Re: Calling testers for another Dead Function Optimisation update

[Jamie Lokier <lk@tantalophile.demon.co.uk>]

Graham Stoney wrote:
> > This is the way the kernel used to be, with the kernel objects
> > as *.a files instead of *.o files.
> 
> I'm definitely with you on this one. Using ld -r in intermediate
> stages is defeating the linker's natural ability to exclude unused
> objects. My patch achieves a similar effect by allowing the linker to
> exclude unused functions, but it does so in a very torturous way. I'd
> prefer to have both .a's for wholesale dead object elimination _and_
> -ffunction-sections for elimination of any remaining dead functions.

OTOH .a's are slower than ld -r.  They don't save any I/O: all the
enclosed object files have to be duplicated until the final link anyway.
ld -r removes duplicate symbols and debugging information, which makes
the .o files smaller than the corresponding .a files and faster to read.

Using .a _and_ -ffunction-sections at the same time would surely be the
worst possible combination.

-- Jamie