Enabling the epoch serving-mode JIT globally regressed continuation-based guest
interpreters (the epoch mode is the shared command channel every loop's
conformance runner uses). Two-part fix:
1. SAFE DEFAULT GATE. register_jit_hook in the persistent server branch is now
opt-in via SX_SERVING_JIT=1 (default OFF). Default behaviour is unchanged
(no JIT in epoch serving) → zero regression for sibling loops. The
content/Smalltalk page server opts in.
2. GENERAL FIXES + per-guest interpret-only declarations:
- callable? (sx_server/run_tests/integration_tests/mcp_tree) now accepts
VmClosure. A JIT-compiled higher-order function returns its inner closure
as a VmClosure; callable? previously rejected it, so scheme-apply's
(callable? proc) guard failed with "not a procedure: <vm:anon>".
- jit-exclude! gains a trailing-"*" namespace-prefix form
(Sx_types.jit_excluded_prefixes), the robust way to mark a whole guest
interpreter interpret-only (a name-list misses functions in extra files —
it left erlang's vm/dispatcher JIT'd and 13 tests short).
- Per-guest exclusions in each guest's runtime.sx:
scheme "scheme-*" "scm-*" erlang "er-*" "erlang-*"
prolog "pl-*" common-lisp "cl-*" "clos-*"
js "js-*" haskell "hk-*"
Verified under opt-in JIT (== CEK, no hang): smalltalk 847/847, scheme/flow
166/166, erlang 530/530, prolog 590/590, apl 152/152, js 147/148. Residual
(documented, protected by the default gate): common-lisp 6 fails in advanced
suites (parser-recovery/debugger/CLOS/MOP). lua (0/16) and tcl (3/4) fail
identically on CEK — pre-existing, not JIT. run_tests --jit/no-jit unchanged.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
register_jit_hook is now installed in the persistent (epoch) serving-mode
branch of sx_server.ml, not just --http/cli/site. Smalltalk-on-SX conformance
under JIT is 847/847 — identical to the no-JIT baseline; Datalog 356/356.
run_tests --jit/no-jit are byte-identical before/after (no regression).
Five distinct root causes fixed (not one "miscompile"):
1. Serving mode never loaded lib/compiler.sx, so JIT used the native
Sx_compiler.compile stub (arity-0 bytecode, params as GLOBAL_GET →
"VM undefined: <param>"). Server-mode branch now loads compiler.sx
before registering the hook, matching http/cli/site.
2. compile-cond / compile-case-clauses / compile-guard-clauses only treated
keyword :else and true as the catch-all, not the bare symbol `else` that
the CEK's is-else-clause? accepts → GLOBAL_GET "else". (lib/compiler.sx)
3. OP_DIV produced a float for non-divisible Integer/Integer (1/2 → 0.5)
instead of the exact Rational the "/" primitive returns. Now delegates to
the primitive, matching CEK. (sx_vm.ml)
4. OP_EQ / _fast_eq lacked Rational/ListRef cases that the "=" primitive's
safe_eq has → (= 1/2 1/2) false under JIT. OP_EQ now delegates non-scalars
to the "=" primitive; _fast_eq gained rational + ListRef. (sx_vm.ml,
sx_runtime.ml)
5. Continuation-based control flow (Smalltalk ^expr non-local return, block
escape, exceptions via call/cc) can't run in the stack VM. New data-driven
exclusion set Sx_types.jit_excluded + `jit-exclude!` primitive, consulted in
jit_compile_lambda (covers both the CEK hook and vm_call's tiered path).
lib/smalltalk/eval.sx self-declares its continuation dispatch core
interpret-only; pure helpers still JIT. The SUnit suite-runner test helper
pharo-test-class miscompiles mid-loop and is excluded in tests/tokenize.sx.
Also adds SX_JIT_DENY / SX_JIT_ONLY env-var bisection filters to the serving
hook. Known residual documented in plans/jit-bytecode-correctness.md: the hook
re-runs a failed VM execution via CEK (correct result, possible duplicate side
effects); adopting run_tests' propagate-don't-rerun semantics is deferred to
avoid changing shared VM/CEK behavior under this loop.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
