Micro-optimize finding executables (#45740)

2 files changed, 8 insertions, 11 deletions

diff --git a/lib/spack/spack/detection/common.py b/lib/spack/spack/detection/common.py
index ae3c1927d2..e043c6fb8a 100644
--- a/lib/spack/spack/detection/common.py
+++ b/lib/spack/spack/detection/common.py
@@ -136,10 +136,10 @@ def path_to_dict(search_paths: List[str]):
     # entry overrides later entries
     for search_path in reversed(search_paths):
         try:
-            for lib in os.listdir(search_path):
-                lib_path = os.path.join(search_path, lib)
-                if llnl.util.filesystem.is_readable_file(lib_path):
-                    path_to_lib[lib_path] = lib
+            with os.scandir(search_path) as entries:
+                path_to_lib.update(
+                    {entry.path: entry.name for entry in entries if entry.is_file()}
+                )
         except OSError as e:
             msg = f"cannot scan '{search_path}' for external software: {str(e)}"
             llnl.util.tty.debug(msg)
diff --git a/lib/spack/spack/detection/path.py b/lib/spack/spack/detection/path.py
index 943de16ee6..01b83b5472 100644
--- a/lib/spack/spack/detection/path.py
+++ b/lib/spack/spack/detection/path.py
@@ -335,13 +335,10 @@ class ExecutablesFinder(Finder):
 
     def candidate_files(self, *, patterns: List[str], paths: List[str]) -> List[str]:
         executables_by_path = executables_in_path(path_hints=paths)
-        patterns = [re.compile(x) for x in patterns]
-        result = []
-        for compiled_re in patterns:
-            for path, exe in executables_by_path.items():
-                if compiled_re.search(exe):
-                    result.append(path)
-        return list(sorted(set(result)))
+        joined_pattern = re.compile(r"|".join(patterns))
+        result = [path for path, exe in executables_by_path.items() if joined_pattern.search(exe)]
+        result.sort()
+        return result
 
     def prefix_from_path(self, *, path: str) -> str:
         result = executable_prefix(path)