On Wed, Nov 04, 2020 at 01:06:03PM -0800, Tom Stellard wrote:
On 11/4/20 3:57 PM, Jakub Jelinek wrote:
> On Wed, Nov 04, 2020 at 03:51:40PM -0500, Neal Gompa wrote:
> > > Well, gcc really should have either weak or strong dependency on make too
> > > given that -flto is now used everywhere.
> >
> > The goal of this change seems to include removal of Make as a
> > dependency for the LTO wrapper used by GCC.
>
> That is definitely not something that really happened in GCC, the only
> change that has been done is to make sure that gcc -flto doesn't fail
> because of missing make, but missing make will just mean that the
> compilation will be significantly slower.
>
My understanding was that the performance of gcc -flto when using something
other than make (e.g. ninja) to build was the same whether or not you have
make installed[1]. Is this correct?
That is not correct.
-flto=jobserver will only parallelize if a make jobserver is active and thus
only when executed from make -jN with + at the start of the command,
but -flto=auto uses jobserver if it is detected, otherwise falls back to
detecting number of threads to use and parallelizing using that (but it uses
make for that parallelization), or say -flto=32 asks for 32 parallel jobs
(and again needs make to do that).
Jakub