Gentoo Archives: gentoo-dev

From: Luca Barbato <lu_zero@g.o>
To: gentoo-dev@l.g.o
Subject: Re: [gentoo-dev] New project: LLVM
Date: Fri, 19 Aug 2016 17:38:17
In Reply to: Re: [gentoo-dev] New project: LLVM by "C Bergström"
1 On 19/08/16 17:15, 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.
16 I see, it is getting quite close =)
18 > As a philosophy - "we" aren't really trying to be the best generic
19 > compiler in the world. We aim more on optimizing as much for known
20 > targets. So if by system you mean, a compiler that would produce an
21 > "OS" which only runs on a single class of hardware, then yeah it could
22 > work at some point in the future. Specifically, on x86 we default on
23 > host CPU optimizations. So on newer Intel hardware it's easy to get a
24 > binary that won't run on AMD or older 64bit Intel.
25 >
26 > More recently on ARMv8 - we turn on processor specific tuning. So
27 > while it may "run", the difference between APM's mustang and Cavium
28 > ThunderX is pretty big and running binaries intended for A and ran on
29 > B would certainly take a hit.. (this is just the tip of the iceberg)
31 This is not a problem for Gentoo, actually sounds a good match for one
32 of our many use-cases =)
34 > For HPC codes or anything where you get loops or computationally
35 > complex - the gloves are off and I could see big differences... (again
36 > being general and maybe a bit dramatic for fun)
38 I started to do some decoding benchmark across compiler version some
39 time ago, I should try to put in the mix your compiler as well and
40 eventually blog about it =)
42 lu