Deferred Interning (CGO'27) · E6: make verify-arch independently toggleable

Paper: Deferred Interning: Deterministic, Lock-Free Parallel Compilation — CGO 2027 R2, deadline 2026-09-10 AoE.
Measurement plan: vx-review/parallel-frontend-paper/MEASUREMENT_PLAN.md · Vx tracking: hiraditya/Vx.1#300 · cross-repo index: hiraditya/vx-review#5

E6 of the CGO 2027 R2 measurement plan — and a gap in it.

The problem

E6 asks for "verify-arch on vs. off, same corpus: overhead %", to support the claim that executable invariants are affordable in debug and free in release.

As gated today that measurement cannot be produced. src/parallel_architecture_verifier.rs is #[cfg(debug_assertions)] (line 15) and there is no runtime flag — verified: nothing matching verify.arch in src/driver.rs or src/main.rs. So "on vs. off" is really "debug build vs. release build," which conflates the verifier's cost with every other debug assertion, bounds check, and optimisation-level difference in the binary. The resulting number would not be the verifier's overhead, and a reviewer will say so.

Scope

• make the verifier independently toggleable within a single build — runtime flag or cargo feature, either is fine, so long as one binary can run both arms
• confirm the release claim separately: verifier compiled out entirely, not merely skipped
• then measure overhead % on the E2 corpus

Doing this first is what makes E6's number mean what the paper says it means.

Read src/parallel_architecture_verifier.rs and inspect the related paths in src/driver.rs and src/main.rs, then review MEASUREMENT_PLAN.md for E6 and the E2 corpus. Choose a supported independent toggle that permits both arms in one build, verify the release build compiles the verifier out, and record the resulting overhead measurement.