2025-09-19 02:07:38 +09:00
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# PHI Observability and Trace Checking (Draft)
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Motivation
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- SSA construction bugs are subtle. We want a first‑class, machine‑checkable record of PHI decisions.
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Approach
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- Emit structured JSONL events across PHI lifecycle: `finalize_begin`, `finalize_dst`, `finalize_target`, `wire_choose`, `add_incoming`, `finalize_summary`.
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- Provide a checker that validates coverage and invariants (e.g., each dst has at least one add_incoming; chosen preds ⊆ CFG preds).
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Code References
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- Trace writer: `src/llvm_py/llvm_builder.py`, `src/llvm_py/phi_wiring/wiring.py`
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- Checker: `tools/phi_trace_check.py`
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2025-09-24 23:27:59 +09:00
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Usage (v2)
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- `NYASH_LLVM_TRACE_PHI=1 NYASH_LLVM_TRACE_OUT=tmp/phi_trace.jsonl bash tools/smokes/phi_trace_local.sh`
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- `python3 tools/phi_trace_check.py --summary tmp/phi_trace.jsonl`
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2025-09-19 02:07:38 +09:00
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Next
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- Expand checks (dominance, grouping at head), integrate into CI as optional gate.
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