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GeezerVison is showing github.com — GH-98831: Add DECREF_INPUTS(), expanding to DECREF() each stack input by gvanrossum · Pull Request #100205 · python/cpython

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@gvanrossum

@gvanrossum gvanrossum commented Dec 13, 2022 •
edited by bedevere-bot
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The presence of this macro indicates that a particular instruction may be considered for conversion to a register-based format (see faster-cpython/ideas#485).

An invariant (currently unchecked) is that DEOPT_IF() may only occur before DECREF_INPUTS(), and ERROR_IF() may only occur after it. One reason not to check this is that there are a few places where we insert two DECREF_INPUTS() calls, in different branches of the code. The invariant checking would have to be able to do some flow control analysis to understand this.

Note that many instructions, especially specialized ones, can't be converted to use this macro straightforwardly. This is because the generator currently only generates plain Py_DECREF(variable) statements, and cannot generate things like _Py_DECREF_SPECIALIZED() let alone deal with _PyList_AppendTakeRef().

  • Issue: Generate the interpreter #98831

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@gvanrossum
Add DECREF_INPUTS(), expanding to DECREF() each stack input
beaea61
The presence of this macro indicates that a particular instruction
may be considered for conversion to a register-based format
(see faster-cpython/ideas#485).

An invariant (currently unchecked) is that `DEOPT_IF()` may only
occur *before* `DECREF_INPUTS()`, and `ERROR_IF()` may only occur
*after* it. One reason not to check this is that there are a few
places where we insert *two* `DECREF_INPUTS()` calls, in different
branches of the code. The invariant checking would have to be able
to do some flow control analysis to understand this.

Note that many instructions, especially specialized ones,
can't be converted to use this macro straightforwardly.
This is because the generator currently only generates plain
`Py_DECREF(variable)` statements, and cannot generate
things like `_Py_DECREF_SPECIALIZED()` let alone deal with
`_PyList_AppendTakeRef()`.
@gvanrossum
gvanrossum requested a review from iritkatriel December 13, 2022 01:11
@bedevere-bot bedevere-bot mentioned this pull request Dec 13, 2022
Generate the interpreter #98831
Closed
@bedevere-bot bedevere-bot added the awaiting core review label Dec 13, 2022
@gvanrossum

gvanrossum commented Dec 13, 2022

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Some thoughts about how the code would change for the register VM (to be done in a future PR):

  • We need a separate way to mark an instruction as register-based in the DSL input, maybe register inst(NAME, ...)
  • A register-based instruction may have at most three stack effects (inputs and outputs) in total, assigned to oparg, oparg2, and oparg3
  • For those instructions, DECREF_INPUTS() expands to nothing
  • The preamble would assign each input an oparg and then generate code to initialize the variable using fast_locals[opargN] instead of using PEEK(N)
  • The postamble assigns the output variable the next oparg and writes it using Py_SETREF(fast_locals[opargN], variable)
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@iritkatriel

iritkatriel commented Dec 13, 2022

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  • A register-based instruction may have at most three stack effects (inputs and outputs) in total, assigned to oparg, oparg2, and oparg3

Should we make it oparg1, oparg2, oparg3? (oparg can stay for now, for "legacy" instructions that were not converted yet).

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@python python deleted a comment from netlify Bot Dec 13, 2022
@gvanrossum gvanrossum added the skip news label Dec 13, 2022
@gvanrossum

gvanrossum commented Dec 15, 2022

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I was hoping you'd review this PR, @iritkatriel. We can work on the 'register inst' syntax next.

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iritkatriel
iritkatriel approved these changes Dec 15, 2022
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@bedevere-bot bedevere-bot added awaiting merge and removed awaiting core review labels Dec 15, 2022
@gvanrossum
gvanrossum merged commit 9cdd2fa into python:main Dec 17, 2022
@bedevere-bot bedevere-bot removed the awaiting merge label Dec 17, 2022
@gvanrossum
gvanrossum deleted the decref-inputs branch December 17, 2022 04:46
gvanrossum added a commit to gvanrossum/cpython that referenced this pull request Dec 17, 2022
@gvanrossum
pythonGH-98831: Add DECREF_INPUTS(), expanding to DECREF() each stack…
6b82c8d
… input (python#100205)

The presence of this macro indicates that a particular instruction
may be considered for conversion to a register-based format
(see faster-cpython/ideas#485).

An invariant (currently unchecked) is that `DEOPT_IF()` may only
occur *before* `DECREF_INPUTS()`, and `ERROR_IF()` may only occur
*after* it. One reason not to check this is that there are a few
places where we insert *two* `DECREF_INPUTS()` calls, in different
branches of the code. The invariant checking would have to be able
to do some flow control analysis to understand this.

Note that many instructions, especially specialized ones,
can't be converted to use this macro straightforwardly.
This is because the generator currently only generates plain
`Py_DECREF(variable)` statements, and cannot generate
things like `_Py_DECREF_SPECIALIZED()` let alone deal with
`_PyList_AppendTakeRef()`.
@gvanrossum gvanrossum mentioned this pull request Dec 17, 2022
Enhance generator for register instructions iritkatriel/cpython#48
Merged
shihai1991 added a commit to shihai1991/cpython that referenced this pull request Dec 18, 2022
@shihai1991
Merge remote-tracking branch 'origin/main' into bpo_34697
2878571
* origin/main: (1306 commits)
  Correct CVE-2020-10735 documentation (python#100306)
  pythongh-100272: Fix JSON serialization of OrderedDict (pythonGH-100273)
  pythongh-93649: Split tracemalloc tests from _testcapimodule.c (python#99551)
  Docs: Use `PY_VERSION_HEX` for version comparison (python#100179)
  pythongh-97909: Fix markup for `PyMethodDef` members (python#100089)
  pythongh-99240: Reset pointer to NULL when the pointed memory is freed in argument parsing (python#99890)
  pythongh-99240: Reset pointer to NULL when the pointed memory is freed in argument parsing (python#99890)
  pythonGH-98831: Add DECREF_INPUTS(), expanding to DECREF() each stack input (python#100205)
  pythongh-78707: deprecate passing >1 argument to `PurePath.[is_]relative_to()` (pythonGH-94469)
  pythongh-99540: Constant hash for _PyNone_Type to aid reproducibility (pythonGH-99541)
  pythongh-100039: enhance __signature__ to work with str and callables (pythonGH-100168)
  pythongh-99830: asyncio: Document returns of remove_{reader,writer} (python#100302)
  "Compound statement" docs: Fix with-statement step indexing (python#100286)
  pythonGH-90043: Handle NaNs in COMPARE_OP_FLOAT_JUMP (pythonGH-100278)
  Improve stats presentation for calls. (pythonGH-100274)
  Better stats for `LOAD_ATTR` and `STORE_ATTR` (pythonGH-100295)
  pythongh-81057: Move the Cached Parser Dummy Name to _PyRuntimeState (python#100277)
  Document that zipfile's pwd parameter is a `bytes` object (python#100209)
  pythongh-99767: mark `PyTypeObject.tp_watched` as internal use only in table (python#100271)
  Fix typo in introduction.rst (python#100266)
  ...
carljm added a commit to carljm/cpython that referenced this pull request Dec 19, 2022
@carljm
Merge branch 'main' into fastmock
a9af20a
* main:
  pythongh-89727: Fix os.walk RecursionError on deep trees (python#99803)
  Docs: Don't upload CI artifacts (python#100330)
  pythongh-94912: Added marker for non-standard coroutine function detection (python#99247)
  Correct CVE-2020-10735 documentation (python#100306)
  pythongh-100272: Fix JSON serialization of OrderedDict (pythonGH-100273)
  pythongh-93649: Split tracemalloc tests from _testcapimodule.c (python#99551)
  Docs: Use `PY_VERSION_HEX` for version comparison (python#100179)
  pythongh-97909: Fix markup for `PyMethodDef` members (python#100089)
  pythongh-99240: Reset pointer to NULL when the pointed memory is freed in argument parsing (python#99890)
  pythongh-99240: Reset pointer to NULL when the pointed memory is freed in argument parsing (python#99890)
  pythonGH-98831: Add DECREF_INPUTS(), expanding to DECREF() each stack input (python#100205)
  pythongh-78707: deprecate passing >1 argument to `PurePath.[is_]relative_to()` (pythonGH-94469)
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@gvanrossum @iritkatriel @bedevere-bot
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