Re: [PATCH v2 2/2] Makefile: infer CROSS_COMPILE from SRCARCH for LLVM=1 LLVM_IAS=1

From: Linus Torvalds
Date: Tue Jul 20 2021 - 17:16:12 EST

On Tue, Jul 20, 2021 at 1:52 PM Nick Desaulniers
<ndesaulniers@xxxxxxxxxx> wrote:
> > -CC = $(CROSS_COMPILE)gcc
> > +CC = $(CROSS_COMPILE)clang
> So you haven't been using LLD... :( (imagine using more than one
> thread to link, and being faster than

I started out just building my own clang - nothing else.

And now that I'm using the distro clang, the linker isn't even _close_
to a performance issue. Since clang is a big, slow, bloated pig.

I posted profiles and performance numbers of clang being three times
slower than gcc, and it was all just clang itself, not the linker. All
due to insanely expensive startup costs.

I suspect a lot of clang users build bloated C++ code where the time
to compile a single object file is so big that the startup costs don't
even show up. But for the (fairly) lean C kernel header files that
don't bring in millions of lines of headers for some template library,
startup costs are a big deal.

So honestly, I don't care at all about "imagine being faster than".

I can only _dream_ of clang itself not being 3x slower than gcc.