Gentoo Archives: gentoo-dev

From: james <garftd@×××××××.net>
To: gentoo-dev@l.g.o
Subject: Re: [gentoo-dev] New project: LLVM
Date: Fri, 19 Aug 2016 18:02:59
In Reply to: Re: [gentoo-dev] New project: LLVM by "C Bergström"
1 On 08/19/2016 11:15 AM, C Bergström wrote:
2 > On Fri, Aug 19, 2016 at 11:01 PM, Luca Barbato <lu_zero@g.o> wrote:
3 >> BTW is pathscale ready to be used as system compiler as well?
4 >
5 > I wish, but no. We have known issues when building grub2, glibc and
6 > the Linux kernel at the very least. Someone* did report a long time
7 > ago that with their unofficial port, were able to build/boot the
8 > NetBSD kernel.
9 > (*A community dev we trusted with our sources and was helping us with
10 > portability across platforms)
11 >
12 > The stuff with grub2 may potentially be fixed in the "near" future...
13 > the others are more tricky. In general if clang can do it, we have a
14 > strong chance as well.
15 >
16 > As a philosophy - "we" aren't really trying to be the best generic
17 > compiler in the world. We aim more on optimizing as much for known
18 > targets. So if by system you mean, a compiler that would produce an
19 > "OS" which only runs on a single class of hardware, then yeah it could
20 > work at some point in the future. Specifically, on x86 we default on
21 > host CPU optimizations. So on newer Intel hardware it's easy to get a
22 > binary that won't run on AMD or older 64bit Intel.
23 >
24 > More recently on ARMv8 - we turn on processor specific tuning. So
25 > while it may "run", the difference between APM's mustang and Cavium
26 > ThunderX is pretty big and running binaries intended for A and ran on
27 > B would certainly take a hit.. (this is just the tip of the iceberg)
28 >
29 > For general scalar OS code it isn't likely to matter... the real
30 > impact being like 1-10% difference (being very general.. it could be
31 > less or more in the real world..)
32 >
33 > For HPC codes or anything where you get loops or computationally
34 > complex - the gloves are off and I could see big differences... (again
35 > being general and maybe a bit dramatic for fun)
38 OK (actually fantastic!). Looking at the pathscale site pages and
39 github, perhaps a cheap arm embedded board where llvm is the centerpiece
40 of compiling a minimal system to entice gentoo-llvm testers, would be
41 possible in the near future?. I have a 96boards, HiKey arm64v8 that I
42 could dedicate to gentoo+armv8-llvm testing, if that'd help. [1]
44 Perhaps a baseline bootstrap iso (or such) version targeted at
45 llvm-centric testers on x86-64 or armv8 ? Skip grub2 and use grub-legacy
46 or lilo or (?), since there seems to be issues with llvm-grub2.
49 [1]
52 No matter how you slice it, from someone who is focused on building
53 minimized and embedded (bare metal) systems that are customized and
54 coalesced into a heterogeneous gentoo cluster for HPC, this is wonderful
55 news. Finally a vendor in the cluster space, with some vision and
56 common-sense, imho. Heterogeneous and open HPC is where is at, imho. If
57 there is a forum where the community and pathscale folks discuss issues,
58 point that out as I could not find one for deeper reading....
61 hth,
62 James


Subject Author
Re: [gentoo-dev] New project: LLVM "C Bergström" <cbergstrom@×××××××××.com>