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bpo-43693: Eliminate unused "fast locals". #26587

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merged 10 commits into from
Jun 15, 2021
Merged

bpo-43693: Eliminate unused "fast locals". #26587

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d63f73e
Merge cell locals with var locals for args.
ericsnowcurrently May 10, 2021
db2fd06
Eliminate co_cell2arg.
ericsnowcurrently May 10, 2021
6cae5e0
Add a NEWS entry.
ericsnowcurrently Jun 7, 2021
b5ef8e1
Bump the .pyc magic number.
ericsnowcurrently Jun 9, 2021
0e1cbc4
Drop an expensive check from super_init_without_args().
ericsnowcurrently Jun 15, 2021
2ec5ae4
Do not export _PyFrame_OpAlreadyRan().
ericsnowcurrently Jun 15, 2021
4b086e9
Check only the free vars in super_init_without_args().
ericsnowcurrently Jun 15, 2021
09c3cdd
Simplify a comment.
ericsnowcurrently Jun 15, 2021
8693744
Sort the MAKE_CELL ops by oparg.
ericsnowcurrently Jun 15, 2021
bdb12a7
Add a light-weight check to super_init_without_args().
ericsnowcurrently Jun 15, 2021
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Merge cell locals with var locals for args.
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@ericsnowcurrently
ericsnowcurrently committed Jun 14, 2021
commit d63f73ebb31108f42e245f775a5613b88917288a
3 changes: 2 additions & 1 deletion Include/cpython/code.h
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Original file line number Diff line number Diff line change
Expand Up @@ -87,7 +87,8 @@ struct PyCodeObject {
// redundant values (derived from co_localsplusnames and co_localspluskinds)
int co_nlocalsplus; /* number of local + cell + free variables */
int co_nlocals; /* number of local variables */
int co_ncellvars; /* number of cell variables */
int co_nplaincellvars; /* number of non-arg cell variables */
int co_ncellvars; /* total number of cell variables */
int co_nfreevars; /* number of free variables */
// lazily-computed values
PyObject *co_varnames; /* tuple of strings (local variable names) */
Expand Down
42 changes: 21 additions & 21 deletions Lib/test/test_dis.py
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Original file line number Diff line number Diff line change
Expand Up @@ -427,9 +427,9 @@ def foo(x):
return foo

dis_nested_0 = """\
0 MAKE_CELL 2 (y)
0 MAKE_CELL 0 (y)

%3d 2 LOAD_CLOSURE 2 (y)
%3d 2 LOAD_CLOSURE 0 (y)
4 BUILD_TUPLE 1
6 LOAD_CONST 1 (<code object foo at 0x..., file "%s", line %d>)
8 LOAD_CONST 2 ('_h.<locals>.foo')
Expand All @@ -446,14 +446,14 @@ def foo(x):

dis_nested_1 = """%s
Disassembly of <code object foo at 0x..., file "%s", line %d>:
0 MAKE_CELL 1 (x)
0 MAKE_CELL 0 (x)

%3d 2 LOAD_CLOSURE 1 (x)
%3d 2 LOAD_CLOSURE 0 (x)
4 BUILD_TUPLE 1
6 LOAD_CONST 1 (<code object <listcomp> at 0x..., file "%s", line %d>)
8 LOAD_CONST 2 ('_h.<locals>.foo.<locals>.<listcomp>')
10 MAKE_FUNCTION 8 (closure)
12 LOAD_DEREF 2 (y)
12 LOAD_DEREF 1 (y)
14 GET_ITER
16 CALL_FUNCTION 1
18 RETURN_VALUE
Expand Down Expand Up @@ -966,19 +966,19 @@ def jumpy():

Instruction = dis.Instruction
expected_opinfo_outer = [
Instruction(opname='MAKE_CELL', opcode=135, arg=3, argval='a', argrepr='a', offset=0, starts_line=None, is_jump_target=False),
Instruction(opname='MAKE_CELL', opcode=135, arg=4, argval='b', argrepr='b', offset=2, starts_line=None, is_jump_target=False),
Instruction(opname='MAKE_CELL', opcode=135, arg=0, argval='a', argrepr='a', offset=0, starts_line=None, is_jump_target=False),
Instruction(opname='MAKE_CELL', opcode=135, arg=1, argval='b', argrepr='b', offset=2, starts_line=None, is_jump_target=False),
Instruction(opname='LOAD_CONST', opcode=100, arg=8, argval=(3, 4), argrepr='(3, 4)', offset=4, starts_line=2, is_jump_target=False),
Instruction(opname='LOAD_CLOSURE', opcode=136, arg=3, argval='a', argrepr='a', offset=6, starts_line=None, is_jump_target=False),
Instruction(opname='LOAD_CLOSURE', opcode=136, arg=4, argval='b', argrepr='b', offset=8, starts_line=None, is_jump_target=False),
Instruction(opname='LOAD_CLOSURE', opcode=136, arg=0, argval='a', argrepr='a', offset=6, starts_line=None, is_jump_target=False),
Instruction(opname='LOAD_CLOSURE', opcode=136, arg=1, argval='b', argrepr='b', offset=8, starts_line=None, is_jump_target=False),
Instruction(opname='BUILD_TUPLE', opcode=102, arg=2, argval=2, argrepr='', offset=10, starts_line=None, is_jump_target=False),
Instruction(opname='LOAD_CONST', opcode=100, arg=3, argval=code_object_f, argrepr=repr(code_object_f), offset=12, starts_line=None, is_jump_target=False),
Instruction(opname='LOAD_CONST', opcode=100, arg=4, argval='outer.<locals>.f', argrepr="'outer.<locals>.f'", offset=14, starts_line=None, is_jump_target=False),
Instruction(opname='MAKE_FUNCTION', opcode=132, arg=9, argval=9, argrepr='defaults, closure', offset=16, starts_line=None, is_jump_target=False),
Instruction(opname='STORE_FAST', opcode=125, arg=2, argval='f', argrepr='f', offset=18, starts_line=None, is_jump_target=False),
Instruction(opname='LOAD_GLOBAL', opcode=116, arg=0, argval='print', argrepr='print', offset=20, starts_line=7, is_jump_target=False),
Instruction(opname='LOAD_DEREF', opcode=137, arg=3, argval='a', argrepr='a', offset=22, starts_line=None, is_jump_target=False),
Instruction(opname='LOAD_DEREF', opcode=137, arg=4, argval='b', argrepr='b', offset=24, starts_line=None, is_jump_target=False),
Instruction(opname='LOAD_DEREF', opcode=137, arg=0, argval='a', argrepr='a', offset=22, starts_line=None, is_jump_target=False),
Instruction(opname='LOAD_DEREF', opcode=137, arg=1, argval='b', argrepr='b', offset=24, starts_line=None, is_jump_target=False),
Instruction(opname='LOAD_CONST', opcode=100, arg=5, argval='', argrepr="''", offset=26, starts_line=None, is_jump_target=False),
Instruction(opname='LOAD_CONST', opcode=100, arg=6, argval=1, argrepr='1', offset=28, starts_line=None, is_jump_target=False),
Instruction(opname='BUILD_LIST', opcode=103, arg=0, argval=0, argrepr='', offset=30, starts_line=None, is_jump_target=False),
Expand All @@ -991,23 +991,23 @@ def jumpy():
]

expected_opinfo_f = [
Instruction(opname='MAKE_CELL', opcode=135, arg=3, argval='c', argrepr='c', offset=0, starts_line=None, is_jump_target=False),
Instruction(opname='MAKE_CELL', opcode=135, arg=4, argval='d', argrepr='d', offset=2, starts_line=None, is_jump_target=False),
Instruction(opname='MAKE_CELL', opcode=135, arg=0, argval='c', argrepr='c', offset=0, starts_line=None, is_jump_target=False),
Instruction(opname='MAKE_CELL', opcode=135, arg=1, argval='d', argrepr='d', offset=2, starts_line=None, is_jump_target=False),
Instruction(opname='LOAD_CONST', opcode=100, arg=5, argval=(5, 6), argrepr='(5, 6)', offset=4, starts_line=3, is_jump_target=False),
Instruction(opname='LOAD_CLOSURE', opcode=136, arg=5, argval='a', argrepr='a', offset=6, starts_line=None, is_jump_target=False),
Instruction(opname='LOAD_CLOSURE', opcode=136, arg=6, argval='b', argrepr='b', offset=8, starts_line=None, is_jump_target=False),
Instruction(opname='LOAD_CLOSURE', opcode=136, arg=3, argval='c', argrepr='c', offset=10, starts_line=None, is_jump_target=False),
Instruction(opname='LOAD_CLOSURE', opcode=136, arg=4, argval='d', argrepr='d', offset=12, starts_line=None, is_jump_target=False),
Instruction(opname='LOAD_CLOSURE', opcode=136, arg=3, argval='a', argrepr='a', offset=6, starts_line=None, is_jump_target=False),
Instruction(opname='LOAD_CLOSURE', opcode=136, arg=4, argval='b', argrepr='b', offset=8, starts_line=None, is_jump_target=False),
Instruction(opname='LOAD_CLOSURE', opcode=136, arg=0, argval='c', argrepr='c', offset=10, starts_line=None, is_jump_target=False),
Instruction(opname='LOAD_CLOSURE', opcode=136, arg=1, argval='d', argrepr='d', offset=12, starts_line=None, is_jump_target=False),
Instruction(opname='BUILD_TUPLE', opcode=102, arg=4, argval=4, argrepr='', offset=14, starts_line=None, is_jump_target=False),
Instruction(opname='LOAD_CONST', opcode=100, arg=3, argval=code_object_inner, argrepr=repr(code_object_inner), offset=16, starts_line=None, is_jump_target=False),
Instruction(opname='LOAD_CONST', opcode=100, arg=4, argval='outer.<locals>.f.<locals>.inner', argrepr="'outer.<locals>.f.<locals>.inner'", offset=18, starts_line=None, is_jump_target=False),
Instruction(opname='MAKE_FUNCTION', opcode=132, arg=9, argval=9, argrepr='defaults, closure', offset=20, starts_line=None, is_jump_target=False),
Instruction(opname='STORE_FAST', opcode=125, arg=2, argval='inner', argrepr='inner', offset=22, starts_line=None, is_jump_target=False),
Instruction(opname='LOAD_GLOBAL', opcode=116, arg=0, argval='print', argrepr='print', offset=24, starts_line=5, is_jump_target=False),
Instruction(opname='LOAD_DEREF', opcode=137, arg=5, argval='a', argrepr='a', offset=26, starts_line=None, is_jump_target=False),
Instruction(opname='LOAD_DEREF', opcode=137, arg=6, argval='b', argrepr='b', offset=28, starts_line=None, is_jump_target=False),
Instruction(opname='LOAD_DEREF', opcode=137, arg=3, argval='c', argrepr='c', offset=30, starts_line=None, is_jump_target=False),
Instruction(opname='LOAD_DEREF', opcode=137, arg=4, argval='d', argrepr='d', offset=32, starts_line=None, is_jump_target=False),
Instruction(opname='LOAD_DEREF', opcode=137, arg=3, argval='a', argrepr='a', offset=26, starts_line=None, is_jump_target=False),
Instruction(opname='LOAD_DEREF', opcode=137, arg=4, argval='b', argrepr='b', offset=28, starts_line=None, is_jump_target=False),
Instruction(opname='LOAD_DEREF', opcode=137, arg=0, argval='c', argrepr='c', offset=30, starts_line=None, is_jump_target=False),
Instruction(opname='LOAD_DEREF', opcode=137, arg=1, argval='d', argrepr='d', offset=32, starts_line=None, is_jump_target=False),
Instruction(opname='CALL_FUNCTION', opcode=131, arg=4, argval=4, argrepr='', offset=34, starts_line=None, is_jump_target=False),
Instruction(opname='POP_TOP', opcode=1, arg=None, argval=None, argrepr='', offset=36, starts_line=None, is_jump_target=False),
Instruction(opname='LOAD_FAST', opcode=124, arg=2, argval='inner', argrepr='inner', offset=38, starts_line=6, is_jump_target=False),
Expand Down
66 changes: 37 additions & 29 deletions Objects/codeobject.c
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Original file line number Diff line number Diff line change
Expand Up @@ -162,43 +162,28 @@ _Py_set_localsplus_info(int offset, PyObject *name, _PyLocalsPlusKind kind,
Py_INCREF(name);
PyTuple_SET_ITEM(names, offset, name);
kinds[offset] = kind;

if (kind == CO_FAST_CELL) {
// Cells can overlap with args, so mark those cases.
int nlocalsplus = (int)PyTuple_GET_SIZE(names);
for (int i = 0; i < nlocalsplus; i++) {
_PyLocalsPlusKind kind = kinds[i];
if (kind && !(kind & CO_FAST_LOCAL)) {
// We've moved past the locals.
break;
}
PyObject *varname = PyTuple_GET_ITEM(names, i);
int cmp = PyUnicode_Compare(name, varname);
if (cmp == 0) {
kinds[i] |= CO_FAST_CELL;
break;
}
assert(cmp > 0 || !PyErr_Occurred());
}
}
}

static void
get_localsplus_counts(PyObject *names, _PyLocalsPlusKinds kinds,
int *pnlocals, int *pncellvars,
int *pnlocals, int *pnplaincellvars, int *pncellvars,
int *pnfreevars)
{
int nlocals = 0;
int nplaincellvars = 0;
int ncellvars = 0;
int nfreevars = 0;
int nlocalsplus = Py_SAFE_DOWNCAST(PyTuple_GET_SIZE(names),
Py_ssize_t, int);
Py_ssize_t nlocalsplus = PyTuple_GET_SIZE(names);
for (int i = 0; i < nlocalsplus; i++) {
if (kinds[i] & CO_FAST_LOCAL) {
nlocals += 1;
if (kinds[i] & CO_FAST_CELL) {
ncellvars += 1;
}
}
else if (kinds[i] & CO_FAST_CELL) {
ncellvars += 1;
nplaincellvars += 1;
}
else if (kinds[i] & CO_FAST_FREE) {
nfreevars += 1;
Expand All @@ -207,6 +192,9 @@ get_localsplus_counts(PyObject *names, _PyLocalsPlusKinds kinds,
if (pnlocals != NULL) {
*pnlocals = nlocals;
}
if (pnplaincellvars != NULL) {
*pnplaincellvars = nplaincellvars;
}
if (pncellvars != NULL) {
*pncellvars = ncellvars;
}
Expand All @@ -227,10 +215,6 @@ get_localsplus_names(PyCodeObject *co, _PyLocalsPlusKind kind, int num)
if ((co->co_localspluskinds[offset] & kind) == 0) {
continue;
}
// For now there may be duplicates, which we ignore.
if (kind == CO_FAST_CELL && co->co_localspluskinds[offset] != kind) {
continue;
}
assert(index < num);
PyObject *name = PyTuple_GET_ITEM(co->co_localsplusnames, offset);
Py_INCREF(name);
Expand Down Expand Up @@ -283,7 +267,7 @@ _PyCode_Validate(struct _PyCodeConstructor *con)
* here to avoid the possibility of overflow (however remote). */
int nlocals;
get_localsplus_counts(con->localsplusnames, con->localspluskinds,
&nlocals, NULL, NULL);
&nlocals, NULL, NULL, NULL);
int nplainlocals = nlocals -
con->argcount -
con->kwonlyargcount -
Expand All @@ -301,9 +285,9 @@ static void
init_code(PyCodeObject *co, struct _PyCodeConstructor *con)
{
int nlocalsplus = (int)PyTuple_GET_SIZE(con->localsplusnames);
int nlocals, ncellvars, nfreevars;
int nlocals, nplaincellvars, ncellvars, nfreevars;
get_localsplus_counts(con->localsplusnames, con->localspluskinds,
&nlocals, &ncellvars, &nfreevars);
&nlocals, &nplaincellvars, &ncellvars, &nfreevars);

Py_INCREF(con->filename);
co->co_filename = con->filename;
Expand Down Expand Up @@ -341,6 +325,7 @@ init_code(PyCodeObject *co, struct _PyCodeConstructor *con)
co->co_cell2arg = NULL; // This will be set soon.
co->co_nlocalsplus = nlocalsplus;
co->co_nlocals = nlocals;
co->co_nplaincellvars = nplaincellvars;
co->co_ncellvars = ncellvars;
co->co_nfreevars = nfreevars;
co->co_varnames = NULL;
Expand Down Expand Up @@ -401,6 +386,7 @@ _PyCode_New(struct _PyCodeConstructor *con)
assert(totalargs <= co->co_nlocals);
/* Find cells which are also arguments. */
for (int i = 0; i < co->co_ncellvars; i++) {
continue;
PyObject *cellname = PyTuple_GET_ITEM(co->co_localsplusnames,
i + co->co_nlocals);
for (int j = 0; j < totalargs; j++) {
Expand Down Expand Up @@ -478,6 +464,23 @@ PyCode_NewWithPosOnlyArgs(int argcount, int posonlyargcount, int kwonlyargcount,
}
for (int i = 0; i < ncellvars; i++, offset++) {
PyObject *name = PyTuple_GET_ITEM(cellvars, i);
int argoffset = -1;
for (int j = 0; j < nvarnames; j++) {
int cmp = PyUnicode_Compare(PyTuple_GET_ITEM(varnames, j),
name);
assert(!PyErr_Occurred());
if (cmp == 0) {
argoffset = j;
break;
}
}
if (argoffset >= 0) {
// Merge the localsplus indices.
nlocalsplus -= 1;
offset -= 1;
localspluskinds[argoffset] |= CO_FAST_CELL;
continue;
}
_Py_set_localsplus_info(offset, name, CO_FAST_CELL,
localsplusnames, localspluskinds);
}
Expand All @@ -486,6 +489,11 @@ PyCode_NewWithPosOnlyArgs(int argcount, int posonlyargcount, int kwonlyargcount,
_Py_set_localsplus_info(offset, name, CO_FAST_FREE,
localsplusnames, localspluskinds);
}
// If any cells were args then nlocalsplus will have shrunk.
// We don't bother resizing localspluskinds.
if (_PyTuple_Resize(&localsplusnames, nlocalsplus) < 0) {
goto error;
}

struct _PyCodeConstructor con = {
.filename = filename,
Expand Down
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