I'm unimpressed that x64 assumes function calls write the return address to stack memory instead of passing it in a register. It means you have to use the stack

I'm unimpressed that x64 assumes function calls write the return address to stack memory instead of passing it in a register. It means you have to use the stack memory in order to benefit from the call/ret prediction hardware, even in functions which don't otherwise need to allocate any stack memory. In general leaking microarch weirdness matters less if you don't have backwards compatibility.