new object and fill in its details. */
- reggroup_object *group
- = PyObject_New (reggroup_object, ®group_object_type);
- if (group == NULL)
- return NULL;
- group->reggroup = reggroup;
- return (PyObject *) group;
+ /* Map from GDB's internal reggroup objects to the Python representation.
+ GDB's reggroups are global, and are never deleted, so using a map like
+ this is safe. */
+ static std::unordered_map<struct reggroup *,gdbpy_ref<>>
+ gdbpy_reggroup_object_map;
+
+ /* If there is not already a suitable Python object in the map then
+ create a new one, and add it to the map. */
+ if (gdbpy_reggroup_object_map[reggroup] == nullptr)
+ {
+ /* Create a new object and fill in its details. */
+ gdbpy_ref<reggroup_object> group
+ (PyObject_New (reggroup_object, ®group_object_type));
+ if (group == NULL)
+ return NULL;
+ group->reggroup = reggroup;
+ gdbpy_reggroup_object_map[reggroup]
+ = gdbpy_ref<> ((PyObject *) group.release ());
+ }
+
+ /* Fetch the Python object wrapping REGGROUP from the map, increasing
+ the reference count is handled by the gdbpy_ref class. */
+ return gdbpy_reggroup_object_map[reggroup];
}
/* Convert a gdb.RegisterGroup to a string, it just returns the name of
@@ -215,7 +234,7 @@ gdbpy_reggroup_iter_next (PyObject *self)
}
iter_obj->reggroup = next_group;
- return gdbpy_new_reggroup (iter_obj->reggroup);
+ return gdbpy_get_reggroup (iter_obj->reggroup).release ();
}
/* Return a new gdb.RegisterGroupsIterator over all the register groups in
diff --git a/gdb/testsuite/gdb.python/py-arch-reg-groups.exp b/gdb/testsuite/gdb.python/py-arch-reg-groups.exp
index ea9aa77b0fa..093de2e7390 100644
--- a/gdb/testsuite/gdb.python/py-arch-reg-groups.exp
+++ b/gdb/testsuite/gdb.python/py-arch-reg-groups.exp
@@ -85,3 +85,22 @@ for { set i 0 } { $i < [llength $groups] } { incr i } {
}
}
gdb_assert { $found_non_match == 0 } "all register groups match"
+
+# Check that we get the same register group descriptors from two
+# different iterators.
+gdb_py_test_silent_cmd \
+ "python iter1 = arch.register_groups ()" \
+ "get first all register group iterator" 0
+gdb_py_test_silent_cmd \
+ "python iter2 = arch.register_groups ()" \
+ "get second all register group iterator" 0
+gdb_py_test_silent_cmd \
+ [multi_line_input \
+ "python" \
+ "for r1, r2 in zip(iter1, iter2):" \
+ " if (r1.name != r2.name):"\
+ " raise gdb.GdbError (\"miss-matched names\")" \
+ " if (r1 != r2):" \
+ " raise gdb.GdbError (\"miss-matched objects\")" \
+ "\004" ] \
+ "check names and objects match" 1
--
2.25.4
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