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0 pointspurplesyringa14d ago0 comments

I suspect that LLVM is optimized for compiling with `-ftrapv`, perhaps for cheap sanitizing or maybe just due to design decisions like using unsigned integers everywhere (please correct me if I'm wrong). I'm personally interested in how RISC-V behaves on computational tasks where computing carry is a known bottleneck, like long addition. Maybe looking at libgmp could be interesting, though I suspect absolute numbers will not be meaningful, and there's no baseline to compare them to.

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camel-cdr12d ago

LLVM mostly uses size_t like most C/C++ programs, which either use size_t or int for everything, both of which are handled well by RISC-V.

> Maybe looking at libgmp could be interesting, though I suspect absolute numbers will not be meaningful, and there's no baseline to compare them to.

Realistically, nobody cares about BigInt addition performance, considering there is no GMP implementarion using SIMD, or even any using dependency breaking to get beyond 64-bit per cycle.

I whipped up a quick AVX-512 implementation that was 2x faster than libgmp on Zen4 (which has 256-bit SIMD ALUs). On RISC-V you'd just use RVV to do BigInt stuff.

purplesyringaOP9d ago

"nobody cares about BigInt addition performance" is an odd claim to make when half of the world's cryptography is based on ECC.

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