Re: [edk2-devel] [PATCH v2] ArmPkg/CompilerIntrinsicsLib: provide atomics intrinsics

["Leif Lindholm" <leif@nuviainc.com>]

On Thu, May 21, 2020 at 15:31:44 +0200, Ard Biesheuvel wrote:
> > > That does mean you would need GCC 10.2 at least, or you get the error,
> > > unless we merge this patch as well. That would mean the intrinsics are never
> > > used in practice, but using a compiler that does use them will not break the
> > > build.
> > > 
> > > I am leaning towards omitting this patch, but I could be convinced to adopt
> > > both mitigations. But the #pragma is strongly preferred.
> > 
> > What is the codesize impact on a full RELEASE image?
> 
> Not sure how that matters? Given the modular nature of EDK2, I would not
> expect the outline atomics to have any measurable size benefit. The
> intrinsics library is static, with each of the 100 different functions
> emitted into a separate section, so you only get what you use.

Ah, I'd missed (misfiled?) the separate section thing.

> > If non-negligable, how about #ifdefing the whole content out unless
> > some specific preprocessor flag is passed? Then at least there's a
> > quick workaround for anyone who needs it.
> > 
> 
> The linker will only incorporate the parts that are actually used.

Yeah, so not an issue.
OK, then I would vote *for* merging the patch regardless. We know how
long some toolchain versions can stick around simply because they were
mentioned in some blog post somewhere that ended up high in search
rankings.

Once gcc 10.2 is released (and we have verified the problem can be
worked around elsewhere), I guess we could add a note saying "once all
gcc 10.0 and 10.1 toolchains are considered obsolete, this file can
be deleted".

/
    Leif