ludic/selfhost/backend/game/emit_save.ludic

# emit_save.ludic — save() / load() snapshot of the whole ECS world. The
# compiler writes the entity/component half itself (it knows the shape) and
# hands the open file to rt_save_state/rt_load_state for the runtime's own
# state. Mirrors compiler/back/ir_save.c. save()->@L_save, load()->@L_load.

var g_iok: int = 0

# The snapshot is a fixed sequence of (region, byte-length) blocks; the same list
# feeds two targets — a file (save/load via fwrite/fread) and a memory buffer
# (world_save/world_load via memcpy, NETWORKING-DESIGN §5 N1). g_snap_mode picks
# which; buffer modes thread a running i64 offset (@g_off) so world_save returns
# the total byte count and world_load reads the identical layout back.
# NOTE: a string initializer on a module `ptr` var lowers to null (global_init),
# so these are seeded at runtime in emit_snapshot before first use — never read
# them uninitialized (a null string `==` would deref and crash the compiler).
var g_snap_mode: pointer = null      # "file" | "save" | "load" | "size"
var g_off: pointer = null            # current byte-offset register, buffer modes

function emit_io(fn2: pointer, p: pointer, bytes: pointer) -> void {
  if (g_snap_mode == "file") {
    let r = `%io{itoa(g_iok)}`;  g_iok += 1
    emit("  ");  emit(r);  emit(" = call i64 @");  emit(fn2);  emit("(ptr ");  emit(p);  emit(", i64 1, i64 ");  emit(bytes);  emit(", ptr %f)\n")
    return
  }
  if (g_snap_mode == "size") {                    # accumulate the offset only, no copy
    let noff = `%ioff{itoa(g_iok)}`
    emit("  ");  emit(noff);  emit(" = add i64 ");  emit(g_off);  emit(", ");  emit(bytes);  emit("\n")
    g_off = noff
    g_iok += 1
    return
  }
  # buffer mode: dst/src is %buf + g_off, copy `bytes`, then advance the cursor
  let addr = `%ioa{itoa(g_iok)}`
  emit("  ");  emit(addr);  emit(" = getelementptr inbounds i8, ptr %buf, i64 ");  emit(g_off);  emit("\n")
  if (g_snap_mode == "save") {
    emit("  call ptr @memcpy(ptr ");  emit(addr);  emit(", ptr ");  emit(p);  emit(", i64 ");  emit(bytes);  emit(")\n")
  } else {
    emit("  call ptr @memcpy(ptr ");  emit(p);  emit(", ptr ");  emit(addr);  emit(", i64 ");  emit(bytes);  emit(")\n")
  }
  let noff = `%ioff{itoa(g_iok)}`
  emit("  ");  emit(noff);  emit(" = add i64 ");  emit(g_off);  emit(", ");  emit(bytes);  emit("\n")
  g_off = noff
  g_iok += 1
}

function emit_snapshot_blocks(fn2: pointer) -> void {
  g_iok = 0
  g_off = "0"
  let me = itoa(MAX_ENT)
  emit_io(fn2, "@L_entc", "4")
  emit_io(fn2, "@L_freen", "4")
  emit("  %nalive = mul i64 ");  emit(me);  emit(", 4\n")
  emit_io(fn2, "@L_alive", "%nalive")
  emit_io(fn2, "@L_freelist", "%nalive")
  emit_io(fn2, "@L_kind", "%nalive")
  # N3: an @Owned world snapshots its per-entity owners too, so rollback/replication
  # round-trips ownership (like @L_kind). Gated, so non-@Owned snapshots are unchanged.
  if net_has_owned() { emit_io(fn2, "@L_owner_arr", "%nalive") }
  var i = 0
  while i < len(prog) { if prog[i].kind == N_VAR { emit_io(fn2, `@g_{prog[i].s}`, "4") };  i += 1 }
  var ci = 0
  i = 0
  while i < len(prog) {
    if prog[i].kind == N_COMP {
      let c = prog[i].s
      let csz = `%csz{itoa(ci)}`
      emit("  ");  emit(csz);  emit(" = ptrtoint ptr getelementptr (%Cmp_");  emit(c);  emit(", ptr null, i32 ");  emit(me);  emit(") to i64\n")
      emit_io(fn2, `@S_{c}`, csz)
      emit_io(fn2, `@H_{c}`, me)
      ci += 1
    }
    i += 1
  }
}

function emit_snapshot() -> void {
  g_snap_mode = "file"                            # seed (module ptr inits are null)
  emith("@.sav_path = private unnamed_addr constant [10 x i8] c\"ludic.sav\\00\"\n")
  emith("@.sav_wb = private unnamed_addr constant [3 x i8] c\"wb\\00\"\n")
  emith("@.sav_rb = private unnamed_addr constant [3 x i8] c\"rb\\00\"\n")
  let has_save = (find_fn("rt_save_state") != null)
  let has_load = (find_fn("rt_load_state") != null)

  emit("define void @L_save() {\nentry:\n")
  emit("  %f = call ptr @fopen(ptr @.sav_path, ptr @.sav_wb)\n")
  emit("  %bad = icmp eq ptr %f, null\n")
  emit("  br i1 %bad, label %out, label %go\ngo:\n")
  emit_snapshot_blocks("fwrite")
  if has_save { emit("  call void @fn_rt_save_state(ptr %f)\n") }
  emit("  %c = call i32 @fclose(ptr %f)\n  br label %out\nout:\n  ret void\n}\n\n")

  emit("define i32 @L_load() {\nentry:\n")
  emit("  %f = call ptr @fopen(ptr @.sav_path, ptr @.sav_rb)\n")
  emit("  %bad = icmp eq ptr %f, null\n")
  emit("  br i1 %bad, label %miss, label %go\nmiss:\n  ret i32 0\ngo:\n")
  emit_snapshot_blocks("fread")
  if has_load { emit("  call void @fn_rt_load_state(ptr %f)\n") }
  emit("  %c = call i32 @fclose(ptr %f)\n  ret i32 1\n}\n\n")

  # world_save(buf) -> int / world_load(buf, len): the same whole-world snapshot,
  # to a caller-owned memory buffer instead of a file (NETWORKING-DESIGN §5 N1) —
  # the rollback/replication substrate. No rt_ hook: this is the ECS world only
  # (entities, components, vars), which is what a peer replicates or a rollback
  # restores; the runtime's windowing state stays local. world_save returns the
  # byte count written; the caller sizes the buffer with world_size().
  emit("define i32 @L_world_save(ptr %buf) {\nentry:\n")
  g_snap_mode = "save"
  emit_snapshot_blocks("")
  let sret = `%wsn{itoa(g_iok)}`
  emit("  ");  emit(sret);  emit(" = trunc i64 ");  emit(g_off);  emit(" to i32\n")
  emit("  ret i32 ");  emit(sret);  emit("\n}\n\n")

  emit("define void @L_world_load(ptr %buf, i32 %len) {\nentry:\n")
  g_snap_mode = "load"
  emit_snapshot_blocks("")
  emit("  ret void\n}\n\n")

  # world_size() -> int: the exact byte count a full snapshot needs, so a caller
  # can size the buffer before world_save. Same block walk, offset-only.
  emit("define i32 @L_world_size() {\nentry:\n")
  g_snap_mode = "size"
  emit_snapshot_blocks("")
  let zret = `%wzn{itoa(g_iok)}`
  emit("  ");  emit(zret);  emit(" = trunc i64 ");  emit(g_off);  emit(" to i32\n")
  emit("  ret i32 ");  emit(zret);  emit("\n}\n\n")
  g_snap_mode = "file"
}