riscv-v-spec
riscv-isa-manual
riscv-v-spec | riscv-isa-manual | |
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43 | 41 | |
858 | 3,293 | |
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6.0 | 9.7 | |
about 2 months ago | 2 days ago | |
Assembly | TeX | |
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-isa-manual
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The Improved RISC-V Specification (latest WIP draft)
https://github.com/riscv/riscv-isa-manual/releases
Regarding the recent "How to improve the RISC-V specification" post [0], I just wanted to point out, that the latest draft manual is already a great improvement. (see link above)
It includes a lot of the newly ratified extensions: bitmanip,zicond,vector,vector crypto, ...
And there are a bunch of included SAIL definitions for bitmanip and zicond, but other instructions are still missing the SAIL code. Most notably, the SAIL definitions from the RV32I/RV64I base isa are also missing.
I asked for the further SAIL integration plans here: https://github.com/riscv/riscv-isa-manual/issues/1369
Here is an example SAIL snippet from cpopw:
let bitcount = 0;
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How to improve the RISC-V specification
I encourage you to look at the newest isa manual draft on github: https://github.com/riscv/riscv-isa-manual/releases
It includes the more recently extensions, and e.g. the bitmanip instructions all have associated pseudo code.
Here is e.g. the code for cpopw:
let bitcount = 0;
- Need help with designing a basic RISC V processor?
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The legend of “x86 CPUs decode instructions into RISC form internally”
I tried searching the spec [1] for "overflow" and here is what it says at page 17:
> We did not include special instruction-set support for overflow checks on integer arithmetic operations in the base instruction set, as many overflow checks can be cheaply implemented using RISC-V branches.
> For general signed addition, three additional instructions after the addition are required
Is this "cheap", replacing 1 instruction with four? According to some old mainframe era research (cannot find link now), addition is the most often used instruction and they suggest that we should replace each one with four?
Their "rationale" is not rational at all. It doesn't make sense.
Overflow check should be free (no additional instructions required), otherwise we will see the same story we have seen for last 50 years: compiler writers do not want to implement checks because they are expensive; language designers do not want to use proper arithmetic because it is expensive. As a result, there will be errors and vulnerabilities. A vicious circle.
[1] https://github.com/riscv/riscv-isa-manual/releases/download/...
- 64-bit Arm ∩ 64-bit RISC V
- Beginner question: F extension
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Riscv Ghidra Instruction Manual
Why not use the actual release PDF instead from their github? https://github.com/riscv/riscv-isa-manual
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How would I go about designing an 8-bit RISC-V CPU? Is it possible?
https://github.com/riscv/riscv-isa-manual/releases/download/Priv-v1.12/riscv-privileged-20211203.pdf Part 2
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Have to convert a C language code into RISC-V MIPS
If you don't want to cheat then read the RISC-V ISA manual: https://github.com/riscv/riscv-isa-manual/releases/download/Ratified-IMAFDQC/riscv-spec-20191213.pdf
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How does a computer understand machine language?
Yeah you are on the right track. Processors are designed on top of an Instruction Set Architecture (ISA). For an example you can look on top of the RISC-V specifications:https://github.com/riscv/riscv-isa-manual/releases/download/Ratified-IMAFDQC/riscv-spec-20191213.pdf (possible PDF download)
What are some alternatives?
riscv-p-spec - RISC-V Packed SIMD Extension
riscv-elf-psabi-doc - A RISC-V ELF psABI Document
highway - Performance-portable, length-agnostic SIMD with runtime dispatch
riscv-emulator-docker-image
highway - Highway - A Modern Javascript Transitions Manager
amaranth - A modern hardware definition language and toolchain based on Python
riscv-bitmanip - Working draft of the proposed RISC-V Bitmanipulation extension
vroom - VRoom! RISC-V CPU
open-source-cs - Video discussing this curriculum:
learn-fpga - Learning FPGA, yosys, nextpnr, and RISC-V
ibex - Ibex is a small 32 bit RISC-V CPU core, previously known as zero-riscy.