Progress report in Pen programming language

July 17th, 2022

@raviqqe

Agenda

• Progress report
  • Reference counting optimization
  • C calling convention (no progress)
• Next plans

Progress report

Reference counting optimization

• Fibonacci number is 25% faster than the previous version!
  • Now, it's 2 times slower than Rust... (with floating-pointer numbers)
• Static pointer tagging was preventing direct calls of global functions.
  • Now, Pen uses static counts for statically allocated memory blocks.
  • Pointer tagging and un-tagging were not removed by LLVM's optimization somehow even with correct alignment of global variables.
  • Clang does it but at the level of CIL?
  • Removal of pointer tags also led to simpler static check of memory blocks.

C calling convention (no progress)

• The Zig's developer says: https://twitter.com/andy_kelley/status/1527743699836280833
• LLVM's C calling convention is not the one used by C.
  • Linux on x86 uses the System V ABI.
  • LLVM handles only part of it.
    • Register spilling
    • Struct decomposition
• MLIR has it as C wrapper emission for the LLVM dialect.
  • Not released yet. Maybe in LLVM 15?

C calling convention (no progress, continued)

• C backend again for F--?
  • F-- is Pen's lower-level IR.
  • Currently, C backend doesn't support guaranteed tail call optimization.
  • Clang's musttail needs function signature matching.
    • C's standard proposal also follows the same design for portability.

Next plans

• Standard library improvements
  • More functionality
  • More completeness
• Application development?
  • Web application?
  • WebGL??
  • Currently, tail calls in WASM is only supported by Chrome (and Node.js.)
• Efficient C calling convention in FFI #444
  • Compiling to MLIR? Wait for LLVM 15?

Summary

• Progress
  • Reference counting optimization
• Next plans
  • Standard library improvements
  • Application development?