http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50384
--- Comment #3 from Marc Glisse <marc.glisse at normalesup dot org> 2012-01-28 20:17:20 UTC --- (In reply to comment #2) > The issue with comment #1 is simple, f is not being marked as a tail call. Marking it as a tail call would indeed work for that case. In this slight variation however, I get a similar long copying to move the return value to an argument for the next call, where I would expect the compiler to just move the 64bit register that contains it. #include <array> typedef std::array<char,7> X; void h(X); X f(X,X); void g(X a,X b){h(f(a,b));}