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

-----Original Message-----
From: Ard Biesheuvel [mailto:ard.biesheuvel@...]
Sent: Wednesday, July 27, 2016 7:14 PM
To: edk2-devel@...; lersek@...; Gao, Liming
<liming.gao@...>; Shi, Steven <steven.shi@...>; Zhu,
Yonghong <yonghong.zhu@...>; Justen, Jordan L
<jordan.l.justen@...>
Cc: leif.lindholm@...; Ard Biesheuvel <ard.biesheuvel@...>
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