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GH-113710: Tier 2 optimizer: check the function instead of checking globals.#116410

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markshannon merged 3 commits intopython:mainfrom
faster-cpython:globals-check-to-function-check
Mar 6, 2024
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GH-113710: Tier 2 optimizer: check the function instead of checking globals.#116410
markshannon merged 3 commits intopython:mainfrom
faster-cpython:globals-check-to-function-check

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@markshannon markshannon commented Mar 6, 2024 •
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Since the globals and builtin fields of function objects are immutable, we can check the function instead of the globals and builtins.

This is:

  • Never slower, we never add more checks
  • Faster for inlined calls as _INIT_CALL_PY_EXACT_ARGS implicitly checks the function, so no additional checks are needed.
  • Faster in many other cases, as we can replace _CHECK_GLOBALS + _CHECK_BUILTINS with _CHECK_FUNCTION.

@bedevere-app bedevere-app bot mentioned this pull request Mar 6, 2024
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@markshannon markshannon merged commit 27858e2 into python:main Mar 6, 2024
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gvanrossum commented Mar 6, 2024

@markshannon, Is this correct? WhenI run a really simple test with debug output, I get a DEOPT message for _CHECK_FUNCTION for each iteration; before this PR I only got one DEOPT message at the end of the loop.

Code:

import _testinternalcapi

def cast(typ, val):
    return val

def testfunc(n):
    x = 0
    for i in range(n):
        x = cast(int, i)
    return x

def main():
    count = 20
    a = testfunc(count)
    assert a + 1 == count, (a, count)
    old_opt = _testinternalcapi.get_optimizer()
    opt = _testinternalcapi.new_uop_optimizer()
    _testinternalcapi.set_optimizer(opt)
    a = testfunc(count)
    _testinternalcapi.set_optimizer(old_opt)
    assert a + 1 == count, (a, count)

main()

Before:

Optimized executor (length 27):
   0 OPTIMIZED: _START_EXECUTOR (52685, target=-842150451, operand=12a70eb70)
   1 OPTIMIZED: _CHECK_VALIDITY (0, target=33, operand=1031faf9a)
   2 OPTIMIZED: _SET_IP (0, target=14, operand=1031faf74)
   3 OPTIMIZED: _ITER_CHECK_RANGE (19, target=14, operand=0)
   4 OPTIMIZED: _GUARD_NOT_EXHAUSTED_RANGE (19, target=14, operand=0)
   5 OPTIMIZED: _ITER_NEXT_RANGE (19, target=14, operand=0)
   6 OPTIMIZED: _CHECK_VALIDITY (0, target=16, operand=1031faf78)
   7 OPTIMIZED: _STORE_FAST_2 (2, target=16, operand=0)
   8 OPTIMIZED: _CHECK_GLOBALS (3, target=17, operand=10330f050)
   9 OPTIMIZED: _LOAD_CONST_INLINE_WITH_NULL (3, target=17, operand=1032fa150)
  10 OPTIMIZED: _CHECK_BUILTINS (4, target=22, operand=10323fa70)
  11 OPTIMIZED: _LOAD_CONST_INLINE_BORROW (4, target=22, operand=102e39508)
  12 OPTIMIZED: _LOAD_FAST_2 (2, target=27, operand=0)
  13 OPTIMIZED: _SET_IP (0, target=28, operand=1031faf90)
  14 OPTIMIZED: _CHECK_FUNCTION_EXACT_ARGS (2, target=28, operand=2c9)
  15 OPTIMIZED: _CHECK_STACK_SPACE (2, target=28, operand=0)
  16 OPTIMIZED: _INIT_CALL_PY_EXACT_ARGS_2 (2, target=28, operand=0)
  17 OPTIMIZED: _SAVE_RETURN_OFFSET (4, target=28, operand=0)
  18 OPTIMIZED: _PUSH_FRAME (2, target=28, operand=1032fa150)
  19 OPTIMIZED: _CHECK_VALIDITY (0, target=0, operand=1033690f8)
  20 OPTIMIZED: _RESUME_CHECK (0, target=0, operand=0)
  21 OPTIMIZED: _LOAD_FAST_1 (1, target=1, operand=0)
  22 OPTIMIZED: _SET_IP (0, target=2, operand=1033690fc)
  23 OPTIMIZED: _POP_FRAME (0, target=2, operand=10336fa10)
  24 OPTIMIZED: _CHECK_VALIDITY (0, target=32, operand=1031faf98)
  25 OPTIMIZED: _STORE_FAST_1 (1, target=32, operand=0)
  26 OPTIMIZED: _JUMP_TO_TOP (0, target=0, operand=0)
DEOPT: [UOp _GUARD_NOT_EXHAUSTED_RANGE (19, target=14, operand=0) -> FOR_ITER_RANGE]

After:

Optimized executor (length 26):
   0 OPTIMIZED: _START_EXECUTOR (52685, target=-842150451, operand=12670ec50)
   1 OPTIMIZED: _CHECK_VALIDITY (0, target=33, operand=100dd2f9a)
   2 OPTIMIZED: _SET_IP (0, target=14, operand=100dd2f74)
   3 OPTIMIZED: _ITER_CHECK_RANGE (19, target=14, operand=0)
   4 OPTIMIZED: _GUARD_NOT_EXHAUSTED_RANGE (19, target=14, operand=0)
   5 OPTIMIZED: _ITER_NEXT_RANGE (19, target=14, operand=0)
   6 OPTIMIZED: _CHECK_VALIDITY (0, target=16, operand=100dd2f78)
   7 OPTIMIZED: _STORE_FAST_2 (2, target=16, operand=0)
   8 OPTIMIZED: _CHECK_FUNCTION (3, target=17, operand=100ee7050)
   9 OPTIMIZED: _LOAD_CONST_INLINE_WITH_NULL (3, target=17, operand=100ed2210)
  10 OPTIMIZED: _LOAD_CONST_INLINE_BORROW (4, target=22, operand=100a11508)
  11 OPTIMIZED: _LOAD_FAST_2 (2, target=27, operand=0)
  12 OPTIMIZED: _SET_IP (0, target=28, operand=100dd2f90)
  13 OPTIMIZED: _CHECK_FUNCTION_EXACT_ARGS (2, target=28, operand=2c9)
  14 OPTIMIZED: _CHECK_STACK_SPACE (2, target=28, operand=0)
  15 OPTIMIZED: _INIT_CALL_PY_EXACT_ARGS_2 (2, target=28, operand=0)
  16 OPTIMIZED: _SAVE_RETURN_OFFSET (4, target=28, operand=0)
  17 OPTIMIZED: _PUSH_FRAME (2, target=28, operand=100ed2210)
  18 OPTIMIZED: _CHECK_VALIDITY (0, target=0, operand=100f410f8)
  19 OPTIMIZED: _RESUME_CHECK (0, target=0, operand=0)
  20 OPTIMIZED: _LOAD_FAST_1 (1, target=1, operand=0)
  21 OPTIMIZED: _SET_IP (0, target=2, operand=100f410fc)
  22 OPTIMIZED: _POP_FRAME (0, target=2, operand=100f47ad0)
  23 OPTIMIZED: _CHECK_VALIDITY (0, target=32, operand=100dd2f98)
  24 OPTIMIZED: _STORE_FAST_1 (1, target=32, operand=0)
  25 OPTIMIZED: _JUMP_TO_TOP (0, target=0, operand=0)
DEOPT: [UOp _CHECK_FUNCTION (3, target=17, operand=100ee7050) -> FOR_ITER_RANGE]
DEOPT: [UOp _CHECK_FUNCTION (3, target=17, operand=100ee7050) -> FOR_ITER_RANGE]
DEOPT: [UOp _CHECK_FUNCTION (3, target=17, operand=100ee7050) -> FOR_ITER_RANGE]
DEOPT: [UOp _CHECK_FUNCTION (3, target=17, operand=100ee7050) -> FOR_ITER_RANGE]
DEOPT: [UOp _CHECK_FUNCTION (3, target=17, operand=100ee7050) -> FOR_ITER_RANGE]
DEOPT: [UOp _CHECK_FUNCTION (3, target=17, operand=100ee7050) -> FOR_ITER_RANGE]
DEOPT: [UOp _CHECK_FUNCTION (3, target=17, operand=100ee7050) -> FOR_ITER_RANGE]
DEOPT: [UOp _CHECK_FUNCTION (3, target=17, operand=100ee7050) -> FOR_ITER_RANGE]
DEOPT: [UOp _CHECK_FUNCTION (3, target=17, operand=100ee7050) -> FOR_ITER_RANGE]
DEOPT: [UOp _CHECK_FUNCTION (3, target=17, operand=100ee7050) -> FOR_ITER_RANGE]
DEOPT: [UOp _CHECK_FUNCTION (3, target=17, operand=100ee7050) -> FOR_ITER_RANGE]
DEOPT: [UOp _CHECK_FUNCTION (3, target=17, operand=100ee7050) -> FOR_ITER_RANGE]
DEOPT: [UOp _CHECK_FUNCTION (3, target=17, operand=100ee7050) -> FOR_ITER_RANGE]
DEOPT: [UOp _CHECK_FUNCTION (3, target=17, operand=100ee7050) -> FOR_ITER_RANGE]
DEOPT: [UOp _CHECK_FUNCTION (3, target=17, operand=100ee7050) -> FOR_ITER_RANGE]
DEOPT: [UOp _CHECK_FUNCTION (3, target=17, operand=100ee7050) -> FOR_ITER_RANGE]
DEOPT: [UOp _CHECK_FUNCTION (3, target=17, operand=100ee7050) -> FOR_ITER_RANGE]
DEOPT: [UOp _CHECK_FUNCTION (3, target=17, operand=100ee7050) -> FOR_ITER_RANGE]
DEOPT: [UOp _CHECK_FUNCTION (3, target=17, operand=100ee7050) -> FOR_ITER_RANGE]
DEOPT: [UOp _GUARD_NOT_EXHAUSTED_RANGE (19, target=14, operand=0) -> FOR_ITER_RANGE]

That's the _CHECK_FUNCTION call at index 8 deoptimizing every time.

@brandtbucher
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brandtbucher commented Mar 7, 2024

@markshannon, Is this correct? WhenI run a really simple test with debug output, I get a DEOPT message for _CHECK_FUNCTION for each iteration; before this PR I only got one DEOPT message at the end of the loop.

Yep, the bug is that this PR doesn't update the operand, just the opcode. So it's incorrectly comparing the function to the builtin or globals dicts.

@markshannon markshannon mentioned this pull request Mar 7, 2024
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markshannon commented Mar 7, 2024

#116460

adorilson pushed a commit to adorilson/cpython that referenced this pull request Mar 25, 2024
@markshannon @adorilson
pythonGH-113710: Tier 2 optimizer: check the function instead of chec…
c3d9d46 
…king globals. (pythonGH-116410)
diegorusso pushed a commit to diegorusso/cpython that referenced this pull request Apr 17, 2024
@markshannon @diegorusso
pythonGH-113710: Tier 2 optimizer: check the function instead of chec…
05a9af1 
…king globals. (pythonGH-116410)
@markshannon markshannon deleted the globals-check-to-function-check branch August 6, 2024 10:18
@markshannon markshannon restored the globals-check-to-function-check branch August 15, 2025 14:33
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