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cpython/Tools/cases_generator
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Guido van Rossum b3648f036e
gh-104584: Allow unspecialized instructions in superblocks (#106497) 
This adds several of unspecialized opcodes to superblocks:

TO_BOOL, BINARY_SUBSCR, STORE_SUBSCR,
UNPACK_SEQUENCE, LOAD_GLOBAL, LOAD_ATTR,
COMPARE_OP, BINARY_OP.

While we may not want that eventually, for now this helps finding bugs.

There is a rudimentary test checking for UNPACK_SEQUENCE.

Once we're ready to undo this, that would be simple:
just replace the call to variable_used_unspecialized
with a call to variable_used (as shown in a comment).
Or add individual opcdes to FORBIDDEN_NAMES_IN_UOPS.
2023-07-07 18:03:27 +00:00
..
generate_cases.py gh-104584: Allow unspecialized instructions in superblocks (#106497) 2023-07-07 18:03:27 +00:00
interpreter_definition.md Update DSL docs for cases generator (#105753) 2023-06-14 08:19:24 -07:00
lexer.py gh-106200: Remove unused imports (#106201) 2023-06-28 11:55:41 +00:00
parser.py Remove support for legacy bytecode instructions (#105705) 2023-06-12 18:19:04 +00:00
plexer.py GH-98831: Refactor and fix cases generator (#99526) 2022-11-17 17:06:07 -08:00
README.md gh-104584: Baby steps towards generating and executing traces (#105924) 2023-06-26 19:02:57 -07:00
test_generator.py gh-104584: Baby steps towards generating and executing traces (#105924) 2023-06-26 19:02:57 -07:00

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 (and several other files)
  • 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.