Speedup the default 'libs' property search ... (#7553)

* Speedup the default 'libs' property search - important for external
packages.

* As advised by @alalazo, use tuples instead of lists inside
_libs_default_handler.

1 files changed, 21 insertions, 24 deletions

diff --git a/lib/spack/spack/spec.py b/lib/spack/spack/spec.py
index 68fa632e9e..35ab59f76a 100644
--- a/lib/spack/spack/spec.py
+++ b/lib/spack/spack/spec.py
@@ -729,31 +729,28 @@ def _libs_default_handler(descriptor, spec, cls):
     # unlikely).
     name = 'lib' + spec.name.replace('-', '?')
 
-    if '+shared' in spec:
-        libs = find_libraries(
-            name, root=spec.prefix, shared=True, recursive=True
-        )
-    elif '~shared' in spec:
-        libs = find_libraries(
-            name, root=spec.prefix, shared=False, recursive=True
-        )
-    else:
-        # Prefer shared
-        libs = find_libraries(
-            name, root=spec.prefix, shared=True, recursive=True
-        )
-        if libs:
-            return libs
-
-        libs = find_libraries(
-            name, root=spec.prefix, shared=False, recursive=True
-        )
+    # To speedup the search for external packages configured e.g. in /usr,
+    # perform first non-recursive search in prefix.lib then in prefix.lib64 and
+    # finally search all of prefix recursively. The search stops when the first
+    # match is found.
+    prefix = spec.prefix
+    search_paths = [(prefix.lib, False), (prefix.lib64, False), (prefix, True)]
+
+    # If '+shared' search only for shared library; if '~shared' search only for
+    # static library; otherwise, first search for shared and then for static.
+    search_shared = [True] if ('+shared' in spec) else \
+        ([False] if ('~shared' in spec) else [True, False])
+
+    for shared in search_shared:
+        for path, recursive in search_paths:
+            libs = find_libraries(
+                name, root=path, shared=shared, recursive=recursive
+            )
+            if libs:
+                return libs
 
-    if libs:
-        return libs
-    else:
-        msg = 'Unable to recursively locate {0} libraries in {1}'
-        raise RuntimeError(msg.format(spec.name, spec.prefix))
+    msg = 'Unable to recursively locate {0} libraries in {1}'
+    raise RuntimeError(msg.format(spec.name, prefix))
 
 
 class ForwardQueryToPackage(object):