ptr[0] *= 2.0;
  ptr[1] *= 2.0;
  ptr += 2;

  loop(2, ptr[0] *= 2.0; ptr+=1; );

   foo = (x*y+z)*3.0;

   tmp = x*y+z;
   foo = tmp * 3.0;

• Linux: anything with gnu libc and gcc 4.x (eg debian)
• macOS: if you want to support older (pre-10.15), then Xcode 9 or so, and any OS that supports that
• macOS: if you want to support newer 10.15+ and arm64, Xcode 11+, and an OS that supports that
• Windows: any VC version that supports the OSes you want to support, we use 2005 with ICC, but 2013 should be fine. Probably want to static link the runtime to avoid a dependency there.