riscv-v-spec
riscv-bitmanip
riscv-v-spec | riscv-bitmanip | |
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43 | 12 | |
858 | 206 | |
- | 2.9% | |
6.0 | 0.0 | |
about 2 months ago | about 2 months ago | |
Assembly | Makefile | |
Creative Commons Attribution 4.0 | Creative Commons Attribution 4.0 |
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riscv-v-spec
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Scaleway launches RISC-V servers
Here are some resources I can recommend:
RVV spec (also look at the examples in the repo): https://github.com/riscv/riscv-v-spec/blob/master/v-spec.ado...
RVV intrinsics viewer: https://dzaima.github.io/intrinsics-viewer
Tutorial: RISC-V Vector Extension Demystified (3 hour video going over every instruction): https://youtu.be/oTaOd8qr53U
RISC-V Vector extension in a nutshell: https://fprox.substack.com/p/risc-v-vector-extension-in-a-nu...
If you want to see a more complex example/real world application, then you might also be ibterested ib my article about vectorizing unicode conversions: https://camel-cdr.github.io/rvv-bench-results/articles/vecto...
In terms of development I'd recommend using qemu and a cross compiler, or if you want hardware try to get the kendryte k230 (currently the only sbc with rvv 1.0 support) or wait a bit for better hardware (BPI-F3 and sg2380 should release this year).
- Cray-1 performance vs. modern CPUs
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x86 vs ARM; Vector and Matrix Extensions; How do they compare?
And this isn't just some theoretical or something unlikely to happen - the official spec already contains such a bug. If the writers of the spec can't get things right, even with the small amount of code in the spec, I don't have high hopes that less informed programmers will. RVV being absurdly complicated (IMO, compared to SVE2 and AVX10) doesn't help its cause here.
- riscv64 is now an official Debian architecture (rebootstrap in progress)
- Vector vs SIMD
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LLVM's libc Gets Much Faster memcpy For RISC-V
Will the reference one actually be the most optimal one on future hardware?
- Is there any good place to find a copy-paste-able quick reference on RISC-V extensions? Particularly for the vector extension
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Building a toolchain suitable for compiling V extension code
I'll do a deep dive into the https://gms.tf/riscv-vector.html#getting-started tutorial, and probably pop the proverbial stack and just study RVV 0.7.1 on its own (using https://github.com/riscv/riscv-v-spec/releases/tag/0.7.1).
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A weird idea for using RV32E on a RV32I core - multithreaded microcontrollers?
I see your point. You can file a request for it at https://github.com/riscv/riscv-v-spec/issues if you want to pitch it to the relevant ISA bodies. The bar for implementing it pretty high.
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Examining the Top Five Fallacies About RISC-V
It's not "unusual"; using data registers for mask is a valid tradeoff especially for low-end implementations, whereas higher-end architectures can easily use shadow registers. Discussed in depth at https://github.com/riscv/riscv-v-spec/issues/811
riscv-bitmanip
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You Won’t Believe This One Weird CPU Instruction (2019)
The bit manipulation [0] extension has been ratified for a while now and is part of the RVA22 application extension profile [1].
You can already buy SOCs that support it, e.g. vision five 2 and star64.
Interestingly the risc-v vector has it's own popcount instructions for vector registers/register masks. This is needed, because the scalable architecture doesn't guarantee that a vector mask can fit into a 64 bit register, so vector masks are stored in a single LMUL=1 register. This works really well, because with LMUL=8 and SEW=8 you get 100% utilization of the single LMUL=1 vector register.
Another interesting thing is that the vector crypto extension will likely introduce a element wise popcount instruction.
[0] https://github.com/riscv/riscv-bitmanip/releases/download/1....
[1] https://github.com/riscv/riscv-profiles/blob/main/profiles.a...
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Is Bit Manipulation extension ratified?
According to latest version of spec on GitHub (https://github.com/riscv/riscv-bitmanip) Bit-manip is in frozen state. Is this ratified and not updated in the sepc document or is it actually frozen?
- Hand optimised RISC-V assembly language clz
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Testing for presence of _Zba and _Zbb
I guess 0x20a52533 is a specific _zba instruction? Which one? I searched for "001000" (the left 6 bits of 0x20) in https://github.com/riscv/riscv-bitmanip/releases/download/1.0.0/bitmanip-1.0.0-38-g865e7a7.pdf , but couldn't find a match? Might be PEBKAC.
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A Neat XOR Trick
RISC-V does have a proposed extension Zbb that includes the cpop and cpopw instructions. It doesn't seem to have much recent activity, though.
https://github.com/riscv/riscv-bitmanip/blob/main/bitmanip/i...
- Why aren't there any RISC-V cores with desktop level power?
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Cores with V-extension and Linux support
Enabling B use in dynamically linked libc code will improve every application, especially for example use of orc.b in the C string functions, which is what I invented it for https://github.com/riscv/riscv-bitmanip/issues/41 (using V is even better, but that's optional in RVA22)
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Bitmanip: Missing bit field extract / insert instructions?
[2] https://github.com/riscv/riscv-bitmanip/releases/tag/1.0.0
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gmp: "Risc V is a terrible architecture"
There was a pick instruction, literally named cmov, in an older version of the B (bitmanip) extension (all the good stuff is in extensions). But it seems like it got canned or something, it's not in it anymore (various other interesting instructions were also lost). Silly if you ask me, but I haven't kept up with any of the debate, maybe there's a decent reason..
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RISC-V Int. Ratifies 15 New Specs, Opening Up New RISC-V Design Possibilities
Yoe maybe interested in the just ratified "RISC-V Bit-Manipulation ISA-extensions" https://github.com/riscv/riscv-bitmanip/releases/download/1....
What are some alternatives?
riscv-p-spec - RISC-V Packed SIMD Extension
riscv-sbi-doc - Documentation for the RISC-V Supervisor Binary Interface
highway - Performance-portable, length-agnostic SIMD with runtime dispatch
riscv-isa-manual - RISC-V Instruction Set Manual
highway - Highway - A Modern Javascript Transitions Manager
riscv-crypto - RISC-V cryptography extensions standardisation work.
vroom - VRoom! RISC-V CPU
nytm-spelling-bee - Generate anagram puzzles like Frank Longo's "Spelling Bee" as in New York Times Magazine
learn-fpga - Learning FPGA, yosys, nextpnr, and RISC-V
cpu_features - A cross platform C99 library to get cpu features at runtime.
meetings - WebAssembly meetings (VC or in-person), agendas, and notes
riscv-platform-specs - RISC-V Profiles and Platform Specification