+/* Construct the pass tree. The sequencing of passes is driven by
+ the cgraph routines:
+
+ cgraph_finalize_compilation_unit ()
+ for each node N in the cgraph
+ cgraph_analyze_function (N)
+ cgraph_lower_function (N) -> all_lowering_passes
+
+ If we are optimizing, cgraph_optimize is then invoked:
+
+ cgraph_optimize ()
+ ipa_passes () -> all_ipa_passes
+ cgraph_expand_all_functions ()
+ for each node N in the cgraph
+ cgraph_expand_function (N)
+ cgraph_lower_function (N) -> Now a NOP.
+ lang_hooks.callgraph.expand_function (DECL (N))
+ tree_rest_of_compilation (DECL (N)) -> all_passes
+*/