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bpo-29469: peephole: Remove const_stack #4879

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Merged
merged 5 commits into from
Dec 18, 2017
Merged

bpo-29469: peephole: Remove const_stack #4879

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915a1a4
bpo-29469: peephole: Remove const_stack
methane Dec 15, 2017
ca5bacf
fixup
methane Dec 15, 2017
b8d6ab0
Reformat code.
methane Dec 18, 2017
d435e6c
More cleanup
methane Dec 18, 2017
492f473
fix
methane Dec 18, 2017
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102 changes: 21 additions & 81 deletions Python/peephole.c
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Original file line number Diff line number Diff line change
Expand Up @@ -23,51 +23,6 @@
(blocks[start]==blocks[end])


#define CONST_STACK_CREATE() { \
const_stack_size = 256; \
const_stack = PyMem_New(PyObject *, const_stack_size); \
if (!const_stack) { \
PyErr_NoMemory(); \
goto exitError; \
} \
}

#define CONST_STACK_DELETE() do { \
if (const_stack) \
PyMem_Free(const_stack); \
} while(0)

#define CONST_STACK_LEN() ((unsigned)(const_stack_top + 1))

#define CONST_STACK_PUSH_OP(i) do { \
PyObject *_x; \
assert(_Py_OPCODE(codestr[i]) == LOAD_CONST); \
assert(PyList_GET_SIZE(consts) > (Py_ssize_t)get_arg(codestr, i)); \
_x = PyList_GET_ITEM(consts, get_arg(codestr, i)); \
if (++const_stack_top >= const_stack_size) { \
const_stack_size *= 2; \
PyMem_Resize(const_stack, PyObject *, const_stack_size); \
if (!const_stack) { \
PyErr_NoMemory(); \
goto exitError; \
} \
} \
const_stack[const_stack_top] = _x; \
in_consts = 1; \
} while(0)

#define CONST_STACK_RESET() do { \
const_stack_top = -1; \
} while(0)

#define CONST_STACK_LASTN(i) \
&const_stack[CONST_STACK_LEN() - i]

#define CONST_STACK_POP(i) do { \
assert(CONST_STACK_LEN() >= i); \
const_stack_top -= i; \
} while(0)

/* Scans back N consecutive LOAD_CONST instructions, skipping NOPs,
returns index of the Nth last's LOAD_CONST's EXTENDED_ARG prefix.
Callers are responsible to check CONST_STACK_LEN beforehand.
Expand All @@ -88,8 +43,7 @@ lastn_const_start(const _Py_CODEUNIT *codestr, Py_ssize_t i, Py_ssize_t n)
}
}
else {
assert(_Py_OPCODE(codestr[i]) == NOP ||
_Py_OPCODE(codestr[i]) == EXTENDED_ARG);
assert(_Py_OPCODE(codestr[i]) == EXTENDED_ARG);
}
}
}
Expand Down Expand Up @@ -172,39 +126,40 @@ copy_op_arg(_Py_CODEUNIT *codestr, Py_ssize_t i, unsigned char op,
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 Py_ssize_t
fold_tuple_on_constants(_Py_CODEUNIT *codestr, Py_ssize_t c_start,
Py_ssize_t opcode_end, unsigned char opcode,
PyObject *consts, PyObject **objs, int n)
Py_ssize_t opcode_end, PyObject *consts, int n)
{
PyObject *newconst, *constant;
Py_ssize_t i, len_consts;

/* Pre-conditions */
assert(PyList_CheckExact(consts));

/* Buildup new tuple of constants */
newconst = PyTuple_New(n);
PyObject *newconst = PyTuple_New(n);
if (newconst == NULL) {
return -1;
}
for (i=0 ; i<n ; i++) {
constant = objs[i];

for (Py_ssize_t i = 0, pos = c_start; i < n; i++, pos++) {
assert(pos < opcode_end);
pos = find_op(codestr, pos);
assert(_Py_OPCODE(codestr[pos]) == LOAD_CONST);

unsigned int arg = get_arg(codestr, pos);
PyObject *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 -1;
}
Py_DECREF(newconst);

return copy_op_arg(codestr, c_start, LOAD_CONST, len_consts, opcode_end);
return copy_op_arg(codestr, c_start, LOAD_CONST,
PyList_GET_SIZE(consts)-1, opcode_end);
}

static unsigned int *
Expand Down Expand Up @@ -274,10 +229,8 @@ PyCode_Optimize(PyObject *code, PyObject* consts, PyObject *names,
unsigned char *lnotab;
unsigned int cum_orig_offset, last_offset;
Py_ssize_t tabsiz;
PyObject **const_stack = NULL;
Py_ssize_t const_stack_top = -1;
Py_ssize_t const_stack_size = 0;
int in_consts = 0; /* whether we are in a LOAD_CONST sequence */
// Count runs of consecutive LOAD_CONSTs
unsigned int cumlc = 0, lastlc = 0;
unsigned int *blocks = NULL;

/* Bail out if an exception is set */
Expand Down Expand Up @@ -314,8 +267,6 @@ PyCode_Optimize(PyObject *code, PyObject* consts, PyObject *names,
goto exitError;
assert(PyList_Check(consts));

CONST_STACK_CREATE();

for (i=find_op(codestr, 0) ; i<codelen ; i=nexti) {
opcode = _Py_OPCODE(codestr[i]);
op_start = i;
Expand All @@ -328,23 +279,21 @@ PyCode_Optimize(PyObject *code, PyObject* consts, PyObject *names,
nexti++;
nextop = nexti < codelen ? _Py_OPCODE(codestr[nexti]) : 0;

if (!in_consts) {
CONST_STACK_RESET();
}
in_consts = 0;
lastlc = cumlc;
cumlc = 0;

switch (opcode) {
/* Skip over LOAD_CONST trueconst
POP_JUMP_IF_FALSE xx. This improves
"while 1" performance. */
case LOAD_CONST:
CONST_STACK_PUSH_OP(i);
cumlc = lastlc + 1;
if (nextop != POP_JUMP_IF_FALSE ||
!ISBASICBLOCK(blocks, op_start, i + 1) ||
!PyObject_IsTrue(PyList_GET_ITEM(consts, get_arg(codestr, i))))
break;
fill_nops(codestr, op_start, nexti + 1);
CONST_STACK_POP(1);
cumlc = 0;
break;

/* Try to fold tuples of constants.
Expand All @@ -353,15 +302,10 @@ PyCode_Optimize(PyObject *code, PyObject* consts, PyObject *names,
Replace BUILD_SEQN 3 UNPACK_SEQN 3 with ROT3 ROT2. */
case BUILD_TUPLE:
j = get_arg(codestr, i);
if (j > 0 && CONST_STACK_LEN() >= j) {
if (j > 0 && lastlc >= j) {
h = lastn_const_start(codestr, op_start, j);
if (ISBASICBLOCK(blocks, h, op_start)) {
h = fold_tuple_on_constants(codestr, h, i + 1, opcode,
consts, CONST_STACK_LASTN(j), j);
if (h >= 0) {
CONST_STACK_POP(j);
CONST_STACK_PUSH_OP(h);
}
h = fold_tuple_on_constants(codestr, h, i+1, consts, j);
break;
}
}
Expand All @@ -374,12 +318,10 @@ PyCode_Optimize(PyObject *code, PyObject* consts, PyObject *names,
} else if (j == 2) {
codestr[op_start] = PACKOPARG(ROT_TWO, 0);
fill_nops(codestr, op_start + 1, nexti + 1);
CONST_STACK_RESET();
} else if (j == 3) {
codestr[op_start] = PACKOPARG(ROT_THREE, 0);
codestr[op_start + 1] = PACKOPARG(ROT_TWO, 0);
fill_nops(codestr, op_start + 2, nexti + 1);
CONST_STACK_RESET();
}
break;

Expand Down Expand Up @@ -538,7 +480,6 @@ PyCode_Optimize(PyObject *code, PyObject* consts, PyObject *names,
}
assert(h + (Py_ssize_t)nops == codelen);

CONST_STACK_DELETE();
PyMem_Free(blocks);
code = PyBytes_FromStringAndSize((char *)codestr, h * sizeof(_Py_CODEUNIT));
PyMem_Free(codestr);
Expand All @@ -549,7 +490,6 @@ PyCode_Optimize(PyObject *code, PyObject* consts, PyObject *names,

exitUnchanged:
Py_XINCREF(code);
CONST_STACK_DELETE();
PyMem_Free(blocks);
PyMem_Free(codestr);
return code;
Expand Down