Phase 1.final of the flat-memory comptime VM — wire the host through it,
reach corpus parity, and gate it behind a build flag — plus the first
Phase 3 (compiler-API) step. Default OFF; legacy interpreter unchanged.
Host wiring + hardening:
- Machine accessors return error.OutOfBounds (no debug panic) on bad
addresses; Frame.get/set bounds-check and bail (no panic) on a malformed
operand ref (e.g. a ret Ref.none from an unresolved name).
- tryEval routed at both comptime call sites in emit_llvm — the const-init
fold and the #run side-effect path — with per-eval legacy fallback;
yields .void_val for void/noreturn entries. Both sites sx_trace_clear()
before the legacy fallback so a partial VM run that pushed trace frames
doesn't double-push on re-run.
VM coverage (all corpus const-inits except the inline-asm global):
- Implicit context materialized from the __sx_default_context global; the
full allocator protocol runs on the VM (context.allocator.alloc ->
call_indirect -> CAllocator thunk -> libc_malloc -> native flat malloc).
- Native libc memory builtins (malloc/calloc/free/memcpy/memmove/memset)
on flat memory; f32 stored/loaded as the 4-byte single; signed sub-64-bit
loads sign-extended; global_get (lazy + memoized); func_ref/call_indirect
(func-ref encoded fid+1, 0 reserved for null); string/slice fat-pointer
field access; is_comptime; the failable/error cluster (error_set tuples,
trace_frame + native sx_trace_push/clear -> raise/catch/or + return traces).
Build flag + Phase 3 seed:
- -Dcomptime-flat (build_opts module) OR SX_COMPTIME_FLAT env enables the VM;
zig build test -Dcomptime-flat runs the full corpus on the VM (688/0).
- intern/text_of serviced natively on flat memory via Vm.callCompilerFn
(compiler_welded boundary) — the seed the rest of the compiler-API grows on.
Parity 688/688 gate ON and OFF. Unit tests added throughout. The
lowering-time #insert wiring was explored and reverted (lowering-time IR can
be malformed; full malformed-IR hardening is a prerequisite, deferred).
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