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, 35 insertions, 0 deletions

diff --git a/Python/ceval.c b/Python/ceval.c
index 56a3b12..e8534ec 100644
--- a/Python/ceval.c
+++ b/Python/ceval.c
@@ -775,6 +775,41 @@ handle_eval_breaker:
 
 #include "generated_cases.c.h"
 
+    /* INSTRUMENTED_LINE has to be here, rather than in bytecodes.c,
+     * because it needs to capture frame->prev_instr before it is updated,
+     * as happens in the standard instruction prologue.
+     */
+#if USE_COMPUTED_GOTOS
+        TARGET_INSTRUMENTED_LINE:
+#else
+        case INSTRUMENTED_LINE:
+#endif
+    {
+        _Py_CODEUNIT *prev = frame->prev_instr;
+        _Py_CODEUNIT *here = frame->prev_instr = next_instr;
+        _PyFrame_SetStackPointer(frame, stack_pointer);
+        int original_opcode = _Py_call_instrumentation_line(
+                tstate, frame, here, prev);
+        stack_pointer = _PyFrame_GetStackPointer(frame);
+        if (original_opcode < 0) {
+            next_instr = here+1;
+            goto error;
+        }
+        next_instr = frame->prev_instr;
+        if (next_instr != here) {
+            DISPATCH();
+        }
+        if (_PyOpcode_Caches[original_opcode]) {
+            _PyBinaryOpCache *cache = (_PyBinaryOpCache *)(next_instr+1);
+            /* Prevent the underlying instruction from specializing
+             * and overwriting the instrumentation. */
+            INCREMENT_ADAPTIVE_COUNTER(cache->counter);
+        }
+        opcode = original_opcode;
+        DISPATCH_GOTO();
+    }
+
+
 #if USE_COMPUTED_GOTOS
         _unknown_opcode:
 #else