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xic-rs

An (extended) compiler for the Xi++ programming language, based on the language specification and assignments from Cornell's CS 4120 spring 2019 website. The relevant documents are in the docs directory.

Language Features

  • Object-oriented
  • Class inheritance and subtyping
  • Dynamic dispatch
  • Integer, array, and product (object) types
  • C++ style duck-typed function and class templates
  • C++ style header files
  • Global static variables

Compiler Features

  • Six-ish intermediate representations

    • Abstract syntax tree (AST): close to source language, preserves span information for error messages
    • High intermediate representation (HIR): desugared AST, arbitrarily nested trees of expressions and statements
    • Low intermediate representation (LIR): sequence of top-level statements with arbitrarily nested sub-expressions, generic over conditional branch (jump to label or fall through on false)
    • Abstract assembly: subset of x86-64, generic over temporary or register operands
  • HIR and LIR interpreters

  • (Dubious) macro-based domain-specific languages for LIR, HIR, assembly:

    hir::Function {
      name: symbol::intern_static(abi::XI_MEMDUP),
      linkage: ir::Linkage::LinkOnceOdr,
      statement: hir!(
          (SEQ
              (MOVE
                  (TEMP bound)
                  (ADD (MUL (MEM (TEMP arguments[0])) (CONST abi::WORD)) (CONST abi::WORD)))
              (MOVE (TEMP address) (CALL (NAME abi::XI_ALLOC) (Temporary::fresh_returns(1)) (TEMP bound)))
              (MOVE (TEMP offset) (CONST 0))
              (LABEL r#while)
              (MOVE
                  (MEM (ADD (TEMP address) (TEMP offset)))
                  (MEM (ADD (TEMP arguments[0]) (TEMP offset))))
              (MOVE (TEMP offset) (ADD (TEMP offset) (CONST abi::WORD)))
              (CJUMP (GE (TEMP offset) (TEMP bound)) done r#while)
              (LABEL done)
              (RETURN (TEMP address)))
      ),
      arguments,
      returns: 1,
    }
  • Nice error messages via ariadne:

    >> xic tests/check/bad_incomplete_class_1.xi
    Error: Semantic error
      ╭─[./tests/check/bad_incomplete_class_1.xi:1:1]
      │
    1 │ class A {}
      · ─────┬────
      ·      ╰────── Class A does not implement method required in interface
      │
      ├─[./tests/check/bad_incomplete_class_1.ixi:2:5]
      │
    2 │     foo(): int
      ·     ─┬─
      ·      ╰─── Method required here
    ───╯
    
  • Correctness

    • Suite of ~5000 snapshot tests via insta
    • UI testing of lexer, parser, type checker errors
    • Manual testing of Qt examples
    • Property testing of behavior equivalence across optimizations and interpreters
    • Working solutions for some Advent of Code problems
  • Optimization

  • Debugging

    • Optimization effects logged via pretty_env_logger

    • graphviz-based rendering of dataflow solutions:

      >> cat tests/suite/analyze/snapshots/suite__analyze__copy_propagation__partially_overwritten_tree.snap
      ---
      source: tests/suite/analyze/copy_propagation.rs
      assertion_line: 90
      expression: copy_propagation(function)
      ---
      
          partially_overwritten_tree
      
      +----------------------------------+
      |              enter:              |
      | {}                               |
      | mov _a, _b                       |
      | {_a: _b}                         |
      | mov _d, _a                       |
      | {_a: _b, _d: _a}                 |
      | mov _c, _b                       |
      | {_a: _b, _d: _a, _c: _b}         |
      | mov _e, _c                       |
      | {_a: _b, _d: _a, _c: _b, _e: _c} |
      | mov _a, 1                        |
      | {_e: _c, _c: _b}                 |
      | jmp exit                         |
      | {_e: _c, _c: _b}                 |
      +----------------------------------+
        |
        |
        v
      +----------------------------------+
      |              exit:               |
      | {_e: _c, _c: _b}                 |
      | ret                              |
      | {_e: _c, _c: _b}                 |
      +----------------------------------+
      
    • Custom rendering of live variable ranges:

      >> cat tests/suite/analyze/snapshots/suite__analyze__live_variables__everything_is_meaningless_except_call-2.snap
      ---
      source: tests/suite/analyze/live_variables.rs
      assertion_line: 198
      expression: live_ranges
      ---
      rsp          enter:
      ┊              mov _x, 1
      ┊   _x         mov _y, 2
      ┊   |   _y     add _x, _y
      ┊   |   |      add _y, _x
      ┊   ●   |      mov rdi, _x
      ┊   rdi ●      mov rsi, _y
      ┊   ●   rsi    call black_box
      ┊              add _x, _y
      ┊              add _y, _x
      ┊            exit:
      C              ret
      

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Compiler for the Xi++ programming language

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