[lld] [patch] Mach-O Performance fix

Hello,

While profiling lld, I found that lld spend more than 10% of the link time doing useless vector copy induced by used of ‘auto’ keyword.

Here is a patch to avoid that copy by explicitly requiring a reference (auto&). The culprit was ‘auto vec = pos->second’

Maybe we should review other places where auto is used to make sure that kind of issue does not occurs.

-- Jean-Daniel

nocopy.patch (1.09 KB)

Thanks! Committed in r222455

-Nick