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Guido van Rossum 65b7b6bd23
gh-98831: Use opcode metadata for stack_effect() (#101704) 
* Write output and metadata in a single run
  This halves the time to run the cases generator
  (most of the time goes into parsing the input).
* Declare or define opcode metadata based on NEED_OPCODE_TABLES
* Use generated metadata for stack_effect()
* compile.o depends on opcode_metadata.h
* Return -1 from _PyOpcode_num_popped/pushed for unknown opcode
 		2023-02-08 16:23:19 -08:00
..
README.md gh-98831: Move DSL documentation here from ideas repo (#101629) 2023-02-06 21:03:58 -08:00
generate_cases.py gh-98831: Use opcode metadata for stack_effect() (#101704) 2023-02-08 16:23:19 -08:00
interpreter_definition.md gh-98831: Move DSL documentation here from ideas repo (#101629) 2023-02-06 21:03:58 -08:00
lexer.py GH-98831: Support cache effects in super- and macro instructions (#99601) 2022-12-02 19:57:30 -08:00
parser.py gh-98831: Modernize FORMAT_VALUE (#101628) 2023-02-07 17:35:55 -08:00
plexer.py GH-98831: Refactor and fix cases generator (#99526) 2022-11-17 17:06:07 -08:00
test_generator.py gh-98831: Modernize CALL_FUNCTION_EX (#101627) 2023-02-07 20:03:22 -08:00

README.md

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 Shannon
  • plexer.py: OO interface on top of lexer.py; main class: PLexer
  • parser.py: Parser for instruction definition DSL; main class Parser
  • generate_cases.py: driver script to read Python/bytecodes.c and write Python/generated_cases.c.h
  • test_generator.py: tests, require manual running using pytest

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.