SF patch #1031667: Fold tuples of constants into a single constant
Example:
>>> import dis
>>> dis.dis(compile('1,2,3', '', 'eval'))
0 0 LOAD_CONST 3 ((1, 2, 3))
3 RETURN_VALUE
diff --git a/Lib/test/test_peepholer.py b/Lib/test/test_peepholer.py
index 33eb0f5..913f805 100644
--- a/Lib/test/test_peepholer.py
+++ b/Lib/test/test_peepholer.py
@@ -64,15 +64,25 @@
def test_pack_unpack(self):
for line, elem in (
- ('a, = 1,', 'LOAD_CONST',),
- ('a, b = 1, 2', 'ROT_TWO',),
- ('a, b, c = 1, 2, 3', 'ROT_THREE',),
+ ('a, = a,', 'LOAD_CONST',),
+ ('a, b = a, b', 'ROT_TWO',),
+ ('a, b, c = a, b, c', 'ROT_THREE',),
):
asm = dis_single(line)
self.assert_(elem in asm)
self.assert_('BUILD_TUPLE' not in asm)
self.assert_('UNPACK_TUPLE' not in asm)
+ def test_folding_of_tuples_of_constants(self):
+ for line, elem in (
+ ('a = 1,2,3', '((1, 2, 3))',),
+ ('("a","b","c")', "(('a', 'b', 'c'))",),
+ ('a,b,c = 1,2,3', '((1, 2, 3))',),
+ ):
+ asm = dis_single(line)
+ self.assert_(elem in asm)
+ self.assert_('BUILD_TUPLE' not in asm)
+
def test_elim_extra_return(self):
# RETURN LOAD_CONST None RETURN --> RETURN
def f(x):
diff --git a/Misc/NEWS b/Misc/NEWS
index b87f128..3c2734b 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -12,6 +12,9 @@
Core and builtins
-----------------
+- The bytecode optimizer now folds tuples of constants into a single
+ constant.
+
- PyLong_AsUnsignedLong[Mask] now support int objects as well.
Extension modules
diff --git a/Python/compile.c b/Python/compile.c
index e8f4d67..9beb7da 100644
--- a/Python/compile.c
+++ b/Python/compile.c
@@ -380,6 +380,8 @@
}
}
+/* Begin: Peephole optimizations ----------------------------------------- */
+
#define GETARG(arr, i) ((int)((arr[i+2]<<8) + arr[i+1]))
#define UNCONDITIONAL_JUMP(op) (op==JUMP_ABSOLUTE || op==JUMP_FORWARD)
#define ABSOLUTE_JUMP(op) (op==JUMP_ABSOLUTE || op==CONTINUE_LOOP)
@@ -388,6 +390,56 @@
#define CODESIZE(op) (HAS_ARG(op) ? 3 : 1)
#define ISBASICBLOCK(blocks, start, bytes) (blocks[start]==blocks[start+bytes-1])
+/* Replace LOAD_CONST c1. LOAD_CONST c2 ... LOAD_CONST cn BUILD_TUPLE n
+ with LOAD_CONST (c1, c2, ... cn).
+ The consts table must still be in list form so that the
+ new constant (c1, c2, ... cn) can be appended.
+ Called with codestr pointing to the first LOAD_CONST.
+ Bails out with no change if one or more of the LOAD_CONSTs is missing. */
+static int
+tuple_of_constants(unsigned char *codestr, int n, PyObject *consts)
+{
+ PyObject *newconst, *constant;
+ int i, arg, len_consts;
+
+ /* Pre-conditions */
+ assert(PyList_CheckExact(consts));
+ assert(codestr[0] == LOAD_CONST);
+ assert(codestr[n*3] == BUILD_TUPLE);
+ assert(GETARG(codestr, (n*3)) == n);
+
+ /* Verify chain of n load_constants */
+ for (i=0 ; i<n ; i++)
+ if (codestr[i*3] != LOAD_CONST)
+ return 0;
+
+ /* Buildup new tuple of constants */
+ newconst = PyTuple_New(n);
+ if (newconst == NULL)
+ return 0;
+ for (i=0 ; i<n ; i++) {
+ arg = GETARG(codestr, (i*3));
+ constant = PyList_GET_ITEM(consts, arg);
+ Py_INCREF(constant);
+ PyTuple_SET_ITEM(newconst, i, constant);
+ }
+
+ /* Append folded constant onto consts */
+ len_consts = PyList_GET_SIZE(consts);
+ if (PyList_Append(consts, newconst)) {
+ Py_DECREF(newconst);
+ return 0;
+ }
+ Py_DECREF(newconst);
+
+ /* Write NOPs over old LOAD_CONSTS and
+ add a new LOAD_CONST newconst on top of the BUILD_TUPLE n */
+ memset(codestr, NOP, n*3);
+ codestr[n*3] = LOAD_CONST;
+ SETARG(codestr, (n*3), len_consts);
+ return 1;
+}
+
static unsigned int *
markblocks(unsigned char *code, int len)
{
@@ -423,6 +475,21 @@
return blocks;
}
+/* Perform basic peephole optimizations to components of a code object.
+ The consts object should still be in list form to allow new constants
+ to be appended.
+
+ To keep the optimizer simple, it bails out (does nothing) for code
+ containing extended arguments or that has a length over 32,700. That
+ allows us to avoid overflow and sign issues. Likewise, it bails when
+ the lineno table has complex encoding for gaps >= 255.
+
+ Optimizations are restricted to simple transformations occuring within a
+ single basic block. All transformations keep the code size the same or
+ smaller. For those that reduce size, the gaps are initially filled with
+ NOPs. Later those NOPs are removed and the jump addresses retargeted in
+ a single pass. Line numbering is adjusted accordingly. */
+
static PyObject *
optimize_code(PyObject *code, PyObject* consts, PyObject *names, PyObject *lineno_obj)
{
@@ -447,7 +514,7 @@
/* Avoid situations where jump retargeting could overflow */
codelen = PyString_Size(code);
- if (codelen > 32000)
+ if (codelen > 32700)
goto exitUnchanged;
/* Make a modifiable copy of the code string */
@@ -464,7 +531,7 @@
blocks = markblocks(codestr, codelen);
if (blocks == NULL)
goto exitUnchanged;
- assert(PyTuple_Check(consts));
+ assert(PyList_Check(consts));
for (i=0, nops=0 ; i<codelen ; i += CODESIZE(codestr[i])) {
addrmap[i] = i - nops;
@@ -511,8 +578,8 @@
name = PyString_AsString(PyTuple_GET_ITEM(names, j));
if (name == NULL || strcmp(name, "None") != 0)
continue;
- for (j=0 ; j < PyTuple_GET_SIZE(consts) ; j++) {
- if (PyTuple_GET_ITEM(consts, j) == Py_None) {
+ for (j=0 ; j < PyList_GET_SIZE(consts) ; j++) {
+ if (PyList_GET_ITEM(consts, j) == Py_None) {
codestr[i] = LOAD_CONST;
SETARG(codestr, i, j);
break;
@@ -525,17 +592,28 @@
j = GETARG(codestr, i);
if (codestr[i+3] != JUMP_IF_FALSE ||
codestr[i+6] != POP_TOP ||
- !ISBASICBLOCK(blocks,i,7) ||
- !PyObject_IsTrue(PyTuple_GET_ITEM(consts, j)))
+ !ISBASICBLOCK(blocks,i,7) ||
+ !PyObject_IsTrue(PyList_GET_ITEM(consts, j)))
continue;
memset(codestr+i, NOP, 7);
nops += 7;
break;
- /* Skip over BUILD_SEQN 1 UNPACK_SEQN 1.
+ /* Try to fold tuples of constants.
+ Skip over BUILD_SEQN 1 UNPACK_SEQN 1.
Replace BUILD_SEQN 2 UNPACK_SEQN 2 with ROT2.
Replace BUILD_SEQN 3 UNPACK_SEQN 3 with ROT3 ROT2. */
case BUILD_TUPLE:
+ j = GETARG(codestr, i);
+ h = i - 3 * j;
+ if (h >= 0 &&
+ codestr[h] == LOAD_CONST &&
+ ISBASICBLOCK(blocks, h, 3*(j+1)) &&
+ tuple_of_constants(&codestr[h], j, consts)) {
+ nops += 3 * j;
+ break;
+ }
+ /* Intentional fallthrough */
case BUILD_LIST:
j = GETARG(codestr, i);
if (codestr[i+3] != UNPACK_SEQUENCE ||
@@ -610,8 +688,8 @@
/* Replace RETURN LOAD_CONST None RETURN with just RETURN */
case RETURN_VALUE:
- if (i+4 >= codelen ||
- codestr[i+4] != RETURN_VALUE ||
+ if (i+4 >= codelen ||
+ codestr[i+4] != RETURN_VALUE ||
!ISBASICBLOCK(blocks,i,5))
continue;
memset(codestr+i+1, NOP, 4);
@@ -677,6 +755,8 @@
return code;
}
+/* End: Peephole optimizations ----------------------------------------- */
+
PyCodeObject *
PyCode_New(int argcount, int nlocals, int stacksize, int flags,
PyObject *code, PyObject *consts, PyObject *names,
@@ -4899,7 +4979,6 @@
if (sc.c_errors == 0) {
PyObject *consts, *names, *varnames, *filename, *name,
*freevars, *cellvars, *code;
- consts = PyList_AsTuple(sc.c_consts);
names = PyList_AsTuple(sc.c_names);
varnames = PyList_AsTuple(sc.c_varnames);
cellvars = dict_keys_inorder(sc.c_cellvars, 0);
@@ -4907,7 +4986,8 @@
PyTuple_GET_SIZE(cellvars));
filename = PyString_InternFromString(sc.c_filename);
name = PyString_InternFromString(sc.c_name);
- code = optimize_code(sc.c_code, consts, names, sc.c_lnotab);
+ code = optimize_code(sc.c_code, sc.c_consts, names, sc.c_lnotab);
+ consts = PyList_AsTuple(sc.c_consts);
if (!PyErr_Occurred())
co = PyCode_New(sc.c_argcount,
sc.c_nlocals,
diff --git a/Python/import.c b/Python/import.c
index 8bbd31b..61e4313 100644
--- a/Python/import.c
+++ b/Python/import.c
@@ -49,8 +49,9 @@
Python 2.3a0: 62011 (!)
Python 2.4a0: 62041
Python 2.4a3: 62051
+ Python 2.4b1: 62061
*/
-#define MAGIC (62051 | ((long)'\r'<<16) | ((long)'\n'<<24))
+#define MAGIC (62061 | ((long)'\r'<<16) | ((long)'\n'<<24))
/* Magic word as global; note that _PyImport_Init() can change the
value of this global to accommodate for alterations of how the