Skip to content

Phase 3: MIR + LLVM Codegen Implementation Plan

For agentic workers: REQUIRED SUB-SKILL: Use superpowers:subagent-driven-development or superpowers:executing-plans.

Goal: Lower typed AST to MIR, optimize lightly, emit LLVM IR, link native binary via lic build.

Architecture: li_mir defines MIR ops; li_codegen lowers MIR → LLVM; driver shells out to clang for link.

Tech Stack: inkwell, clang

Depends on: Phase 2
Blocks: Phase 4

MIR instruction set (v1)

mir_fn ::= fn name(params) -> ret { basic_blocks }
bb     ::= label: mir_inst*
inst   ::= assign dest, operand
         | binop dest, op, lhs, rhs
         | br cond, then_bb, else_bb
         | jmp bb
         | ret operand?
         | call dest?, fn, args…
         | load_field / store_field
         | load_index / store_index (with bounds check call)
         | panic_if_oob index, len

Task 1: MIR data structures

Files: - Create: crates/li_mir/src/lib.rs - Create: crates/li_mir/src/lower.rs

  • lower_module(TypedModule) -> MirModule
  • One basic block per stmt chain; if/while create CFG edges

Task 2: MIR → LLVM

Files: - Modify: crates/li_codegen/src/lib.rs - Create: crates/li_codegen/src/mir_llvm.rs

  • Map MIR types to LLVM types (array → struct or stack array)
  • Emit main calling user main if present
  • Debug: li_bounds_fail call on dynamic index

Task 3: Driver lic build

Files: - Modify: crates/lic/src/main.rs - Create: crates/lic/src/driver.rs

  • lic build input.li -o out [--release]
  • Pipeline: parse → check → mir → llvm bitcode → clang -o out
  • Link runtime/li_rt.c

Task 4: End-to-end hello

Files: - Create: examples/hello.li

proc main() raises IO =
  echo "hello li"
  • Deferred until Phase 4 provides echo — for Phase 3 use:
proc main() -> int =
  return 0
  • lic build examples/hello.li -o hello && ./hello; echo $? → 0

Task 5: Snapshot tests

Files: - Create: crates/li_codegen/tests/llvm_snap.rs

  • insta snapshot of LLVM IR for return 0 program

Phase 3 exit gate

  • Native binary from minimal proc
  • -O2 flag forwarded to clang in --release
  • Bounds check calls present in IR for dynamic index