Mobile is the new PC and AArch64 is the new x64

[Joakim]

On Wednesday, 12 September 2018 at 22:41:31 UTC, Iain Buclaw 
wrote:
> On 12 September 2018 at 10:09, Joakim via Digitalmars-d 
> <digitalmars-d at puremagic.com> wrote:
>> I think their model of having an open ISA with proprietary 
>> extensions will inevitably win out for hardware, just as a 
>> similar model has basically won already for software, but that 
>> doesn't mean that RISC-V will be the one to do it. Someone 
>> else might execute that model better.
>>
>
> POWER9 has been making some headway, for instance finally they 
> have a sensible real type (IEEE Quadruple).  Though the 
> developers working on glibc support seem to be making a 
> shambles of it, where they want to support both new and old 
> long double types at the same time at run-time!  It seems that 
> no one thought about Fortran, Ada, or D when it came to long 
> double support in the C runtime library *sigh*.
>
> For us, I think we can choose to ignore the old IBM 128-bit 
> float, and so remove any supporting code from our library, 
> focusing instead only on completing IEEE 128-bit float support 
> (LDC, upstream your local patches before i start naming and 
> shaming you).

All the pulls linked from that AArch64 tracker issue above were 
submitted upstream first before merging into the ldc repo. Only 
one patch that I know of hasn't been merged upstream yet: my 
commit to add IEEE Quadruple support to core.internal.convert, 
only because I want to add another Android commit to that pull 
soon, but the patch is available in the open druntime pulls.

If you know of some other patches that need to be upstreamed, let 
us know, AFAIK they were all upstreamed first.

> ARM seems to be taking RISC-V seriously at least (this site was 
> taken down after a couple days if I understand right: 
> http://archive.fo/SkiH0).  There is currently a lot of 
> investment going into ARM64 in the server space right now, but 
> signals I'm getting from people working on those projects are 
> that it just doesn't hold water.  With one comparison being a 
> high end ARM64 server is no better than a cheap laptop bought 5 
> years ago.

As Kagamin says, it depends on how many cores you're using and 
what benchmark you run, but most of the time, that's not true at 
all:

https://blog.cloudflare.com/arm-takes-wing/

And ARM does it with much less electric power used, as shown in 
that last graph, which you have to take into account when looking 
at the total costs. The ARM blog post I linked earlier in this 
thread shows they've gone ahead with using ARM too.

> RISC-V got accepted into gcc-7, and runtime made it into glibc 
> 2.27, there's certainly a lot effort being pushed for it.  They 
> have excellent simulator support on qemu, porting druntime only 
> took two days.  Patches for RISCV64 will come soon, probably 
> with some de-duplication of large blocks.

Great, but it's still in very nascent stages, with linux only 
running on it this year. I thought about using Qemu but figured 
the slowness and possible hardware compatibility issues weren't 
worth it.

I hope some open arch like these takes off sometime soon, as I 
don't like an ARM monopoly much better than the previous Intel 
one, but it's going to take awhile for POWER/RISC-V to get 
anywhere close.