Re: [PATCH dwarves v3 0/3] permit merging all dwarf cu's for clang lto built binary

[Arnaldo Carvalho de Melo <acme@kernel.org>]

Em Tue, Mar 30, 2021 at 08:20:20PM -0700, Yonghong Song escreveu:
> On 3/30/21 11:24 AM, Arnaldo Carvalho de Melo wrote:
> > Em Tue, Mar 30, 2021 at 03:08:06PM -0300, Arnaldo Carvalho de Melo escreveu:
> > > [acme@five pahole]$ fullcircle tcp_bbr.o
> > > [acme@five pahole]$

> > > This one is dealt with, doing some more tests and looking at that
> > > array[] versus array[0].

> > I've pushed what I have to the main repos at kernel.org and github,
> > please check, I'll continue from there.

> Looks good. Thanks!

> I will try to experiment with an alternative way ([1]) to check whether
> cross-cu reference happens or not. But at least checking flags
> approach can be adapted to gcc (if we want after comparing the alternative)
> since gcc always has flags in dwarf.
 
> [1] https://lore.kernel.org/bpf/d34a3d62-bae8-3a30-26b6-4e5e8efcd0af@fb.com/T/#m1b0b1206091c19a90b15d054aa26239101289f84

I thought about some other method, like adding a ELF note to vmlinux
stating that this was built with LTO, that would be the fastest way, I
think. If that note wasn't there, then we would fallback to looking at
inter CU references, that way we would have the best of both worlds and
wouldn't incur in per-CU DW_AT_producer overheads with the flags for
each object file.

- Arnaldo