[PATCH] D24826: [LTO] Add -flto-jobs=N to control backend parallelism

[Teresa Johnson via cfe-commits]

tejohnson added a comment.

In https://reviews.llvm.org/D24826#549788, @mehdi_amini wrote:

> The Gold path looks fine. 
>  On OSX, we would have the clang driver relying on a LLVM cl::opt, for which I don't think there is any precedent. CC Duncan for advice.


I do see other uses of -mllvm in lib/Driver/Tools.cpp, but are you talking about something else?

> Also I don't think the same option should be used for the parallel LTO codegen: it actually does not generate the same binary, which should deserve a dedicated opt-in (What if I mix ThinLTO and LTO, and I don't want // codegen?)


Ok good point. I can change this to -fthinlto_jobs. However, while the two parallel settings are separate in the LTO API, currently the gold-plugin jobs option controls both, so I will need to do a preparatory gold-plugin patch to split this into thinlto_jobs and lto_jobs. On the libLTO/ld64 path, looks like the current -mllvm -threads only affects ThinLTO so there is no work to do there.


https://reviews.llvm.org/D24826