[Python-checkins] bpo-42615: Delete redundant jump instructions that only bypass empty blocks (GH-23733)
markshannon
webhook-mailer at python.org
Wed Dec 16 07:18:26 EST 2020
https://github.com/python/cpython/commit/c71581c7a4192e6ba9a79eccc583aaadab300efa
commit: c71581c7a4192e6ba9a79eccc583aaadab300efa
branch: master
author: Om G <34579088+OmG-117 at users.noreply.github.com>
committer: markshannon <mark at hotpy.org>
date: 2020-12-16T12:18:05Z
summary:
bpo-42615: Delete redundant jump instructions that only bypass empty blocks (GH-23733)
* Delete jump instructions that bypass empty blocks
* Add news entry
* Explicitly check for unconditional jump opcodes
Using the is_jump function results in the inclusion of instructions like
returns for which this optimization is not really valid. So, instead
explicitly check that the instruction is an unconditional jump.
* Handle conditional jumps, delete jumps gracefully
* Ensure b_nofallthrough and b_reachable are valid
* Add test for redundant jumps
* Regenerate importlib.h and edit Misc/ACKS
* Fix bad whitespace
files:
A Misc/NEWS.d/next/Core and Builtins/2020-12-10-17-06-52.bpo-42615.Je6Q-r.rst
M Lib/test/test_compile.py
M Misc/ACKS
M Python/compile.c
M Python/importlib.h
diff --git a/Lib/test/test_compile.py b/Lib/test/test_compile.py
index 3a37b6cf30bfc..3e826b9accfb1 100644
--- a/Lib/test/test_compile.py
+++ b/Lib/test/test_compile.py
@@ -837,6 +837,34 @@ def test_big_dict_literal(self):
the_dict = "{" + ",".join(f"{x}:{x}" for x in range(dict_size)) + "}"
self.assertEqual(len(eval(the_dict)), dict_size)
+ def test_redundant_jump_in_if_else_break(self):
+ # Check if bytecode containing jumps that simply point to the next line
+ # is generated around if-else-break style structures. See bpo-42615.
+
+ def if_else_break():
+ val = 1
+ while True:
+ if val > 0:
+ val -= 1
+ else:
+ break
+ val = -1
+
+ INSTR_SIZE = 2
+ HANDLED_JUMPS = (
+ 'POP_JUMP_IF_FALSE',
+ 'POP_JUMP_IF_TRUE',
+ 'JUMP_ABSOLUTE',
+ 'JUMP_FORWARD',
+ )
+
+ for line, instr in enumerate(dis.Bytecode(if_else_break)):
+ if instr.opname == 'JUMP_FORWARD':
+ self.assertNotEqual(instr.arg, 0)
+ elif instr.opname in HANDLED_JUMPS:
+ self.assertNotEqual(instr.arg, (line + 1)*INSTR_SIZE)
+
+
class TestExpressionStackSize(unittest.TestCase):
# These tests check that the computed stack size for a code object
# stays within reasonable bounds (see issue #21523 for an example
diff --git a/Misc/ACKS b/Misc/ACKS
index 253349017c5cd..134f4ea3be874 100644
--- a/Misc/ACKS
+++ b/Misc/ACKS
@@ -643,6 +643,7 @@ Grzegorz Grzywacz
Thomas Guettler
Yuyang Guo
Anuj Gupta
+Om Gupta
Michael Guravage
Lars Gustäbel
Thomas Güttler
diff --git a/Misc/NEWS.d/next/Core and Builtins/2020-12-10-17-06-52.bpo-42615.Je6Q-r.rst b/Misc/NEWS.d/next/Core and Builtins/2020-12-10-17-06-52.bpo-42615.Je6Q-r.rst
new file mode 100644
index 0000000000000..2d919a8192d5a
--- /dev/null
+++ b/Misc/NEWS.d/next/Core and Builtins/2020-12-10-17-06-52.bpo-42615.Je6Q-r.rst
@@ -0,0 +1,2 @@
+Remove jump commands made redundant by the deletion of unreachable bytecode
+blocks
diff --git a/Python/compile.c b/Python/compile.c
index ae92869fc9565..4792733fd5861 100644
--- a/Python/compile.c
+++ b/Python/compile.c
@@ -6437,8 +6437,50 @@ optimize_cfg(struct assembler *a, PyObject *consts)
for (basicblock *b = a->a_entry; b != NULL; b = b->b_next) {
if (b->b_reachable == 0) {
b->b_iused = 0;
+ b->b_nofallthrough = 0;
}
}
+ /* Delete jump instructions made redundant by previous step. If a non-empty
+ block ends with a jump instruction, check if the next non-empty block
+ reached through normal flow control is the target of that jump. If it
+ is, then the jump instruction is redundant and can be deleted.
+ */
+ for (basicblock *b = a->a_entry; b != NULL; b = b->b_next) {
+ if (b->b_iused > 0) {
+ struct instr *b_last_instr = &b->b_instr[b->b_iused - 1];
+ if (b_last_instr->i_opcode == POP_JUMP_IF_FALSE ||
+ b_last_instr->i_opcode == POP_JUMP_IF_TRUE ||
+ b_last_instr->i_opcode == JUMP_ABSOLUTE ||
+ b_last_instr->i_opcode == JUMP_FORWARD) {
+ basicblock *b_next_act = b->b_next;
+ while (b_next_act != NULL && b_next_act->b_iused == 0) {
+ b_next_act = b_next_act->b_next;
+ }
+ if (b_last_instr->i_target == b_next_act) {
+ b->b_nofallthrough = 0;
+ switch(b_last_instr->i_opcode) {
+ case POP_JUMP_IF_FALSE:
+ case POP_JUMP_IF_TRUE:
+ b_last_instr->i_opcode = POP_TOP;
+ b_last_instr->i_target = NULL;
+ b_last_instr->i_oparg = 0;
+ break;
+ case JUMP_ABSOLUTE:
+ case JUMP_FORWARD:
+ b_last_instr->i_opcode = NOP;
+ clean_basic_block(b);
+ break;
+ }
+ /* The blocks after this one are now reachable through it */
+ b_next_act = b->b_next;
+ while (b_next_act != NULL && b_next_act->b_iused == 0) {
+ b_next_act->b_reachable = 1;
+ b_next_act = b_next_act->b_next;
+ }
+ }
+ }
+ }
+ }
minimize_lineno_table(a);
return 0;
}
diff --git a/Python/importlib.h b/Python/importlib.h
index e05c8ea391474..f8def1b2b95e2 100644
--- a/Python/importlib.h
+++ b/Python/importlib.h
@@ -1749,107 +1749,107 @@ const unsigned char _Py_M__importlib_bootstrap[] = {
102,114,111,109,95,110,97,109,101,129,4,0,0,115,10,0,
0,0,10,1,8,1,12,1,8,1,255,128,114,231,0,0,
0,99,2,0,0,0,0,0,0,0,0,0,0,0,10,0,
- 0,0,5,0,0,0,67,0,0,0,115,164,0,0,0,124,
+ 0,0,5,0,0,0,67,0,0,0,115,162,0,0,0,124,
1,97,0,124,0,97,1,116,2,116,1,131,1,125,2,116,
- 1,106,3,160,4,161,0,68,0,93,70,92,2,125,3,125,
+ 1,106,3,160,4,161,0,68,0,93,68,92,2,125,3,125,
4,116,5,124,4,124,2,131,2,114,26,124,3,116,1,106,
- 6,118,0,114,60,116,7,125,5,110,16,116,0,160,8,124,
- 3,161,1,114,26,116,9,125,5,110,0,116,10,124,4,124,
- 5,131,2,125,6,116,11,124,6,124,4,131,2,1,0,113,
- 26,116,1,106,3,116,12,25,0,125,7,100,1,68,0,93,
- 46,125,8,124,8,116,1,106,3,118,1,114,136,116,13,124,
- 8,131,1,125,9,110,10,116,1,106,3,124,8,25,0,125,
- 9,116,14,124,7,124,8,124,9,131,3,1,0,113,112,100,
- 2,83,0,41,3,122,250,83,101,116,117,112,32,105,109,112,
- 111,114,116,108,105,98,32,98,121,32,105,109,112,111,114,116,
- 105,110,103,32,110,101,101,100,101,100,32,98,117,105,108,116,
- 45,105,110,32,109,111,100,117,108,101,115,32,97,110,100,32,
- 105,110,106,101,99,116,105,110,103,32,116,104,101,109,10,32,
- 32,32,32,105,110,116,111,32,116,104,101,32,103,108,111,98,
- 97,108,32,110,97,109,101,115,112,97,99,101,46,10,10,32,
- 32,32,32,65,115,32,115,121,115,32,105,115,32,110,101,101,
- 100,101,100,32,102,111,114,32,115,121,115,46,109,111,100,117,
- 108,101,115,32,97,99,99,101,115,115,32,97,110,100,32,95,
- 105,109,112,32,105,115,32,110,101,101,100,101,100,32,116,111,
- 32,108,111,97,100,32,98,117,105,108,116,45,105,110,10,32,
- 32,32,32,109,111,100,117,108,101,115,44,32,116,104,111,115,
- 101,32,116,119,111,32,109,111,100,117,108,101,115,32,109,117,
- 115,116,32,98,101,32,101,120,112,108,105,99,105,116,108,121,
- 32,112,97,115,115,101,100,32,105,110,46,10,10,32,32,32,
- 32,41,3,114,26,0,0,0,114,95,0,0,0,114,68,0,
- 0,0,78,41,15,114,61,0,0,0,114,18,0,0,0,114,
- 3,0,0,0,114,99,0,0,0,218,5,105,116,101,109,115,
- 114,203,0,0,0,114,82,0,0,0,114,169,0,0,0,114,
- 92,0,0,0,114,184,0,0,0,114,149,0,0,0,114,155,
- 0,0,0,114,9,0,0,0,114,231,0,0,0,114,12,0,
- 0,0,41,10,218,10,115,121,115,95,109,111,100,117,108,101,
- 218,11,95,105,109,112,95,109,111,100,117,108,101,90,11,109,
- 111,100,117,108,101,95,116,121,112,101,114,20,0,0,0,114,
- 104,0,0,0,114,116,0,0,0,114,103,0,0,0,90,11,
- 115,101,108,102,95,109,111,100,117,108,101,90,12,98,117,105,
- 108,116,105,110,95,110,97,109,101,90,14,98,117,105,108,116,
- 105,110,95,109,111,100,117,108,101,114,5,0,0,0,114,5,
- 0,0,0,114,6,0,0,0,218,6,95,115,101,116,117,112,
- 136,4,0,0,115,40,0,0,0,4,9,4,1,8,3,18,
- 1,10,1,10,1,6,1,10,1,6,1,10,3,10,1,2,
- 128,10,3,8,1,10,1,10,1,10,2,14,1,4,251,255,
- 128,114,235,0,0,0,99,2,0,0,0,0,0,0,0,0,
- 0,0,0,2,0,0,0,3,0,0,0,67,0,0,0,115,
- 38,0,0,0,116,0,124,0,124,1,131,2,1,0,116,1,
- 106,2,160,3,116,4,161,1,1,0,116,1,106,2,160,3,
- 116,5,161,1,1,0,100,1,83,0,41,2,122,48,73,110,
- 115,116,97,108,108,32,105,109,112,111,114,116,101,114,115,32,
- 102,111,114,32,98,117,105,108,116,105,110,32,97,110,100,32,
- 102,114,111,122,101,110,32,109,111,100,117,108,101,115,78,41,
- 6,114,235,0,0,0,114,18,0,0,0,114,201,0,0,0,
- 114,126,0,0,0,114,169,0,0,0,114,184,0,0,0,41,
- 2,114,233,0,0,0,114,234,0,0,0,114,5,0,0,0,
- 114,5,0,0,0,114,6,0,0,0,218,8,95,105,110,115,
- 116,97,108,108,171,4,0,0,115,8,0,0,0,10,2,12,
- 2,16,1,255,128,114,236,0,0,0,99,0,0,0,0,0,
- 0,0,0,0,0,0,0,1,0,0,0,4,0,0,0,67,
- 0,0,0,115,32,0,0,0,100,1,100,2,108,0,125,0,
- 124,0,97,1,124,0,160,2,116,3,106,4,116,5,25,0,
- 161,1,1,0,100,2,83,0,41,3,122,57,73,110,115,116,
- 97,108,108,32,105,109,112,111,114,116,101,114,115,32,116,104,
- 97,116,32,114,101,113,117,105,114,101,32,101,120,116,101,114,
- 110,97,108,32,102,105,108,101,115,121,115,116,101,109,32,97,
- 99,99,101,115,115,114,25,0,0,0,78,41,6,218,26,95,
- 102,114,111,122,101,110,95,105,109,112,111,114,116,108,105,98,
- 95,101,120,116,101,114,110,97,108,114,133,0,0,0,114,236,
- 0,0,0,114,18,0,0,0,114,99,0,0,0,114,9,0,
- 0,0,41,1,114,237,0,0,0,114,5,0,0,0,114,5,
- 0,0,0,114,6,0,0,0,218,27,95,105,110,115,116,97,
- 108,108,95,101,120,116,101,114,110,97,108,95,105,109,112,111,
- 114,116,101,114,115,179,4,0,0,115,8,0,0,0,8,3,
- 4,1,20,1,255,128,114,238,0,0,0,41,2,78,78,41,
- 1,78,41,2,78,114,25,0,0,0,41,4,78,78,114,5,
- 0,0,0,114,25,0,0,0,41,54,114,10,0,0,0,114,
- 7,0,0,0,114,26,0,0,0,114,95,0,0,0,114,68,
- 0,0,0,114,133,0,0,0,114,17,0,0,0,114,21,0,
- 0,0,114,63,0,0,0,114,37,0,0,0,114,47,0,0,
- 0,114,22,0,0,0,114,23,0,0,0,114,53,0,0,0,
- 114,54,0,0,0,114,57,0,0,0,114,69,0,0,0,114,
- 71,0,0,0,114,80,0,0,0,114,90,0,0,0,114,94,
- 0,0,0,114,105,0,0,0,114,118,0,0,0,114,119,0,
- 0,0,114,98,0,0,0,114,149,0,0,0,114,155,0,0,
- 0,114,159,0,0,0,114,114,0,0,0,114,100,0,0,0,
- 114,166,0,0,0,114,167,0,0,0,114,101,0,0,0,114,
- 169,0,0,0,114,184,0,0,0,114,189,0,0,0,114,198,
- 0,0,0,114,200,0,0,0,114,202,0,0,0,114,208,0,
- 0,0,90,15,95,69,82,82,95,77,83,71,95,80,82,69,
- 70,73,88,114,210,0,0,0,114,213,0,0,0,218,6,111,
- 98,106,101,99,116,114,214,0,0,0,114,215,0,0,0,114,
- 216,0,0,0,114,221,0,0,0,114,227,0,0,0,114,230,
- 0,0,0,114,231,0,0,0,114,235,0,0,0,114,236,0,
- 0,0,114,238,0,0,0,114,5,0,0,0,114,5,0,0,
- 0,114,5,0,0,0,114,6,0,0,0,218,8,60,109,111,
- 100,117,108,101,62,1,0,0,0,115,106,0,0,0,4,0,
- 8,22,4,9,4,1,4,1,4,3,8,3,8,8,4,8,
- 4,2,16,3,14,4,14,77,14,21,8,16,8,37,8,17,
- 14,11,8,8,8,11,8,12,8,19,14,36,16,101,10,26,
- 14,45,8,72,8,17,8,17,8,30,8,36,8,45,14,15,
- 14,75,14,80,8,13,8,9,10,9,8,47,4,16,8,1,
- 8,2,6,32,8,3,10,16,14,15,8,37,10,27,8,37,
- 8,7,8,35,12,8,255,128,
+ 6,118,0,114,60,116,7,125,5,110,14,116,0,160,8,124,
+ 3,161,1,114,26,116,9,125,5,116,10,124,4,124,5,131,
+ 2,125,6,116,11,124,6,124,4,131,2,1,0,113,26,116,
+ 1,106,3,116,12,25,0,125,7,100,1,68,0,93,46,125,
+ 8,124,8,116,1,106,3,118,1,114,134,116,13,124,8,131,
+ 1,125,9,110,10,116,1,106,3,124,8,25,0,125,9,116,
+ 14,124,7,124,8,124,9,131,3,1,0,113,110,100,2,83,
+ 0,41,3,122,250,83,101,116,117,112,32,105,109,112,111,114,
+ 116,108,105,98,32,98,121,32,105,109,112,111,114,116,105,110,
+ 103,32,110,101,101,100,101,100,32,98,117,105,108,116,45,105,
+ 110,32,109,111,100,117,108,101,115,32,97,110,100,32,105,110,
+ 106,101,99,116,105,110,103,32,116,104,101,109,10,32,32,32,
+ 32,105,110,116,111,32,116,104,101,32,103,108,111,98,97,108,
+ 32,110,97,109,101,115,112,97,99,101,46,10,10,32,32,32,
+ 32,65,115,32,115,121,115,32,105,115,32,110,101,101,100,101,
+ 100,32,102,111,114,32,115,121,115,46,109,111,100,117,108,101,
+ 115,32,97,99,99,101,115,115,32,97,110,100,32,95,105,109,
+ 112,32,105,115,32,110,101,101,100,101,100,32,116,111,32,108,
+ 111,97,100,32,98,117,105,108,116,45,105,110,10,32,32,32,
+ 32,109,111,100,117,108,101,115,44,32,116,104,111,115,101,32,
+ 116,119,111,32,109,111,100,117,108,101,115,32,109,117,115,116,
+ 32,98,101,32,101,120,112,108,105,99,105,116,108,121,32,112,
+ 97,115,115,101,100,32,105,110,46,10,10,32,32,32,32,41,
+ 3,114,26,0,0,0,114,95,0,0,0,114,68,0,0,0,
+ 78,41,15,114,61,0,0,0,114,18,0,0,0,114,3,0,
+ 0,0,114,99,0,0,0,218,5,105,116,101,109,115,114,203,
+ 0,0,0,114,82,0,0,0,114,169,0,0,0,114,92,0,
+ 0,0,114,184,0,0,0,114,149,0,0,0,114,155,0,0,
+ 0,114,9,0,0,0,114,231,0,0,0,114,12,0,0,0,
+ 41,10,218,10,115,121,115,95,109,111,100,117,108,101,218,11,
+ 95,105,109,112,95,109,111,100,117,108,101,90,11,109,111,100,
+ 117,108,101,95,116,121,112,101,114,20,0,0,0,114,104,0,
+ 0,0,114,116,0,0,0,114,103,0,0,0,90,11,115,101,
+ 108,102,95,109,111,100,117,108,101,90,12,98,117,105,108,116,
+ 105,110,95,110,97,109,101,90,14,98,117,105,108,116,105,110,
+ 95,109,111,100,117,108,101,114,5,0,0,0,114,5,0,0,
+ 0,114,6,0,0,0,218,6,95,115,101,116,117,112,136,4,
+ 0,0,115,40,0,0,0,4,9,4,1,8,3,18,1,10,
+ 1,10,1,6,1,10,1,4,1,10,3,10,1,2,128,10,
+ 3,8,1,10,1,10,1,10,2,14,1,4,251,255,128,114,
+ 235,0,0,0,99,2,0,0,0,0,0,0,0,0,0,0,
+ 0,2,0,0,0,3,0,0,0,67,0,0,0,115,38,0,
+ 0,0,116,0,124,0,124,1,131,2,1,0,116,1,106,2,
+ 160,3,116,4,161,1,1,0,116,1,106,2,160,3,116,5,
+ 161,1,1,0,100,1,83,0,41,2,122,48,73,110,115,116,
+ 97,108,108,32,105,109,112,111,114,116,101,114,115,32,102,111,
+ 114,32,98,117,105,108,116,105,110,32,97,110,100,32,102,114,
+ 111,122,101,110,32,109,111,100,117,108,101,115,78,41,6,114,
+ 235,0,0,0,114,18,0,0,0,114,201,0,0,0,114,126,
+ 0,0,0,114,169,0,0,0,114,184,0,0,0,41,2,114,
+ 233,0,0,0,114,234,0,0,0,114,5,0,0,0,114,5,
+ 0,0,0,114,6,0,0,0,218,8,95,105,110,115,116,97,
+ 108,108,171,4,0,0,115,8,0,0,0,10,2,12,2,16,
+ 1,255,128,114,236,0,0,0,99,0,0,0,0,0,0,0,
+ 0,0,0,0,0,1,0,0,0,4,0,0,0,67,0,0,
+ 0,115,32,0,0,0,100,1,100,2,108,0,125,0,124,0,
+ 97,1,124,0,160,2,116,3,106,4,116,5,25,0,161,1,
+ 1,0,100,2,83,0,41,3,122,57,73,110,115,116,97,108,
+ 108,32,105,109,112,111,114,116,101,114,115,32,116,104,97,116,
+ 32,114,101,113,117,105,114,101,32,101,120,116,101,114,110,97,
+ 108,32,102,105,108,101,115,121,115,116,101,109,32,97,99,99,
+ 101,115,115,114,25,0,0,0,78,41,6,218,26,95,102,114,
+ 111,122,101,110,95,105,109,112,111,114,116,108,105,98,95,101,
+ 120,116,101,114,110,97,108,114,133,0,0,0,114,236,0,0,
+ 0,114,18,0,0,0,114,99,0,0,0,114,9,0,0,0,
+ 41,1,114,237,0,0,0,114,5,0,0,0,114,5,0,0,
+ 0,114,6,0,0,0,218,27,95,105,110,115,116,97,108,108,
+ 95,101,120,116,101,114,110,97,108,95,105,109,112,111,114,116,
+ 101,114,115,179,4,0,0,115,8,0,0,0,8,3,4,1,
+ 20,1,255,128,114,238,0,0,0,41,2,78,78,41,1,78,
+ 41,2,78,114,25,0,0,0,41,4,78,78,114,5,0,0,
+ 0,114,25,0,0,0,41,54,114,10,0,0,0,114,7,0,
+ 0,0,114,26,0,0,0,114,95,0,0,0,114,68,0,0,
+ 0,114,133,0,0,0,114,17,0,0,0,114,21,0,0,0,
+ 114,63,0,0,0,114,37,0,0,0,114,47,0,0,0,114,
+ 22,0,0,0,114,23,0,0,0,114,53,0,0,0,114,54,
+ 0,0,0,114,57,0,0,0,114,69,0,0,0,114,71,0,
+ 0,0,114,80,0,0,0,114,90,0,0,0,114,94,0,0,
+ 0,114,105,0,0,0,114,118,0,0,0,114,119,0,0,0,
+ 114,98,0,0,0,114,149,0,0,0,114,155,0,0,0,114,
+ 159,0,0,0,114,114,0,0,0,114,100,0,0,0,114,166,
+ 0,0,0,114,167,0,0,0,114,101,0,0,0,114,169,0,
+ 0,0,114,184,0,0,0,114,189,0,0,0,114,198,0,0,
+ 0,114,200,0,0,0,114,202,0,0,0,114,208,0,0,0,
+ 90,15,95,69,82,82,95,77,83,71,95,80,82,69,70,73,
+ 88,114,210,0,0,0,114,213,0,0,0,218,6,111,98,106,
+ 101,99,116,114,214,0,0,0,114,215,0,0,0,114,216,0,
+ 0,0,114,221,0,0,0,114,227,0,0,0,114,230,0,0,
+ 0,114,231,0,0,0,114,235,0,0,0,114,236,0,0,0,
+ 114,238,0,0,0,114,5,0,0,0,114,5,0,0,0,114,
+ 5,0,0,0,114,6,0,0,0,218,8,60,109,111,100,117,
+ 108,101,62,1,0,0,0,115,106,0,0,0,4,0,8,22,
+ 4,9,4,1,4,1,4,3,8,3,8,8,4,8,4,2,
+ 16,3,14,4,14,77,14,21,8,16,8,37,8,17,14,11,
+ 8,8,8,11,8,12,8,19,14,36,16,101,10,26,14,45,
+ 8,72,8,17,8,17,8,30,8,36,8,45,14,15,14,75,
+ 14,80,8,13,8,9,10,9,8,47,4,16,8,1,8,2,
+ 6,32,8,3,10,16,14,15,8,37,10,27,8,37,8,7,
+ 8,35,12,8,255,128,
};
More information about the Python-checkins
mailing list