82 lines
3.9 KiB
Markdown
82 lines
3.9 KiB
Markdown
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# Phase 11.7 – JIT Complete Plan (Cranelift)
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Goal
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- Ship a complete JIT backend (Cranelift) for MIR Core‑15 with Semantics layer as the single source of truth, GC sync/async support, and full Box/Extern integration. Keep DX simple and cross‑platform.
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Milestones
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1) Bootstrap (Infra + Skeleton)
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- Add backend module: `src/backend/cranelift/{mod.rs,context.rs,lower.rs,jit.rs,object.rs}`
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- Context: host ISA, FunctionBuilder, Module (JIT/Object) setup helpers
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- Runner: `--backend cranelift` execution path; feature flag reuse (`cranelift-jit`)
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- Minimal ops: Const i64/f64/bool/null/string → CLIF values; Return; straight‑line add/sub
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- Smoke: `apps/tests/ny-echo-lite` returns 0 via JIT
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2) Core MIR‑15 Lowering (Parity with VM)
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- Control: Jump/Branch/Phi, Load/Store (alloca on entry; i1↔i64 widen/narrow)
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- Unary/Binary/Compare: int/float/ptr eq/ne; logical and/or via to_bool
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- TypeOp (when needed) + pointer/int casts (handle→i64/i8* via ABI helpers)
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- Strings: concat via NyRT shims (`nyash.string.concat_*`)
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- BoxCall (by‑id): fixed/tagged args (<=4) + vector path; handle‑first returns (i64/ptr)
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- ExternCall: `env.console.*`, `env.debug.trace`, `console.readLine` via NyRT shims
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- Smokes: array/map/vinvoke(size/ret), echo; compare outputs with VM
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3) GC Cooperation
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- Sync barriers: insert read/write barriers at Load/Store & NewBox as per VM semantics
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- Async safepoints: at call sites/loop backedges; NyRT entry glue to yield if required
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- Tests: targeted barrier smoke (array/map mutations) + perf sanity (no excessive barriers)
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4) Parity + Stability
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- UnsupportedLegacyInstruction: maintain strict mode; allow env override for debug
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- Error reporting: source op pretty‑print, MIR value ids in error messages
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- Logging: `NYASH_CLI_VERBOSE=1` shows JIT compile stages + object sizes (optional)
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- Doc/Doctor script: `tools/doctor.ps1`/`.sh` for quick env checks (optional nice‑to‑have)
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5) AOT (Optional within 11.7 if time)
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- `cranelift-object` emit: `.o` for main; link with NyRT → exe (`tools/build_cl.*`)
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- Windows: clang/lld link; Linux: cc link; parity with LLVM’s scripts
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Instruction Coverage (MIR Core‑15)
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- Const, UnaryOp, BinOp, Compare, TypeOp
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- Load, Store, Phi, Jump, Branch, Return
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- Call, NewBox, BoxCall, ExternCall
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ABI & Shims
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- Handle‑first: receiver/values normalized to i64; ptr/int casts via helpers
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- NyRT shims used: `nyash.console.*`, `nyash.debug.trace`, `nyash.console.readline`,
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`nyash_string_new`, `nyash.string.concat_*`, `nyash_array_*_h`, `nyash.instance.*_h`,
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plugin invoke (by‑id tagged, vector variants)
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Semantics Integration (new in 11.7)
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- Add `Semantics` trait as unified MIR semantics API.
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- Provide `SemanticsVM` (exec) and `SemanticsClif` (lower) so the same MIR walks yield identical behavior across VM and JIT.
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- Use `semantics::MirInterpreter` for parity tests; prefer zero‑cost abstractions with static dispatch.
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Status Notes (2025‑09‑01)
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- LLVM AOT: closed for now due to Windows dependency weight; Cranelift is the mainline.
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- VM: safepoint/barrier/scheduler wired and observable (CountingGc).
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- JIT: `nyash.rt.checkpoint`/`nyash.gc.barrier_write` symbols are available via NyRT; LowerCore needs to emit safepoints and barriers; Await lowering pending.
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Deliverables
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- Code: Cranelift backend files + runner integration
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- Tools: build/run scripts for JIT/AOT; updated smokes to exercise CL route
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- Docs: this plan + CURRENT_TASK.md; brief README how to run JIT
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Risks & Mitigations
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- Pointer/int mismatch → normalize via i64/ptr helpers in one place; add asserts
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- Barrier placement overhead → start with conservative placement; measure; trim if safe
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- Windows toolchain variance → Cranelift avoids external LLVM; keep MSVC only
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Timeline (indicative)
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- Week 1: Milestone 1 + 2 (most ops) → basic smokes green
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- Week 2: GC barriers + safepoints, full parity sweep; docs/tools polish
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- Optional: AOT via cl‑object emit & link scripts
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