47 lines
2.3 KiB
Markdown
47 lines
2.3 KiB
Markdown
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# Design Notes – Phase 11.7 JIT Complete (Meeting Summary)
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Date: 2025-09-01
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Key Decisions
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- Single Semantics Source: Introduce a MIR semantics layer (trait) as the single source of truth. All backends (VM/Cranelift/LLVM/WASM) implement this interface.
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- No Runtime Fallback: Remove VM→JIT fallback complexity. VM becomes the reference executor; codegen backends handle execution/AOT. JIT is compile-only/AOT‑assist when needed.
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- Handle‑First ABI: Unify handle/i64/ptr conversions, tag classification, concat/extern/boxcall via shared helpers; call into NyRT shims from backends.
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- GC Hooks: Insert sync barriers and async safepoints as MIR‑level hooks that each backend lowers appropriately.
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- Backends Roadmap: LLVM AOT は一旦アーカイブ。Cranelift を主線（JIT/軽量AOT）とし、WASM は同一セマンティクスで後段。Windows DX を軽く保つ。
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Architecture Sketch
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- MIR → Semantics<E>
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- VmSem: executes values (reference)
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- ClifSem: builds Cranelift IR (JIT/AOT)
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- LlvmSem: builds LLVM IR (AOT)
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- WasmSem: builds Wasm (future)
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- Shared ABI utilities: handle↔i64/ptr, to_bool, compare, tags, invoke variants, NyRT shims.
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Implementation Plan (Progressive)
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- Phase 1: Skeleton + minimal lowering (Const/Return/Add) → echo-lite returns 0 via Cranelift JIT skeleton.
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- Phase 2: Control (Jump/Branch/Phi), Load/Store, Compare, String concat via NyRT, Box/Extern by-id (fixed/vector).
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- Phase 3: GC barriers/safepoints; parity with VM（CountingGc での観測を含む）。
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- Phase 4: Stability, logs, strict/legacy guards; optional AOT via cranelift-object + link scripts.
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Notes from Review
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- Using Semantics trait enables zero‑cost abstractions with static dispatch.
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- Add optional debug hooks (location/value) and optimization hints (likely_branch, pure_function_hint) later.
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- Testing: MockSemantics for unit tests; parity tests VM vs CLIF.
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Action Items
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- Land Semantics trait + minimal MirInterpreter (skeleton added).
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- Implement ClifSem minimal lowering; wire Runner `--backend cranelift`.
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- Centralize ABI helpers; migrate existing scattered logic to shared module.
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- Emit `nyash.rt.checkpoint` and `nyash.gc.barrier_write` from LowerCore at appropriate sites; wire Await (PoC: blocking get).
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- Add build_cl scripts for AOT when ready.
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Links
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- PLAN.md – milestones and coverage
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- CURRENT_TASK.md – immediate focus
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