Skip to content

gh-142961: Fix constant folding len(tuple) in JIT #142963

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
Fidget-Spinner merged 5 commits into from
Dec 19, 2025
Merged

gh-142961: Fix constant folding len(tuple) in JIT #142963

Show file tree
Hide file tree
Changes from 3 commits
Commits
Show all changes
5 commits
Select commit Hold shift + click to select a range
473b8d3
Fix constant folding len(tuple)
Fidget-Spinner Dec 19, 2025
9cb5af3
📜🤖 Added by blurb_it.
blurb-it[bot] Dec 19, 2025
326220b
Update 2025-12-19-00-59-29.gh-issue-142961.q8WRSq.rst
Fidget-Spinner Dec 19, 2025
9fec34d
Address review
Fidget-Spinner Dec 19, 2025
b8e7866
avoid name clash
Fidget-Spinner Dec 19, 2025
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
1,499 changes: 752 additions & 747 deletions Include/internal/pycore_uop_ids.h
View file
Open in desktop

Large diffs are not rendered by default.

21 changes: 21 additions & 0 deletions Include/internal/pycore_uop_metadata.h
View file
Open in desktop

Some generated files are not rendered by default. Learn more about how customized files appear on GitHub.

12 changes: 12 additions & 0 deletions Lib/test/test_capi/test_opt.py
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -3008,6 +3008,18 @@ class Obj:
for _ in range(TIER2_THRESHOLD+1):
obj.attr = EvilAttr(obj.__dict__)

def test_constant_fold_tuple(self):
def testfunc(n):
for _ in range(n):
t = (1,)
p = len(t)

res, ex = self._run_with_optimizer(testfunc, TIER2_THRESHOLD)
self.assertIsNotNone(ex)
uops = get_opnames(ex)

self.assertNotIn("_CALL_LEN", uops)

def test_binary_subscr_list_int(self):
def testfunc(n):
l = [1]
Expand Down
1 change: 1 addition & 0 deletions Misc/NEWS.d/next/Core_and_Builtins/2025-12-19-00-59-29.gh-issue-142961.q8WRSq.rst
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -0,0 +1 @@
Fix a segfault in the JIT when constant folding ``len(tuple)``.
7 changes: 7 additions & 0 deletions Python/bytecodes.c
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -5285,6 +5285,13 @@ dummy_func(
value = PyStackRef_FromPyObjectBorrow(ptr);
}

tier2 op(_SWAP_CALL_ARG_LOAD_CONST_INLINE_BORROW, (ptr/4, callable, null, arg -- res, a, c)) {
Copy link
Copy Markdown
Member

@markshannon markshannon Dec 19, 2025

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Can you give this a name that describes what it does. It doesn't call anything, nor have an argument.
callable must be the builtin len function, so is immortal and can be dropped. Avoid the register shuffle:

Suggested change
tier2 op(_SWAP_CALL_ARG_LOAD_CONST_INLINE_BORROW, (ptr/4, callable, null, arg -- res, a, c)) {
tier2 op(_LOAD_CONST_INLINE_BORROW_SWAP4_DROP, (ptr/4, callable, null, arg -- res, n, a)) {
assert(_Py_IsImmortal(callable));

Copy link
Copy Markdown
Member Author

@Fidget-Spinner Fidget-Spinner Dec 19, 2025

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Done.

Copy link
Copy Markdown
Member

@markshannon markshannon Dec 19, 2025

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Not quite done. You don't need to shuffle the values around as much.

Copy link
Copy Markdown
Member Author

@Fidget-Spinner Fidget-Spinner Dec 19, 2025

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

If I dont shuffle them the following POP_TOP will segfault?

Copy link
Copy Markdown
Member

@markshannon markshannon Dec 19, 2025

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

It won't on the default build, as NULL is immortal. You'd need to check on the FT build.

res = PyStackRef_FromPyObjectBorrow(ptr);
a = arg;
c = callable;
INPUTS_DEAD();
}

tier2 op(_POP_CALL_TWO_LOAD_CONST_INLINE_BORROW, (ptr/4, callable, null, pop1, pop2 -- value)) {
PyStackRef_CLOSE(pop2);
PyStackRef_CLOSE(pop1);
Expand Down
100 changes: 100 additions & 0 deletions Python/executor_cases.c.h
View file
Open in desktop

Some generated files are not rendered by default. Learn more about how customized files appear on GitHub.

6 changes: 1 addition & 5 deletions Python/optimizer_bytecodes.c
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -529,10 +529,6 @@ dummy_func(void) {
value = PyJitRef_Borrow(sym_new_const(ctx, ptr));
}

op(_POP_CALL_ONE_LOAD_CONST_INLINE_BORROW, (ptr/4, unused, unused, unused -- value)) {
value = PyJitRef_Borrow(sym_new_const(ctx, ptr));
}

op(_POP_CALL_TWO_LOAD_CONST_INLINE_BORROW, (ptr/4, unused, unused, unused, unused -- value)) {
value = PyJitRef_Borrow(sym_new_const(ctx, ptr));
}
Expand Down Expand Up @@ -1263,7 +1259,7 @@ dummy_func(void) {
goto error;
}
if (_Py_IsImmortal(temp)) {
REPLACE_OP(this_instr, _POP_CALL_ONE_LOAD_CONST_INLINE_BORROW,
REPLACE_OP(this_instr, _SWAP_CALL_ARG_LOAD_CONST_INLINE_BORROW,
0, (uintptr_t)temp);
}
res = sym_new_const(ctx, temp);
Expand Down
18 changes: 15 additions & 3 deletions Python/optimizer_cases.c.h
View file
Open in desktop

Some generated files are not rendered by default. Learn more about how customized files appear on GitHub.

Loading