element: Create a specialised build-dep cachekey functiondanielsilverstone-ct/iterative-deps

This speeds up cache key generation somewhat.

Signed-off-by: Daniel Silverstone <daniel.silverstone@codethink.co.uk>

2 files changed, 23 insertions, 4 deletions

diff --git a/src/buildstream/_element.pyx b/src/buildstream/_element.pyx
index 56fa5f141..3beeb3512 100644
--- a/src/buildstream/_element.pyx
+++ b/src/buildstream/_element.pyx
@@ -109,3 +109,24 @@ def recursive_dependencies_helper(element, scope, visited):
     else:
         # Scope.NONE, unusual here.
         yield element
+
+def build_deps_cachekeys_helper(element):
+    ret = []
+    visit_stack = []
+    runtime_visited = BitMap()
+
+    for dep in reversed(element._Element__build_dependencies):
+        visit_stack.append((dep, False))
+
+    while visit_stack:
+        element, visited = visit_stack.pop()
+        if visited:
+            ret.append(element._Element__strict_cache_key)
+        elif element._unique_id not in runtime_visited:
+            runtime_visited.add(element._unique_id)
+            visit_stack.append((element, True))
+            visit_stack.extend((
+                (dep, False) for dep in reversed(element._Element__runtime_dependencies)
+                if dep._unique_id not in runtime_visited))
+
+    return ret
diff --git a/src/buildstream/element.py b/src/buildstream/element.py
index 57322293d..e8d8dad6a 100644
--- a/src/buildstream/element.py
+++ b/src/buildstream/element.py
@@ -108,7 +108,7 @@ from .storage._filebaseddirectory import FileBasedDirectory
 from .storage._casbaseddirectory import CasBasedDirectory
 from .storage.directory import VirtualDirectoryError
 
-from ._element import recursive_dependencies_helper
+from ._element import recursive_dependencies_helper, build_deps_cachekeys_helper
 
 class ElementError(BstError):
     """This exception should be raised by :class:`.Element` implementations
@@ -2902,9 +2902,7 @@ class Element(Plugin):
                 return
 
         if self.__strict_cache_key is None:
-            dependencies = [
-                e.__strict_cache_key for e in self.dependencies(Scope.BUILD)
-            ]
+            dependencies = build_deps_cachekeys_helper(self)
             self.__strict_cache_key = self._calculate_cache_key(dependencies)
 
     # __update_artifact_state()