gh-131798: Split `_CHECK_AND_ALLOCATE_OBJECT` into smaller uops by Sacul0457 · Pull Request #148433 · python/cpython · GitHub

Issue: Better uop coverage in the JIT optimizer #131798

Hey @Fidget-Spinner, I'm a little lost here
From my understanding:

In _CHECK_OBJECT if tp->tp_version_tag == type_version is true, we remove the guard.
Do we set callable to a const here like it currently does?
If 1. is false, we need to add a type watcher.

This should go into the new _ALLOCATE_OBJECT
It should be callable = sym_new_const(ctx, init); not sym_set_const(callable, init);. There's a difference --- the first overrides the current callable with a new one, the second sets the current callable to a known constant. If you read the code in bytecodes.c, you'll see it's the first one.

Same to bytecodes.c:

Suggested change

      
                        }
          
                        }
          
                   self_or_null = sym_new_not_null(ctx);

Wait sorry, shouldn't this be sym_set_non_null?

No. Please look at bytecodes.c. It's creating a new object, self. That's what _ALLOCATE_OBJECT does. So it should be a new non-null. This is same as the above where it grabs a new __init__ callable. In both of these cases, we do not set the existing symbol, but create a new one. This is a good learning point as it's tricky and requires observing bytecodes.c!

Ah ok

Co-authored-by: Hai Zhu <haiizhu@outlook.com>

@Sacul0457 I'm going to push to this PR, as I think it's a little tricky to get right. Please add a test after I push.

@Sacul0457 please add the following tests:

One test where there's a class outside the trace, and needs to be inferred. E.g.

class MyPoint:
    def __init__(self, x, y):
        return None

def testfunc(n):
    point_local = MyPoint
    for _ in range(n):
        p = point_local(1.0, 2.0)
        p = point_local(1.0, 2.0)

One test where it's directly using the class, and that gets constant folded and removed. E.g.

class MyPoint:
    def __init__(self, x, y):
        return None

def testfunc(n):
    for _ in range(n):
        p = MyPoint(1.0, 2.0)
        p = MyPoint(1.0, 2.0)

Sorry for the wait, I printed the uops trace for the second test and how can we tell if it is constant folded?

['_START_EXECUTOR', '_MAKE_WARM', '_SET_IP', '_CHECK_PERIODIC', '_CHECK_VALIDITY', '_ITER_CHECK_RANGE', '_GUARD_NOT_EXHAUSTED_RANGE', 
'_ITER_NEXT_RANGE', '_SET_IP', '_SWAP_FAST_1', '_SPILL_OR_RELOAD', '_POP_TOP', '_CHECK_VALIDITY', '_SET_IP', '_LOAD_DEREF', 
'_CHECK_VALIDITY', '_PUSH_NULL', '_LOAD_CONST_INLINE_BORROW', '_SPILL_OR_RELOAD', '_LOAD_CONST_INLINE_BORROW', '_SET_IP', 
'_SPILL_OR_RELOAD', '_CHECK_OBJECT', '_ALLOCATE_OBJECT', '_CREATE_INIT_FRAME', '_PUSH_FRAME', '_CHECK_VALIDITY', 
'_TIER2_RESUME_CHECK', '_LOAD_CONST_INLINE_BORROW', '_SET_IP', '_RETURN_VALUE', '_CHECK_VALIDITY', '_SET_IP', '_EXIT_INIT_CHECK', 
'_CHECK_VALIDITY', '_SET_IP', '_MAKE_HEAP_SAFE', '_RETURN_VALUE', '_GUARD_IP_RETURN_VALUE', '_GUARD_CODE_VERSION_RETURN_VALUE', 
'_CHECK_VALIDITY', '_SET_IP', '_SWAP_FAST_2', '_POP_TOP', '_CHECK_VALIDITY', '_SET_IP', '_LOAD_DEREF', '_CHECK_VALIDITY', 
'_PUSH_NULL', '_LOAD_CONST_INLINE_BORROW', '_SPILL_OR_RELOAD', '_LOAD_CONST_INLINE_BORROW', '_SET_IP', '_SPILL_OR_RELOAD', 
'_CHECK_OBJECT', '_ALLOCATE_OBJECT', '_CREATE_INIT_FRAME', '_PUSH_FRAME', '_CHECK_VALIDITY', '_TIER2_RESUME_CHECK', 
'_LOAD_CONST_INLINE_BORROW', '_SET_IP', '_RETURN_VALUE', '_CHECK_VALIDITY', '_SET_IP', '_EXIT_INIT_CHECK', '_CHECK_VALIDITY', 
'_SET_IP', '_MAKE_HEAP_SAFE', '_RETURN_VALUE', '_GUARD_IP_RETURN_VALUE', '_GUARD_CODE_VERSION_RETURN_VALUE', '_CHECK_VALIDITY', '_SET_IP', '_SWAP_FAST_2', '_POP_TOP', '_JUMP_TO_TOP', ...]

@Sacul0457 that's strange, seems like it's not being constant folded in the second case. Let me fix that.

Oh alright. I'm probably going to bed now, please feel free to add the tests too as I don't want to hold up this PR being merged. Thank you!

Sorry Sacul, I forgot to mention that you can't nest MyPoint in the test, it needs to be a global to be promoted. My bad, and good night!

Thank you for splitting the ops in bytecodes.c Sacul.

…ler uops (pythonGH-148433)" This reverts commit 18d7d90.

…pythonGH-148433) Co-authored-by: Hai Zhu <haiizhu@outlook.com> Co-authored-by: Ken Jin <kenjin4096@gmail.com>

Sacul0457 added 3 commits April 12, 2026 18:40

initial commit to split the uops

9c745a0

revert test

d976e47

remove empty line

c72c139

Sacul0457 requested review from Fidget-Spinner, markshannon, savannahostrowski and tomasr8 as code owners April 12, 2026 10:47

bedevere-app Bot added the awaiting review label Apr 12, 2026

bedevere-app Bot mentioned this pull request Apr 12, 2026

Better uop coverage in the JIT optimizer #131798

Open

Sacul0457 marked this pull request as draft April 12, 2026 10:47

bedevere-app Bot removed the awaiting review label Apr 12, 2026

Fidget-Spinner reviewed Apr 12, 2026

View reviewed changes

cocolato reviewed Apr 12, 2026

View reviewed changes

Partially address reviews

7885033

Co-authored-by: Hai Zhu <haiizhu@outlook.com>

handle probable and non-probable cases

13e2608

lint

fc0c169

Fidget-Spinner added the skip news label Apr 12, 2026

Sacul0457 marked this pull request as ready for review April 12, 2026 17:42

bedevere-app Bot added the awaiting review label Apr 12, 2026

add tests

a459c25

Fidget-Spinner approved these changes Apr 12, 2026

View reviewed changes

bedevere-app Bot added awaiting merge and removed awaiting review labels Apr 12, 2026

Fidget-Spinner merged commit 18d7d90 into python:main Apr 12, 2026
78 checks passed

bedevere-app Bot removed the awaiting merge label Apr 12, 2026

prakashsellathurai added a commit to prakashsellathurai/cpython that referenced this pull request Apr 13, 2026

Revert "pythongh-131798 : Split _CHECK_AND_ALLOCATE_OBJECT into smal…

769e5da

…ler uops (pythonGH-148433)" This reverts commit 18d7d90.

ljfp pushed a commit to ljfp/cpython that referenced this pull request Apr 25, 2026

pythongh-131798 : Split _CHECK_AND_ALLOCATE_OBJECT into smaller uops (…

8aac827

…pythonGH-148433) Co-authored-by: Hai Zhu <haiizhu@outlook.com> Co-authored-by: Ken Jin <kenjin4096@gmail.com>

                           assert(init != NULL);
                           assert(PyFunction_Check(init));
-                          callable = sym_new_const(ctx, init);
+                          sym_set_const(callable, init);

+                                  PyType_Watch(TYPE_WATCHER_ID, (PyObject *)type);
+                                  _Py_BloomFilter_Add(dependencies, type);
+                              }
+                          }

gh-131798: Split `_CHECK_AND_ALLOCATE_OBJECT` into smaller uops by Sacul0457 · Pull Request #148433 · python/cpython · GitHub

Repository navigation

gh-131798: Split _CHECK_AND_ALLOCATE_OBJECT into smaller uops - #148433

gh-131798: Split _CHECK_AND_ALLOCATE_OBJECT into smaller uops#148433Fidget-Spinner merged 7 commits intopython:mainpython/cpython:mainfrom Sacul0457:Split-_CHECK_AND_ALLOCATE_OBJECTSacul0457/cpython:Split-_CHECK_AND_ALLOCATE_OBJECTCopy head branch name to clipboard

Conversation

Sacul0457 commented Apr 12, 2026 • edited by bedevere-app Bot Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

Sacul0457 commented Apr 12, 2026

Uh oh!

Fidget-Spinner Apr 12, 2026

Choose a reason for hiding this comment

Uh oh!

Uh oh!

cocolato Apr 12, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Sacul0457 Apr 12, 2026

Choose a reason for hiding this comment

Uh oh!

Fidget-Spinner Apr 12, 2026

Choose a reason for hiding this comment

Uh oh!

Sacul0457 Apr 12, 2026

Choose a reason for hiding this comment

Uh oh!

Fidget-Spinner commented Apr 12, 2026

Uh oh!

Fidget-Spinner commented Apr 12, 2026

Uh oh!

Sacul0457 commented Apr 12, 2026

Uh oh!

Fidget-Spinner commented Apr 12, 2026

Uh oh!

Sacul0457 commented Apr 12, 2026

Uh oh!

Fidget-Spinner commented Apr 12, 2026

Uh oh!

Fidget-Spinner left a comment

Choose a reason for hiding this comment

Uh oh!

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

3 participants

gh-131798: Split _CHECK_AND_ALLOCATE_OBJECT into smaller uops#148433
Fidget-Spinner merged 7 commits into
python:mainfrom
Sacul0457:Split-_CHECK_AND_ALLOCATE_OBJECT

Sacul0457 commented Apr 12, 2026 •
edited by bedevere-app Bot
Loading

cocolato Apr 12, 2026 •
edited
Loading