Fix the counters

Author: Fidget-Spinner

Include/internal/pycore_backoff.h

@@ -129,6 +129,14 @@ initial_unreachable_backoff_counter(void)
     return make_backoff_counter(0, UNREACHABLE_BACKOFF);
 }
 
+// Required to not get stuck in infinite specialization loops due to specialization failure.
+// We use 2 here as tnere are a few scenarios:
+// 1. Freshly specialized from unspecialized, in which case the counter will be 1.
+// 2. Re-specialized from deopt, in which case the counter will be 1.
+// 3. Deopt -> Specialize -> Deopt -> Specialize, in which case the counter will be 2.
+// We do not want the 3rd case.
+#define MAX_SPECIALIZATION_TRIES 2
+
 #ifdef __cplusplus
 }
 #endif

Python/ceval_macros.h

@@ -135,8 +135,7 @@
 
 #if (_Py_TAIL_CALL_INTERP || USE_COMPUTED_GOTOS) && _Py_TIER2
 #  define IS_JIT_TRACING() (DISPATCH_TABLE_VAR == TRACING_DISPATCH_TABLE)
-// Required to not get stuck in infinite specialization loops due to specialization failure.
-#  define IS_JIT_TRACING_MAKING_PROGRESS() (IS_JIT_TRACING() && tstate->interp->jit_state.specialize_counter < 1)
+#  define IS_JIT_TRACING_MAKING_PROGRESS() (IS_JIT_TRACING() && tstate->interp->jit_state.specialize_counter < MAX_SPECIALIZATION_TRIES)
 #  define ENTER_TRACING() \
     DISPATCH_TABLE_VAR = TRACING_DISPATCH_TABLE;
 #  define LEAVE_TRACING() \

Python/optimizer.c

@@ -557,6 +557,14 @@ _PyJit_translate_single_bytecode_to_trace(
     _Py_CODEUNIT *next_instr)
 {
 
+#ifdef Py_DEBUG
+    char *python_lltrace = Py_GETENV("PYTHON_LLTRACE");
+    int lltrace = 0;
+    if (python_lltrace != NULL && *python_lltrace >= '0') {
+        lltrace = *python_lltrace - '0';  // TODO: Parse an int and all that
+    }
+#endif
+
     PyCodeObject *old_code = tstate->interp->jit_state.prev_instr_code;
     // Something else finalized the trace. This can happen in multi-threaded scenarios as our trace
     // addition from bytecode execution to here is not atomic.
@@ -576,13 +584,6 @@ _PyJit_translate_single_bytecode_to_trace(
         goto full;
     }
 
-#ifdef Py_DEBUG
-    char *python_lltrace = Py_GETENV("PYTHON_LLTRACE");
-    int lltrace = 0;
-    if (python_lltrace != NULL && *python_lltrace >= '0') {
-        lltrace = *python_lltrace - '0';  // TODO: Parse an int and all that
-    }
-#endif
     _Py_CODEUNIT *this_instr =  tstate->interp->jit_state.prev_instr;
     _Py_CODEUNIT *target_instr = this_instr;
     uint32_t target = 0;
@@ -593,8 +594,8 @@ _PyJit_translate_single_bytecode_to_trace(
     // We must point to the first EXTENDED_ARG when deopting.
     int oparg = tstate->interp->jit_state.prev_instr_oparg;
     int opcode = this_instr->op.code;
-    // Failed specialization twice in a row. Deopt!
-    if (tstate->interp->jit_state.specialize_counter >= 1) {
+    // Failed specialization many times. Deopt!
+    if (tstate->interp->jit_state.specialize_counter >= MAX_SPECIALIZATION_TRIES) {
         opcode = _PyOpcode_Deopt[opcode];
     }
     int rewind_oparg = oparg;