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GeezerVison is showing github.com — gh-118335: Configure Tier 2 interpreter at build time by gvanrossum · Pull Request #118339 · python/cpython

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gvanrossum commented Apr 27, 2024 •

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The code for Tier 2 is now only compiled when configured with --enable-experimental-jit[=yes|interpreter]. We drop support for PYTHON_UOPS and -Xuops, but you can disable the interpreter or JIT at runtime by setting PYTHON_JIT=0. You can also build it without enabling it by default using --enable-experimental-jit=yes-off; enable with PYTHON_JIT=1.

@mdboom See note in issue about benchmarking setup.

~~@markshannon An alternative approach would be to keep the APIs but make them always fail. In particular, there are some PyUnstable APIs that will only exist when _Py_TIER2 is defined. Thoughts?~~

EDIT: In particular, we could arguably keep offering PyUnstable_{Get,Set}Optimizer, so 3rd parties could create and activate their own optimizers, like in your original design (which I cannot find back -- you had something where 3rd parties could register optimizations and parameters indicating the cost and benefit, or something). However, the rest of the optimizer machinery is now dependent on executors (starting with _PyOptimizer_Optimize, ). If we wanted to keep supporting both optimizers and executors, we'd have to do something different in ENTER_EXECUTOR too. (Possibly in both cases the key issue is that GOTO_TIER_TWO(executor) assumes JIT or Tier 2 IR.)

EDIT 2: Another consideration is whether we'd still want the runtime -Xuops flag and the PYTHON_UOPS env var, when enabled at build time. Or perhaps at least PYTHON_UOPS=0 to disable at runtime (which is a simple change in pylifecycle.c). I'd use that when debugging tests with PYTHON_LLTRACE=N, since the debug output from the test infrastructure might overwhelm that for the test proper.

~~Yet another option would be to leave everything as it was, except change the default with the build-time flag.~~

Issue: Configure Tier 2 interpreter at build time #118335

📚 Documentation preview 📚: https://cpython-previews--118339.org.readthedocs.build/

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gvanrossum added 10 commits

April 26, 2024 14:11


          Step 1: replace 'python -Xuops' with 'configure --enable-experimental…

1eb8fea

…-tier2'


          Make JIT imply TIER2, for convenience

0863c17


          Step 2: Remove all code from optimizer*.c unless TIER2; fix deps exce…

9e43331

…pt _testinternalcapi


          Remove TIER2 stuff from _testinternalcapi

064de58


          Fix test_dis.py: _opcode.get_executor() may raise RuntimeError

13b8ef0


          Fix test_regrtest (by tweaking without_getoptimizer)

edbaeef


          Fix test_optimizer.py


          Fix test_opcache

300ae6d


          Fix test_monitoring

db911e4


          Fix test_capi.test_opt (by disabling unless get_optimizer exists)

8cb71dd

gvanrossum requested a review from markshannon

April 27, 2024 00:30

bedevere-app Bot mentioned this pull request

Apr 27, 2024

Configure Tier 2 interpreter at build time #118335

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gvanrossum commented Apr 27, 2024 •

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WASI build is failing, just like it did before when I had an option to disable Tier 2.

I'm away from my Windows laptop so I can't debug the Windows JIT failures yet -- this seems to be in test_opcache.TestRacesDoNotCrash.test_store_attr_with_hint.

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gvanrossum added 2 commits

April 26, 2024 20:49


          Fix _opcode.c

7e79509


          Fix warning in sysmodule.c

638b7ec

gvanrossum commented Apr 27, 2024

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There's also this failure (a hang in test_multiprocessing, apparently): https://github.com/python/cpython/actions/runs/8857124270/job/24324215355?pr=118339

PS. I've updated the discussion in the initial comment.

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gvanrossum commented Apr 27, 2024

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Benchmark says 1% faster (in Tier 1 mode).

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gvanrossum mentioned this pull request

Apr 29, 2024

Move Tier 2 interpreter out of _PyEval_EvalFrameDefault #116970

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gvanrossum added 3 commits

April 29, 2024 15:55


          When compiling _testinternalcapi.c, define _Py_JIT

8fc905f


          Try making WASI Debug recursion limit 400

877a005


          Merge main into tier2-flag

e4464d4

gvanrossum commented Apr 29, 2024

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Looks like Windows JIT builds now pass. WASI build still fails. I wonder if there's something in the WASI build similar to the Windows problem (which had to do with _Py_TIER2 never getting set in a place where it was tested).

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mdboom mentioned this pull request

Apr 30, 2024

Use new configure flags for Tier2 and JIT python/bench_runner#183

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gvanrossum added 4 commits

April 30, 2024 07:39


          Revert "Try making WASI Debug recursion limit 400"

ffd7722

It doesn't work. I'm giving up.

This reverts commit 877a005.


          Update jit/README.md to require LLVM 18 everywhere

6e2777b


          Rip out --enable-experimental-tier2, in favor of --enable-experimenta…

f228a06

…l-jit=XXX

There's more to do.


          Rip out _Py_TIER2, replace with _Py_JIT

70e18a5

The value is a bitflag:
- 0: off
- 1: JIT, on by default
- 3: JIT, off by default (not yet implemented, requires fiddling pystate.c)
- 4: tier 2 interpreter, on by default

gvanrossum force-pushed the tier2-flag branch from e8cf5bd to 70e18a5 Compare

April 30, 2024 14:41

mdboom requested changes

Apr 30, 2024

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This may already be on your radar, but a reminder to also update the Windows build.bat script to support this 4-way option.

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bedevere-app Bot added the awaiting core review label

Apr 30, 2024

gvanrossum requested review from mdboom and removed request for ericsnowcurrently, erlend-aasland and markshannon

April 30, 2024 20:53

gvanrossum commented Apr 30, 2024

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WASI bliss at last.

@brandtbucher Do you have time to review this?

@mdboom I peeked at your new-flags branch in the benchmarking repo. We lose the ability to benchmark Tier 2 on Windows (for now) -- is that reflected in the diff there? (As an only occasional user of the UI there I rely on the script to let me know if I've selected an impossible combination.)

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brandtbucher commented Apr 30, 2024

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@brandtbucher Do you have time to review this?

Yep, looking at it now.

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brandtbucher reviewed

Apr 30, 2024

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Thanks for taking the time to tackle this. Performing the surgery after-the-fact definitely seems like a tricky task.

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gvanrossum added 6 commits

April 30, 2024 15:01


          Shorten to --enable-exerimental-jit=yes-off

8276a9a


          Tweak code in test/support/__init__.py without_optimizer()

f950e25


          Fix news blurb

6be70c0


          Fix typo in _opcode.c

fdbe440


          Shut up annoying warning

3c919bb


          Use Py_FatalError for ENTER_EXECUTOR in non-TIER2 build

d5a3ff0

gvanrossum requested a review from markshannon as a code owner

April 30, 2024 22:56

gvanrossum commented Apr 30, 2024

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@brandtbucher I believe I've done everything from your review that I gave a thumbs up, and for everything else I stated a reason.

@mdboom -- At Brandt's suggestion I've shortened the "default off" flag to --enable-experimental-jit=yes-off. I think this has no repercussions for your new-flags branch of the benchmarking repo, but you may want to double-check.

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brandtbucher approved these changes

Apr 30, 2024

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@brandtbucher I believe I've done everything from your review that I gave a thumbs up, and for everything else I stated a reason.

Yep!

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bedevere-app Bot added awaiting merge and removed awaiting core review labels

Apr 30, 2024

gvanrossum added 2 commits

April 30, 2024 17:02


          Add --experimental-jit-{off|interpreter} to PCbuild/build.bat

07c485e


          Revert "Shut up annoying warning"

a2d4f30

Apparently makes the CI fuzzer unhappy.

This reverts commit 3c919bb.

gvanrossum commented May 1, 2024

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Okay, I've got the Windows flag stuff sorted out. It's a little different from Unix, because you apparently can't say "--experimental-jit=yes-off" while also supporting "--experimental-jit"; it treats the "=" as a space. Rather than becoming a .BAT file CLI parsing expert I chose the following option names:

--experimental-jit
--experimental-jit-off (build JIT, but default off)
--experimental-interpreter
--experimental-interpreter-off (undocumented, for Mark :-)

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gvanrossum merged commit 7d83f7b into python:main

May 1, 2024

bedevere-app Bot removed the awaiting merge label

May 1, 2024

gvanrossum deleted the tier2-flag branch

May 1, 2024 01:26

gvanrossum added a commit to gvanrossum/cpython that referenced this pull request

May 1, 2024


          Also patch up news blurb for pythongh-118339

bd54618

gvanrossum added a commit that referenced this pull request

May 1, 2024


          gh-118335: Make REGEN_JIT_COMMAND empty if tier2 interpreter enabled (#…

a524152

…118493)

Also patch up news blurb for gh-118339
(add warning that PYTHON_UOPS is now PYTHON_JIT).

SonicField pushed a commit to SonicField/cpython that referenced this pull request

May 8, 2024


          pythongh-118335: Configure Tier 2 interpreter at build time (python#1…

…18339)

The code for Tier 2 is now only compiled when configured
with `--enable-experimental-jit[=yes|interpreter]`.

We drop support for `PYTHON_UOPS` and -`Xuops`,
but you can disable the interpreter or JIT
at runtime by setting `PYTHON_JIT=0`.
You can also build it without enabling it by default
using `--enable-experimental-jit=yes-off`;
enable with `PYTHON_JIT=1`.

On Windows, the `build.bat` script supports
`--experimental-jit`, `--experimental-jit-off`,
`--experimental-interpreter`.

In the C code, `_Py_JIT` is defined as before
when the JIT is enabled; the new variable
`_Py_TIER2` is defined when the JIT *or* the
interpreter is enabled. It is actually a bitmask:
1: JIT; 2: default-off; 4: interpreter.

SonicField pushed a commit to SonicField/cpython that referenced this pull request

May 8, 2024


          pythongh-118335: Make REGEN_JIT_COMMAND empty if tier2 interpreter en…

122867b

…abled (python#118493)

Also patch up news blurb for pythongh-118339
(add warning that PYTHON_UOPS is now PYTHON_JIT).

brandtbucher added the topic-JIT label

May 31, 2024

mdboom mentioned this pull request

Jul 2, 2024

gh-121263: Macro-ify most stackref functions for MSVC #121270

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gvanrossum commented Apr 27, 2024 •

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gvanrossum commented Apr 27, 2024 •

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