51fc725117
Added a new, experimental, tracing optimizer and interpreter (a.k.a. "tier 2"). This currently pessimizes, so don't use yet -- this is infrastructure so we can experiment with optimizing passes. To enable it, pass ``-Xuops`` or set ``PYTHONUOPS=1``. To get debug output, set ``PYTHONUOPSDEBUG=N`` where ``N`` is a debug level (0-4, where 0 is no debug output and 4 is excessively verbose). All of this code is likely to change dramatically before the 3.13 feature freeze. But this is a first step.
1.6 KiB
Tooling to generate interpreters
Documentation for the instruction definitions in Python/bytecodes.c
("the DSL") is here.
What's currently here:
lexer.py: lexer for C, originally written by Mark Shannonplexer.py: OO interface on top of lexer.py; main class:PLexerparser.py: Parser for instruction definition DSL; main classParsergenerate_cases.py: driver script to readPython/bytecodes.cand writePython/generated_cases.c.h(and several other files)test_generator.py: tests, require manual running usingpytest
Note that there is some dummy C code at the top and bottom of
Python/bytecodes.c
to fool text editors like VS Code into believing this is valid C code.
A bit about the parser
The parser class uses a pretty standard recursive descent scheme,
but with unlimited backtracking.
The PLexer class tokenizes the entire input before parsing starts.
We do not run the C preprocessor.
Each parsing method returns either an AST node (a Node instance)
or None, or raises SyntaxError (showing the error in the C source).
Most parsing methods are decorated with @contextual, which automatically
resets the tokenizer input position when None is returned.
Parsing methods may also raise SyntaxError, which is irrecoverable.
When a parsing method returns None, it is possible that after backtracking
a different parsing method returns a valid AST.
Neither the lexer nor the parsers are complete or fully correct.
Most known issues are tersely indicated by # TODO: comments.
We plan to fix issues as they become relevant.