[PATCH v2 0/4] riscv: enable HAVE_LD_DEAD_CODE_DATA_ELIMINATION

[Palmer Dabbelt]

On Tue, 20 Jun 2023 14:08:33 PDT (-0700), Palmer Dabbelt wrote:
> On Tue, 20 Jun 2023 13:47:07 PDT (-0700), ndesaulniers at google.com wrote:
>> On Tue, Jun 20, 2023 at 4:41 PM Palmer Dabbelt <palmer at dabbelt.com> wrote:
>>>
>>> On Tue, 20 Jun 2023 13:32:32 PDT (-0700), ndesaulniers at google.com wrote:
>>> > On Tue, Jun 20, 2023 at 4:13 PM Conor Dooley <conor at kernel.org> wrote:
>>> >>
>>> >> On Tue, Jun 20, 2023 at 04:05:55PM -0400, Nick Desaulniers wrote:
>>> >> > On Mon, Jun 19, 2023 at 6:06 PM Palmer Dabbelt <palmer at dabbelt.com> wrote:
>>> >> > > On Thu, 15 Jun 2023 06:54:33 PDT (-0700), Palmer Dabbelt wrote:
>>> >> > > > On Wed, 14 Jun 2023 09:25:49 PDT (-0700), jszhang at kernel.org wrote:
>>> >> > > >> On Wed, Jun 14, 2023 at 07:49:17AM -0700, Palmer Dabbelt wrote:
>>> >> > > >>> On Tue, 23 May 2023 09:54:58 PDT (-0700), jszhang at kernel.org wrote:
>>> >>
>>> >> > > >> Commit 3b90b09af5be ("riscv: Fix orphan section warnings caused by
>>> >> > > >> kernel/pi") touches vmlinux.lds.S, so to make the merge easy, this
>>> >> > > >> series is based on 6.4-rc2.
>>> >> > > >
>>> >> > > > Thanks.
>>> >> > >
>>> >> > > Sorry to be so slow here, but I think this is causing LLD to hang on
>>> >> > > allmodconfig.  I'm still getting to the bottom of it, there's a few
>>> >> > > other things I have in flight still.
>>> >> >
>>> >> > Confirmed with v3 on mainline (linux-next is pretty red at the moment).
>>> >> > https://lore.kernel.org/linux-riscv/20230517082936.37563-1-falcon@tinylab.org/
>>> >>
>>> >> Just FYI Nick, there's been some concurrent work here from different
>>> >> people working on the same thing & the v3 you linked (from Zhangjin) was
>>> >> superseded by this v2 (from Jisheng).
>>> >
>>> > Ah! I've been testing the deprecated patch set, sorry I just looked on
>>> > lore for "dead code" on riscv-linux and grabbed the first thread,
>>> > without noticing the difference in authors or new version numbers for
>>> > distinct series. ok, nevermind my noise.  I'll follow up with the
>>> > correct patch set, sorry!
>>>
>>> Ya, I hadn't even noticed the v3 because I pretty much only look at
>>> patchwork these days.  Like we talked about in IRC, I'm going to go test
>>> the merge of this one and see what's up -- I've got it staged at
>>> <https://git.kernel.org/pub/scm/linux/kernel/git/palmer/linux.git/commit/?h=for-next&id=1bd2963b21758a773206a1cb67c93e7a8ae8a195>,
>>> though that won't be a stable hash if it's actually broken...
>>
>> Ok, https://lore.kernel.org/linux-riscv/20230523165502.2592-1-jszhang@kernel.org/
>> built for me.  If you're seeing a hang, please let me know what
>> version of LLD you're using and I'll build that tag from source to see
>> if I can reproduce, then bisect if so.
>>
>> $ ARCH=riscv LLVM=1 /usr/bin/time -v make -j128 allmodconfig vmlinux
>> ...
>>         Elapsed (wall clock) time (h:mm:ss or m:ss): 2:35.68
>> ...
>>
>> Tested-by: Nick Desaulniers <ndesaulniers at google.com> # build
>
> OK, it triggered enough of a rebuild that it might take a bit for
> anything to filter out.

I'm on LLVM 16.0.2

    $ git describe
    llvmorg-16.0.2
    $ git log | head -n1
    commit 18ddebe1a1a9bde349441631365f0472e9693520

that seems to hang for me -- or at least run for an hour without 
completing, so I assume it's hung.  I'm not wed to 16.0.2, it just 
happens to be the last time I bumped the toolchain.  I'm moving to 
16.0.5 to see if that changes anything.

>
> Thanks!
>
>>
>>>
>>> >
>>> >>
>>> >> Cheers,
>>> >> Conor.
>>> >
>>> >
>>> >
>>> > --
>>> > Thanks,
>>> > ~Nick Desaulniers
>>
>>
>>
>> --
>> Thanks,
>> ~Nick Desaulniers