Bug 1370296 - Add compile graphs nodes without dependencies as direct dependencies of the top recursion target. r=gps

Incidentally, this prioritizes js/src even more than it was after bug 1262241.

--HG--
extra : rebase_source : 904fad5ca9a29c7b2a1b33fdf500f98f70904118

python/mozbuild/mozbuild/backend/recursivemake.py

@@ -742,7 +742,20 @@ class RecursiveMakeBackend(CommonBackend):
 
         all_compile_deps = reduce(lambda x,y: x|y,
             self._compile_graph.values()) if self._compile_graph else set()
-        compile_roots = set(self._compile_graph.keys()) - all_compile_deps
+        # Include the following as dependencies of the top recursion target for
+        # compilation:
+        # - nodes that are not dependended upon by anything. Typically, this
+        #   would include programs, that need to be recursed, but that nothing
+        #   depends on.
+        # - nodes that have no dependencies of their own. Technically, this is
+        #   not necessary, because other things have dependencies on them, and
+        #   they all end up rooting to nodes from the above category. But the
+        #   way make works[1] is such that there can be benefits listing them
+        #   as direct dependencies of the top recursion target, to somehow
+        #   prioritize them.
+        #   1. See bug 1262241 comment 5.
+        compile_roots = [t for t, deps in self._compile_graph.iteritems()
+                         if not deps or t not in all_compile_deps]
 
         rule = root_deps_mk.create_rule(['recurse_compile'])
         rule.add_dependencies(compile_roots)