[Libre-soc-isa] [Bug 1214] Simple-V ISA Expansion -- Evaluate adding Simple-V to x86

[bugzilla-daemon at libre-soc.org]

https://bugs.libre-soc.org/show_bug.cgi?id=1214

--- Comment #2 from Luke Kenneth Casson Leighton <lkcl at lkcl.net> ---
(In reply to Jacob Lifshay from comment #1)

> Well, I care, and NLNet probably cares, since we don't want to do work on
> something that basically no one will use, since the ISA is too old.

reminder (four times in this bugreport already): the scope is evaluate not
implement.

> We could use Intel XED:
> https://github.com/intelxed/xed
> it's an open source (Apache 2.0) x86/x86-64 instruction
> decoder/encoder...that looks like it should be somewhat doable to add some
> of SV to, 

x86 is going to be a pain in the ass because of the hardcoded regster names.
eax/ebx as a target. sigh. vectorising that is part of the evluation, but
*please do not get distracted* from the deadlines by focussing on this
even before the grant has been evluated, we get *no money*

> and then implement a minimal simulator on top of that that runs
> just enough for a strcpy or something of similar complexity, that would
> probably be a few dozen instructions at most. this is enough for a
> proof-of-concept on top of an ISA (x86-64) that everyone does use.

scope: evaluate not implement. although xed looks real handy to do the
conversion to libopid/insndb.


>  also,
> Intel XED has support for APX which supports 32 GPRs.
> 
> > implementation exists. https://opencores.org/projects/ao486
> > *assessment* not full-blown implementation.
> 
> according to the readme it implements cpuid and all 486SX instructions, so
> basically everything but x87. so it is pretty full-blown,

exactly. and what is really nice is, if you dig a little deeper, it
is a pseudocode-to-verilog compiler!! so the pseudocode is *already there*
meaning that getting it into ISACaller is real simple.

[... why do you think i picked it? :) ]

> just not very
> useful for our purposes imo since basically no one will want to target a
> i486, it doesn't even have popcount or 64-bit atomics!

that's ok, we can look at adding them (after finding the ones that
are unpatented). idea here is to evaluate not implement although i
do love the thought.  i particularly want to see what the compression
ratio is (bang per buck).

> if we still didn't care if anyone will use it, why not try to add SimpleV to
> the VAX ISA, it has a gcc target and an attempted linux port?

ooo niiice! perfect! let's add it to the list...

-- 
You are receiving this mail because:
You are on the CC list for the bug.