There are already plenty of architectural differences that change optimal trade-offs in the code, e.g. memory speed affects lookup tables vs recomputation choice and inlined data vs pointer chasing, branch prediction cost affects conditionals vs branchless/redundant code, data layout needs to be adjusted for SIMD and cache line sizes, memory hierarchy and core topology limit when it's beneficial to parallelize algorithms, and so on. These trade-offs don't even require oddball futuristic CPUs, and already vary significantly even within existing CPU families.

There are some languages that focus on "what" and magically optimize "how" (ISPC, Halide, and good'ol SQL), but for better or worse, Rust has chosen the "portable assembly" angle and micromanagement of everything. The upside is that you have very few surprises and "performance cliffs", and rest assured that if something is slow, you have enough control to fix it (as opposed to e.g. JIT-based language).