5 ms·
> Manifestly, the B extension isn't in any of the chips being produced now The RISC-V chips produced today are not made for performance or be competitive, they
by avianes 6y ago
> Manifestly, the B extension isn't in any of the chips being produced now
The RISC-V chips produced today are not made for performance or be competitive, they are proof of concepts, toys and prototypes.
The current state of the RISC-V spec is not competitive with either ARM or x86. Therefore why use this as a comparison point?
> It's a proposed extension, not finalized.
Like many other extensions such as the Packed SIMD one, the Vector one and Hypervisor one.
These 3 are probably even more important than bit manipulation for performance and are not finalized either.
The RISC-V ISA is still under construction.
> It's a large extension, so (like other large extensions) it won't be implemented on the smaller chips that will also lack.
Did you know that it's stipulated in the RISC-V spec that instructions not present in the hardware can be emulated in software?
This makes it possible, in a small chip, to handle an extension as large as B without the need to implement all the instructions.
> For all we know, it may never become a standard extension. Somebody said they were trying to get the POPCOUNT instruction removed even from the extension, or made an optional part of it.
> I don't know why I would need sources.
You need a source because you make surprising assertions.
- ncmncm 6y agoI see that you do not understand that an emulated popcount instruction would be worse than useless. If you found anything I said surprising, it is only by not having thought things through. You would better learn to do that.
- avianes 6y ago> I see that you do not understand that an emulated popcount instruction would be worse than useless. Where do you read that I'm talking about emulating popcount in software? I mean exactly the opposite. If you need to support all B, or a subgroup of B, you can choose to put popcount in hardware and emulate the other instructions. > If you found anything I said surprising This is neither a source nor an argument.
- ncmncm 6y agoYet, it remains a fact. If you know of any chips in production that implement the Bitmanip extension, you have been free all along to mention them.
- jlokier 6y ago> Where do you read that I'm talking about emulating popcount in software? I mean exactly the opposite. Because you wrote this: > Did you know that it's stipulated in the RISC-V spec that instructions not present in the hardware can be emulated in software? apparently in reference to the B extension which includes popcount.