mesonbuild: move subdir generation along link dep generation

The problem with the earlier position of the generation code was, that
the results could not be cached, because the list of all link_deps was
overall different. However, it shared a special kind of subsets with
other build build targets.

Generating the set of subdirs that are required for linking, alongside
with the link dependencies brings the possibility of caching this.
This reduces the buildting from 1 min. in efl down to 20 sec. And
reduces the amount of 30872534 calls down.

this saves ~40 sec.

2 files changed, 14 insertions, 7 deletions

diff --git a/mesonbuild/backend/backends.py b/mesonbuild/backend/backends.py
index a6bec06..8153ff7 100644
--- a/mesonbuild/backend/backends.py
+++ b/mesonbuild/backend/backends.py
@@ -394,12 +394,11 @@ class Backend:
         return paths
 
     def determine_rpath_dirs(self, target):
-        link_deps = target.get_all_link_deps()
-        result = OrderedSet()
-        for ld in link_deps:
-            if ld is target:
-                continue
-            result.add(self.get_target_dir(ld))
+        if self.environment.coredata.get_builtin_option('layout') == 'mirror':
+            result = target.get_link_dep_subdirs()
+        else:
+            result = OrderedSet()
+            result.add('meson-out')
         result.update(self.rpaths_for_bundled_shared_libraries(target))
         return list(result)
 
diff --git a/mesonbuild/build.py b/mesonbuild/build.py
index e8af2b6..b86c84d 100644
--- a/mesonbuild/build.py
+++ b/mesonbuild/build.py
@@ -21,7 +21,7 @@ from functools import lru_cache
 from . import environment
 from . import dependencies
 from . import mlog
-from .mesonlib import File, MesonException, listify, extract_as_list
+from .mesonlib import File, MesonException, listify, extract_as_list, OrderedSet
 from .mesonlib import typeslistify, stringlistify, classify_unity_sources
 from .mesonlib import get_filenames_templates_dict, substitute_values
 from .mesonlib import for_windows, for_darwin, for_cygwin, for_android, has_path_sep
@@ -676,6 +676,14 @@ class BuildTarget(Target):
             result += i.get_all_link_deps()
         return result
 
+    @lru_cache(maxsize=None)
+    def get_link_dep_subdirs(self):
+        result = OrderedSet()
+        for i in self.link_targets:
+            result.add(i.get_subdir())
+            result.update(i.get_link_dep_subdirs())
+        return result
+
     def get_custom_install_dir(self):
         return self.install_dir