[Bug tree-optimization/93843] [10 Regression] wrong code at -O3 on x86_64-linux-gnu

[kretz at kde dot org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93843

--- Comment #7 from Matthias Kretz (Vir) <kretz at kde dot org> ---
This one exhibits the issue without -ftree-vectorize (`-O1` suffices) (cf.
https://godbolt.org/z/Swx-jW):

using M [[gnu::vector_size(2)]] = char;
using MM [[gnu::vector_size(4)]] = short;

MM
cvt(M x)
{
  return MM{short(x[0]), short(x[1])};
}