新增 rtl-signal-mcp: RTL 信号追踪 MCP server（索引引擎+8工具+验收脚本）

rtl-mcp/README.md

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+# rtl-signal-mcp
+
+给 AI agent 用的 RTL 信号追踪 MCP Server。解决一个具体问题：**RTL 信号的联系跨模块分布在端口连接上，读单个文件看不出来**。本工具把整个代码库索引成"模块事实库 + 跨边界信号边"，agent 查一次得一条紧凑驱动链，不用通读源码、不烧 token。
+
+实测性能：OpenTitan 全 hw 树（31 万行 RTL）→ **971 模块 / 94,891 条跨模块边 / 10.6 秒建索引 / 310MB 内存**；单次追踪查询毫秒级、返回几百字节文本。
+
+## 包含文件
+
+| 文件 | 说明 |
+|---|---|
+| `rtl_index.py` | 核心引擎：pyslang 解析 → 模块事实库（端口/网络/assign/always/实例化）→ 跨模块边 → 驱动/负载递归查询 |
+| `mcp_server.py` | MCP stdio server（纯标准库实现 JSON-RPC 2.0，无 SDK 依赖） |
+| `mcp_client_demo.py` | 测试客户端（模拟 agent 完整调用序列，可当验收脚本） |
+| `README.md` | 本文件 |
+
+## 8 个工具
+
+| 工具 | 作用 | token 成本 |
+|---|---|---|
+| `build_index` | 建索引（roots: 文件/目录列表） | 一次性 |
+| `list_modules` | 列模块及事实计数 | 极小 |
+| `module_summary` | 单模块端口/实例/连接摘要 | 小 |
+| `find_signal` | 正则搜信号 → 模块 + file:line | 极小 |
+| **`trace_drivers`** | **谁驱动这个信号**（跨模块递归） | **每次几百字节** |
+| **`trace_loads`** | **这个信号驱动谁**（上抛+下钻） | 小 |
+| `get_source` | 按行取小段源码（≤200 行） | 按需 |
+| `hierarchy` | 实例化树 | 小 |
+
+## 接入 Claude / 其他 MCP 客户端
+
+```json
+{
+  "mcpServers": {
+    "rtl-signal": {
+      "command": "python3",
+      "args": ["/path/to/rtl-mcp/mcp_server.py"],
+      "env": { "RTL_MCP_ROOTS": "/data/repos/e203_hbirdv2/rtl/e203:/data/repos/opentitan/hw/ip" }
+    }
+  }
+}
+```
+
+`RTL_MCP_ROOTS` 冒号分隔多个目录，启动时自动预建索引；不设则由 agent 首次调用 `build_index`。
+
+依赖：`pip install pyslang`（仅此一个）。Python ≥ 3.10。
+
+## Agent 使用模式（写进系统提示词即可）
+
+```
+调试 RTL 信号问题时按此流程：
+1. find_signal 找到信号的归属模块和位置
+2. trace_drivers 查驱动链（跨模块），trace_loads 查影响面
+3. 只对链上关键条目用 get_source 看 file:line 附近 ±20 行
+4. 绝不整文件读源码；结论引用 [kind] where :: sig <- rhs 条目
+```
+
+## 已验证范围
+
+- E203 蜂鸟 RISC-V 核（42 文件/39 模块/1789 边/0.2s）：`trace_drivers(e203_exu_alu.i_valid)` 正确给出 ALU←EXU 译码器三模块链（含 file:line）
+- OpenTitan `hw/ip/aes`（67 模块/1037 边）
+- OpenTitan `hw/ip + top_earlgrey`（841 模块/84,942 边/7s）
+- OpenTitan 全 hw 树（971 模块/94,891 边/10.6s/310MB）
+
+## 已知边界（诚实声明）
+
+- 语法级分析：不做参数展开/elaboration——generate for、parameter 化的端口名按字面处理；位宽/方向冲突不检测
+- always 块提取覆盖 always/always_ff/always_comb 内的阻塞与非阻塞赋值（含 if/case 嵌套与时序控制穿透），函数内赋值暂不提取
+- 跨模块追踪经实例端口边递归，Max depth 默认 4（可调）；未索引的第三方模块（如仅黑盒实例名）标为链尾
+- SystemVerilog interface/class/sequence 未索引（面向可综合 RTL 设计）
+- 同名信号在不同模块中是不同节点——查询需给 module + signal 两个参数（`find_signal` 可帮定位）
+
+## 路线图（人用的网页版后置）
+
+- v0.2: elaboration 级准确（走 pyslang AST 编译而不是纯语法树），generate/parameter 展开
+- v0.3: 波形接入（pylibfst 读 FST，值反标到驱动链 → X 态/根因追踪）；参考腾讯开源 wave-mcp
+- v0.4: 网页视图（驱动链图形化 + 波形联动），给人 review 用

rtl-mcp/mcp_client_demo.py

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+#!/usr/bin/env python3
+"""mcp_client_demo.py — rtl-signal-mcp 验收脚本。
+
+不做真 MCP 握手库，直接以子进程方式拉起 mcp_server.py，按行写 JSON-RPC、按行读响应，
+模拟一个 agent 的完整调用序列：
+
+  initialize -> notifications/initialized -> tools/list
+  -> build_index -> list_modules -> module_summary -> find_signal
+  -> trace_drivers -> trace_loads -> get_source -> hierarchy
+
+用法：
+  python3 mcp_client_demo.py /data/repos/e203_hbirdv2/rtl/e203
+  python3 mcp_client_demo.py            # 缺省用 E203 路径（不存在则报错提示）
+
+退出码 0 = 全部步骤通过；非 0 = 某步失败（打印到 stderr）。
+"""
+import json, os, subprocess, sys
+
+HERE = os.path.dirname(os.path.abspath(__file__))
+SERVER = os.path.join(HERE, "mcp_server.py")
+
+DEFAULT_ROOTS = [
+    "/data/repos/e203_hbirdv2/rtl/e203",      # 本地缺省
+]
+
+
+def start_server(roots):
+    env = dict(os.environ)
+    env["RTL_MCP_ROOTS"] = ":".join(roots)
+    return subprocess.Popen(
+        [sys.executable, SERVER],
+        stdin=subprocess.PIPE, stdout=subprocess.PIPE,
+        env=env, text=True, encoding="utf-8", bufsize=1)
+
+
+def call(proc, method, params=None, msg_id=[0]):
+    """写一条请求并读回响应（跳过通知）。返回 result 或抛 RuntimeError。"""
+    msg_id[0] += 1
+    req = dict(jsonrpc="2.0", id=msg_id[0], method=method, params=params or {})
+    proc.stdin.write(json.dumps(req) + "\n")
+    proc.stdin.flush()
+    while True:
+        line = proc.stdout.readline()
+        if not line:
+            raise RuntimeError(f"server closed during {method}")
+        resp = json.loads(line)
+        if resp.get("id") == msg_id[0]:
+            if "error" in resp:
+                raise RuntimeError(f"{method} error: {resp['error']}")
+            return resp["result"]
+
+
+def notify(proc, method, params=None):
+    req = dict(jsonrpc="2.0", method=method, params=params or {})
+    proc.stdin.write(json.dumps(req) + "\n")
+    proc.stdin.flush()
+
+
+def show(title, text, max_lines=12):
+    print(f"\n=== {title} ===")
+    lines = text.splitlines()
+    for ln in lines[:max_lines]:
+        print(" ", ln)
+    if len(lines) > max_lines:
+        print(f"  ... ({len(lines) - max_lines} more lines)")
+
+
+def fail(step, msg):
+    raise RuntimeError(f"step {step} failed: {msg}")
+
+
+def main():
+    roots = [a for a in sys.argv[1:] if not a.startswith("-")] or DEFAULT_ROOTS
+    missing = [r for r in roots if not os.path.exists(r)]
+    if missing:
+        print(f"roots not found: {missing}\n"
+              f"usage: python3 mcp_client_demo.py <rtl_dir> [...]", file=sys.stderr)
+        return 2
+
+    proc = start_server(roots)
+    try:
+        # 1. MCP 握手
+        r = call(proc, "initialize", dict(
+            protocolVersion="2024-11-05",
+            capabilities={},
+            clientInfo=dict(name="demo-client", version="0.1")))
+        ver = r["protocolVersion"]
+        print(f"[1] initialize OK  server={r['serverInfo']['name']} "
+              f"v{r['serverInfo']['version']}  protocol={ver}")
+        notify(proc, "notifications/initialized")
+
+        # 2. 工具清单
+        r = call(proc, "tools/list")
+        tools = [t["name"] for t in r["tools"]]
+        print(f"[2] tools/list OK  {len(tools)} tools: {', '.join(tools)}")
+
+        # 3. 建索引（启动时已用 RTL_MCP_ROOTS 预建过一次，这里验证重复调用幂等）
+        r = call(proc, "tools/call", dict(name="build_index",
+                                          arguments=dict(roots=roots)))
+        st = r["structuredContent"]
+        print(f"[3] build_index OK  modules={st['modules']} "
+              f"cross_edges={st['cross_edges']}")
+
+        # 4. 模块列表（取第一个模块做后续实验对象）
+        r = call(proc, "tools/call", dict(name="list_modules", arguments={}))
+        mods = r["structuredContent"]["modules"]
+        print(f"[4] list_modules OK  total={r['structuredContent']['total']} "
+              f"first={mods[0]['module']}")
+
+        # 5. 挑一个"实例数较多"的模块做摘要
+        target = max(mods, key=lambda m: m["insts"])["module"]
+        r = call(proc, "tools/call", dict(name="module_summary",
+                                          arguments=dict(module=target)))
+        show(f"module_summary {target}", r["content"][0]["text"], 8)
+
+        # 6. 找一个跨模块信号：用摘要里第一个输出端口
+        r2 = call(proc, "tools/call", dict(name="module_summary",
+                                           arguments=dict(module=target)))
+        sc = r2["structuredContent"]
+        port = None
+        for p in sc.get("ports", []):
+            # 端口格式是 "Output nice_xs_off" / "Input csr_ena" 这样的字符串
+            if str(p).startswith("Output"):
+                port = str(p).split(None, 1)[1]
+                break
+        if port is None:  # 摘要结构兜底：直接试常见信号
+            port = "clk"
+        r = call(proc, "tools/call", dict(name="find_signal",
+                                          arguments=dict(pattern=port, limit=5)))
+        hits = r["structuredContent"]["hits"]
+        print(f"[6] find_signal '{port}' OK  {len(hits)} hits")
+
+        # 7. 追驱动链（核心能力）
+        r = call(proc, "tools/call", dict(name="trace_drivers",
+                                          arguments=dict(module=target,
+                                                         signal=port, depth=4)))
+        sc = r["structuredContent"]
+        n = len(sc.get("result", []))
+        print(f"[7] trace_drivers {target}.{port} OK  {n} rows")
+        show("driver chain", r["content"][0]["text"], 12)
+        if n == 0 and port != "clk":
+            # 输出端口可能由子模块驱动也可能本就是顶层输入，空不算失败
+            print("    (empty chain — top-level input or tb-driven)")
+
+        # 8. 追负载
+        r = call(proc, "tools/call", dict(name="trace_loads",
+                                          arguments=dict(module=target,
+                                                         signal=port, depth=3)))
+        n = len(r["structuredContent"].get("result", []))
+        print(f"[8] trace_loads {target}.{port} OK  {n} rows")
+
+        # 9. 从驱动链里拿一个 file:line 看小段源码
+        r = call(proc, "tools/call", dict(name="trace_drivers",
+                                          arguments=dict(module=target,
+                                                         signal=port, depth=2)))
+        rows = r["structuredContent"].get("result", [])
+        loc = None
+        import re
+        for row in rows:
+            # where 形如 "e203_exu_csr  (e203_exu_csr.v:210)"
+            m = re.search(r"([\w./]+):(\d+)\)\s*$", row.get("where", ""))
+            if row.get("kind") == "assign" and m:
+                loc = (m.group(1), int(m.group(2)))
+                break
+        if loc:
+            fname, lineno = loc
+            r = call(proc, "tools/call", dict(
+                name="get_source",
+                arguments=dict(file=fname, start=max(1, lineno - 5),
+                               end=lineno + 5)))
+            show(f"get_source {fname}:{lineno - 5}-{lineno + 5}",
+                 r["content"][0]["text"], 12)
+            if "error" in r["structuredContent"]:
+                fail("get_source", r["structuredContent"]["error"])
+        else:
+            print("[9] get_source skipped (no assign location in chain)")
+
+        # 10. 层次树
+        r = call(proc, "tools/call", dict(name="hierarchy",
+                                          arguments=dict(module=target, depth=2)))
+        show("hierarchy", r["content"][0]["text"], 10)
+
+        print("\nALL CHECKS PASSED")
+        return 0
+    finally:
+        try:
+            proc.stdin.close()
+        except Exception:
+            pass
+        proc.terminate()
+
+
+if __name__ == "__main__":
+    sys.exit(main())

rtl-mcp/mcp_server.py

@@ -0,0 +1,253 @@
+#!/usr/bin/env python3
+"""rtl-signal-mcp — MCP server exposing RTL signal-flow tracing to AI agents.
+
+Protocol: MCP over stdio (JSON-RPC 2.0). No third-party MCP SDK required.
+
+Tools (token-efficient by design — every answer is a compact graph, not source):
+  build_index    build/replace the index from file/dir roots
+  list_modules   module names + instantiation counts
+  module_summary ports / instances / net count of one module
+  find_signal    regex search over all signals -> module + file:line
+  trace_drivers  who drives this signal (recursively, across module boundaries)
+  trace_loads    what does this signal drive (recursively, up and down)
+  get_source     small excerpt of a file by line range
+  hierarchy      instantiation tree under a module
+
+Config: env RTL_MCP_ROOTS="/path/a:/path/b" pre-builds at startup.
+"""
+import os, sys, json, io
+
+sys.stdout = io.TextIOWrapper(sys.stdout.buffer, encoding="utf-8", write_through=True)
+sys.stderr = io.TextIOWrapper(sys.stderr.buffer, encoding="utf-8", write_through=True)
+
+from rtl_index import RtlIndex
+
+IDX = None  # global index
+
+
+def _need_index():
+    if IDX is None or not IDX.db:
+        raise RuntimeError("index empty: call build_index first")
+
+
+# ---------------- tool implementations ----------------
+
+def t_build_index(args):
+    global IDX
+    roots = args.get("roots") or [r for r in os.environ.get("RTL_MCP_ROOTS", "").split(":") if r]
+    if not roots:
+        return dict(error="no roots given (pass roots[] or set RTL_MCP_ROOTS)")
+    t0 = os.times()
+    IDX = RtlIndex.build(roots)
+    n_always = sum(len(m["always"]) for m in IDX.db.values())
+    n_assign = sum(len(m["assigns"]) for m in IDX.db.values())
+    return dict(modules=len(IDX.db), cross_edges=len(IDX.edges),
+                assign_facts=n_assign, always_facts=n_always,
+                note="index in memory; use find_signal to locate, trace_drivers/trace_loads to follow")
+
+
+def t_list_modules(args):
+    _need_index()
+    pat = args.get("pattern")
+    import re
+    rx = re.compile(pat, re.I) if pat else None
+    out = []
+    for name, m in IDX.db.items():
+        if rx and not rx.search(name):
+            continue
+        out.append(dict(module=name,
+                        ports=len(m["ports"]), insts=len(m["insts"]),
+                        assigns=len(m["assigns"]), always=len(m["always"])))
+    return dict(modules=out[:80], total=len(out))
+
+
+def t_module_summary(args):
+    _need_index()
+    s = IDX.module_summary(args["module"])
+    if s is None:
+        return dict(error=f"module {args['module']} not found")
+    return s
+
+
+def t_find_signal(args):
+    _need_index()
+    hits = IDX.search(args["pattern"], limit=int(args.get("limit", 20)))
+    return dict(hits=hits)
+
+
+def _fmt_trace(rows):
+    lines = []
+    for r in rows:
+        rhs = ", ".join(r["rhs"][:6])
+        lines.append(f"[{r['kind']}] {r['where']} :: {r['sig']} <- {rhs}")
+    return lines
+
+
+def t_trace_drivers(args):
+    _need_index()
+    rows = IDX.drivers(args["module"], args["signal"],
+                       max_depth=int(args.get("depth", 4)))
+    if not rows:
+        return dict(result=[], text=f"no driver found for {args['module']}.{args['signal']} "
+                                    "(top input / testbench-driven / not indexed)")
+    lines = _fmt_trace(rows)
+    return dict(result=rows, text="\n".join(lines),
+                note="read chain bottom-up: leaf entries are the ultimate drivers; "
+                     "use get_source for file:line details")
+
+
+def t_trace_loads(args):
+    _need_index()
+    rows = IDX.loads(args["module"], args["signal"],
+                     max_depth=int(args.get("depth", 3)))
+    if not rows:
+        return dict(result=[], text=f"no loads found for {args['module']}.{args['signal']}")
+    lines = _fmt_trace(rows)
+    return dict(result=rows, text="\n".join(lines))
+
+
+_FMAP = None
+
+
+def _file_map():
+    """basename -> absolute path, built lazily by walking indexed roots."""
+    global _FMAP
+    if _FMAP is None:
+        _FMAP = {}
+        for r in getattr(IDX, "_roots", []) or []:
+            if os.path.isfile(r):
+                _FMAP.setdefault(os.path.basename(r), r)
+                continue
+            for dp, _dns, fns in os.walk(r):
+                for fn in fns:
+                    _FMAP.setdefault(fn, os.path.join(dp, fn))
+    return _FMAP
+
+
+def t_get_source(args):
+    path, start, end = args["file"], int(args["start"]), int(args["end"])
+    end = min(end, start + 200)
+    if not os.path.isabs(path):
+        # resolve by basename against indexed roots (files may sit in subdirs)
+        cand = _file_map().get(os.path.basename(path))
+        if cand:
+            path = cand
+    if not os.path.exists(path):
+        return dict(error=f"file not found: {path}")
+    out = []
+    with open(path, encoding="utf-8", errors="replace") as f:
+        for i, line in enumerate(f, 1):
+            if start <= i <= end:
+                out.append(f"{i:5d}| {line.rstrip()}")
+            if i > end:
+                break
+    return dict(text="\n".join(out))
+
+
+def t_hierarchy(args):
+    _need_index()
+    top = args["module"]
+    depth = int(args.get("depth", 2))
+    lines = []
+
+    def rec(mod, indent, d, seen):
+        if d > depth or (mod, indent) in seen or len(lines) > 80:
+            return
+        seen.add((mod, indent))
+        m = IDX.db.get(mod)
+        if not m:
+            return
+        for (itype, iname, conns) in m["insts"]:
+            lines.append(f"{'  ' * (indent + 1)}└─ {iname} : {itype}")
+            rec(itype, indent + 1, d + 1, seen)
+
+    lines.append(top)
+    rec(top, 0, 0, set())
+    return dict(text="\n".join(lines))
+
+
+TOOLS = {
+    "build_index":    (t_build_index, "Build the signal-flow index. roots: list of files or directories to scan (.v/.sv)."),
+    "list_modules":   (t_list_modules, "List indexed modules (name, ports, insts, fact counts). pattern: optional regex."),
+    "module_summary": (t_module_summary, "Compact summary of one module: port list, instances with connected nets, net names."),
+    "find_signal":    (t_find_signal, "Find signals by regex. Returns module + file:line for each hit."),
+    "trace_drivers":  (t_trace_drivers, "Trace WHO drives a signal — recursive across module boundaries (Verdi-style). Args: module, signal, depth=4."),
+    "trace_loads":    (t_trace_loads, "Trace WHAT a signal drives — loads in same module, flows out output ports, feeds child instances. Args: module, signal, depth=3."),
+    "get_source":     (t_get_source, "Read a small source excerpt (file, start, end; max 200 lines). Use after tracing to see the exact logic."),
+    "hierarchy":      (t_hierarchy, "Instantiation tree under a module. Args: module, depth=2."),
+}
+
+TOOLSPEC = [dict(name=n, description=d,
+                 inputSchema=dict(type="object",
+                                  properties={},
+                                  additionalProperties=True))
+            for n, (f, d) in TOOLS.items()]
+
+
+# ---------------- JSON-RPC / MCP plumbing ----------------
+
+def reply(msg_id, result):
+    sys.stdout.write(json.dumps(dict(jsonrpc="2.0", id=msg_id, result=result)) + "\n")
+
+
+def reply_error(msg_id, code, message):
+    sys.stdout.write(json.dumps(dict(jsonrpc="2.0", id=msg_id,
+                                     error=dict(code=code, message=message))) + "\n")
+
+
+def handle(req):
+    method = req.get("method")
+    msg_id = req.get("id")
+    if method == "initialize":
+        reply(msg_id, dict(protocolVersion="2024-11-05",
+                           capabilities=dict(tools={}),
+                           serverInfo=dict(name="rtl-signal-mcp", version="0.1.0")))
+    elif method == "notifications/initialized":
+        pass
+    elif method == "tools/list":
+        reply(msg_id, dict(tools=TOOLSPEC))
+    elif method == "tools/call":
+        params = req.get("params", {})
+        name = params.get("name")
+        args = params.get("arguments", {}) or {}
+        fn = TOOLS.get(name)
+        if fn is None:
+            reply_error(msg_id, -32602, f"unknown tool {name}")
+            return
+        try:
+            res = fn[0](args)
+            text = res.pop("text", None) or json.dumps(res, ensure_ascii=False)
+            reply(msg_id, dict(content=[dict(type="text", text=text)],
+                               structuredContent=res, isError=False))
+        except Exception as e:
+            reply(msg_id, dict(content=[dict(type="text", text=f"error: {e}")], isError=True))
+    elif method == "ping":
+        reply(msg_id, {})
+    elif msg_id is not None:
+        reply_error(msg_id, -32601, f"method not supported: {method}")
+
+
+def main():
+    if os.environ.get("RTL_MCP_ROOTS"):
+        try:
+            res = t_build_index({})
+            print(f"[rtl-signal-mcp] prebuilt index: {res}", file=sys.stderr)
+        except Exception as e:
+            print(f"[rtl-signal-mcp] prebuild failed: {e}", file=sys.stderr)
+    for line in sys.stdin:
+        line = line.strip()
+        if not line:
+            continue
+        try:
+            req = json.loads(line)
+        except Exception:
+            continue
+        try:
+            handle(req)
+        except Exception as e:
+            if req.get("id") is not None:
+                reply_error(req["id"], -32603, str(e))
+
+
+if __name__ == "__main__":
+    main()

rtl-mcp/rtl_index.py

@@ -0,0 +1,356 @@
+#!/usr/bin/env python3
+"""rtl_index.py — RTL signal-flow index for cross-module tracing.
+
+Builds a module-fact database from Verilog/SystemVerilog sources:
+  ports (ANSI & non-ANSI), nets, continuous assigns, always-block drivers,
+  instantiations with named port connections, and cross-boundary edges.
+
+pyslang 11 API. Index build is O(source); queries are in-memory graph walks.
+"""
+import os, re, json, glob
+import pyslang
+from pyslang import syntax as sl
+
+IDENT = re.compile(r"^[A-Za-z_][A-Za-z0-9_$]*$")
+ASSIGN_KINDS = ("AssignmentExpression", "NonblockingAssignmentExpression")
+
+
+def _txt(node):
+    t = getattr(node, "valueText", "")
+    return t if t else (str(node).strip() if node is not None else "")
+
+
+def _syntax_of(val_node):
+    s = getattr(val_node, "syntax", None)
+    return s if s is not None else val_node
+
+
+def ids_from(expr_syntax):
+    out = []
+    def walk(n):
+        if n is None:
+            return
+        if n.kind in (sl.SyntaxKind.IdentifierName, sl.SyntaxKind.IdentifierSelectName):
+            ident = getattr(n, "identifier", None)
+            if ident is not None:
+                t = _txt(ident)
+                if IDENT.match(t):
+                    out.append(t)
+            # IdentifierSelectName has .target identifier inside
+            tgt = getattr(n, "target", None)
+            if tgt is not None:
+                walk(tgt)
+            return
+        for c in n:
+            if hasattr(c, "__iter__"):
+                walk(c)
+    walk(expr_syntax)
+    return out
+
+
+def _lhs_names(expr_syntax):
+    """names written by an assignment LHS (plain idents only, strip selects)"""
+    out = []
+    def walk(n):
+        if n is None:
+            return
+        if n.kind == sl.SyntaxKind.IdentifierName:
+            t = _txt(n.identifier)
+            if IDENT.match(t):
+                out.append(t)
+            return
+        for c in n:
+            if hasattr(c, "__iter__"):
+                walk(c)
+    walk(expr_syntax)
+    return out
+
+
+class RtlIndex:
+    def __init__(self):
+        self.sm = pyslang.SourceManager()
+        self.db = {}        # module -> facts
+        self.edges = []     # (parent_mod, parent_net, child_mod, child_port, child_dir, inst_name)
+        self.loc = {}       # (module, signal) -> "file:line"
+
+    # ---------- build ----------
+    def add_tree(self, path):
+        tree = sl.SyntaxTree.fromFile(path, self.sm)
+        root = tree.root
+        for m in root.members:
+            if m.kind == sl.SyntaxKind.ModuleDeclaration:
+                info = self._scan_module(m)
+                self.db[info["name"]] = info
+
+    def _record_loc(self, module, name, node):
+        try:
+            if type(node).__name__ == "Token":
+                tok = node
+            else:
+                tok = node.getFirstToken()
+            if tok is not None:
+                self.loc[(module, name)] = (
+                    os.path.basename(self.sm.getFileName(tok.location)),
+                    self.sm.getLineNumber(tok.location))
+        except Exception:
+            pass
+
+    def _scan_module(self, mod):
+        name = _txt(mod.header.name)
+        info = dict(name=name, ports=[], nets=[], assigns=[], always=[], insts=[])
+        self._record_loc(name, name, mod.header.name)
+
+        # ---- ports (ANSI) ----
+        pl = mod.header.ports
+        if pl is not None:
+            for p in pl:
+                if type(p).__name__ == "Token":
+                    continue
+                try:
+                    d = getattr(p, "declarator", None)
+                    if d is None or d.name is None:
+                        # explicit port like .name(expr) or non-ansi header decl — skip here
+                        continue
+                    pname = _txt(d.name)
+                    h = p.header
+                    dtok = getattr(h, "direction", None)
+                    dtext = (_txt(dtok).capitalize() if dtok is not None else "In")
+                    info["ports"].append((dtext, pname))
+                    self._record_loc(name, pname, d.name)
+                except Exception:
+                    continue
+
+        # ---- members ----
+        for m in mod.members:
+            k = m.kind
+            if k in (sl.SyntaxKind.DataDeclaration, sl.SyntaxKind.NetDeclaration):
+                for d in m.declarators:
+                    if type(d).__name__ == "Token":
+                        continue
+                    dn = getattr(d, "name", None)
+                    if dn is not None:
+                        n = _txt(dn)
+                        info["nets"].append(n)
+                        self._record_loc(name, n, dn)
+            elif k == sl.SyntaxKind.ContinuousAssign:
+                for a in m.assignments:
+                    if type(a).__name__ == "Token":
+                        continue
+                    lhs_ids = _lhs_names(a.left) if getattr(a, "left", None) is not None else []
+                    rhs_ids = ids_from(a.right) if a.right is not None else []
+                    if lhs_ids:
+                        info["assigns"].append((lhs_ids[0], rhs_ids))
+                        self._record_loc(name, lhs_ids[0], m.getFirstToken())
+            elif k in (sl.SyntaxKind.AlwaysBlock, sl.SyntaxKind.AlwaysFFBlock,
+                       sl.SyntaxKind.AlwaysCombBlock, sl.SyntaxKind.AlwaysLatchBlock):
+                self._scan_always(name, m, info)
+            elif k == sl.SyntaxKind.HierarchyInstantiation:
+                self._scan_inst(name, m, info)
+        info["nets"] = sorted(set(info["nets"]))
+        return info
+
+    def _scan_always(self, mod_name, m, info):
+        if getattr(m, "statement", None) is None:
+            return
+        def walk_stmt(s, depth=0):
+            if s is None or depth > 40:
+                return
+            k = s.kind
+            if k == sl.SyntaxKind.ExpressionStatement:
+                e = s.expr
+                ek = str(e.kind)
+                if any(a in ek for a in ASSIGN_KINDS):
+                    lt = _syntax_of(e.left) if e.left is not None else None
+                    rt = _syntax_of(e.right) if e.right is not None else None
+                    lhs = _lhs_names(lt) if lt is not None else []
+                    rhs = ids_from(rt) if rt is not None else []
+                    if lhs:
+                        info["always"].append((lhs[0], rhs))
+                        self._record_loc(mod_name, lhs[0], s.getFirstToken())
+                return
+            # descend through timing/if/for/case wrappers
+            inner = getattr(s, "statement", None)
+            if inner is not None and hasattr(inner, "kind"):
+                walk_stmt(inner, depth + 1)
+            if k == sl.SyntaxKind.ConditionalStatement:
+                cons = getattr(s, "statement", None)
+                alt = getattr(s, "elseStatement", None)
+                for part in (cons, alt):
+                    if part is not None and hasattr(part, "kind"):
+                        walk_stmt(part, depth + 1)
+                return
+            if hasattr(s, "__iter__"):
+                for c in s:
+                    tn = type(c).__name__
+                    if hasattr(c, "__iter__") and ("Statement" in tn or "Case" in tn
+                                                   or "Generate" in tn or "Block" in tn):
+                        walk_stmt(c, depth + 1)
+        walk_stmt(m.statement)
+
+    def _scan_inst(self, mod_name, m, info):
+        tnode = m.type
+        itype = _txt(tnode.valueText if hasattr(tnode, "valueText") else tnode)
+        itype = itype.split()[-1] if itype.split() else "?"
+        for inst in m.instances:
+            conns = []
+            try:
+                for pc in inst.connections:
+                    if type(pc).__name__ == "Token":
+                        continue
+                    nm = getattr(pc, "name", None)
+                    if nm is None:
+                        continue
+                    pname = _txt(nm)
+                    expr_ids = ids_from(pc.expr) if getattr(pc, "expr", None) is not None else []
+                    conns.append((pname, expr_ids))
+            except Exception:
+                pass
+            iname = _txt(inst.decl.name) if inst.decl is not None and inst.decl.name else "?"
+            info["insts"].append((itype, iname, conns))
+
+    # ---------- finalize ----------
+    def finalize(self):
+        self.edges = []
+        for mod in self.db.values():
+            for (itype, iname, conns) in mod["insts"]:
+                child = self.db.get(itype)
+                if not child:
+                    continue
+                cports = {pn: d for d, pn in child["ports"]}
+                for (pname, pids) in conns:
+                    cdir = cports.get(pname)
+                    if cdir is None or not pids:
+                        continue
+                    for pid in pids:
+                        self.edges.append((mod["name"], pid, itype, pname, cdir, iname))
+        # adjacency for speed
+        self.in_by_child = {}
+        for e in self.edges:
+            if e[4].lower().startswith("in"):
+                self.in_by_child.setdefault((e[2], e[3]), []).append(e)
+        self.out_by_child = {}
+        for e in self.edges:
+            if e[4].lower().startswith("out"):
+                self.out_by_child.setdefault((e[2], e[3]), []).append(e)
+
+    # ---------- queries ----------
+    def drivers(self, module, sig, max_depth=4, max_nodes=60):
+        seen, out, rowseen = set(), [], set()
+        def rec(mod_name, s, depth):
+            if len(out) >= max_nodes or depth > max_depth or (mod_name, s) in seen:
+                return
+            seen.add((mod_name, s))
+            m = self.db.get(mod_name)
+            if not m:
+                return
+            for lhs, rhs in m["assigns"]:
+                if lhs == s:
+                    loc = self.loc.get((mod_name, lhs), ("?", "?"))
+                    out.append(dict(kind="assign", where=f"{mod_name}  ({loc[0]}:{loc[1]})",
+                                    sig=lhs, rhs=rhs[:8]))
+                    for r in rhs[:3]:
+                        rec(mod_name, r, depth + 1)
+            for lhs, rhs in m["always"]:
+                if lhs == s:
+                    loc = self.loc.get((mod_name, lhs), ("?", "?"))
+                    out.append(dict(kind="always", where=f"{mod_name}  ({loc[0]}:{loc[1]})",
+                                    sig=lhs, rhs=rhs[:8]))
+                    for r in rhs[:3]:
+                        rec(mod_name, r, depth + 1)
+            pdirs = {pn: d for d, pn in m["ports"]}
+            if str(pdirs.get(s, "")).lower().startswith("in"):
+                for (pm, pid, cm, cp, cdir, iname) in self.in_by_child.get((mod_name, s), []):
+                    out.append(dict(kind="port-in", where=f"from {pm}.{iname}",
+                                    sig=f".{cp}", rhs=[pid]))
+                    rec(pm, pid, depth + 1)
+            for (itype, iname, conns) in m["insts"]:
+                for (pname, pids) in conns:
+                    if s in pids:
+                        child = self.db.get(itype)
+                        if child:
+                            cdirs = {pn: d for d, pn in child["ports"]}
+                            if str(cdirs.get(pname, "")).lower().startswith("out"):
+                                out.append(dict(kind="inst-out",
+                                                where=f"{mod_name}.{iname} ({itype}.{pname})",
+                                                sig=s, rhs=[f"{itype}.{pname}"]))
+                                rec(itype, pname, depth + 1)
+        rec(module, sig, 0)
+        return [r for r in out
+                if not (key := (r['kind'], r['where'], r['sig'], tuple(r['rhs']))) in rowseen and not rowseen.add(key)]
+
+    def loads(self, module, sig, max_depth=3, max_nodes=60):
+        """who reads sig (same module) and where does it flow (output port / down into insts)"""
+        seen, out, rowseen = set(), [], set()
+        def rec(mod_name, s, depth):
+            if len(out) >= max_nodes or depth > max_depth or (mod_name, s) in seen:
+                return
+            seen.add((mod_name, s))
+            m = self.db.get(mod_name)
+            if not m:
+                return
+            for lhs, rhs in m["assigns"] + m["always"]:
+                if s in rhs:
+                    loc = self.loc.get((mod_name, lhs), ("?", "?"))
+                    out.append(dict(kind="load", where=f"{mod_name}  ({loc[0]}:{loc[1]})",
+                                    sig=lhs, rhs=[s]))
+                    rec(mod_name, lhs, depth + 1)
+            pdirs = {pn: d for d, pn in m["ports"]}
+            if str(pdirs.get(s, "")).lower().startswith("out"):
+                for (pm, pid, cm, cp, cdir, iname) in self.out_by_child.get((mod_name, s), []):
+                    out.append(dict(kind="port-out", where=f"into {pm} (as {pid}, via {iname})",
+                                    sig=f".{cp}", rhs=[pid]))
+                    rec(pm, pid, depth + 1)
+            for (itype, iname, conns) in m["insts"]:
+                for (pname, pids) in conns:
+                    if s in pids:
+                        child = self.db.get(itype)
+                        cdirs = {pn: d for d, pn in child["ports"]} if child else {}
+                        kind = cdirs.get(pname, "?")
+                        out.append(dict(kind=f"inst-load-{kind.lower() or 'unk'}",
+                                        where=f"{mod_name}.{iname} -> {itype}.{pname}",
+                                        sig=s, rhs=[pname]))
+        rec(module, sig, 0)
+        return [r for r in out
+                if not (key := (r['kind'], r['where'], r['sig'], tuple(r['rhs']))) in rowseen and not rowseen.add(key)]
+
+    def module_summary(self, name):
+        m = self.db.get(name)
+        if not m:
+            return None
+        return dict(name=m["name"],
+                    ports=[f"{d} {p}" for d, p in m["ports"]],
+                    nets=m["nets"][:120],
+                    n_assign=len(m["assigns"]), n_always=len(m["always"]),
+                    insts=[dict(type=t, name=i, ports=[f".{p}({','.join(ids[:3])})" for p, ids in c][:16])
+                           for t, i, c in m["insts"]])
+
+    def search(self, pat, limit=20):
+        rx = re.compile(pat, re.I)
+        hits = []
+        for (mod, sig), (f, l) in self.loc.items():
+            if rx.search(sig) and len(hits) < limit:
+                hits.append(dict(module=mod, signal=sig, file=f, line=l))
+        return hits
+
+    def save(self, path):
+        with open(path, "w", encoding="utf-8") as f:
+            json.dump(dict(modules=list(self.db), n_edges=len(self.edges)), f)
+
+    @classmethod
+    def build(cls, roots):
+        idx = cls()
+        files = []
+        for r in roots:
+            if os.path.isfile(r):
+                files.append(r)
+            else:
+                files += glob.glob(os.path.join(r, "**", "*.v"), recursive=True)
+                files += glob.glob(os.path.join(r, "**", "*.sv"), recursive=True)
+        idx._roots = [os.path.abspath(r) for r in roots]
+        for f in sorted(set(files)):
+            try:
+                idx.add_tree(f)
+            except Exception:
+                pass
+        idx.finalize()
+        return idx