How is Ultrassembler so fast?
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How is Ultrassembler so fast?
1–10 of 53 posts
Re: How is Ultrassembler so fast?
#2Neat, but it's not like assembly is really a bottleneck in any but the most extreme cases. LLVM and GAS are already very fast.
I feel like this might mostly be useful as a reference, because currently RISC-V assembly's specification is mostly "what do GCC/Clang do?"
Re: How is Ultrassembler so fast?
#3Hi everyone, I'm the author of this article.
Feel free to ask me any questions to break the radio silence!
Re: How is Ultrassembler so fast?
#4Hi everyone, I'm the author of this article. Feel free to ask me any questions to break the radio silence!
Overall, this is a fantastic dive into some of RISC-V's architecture and how to use it. But I do have some comments:
> However, in Chata's case, it needs to access a RISC-V assembler from within its C++ code. The alternative is to use some ugly C function like system() to run external software as if it were a human or script running a command in a terminal.
Have you tried LLVM's C++ API [0]?
To be fair, I do think there's merit in writing your own assembler with your own API. But you don't necessarily have to.
I'm not likely to go back to assembly unless my employer needs that extra level of optimization. But if/when I do, and the target platform is RISC-V, then I'll definitely consider Ultraseembler.
> It's not clear when exactly exceptions are slow. I had to do some research here.
There are plenty of cppcon presentations [1] about exceptions, performance, caveats, blah blah. There's also other C++ conferences that have similar presentations (or even, almost identical presentations because the presenters go to multiple conferences), though I don't have a link handy because I pretty much only attend cppcon.
[0]: https://stackoverflow.com/questions/10675661/what-exactly-is...
[1]: https://www.youtube.com/results?search_query=cppcon+exceptio...
Re: How is Ultrassembler so fast?
#5Hi everyone, I'm the author of this article. Feel free to ask me any questions to break the radio silence!
Nice work and good writeup. I think most of that is very sound practice.
The codegen switch with the offsets is in everything, first time I saw it was in the Rhino JS bytecode compiler in maybe 2006, written it a dozen times since. Still clever you worked it out from first principles.
There are some modern C++ libraries that do frightening things with SIMD that might give your bytestring stuff a lift on modern stupid-wide high mispredict penalty stuff. Anything by lemire, stringzilla, take a look at zpp_bits for inspiration about theoretical minimum data structure pack/unpack.
But I think you got damn close to what can be done, niiicccee work.
Re: How is Ultrassembler so fast?
#6Neat, but it's not like assembly is really a bottleneck in any but the most extreme cases. LLVM and GAS are already very fast. I feel like this might mostly be useful as a reference, because currently RISC-V assembly's specification is mostly "what do GCC/Clang do?"
ptxas comes to mind.
Re: How is Ultrassembler so fast?
#7Hi everyone, I'm the author of this article. Feel free to ask me any questions to break the radio silence!
Overall, this is a fantastic dive into some of RISC-V's architecture and how to use it. But I do have some comments: > However, in Chata's case, it needs to access a RISC-V assembler from within its C++ code. The alternative is to use some ugly C function like system() to run external software as if it were a human or script running a command in a terminal. Have you tried LLVM's C++ API [0]? To be fair, I do think th…
> LLVM's C++ API
I think I read something about this but couldn't figure out how to use it because the documentation is horrible. So, I found it easier to implement my own, and as it turns out, there are a few HORRIBLE bugs in the LLVM assembler (from cross reference testing) probably because nobody is using the C++ API.
> There are plenty of cppcon presentations [1] about exceptions, performance, caveats, blah blah.
I don't have enough time to watch these kinds of presentations.
Re: How is Ultrassembler so fast?
#8Neat, but it's not like assembly is really a bottleneck in any but the most extreme cases. LLVM and GAS are already very fast. I feel like this might mostly be useful as a reference, because currently RISC-V assembly's specification is mostly "what do GCC/Clang do?"
ptxas comes to mind.
ptxas is a bit of a misnomer - it actually wraps the entire NVIDIA driver backend compiler
PTX isn’t the assembly language, it is a virtual ISA, so you need a full backend compiler with 10s to 100s of passes to get to machine code
Re: How is Ultrassembler so fast?
#9Earlier quoted context omitted.
ptxas comes to mind.
ptxas is a bit of a misnomer - it actually wraps the entire NVIDIA driver backend compiler PTX isn’t the assembly language, it is a virtual ISA, so you need a full backend compiler with 10s to 100s of passes to get to machine code
I appreciate that hitting sm_70 through sm_120 in one call isn't the same as hitting RISC-V in one call, but I do a lot of builds just for sm_120 which is closer to a fair comparison.
It's imperfect, but I take any excuse to point out how bad monopolies are for customers. All you have to do is build the driver to see that "low priority" is a pretty broad term on the allegedly elite trillion dollar toolchain.
I'm not saying CUDA is unimpressive, its a very, very, very hard problem. But if they were in an uncorrupted market ptxas would be fast instead of devastating znver5 workstations with 6400MT DDR5.
Re: How is Ultrassembler so fast?
#10Hi everyone, I'm the author of this article. Feel free to ask me any questions to break the radio silence!
What's the difference between a Programming Furu and a Programming Guru? Is there a joke I'm missing?