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> the code density that RISC-V allows is disappointing considering the designers had an opportunity to start from scratch. IIRC the code density beats ARMv8 an
by messe 6y ago
> the code density that RISC-V allows is disappointing considering the designers had an opportunity to start from scratch.
IIRC the code density beats ARMv8 and x86_64 in most situations.
- userbinator 6y agoThey may have beaten the average compiler in x86 code density, but compilers aren't normally optimising for size and, as someone who has been writing x86 Asm for a long time, I can safely say that compiler output in general, even at max size opts, is far from the theoretical limit for x86 --- there is plenty of room for improvement there. On the other hand, RISCs are far more constrained in size optimisation. For an example of what I mean by x86 having a very high limit on code density, see https://news.ycombinator.com/item?id=15720923 https://news.ycombinator.com/item?id=15720923
- messe 6y agoBut that is part of the issue with x86. Steadily, the dense instructions of x86 have been neglected and become less performant. A perfect example of this is "rep movsb": up until I think a decade ago, Intel actually recommended against its use in their optimization manuals.