RFC: Should the linker support '--fast' and if so, what should it do ?

[Fangrui Song]

On Wed, Mar 18, 2026 at 4:39 AM Nick Clifton <nickc@redhat.com> wrote:
>
> Hi Guys,
>
>   OK, this one is probably going to be controversial...
>
>   I was wondering whether it would be useful to have a linker command
>   line option to request a fast link, even if the results are not as
>   good as a normal link.  In particular it occurred to me the merging
>   string sections (and other mergeable sections) is not actually
>   required by the ELF standard.  So if we skip that step quite a lot of
>   time can be saved.  In my tests for example I saw time savings of
>   around 20% for big links.  Of course the resulting executables are
>   unnecessarily large and probably a bit slower than their merged
>   equivalents, but for test builds during a development process this
>   might not be an issue.
>
>   So - am I going mad here or is this something worth looking into ?
>
> Cheers
>   Nick
>

We can reuse -O for this purpose...

In ld.lld, -O1 is the default.

-O0 disables constant merge of SHF_MERGE.

-O2 enables some computation heavy size optimization:

enable string suffix merge of SHF_MERGE|SHF_STRINGS. This is very slow
and not parallel.
--compress-debug-sections=zlib uses zlib compression with higher
compression ratio.