Patch 1145039.
set_exc_info(), reset_exc_info(): By exploiting the
likely (who knows?) invariant that when an exception's
`type` is NULL, its `value` and `traceback` are also NULL,
save some cycles in heavily-executed code.
This is a "a kronar saved is a kronar earned" patch: the
speedup isn't reliably measurable, but it obviously does
reduce the operation count in the normal (no exception
raised) path through PyEval_EvalFrameEx().
The tim-exc_sanity branch tries to push this harder, but
is still blowing up (at least in part due to pre-existing
subtle bugs that appear to have no other visible
consequences!).
Not a bugfix candidate.
diff --git a/Include/frameobject.h b/Include/frameobject.h
index 1e3a01e..cce598b 100644
--- a/Include/frameobject.h
+++ b/Include/frameobject.h
@@ -26,7 +26,16 @@
to the current stack top. */
PyObject **f_stacktop;
PyObject *f_trace; /* Trace function */
+
+ /* If an exception is raised in this frame, the next three are used to
+ * record the exception info (if any) originally in the thread state. See
+ * comments before set_exc_info() -- it's not obvious.
+ * Invariant: if _type is NULL, then so are _value and _traceback.
+ * Desired invariant: all three are NULL, or all three are non-NULL. That
+ * one isn't currently true, but "should be".
+ */
PyObject *f_exc_type, *f_exc_value, *f_exc_traceback;
+
PyThreadState *f_tstate;
int f_lasti; /* Last instruction if called */
/* As of 2.3 f_lineno is only valid when tracing is active (i.e. when