Adds Sx_vm.bytecode_uses_extension_opcodes — an operand-aware
bytecode scanner that walks past CONST u16, CALL_PRIM u16+u8, and
CLOSURE u16+dynamic upvalue descriptors so operand bytes that happen
to be ≥200 don't false-positive as extension opcodes.
jit_compile_lambda calls the scanner on the inner closure's bytecode.
On hit it returns None — the lambda then runs through CEK
interpretation. The VM's dispatch fallthrough still routes the
extension opcodes themselves through the registry; this change just
prevents the JIT from claiming code it has no plan for.
Tests: 7 new foundation cases — pure core eligible, head/middle/
post-CLOSURE detection, CONST + CALL_PRIM + CLOSURE-descriptor false-
positive avoidance. +7 pass vs Phase D baseline, no regressions
across 11 conformance suites.
Loop complete: acceptance criteria 1-4 met. Hand-off to the Erlang
loop — lib/erlang/vm/dispatcher.sx's Phase 9b stub can now be
replaced with a real hosts/ocaml/lib/extensions/erlang.ml consumer.
lib/extensions/ becomes the new home for VM extensions, wired in via
(include_subdirs unqualified). README documents the registration
pattern, opcode-ID range conventions (200-209 guest_vm, 210-219
inline test, 220-229 test_ext, 230-247 ports), and naming rules.
extensions/test_ext.ml is the canonical worked example — two
operand-less opcodes (220 push 42, 221 double TOS) carrying a per-
extension state slot (TestExtState invocation counter). Test_ext.register
called from run_tests.ml at the start of the Phase D suite, on top of
the inline test_reg from earlier suites (disjoint opcode IDs).
Sx_vm.opcode_name now consults extension_opcode_name_ref (forward ref
in the same style as extension_dispatch_ref), so disassemble shows
extension opcodes by name instead of UNKNOWN_n. Registry maintains
name_of_id_table and installs the lookup at module init.
Tests: 5 new foundation cases — primitive resolves test_ext name,
end-to-end bytecode (push + double + return → 84), disassemble shows
"test_ext.OP_TEST_PUSH_42" / "test_ext.OP_TEST_DOUBLE_TOS",
unregistered ext opcodes still fall back to UNKNOWN_n, invocation
counter records the two dispatches. +5 pass vs Phase C baseline, no
regressions across 11 conformance suites.
Registers extension-opcode-id from sx_vm_extensions.ml module init.
Lives downstream of both sx_primitives and sx_vm to avoid a build
cycle. Accepts a string or symbol; returns Integer id when the opcode
is registered, Nil otherwise.
Compilers (lib/compiler.sx) call this to emit extension opcodes by
name. Returning Nil rather than failing on unknown names lets a port's
optimization opt in per-build — missing extensions degrade to slower
correct execution.
Tests: 5 new foundation cases — registered lookup, unknown → nil,
symbol arg, zero-arg + integer-arg rejection. +5 pass vs Phase B
baseline, no regressions across 11 conformance suites.
sx_vm_extension.ml: handler type, extensible extension_state variant,
EXTENSION first-class module signature.
sx_vm_extensions.ml: register / dispatch / id_of_name /
state_of_extension. install_dispatch () runs at module init,
swapping Phase A's stub for the real registry. Rejects out-of-range
opcode IDs (must be 200-247), duplicate IDs, duplicate names, and
duplicate extension names.
Tests: 9 new foundation cases — lookup hits/misses, end-to-end VM
dispatch including opcode composition, all four rejection paths.
+9 pass vs Phase A baseline, no regressions across 11 conformance
suites.
Adds Invalid_opcode of int exception and extension_dispatch_ref forward
ref (default raises Invalid_opcode op), plus the |op when op >= 200 arm
before the catch-all in the bytecode dispatch loop. Partition comment
documents 1-199 core / 200-247 extensions / 248-255 reserved.
Phase B will install the real registry's dispatch into the ref at module
init, replacing this stub.
Tests: 4 new foundation cases (Invalid_opcode for 200/224/247, Eval_error
for 199 to pin the threshold). +4 pass vs baseline, no regressions.
plans/sx-vm-opcode-extension.md ports over from loops/erlang (f6a68656)
with the opcode partition adjusted to match real VM usage: 1-199 core
(current ceiling 175 = OP_DEC), 200-247 extensions, 248-255 reserved.
plans/agent-briefings/sx-vm-extensions-loop.md captures the per-fire
workflow and ground rules.
