GH-103082: Filter LINE events in VM, to simplify tool implementation. (GH-104387)

When monitoring LINE events, instrument all instructions that can have a predecessor on a different line.
Then check that the a new line has been hit in the instrumentation code.
This brings the behavior closer to that of 3.11, simplifying implementation and porting of tools.

1 files changed, 19 insertions, 54 deletions

diff --git a/Python/legacy_tracing.c b/Python/legacy_tracing.c
index e509e63..5143b79 100644
--- a/Python/legacy_tracing.c
+++ b/Python/legacy_tracing.c
@@ -4,6 +4,7 @@
 
 #include <stddef.h>
 #include "Python.h"
+#include "opcode.h"
 #include "pycore_ceval.h"
 #include "pycore_object.h"
 #include "pycore_sysmodule.h"
@@ -213,7 +214,6 @@ trace_line(
     if (line < 0) {
         Py_RETURN_NONE;
     }
-    frame ->f_last_traced_line = line;
     Py_INCREF(frame);
     frame->f_lineno = line;
     int err = tstate->c_tracefunc(tstate->c_traceobj, frame, self->event, Py_None);
@@ -245,14 +245,12 @@ sys_trace_line_func(
         return NULL;
     }
     assert(args[0] == (PyObject *)frame->f_frame->f_code);
-    if (frame ->f_last_traced_line == line) {
-        /* Already traced this line */
-        Py_RETURN_NONE;
-    }
     return trace_line(tstate, self, frame, line);
 }
 
-
+/* sys.settrace generates line events for all backward
+ * edges, even if on the same line.
+ * Handle that case here */
 static PyObject *
 sys_trace_jump_func(
     _PyLegacyEventHandler *self, PyObject *const *args,
@@ -268,61 +266,33 @@ sys_trace_jump_func(
     assert(from >= 0);
     int to = _PyLong_AsInt(args[2])/sizeof(_Py_CODEUNIT);
     assert(to >= 0);
-    PyFrameObject *frame = PyEval_GetFrame();
-    if (frame == NULL) {
-        PyErr_SetString(PyExc_SystemError,
-                        "Missing frame when calling trace function.");
-        return NULL;
-    }
-    if (!frame->f_trace_lines) {
-        Py_RETURN_NONE;
+    if (to > from) {
+        /* Forward jump */
+        return &_PyInstrumentation_DISABLE;
     }
     PyCodeObject *code = (PyCodeObject *)args[0];
     assert(PyCode_Check(code));
-    assert(code == frame->f_frame->f_code);
     /* We can call _Py_Instrumentation_GetLine because we always set
     * line events for tracing */
     int to_line = _Py_Instrumentation_GetLine(code, to);
-    /* Backward jump: Always generate event
-     * Forward jump: Only generate event if jumping to different line. */
-    if (to > from && frame->f_last_traced_line == to_line) {
-        /* Already traced this line */
-        Py_RETURN_NONE;
+    int from_line = _Py_Instrumentation_GetLine(code, from);
+    if (to_line != from_line) {
+        /* Will be handled by target INSTRUMENTED_LINE */
+        return &_PyInstrumentation_DISABLE;
     }
-    return trace_line(tstate, self, frame, to_line);
-}
-
-/* We don't care about the exception here,
- * we just treat it as a possible new line
- */
-static PyObject *
-sys_trace_exception_handled(
-    _PyLegacyEventHandler *self, PyObject *const *args,
-    size_t nargsf, PyObject *kwnames
-) {
-    assert(kwnames == NULL);
-    PyThreadState *tstate = _PyThreadState_GET();
-    if (tstate->c_tracefunc == NULL) {
-        Py_RETURN_NONE;
-    }
-    assert(PyVectorcall_NARGS(nargsf) == 3);
     PyFrameObject *frame = PyEval_GetFrame();
-    PyCodeObject *code = (PyCodeObject *)args[0];
-    assert(PyCode_Check(code));
+    if (frame == NULL) {
+        PyErr_SetString(PyExc_SystemError,
+                        "Missing frame when calling trace function.");
+        return NULL;
+    }
     assert(code == frame->f_frame->f_code);
-    assert(PyLong_Check(args[1]));
-    int offset = _PyLong_AsInt(args[1])/sizeof(_Py_CODEUNIT);
-    /* We can call _Py_Instrumentation_GetLine because we always set
-    * line events for tracing */
-    int line = _Py_Instrumentation_GetLine(code, offset);
-    if (frame->f_last_traced_line == line) {
-        /* Already traced this line */
+    if (!frame->f_trace_lines) {
         Py_RETURN_NONE;
     }
-    return trace_line(tstate, self, frame, line);
+    return trace_line(tstate, self, frame, to_line);
 }
 
-
 PyTypeObject _PyLegacyEventHandler_Type = {
     PyVarObject_HEAD_INIT(&PyType_Type, 0)
     "sys.legacy_event_handler",
@@ -487,7 +457,7 @@ _PyEval_SetTrace(PyThreadState *tstate, Py_tracefunc func, PyObject *arg)
         }
         if (set_callbacks(PY_MONITORING_SYS_TRACE_ID,
             (vectorcallfunc)sys_trace_jump_func, PyTrace_LINE,
-                        PY_MONITORING_EVENT_JUMP, PY_MONITORING_EVENT_BRANCH)) {
+                        PY_MONITORING_EVENT_JUMP, -1)) {
             return -1;
         }
         if (set_callbacks(PY_MONITORING_SYS_TRACE_ID,
@@ -495,11 +465,6 @@ _PyEval_SetTrace(PyThreadState *tstate, Py_tracefunc func, PyObject *arg)
                         PY_MONITORING_EVENT_INSTRUCTION, -1)) {
             return -1;
         }
-        if (set_callbacks(PY_MONITORING_SYS_TRACE_ID,
-            (vectorcallfunc)sys_trace_exception_handled, PyTrace_LINE,
-                        PY_MONITORING_EVENT_EXCEPTION_HANDLED, -1)) {
-            return -1;
-        }
     }
 
     int delta = (func != NULL) - (tstate->c_tracefunc != NULL);