https://gcc.gnu.org/bugzilla/show_bug.cgi?id=121623
--- Comment #13 from Sam James <sjames at gcc dot gnu.org> --- The preprocessed source should be identical between stage2 and stage3 so it doesn't matter which you use. Just grep through the build.log for the last command used to build trans-mem.o, run it manually (perhaps adjusting some paths), append -save-temps, then find trans-mem.ii.
