Replace code that directly accesses PyASCIIObject.hash with
PyUnstable_Unicode_GET_CACHED_HASH().
Remove redundant "assert(PyUnicode_Check(op))" from
PyUnstable_Unicode_GET_CACHED_HASH(), _PyASCIIObject_CAST() already
implements the check.
This needs a single bit, but was stored as a void* in the module
struct. This didn't matter due to packing, but now that there's
another bool in the struct, we can save a bit of memory by
making md_gil a bool.
Variables that changed type are renamed, to detect conflicts.
This PR changes the current JIT model from trace projection to trace recording. Benchmarking: better pyperformance (about 1.7% overall) geomean versus current https://raw.githubusercontent.com/facebookexperimental/free-threading-benchmarking/refs/heads/main/results/bm-20251108-3.15.0a1%2B-7e2bc1d-JIT/bm-20251108-vultr-x86_64-Fidget%252dSpinner-tracing_jit-3.15.0a1%2B-7e2bc1d-vs-base.svg, 100% faster Richards on the most improved benchmark versus the current JIT. Slowdown of about 10-15% on the worst benchmark versus the current JIT. **Note: the fastest version isn't the one merged, as it relies on fixing bugs in the specializing interpreter, which is left to another PR**. The speedup in the merged version is about 1.1%. https://raw.githubusercontent.com/facebookexperimental/free-threading-benchmarking/refs/heads/main/results/bm-20251112-3.15.0a1%2B-f8a764a-JIT/bm-20251112-vultr-x86_64-Fidget%252dSpinner-tracing_jit-3.15.0a1%2B-f8a764a-vs-base.svg
Stats: 50% more uops executed, 30% more traces entered the last time we ran them. It also suggests our trace lengths for a real trace recording JIT are too short, as a lot of trace too long aborts https://github.com/facebookexperimental/free-threading-benchmarking/blob/main/results/bm-20251023-3.15.0a1%2B-eb73378-CLANG%2CJIT/bm-20251023-vultr-x86_64-Fidget%252dSpinner-tracing_jit-3.15.0a1%2B-eb73378-pystats-vs-base.md .
This new JIT frontend is already able to record/execute significantly more instructions than the previous JIT frontend. In this PR, we are now able to record through custom dunders, simple object creation, generators, etc. None of these were done by the old JIT frontend. Some custom dunders uops were discovered to be broken as part of this work gh-140277
The optimizer stack space check is disabled, as it's no longer valid to deal with underflow.
Pros:
* Ignoring the generated tracer code as it's automatically created, this is only additional 1k lines of code. The maintenance burden is handled by the DSL and code generator.
* `optimizer.c` is now significantly simpler, as we don't have to do strange things to recover the bytecode from a trace.
* The new JIT frontend is able to handle a lot more control-flow than the old one.
* Tracing is very low overhead. We use the tail calling interpreter/computed goto interpreter to switch between tracing mode and non-tracing mode. I call this mechanism dual dispatch, as we have two dispatch tables dispatching to each other. Specialization is still enabled while tracing.
* Better handling of polymorphism. We leverage the specializing interpreter for this.
Cons:
* (For now) requires tail calling interpreter or computed gotos. This means no Windows JIT for now :(. Not to fret, tail calling is coming soon to Windows though https://github.com/python/cpython/pull/139962
Design:
* After each instruction, the `record_previous_inst` function/label is executed. This does as the name suggests.
* The tracing interpreter lowers bytecode to uops directly so that it can obtain "fresh" values at the point of lowering.
* The tracing version behaves nearly identical to the normal interpreter, in fact it even has specialization! This allows it to run without much of a slowdown when tracing. The actual cost of tracing is only a function call and writes to memory.
* The tracing interpreter uses the specializing interpreter's deopt to naturally form the side exit chains. This allows it to side exit chain effectively, without repeating much code. We force a re-specializing when tracing a deopt.
* The tracing interpreter can even handle goto errors/exceptions, but I chose to disable them for now as it's not tested.
* Because we do not share interpreter dispatch, there is should be no significant slowdown to the original specializing interpreter on tailcall and computed got with JIT disabled. With JIT enabled, there might be a slowdown in the form of the JIT trying to trace.
* Things that could have dynamic instruction pointer effects are guarded on. The guard deopts to a new instruction --- `_DYNAMIC_EXIT`.
Update `bytearray` to contain a `bytes` and provide a zero-copy path to
"extract" the `bytes`. This allows making several code paths more efficient.
This does not move any codepaths to make use of this new API. The documentation
changes include common code patterns which can be made more efficient with
this API.
---
When just changing `bytearray` to contain `bytes` I ran pyperformance on a
`--with-lto --enable-optimizations --with-static-libpython` build and don't see
any major speedups or slowdowns with this; all seems to be in the noise of
my machine (Generally changes under 5% or benchmarks that don't touch
bytes/bytearray).
Co-authored-by: Victor Stinner <vstinner@python.org>
Co-authored-by: Maurycy Pawłowski-Wieroński <5383+maurycy@users.noreply.github.com>
faulthandler now detects if a frame or a code object is invalid or
freed.
Add helper functions:
* _PyCode_SafeAddr2Line()
* _PyFrame_SafeGetCode()
* _PyFrame_SafeGetLasti()
_PyMem_IsPtrFreed() now detects pointers in [-0xff, 0xff] range
as freed.
Move the public PyUnicodeWriter API and the private _PyUnicodeWriter
API to a new Objects/unicode_writer.c file.
Rename a few helper functions to share them between unicodeobject.c
and unicode_writer.c, such as resize_compact() or unicode_result().
Expose `_PyUnicode_IsXidContinue/Start` in `unicodedata`:
add isxidstart() and isxidcontinue() functions.
Co-authored-by: Victor Stinner <vstinner@python.org>
The `make_gen()` function creates and tracks generator/coro objects, but
doesn't fully initialize all the fields. At a minimum, we need to
initialize all the fields that may be accessed by gen_traverse because
the call to `compute_cr_origin()` can trigger a GC.
Currently, there are a few places where tp_mro could theoretically
become NULL, but do not in practice. This commit adds defensive checks for
NULL values to ensure that any changes do not introduce a crash and that
state invariants are upheld.
The assertions added in this commit are all instances where a NULL value would get passed to something not expecting a NULL, so it is better to catch an assertion failure than crash later on.
There are a few cases where it is OK for the return of lookup_tp_mro to be NULL, such as when passed to is_subtype_with_mro, which handles this explicitly.
* Count number of actually tracked objects, instead of trackable objects. This ensures that untracking tuples has the desired effect of reducing GC overhead
* Do not track most untrackable tuples during creation. This prevents large numbers of small tuples causing execessive GCs.
The previous `Py_REFCNT(x) == 1` checks can have data races in the free
threaded build. `_PyObject_IsUniquelyReferenced(x)` is a more conservative
check that is safe in the free threaded build and is identical to
`Py_REFCNT(x) == 1` in the default GIL-enabled build.
* Move PyUnicode_Format() implementation from unicodeobject.c
to unicode_format.c.
* Replace unicode_modifiable() with _PyUnicode_IsModifiable()
* Add empty lines to have two empty lines between functions.
* Move Python/formatter_unicode.c to Objects/unicode_formatter.c.
* Move Objects/stringlib/localeutil.h content into
unicode_formatter.c. Remove localeutil.h.
* Move _PyUnicode_InsertThousandsGrouping() to unicode_formatter.c
and mark the function as static.
* Rename unicode_fill() to _PyUnicode_Fill() and export it in
pycore_unicodeobject.h.
* Move MAX_UNICODE to pycore_unicodeobject.h as _Py_MAX_UNICODE.
Replace PyBytes_FromStringAndSize() and _PyBytes_Resize() with the
PyBytesWriter API.
Add _PyBytesWriter_GetSize() and _PyBytesWriter_GetData() static
inline functions.
