diff --git a/tasks.py b/tasks.py
index e40f3c9..5e2fb62 100644
--- a/tasks.py
+++ b/tasks.py
@@ -24,18 +24,45 @@ def bsc_root(c):
             return Path(l[len(dir_prefix):])
     raise RuntimeError("Couldn't locate Bluespec root dir")
 
-def find_verilog_modules(c, modules):
-    libpaths = [Path("lib"), bsc_root(c) / "Verilog"]
+def bluespec_libdirs(*extras):
+    ret = []
+    for x in extras:
+        x = Path(x)
+        if not x.is_dir():
+            x = x.parent
+            if not x.is_dir():
+                raise ValueError(f"unknown libdir thing {x}")
+        ret.append(x)
+
+    bsv_dirs = list(sorted(set(p.parent for p in Path("").glob("**/*.bsv"))))
+    exclude_trees = [Path("hardware"), Path("experiments"), Path("sim")] + ret
+    for d in bsv_dirs:
+        if any(d.is_relative_to(x) for x in exclude_trees):
+            continue
+        ret.append(d)
+    ret.append("%/Libraries")
+    return ":".join(str(s) for s in ret)
+
+def find_verilog_modules(c, target_dir, modules):
+    preferred_libpaths = [target_dir, Path("lib"), bsc_root(c) / "Verilog"]
     ret = []
     for module in modules:
         module_path = None
+        verilog_path = Path(module).with_suffix(".v")
+        # Try preferred libpaths first.
         for p in libpaths:
-            f = p / Path(module).with_suffix(".v")
+            f = p / verilog_path
             if f.is_file():
                 module_path = f
                 break
         if module_path is None:
-            raise RuntimeError(f"Cannot find verilog module {module} in {libpaths}")
+            # Not in preferred paths, accept anywhere now.
+            matches = Path("").glob(f"**/{module}.v")
+            if len(matches) > 1:
+                raise RuntimeError(f"Multiple candidates for verilog module {module}: {matches}")
+            elif len(matches) == 0:
+                raise RuntimeError(f"Cannot find verilog module {module} in {libpaths}")
+            module_path = matches[0]
         ret.append(module_path)
     return ret
 
@@ -82,14 +109,16 @@ def phase(name):
     print("")
 
 @task
-def build(c, target="."):
+def build(c, target):
     phase("Compile Bluespec")
 
     verilog_files = []
     for target in expand_build_target(target):
         out_info, out_verilog, out_bsc = ensure_build_dirs(target, "info", "verilog", "bsc")
+        libdirs = bluespec_libdirs(target)
         print(f"Building {target}")
-        c.run(f"bsc -aggressive-conditions -check-assert -remove-dollar -remove-empty-rules -remove-false-rules -remove-starved-rules -verilog-filter scripts/basicinout.pl -show-method-conf -show-method-bvi -u -verilog -info-dir {out_info} -vdir {out_verilog} -bdir {out_bsc} -p {target.parent}:vram:lib:%/Libraries -show-module-use -show-compiles {target}")
+        print(f"Libdirs: {libdirs.replace(':', ', ')}")
+        c.run(f"bsc -aggressive-conditions -check-assert -remove-dollar -remove-empty-rules -remove-false-rules -remove-starved-rules -verilog-filter scripts/basicinout.pl -show-method-conf -show-method-bvi -u -verilog -info-dir {out_info} -vdir {out_verilog} -bdir {out_bsc} -p {libdirs} -show-module-use -show-compiles {target}")
 
         module_name = Path(f"mk{target.stem}")
         verilog_main_file = out_verilog / module_name.with_suffix(".v")
@@ -98,7 +127,7 @@ def build(c, target="."):
         use_file = out_verilog / module_name.with_suffix(".use")
         if use_file.is_file():
             with open(out_verilog / module_name.with_suffix(".use")) as f:
-                verilog_files.extend(find_verilog_modules(c, f.read().splitlines()))
+                verilog_files.extend(find_verilog_modules(c, target.parent, f.read().splitlines()))
 
     if verilog_files:
         print("\nVerilog files for synthesis:")
@@ -187,7 +216,9 @@ def synth(c, target):
 def test(c, target):
     for target in expand_test_target(target):
         out_info, out_sim, out_bsc = ensure_build_dirs(target, "info", "sim", "bsc")
-        c.run(f"bsc -show-schedule -aggressive-conditions -check-assert -u -sim -info-dir {out_info} -simdir {out_sim} -bdir {out_bsc} -g mkTB -p {target.parent}:lib:sim:%/Libraries {target}")
+        libdirs = bluespec_libdirs(target, "sim")
+        print(f"Libdirs: {libdirs.replace(':', ', ')}")
+        c.run(f"bsc -show-schedule -aggressive-conditions -check-assert -u -sim -info-dir {out_info} -simdir {out_sim} -bdir {out_bsc} -g mkTB -p {libdirs} {target}")
         exec = out_sim / "TB"
         c.run(f"bsc -p {out_bsc} -sim -simdir {out_sim} -e mkTB -o {exec}")
         testdata = out_sim / "testdata"