restore(lang): full lang tree from ff3ef452 (306 files) — compiler, vm, shared, runner, c-abi, etc.\n\n- Restores lang/ directory (files≈306, dirs≈64) as per historical branch with selfhost sources\n- Keeps our recent parser index changes in compiler/* (merged clean by checkout)\n- Unblocks selfhost development and documentation references

lang/src/llvm_ir/boxes/aot_prep.hako

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+// aot_prep.hako — AotPrepBox (pre-MIR normalizer/optimizer; skeleton)
+// 入出力（最小仕様）
+// - AotPrepBox.prep/1(json_in_path: String) -> String (json_out_path)
+// 責務
+// - JSON(MIR v0) の軽量正規化（キー順/冗長キー削除）と安全な const/binop(+,-,*)/ret の単一ブロック畳み込み
+// - 既定ではパススルー（Rust 側 maybe_prepare_mir_json が実体）。段階的にこちらへ移管する
+
+using "lang/src/shared/mir/mir_io_box.hako" as MirIoBox
+using "lang/src/shared/common/string_helpers.hako" as StringHelpers
+
+static box AotPrepBox {
+  // AotPrepBox.prep
+  // 入力: JSONファイルパス（MIR v0）
+  // 出力: 正規化後のJSONを書き出したパス（<in>.prep.json）。失敗時は入力パスを返す（Fail‑FastはRust側が継続）。
+  prep(json_in_path) {
+    if !json_in_path { return json_in_path }
+    // Read input
+    local fb = new FileBox()
+    fb.open(json_in_path, "r")
+    local src = fb.read()
+    fb.close()
+    if !src { return json_in_path }
+
+    // Phase‑1: 文字列正規化（安定化）
+    // いまは canonicalize は恒等（将来はHostBridgeでキー順安定化）
+    local canon = MirIoBox.normalize(src)
+
+    // Phase‑2: 安全な単一ブロック const/binop(+,-,*)/ret の畳み込み（最小実装）
+    // 備考: まずは main 関数を優先対象とし、成立時のみ最小 JSON に置換（今後は in‑place 置換へ段階移行）。
+    local out = AotPrepBox._try_fold_const_binop_ret(canon)
+    if !out { out = canon }
+
+    // Decide output path
+    local out_path = json_in_path + ".prep.json"
+    fb.open(out_path, "w")
+    fb.write(out)
+    fb.close()
+    return out_path
+  }
+
+  // 内部: 最小の安全畳み込み（JSON文字列ベース）
+  _try_fold_const_binop_ret(json) {
+    if !json { return null }
+    // Helper: find the [ ... ] span of the first block's instructions for the function near `start_from`.
+    local find_instr_span_from = fun(s, start_from) {
+      local key = "\"instructions\":["
+      local pos = s.indexOf(key, start_from)
+      if pos < 0 { return [-1, -1] }
+      local ls = s.indexOf("[", pos)
+      if ls < 0 { return [-1, -1] }
+      local depth = 0
+      local i = ls
+      local L = s.size()
+      local rs = -1
+      loop(i < L) {
+        local ch = s.substring(i, i+1)
+        if ch == "[" { depth = depth + 1 }
+        if ch == "]" { depth = depth - 1; if depth == 0 { rs = i; break } }
+        i = i + 1
+      }
+      return [ls, rs]
+    }
+    // Helper: attempt to fold within a given [arr_start, arr_end] span; return replaced JSON on success
+    local try_fold_in_span = fun(s, arr_start, arr_end) {
+      if arr_start < 0 || arr_end < 0 { return null }
+      local body = s.substring(arr_start, arr_end+1)
+      // Need two const, a binop, and a ret in this span
+      local p1 = body.indexOf("\"op\":\"const\"")
+      local p2 = body.indexOf("\"op\":\"const\"", (p1>=0 ? (p1+1) : 0))
+      local pb = body.indexOf("\"op\":\"binop\"", (p2>=0 ? (p2+1) : 0))
+      local pr = body.indexOf("\"op\":\"ret\"", (pb>=0 ? (pb+1) : 0))
+      if p1 < 0 || p2 < 0 || pb < 0 || pr < 0 { return null }
+      // parse helpers within body
+      local parse_dst = fun(ss, pos) {
+        local k = "\"dst\":"
+        local i = ss.indexOf(k, pos)
+        if i < 0 { return -1 }
+        i = i + k.size()
+        local digs = StringHelpers.read_digits(ss, i)
+        if digs == "" { return -1 }
+        return StringHelpers.to_i64(digs)
+      }
+      local parse_val = fun(ss, pos) {
+        local k = "\"value\":{\"type\":\"i64\",\"value\":"
+        local i = ss.indexOf(k, pos)
+        if i < 0 { return null }
+        i = i + k.size()
+        local digs = StringHelpers.read_digits(ss, i)
+        if digs == "" { return null }
+        return StringHelpers.to_i64(digs)
+      }
+      local d1 = parse_dst(body, p1)
+      local a  = parse_val(body, p1)
+      local d2 = parse_dst(body, p2)
+      local b  = parse_val(body, p2)
+      if d1 < 0 || d2 < 0 || a == null || b == null { return null }
+      local find_num = fun(ss, key, pos) {
+        local k = key
+        local i = ss.indexOf(k, pos)
+        if i < 0 { return -1 }
+        i = i + k.size()
+        local digs = StringHelpers.read_digits(ss, i)
+        if digs == "" { return -1 }
+        return StringHelpers.to_i64(digs)
+      }
+      local find_op = fun(ss, pos) {
+        local k = "\"operation\":\""
+        local i = ss.indexOf(k, pos)
+        if i < 0 { return "" }
+        i = i + k.size()
+        local j = ss.indexOf("\"", i)
+        if j < 0 { return "" }
+        return ss.substring(i, j)
+      }
+      local lhs = find_num(body, "\"lhs\":", pb)
+      local rhs = find_num(body, "\"rhs\":", pb)
+      local bop = find_op(body, pb)
+      local d3  = find_num(body, "\"dst\":", pb)
+      if lhs != d1 || rhs != d2 || d3 < 0 { return null }
+      local rv = find_num(body, "\"value\":", pr)
+      if rv != d3 { return null }
+      // binop allowed: +,-,* only
+      local res = 0
+      if bop == "+" { res = a + b } else { if bop == "-" { res = a - b } else { if bop == "*" { res = a * b } else { return null } } }
+      // build new array and replace in-place
+      local new_insts = "[" +
+        "{\\\"op\\\":\\\"const\\\",\\\"dst\\\":" + StringHelpers.int_to_str(d1) + ",\\\"value\\\":{\\\"type\\\":\\\"i64\\\",\\\"value\\\":" + StringHelpers.int_to_str(res) + "}}," +
+        "{\\\"op\\\":\\\"ret\\\",\\\"value\\\":" + StringHelpers.int_to_str(d1) + "}]"
+      local head = s.substring(0, arr_start)
+      local tail = s.substring(arr_end + 1, s.size())
+      return head + new_insts + tail
+    }
+    // Pass 1: prefer name:"main"
+    local fn_pos = json.indexOf("\"name\":\"main\"")
+    if fn_pos >= 0 {
+      local span = find_instr_span_from(json, fn_pos)
+      local ls = span[0]; local rs = span[1]
+      local repl = try_fold_in_span(json, ls, rs)
+      if repl { return repl }
+    }
+    // Pass 2: scan functions sequentially and attempt per function
+    local froot = json.indexOf("\"functions\":[")
+    if froot < 0 { return null }
+    local scan = froot
+    local tries = 0
+    loop(tries < 16) {
+      local np = json.indexOf("\"name\":\"", scan+1)
+      if np < 0 { break }
+      local span2 = find_instr_span_from(json, np)
+      local ls2 = span2[0]; local rs2 = span2[1]
+      if ls2 >= 0 && rs2 >= 0 {
+        local repl2 = try_fold_in_span(json, ls2, rs2)
+        if repl2 { return repl2 }
+        scan = rs2 + 1
+      } else {
+        scan = np + 8
+      }
+      tries = tries + 1
+    }
+    return null
+  }
+}