Mostly, yeah. But microarchitectures do sometimes add new instruction set extensions, like how Intel's Skylake added AVX-512. Bitcode can be re-lowered to the

Mostly, yeah. But microarchitectures do sometimes add new instruction set extensions, like how Intel's Skylake added AVX-512. Bitcode can be re-lowered to the new extended ISA to use these instructions (assuming you don't need to target earlier uarchs). Machine code, not as easily (and I don't think anyone really tries, though I'd be interested to learn if someone does).