gh-116968: Reimplement Tier 2 counters (#117144)

Introduce a unified 16-bit backoff counter type (``_Py_BackoffCounter``),
shared between the Tier 1 adaptive specializer and the Tier 2 optimizer. The
API used for adaptive specialization counters is changed but the behavior is
(supposed to be) identical.

The behavior of the Tier 2 counters is changed:
- There are no longer dynamic thresholds (we never varied these).
- All counters now use the same exponential backoff.
- The counter for ``JUMP_BACKWARD`` starts counting down from 16.
- The ``temperature`` in side exits starts counting down from 64.

1 files changed, 4 insertions, 4 deletions

diff --git a/Python/instrumentation.c b/Python/instrumentation.c
index 018cd66..0f60290 100644
--- a/Python/instrumentation.c
+++ b/Python/instrumentation.c
@@ -590,7 +590,7 @@ de_instrument(PyCodeObject *code, int i, int event)
     CHECK(_PyOpcode_Deopt[deinstrumented] == deinstrumented);
     *opcode_ptr = deinstrumented;
     if (_PyOpcode_Caches[deinstrumented]) {
-        instr[1].cache = adaptive_counter_warmup();
+        instr[1].counter = adaptive_counter_warmup();
     }
 }
 
@@ -611,7 +611,7 @@ de_instrument_line(PyCodeObject *code, int i)
     CHECK(original_opcode == _PyOpcode_Deopt[original_opcode]);
     instr->op.code = original_opcode;
     if (_PyOpcode_Caches[original_opcode]) {
-        instr[1].cache = adaptive_counter_warmup();
+        instr[1].counter = adaptive_counter_warmup();
     }
     assert(instr->op.code != INSTRUMENTED_LINE);
 }
@@ -634,7 +634,7 @@ de_instrument_per_instruction(PyCodeObject *code, int i)
     CHECK(original_opcode == _PyOpcode_Deopt[original_opcode]);
     *opcode_ptr = original_opcode;
     if (_PyOpcode_Caches[original_opcode]) {
-        instr[1].cache = adaptive_counter_warmup();
+        instr[1].counter = adaptive_counter_warmup();
     }
     assert(*opcode_ptr != INSTRUMENTED_INSTRUCTION);
     assert(instr->op.code != INSTRUMENTED_INSTRUCTION);
@@ -667,7 +667,7 @@ instrument(PyCodeObject *code, int i)
         assert(instrumented);
         *opcode_ptr = instrumented;
         if (_PyOpcode_Caches[deopt]) {
-            instr[1].cache = adaptive_counter_warmup();
+            instr[1].counter = adaptive_counter_warmup();
         }
     }
 }