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hakorune/docs/LOWERING_LLVM.md
Selfhosting Dev 89e6fbf010 feat(llvm): Comprehensive LLVM backend improvements by ChatGPT 
Major enhancements to LLVM code generation and type handling:

1. String Operations:
   - Added StringBox length fast-path (length/len methods)
   - Converts i8* to handle when needed for len_h call
   - Consistent handle-based string operations

2. Array/Map Fast-paths:
   - ArrayBox: get/set/push/length operations
   - MapBox: get/set/has/size with handle-based keys
   - Optimized paths for common collection operations

3. Field Access:
   - getField/setField implementation with handle conversion
   - Proper i64 handle to pointer conversions

4. NewBox Improvements:
   - StringBox/IntegerBox pass-through optimizations
   - Fallback to env.box.new when type_id unavailable
   - Support for dynamic box creation

5. Documentation:
   - Added ARCHITECTURE.md for overall design
   - Added EXTERNCALL.md for external call specs
   - Added LOWERING_LLVM.md for LLVM lowering rules
   - Added PLUGIN_ABI.md for plugin interface

6. Type System:
   - Added UserBox type registration in nyash_box.toml
   - Consistent handle (i64) representation across system

Results: More robust LLVM code generation with proper type handling

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>
2025-09-11 22:30:26 +09:00

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LLVM Lowering Rules (Phase 15)

This document describes the active LLVM lowering rules used in Phase 15. Only the LLVM path is authoritative at this time.

General

  • Box values are represented as i64 handles when crossing the NyRT boundary.
  • String operations prefer i8* fast paths (AOT helpers) when possible. Handle conversions are done only at explicit boundaries.

NewBox

  • StringBox:
    • When constructed from a constant string, lowering produces i8* via nyash_string_new and keeps it as i8* (no immediate handle conversion).
    • Builder skips redundant birth calls for StringBox.
  • Other boxes:
    • Minimal birth shims exist (e.g., nyash.box.birth_h, nyash.box.birth_i64) using Box type ids.

BoxCall: String.concat fast path

  • If the receiver is annotated as String (or StringBox), lower to AOT helpers directly:
    • concat_ss(i8*, i8*) -> i8*
    • concat_si(i8*, i64) -> i8* (right operand is a handle coerced to string by NyRT)
    • concat_is(i64, i8*) -> i8*
  • For non‑String receivers or plugin cases, fall back to plugin/by‑id paths as needed.

BinOp Add: String concatenation

  • Primary path: AOT helpers selected by operand shapes at IR time:
    • i8* + i8* -> concat_ss
    • i8* + i64 -> concat_si
    • i64 + i8* -> concat_is
  • Fallback policy: keep to the minimum. Do not add implicit conversions beyond the above without clear MIR type annotations. If mixed forms miscompile, fix MIR annotations first.

ExternCall selection (console/debug)

  • env.console.{log,warn,error} and env.debug.trace inspect the argument at lowering time:
    • If argument is i8*, call the C‑string variant: nyash.console.{log,warn,error} / nyash.debug.trace.
    • Otherwise convert to i64 and call the handle variant: nyash.console.{log,warn,error}_handle / nyash.debug.trace_handle.
  • The result values are ignored or zeroed as appropriate (side‑effecting I/O).

Return/Result mapping

  • For plugin/by‑id calls that return an i64 handle but the destination is annotated as pointer‑like (String/Box/Array/Future/Unknown), the handle is cast to an opaque pointer for SSA flow. Integers/Bools remain integers.

Backend Consistency Notes

  • VM/Cranelift/JIT are not MIR14‑ready and may not follow these rules yet. LLVM behavior takes precedence; other backends will be aligned later.
  • Any new fallback must be justified and scoped; wide catch‑alls are prohibited to prevent backend divergence.