gh-100188: Reduce misses in BINARY_SUBSCR_(LIST/TUPLE)_INT (#100189)

Don't specialize if the index is negative.
python · Dec 20, 2022 · c18d831 · c18d831
1 parent 44892d4
commit c18d831
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diff --git a/Misc/NEWS.d/next/Core and Builtins/2022-12-12-05-30-12.gh-issue-100188.sGCSMR.rst b/Misc/NEWS.d/next/Core and Builtins/2022-12-12-05-30-12.gh-issue-100188.sGCSMR.rst
@@ -0,0 +1,3 @@
+The ``BINARY_SUBSCR_LIST_INT`` and ``BINARY_SUBSCR_TUPLE_INT``
+instructions are no longer used for negative integers because
+those instructions always miss when encountering negative integers.
diff --git a/Python/specialize.c b/Python/specialize.c
@@ -1302,17 +1302,25 @@ _Py_Specialize_BinarySubscr(
     PyTypeObject *container_type = Py_TYPE(container);
     if (container_type == &PyList_Type) {
         if (PyLong_CheckExact(sub)) {
-            _py_set_opcode(instr, BINARY_SUBSCR_LIST_INT);
-            goto success;
+            if (Py_SIZE(sub) == 0 || Py_SIZE(sub) == 1) {
+                _py_set_opcode(instr, BINARY_SUBSCR_LIST_INT);
+                goto success;
+            }
+            SPECIALIZATION_FAIL(BINARY_SUBSCR, SPEC_FAIL_OUT_OF_RANGE);
+            goto fail;
         }
         SPECIALIZATION_FAIL(BINARY_SUBSCR,
             PySlice_Check(sub) ? SPEC_FAIL_SUBSCR_LIST_SLICE : SPEC_FAIL_OTHER);
         goto fail;
     }
     if (container_type == &PyTuple_Type) {
         if (PyLong_CheckExact(sub)) {
-            _py_set_opcode(instr, BINARY_SUBSCR_TUPLE_INT);
-            goto success;
+            if (Py_SIZE(sub) == 0 || Py_SIZE(sub) == 1) {
+                _py_set_opcode(instr, BINARY_SUBSCR_TUPLE_INT);
+                goto success;
+            }
+            SPECIALIZATION_FAIL(BINARY_SUBSCR, SPEC_FAIL_OUT_OF_RANGE);
+            goto fail;
         }
         SPECIALIZATION_FAIL(BINARY_SUBSCR,
             PySlice_Check(sub) ? SPEC_FAIL_SUBSCR_TUPLE_SLICE : SPEC_FAIL_OTHER);