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bpo-43950: optimize column table assembling with pre-sizing object (GH-26997)

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The new resizing system works like this;
```
$ cat t.py
a + a + a + b + c + a + a + a + b + c + a + a + a + b + c + a + a + a + b + c
[repeated 99 more times]
$ ./python t.py
RESIZE: prev len = 32, new len = 66
FINAL SIZE: 56
-----------------------------------------------------
RESIZE: prev len = 32, new len = 66
RESIZE: prev len = 66, new len = 134
RESIZE: prev len = 134, new len = 270
RESIZE: prev len = 270, new len = 542
RESIZE: prev len = 542, new len = 1086
RESIZE: prev len = 1086, new len = 2174
RESIZE: prev len = 2174, new len = 4350
RESIZE: prev len = 4350, new len = 8702
FINAL SIZE: 8004
```

So now we do considerably lower number of `_PyBytes_Resize` calls.

Automerge-Triggered-By: GH:isidentical
This commit is contained in:
Batuhan Taskaya 2021-07-02 22:03:58 +03:00 • committed by GitHub
parent 2560c612c8
commit ec8759b060
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GPG key ID: 4AEE18F83AFDEB23
1 changed files with 13 additions and 6 deletions
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19
Python/compile.c
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@ -40,7 +40,7 @@
#define DEFAULT_BLOCKS 8
#define DEFAULT_CODE_SIZE 128
#define DEFAULT_LNOTAB_SIZE 16
#define DEFAULT_CNOTAB_SIZE 0
#define DEFAULT_CNOTAB_SIZE 32
#define COMP_GENEXP 0
#define COMP_LISTCOMP 1
@ -6587,6 +6587,7 @@ struct assembler {
PyObject* a_cnotab; /* bytes containing cnotab */
int a_lnotab_off; /* offset into lnotab */
int a_enotab_off; /* offset into enotab */
int a_cnotab_off; /* offset into cnotab */
PyObject *a_except_table; /* bytes containing exception table */
int a_except_table_off; /* offset into exception table */
int a_prevlineno; /* lineno of last emitted line in line table */
@ -6696,6 +6697,7 @@ assemble_init(struct assembler *a, int nblocks, int firstlineno)
a->a_lnotab = NULL;
a->a_enotab = NULL;
a->a_cnotab = NULL;
a->a_cnotab_off = 0;
a->a_except_table = NULL;
a->a_bytecode = PyBytes_FromStringAndSize(NULL, DEFAULT_CODE_SIZE);
if (a->a_bytecode == NULL) {
@ -7106,14 +7108,16 @@ static int
assemble_cnotab(struct assembler* a, struct instr* i, int instr_size)
{
Py_ssize_t len = PyBytes_GET_SIZE(a->a_cnotab);
// TODO: Allocate more memory than just what we immediately need
// like a_lnotab does.
if (_PyBytes_Resize(&a->a_cnotab, len + (instr_size * 2)) < 0) {
return 0;
int difference = instr_size * 2;
if (a->a_cnotab_off + difference >= len) {
if (_PyBytes_Resize(&a->a_cnotab, difference + (len * 2)) < 0) {
return 0;
}
}
unsigned char* cnotab = (unsigned char*)PyBytes_AS_STRING(a->a_cnotab);
cnotab += len;
cnotab += a->a_cnotab_off;
a->a_cnotab_off += difference;
for (int j = 0; j < instr_size; j++) {
if (i->i_col_offset > 255 || i->i_end_col_offset > 255) {
@ -7855,6 +7859,9 @@ assemble(struct compiler *c, int addNone)
if (!merge_const_one(c, &a.a_enotab)) {
goto error;
}
if (_PyBytes_Resize(&a.a_cnotab, a.a_cnotab_off) < 0) {
goto error;
}
if (_PyBytes_Resize(&a.a_bytecode, a.a_offset * sizeof(_Py_CODEUNIT)) < 0) {
goto error;
}