Re: [PATCH 0/3] fixes for CLANG35 on ARM

[Ard Biesheuvel <ard.biesheuvel@linaro.org>]

On Wed, 12 Dec 2018 at 15:01, Gao, Liming <liming.gao@intel.com> wrote:
>
> Ard:
>   I have no comments on this patch. So, CLANG38 has no issue. If so, could you recommend use CLANG38?
>

Yes, the latest is always preferred. However, since CLANG38 enables
LTO, you need the LLVMgold plugin, which is not shipped for all
versions of Clang by the distros. So it is good to keep CLANG35 as a
fallback.

> > -----Original Message-----
> > From: Ard Biesheuvel [mailto:ard.biesheuvel@linaro.org]
> > Sent: Wednesday, December 12, 2018 6:33 PM
> > To: edk2-devel@lists.01.org
> > Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>; Kinney, Michael D <michael.d.kinney@intel.com>; Gao, Liming
> > <liming.gao@intel.com>; Feng, Bob C <bob.c.feng@intel.com>; Leif Lindholm <leif.lindholm@linaro.org>; Laszlo Ersek
> > <lersek@redhat.com>
> > Subject: [PATCH 0/3] fixes for CLANG35 on ARM
> >
> > Building with Clang 3.5 for ARM may result in build breakage, due to the
> > fact that it may emit non-adjacent movw/movt instructions pairs which
> > cannot be relocated in PE/COFF. We pass -mno-movt in some places to
> > work around a related issue in the relocatable PrePi in ArmVirtPkg, but
> > we need to disable movw/movt entirely to really address this issue.
> >
> > So first, fix some breakage that results from building with -mlong-calls
> > in the optimized BaseMemoryLib code (#1)
> >
> > Patch #2 switches to -mkernel, which disables movw/movt generation (and
> > enabled -mlong-calls as a side effect)
> >
> > Patch #3 removes the now redundant, and incompatible command line
> > overrides for the relocatable PrePi.
> >
> > Cc: Michael D Kinney <michael.d.kinney@intel.com>
> > Cc: Liming Gao <liming.gao@intel.com>
> > Cc: Bob Feng <bob.c.feng@intel.com>
> > Cc: Leif Lindholm <leif.lindholm@linaro.org>
> > Cc: Laszlo Ersek <lersek@redhat.com>
> >
> > Ard Biesheuvel (3):
> >   MdePkg/BaseMemoryLibOptDxe ARM: add missing function annotations
> >   BaseTools/tools_def ARM CLANG35: work around -mno-movt option name
> >     change
> >   ArmVirtPkg/PrePi ARM CLANG35: drop incompatible command line option
> >
> >  ArmVirtPkg/ArmVirtQemuKernel.dsc                     | 5 -----
> >  ArmVirtPkg/ArmVirtXen.dsc                            | 5 -----
> >  BaseTools/Conf/tools_def.template                    | 2 +-
> >  MdePkg/Library/BaseMemoryLibOptDxe/Arm/CompareGuid.S | 1 +
> >  MdePkg/Library/BaseMemoryLibOptDxe/Arm/CompareMem.S  | 1 +
> >  MdePkg/Library/BaseMemoryLibOptDxe/Arm/CopyMem.S     | 1 +
> >  MdePkg/Library/BaseMemoryLibOptDxe/Arm/SetMem.S      | 5 +++++
> >  7 files changed, 9 insertions(+), 11 deletions(-)
> >
> > --
> > 2.19.2
>