Re: [edk2-devel] [RFC] Move CompilerIntrinsicsLib and ArmSoftFloatLib to MdePkg

["Michael D Kinney" <michael.d.kinney@intel.com>]

> -----Original Message-----
> From: Ard Biesheuvel <ardb@kernel.org>
> Sent: Friday, August 2, 2024 1:46 AM
> To: Oliver Smith-Denny <osde@linux.microsoft.com>
> Cc: devel@edk2.groups.io; Leif Lindholm <quic_llindhol@quicinc.com>; Sami
> Mujawar <sami.mujawar@arm.com>; Kinney, Michael D
> <michael.d.kinney@intel.com>; Liming Gao <gaoliming@byosoft.com.cn>; Liu,
> Zhiguang <zhiguang.liu@intel.com>
> Subject: Re: [RFC] Move CompilerIntrinsicsLib and ArmSoftFloatLib to MdePkg
> 
> On Fri, 2 Aug 2024 at 00:39, Oliver Smith-Denny
> <osde@linux.microsoft.com> wrote:
> >
> > CompilerIntrinsicsLib and ArmSoftFloatLib add ARM/AARCH64 compiler
> > intrinsics and floating point functions required by OpenSSL,
> > respectively. CompilerIntrinsicsLib is used almost in every DSC that
> > builds ARM/AARCH64 and ArmSoftFloatLib is used by every DSC that builds
> > logic from OpenSSL.
> 
> What's even worse: OpenSSL doesn't really use floating point at all -
> the only reason we need this is because there is some global double_t
> somewhere that records entropy or somesuch, but IIRC that code is not
> actually used.
> 
> So perhaps we could add a hack in OpensslLib to work around this in
> one way or another for ARM only, and get rid of SoftFloatLib
> altogether.
> 
> > Together these make almost every DSC have a
> > dependency on ArmPkg, which is odd and for a handful, MdeModulePkg,
> > EmbeddedPkg, and ShellPkg, namely, it is a circular dependency.
> >
> > There have been previous mailing list suggestions to move
> > CompilerIntrinsicsLib to MdePkg (possibly combining with other arch
> > intrinsics). I am not sure the end status of those conversations. By
> > moving these two libraries to MdePkg package, we accomplish a few
> > things:
> >
> >    - Removing the circular dependency from MdeModulePkg and ShellPkg
> >      (EmbeddedPkg has other ArmPkg dependencies)
> >
> >    - Aligning MdePkg as the base package where baseline build and spec
> >      dependencies are found with other industry standard behavior
> >
> >    - Detangling ArmPkg and making ARM/AARCH64 more of a first class
> >      citizen in edk2 instead of bolted onto the side
> >
> > There is no functional change here and the amount of work is light, but
> > I think it moves edk2 in the direction it wants to go, so I'm happy to
> > put up a PR for this, but I wanted to get feedback before I did so. This
> > aligns with similar efforts, such as moving more ARM/AARCH64 chipset
> > definitions to MdePkg from ArmPkg [1][2][3]. This also aligns to the
> > overall goal of deleting ArmPkg:
> > https://bugzilla.tianocore.org/show_bug.cgi?id=4121
> >
> 
> Intrinsics are tightly coupled with the toolchain, and so it would
> make sense for the basetools to provide them. Intrinsics are also
> -essentially- build once, run everywhere objects so I don't think we
> need the typical handling for them either, and we could just build
> them once when we build the basetools.

I do not think this is possible

* BaseTools are built with the host compiler.
* FW is built with the target compiler which may be different than
  the host compiler.  And multiple target compilers or target compiler
  CPU target may be used from a single host build environment.  An
  intrinsic lib instance is needed for each unique target used.






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