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GeezerVison is showing github.com — gh-131798: JIT: Narrow the return type of _CALL_LEN to int by diegorusso · Pull Request #132940 · python/cpython

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@diegorusso

@diegorusso diegorusso commented Apr 25, 2025 •
edited by bedevere-app Bot
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Reduce unnecessary guards whenever len() is called and used in arithmetic operations.

  • Issue: Better uop coverage in the JIT optimizer #131798

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@diegorusso
pythongh-131798: JIT: Narrow the return type of _CALL_LEN to int
ee947e3 
Reduce unnecessary guards whenever `len()` is called and used
in arithmetic operations.
@diegorusso
diegorusso requested a review from Fidget-Spinner as a code owner April 25, 2025 13:58
@bedevere-app bedevere-app Bot added the awaiting review label Apr 25, 2025
@diegorusso
diegorusso requested review from brandtbucher and removed request for Fidget-Spinner April 25, 2025 13:58
@bedevere-app bedevere-app Bot mentioned this pull request Apr 25, 2025
Better uop coverage in the JIT optimizer #131798
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@diegorusso
diegorusso requested a review from Fidget-Spinner April 25, 2025 14:34
Fidget-Spinner
Fidget-Spinner approved these changes Apr 25, 2025
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Thanks!

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@bedevere-app bedevere-app Bot added awaiting merge and removed awaiting review labels Apr 25, 2025
@Fidget-Spinner

Fidget-Spinner commented Apr 25, 2025

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Windows JIT builds might've been broken by #132852. That PR did not trigger JIT CI.
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tomasr8
tomasr8 reviewed Apr 25, 2025
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Comment thread Python/optimizer_bytecodes.c Resolved

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Comment thread Lib/test/test_capi/test_opt.py
Comment on lines +1916 to +1920
a = [1, 2, 3, 4]
for _ in range(n):
_ = len(a) - 1

_, ex = self._run_with_optimizer(testfunc, TIER2_THRESHOLD)

@tomasr8 tomasr8 Apr 25, 2025

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I don't know if it's needed in this case, but for other tests there's normally a 'control' variable that checks that the result is still correct even with the optimization. Something like this:

Suggested change
a = [1, 2, 3, 4]
for _ in range(n):
_ = len(a) - 1
_, ex = self._run_with_optimizer(testfunc, TIER2_THRESHOLD)
x = 0
a = [1, 2, 3, 4]
for _ in range(n):
_ = len(a) - 1
if _ == 3:
x += 1
_, ex = self._run_with_optimizer(testfunc, TIER2_THRESHOLD)
self.assertEqual(res, TIER2_THRESHOLD)

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@diegorusso diegorusso Apr 25, 2025

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Good point, I'll do it.

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@diegorusso diegorusso Apr 25, 2025

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OK the problem is if I add this, _GUARD_TOS_INT and _GUARD_NOS_INT are appearing in the uops list.

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@Fidget-Spinner Fidget-Spinner Apr 25, 2025

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Yeah we can't do it. x is from outside the loop (trace), so the first x += 1 has to have a guard somewhere.

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  • 👍 2 reactions
@blurb-it
📜🤖 Added by blurb_it.
705bf8b
tekknolagi
tekknolagi reviewed Apr 25, 2025
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Comment thread Misc/NEWS.d/next/Core_and_Builtins/2025-04-25-14-56-45.gh-issue-131798.NpcKub.rst Resolved

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Fidget-Spinner and others added 2 commits April 26, 2025 01:48
@Fidget-Spinner
Merge branch 'main' into call-len
e4e6bbf
@diegorusso @tekknolagi
Update Misc/NEWS.d/next/Core_and_Builtins/2025-04-25-14-56-45.gh-issu…
a017e93 
…e-131798.NpcKub.rst

Co-authored-by: Max Bernstein <[email protected]>
@Fidget-Spinner
Fidget-Spinner merged commit 4c20f46 into python:main Apr 25, 2025
@bedevere-app bedevere-app Bot removed the awaiting merge label Apr 25, 2025
@diegorusso
diegorusso deleted the call-len branch April 30, 2025 00:15
@tomasr8 tomasr8 mentioned this pull request May 1, 2025
Keep instruction definitions in bytecodes.c and optimizer_bytecodes.c in sync #133273
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@tomasr8 tomasr8 tomasr8 left review comments
@Fidget-Spinner Fidget-Spinner Fidget-Spinner approved these changes
@brandtbucher brandtbucher Awaiting requested review from brandtbucher
+1 more reviewer
@tekknolagi tekknolagi tekknolagi left review comments
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4 participants

@diegorusso @Fidget-Spinner @tekknolagi @tomasr8
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