Skip to content
Navigation Menu
{{ message }}
forked from python/cpython
-
Notifications
You must be signed in to change notification settings - Fork 0
Expand file tree
/
Copy pathpeephole.c
More file actions
534 lines (485 loc) · 18.9 KB
/
Copy pathpeephole.c
File metadata and controls
534 lines (485 loc) · 18.9 KB
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
/* Peephole optimizations for bytecode compiler. */
#include "Python.h"
#include "Python-ast.h"
#include "node.h"
#include "ast.h"
#include "code.h"
#include "symtable.h"
#include "opcode.h"
#include "wordcode_helpers.h"
#define UNCONDITIONAL_JUMP(op) (op==JUMP_ABSOLUTE || op==JUMP_FORWARD)
#define CONDITIONAL_JUMP(op) (op==POP_JUMP_IF_FALSE || op==POP_JUMP_IF_TRUE \
|| op==JUMP_IF_FALSE_OR_POP || op==JUMP_IF_TRUE_OR_POP || op==JUMP_IF_NOT_EXC_MATCH)
#define ABSOLUTE_JUMP(op) (op==JUMP_ABSOLUTE \
|| op==POP_JUMP_IF_FALSE || op==POP_JUMP_IF_TRUE \
|| op==JUMP_IF_FALSE_OR_POP || op==JUMP_IF_TRUE_OR_POP || op==JUMP_IF_NOT_EXC_MATCH)
#define JUMPS_ON_TRUE(op) (op==POP_JUMP_IF_TRUE || op==JUMP_IF_TRUE_OR_POP)
#define GETJUMPTGT(arr, i) (get_arg(arr, i) / sizeof(_Py_CODEUNIT) + \
(ABSOLUTE_JUMP(_Py_OPCODE(arr[i])) ? 0 : i+1))
#define ISBASICBLOCK(blocks, start, end) \
(blocks[start]==blocks[end])
/* 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.
*/
static Py_ssize_t
lastn_const_start(const _Py_CODEUNIT *codestr, Py_ssize_t i, Py_ssize_t n)
{
assert(n > 0);
for (;;) {
i--;
assert(i >= 0);
if (_Py_OPCODE(codestr[i]) == LOAD_CONST) {
if (!--n) {
while (i > 0 && _Py_OPCODE(codestr[i-1]) == EXTENDED_ARG) {
i--;
}
return i;
}
}
else {
assert(_Py_OPCODE(codestr[i]) == EXTENDED_ARG);
}
}
}
/* Scans through EXTENDED ARGs, seeking the index of the effective opcode */
static Py_ssize_t
find_op(const _Py_CODEUNIT *codestr, Py_ssize_t codelen, Py_ssize_t i)
{
while (i < codelen && _Py_OPCODE(codestr[i]) == EXTENDED_ARG) {
i++;
}
return i;
}
/* Given the index of the effective opcode,
scan back to construct the oparg with EXTENDED_ARG */
static unsigned int
get_arg(const _Py_CODEUNIT *codestr, Py_ssize_t i)
{
_Py_CODEUNIT word;
unsigned int oparg = _Py_OPARG(codestr[i]);
if (i >= 1 && _Py_OPCODE(word = codestr[i-1]) == EXTENDED_ARG) {
oparg |= _Py_OPARG(word) << 8;
if (i >= 2 && _Py_OPCODE(word = codestr[i-2]) == EXTENDED_ARG) {
oparg |= _Py_OPARG(word) << 16;
if (i >= 3 && _Py_OPCODE(word = codestr[i-3]) == EXTENDED_ARG) {
oparg |= _Py_OPARG(word) << 24;
}
}
}
return oparg;
}
/* Fill the region with NOPs. */
static void
fill_nops(_Py_CODEUNIT *codestr, Py_ssize_t start, Py_ssize_t end)
{
memset(codestr + start, NOP, (end - start) * sizeof(_Py_CODEUNIT));
}
/* Given the index of the effective opcode,
attempt to replace the argument, taking into account EXTENDED_ARG.
Returns -1 on failure, or the new op index on success */
static Py_ssize_t
set_arg(_Py_CODEUNIT *codestr, Py_ssize_t i, unsigned int oparg)
{
unsigned int curarg = get_arg(codestr, i);
int curilen, newilen;
if (curarg == oparg)
return i;
curilen = instrsize(curarg);
newilen = instrsize(oparg);
if (curilen < newilen) {
return -1;
}
write_op_arg(codestr + i + 1 - curilen, _Py_OPCODE(codestr[i]), oparg, newilen);
fill_nops(codestr, i + 1 - curilen + newilen, i + 1);
return i-curilen+newilen;
}
/* Attempt to write op/arg at end of specified region of memory.
Preceding memory in the region is overwritten with NOPs.
Returns -1 on failure, op index on success */
static Py_ssize_t
copy_op_arg(_Py_CODEUNIT *codestr, Py_ssize_t i, unsigned char op,
unsigned int oparg, Py_ssize_t maxi)
{
int ilen = instrsize(oparg);
if (i + ilen > maxi) {
return -1;
}
write_op_arg(codestr + maxi - ilen, op, oparg, ilen);
fill_nops(codestr, i, maxi - ilen);
return maxi - 1;
}
/* Replace LOAD_CONST c1, LOAD_CONST c2 ... LOAD_CONST cn, BUILD_TUPLE n
with LOAD_CONST (c1, c2, ... cn).
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.
*/
static Py_ssize_t
fold_tuple_on_constants(_Py_CODEUNIT *codestr, Py_ssize_t codelen,
Py_ssize_t c_start, Py_ssize_t opcode_end,
PyObject *consts, int n)
{
/* Pre-conditions */
assert(PyList_CheckExact(consts));
/* Buildup new tuple of constants */
PyObject *newconst = PyTuple_New(n);
if (newconst == NULL) {
return -1;
}
for (Py_ssize_t i = 0, pos = c_start; i < n; i++, pos++) {
assert(pos < opcode_end);
pos = find_op(codestr, codelen, 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);
}
Py_ssize_t index = PyList_GET_SIZE(consts);
#if SIZEOF_SIZE_T > SIZEOF_INT
if ((size_t)index >= UINT_MAX - 1) {
Py_DECREF(newconst);
PyErr_SetString(PyExc_OverflowError, "too many constants");
return -1;
}
#endif
/* Append folded constant onto consts */
if (PyList_Append(consts, newconst)) {
Py_DECREF(newconst);
return -1;
}
Py_DECREF(newconst);
return copy_op_arg(codestr, c_start, LOAD_CONST,
(unsigned int)index, opcode_end);
}
static unsigned int *
markblocks(_Py_CODEUNIT *code, Py_ssize_t len)
{
unsigned int *blocks = PyMem_New(unsigned int, len);
int i, j, opcode, blockcnt = 0;
if (blocks == NULL) {
PyErr_NoMemory();
return NULL;
}
memset(blocks, 0, len*sizeof(int));
/* Mark labels in the first pass */
for (i = 0; i < len; i++) {
opcode = _Py_OPCODE(code[i]);
switch (opcode) {
case FOR_ITER:
case JUMP_FORWARD:
case JUMP_IF_FALSE_OR_POP:
case JUMP_IF_TRUE_OR_POP:
case POP_JUMP_IF_FALSE:
case POP_JUMP_IF_TRUE:
case JUMP_IF_NOT_EXC_MATCH:
case JUMP_ABSOLUTE:
case SETUP_FINALLY:
case SETUP_WITH:
case SETUP_ASYNC_WITH:
j = GETJUMPTGT(code, i);
assert(j < len);
blocks[j] = 1;
break;
}
}
/* Build block numbers in the second pass */
for (i = 0; i < len; i++) {
blockcnt += blocks[i]; /* increment blockcnt over labels */
blocks[i] = blockcnt;
}
return blocks;
}
/* Perform basic peephole optimizations to components of a code object.
The consts object should still be in list form to allow new constants
to be appended.
To keep the optimizer simple, it bails when the lineno table has complex
encoding for gaps >= 255.
Optimizations are restricted to simple transformations occurring within a
single basic block. All transformations keep the code size the same or
smaller. For those that reduce size, the gaps are initially filled with
NOPs. Later those NOPs are removed and the jump addresses retargeted in
a single pass. */
PyObject *
PyCode_Optimize(PyObject *code, PyObject* consts, PyObject *names,
PyObject *lnotab_obj)
{
Py_ssize_t h, i, nexti, op_start, tgt;
unsigned int j, nops;
unsigned char opcode, nextop;
_Py_CODEUNIT *codestr = NULL;
unsigned char *lnotab;
unsigned int cum_orig_offset, last_offset;
Py_ssize_t tabsiz;
// Count runs of consecutive LOAD_CONSTs
unsigned int cumlc = 0, lastlc = 0;
unsigned int *blocks = NULL;
/* Bail out if an exception is set */
if (PyErr_Occurred())
goto exitError;
/* Bypass optimization when the lnotab table is too complex */
assert(PyBytes_Check(lnotab_obj));
lnotab = (unsigned char*)PyBytes_AS_STRING(lnotab_obj);
tabsiz = PyBytes_GET_SIZE(lnotab_obj);
assert(tabsiz == 0 || Py_REFCNT(lnotab_obj) == 1);
/* Don't optimize if lnotab contains instruction pointer delta larger
than +255 (encoded as multiple bytes), just to keep the peephole optimizer
simple. The optimizer leaves line number deltas unchanged. */
for (i = 0; i < tabsiz; i += 2) {
if (lnotab[i] == 255) {
goto exitUnchanged;
}
}
assert(PyBytes_Check(code));
Py_ssize_t codesize = PyBytes_GET_SIZE(code);
assert(codesize % sizeof(_Py_CODEUNIT) == 0);
Py_ssize_t codelen = codesize / sizeof(_Py_CODEUNIT);
if (codelen > INT_MAX) {
/* Python assembler is limited to INT_MAX: see assembler.a_offset in
compile.c. */
goto exitUnchanged;
}
/* Make a modifiable copy of the code string */
codestr = (_Py_CODEUNIT *)PyMem_Malloc(codesize);
if (codestr == NULL) {
PyErr_NoMemory();
goto exitError;
}
memcpy(codestr, PyBytes_AS_STRING(code), codesize);
blocks = markblocks(codestr, codelen);
if (blocks == NULL)
goto exitError;
assert(PyList_Check(consts));
for (i=find_op(codestr, codelen, 0) ; i<codelen ; i=nexti) {
opcode = _Py_OPCODE(codestr[i]);
op_start = i;
while (op_start >= 1 && _Py_OPCODE(codestr[op_start-1]) == EXTENDED_ARG) {
op_start--;
}
nexti = i + 1;
while (nexti < codelen && _Py_OPCODE(codestr[nexti]) == EXTENDED_ARG)
nexti++;
nextop = nexti < codelen ? _Py_OPCODE(codestr[nexti]) : 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:
cumlc = lastlc + 1;
if (nextop != POP_JUMP_IF_FALSE ||
!ISBASICBLOCK(blocks, op_start, i + 1)) {
break;
}
PyObject* cnt = PyList_GET_ITEM(consts, get_arg(codestr, i));
int is_true = PyObject_IsTrue(cnt);
if (is_true == -1) {
goto exitError;
}
if (is_true == 1) {
fill_nops(codestr, op_start, nexti + 1);
cumlc = 0;
}
break;
/* Try to fold tuples of constants.
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:
j = get_arg(codestr, i);
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, codelen,
h, i+1, consts, j);
break;
}
}
if (nextop != UNPACK_SEQUENCE ||
!ISBASICBLOCK(blocks, op_start, i + 1) ||
j != get_arg(codestr, nexti))
break;
if (j < 2) {
fill_nops(codestr, op_start, nexti + 1);
} else if (j == 2) {
codestr[op_start] = PACKOPARG(ROT_TWO, 0);
fill_nops(codestr, op_start + 1, nexti + 1);
} 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);
}
break;
/* Simplify conditional jump to conditional jump where the
result of the first test implies the success of a similar
test or the failure of the opposite test.
Arises in code like:
"a and b or c"
"(a and b) and c"
"(a or b) or c"
"(a or b) and c"
x:JUMP_IF_FALSE_OR_POP y y:JUMP_IF_FALSE_OR_POP z
--> x:JUMP_IF_FALSE_OR_POP z
x:JUMP_IF_FALSE_OR_POP y y:JUMP_IF_TRUE_OR_POP z
--> x:POP_JUMP_IF_FALSE y+1
where y+1 is the instruction following the second test.
*/
case JUMP_IF_FALSE_OR_POP:
case JUMP_IF_TRUE_OR_POP:
h = get_arg(codestr, i) / sizeof(_Py_CODEUNIT);
tgt = find_op(codestr, codelen, h);
j = _Py_OPCODE(codestr[tgt]);
if (CONDITIONAL_JUMP(j)) {
/* NOTE: all possible jumps here are absolute. */
if (JUMPS_ON_TRUE(j) == JUMPS_ON_TRUE(opcode)) {
/* The second jump will be taken iff the first is.
The current opcode inherits its target's
stack effect */
h = set_arg(codestr, i, get_arg(codestr, tgt));
} else {
/* The second jump is not taken if the first is (so
jump past it), and all conditional jumps pop their
argument when they're not taken (so change the
first jump to pop its argument when it's taken). */
Py_ssize_t arg = (tgt + 1);
/* cannot overflow: codelen <= INT_MAX */
assert((size_t)arg <= UINT_MAX / sizeof(_Py_CODEUNIT));
arg *= sizeof(_Py_CODEUNIT);
h = set_arg(codestr, i, (unsigned int)arg);
j = opcode == JUMP_IF_TRUE_OR_POP ?
POP_JUMP_IF_TRUE : POP_JUMP_IF_FALSE;
}
if (h >= 0) {
nexti = h;
codestr[nexti] = PACKOPARG(j, _Py_OPARG(codestr[nexti]));
break;
}
}
/* Intentional fallthrough */
/* Replace jumps to unconditional jumps */
case POP_JUMP_IF_FALSE:
case POP_JUMP_IF_TRUE:
case JUMP_FORWARD:
case JUMP_ABSOLUTE:
h = GETJUMPTGT(codestr, i);
tgt = find_op(codestr, codelen, h);
/* Replace JUMP_* to a RETURN into just a RETURN */
if (UNCONDITIONAL_JUMP(opcode) &&
_Py_OPCODE(codestr[tgt]) == RETURN_VALUE) {
codestr[op_start] = PACKOPARG(RETURN_VALUE, 0);
fill_nops(codestr, op_start + 1, i + 1);
} else if (UNCONDITIONAL_JUMP(_Py_OPCODE(codestr[tgt]))) {
size_t arg = GETJUMPTGT(codestr, tgt);
if (opcode == JUMP_FORWARD) { /* JMP_ABS can go backwards */
opcode = JUMP_ABSOLUTE;
} else if (!ABSOLUTE_JUMP(opcode)) {
if (arg < (size_t)(i + 1)) {
break; /* No backward relative jumps */
}
arg -= i + 1; /* Calc relative jump addr */
}
/* cannot overflow: codelen <= INT_MAX */
assert(arg <= (UINT_MAX / sizeof(_Py_CODEUNIT)));
arg *= sizeof(_Py_CODEUNIT);
copy_op_arg(codestr, op_start, opcode,
(unsigned int)arg, i + 1);
}
break;
/* Remove unreachable ops after RETURN */
case RETURN_VALUE:
h = i + 1;
while (h < codelen && ISBASICBLOCK(blocks, i, h))
{
/* Leave SETUP_FINALLY and RERAISE in place to help find block limits. */
if (_Py_OPCODE(codestr[h]) == SETUP_FINALLY || _Py_OPCODE(codestr[h]) == RERAISE) {
while (h > i + 1 &&
_Py_OPCODE(codestr[h - 1]) == EXTENDED_ARG)
{
h--;
}
break;
}
h++;
}
if (h > i + 1) {
fill_nops(codestr, i + 1, h);
nexti = find_op(codestr, codelen, h);
}
break;
}
}
/* Fixup lnotab */
for (i = 0, nops = 0; i < codelen; i++) {
size_t block = (size_t)i - nops;
/* cannot overflow: codelen <= INT_MAX */
assert(block <= UINT_MAX);
/* original code offset => new code offset */
blocks[i] = (unsigned int)block;
if (_Py_OPCODE(codestr[i]) == NOP) {
nops++;
}
}
cum_orig_offset = 0;
last_offset = 0;
for (i=0 ; i < tabsiz ; i+=2) {
unsigned int offset_delta, new_offset;
cum_orig_offset += lnotab[i];
assert(cum_orig_offset % sizeof(_Py_CODEUNIT) == 0);
new_offset = blocks[cum_orig_offset / sizeof(_Py_CODEUNIT)] *
sizeof(_Py_CODEUNIT);
offset_delta = new_offset - last_offset;
assert(offset_delta <= 255);
lnotab[i] = (unsigned char)offset_delta;
last_offset = new_offset;
}
/* Remove NOPs and fixup jump targets */
for (op_start = i = h = 0; i < codelen; i++, op_start = i) {
j = _Py_OPARG(codestr[i]);
while (_Py_OPCODE(codestr[i]) == EXTENDED_ARG) {
i++;
j = j<<8 | _Py_OPARG(codestr[i]);
}
opcode = _Py_OPCODE(codestr[i]);
switch (opcode) {
case NOP:continue;
case JUMP_ABSOLUTE:
case POP_JUMP_IF_FALSE:
case POP_JUMP_IF_TRUE:
case JUMP_IF_FALSE_OR_POP:
case JUMP_IF_TRUE_OR_POP:
case JUMP_IF_NOT_EXC_MATCH:
j = blocks[j / sizeof(_Py_CODEUNIT)] * sizeof(_Py_CODEUNIT);
break;
case FOR_ITER:
case JUMP_FORWARD:
case SETUP_FINALLY:
case SETUP_WITH:
case SETUP_ASYNC_WITH:
j = blocks[j / sizeof(_Py_CODEUNIT) + i + 1] - blocks[i] - 1;
j *= sizeof(_Py_CODEUNIT);
break;
}
Py_ssize_t ilen = i - op_start + 1;
if (instrsize(j) > ilen) {
goto exitUnchanged;
}
assert(ilen <= INT_MAX);
/* If instrsize(j) < ilen, we'll emit EXTENDED_ARG 0 */
write_op_arg(codestr + h, opcode, j, (int)ilen);
h += ilen;
}
assert(h + (Py_ssize_t)nops == codelen);
PyMem_Free(blocks);
code = PyBytes_FromStringAndSize((char *)codestr, h * sizeof(_Py_CODEUNIT));
PyMem_Free(codestr);
return code;
exitError:
code = NULL;
exitUnchanged:
Py_XINCREF(code);
PyMem_Free(blocks);
PyMem_Free(codestr);
return code;
}
You can’t perform that action at this time.