Transform "x in (1,2,3)" to "x in frozenset([1,2,3])".
Inspired by Skip's idea to recognize the throw-away nature of sequences
in this context and to transform their type to one with better performance.
diff --git a/Lib/test/test_peepholer.py b/Lib/test/test_peepholer.py
index 34bd99f..bedf763 100644
--- a/Lib/test/test_peepholer.py
+++ b/Lib/test/test_peepholer.py
@@ -133,6 +133,16 @@
asm = dis_single('a="x"*1000')
self.assert_('(1000)' in asm)
+ def test_set_conversion(self):
+ for line in (
+ 'x in (1,2,3)',
+ 'x not in (1,2,3)',
+ 'not x in (1,2,3)',
+ 'not x not in (1,2,3)',
+ ):
+ asm = dis_single(line)
+ self.assert_('frozenset' in asm)
+
def test_elim_extra_return(self):
# RETURN LOAD_CONST None RETURN --> RETURN
def f(x):
diff --git a/Python/compile.c b/Python/compile.c
index acfbfe1..de07c97 100644
--- a/Python/compile.c
+++ b/Python/compile.c
@@ -540,6 +540,47 @@
return 1;
}
+/* Replace LOAD_CONST tuple with LOAD_CONST frozenset in the context
+ of a single-use constant for "in" and "not in" tests.
+*/
+int
+try_set_conversion(unsigned char *codestr, PyObject *consts)
+{
+ PyObject *newconst, *constant;
+ int arg, len_consts;
+
+ /* Pre-conditions */
+ assert(PyList_CheckExact(consts));
+ assert(codestr[0] == LOAD_CONST);
+ assert(codestr[3] == COMPARE_OP);
+ assert(GETARG(codestr, 3) == 6 || GETARG(codestr, 3) == 7);
+
+ /* Attempt to convert constant to a frozenset. Bail-out with no
+ changes if the tuple contains unhashable values. */
+ arg = GETARG(codestr, 0);
+ constant = PyList_GET_ITEM(consts, arg);
+ if (constant->ob_type != &PyTuple_Type)
+ return 0;
+ newconst = PyObject_CallFunctionObjArgs(
+ (PyObject *)&PyFrozenSet_Type, constant, NULL);
+ if (newconst == NULL) {
+ PyErr_Clear();
+ return 0;
+ }
+
+ /* Append new constant onto consts list.*/
+ len_consts = PyList_GET_SIZE(consts);
+ if (PyList_Append(consts, newconst)) {
+ Py_DECREF(newconst);
+ return 0;
+ }
+ Py_DECREF(newconst);
+
+ /* Write new LOAD_CONST newconst on top of LOAD_CONST oldconst */
+ SETARG(codestr, 0, len_consts);
+ return 1;
+}
+
static unsigned int *
markblocks(unsigned char *code, int len)
{
@@ -665,9 +706,15 @@
/* not a is b --> a is not b
not a in b --> a not in b
not a is not b --> a is b
- not a not in b --> a in b */
+ not a not in b --> a in b
+
+ a in c --> a in frozenset(c)
+ where c is a constant tuple of hashable values
+ */
case COMPARE_OP:
j = GETARG(codestr, i);
+ if (lastlc >= 1 && (j == 6 || j == 7) && ISBASICBLOCK(blocks,i-3,6))
+ try_set_conversion(&codestr[i-3], consts);
if (j < 6 || j > 9 ||
codestr[i+3] != UNARY_NOT ||
!ISBASICBLOCK(blocks,i,4))