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gh-126835: make CFG optimizer skip over NOP's when looking for const sequence construction #129703

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Merged
Eclips4 merged 12 commits into from
Feb 9, 2025
Merged

gh-126835: make CFG optimizer skip over NOP's when looking for const sequence construction #129703

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20e61ee
Make `is_constant_sequence` NOP aware
Feb 5, 2025
8b6d294
implement `get_constant_sequence`
Feb 6, 2025
0845cd7
disable debugging code
Feb 6, 2025
d3768ac
address review
Feb 6, 2025
96ff172
address review
Feb 8, 2025
ed7431d
add tests
Feb 8, 2025
f539224
disable debug code
Feb 8, 2025
5866faa
update tests
Feb 8, 2025
578d66b
update tests
Feb 8, 2025
cd92614
update tests
Feb 9, 2025
1574122
Update Lib/test/test_peepholer.py
Feb 9, 2025
16c66f9
Update Lib/test/test_peepholer.py
Feb 9, 2025
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address review
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@WolframAlph
WolframAlph committed Feb 8, 2025
commit d3768ac8d267fcd751a3a53a0fe6e751e69f3dc5
33 changes: 14 additions & 19 deletions Python/flowgraph.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1339,12 +1339,12 @@ add_const(PyObject *newconst, PyObject *consts, PyObject *const_cache)
}

/*
Walk basic block upwards starting from "start" trying to collect "size" number of
Walk basic block backwards starting from "start" trying to collect "size" number of
subsequent constants from instructions loading constants into new tuple ignoring NOP's in between.

Returns -1 on error and sets "seq" to NULL.
Returns 0 on success and sets "seq" to NULL if failed to collect requested number of constants.
Returns 0 on success and sets "seq" to resulting tuple if succeeded to collect requested number of constants.
Returns ERROR on error and sets "seq" to NULL.
Returns SUCCESS on success and sets "seq" to NULL if failed to collect requested number of constants.
Returns SUCCESS on success and sets "seq" to resulting tuple if succeeded to collect requested number of constants.
*/
static int
get_constant_sequence(basicblock *bb, int start, int size,
Expand All @@ -1354,7 +1354,7 @@ get_constant_sequence(basicblock *bb, int start, int size,
*seq = NULL;
PyObject *res = PyTuple_New((Py_ssize_t)size);
if (res == NULL) {
return -1;
return ERROR;
}
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for (; start >= 0 && size > 0; start--) {
cfg_instr *instr = &bb->b_instr[start];
Expand All @@ -1367,7 +1367,7 @@ get_constant_sequence(basicblock *bb, int start, int size,
PyObject *constant = get_const_value(instr->i_opcode, instr->i_oparg, consts);
if (constant == NULL) {
Py_DECREF(res);
return -1;
return ERROR;
}
PyTuple_SET_ITEM(res, --size, constant);
}
Expand All @@ -1377,15 +1377,14 @@ get_constant_sequence(basicblock *bb, int start, int size,
else {
*seq = res;
}
return 0;
return SUCCESS;
}

/*
Walk basic block upwards starting from "start" and change "count" number of
non-NOP instructions to NOP's, returning index of first instruction before
last placed NOP. Returns -1 if last placed NOP was first instruction in the block.
Walk basic block backwards starting from "start" and change "count" number of
non-NOP instructions to NOP's.
*/
static int
static void
nop_out(basicblock *bb, int start, int count)
{
assert(start < bb->b_iused);
Expand All @@ -1398,7 +1397,6 @@ nop_out(basicblock *bb, int start, int count)
count--;
}
assert(start >= -1);
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Outdated
return start;
}

/* Replace LOAD_CONST c1, LOAD_CONST c2 ... LOAD_CONST cn, BUILD_TUPLE n
Expand All @@ -1425,7 +1423,7 @@ fold_tuple_of_constants(basicblock *bb, int n, PyObject *consts, PyObject *const
int index = add_const(newconst, consts, const_cache);
RETURN_IF_ERROR(index);
INSTR_SET_OP1(&bb->b_instr[n], LOAD_CONST, index);
(void)nop_out(bb, n-1, seq_size);
nop_out(bb, n-1, seq_size);
return SUCCESS;
}

Expand Down Expand Up @@ -1465,16 +1463,13 @@ optimize_if_const_list_or_set(basicblock *bb, int n, PyObject *consts, PyObject
RETURN_IF_ERROR(index);
INSTR_SET_OP1(&bb->b_instr[n], extend, 1);
INSTR_SET_OP1(&bb->b_instr[n-1], LOAD_CONST, index);
int i = nop_out(bb, n-2, seq_size-2);
for (; i > 0 && bb->b_instr[i].i_opcode == NOP; i--);
assert(i >= 0);
assert(loads_const(bb->b_instr[i].i_opcode));
INSTR_SET_OP1(&bb->b_instr[i], build, 0);
INSTR_SET_OP1(&bb->b_instr[n-2], build, 0);
nop_out(bb, n-3, seq_size-2);
return SUCCESS;
}

/*
Walk basic block upwards starting from "start" to collect instruction pair
Walk basic block backwards starting from "start" to collect instruction pair
that loads consts skipping NOP's in between.
*/
static bool
Expand Down