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GH-98831: "Generate" the interpreter (#98830) The switch cases (really TARGET(opcode) macros) have been moved from ceval.c to generated_cases.c.h. That file is generated from instruction definitions in bytecodes.c (which impersonates a C file so the C code it contains can be edited without custom support in e.g. VS Code). The code generator lives in Tools/cases_generator (it has a README.md explaining how it works). The DSL used to describe the instructions is a work in progress, described in https://github.com/faster-cpython/ideas/blob/main/3.12/interpreter_definition.md. This is surely a work-in-progress. An easy next step could be auto-generating super-instructions. **IMPORTANT: Merge Conflicts** If you get a merge conflict for instruction implementations in ceval.c, your best bet is to port your changes to bytecodes.c. That file looks almost the same as the original cases, except instead of `TARGET(NAME)` it uses `inst(NAME)`, and the trailing `DISPATCH()` call is omitted (the code generator adds it automatically).
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# Tooling to generate interpreters
gh-98831: Move DSL documentation here from ideas repo (#101629)
2023-02-07 01:03:58 -04:00
Documentation for the instruction definitions in `Python/bytecodes.c`
("the DSL") is [here](interpreter_definition.md).
GH-98831: "Generate" the interpreter (#98830) The switch cases (really TARGET(opcode) macros) have been moved from ceval.c to generated_cases.c.h. That file is generated from instruction definitions in bytecodes.c (which impersonates a C file so the C code it contains can be edited without custom support in e.g. VS Code). The code generator lives in Tools/cases_generator (it has a README.md explaining how it works). The DSL used to describe the instructions is a work in progress, described in https://github.com/faster-cpython/ideas/blob/main/3.12/interpreter_definition.md. This is surely a work-in-progress. An easy next step could be auto-generating super-instructions. **IMPORTANT: Merge Conflicts** If you get a merge conflict for instruction implementations in ceval.c, your best bet is to port your changes to bytecodes.c. That file looks almost the same as the original cases, except instead of `TARGET(NAME)` it uses `inst(NAME)`, and the trailing `DISPATCH()` call is omitted (the code generator adds it automatically).
2022-11-03 01:31:26 -03:00
What's currently here:
GH-98831: Add `macro` and `op` and their implementation to DSL (#99495) Newly supported interpreter definition syntax: - `op(NAME, (input_stack_effects -- output_stack_effects)) { ... }` - `macro(NAME) = OP1 + OP2;` Also some other random improvements: - Convert `WITH_EXCEPT_START` to use stack effects - Fix lexer to balk at unrecognized characters, e.g. `@` - Fix moved output names; support object pointers in cache - Introduce `error()` method to print errors - Introduce read_uint16(p) as equivalent to `*p` Co-authored-by: Brandt Bucher <brandtbucher@gmail.com>
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- `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`
GH-98831: "Generate" the interpreter (#98830) The switch cases (really TARGET(opcode) macros) have been moved from ceval.c to generated_cases.c.h. That file is generated from instruction definitions in bytecodes.c (which impersonates a C file so the C code it contains can be edited without custom support in e.g. VS Code). The code generator lives in Tools/cases_generator (it has a README.md explaining how it works). The DSL used to describe the instructions is a work in progress, described in https://github.com/faster-cpython/ideas/blob/main/3.12/interpreter_definition.md. This is surely a work-in-progress. An easy next step could be auto-generating super-instructions. **IMPORTANT: Merge Conflicts** If you get a merge conflict for instruction implementations in ceval.c, your best bet is to port your changes to bytecodes.c. That file looks almost the same as the original cases, except instead of `TARGET(NAME)` it uses `inst(NAME)`, and the trailing `DISPATCH()` call is omitted (the code generator adds it automatically).
2022-11-03 01:31:26 -03:00
- `generate_cases.py`: driver script to read `Python/bytecodes.c` and
write `Python/generated_cases.c.h`
gh-98831: Move DSL documentation here from ideas repo (#101629)
2023-02-07 01:03:58 -04:00
- `test_generator.py`: tests, require manual running using `pytest`
GH-98831: "Generate" the interpreter (#98830) The switch cases (really TARGET(opcode) macros) have been moved from ceval.c to generated_cases.c.h. That file is generated from instruction definitions in bytecodes.c (which impersonates a C file so the C code it contains can be edited without custom support in e.g. VS Code). The code generator lives in Tools/cases_generator (it has a README.md explaining how it works). The DSL used to describe the instructions is a work in progress, described in https://github.com/faster-cpython/ideas/blob/main/3.12/interpreter_definition.md. This is surely a work-in-progress. An easy next step could be auto-generating super-instructions. **IMPORTANT: Merge Conflicts** If you get a merge conflict for instruction implementations in ceval.c, your best bet is to port your changes to bytecodes.c. That file looks almost the same as the original cases, except instead of `TARGET(NAME)` it uses `inst(NAME)`, and the trailing `DISPATCH()` call is omitted (the code generator adds it automatically).
2022-11-03 01:31:26 -03:00
gh-98831: Move DSL documentation here from ideas repo (#101629)
2023-02-07 01:03:58 -04:00
Note that there is some dummy C code at the top and bottom of
`Python/bytecodes.c`
GH-98831: "Generate" the interpreter (#98830) The switch cases (really TARGET(opcode) macros) have been moved from ceval.c to generated_cases.c.h. That file is generated from instruction definitions in bytecodes.c (which impersonates a C file so the C code it contains can be edited without custom support in e.g. VS Code). The code generator lives in Tools/cases_generator (it has a README.md explaining how it works). The DSL used to describe the instructions is a work in progress, described in https://github.com/faster-cpython/ideas/blob/main/3.12/interpreter_definition.md. This is surely a work-in-progress. An easy next step could be auto-generating super-instructions. **IMPORTANT: Merge Conflicts** If you get a merge conflict for instruction implementations in ceval.c, your best bet is to port your changes to bytecodes.c. That file looks almost the same as the original cases, except instead of `TARGET(NAME)` it uses `inst(NAME)`, and the trailing `DISPATCH()` call is omitted (the code generator adds it automatically).
2022-11-03 01:31:26 -03:00
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.