python · Fidget-Spinner · Dec 29, 2025 · Dec 29, 2025 · Dec 29, 2025 · Dec 30, 2025
diff --git a/Include/internal/pycore_backoff.h b/Include/internal/pycore_backoff.h
@@ -135,6 +135,20 @@ initial_jump_backoff_counter(_PyOptimizationConfig *opt_config)
         opt_config->jump_backward_initial_backoff);
 }
 
+// This needs to be around 2-4x of JUMP_BACKWARD_INITIAL_VALUE
+// The reasoning is that we always want loop traces to form and inline
+// functions before functions themselves warm up and link to them instead
+// of inlining.
+#define RESUME_INITIAL_VALUE 8190
+#define RESUME_INITIAL_BACKOFF 6
+static inline _Py_BackoffCounter
+initial_resume_backoff_counter(_PyOptimizationConfig *opt_config)
+{
+    return make_backoff_counter(
+        opt_config->resume_initial_value,
+        opt_config->resume_initial_backoff);
+}
+
 /* Initial exit temperature.
  * Must be larger than ADAPTIVE_COOLDOWN_VALUE,
  * otherwise when a side exit warms up we may construct

diff --git a/Include/internal/pycore_code.h b/Include/internal/pycore_code.h
@@ -323,6 +323,7 @@ PyAPI_FUNC(void) _Py_Specialize_ToBool(_PyStackRef value, _Py_CODEUNIT *instr);
 PyAPI_FUNC(void) _Py_Specialize_ContainsOp(_PyStackRef value, _Py_CODEUNIT *instr);
 PyAPI_FUNC(void) _Py_GatherStats_GetIter(_PyStackRef iterable);
 PyAPI_FUNC(void) _Py_Specialize_CallFunctionEx(_PyStackRef func_st, _Py_CODEUNIT *instr);
+PyAPI_FUNC(void) _Py_Specialize_Resume(_Py_CODEUNIT *instr, PyThreadState *tstate);
 
 // Utility functions for reading/writing 32/64-bit values in the inline caches.
 // Great care should be taken to ensure that these functions remain correct and

diff --git a/Include/internal/pycore_interp_structs.h b/Include/internal/pycore_interp_structs.h
@@ -413,6 +413,9 @@ typedef struct _PyOptimizationConfig {
     uint16_t jump_backward_initial_value;
     uint16_t jump_backward_initial_backoff;
 
+    uint16_t resume_initial_value;
+    uint16_t resume_initial_backoff;
+
     // JIT optimization thresholds
     uint16_t side_exit_initial_value;
     uint16_t side_exit_initial_backoff;

diff --git a/Include/internal/pycore_magic_number.h b/Include/internal/pycore_magic_number.h
@@ -292,6 +292,7 @@ Known values:
     Python 3.15a4 3659 (Add CALL_FUNCTION_EX specialization)
     Python 3.15a4 3660 (Change generator preamble code)
     Python 3.15a4 3661 (Lazy imports IMPORT_NAME opcode changes)
+    Python 3.15a6 3662 (Add counter to RESUME)
 
 
     Python 3.16 will start with 3700
@@ -305,7 +306,7 @@ PC/launcher.c must also be updated.
 
 */
 
-#define PYC_MAGIC_NUMBER 3661
+#define PYC_MAGIC_NUMBER 3662
 /* This is equivalent to converting PYC_MAGIC_NUMBER to 2 bytes
    (little-endian) and then appending b'\r\n'. */
 #define PYC_MAGIC_NUMBER_TOKEN \

diff --git a/Include/internal/pycore_opcode_metadata.h b/Include/internal/pycore_opcode_metadata.h
diff --git a/Include/internal/pycore_uop.h b/Include/internal/pycore_uop.h
@@ -36,7 +36,7 @@ typedef struct _PyUOpInstruction{
 } _PyUOpInstruction;
 
 // This is the length of the trace we translate initially.
-#ifdef Py_DEBUG
+#if defined(Py_DEBUG) && defined(_Py_JIT)
     // With asserts, the stencils are a lot larger
 #define UOP_MAX_TRACE_LENGTH 1000
 #else