[PATCH] D15641: [Driver] Pass -O* to the gold plugin via -plugin-opt

[Rafael Espíndola via cfe-commits]

>> This introduces a meaning to -ON during the link. That normally show up by people passing CFLAGS when linking.
>
> I'm not sure what you mean? When I build clang with cake the link is driven by clang, it will accept the O flag by not propagate it to the actual linker. How would CFLAGS help?

It doesn't. It is just a way -O3 sometimes ends up in a link (clang) line.

> Now we thought about that a few months ago and we were planning to do something during the bring up of ThinLTO.
> The alternative to the command line flag is to encode the optimization level in the bitcode itself.
> It may have the advantage (for ThinLTO) to be able to LTO each file with different optimization level.

I don't have a strong preference one way or the other.

Cheers,
Rafael