Gentoo Archives: gentoo-mips

From: Joshua Kinard <kumba@g.o>
To: "Michał Górny" <mgorny@g.o>, gentoo-dev@l.g.o
Cc: mips@g.o, gentoo-mips@l.g.o
Subject: [gentoo-mips] Re: [gentoo-dev] Monthly mips@ project status for April 2018
Date: Tue, 03 Apr 2018 05:24:25
In Reply to: [gentoo-mips] Re: [gentoo-dev] Monthly mips@ project status for April 2018 by "Michał Górny"
1 On 4/2/2018 4:32 PM, Michał Górny wrote:
2 > W dniu pon, 02.04.2018 o godzinie 13∶27 -0400, użytkownik Joshua Kinard
3 > napisał:
4 >> On 4/2/2018 5:41 AM, Michał Górny wrote:
5 >>> W dniu nie, 01.04.2018 o godzinie 20∶40 -0700, użytkownik Matt Turner
6 >>> napisał:
7 >>>
8 >>>> My plan is to add stable 17.0 mips profiles when the keywording is
9 >>>> sorted out and kill two birds with one stone.
10 >>>
11 >>> Does it involve fixing the CHOST inconsistency so that we can finally
12 >>> get LLVM keyworded?
13 >>
14 >> Bug #515694, right? Based on a very quick re-read, there are two
15 >> issues/blockers here:
16 >>
17 >> 1) Current Gentoo/MIPS support was originally based on gcc, thus, we've used
18 >> CHOST tuples that are recognized by gcc.
19 >
20 > As far as I'm aware GCC doesn't really care about which triplet is used.
21 > It's all controlled by --with-abi= option (I may have mistyped its
22 > name).
24 gcc might not, but odds are incredibly likely other software will. I want to
25 say memory reminds me that glibc may be a culprit here, and may explain the
26 reason why someone redesigned the triplets/tuples in the first place. E.g., I
27 *think* (but can't corroborate) that the "mips64-unknown-linux-gnuabin32" tuple
28 derived from glibc wanting to determine n32 support from the CHOST. Again,
29 though, there are no known equivalents of this for uclibc-ng or musl targets
30 that I know of.
33 >> 2) clang lacks a CHOST tuple that defaults to n32. n32 is the "ideal" ABI for
34 >> a 64-bit platform that doesn't need full 64bit (n64) binary support.
35 >>
36 >> As far as I can tell, we need to fix #2 before we can do anything about #1.
37 >> Once clang has a discrete CHOST tuple for n32, that'll put it on parity with
38 >> gcc, which itself appears to have a batch of more specific tuples to select
39 >> different ABIs. You might want to just push upstream any patches you have that
40 >> adds this support first.
41 >
42 > It's chicken-egg problem. Before I can submit a patch upstream, I need
43 > someone with MIPS hardware and a proper profile (using disjoint,
44 > consistent triplets) to test it. Not to mention Gentoo needs to decide
45 > on the triplet in the first place.
47 Is there an option to cross-compile clang/llvm using a CHOST added by your
48 patch? That should at least validate that the CHOST logic works out. Any one
49 of us could then test out a statically-linked binary generated from such a
50 toolchain, assuming the target output matches one of our machines.
52 As far as Gentoo "deciding", I have to argue that it's not an "our fault" thing
53 or such. Back when the port was started in ~2003, there was no such thing as
54 clang/llvm, so we used what CHOSTs gcc was happy with. Life continued on from
55 there, with a few hiccups along the way.
57 I know of no authority that sets/decides what CHOSTs are valid and what aren't.
58 That'd probably be a nice thing to have, TBH, as my irritation with FreeBSD's
59 versioned CHOSTs makes updating a Gentoo/FreeBSD userland mildly annoying.
60 That said, I don't have much of a problem adopting the Debian versions[1]. We
61 would just need a way to migrate existing installs, preferably w/o having to
62 recompile everything...
64 1.
66 --
67 Joshua Kinard
68 Gentoo/MIPS
69 kumba@g.o
70 6144R/F5C6C943 2015-04-27
71 177C 1972 1FB8 F254 BAD0 3E72 5C63 F4E3 F5C6 C943
73 "The past tempts us, the present confuses us, the future frightens us. And our
74 lives slip away, moment by moment, lost in that vast, terrible in-between."
76 --Emperor Turhan, Centauri Republic