Re: Threading the compiler

[Ian Lance Taylor <iant at google dot com>]

"Dave Korn" <dave.korn@artimi.com> writes:

> > The main place where threading may make sense, especially
> > with LTO, is the linker. This is a longer lived task, and
> > is the last step of compilation, where no other parellel
> > processes are active. Moreover, linking tends to be I/O
> > intensive, so a number of threads will likely be blocked
> > for I/O.
> 
>   I'm not really sure how this would play with SMP (as opposed to threading).
> I don't see why you think threading could be particularly useful in the
> linker?  It's the pipeline of compiler optimisation passes that looks like an
> obvious candidate for threading to me.

It's irrelevant to the main discussion here, but in fact there is a
fair amount of possible threading in the linker proper, quite apart
from LTO.  The linker spends a lot of time reading large files, and
the I/O wait can be parallelized.  And the linker spends a reasonable
amount of time computing relocations, which can be parallelized such
that the relocations for each input file are computed independently.

Ian