4 ms·
x86-64 somehow manages to be less compact than ARM while still being variable-length. Thumb is still much saner than x86/x86-64.
by arielb1 11y ago
x86-64 somehow manages to be less compact than ARM while still being variable-length. Thumb is still much saner than x86/x86-64.
- Narishma 11y agoYou mean Thumb-2?
- arielb1 11y agoNo, even vanilla ARM. x86-64 instructions are 3-5 bytes in size and compilers don't use complex instructions effectively.
- pcwalton 11y agoThis is correct. Thumb-2 is the only actual compact instruction set in wide use. x86-64 doesn't even come close to being as efficient; between ARM and x86-64, it's a wash. It's certainly possible to design a CISC ISA (or maybe even a RISC one) that's optimized for compactness. x86 isn't that, though. Maybe it was in the 16-bit era, in a hypothetical future where BCD instructions were used a lot.