3 ms·
>code density RISC-V excels in code density. 64-bit RISC-V is the most dense 64bit ISA by a large margin and has been for a long time. 32-bit RISC-V is the m
by snvzz 4y ago
>code density
RISC-V excels in code density.
64-bit RISC-V is the most dense 64bit ISA by a large margin and has been for a long time.
32-bit RISC-V is the most dense 32bit ISA as of the recent B and Zc work; it used to be Thumb2 was ahead.
All of this is without compromising "purity" or needlessly complicating decode; there already is a 8-wide decode implementation (Ascalon, by Jim Keller's team), matching Apple M1/M2 decode width.
- less_less 4y agoSure, that's fair. And I'm not saying RISC-V made the wrong choice. Just that lack of "impure" instructions like LDMIA does reduce code density, and can't be fixed through fusion, even if you can get ahead of Thumb2 with improvements elsewhere. (Thumb2 is the most apt comparison here I think, since the instructions I mentioned are Thumb2 instructions.)