Re: [PATCH edk2-staging 10/20] IntelUndiPkg/XGigUndiDxe: drop StdLibC library class reference

[Ryszard Knop <ryszard.knop@linux.intel.com>]

Andrew,

Unfortunately, not assigning something too large or using math
functions is not an option for us, as we share a significant amount of
code with Linux/FreeBSD drivers and maintainers of that code don't want
changes similar to the ones below (especially that, for all the other
drivers, intrinsics just work). Intrinsic lib for IA32 and others would
be very much preferred (and one that just works on any architecture, so
that we wouldn't have to add extra arch-specific LibraryClasses).

Thanks, Richard

On Wed, 2019-01-30 at 10:34 -0800, Andrew Fish wrote:
> > On Jan 30, 2019, at 9:26 AM, Ryszard Knop <
> > ryszard.knop@linux.intel.com> wrote:
> > 
> > That's actually not quite correct - we need this package to build
> > on
> > IA32. It's named rather unfortunately, since it's not the EDK2
> > StdLibC,
> > but rather a package in this repository - see IntelUndiPkg/LibC. It
> > contains the bare minimum of functionality required to fix missing
> > 64-
> > bit math/shifts on IA32 and missing memcpy/memset intrinsics. We
> > can't
> > prevent MSVC from yielding memcpy/memset either, so this was the
> > nasty
> > solution for build issues. You have included CompilerIntrinsicsLib
> > for
> > the same reason, too :)
> > 
> 
> Ryszard,
> 
> For IA32/X64 we avoid the compiler intrinsic libs via the coding
> standard. 
> 1) If you don't assign something too large at execution time with an
> = the compiler will not inline memcpy()/memset()
> 2) BaseLib.h has all the math functions that generate intrinsics that
> your code can call explicitly: 
> https://github.com/tianocore/edk2/blob/master/MdePkg/Include/Library/BaseLib.h#L3533
> 
> UINT64 X=0x100000000;
> UINT64 Y=2;
> 
> So:
> Y = X*Y;
> should be:
> Y = MultU64x64 (X, Y);
> 
> When ARM got added much later and some versions of ARM did not even
> have a divide instruction we gave up on trying to add more functions
> into all the existing IA32 code, and add the intrinsic lib. 
> 
> If we are going to add an intrinsic lib for x86 then we should
> probably add it to the MdePkg and it needs to support MSVC and GCC
> (as far as I can tell clang should work with the GCC intrinsics). 
> 
> Thanks,
> 
> Andrew Fish
> 
> 
> > I'm not aware of any X64/IA32 equivalent of your
> > CompilerIntrinsicsLib,
> > but I'd be happy to be proven wrong here. I'm off for the rest of
> > the
> > week - I'll continue with reviews and merging early next week.
> > 
> > Thanks, Richard.
> > 
> > On Wed, 2018-11-14 at 18:33 -0800, ard.biesheuvela wrote:
> > > StdLibc should not be used in drivers (it has dependencies on
> > > Shell
> > > protocols), but in fact, we don't appear to rely on it in the
> > > first
> > > place, so just drop the reference.
> > > 
> > > Contributed-under: TianoCore Contribution Agreement 1.1
> > > Signed-off-by: Ard Biesheuvel <ard.biesheuvel at linaro.org>
> > > ---
> > > IntelUndiPkg/XGigUndiDxe/XGigUndiDxe.inf | 1 -
> > > 1 file changed, 1 deletion(-)
> > > 
> > > diff --git a/IntelUndiPkg/XGigUndiDxe/XGigUndiDxe.inf
> > > b/IntelUndiPkg/XGigUndiDxe/XGigUndiDxe.inf
> > > index beee8aa8134e..b5747565fbea 100644
> > > --- a/IntelUndiPkg/XGigUndiDxe/XGigUndiDxe.inf
> > > +++ b/IntelUndiPkg/XGigUndiDxe/XGigUndiDxe.inf
> > > @@ -132,7 +132,6 @@ GCC:*_*_*_CC_FLAGS = -DEFI32
> > >   PrintLib
> > >   UefiLib
> > >   HiiLib
> > > -  StdLibC
> > > 
> > > [LibraryClasses.X64]
> > > 
> > 
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> 
>