Re: [PATCH v4 0/7] BaseTools: add support for GCC5 in LTO mode

["Gao, Liming" <liming.gao@intel.com>]

Ard:
  Thanks for your update. I have some comments for them. 
1) It uses GCC as Link for GCC44-GCC49. Have you done verification on them? I verify GCC49 in OVMFIa32X64 platform. It works. 
2) After this change, how to append new link option in platform DSC? Use style -Wl, ?
3) I see GCC5 uses gcc-ar as its SLINK, and GCC49 uses ar as its SLINK. Is gcc-ar required only by LTO?
4) Before GCC49 optimization, GCC49 means GCC49 or later, GCC5 can work with GCC49 tool chain configuration. But now, I configure gcc to point to GCC5, and build OVMF with GCC49 tool chain, it reports GenFw failure. I expect GCC5 work with GCC49 and GCC5 tool chain both. GCC49 for no lto, GCC5 for lto. I know Steven has provided the patch to fix this GenFw issue. 

GenFw: ERROR 3000: Invalid
  /home/hwu/work/lgao4/AllPkg/Build/Ovmf3264/DEBUG_GCC49/X64/MdeModulePkg/Core/Dxe/DxeMain/DEBUG/DxeCore.dll unsupported ELF EM_X86_64 relocation 0x9.
GenFw: ERROR 3000: Invalid
  /home/hwu/work/lgao4/AllPkg/Build/Ovmf3264/DEBUG_GCC49/X64/MdeModulePkg/Core/Dxe/DxeMain/DEBUG/DxeCore.dll unsupported ELF EM_X86_64 relocation 0x9.
GenFw: ERROR 3000: Invalid

Thanks
Liming
> -----Original Message-----
> From: Ard Biesheuvel [mailto:ard.biesheuvel@linaro.org]
> Sent: Wednesday, July 27, 2016 7:14 PM
> To: edk2-devel@lists.01.org; lersek@redhat.com; Gao, Liming
> <liming.gao@intel.com>; Shi, Steven <steven.shi@intel.com>; Zhu,
> Yonghong <yonghong.zhu@intel.com>; Justen, Jordan L
> <jordan.l.justen@intel.com>
> Cc: leif.lindholm@linaro.org; Ard Biesheuvel <ard.biesheuvel@linaro.org>
> Subject: [PATCH v4 0/7] BaseTools: add support for GCC5 in LTO mode
> 
> This v4 to introduce GCC5 is now a 7 piece series, including some
> preparatory cleanup patches that allow all GCC4x and CLANG35 toolchains
> to switch to using 'gcc' as the linker. This allows us to get rid of
> the wrapper script to marshall ld arguments in order to make them
> understandable by gcc, which is fragile and likely to cause problems in
> the future.
> 
> Since there appears to be a natural split between the 'legacy' GCC
> toolchains UNIXGCC, ELFGCC, and CYGGCC[xASL], both in term of supported
> architectures [IA32, X64, IPF] vs [IA32, X64, ARM, AARCH64], and in
> terms of maintenance, these toolchains are not moved to using 'gcc' as
> the linker, and instead, a new BUILDRULEFAMILY is introduced called GCCLD
> that will retain the old behavior.
> 
> The result is that GCC5 can align much more closely with its predecessors,
> making the expected maintenance burden of supporting GCC back to v4.4
> much lower.
> 
> Changes since v3:
> - like Steven does in his GCC5LTO patch, add -fno-builtin to IA32 and X64
>   CC_FLAGS; this addresses a build issue reported by Liming
> - add -Os the the linker flags as well, for AARCH64 this does not seem to
> make
>   a difference, but it is arguably correct since the LTO processing at link
>   time involves code generation as well
> - add Laszlo's ack to #2
> - new patch #6 to omit the autogenerated build-id from the PE/COFF binary
> 
> Changes since v2:
> - add license headers to LTO glue files for ARM and AARCH64 (#5)
> - get rid of lto-ld-wrapper script
> 
> Ard Biesheuvel (7):
>   BaseTools CLANG35: drop problematic use-movt and save-temps options
>   ArmVirtPkg/ArmVirtPrePiUniCoreRelocatable: ignore .hash and .note
>     sections
>   BaseTools UNIXGCC ELFGCC CYGGCC: clone GCC build rule family into
>     GCCLD
>   BaseTools GCC: use 'gcc' as the linker command for GCC44 and later
>   ArmPkg: add prebuilt glue binaries for GCC5 LTO support
>   BaseTools GCC: drop GNU notes section from EFI image
>   BaseTools GCC: add support for GCC v5.x in LTO mode
> 
>  ArmPkg/GccLto/liblto-aarch64.a                      | Bin 0 -> 1016 bytes
>  ArmPkg/GccLto/liblto-aarch64.s                      |  27 ++
>  ArmPkg/GccLto/liblto-arm.a                          | Bin 0 -> 2096 bytes
>  ArmPkg/GccLto/liblto-arm.s                          |  61 ++++
>  ArmVirtPkg/PrePi/ArmVirtPrePiUniCoreRelocatable.inf |   2 +-
>  ArmVirtPkg/PrePi/Scripts/PrePi-PIE.lds              |   3 +
>  BaseTools/Conf/build_rule.template                  |  31 +-
>  BaseTools/Conf/tools_def.template                   | 344 ++++++++++++++------
>  BaseTools/Scripts/GccBase.lds                       |   6 +
>  EmulatorPkg/Unix/Host/Host.inf                      |   6 +-
>  10 files changed, 372 insertions(+), 108 deletions(-)
>  create mode 100644 ArmPkg/GccLto/liblto-aarch64.a
>  create mode 100644 ArmPkg/GccLto/liblto-aarch64.s
>  create mode 100644 ArmPkg/GccLto/liblto-arm.a
>  create mode 100644 ArmPkg/GccLto/liblto-arm.s
> 
> --
> 2.7.4