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Issue #6690: Optimize the bytecode for expressions such as x in {1, 2, 3},

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where the right hand operand is a set of constants, by turning the set into
a frozenset and pre-building it as a constant.  The comparison operation
is made against the constant instead of building a new set each time it is
executed (a similar optimization already existed which turned a list of
constants into a pre-built tuple).  Patch and additional tests by Dave
Malcolm.
This commit is contained in:
Antoine Pitrou 2010-01-16 18:37:38 +00:00
parent a8f480f545
commit b7fbcd396f
3 changed files with 73 additions and 4 deletions
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20
Python/peephole.c
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@ -31,7 +31,8 @@
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.
Also works for BUILD_LIST when followed by an "in" or "not in" test.
Also works for BUILD_LIST and BUILT_SET when followed by an "in" or "not in"
test; for BUILD_SET it assembles a frozenset rather than a tuple.
*/
static int
tuple_of_constants(unsigned char *codestr, Py_ssize_t n, PyObject *consts)
@ -41,7 +42,7 @@ tuple_of_constants(unsigned char *codestr, Py_ssize_t n, PyObject *consts)
/* Pre-conditions */
assert(PyList_CheckExact(consts));
assert(codestr[n*3] == BUILD_TUPLE || codestr[n*3] == BUILD_LIST);
assert(codestr[n*3] == BUILD_TUPLE || codestr[n*3] == BUILD_LIST || codestr[n*3] == BUILD_SET);
assert(GETARG(codestr, (n*3)) == n);
for (i=0 ; i<n ; i++)
assert(codestr[i*3] == LOAD_CONST);
@ -59,6 +60,16 @@ tuple_of_constants(unsigned char *codestr, Py_ssize_t n, PyObject *consts)
PyTuple_SET_ITEM(newconst, i, constant);
}
/* If it's a BUILD_SET, use the PyTuple we just built to create a
PyFrozenSet, and use that as the constant instead: */
if (codestr[n*3] == BUILD_SET) {
PyObject *tuple = newconst;
newconst = PyFrozenSet_New(tuple);
Py_DECREF(tuple);
if (newconst == NULL)
return 0;
}
/* Append folded constant onto consts */
if (PyList_Append(consts, newconst)) {
Py_DECREF(newconst);
@ -436,20 +447,21 @@ PyCode_Optimize(PyObject *code, PyObject* consts, PyObject *names,
cumlc = 0;
break;
/* Try to fold tuples of constants (includes a case for lists
/* Try to fold tuples of constants (includes a case for lists and sets
which are only used for "in" and "not in" tests).
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:
case BUILD_LIST:
case BUILD_SET:
j = GETARG(codestr, i);
h = i - 3 * j;
if (h >= 0 &&
j <= lastlc &&
((opcode == BUILD_TUPLE &&
ISBASICBLOCK(blocks, h, 3*(j+1))) ||
(opcode == BUILD_LIST &&
((opcode == BUILD_LIST || opcode == BUILD_SET) &&
codestr[i+3]==COMPARE_OP &&
ISBASICBLOCK(blocks, h, 3*(j+2)) &&
(GETARG(codestr,i+3)==6 ||