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GeezerVison is showing github.com — gh-131798: JIT: Assign type to sliced string/list/tuple by fluhus · Pull Request #134671 · python/cpython

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@fluhus

@fluhus fluhus commented May 25, 2025

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Slicing a string/list/tuple always returns the same type.
Make the optimizer assign a string/list/tuple type to the result of slicing a string/list/tuple.

@brandtbucher

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

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fluhus added 4 commits May 25, 2025 11:25
@fluhus
JIT: Assign type to sliced string
61207d2
@fluhus
Revert accidental whitespace change
e281791
@fluhus
JIT: Remove guard for slicing known type list
e45c280
@fluhus
JIT: Remove guard for slicing known type tuple
4eade4a
@fluhus
fluhus requested a review from Fidget-Spinner as a code owner May 25, 2025 19:29
@bedevere-app bedevere-app Bot added the awaiting review label May 25, 2025
@bedevere-app bedevere-app Bot mentioned this pull request May 25, 2025
Better uop coverage in the JIT optimizer #131798
Open
@blurb-it
📜🤖 Added by blurb_it.
a2bba45
eendebakpt
eendebakpt reviewed May 25, 2025
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Comment thread Python/optimizer_bytecodes.c
// Slicing a string/list/tuple always returns the same type.
PyTypeObject *type = sym_get_type(container);
if (type == &PyUnicode_Type ||
type == &PyList_Type ||

@eendebakpt eendebakpt May 25, 2025

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Suggested change
type == &PyList_Type ||
type == &PyBytes_Type ||
type == &PyList_Type ||

I do not know whether slicing a bytes object occurs often enough to add PyBytes_Type here (and whether the jit slows down if we add more cases here), but if I understand correctly slicing bytes (or bytearray) results in a bytes (or bytearray) so we could add them.

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@brandtbucher brandtbucher Jun 5, 2025

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@fluhus, this PR is probably fine for now, but feel free to add other sequence types like this in a follow-up PR (with tests)!

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brandtbucher
brandtbucher approved these changes Jun 5, 2025
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@brandtbucher brandtbucher left a comment

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Looks great, just one style nitpick:

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Comment thread Lib/test/test_capi/test_opt.py
for i in range(n):
false = i == TIER2_THRESHOLD
empty = "X"[:false]
empty += "" # Make JIT realize this is a string.

@brandtbucher brandtbucher Jun 1, 2025

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Nice!

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Comment thread Python/optimizer_bytecodes.c Resolved

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Comment thread Python/optimizer_bytecodes.c
// Slicing a string/list/tuple always returns the same type.
PyTypeObject *type = sym_get_type(container);
if (type == &PyUnicode_Type ||
type == &PyList_Type ||

@brandtbucher brandtbucher Jun 5, 2025

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@fluhus, this PR is probably fine for now, but feel free to add other sequence types like this in a follow-up PR (with tests)!

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@bedevere-app bedevere-app Bot added awaiting merge and removed awaiting review labels Jun 5, 2025
brandtbucher
brandtbucher reviewed Jun 6, 2025
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Comment thread Python/optimizer_cases.c.h Resolved

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@brandtbucher
PEP 7
2bb095b
@brandtbucher
brandtbucher merged commit 8fdbbf8 into python:main Jun 7, 2025
@bedevere-app bedevere-app Bot removed the awaiting merge label Jun 7, 2025
@fluhus
fluhus deleted the amit branch June 17, 2025 17:38
lkollar pushed a commit to lkollar/cpython that referenced this pull request Jun 19, 2025
@fluhus @lkollar
pythonGH-131798: Type-propagate string/list/tuple slices (pythonGH-13…
a3b80c0 
…4671)
Pranjal095 pushed a commit to Pranjal095/cpython that referenced this pull request Jul 12, 2025
@fluhus @Pranjal095
pythonGH-131798: Type-propagate string/list/tuple slices (pythonGH-13…
8ebc5f6 
…4671)
taegyunkim pushed a commit to taegyunkim/cpython that referenced this pull request Aug 4, 2025
@fluhus @taegyunkim
pythonGH-131798: Type-propagate string/list/tuple slices (pythonGH-13…
73b6b1d 
…4671)
Agent-Hellboy pushed a commit to Agent-Hellboy/cpython that referenced this pull request Aug 19, 2025
@fluhus @Agent-Hellboy
pythonGH-131798: Type-propagate string/list/tuple slices (pythonGH-13…
1b5e5ca 
…4671)
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@eendebakpt eendebakpt eendebakpt left review comments
@brandtbucher brandtbucher brandtbucher approved these changes
@Fidget-Spinner Fidget-Spinner Awaiting requested review from Fidget-Spinner Fidget-Spinner is a code owner

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3 participants

@fluhus @eendebakpt @brandtbucher
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