hakorune/CURRENT_TASK.md

Current Task — Phase 15 Self‑Hosting (2025‑09‑17)

Summary

• Default execution is MIR13 (PHI‑off). Bridge/Builder do not emit PHIs; llvmlite synthesizes PHIs when needed. MIR14 (PHI‑on) remains experimental for targeted tests.
• PyVM is the semantic reference engine; llvmlite is used for AOT and parity checks.

What Changed (recent)

• MIR13 default enabled
  • mir_no_phi() default set to true (can disable via NYASH_MIR_NO_PHI=0).
  • Curated LLVM runner defaults to PHI‑off; --phi-on enables MIR14 lane.
  • Added doc: docs/development/mir/MIR13_MODE.md; README references it.
• JSON v0 Bridge lowering split (non‑functional)
  • Added src/runner/json_v0_bridge/lowering/{if_else.rs, loop_.rs, try_catch.rs, merge.rs} and routed calls from lowering.rs.
• llvmlite stability for MIR13
  • Resolver: forbids cross‑block non‑dominating vmap reuse; for multi‑pred and no declared PHI, synthesizes a localization PHI at block head.
  • Finalize remains function‑local; block_end_values snapshots and placeholder wiring still in place.
• Parity runner pragmatics
  • tools/pyvm_vs_llvmlite.sh compares exit code by default; use CMP_STRICT=1 for stdout+exit.

Current Status

• Self‑hosting Bridge → PyVM smokes: PASS (Stage‑2 reps: array/string/logic/if/loop).
• Curated LLVM (PHI‑off default): PASS.
• Curated LLVM (PHI‑on experimental): apps/tests/loop_if_phi.nyash shows a dominance issue (observed; not blocking, MIR13 recommended).

Next (short plan)

1. JSON v0 lowering: split remaining helpers (peek/ternary/expr) without behavior change.
2. PHI‑on lane (optional): investigate loop_if_phi dominance by tightening finalize ordering and resolver materialization (low priority).
3. Runner refactor (small PRs):
   • selfhost/{child.rs,json.rs} split; modes/common/{io,resolve,exec}.rs split; reduce runner/mod.rs surface.
4. Optimizer/Verifier thin‑hub cleanup (non‑functional): orchestrator minimalization and pass boundaries clarified.

How to Run

• PyVM reference smokes: tools/pyvm_stage2_smoke.sh
• Bridge → PyVM smokes: tools/selfhost_stage2_bridge_smoke.sh
• LLVM curated (PHI‑off default): tools/smokes/curated_llvm.sh
• LLVM PHI‑on (experimental): tools/smokes/curated_llvm.sh --phi-on
• Parity (AOT vs PyVM): tools/pyvm_vs_llvmlite.sh <file.nyash> (CMP_STRICT=1 to enable stdout check)

Key Flags

• NYASH_MIR_NO_PHI (default 1): PHI‑off when 1 (MIR13). Set 0 for PHI‑on.
• NYASH_VERIFY_ALLOW_NO_PHI (default 1): relax verifier for PHI‑less MIR.
• NYASH_LLVM_USE_HARNESS=1: route AOT through llvmlite harness.
• NYASH_LLVM_TRACE_PHI=1: trace PHI resolution/wiring.

Notes / Policies

• Focus is self‑hosting stability. JIT/Cranelift is out of scope (safety fixes only).
• PHI generation remains centralized in llvmlite; Bridge/Builder keep PHI‑off by default.
• No full tracing GC yet; handles/Arc lifetimes govern object retention. Safepoint/barrier/roots are staging utilities.