* [gentoo-dev] How to structure our RISC-V support
@ 2021-05-06 20:01 99% Andreas K. Huettel
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From: Andreas K. Huettel @ 2021-05-06 20:01 UTC (permalink / raw
To: gentoo-dev; +Cc: riscv
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Howdy.
I'm sending this not only to the team members on the alias, but also
to the whole dev list for discussion.
So far I've been trying to support in Gentoo the full risc-v multilib
directory structure and the ABI sets supported by glibc. According to
specs this means for riscv64
-mabi=rv64gc -march=lp64d
libdir = lib64/lp64d
("hardfloat")
-mabi=rv64imac -march=lp64
libdir = lib64/lp64
("softfloat")
and theoretically similar for riscv32 (which just landed in glibc and
is still broken in qemu-user).
However, this leads to several levels of pain (and I definitely dont
have time to deal with it myself):
a) In many places the two-level libdir (e.g., /usr/lib64/lp64d) leads
to difficulties in build systems. Right now Qt5 and CMake are still
somewhat broken (in *Gentoo*).
b) Rust only supports rv64gc/lp64d. (Which is arguably what you should
have for decent Linux support.)
I'm pretty sure these are not the only things, but they are somewhat
symptomatic.
So, I would like to bring two proposals up for discussion.
1) We stop caring about anything except rv64gc/lp64d.
People can still bootstrap other stuff with crossdev etc, but the
Gentoo tree and the riscv keyword reflect that things work with above
-mabi and -march settings.
2) We drop the multilib paths and use "normal" lib64, with additional
"safety symlinks" (/usr)/lib64/lp64d -> .
This is what SuSE and (I think) Fedora already does. The symlink
should be there since "lib64" is NOT an official fallback coded into
gcc/glibc/binutils; the only fallback present is "lib" ...
Opinions?
Cheers,
Andreas
--
Andreas K. Hüttel
dilfridge@gentoo.org
Gentoo Linux developer
(council, toolchain, base-system, perl, libreoffice)
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