Index: Python/ceval.c =================================================================== --- Python/ceval.c (revision 61058) +++ Python/ceval.c (working copy) @@ -1263,9 +1263,8 @@ 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); Index: Python/import.c =================================================================== --- Python/import.c (revision 61058) +++ Python/import.c (working copy) @@ -72,9 +72,10 @@ storing constants that should have been removed) Python 2.5c2: 62131 (fix wrong code: for x, in ... in listcomp/genexp) Python 2.6a0: 62151 (peephole optimizations and STORE_MAP opcode) + Python 2.6a0: 62161 (optimize list comprehensions/change LIST_APPEND) . */ -#define MAGIC (62151 | ((long)'\r'<<16) | ((long)'\n'<<24)) +#define MAGIC (62161 | ((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 Index: Python/compile.c =================================================================== --- Python/compile.c (revision 61058) +++ Python/compile.c (working copy) @@ -683,7 +683,7 @@ return 0; case LIST_APPEND: - return -2; + return -1; case BINARY_POWER: case BINARY_MULTIPLY: @@ -2578,9 +2578,8 @@ } 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 */ @@ -2617,16 +2616,13 @@ } 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); } @@ -2638,10 +2634,6 @@ } 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; } @@ -2649,21 +2641,10 @@ 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, - e->v.ListComp.elt); - Py_DECREF(tmp); - return rc; + return compiler_listcomp_generator(c, e->v.ListComp.generators, 0, + e->v.ListComp.elt); } static int Index: Include/opcode.h =================================================================== --- Include/opcode.h (revision 61058) +++ Include/opcode.h (working copy) @@ -22,7 +22,6 @@ #define UNARY_INVERT 15 -#define LIST_APPEND 18 #define BINARY_POWER 19 #define BINARY_MULTIPLY 20 @@ -89,6 +88,7 @@ #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 /* "" */ Index: Lib/opcode.py =================================================================== --- Lib/opcode.py (revision 61058) +++ Lib/opcode.py (working copy) @@ -58,7 +58,6 @@ 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('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) # "" Index: Lib/test/test_dis.py =================================================================== --- Lib/test/test_dis.py (revision 61058) +++ Lib/test/test_dis.py (working copy) @@ -54,29 +54,25 @@ 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)