https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58950
nightstrike <nightstrike at gmail dot com> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |nightstrike at gmail dot com --- Comment #23 from nightstrike <nightstrike at gmail dot com> --- Given that Comment #1 clearly shows g++ 4.8 working, I think this should qualify as a regression. Moreover, g++ 6.2 works correctly, so this was fixed at some point between 4.9 and 6.2: $ cat > a.cc void f() { int i __attribute__((vector_size(2*sizeof(int))))={2,3}; __builtin_shuffle(i,i); } $ g++ -c a.cc -Wunused-value a.cc: In function 'void f()': a.cc:3:3: warning: value computed is not used [-Wunused-value] __builtin_shuffle(i,i); ^~~~~~~~~~~~~~~~~