More microoptimizations

from_cpython/Modules/_sre.c

@@ -3538,13 +3538,12 @@ _pair(Py_ssize_t i1, Py_ssize_t i2)
 }
 
 static PyObject*
-match_span(MatchObject* self, PyObject* args)
+match_span(MatchObject* self, PyObject* index_)
 {
     Py_ssize_t index;
 
-    PyObject* index_ = Py_False; /* zero */
-    if (!PyArg_UnpackTuple(args, "span", 0, 1, &index_))
-        return NULL;
+    if (!index_)
+        index_ = Py_False; /* zero */
 
     index = match_getindex(self, index_);
 
@@ -3682,7 +3681,7 @@ static PyMethodDef match_methods[] = {
     {"group", (PyCFunction) match_group, METH_VARARGS, match_group_doc},
     {"start", (PyCFunction) match_start, METH_VARARGS, match_start_doc},
     {"end", (PyCFunction) match_end, METH_VARARGS, match_end_doc},
-    {"span", (PyCFunction) match_span, METH_VARARGS, match_span_doc},
+    {"span", (PyCFunction) match_span, METH_O | METH_D1, match_span_doc},
     {"groups", (PyCFunction) match_groups, METH_VARARGS|METH_KEYWORDS,
         match_groups_doc},
     {"groupdict", (PyCFunction) match_groupdict, METH_VARARGS|METH_KEYWORDS,

src/runtime/objmodel.cpp

@@ -3559,7 +3559,20 @@ void rearrangeArgumentsInternal(ParamReceiveSpec paramspec, const ParamNames* pa
             }
         }
 
-        Box* ovarargs = BoxedTuple::create(unused_positional.size(), unused_positional.data());
+        Box* ovarargs;
+        if (argspec.num_args == 0 && paramspec.num_args == 0 && (!varargs || varargs->cls == tuple_cls)) {
+            // We probably could have cut out a lot more of the overhead in this case:
+            assert(varargs_size == unused_positional.size());
+
+            if (!varargs)
+                ovarargs = EmptyTuple;
+            else
+                ovarargs = varargs;
+        } else {
+            ovarargs = BoxedTuple::create(unused_positional.size(), unused_positional.data());
+        }
+        assert(ovarargs->cls == tuple_cls);
+
         getArg(varargs_idx, oarg1, oarg2, oarg3, oargs) = ovarargs;
     } else if (unused_positional.size()) {
         raiseExcHelper(TypeError, "%s() takes at most %d argument%s (%ld given)", func_name_cb(), paramspec.num_args,

src/runtime/str.cpp

@@ -1867,7 +1867,8 @@ Box* strReplace(Box* _self, Box* _old, Box* _new, Box** _args) {
     std::string s = self->s();
 
     bool single_char = old->size() == 1;
-    for (int num_replaced = 0; num_replaced < max_replaces || max_replaces < 0; ++num_replaced) {
+    int num_replaced = 0;
+    for (; num_replaced < max_replaces || max_replaces < 0; ++num_replaced) {
         if (single_char)
             start_pos = s.find(old->s()[0], start_pos);
         else
@@ -1878,6 +1879,10 @@ Box* strReplace(Box* _self, Box* _old, Box* _new, Box** _args) {
         s.replace(start_pos, old->size(), new_->s());
         start_pos += new_->size(); // Handles case where 'to' is a substring of 'from'
     }
+
+    if (num_replaced == 0 && self->cls == str_cls)
+        return self;
+
     return boxString(s);
 }