MaskRay added a comment.
> If we could get this patch merged, we could build and link the whole LLVM
> with lld on NetBSD and it would increase the productivity of the bot (better
> build times). Right now we need to maintain hacks to link at most with 2/3
> cores, while 5/6 ones are idling doing nothing due to enormous RAM
> consumption of GNU ld.
I will be very happy to see the productivity of NetBSD build bot gets improved.
My comments below are about the approach you choose in this patch.
> FreeBSD/OpenBSD ship with mutations of the behavior of ELF/GNU/Linux in
> certain nits, we do the same with our driver.
The FreeBSD specific code is just the following 4 lines in ELF/Driver.cpp:
if (s.endswith("_fbsd")) {
s = s.drop_back(5);
osabi = ELFOSABI_FREEBSD;
}
`PT_OPENBSD_*` extensions are related to
https://bugs.llvm.org//show_bug.cgi?id=31288 , which predated my involvement
into lld.
It was not a good example of issue reports. Neither the bug nor the link it
referenced provided rationale why such extensions were needed. CC @bradsmith
here. I will also ask in their IRC channel and/or send an email to their
mailing list.
The NetBSD extension does much more than FreeBSD (4 lines of code) and OpenBSD
(7 lines of code modulo comments).
On the contrary, the NetBSD patch introduces another toplevel driver nb.lld,
and includes ~200 lines of change.
Moreoever, I anticipate you will post another patch with probably than more
than 200 lines of code that does
https://blog.netbsd.org/tnf/entry/the_first_report_on_lld#handling-of-indirect-shared-library-dependencies
, which many people (probably even the GNU maintainers) feel no longer
appropriate nowadays.
> the linker MUST work in the standalone mode
By standalone mode, do you mean $(LD) or ld? I think for most such use cases,
we should probably change them to do `gcc/clang -nostdlib` instead. In most
cases users are not supposed to call ld directly. On FreeBSD (and Google
servers and Android, if you consider them distributions), it has been proved
many packages don't need ld customization to function properly.
If you can't migrate off those packages right now, a shell script that gets
installed at "/usr/bin/ld" will probably work.
> clang NetBSD driver shall not hardcode LLD specific options
Several toolchains in the clang/lib/Driver/ToolChains detect lld and make lld
specific decisions there. While I hope linker specific options should be kept
at a minimum, I understand that sometimes it is unavoidable. When we have no
choice but to add linker specific options, adding such code to clangDriver is
an established practice followed by almost every toolchain (see Android,
Fuchsia, MinGW, MSVC, etc). Doing the driver thing in two places will more
likely to cause conflicts.
> the linker must have support for cross-building
I think this patch will actually harm cross building that targets NetBSD.
Before, ld.lld is shared by all ELF platforms: Linux, FreeBSD, Fuchsia,
Android, ChromeOS, etc. If an ELF change works on Linux, it will assuredly work
on other platforms. This patch will introduce a new driver that naturally gets
less test coverage.
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D70048/new/
https://reviews.llvm.org/D70048
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