[llvm-dev] [RFC] Annotating global functions and variables to prevent ICF during linking

[Eric Christopher via llvm-dev]

+Peter Collingbourne <pcc at google.com> +Fangrui Song <maskray at google.com>

I'm also not sure I understand. Perhaps an example? i.e. how does the
current system not work here in safe mode?

-eric

On Mon, Mar 22, 2021 at 8:27 PM Zequan Wu via llvm-dev <
llvm-dev at lists.llvm.org> wrote:

> Hi all,
>
> Background:
> It's been a longstanding difficulty of debugging with ICF. Programmers
> don't have control over which sections should be folded by ICF, which
> sections shouldn't. The existing address significant table won't have
> effect for code sections during all ICF mode in both ld.lld and lld-link.
> By switching to safe ICF could mark code sections as unique, but at a cost
> of increasing binary size out of control. So, it would be good if
> programmers could selectively disable ICF in source code by annotating
> global functions/variables with an attribute to improve debugging
> experience and have the control on the binary size increase.
>
> My plan is to add a new section table(`.no_icf`) to object files. Sections
> of all symbols inside the table should not be folded by all ICF mode. And
> symbols can only be added into the table by annotating global
> functions/variables with a new attribute(`no_icf`) in source code.
>
> What do you think about this approach?
>
> Thanks,
> Zequan
>
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