Address review

Author: Fidget-Spinner

Include/internal/pycore_optimizer.h

@@ -36,7 +36,7 @@ extern "C" {
 
 /* Exit quality thresholds: trace stops when fitness < exit_quality.
  * Higher = trace is more willing to stop here. */
-#define EXIT_QUALITY_CLOSE_LOOP      (FITNESS_INITIAL)
+#define EXIT_QUALITY_CLOSE_LOOP      (FITNESS_INITIAL - AVG_SLOTS_PER_INSTRUCTION*4)
 #define EXIT_QUALITY_ENTER_EXECUTOR  (FITNESS_INITIAL * 3 / 8)
 #define EXIT_QUALITY_DEFAULT         (FITNESS_INITIAL / 8)
 #define EXIT_QUALITY_SPECIALIZABLE   (FITNESS_INITIAL / 80)
@@ -48,13 +48,9 @@ extern "C" {
 /* Heuristic backward-edge exit quality: leave room for about 1 unroll and
  * N_BACKWARD_SLACK more bytecodes before reaching EXIT_QUALITY_CLOSE_LOOP,
  * based on AVG_SLOTS_PER_INSTRUCTION. */
-#define N_BACKWARD_SLACK           50
+#define N_BACKWARD_SLACK           10
 #define EXIT_QUALITY_BACKWARD_EDGE (EXIT_QUALITY_CLOSE_LOOP / 2 - N_BACKWARD_SLACK * AVG_SLOTS_PER_INSTRUCTION)
 
-/* Backward edge penalty for JUMP_BACKWARD_NO_INTERRUPT (coroutines/yield-from).
- * Smaller than FITNESS_BACKWARD_EDGE since we want to trace through them. */
-#define EXIT_QUALITY_BACKWARD_EDGE_COROUTINE  (EXIT_QUALITY_BACKWARD_EDGE / 8)
-
 /* Penalty for a perfectly balanced (50/50) branch.
  * 7 such branches (after per-slot cost) exhaust fitness to EXIT_QUALITY_DEFAULT.
  * The calculation assumes the branches are spread out roughly equally throughout the trace.

Python/optimizer.c

@@ -614,25 +614,19 @@ static inline int32_t
 compute_exit_quality(_Py_CODEUNIT *target_instr, int opcode,
                      const _PyJitTracerState *tracer)
 {
-    // We need to check for this, otherwise the first instruction (JUMP_BACKWARD usually)
-    // is mistakenly thought of as an exit.
-    if (uop_buffer_length((_PyJitUopBuffer *)&tracer->code_buffer) > CODE_SIZE_NO_PROGRESS) {
-        if (target_instr == tracer->initial_state.start_instr ||
-            target_instr == tracer->initial_state.close_loop_instr) {
-            return EXIT_QUALITY_CLOSE_LOOP;
-        }
-        else if (target_instr->op.code == ENTER_EXECUTOR && !_PyJit_EnterExecutorShouldStopTracing(opcode)) {
-            return EXIT_QUALITY_ENTER_EXECUTOR;
-        }
-        else if (opcode == JUMP_BACKWARD_JIT || opcode == JUMP_BACKWARD) {
-            return EXIT_QUALITY_BACKWARD_EDGE;
-        }
-        else if (opcode == JUMP_BACKWARD_NO_INTERRUPT) {
-            return EXIT_QUALITY_BACKWARD_EDGE_COROUTINE;
-        }
-        else if (_PyOpcode_Caches[_PyOpcode_Deopt[opcode]] > 0) {
-            return EXIT_QUALITY_SPECIALIZABLE;
-        }
+    if (target_instr == tracer->initial_state.close_loop_instr) {
+        return EXIT_QUALITY_CLOSE_LOOP;
+    }
+    else if (target_instr->op.code == ENTER_EXECUTOR && !_PyJit_EnterExecutorShouldStopTracing(opcode)) {
+        return EXIT_QUALITY_ENTER_EXECUTOR;
+    }
+    else if (opcode == JUMP_BACKWARD_JIT ||
+        opcode == JUMP_BACKWARD ||
+        opcode == JUMP_BACKWARD_NO_INTERRUPT) {
+        return EXIT_QUALITY_BACKWARD_EDGE;
+    }
+    else if (_PyOpcode_Caches[_PyOpcode_Deopt[opcode]] > 0) {
+        return EXIT_QUALITY_SPECIALIZABLE;
     }
     return EXIT_QUALITY_DEFAULT;
 }