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Issue #2183: Simplify and optimize bytecode for list comprehensions.

This commit is contained in:
Antoine Pitrou 2008-12-17 00:38:28 +00:00
parent 43caaa09ea
commit d0c3515bc5
9 changed files with 34 additions and 63 deletions
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6
Doc/library/dis.rst
View File

@ -463,9 +463,11 @@ Miscellaneous opcodes.
address to jump to (which should be a ``FOR_ITER`` instruction).
.. opcode:: LIST_APPEND ()
.. opcode:: LIST_APPEND (i)
Calls ``list.append(TOS1, TOS)``. Used to implement list comprehensions.
Calls ``list.append(TOS[-i], TOS)``. Used to implement list comprehensions.
While the appended value is popped off, the list object remains on the
stack so that it is available for further iterations of the loop.
.. opcode:: LOAD_LOCALS ()

2
Include/opcode.h
View File

@ -22,7 +22,6 @@ extern "C" {
#define UNARY_INVERT 15
#define LIST_APPEND 18
#define BINARY_POWER 19
#define BINARY_MULTIPLY 20
@ -89,6 +88,7 @@ extern "C" {
#define DELETE_NAME 91 /* "" */
#define UNPACK_SEQUENCE 92 /* Number of sequence items */
#define FOR_ITER 93
#define LIST_APPEND 94
#define STORE_ATTR 95 /* Index in name list */
#define DELETE_ATTR 96 /* "" */

12
Lib/compiler/pycodegen.py
View File

@ -570,16 +570,10 @@ class CodeGenerator:
self.nextBlock(end)
# list comprehensions
__list_count = 0
def visitListComp(self, node):
self.set_lineno(node)
# setup list
tmpname = "$list%d" % self.__list_count
self.__list_count = self.__list_count + 1
self.emit('BUILD_LIST', 0)
self.emit('DUP_TOP')
self._implicitNameOp('STORE', tmpname)
stack = []
for i, for_ in zip(range(len(node.quals)), node.quals):
@ -591,9 +585,8 @@ class CodeGenerator:
self.visit(if_, cont)
stack.insert(0, (start, cont, anchor))
self._implicitNameOp('LOAD', tmpname)
self.visit(node.expr)
self.emit('LIST_APPEND')
self.emit('LIST_APPEND', len(node.quals) + 1)
for start, cont, anchor in stack:
if cont:
@ -604,9 +597,6 @@ class CodeGenerator:
self.nextBlock(skip_one)
self.emit('JUMP_ABSOLUTE', start)
self.startBlock(anchor)
self._implicitNameOp('DELETE', tmpname)
self.__list_count = self.__list_count - 1
def visitListCompFor(self, node):
start = self.newBlock()

3
Lib/opcode.py
View File

@ -58,7 +58,6 @@ def_op('UNARY_CONVERT', 13)
def_op('UNARY_INVERT', 15)
def_op('LIST_APPEND', 18)
def_op('BINARY_POWER', 19)
def_op('BINARY_MULTIPLY', 20)
def_op('BINARY_DIVIDE', 21)
@ -128,7 +127,7 @@ name_op('STORE_NAME', 90) # Index in name list
name_op('DELETE_NAME', 91) # ""
def_op('UNPACK_SEQUENCE', 92) # Number of tuple items
jrel_op('FOR_ITER', 93)
def_op('LIST_APPEND', 94)
name_op('STORE_ATTR', 95) # Index in name list
name_op('DELETE_ATTR', 96) # ""
name_op('STORE_GLOBAL', 97) # ""

32
Lib/test/test_dis.py
View File

@ -54,29 +54,25 @@ def bug1333982(x=[]):
dis_bug1333982 = """\
%-4d 0 LOAD_CONST 1 (0)
3 JUMP_IF_TRUE 41 (to 47)
3 JUMP_IF_TRUE 33 (to 39)
6 POP_TOP
7 LOAD_GLOBAL 0 (AssertionError)
10 BUILD_LIST 0
13 DUP_TOP
14 STORE_FAST 1 (_[1])
17 LOAD_FAST 0 (x)
20 GET_ITER
>> 21 FOR_ITER 13 (to 37)
24 STORE_FAST 2 (s)
27 LOAD_FAST 1 (_[1])
30 LOAD_FAST 2 (s)
33 LIST_APPEND
34 JUMP_ABSOLUTE 21
>> 37 DELETE_FAST 1 (_[1])
13 LOAD_FAST 0 (x)
16 GET_ITER
>> 17 FOR_ITER 12 (to 32)
20 STORE_FAST 1 (s)
23 LOAD_FAST 1 (s)
26 LIST_APPEND 2
29 JUMP_ABSOLUTE 17
%-4d 40 LOAD_CONST 2 (1)
43 BINARY_ADD
44 RAISE_VARARGS 2
>> 47 POP_TOP
%-4d >> 32 LOAD_CONST 2 (1)
35 BINARY_ADD
36 RAISE_VARARGS 2
>> 39 POP_TOP
%-4d 48 LOAD_CONST 0 (None)
51 RETURN_VALUE
%-4d 40 LOAD_CONST 0 (None)
43 RETURN_VALUE
"""%(bug1333982.func_code.co_firstlineno + 1,
bug1333982.func_code.co_firstlineno + 2,
bug1333982.func_code.co_firstlineno + 3)

3
Misc/NEWS
View File

@ -12,6 +12,9 @@ What's New in Python 2.7 alpha 1
Core and Builtins
-----------------
- Issue #2183: Simplify and optimize bytecode for list comprehensions.
Original patch by Neal Norwitz.
- Issue #4597: Fixed exception handling when the __exit__ function of a
context manager returns a value that cannot be converted to a bool.

3
Python/ceval.c
View File

@ -1294,9 +1294,8 @@ PyEval_EvalFrameEx(PyFrameObject *f, int throwflag)
case LIST_APPEND:
w = POP();
v = POP();
v = stack_pointer[-oparg];
err = PyList_Append(v, w);
Py_DECREF(v);
Py_DECREF(w);
if (err == 0) {
PREDICT(JUMP_ABSOLUTE);

31
Python/compile.c
View File

@ -693,7 +693,7 @@ opcode_stack_effect(int opcode, int oparg)
return 0;
case LIST_APPEND:
return -2;
return -1;
case BINARY_POWER:
case BINARY_MULTIPLY:
@ -2599,9 +2599,8 @@ compiler_call(struct compiler *c, expr_ty e)
}
static int
compiler_listcomp_generator(struct compiler *c, PyObject *tmpname,
asdl_seq *generators, int gen_index,
expr_ty elt)
compiler_listcomp_generator(struct compiler *c, asdl_seq *generators,
int gen_index, expr_ty elt)
{
/* generate code for the iterator, then each of the ifs,
and then write to the element */
@ -2638,16 +2637,13 @@ compiler_listcomp_generator(struct compiler *c, PyObject *tmpname,
}
if (++gen_index < asdl_seq_LEN(generators))
if (!compiler_listcomp_generator(c, tmpname,
generators, gen_index, elt))
if (!compiler_listcomp_generator(c, generators, gen_index, elt))
return 0;
/* only append after the last for generator */
if (gen_index >= asdl_seq_LEN(generators)) {
if (!compiler_nameop(c, tmpname, Load))
return 0;
VISIT(c, expr, elt);
ADDOP(c, LIST_APPEND);
ADDOP_I(c, LIST_APPEND, gen_index+1);
compiler_use_next_block(c, skip);
}
@ -2659,10 +2655,6 @@ compiler_listcomp_generator(struct compiler *c, PyObject *tmpname,
}
ADDOP_JABS(c, JUMP_ABSOLUTE, start);
compiler_use_next_block(c, anchor);
/* delete the temporary list name added to locals */
if (gen_index == 1)
if (!compiler_nameop(c, tmpname, Del))
return 0;
return 1;
}
@ -2670,21 +2662,10 @@ compiler_listcomp_generator(struct compiler *c, PyObject *tmpname,
static int
compiler_listcomp(struct compiler *c, expr_ty e)
{
identifier tmp;
int rc = 0;
asdl_seq *generators = e->v.ListComp.generators;
assert(e->kind == ListComp_kind);
tmp = compiler_new_tmpname(c);
if (!tmp)
return 0;
ADDOP_I(c, BUILD_LIST, 0);
ADDOP(c, DUP_TOP);
if (compiler_nameop(c, tmp, Store))
rc = compiler_listcomp_generator(c, tmp, generators, 0,
return compiler_listcomp_generator(c, e->v.ListComp.generators, 0,
e->v.ListComp.elt);
Py_DECREF(tmp);
return rc;
}
static int

3
Python/import.c
View File

@ -73,9 +73,10 @@ extern time_t PyOS_GetLastModificationTime(char *, FILE *);
Python 2.5c2: 62131 (fix wrong code: for x, in ... in listcomp/genexp)
Python 2.6a0: 62151 (peephole optimizations and STORE_MAP opcode)
Python 2.6a1: 62161 (WITH_CLEANUP optimization)
Python 2.7a0: 62171 (optimize list comprehensions/change LIST_APPEND)
.
*/
#define MAGIC (62161 | ((long)'\r'<<16) | ((long)'\n'<<24))
#define MAGIC (62171 | ((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