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sx: step 14 — inline JIT primitives (-69% fib, -62% loop, -50% sum on bench_vm)

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The bytecode compiler emitted OP_CALL_PRIM (52) for every primitive call, even
for arithmetic and comparison hot-paths. The VM had specialized opcodes
(OP_ADD, OP_SUB, OP_EQ, etc.) defined but unused.

- lib/compiler.sx (compile-call): emit specialized 1-byte opcode when the
  primitive name + arity matches one of {+, -, *, /, =, <, >, cons, not, len,
  first, rest}. Falls back to CALL_PRIM otherwise. fib bytecode: 50 → 38 bytes.
- hosts/ocaml/lib/sx_compiler.ml: mirror change in the auto-generated OCaml
  compiler so SXBC export from mcp_tree uses the same emission.
- hosts/ocaml/lib/sx_vm.ml: extend OP_ADD/SUB/MUL/DIV to handle Integer+Integer
  (not just Number+Number). Inline OP_EQ via Sx_runtime._fast_eq. Inline
  OP_LT/GT mixed-numeric comparisons. Avoids Hashtbl lookup on the fallback
  path for the common integer cases that dominate tight loops.
- hosts/ocaml/bin/bench_vm.ml: VM-only benchmark — loads compiler.sx via CEK,
  JIT-compiles each fn, measures Sx_vm.call_closure throughput.

Median improvements (best of 3 runs of 9-min, bench_vm.exe):
  fib(22)         107.87ms →  33.13ms   -69%
  loop(200000)    429.64ms → 161.16ms   -62%
  sum-to(50000)    72.85ms →  36.74ms   -50%
  count-lt(20000)  28.44ms →  17.58ms   -38%
  count-eq(20000)  37.23ms →  15.46ms   -58%

Tests: 4550/4550 OCaml passing (unchanged). Zero regressions.

Last step in the sx-improvements roadmap — all 14 steps complete.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
This commit is contained in:
giles
2026-05-07 02:38:47 +00:00
parent 4cb5302232
commit 6c171d4906
6 changed files with 262 additions and 10 deletions
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25
hosts/ocaml/lib/sx_compiler.ml
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@@ -200,7 +200,30 @@ and compile_qq_list em items scope =
(* compile-call *)
and compile_call em head args scope tail_p =
(let is_prim = (let _and = (prim_call "=" [(type_of (head)); (String "symbol")]) in if not (sx_truthy _and) then _and else (let name = (symbol_name (head)) in (let _and = (Bool (not (sx_truthy ((prim_call "=" [(get ((scope_resolve (scope) (name))) ((String "type"))); (String "local")]))))) in if not (sx_truthy _and) then _and else (let _and = (Bool (not (sx_truthy ((prim_call "=" [(get ((scope_resolve (scope) (name))) ((String "type"))); (String "upvalue")]))))) in if not (sx_truthy _and) then _and else (is_primitive (name)))))) in (if sx_truthy (is_prim) then (let name = (symbol_name (head)) in let argc = (len (args)) in let name_idx = (pool_add ((get (em) ((String "pool")))) (name)) in (let () = ignore ((List.iter (fun a -> ignore ((compile_expr (em) (a) (scope) ((Bool false))))) (sx_to_list args); Nil)) in (let () = ignore ((emit_op (em) ((Number 52.0)))) in (let () = ignore ((emit_u16 (em) (name_idx))) in (emit_byte (em) (argc)))))) else (let () = ignore ((compile_expr (em) (head) (scope) ((Bool false)))) in (let () = ignore ((List.iter (fun a -> ignore ((compile_expr (em) (a) (scope) ((Bool false))))) (sx_to_list args); Nil)) in (if sx_truthy (tail_p) then (let () = ignore ((emit_op (em) ((Number 49.0)))) in (emit_byte (em) ((len (args))))) else (let () = ignore ((emit_op (em) ((Number 48.0)))) in (emit_byte (em) ((len (args))))))))))
(let is_prim = (let _and = (prim_call "=" [(type_of (head)); (String "symbol")]) in if not (sx_truthy _and) then _and else (let name = (symbol_name (head)) in (let _and = (Bool (not (sx_truthy ((prim_call "=" [(get ((scope_resolve (scope) (name))) ((String "type"))); (String "local")]))))) in if not (sx_truthy _and) then _and else (let _and = (Bool (not (sx_truthy ((prim_call "=" [(get ((scope_resolve (scope) (name))) ((String "type"))); (String "upvalue")]))))) in if not (sx_truthy _and) then _and else (is_primitive (name)))))) in (if sx_truthy (is_prim) then (let name = (symbol_name (head)) in let argc = (len (args)) in
(* Specialized opcode for hot 2-arg / 1-arg primitives. *)
let specialized_op = (match name, argc with
| String "+", Number 2.0 -> Some 160
| String "-", Number 2.0 -> Some 161
| String "*", Number 2.0 -> Some 162
| String "/", Number 2.0 -> Some 163
| String "=", Number 2.0 -> Some 164
| String "<", Number 2.0 -> Some 165
| String ">", Number 2.0 -> Some 166
| String "cons", Number 2.0 -> Some 172
| String "not", Number 1.0 -> Some 167
| String "len", Number 1.0 -> Some 168
| String "first", Number 1.0 -> Some 169
| String "rest", Number 1.0 -> Some 170
| _ -> None) in
(let () = ignore ((List.iter (fun a -> ignore ((compile_expr (em) (a) (scope) ((Bool false))))) (sx_to_list args); Nil)) in
(match specialized_op with
| Some op -> emit_op em (Number (float_of_int op))
| None ->
let name_idx = (pool_add ((get (em) ((String "pool")))) (name)) in
let () = ignore ((emit_op (em) ((Number 52.0)))) in
let () = ignore ((emit_u16 (em) (name_idx))) in
emit_byte (em) (argc)))) else (let () = ignore ((compile_expr (em) (head) (scope) ((Bool false)))) in (let () = ignore ((List.iter (fun a -> ignore ((compile_expr (em) (a) (scope) ((Bool false))))) (sx_to_list args); Nil)) in (if sx_truthy (tail_p) then (let () = ignore ((emit_op (em) ((Number 49.0)))) in (emit_byte (em) ((len (args))))) else (let () = ignore ((emit_op (em) ((Number 48.0)))) in (emit_byte (em) ((len (args))))))))))
(* compile *)
and compile expr =