回复: 回复: [edk2-devel] [PATCH] BaseTools: Add -ffat-lto-objects option in GCC5 tool chain

["gaoliming" <gaoliming@byosoft.com.cn>]

Laszlo:
  Sure. I will include gcc issue link in the commit message. I will send V2 patch. 

Thanks
Liming
> -----邮件原件-----
> 发件人: devel@edk2.groups.io <devel@edk2.groups.io> 代表 Laszlo Ersek
> 发送时间: 2021年5月20日 15:27
> 收件人: gaoliming <gaoliming@byosoft.com.cn>; devel@edk2.groups.io
> 抄送: 'Sergei Dmitrouk' <sergei@posteo.net>; 'Bob Feng'
> <bob.c.feng@intel.com>; 'Ard Biesheuvel' <ardb+tianocore@kernel.org>
> 主题: Re: 回复: [edk2-devel] [PATCH] BaseTools: Add -ffat-lto-objects option
> in GCC5 tool chain
> 
> On 05/20/21 04:37, gaoliming wrote:
> > Laszlo:
> >   Here is the discussion https://edk2.groups.io/g/devel/message/75299.
> >   Now, some uninitialized warning can't be detected on GCC5 tool chain,
> but can be detected on GCC49 tool chain.
> >   Edk2 CI only covers GCC5 tool chain. So, the merged code may impact
> GCC49 build.
> >   I add this option to expose such uninitialized warning in GCC5 tool chain
> and increase GCC5 tool chain coverage.
> >
> >   And, this is gcc issue
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90844
> >
> >   Yes. This change will expose some existing issues. I will include more
> detail in the commit message for this change.
> 
> Great, thanks for the info.
> 
> Can you please include the reference
> 
>   https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90844
> 
> in the commit message?
> 
> Acked-by: Laszlo Ersek <lersek@redhat.com>
> 
> Thanks!
> Laszlo
> 
> >
> > Thanks
> > Liming
> >> -----邮件原件-----
> >> 发件人: Laszlo Ersek <lersek@redhat.com>
> >> 发送时间: 2021年5月19日 15:23
> >> 收件人: devel@edk2.groups.io; gaoliming@byosoft.com.cn
> >> 抄送: Sergei Dmitrouk <sergei@posteo.net>; Bob Feng
> >> <bob.c.feng@intel.com>; Ard Biesheuvel <ardb+tianocore@kernel.org>
> >> 主题: Re: [edk2-devel] [PATCH] BaseTools: Add -ffat-lto-objects option in
> >> GCC5 tool chain
> >>
> >> Hi Liming,
> >>
> >> On 05/19/21 04:27, gaoliming wrote:
> >>> BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=3403
> >>>
> >>> This option can trig the uninitialized warning when lto is enabled.
> >>> The image size data is also collected for OVMF. There is no impact.
> >>>
> >>> Cc: Sergei Dmitrouk <sergei@posteo.net>
> >>> Cc: Bob Feng <bob.c.feng@intel.com>
> >>> Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
> >>> Signed-off-by: Liming Gao <gaoliming@byosoft.com.cn>
> >>> ---
> >>>  BaseTools/Conf/tools_def.template | 16 ++++++++--------
> >>>  1 file changed, 8 insertions(+), 8 deletions(-)
> >>
> >> I've now read the documentation on "-ffat-lto-objects", and I agree that
> >> it should not affect the final module executable sizes.
> >>
> >> However, I don't understand how this option *helps*. You mention
> >> "uninitialized warning". I find nothing related to that in the
> >> documentation.
> >>
> >> According to the documentation, "fat" LTO objects include both object
> >> code and intermediate language (GIMPLE) bytecode. Such objects can then
> >> be linked with, or without, link-time (= interprocedural) optimization.
> >> As I understand the documentation, "fat" LTO objects only make a
> >> difference if there are parts of the toolchain that are themselves
> >> unaware of LTO, and so need the GIMPLE bytecode to be present in the
> >> object files.
> >>
> >> I *guess* that this is the situation that we have in edk2 -- is there
> >> perhaps something in our toolchain(s) that does not "notice" LTO without
> >> "fat" LTO objects, and therefore we fail to emit a warning? Because,
> >> without LTO, we don't notice that an initialization is missing?
> >>
> >> This is too speculative. The commit message should please include more
> >> details. I'd like to understand what code in edk2 is affected, what the
> >> specific warning is, what the problematic component in the toolchain is
> >> (i.e., what tool requires GIMPLE bytecode to be present in the object file).
> >>
> >> Thanks,
> >> Laszlo
> >>
> >>
> >>
> >>>
> >>> diff --git a/BaseTools/Conf/tools_def.template
> >> b/BaseTools/Conf/tools_def.template
> >>> index 498696e583..aad5297385 100755
> >>> --- a/BaseTools/Conf/tools_def.template
> >>> +++ b/BaseTools/Conf/tools_def.template
> >>> @@ -2315,10 +2315,10 @@
> RELEASE_GCC49_AARCH64_DLINK_XIPFLAGS
> >> = -z common-page-size=0x20
> >>>  *_GCC5_IA32_OBJCOPY_FLAGS        =
> >>>  *_GCC5_IA32_NASM_FLAGS           = -f elf32
> >>>
> >>> -  DEBUG_GCC5_IA32_CC_FLAGS       = DEF(GCC5_IA32_CC_FLAGS)
> >> -flto -Os
> >>> +  DEBUG_GCC5_IA32_CC_FLAGS       =
> DEF(GCC5_IA32_CC_FLAGS)
> >> -ffat-lto-objects -flto -Os
> >>>    DEBUG_GCC5_IA32_DLINK_FLAGS    =
> >> DEF(GCC5_IA32_X64_DLINK_FLAGS) -flto -Os
> >> -Wl,-m,elf_i386,--oformat=elf32-i386
> >>>
> >>> -RELEASE_GCC5_IA32_CC_FLAGS       = DEF(GCC5_IA32_CC_FLAGS)
> >> -flto -Os -Wno-unused-but-set-variable -Wno-unused-const-variable
> >>> +RELEASE_GCC5_IA32_CC_FLAGS       = DEF(GCC5_IA32_CC_FLAGS)
> >> -ffat-lto-objects -flto -Os -Wno-unused-but-set-variable
> >> -Wno-unused-const-variable
> >>>  RELEASE_GCC5_IA32_DLINK_FLAGS    =
> >> DEF(GCC5_IA32_X64_DLINK_FLAGS) -flto -Os
> >> -Wl,-m,elf_i386,--oformat=elf32-i386
> >>>
> >>>    NOOPT_GCC5_IA32_CC_FLAGS       =
> DEF(GCC5_IA32_CC_FLAGS)
> >> -O0
> >>> @@ -2347,10 +2347,10 @@ RELEASE_GCC5_IA32_DLINK_FLAGS    =
> >> DEF(GCC5_IA32_X64_DLINK_FLAGS) -flto -Os -Wl,
> >>>  *_GCC5_X64_OBJCOPY_FLAGS         =
> >>>  *_GCC5_X64_NASM_FLAGS            = -f elf64
> >>>
> >>> -  DEBUG_GCC5_X64_CC_FLAGS        = DEF(GCC5_X64_CC_FLAGS)
> >> -flto -DUSING_LTO -Os
> >>> +  DEBUG_GCC5_X64_CC_FLAGS        = DEF(GCC5_X64_CC_FLAGS)
> >> -ffat-lto-objects -flto -DUSING_LTO -Os
> >>>    DEBUG_GCC5_X64_DLINK_FLAGS     =
> >> DEF(GCC5_X64_DLINK_FLAGS) -flto -Os
> >>>
> >>> -RELEASE_GCC5_X64_CC_FLAGS        = DEF(GCC5_X64_CC_FLAGS)
> >> -flto -DUSING_LTO -Os -Wno-unused-but-set-variable
> >> -Wno-unused-const-variable
> >>> +RELEASE_GCC5_X64_CC_FLAGS        = DEF(GCC5_X64_CC_FLAGS)
> >> -ffat-lto-objects -flto -DUSING_LTO -Os -Wno-unused-but-set-variable
> >> -Wno-unused-const-variable
> >>>  RELEASE_GCC5_X64_DLINK_FLAGS     =
> DEF(GCC5_X64_DLINK_FLAGS)
> >> -flto -Os
> >>>
> >>>    NOOPT_GCC5_X64_CC_FLAGS        =
> DEF(GCC5_X64_CC_FLAGS)
> >> -O0
> >>> @@ -2382,10 +2382,10 @@ RELEASE_GCC5_X64_DLINK_FLAGS     =
> >> DEF(GCC5_X64_DLINK_FLAGS) -flto -Os
> >>>  *_GCC5_ARM_VFRPP_FLAGS           = $(ARCHCC_FLAGS)
> >> $(PLATFORM_FLAGS) DEF(GCC_VFRPP_FLAGS)
> >>>  *_GCC5_ARM_CC_XIPFLAGS           =
> >> DEF(GCC5_ARM_CC_XIPFLAGS)
> >>>
> >>> -  DEBUG_GCC5_ARM_CC_FLAGS        =
> DEF(GCC5_ARM_CC_FLAGS)
> >> -flto -Wno-unused-but-set-variable -Wno-unused-const-variable
> >>> +  DEBUG_GCC5_ARM_CC_FLAGS        =
> DEF(GCC5_ARM_CC_FLAGS)
> >> -ffat-lto-objects -flto -Wno-unused-but-set-variable
> >> -Wno-unused-const-variable
> >>>    DEBUG_GCC5_ARM_DLINK_FLAGS     =
> >> DEF(GCC5_ARM_DLINK_FLAGS) -flto -Os
> >> -L$(WORKSPACE)/ArmPkg/Library/GccLto -llto-arm
> >> -Wl,-plugin-opt=-pass-through=-llto-arm
> >>>
> >>> -RELEASE_GCC5_ARM_CC_FLAGS        =
> DEF(GCC5_ARM_CC_FLAGS)
> >> -flto -Wno-unused-but-set-variable -Wno-unused-const-variable
> >>> +RELEASE_GCC5_ARM_CC_FLAGS        =
> DEF(GCC5_ARM_CC_FLAGS)
> >> -ffat-lto-objects -flto -Wno-unused-but-set-variable
> >> -Wno-unused-const-variable
> >>>  RELEASE_GCC5_ARM_DLINK_FLAGS     =
> >> DEF(GCC5_ARM_DLINK_FLAGS) -flto -Os
> >> -L$(WORKSPACE)/ArmPkg/Library/GccLto -llto-arm
> >> -Wl,-plugin-opt=-pass-through=-llto-arm
> >>>
> >>>    NOOPT_GCC5_ARM_CC_FLAGS        =
> DEF(GCC5_ARM_CC_FLAGS)
> >> -O0
> >>> @@ -2416,11 +2416,11 @@ RELEASE_GCC5_ARM_DLINK_FLAGS     =
> >> DEF(GCC5_ARM_DLINK_FLAGS) -flto -Os -L$(WORKS
> >>>  *_GCC5_AARCH64_VFRPP_FLAGS       = $(ARCHCC_FLAGS)
> >> $(PLATFORM_FLAGS) DEF(GCC_VFRPP_FLAGS)
> >>>  *_GCC5_AARCH64_CC_XIPFLAGS       =
> >> DEF(GCC5_AARCH64_CC_XIPFLAGS)
> >>>
> >>> -  DEBUG_GCC5_AARCH64_CC_FLAGS    =
> >> DEF(GCC5_AARCH64_CC_FLAGS) -flto -Wno-unused-but-set-variable
> >> -Wno-unused-const-variable
> >>> +  DEBUG_GCC5_AARCH64_CC_FLAGS    =
> >> DEF(GCC5_AARCH64_CC_FLAGS) -ffat-lto-objects -flto
> >> -Wno-unused-but-set-variable -Wno-unused-const-variable
> >>>    DEBUG_GCC5_AARCH64_DLINK_FLAGS =
> >> DEF(GCC5_AARCH64_DLINK_FLAGS) -flto -Os
> >> -L$(WORKSPACE)/ArmPkg/Library/GccLto -llto-aarch64
> >> -Wl,-plugin-opt=-pass-through=-llto-aarch64 -Wno-lto-type-mismatch
> >>>    DEBUG_GCC5_AARCH64_DLINK_XIPFLAGS = -z
> >> common-page-size=0x20
> >>>
> >>> -RELEASE_GCC5_AARCH64_CC_FLAGS    =
> >> DEF(GCC5_AARCH64_CC_FLAGS) -flto -Wno-unused-but-set-variable
> >> -Wno-unused-const-variable
> >>> +RELEASE_GCC5_AARCH64_CC_FLAGS    =
> >> DEF(GCC5_AARCH64_CC_FLAGS) -ffat-lto-objects -flto
> >> -Wno-unused-but-set-variable -Wno-unused-const-variable
> >>>  RELEASE_GCC5_AARCH64_DLINK_FLAGS =
> >> DEF(GCC5_AARCH64_DLINK_FLAGS) -flto -Os
> >> -L$(WORKSPACE)/ArmPkg/Library/GccLto -llto-aarch64
> >> -Wl,-plugin-opt=-pass-through=-llto-aarch64 -Wno-lto-type-mismatch
> >>>  RELEASE_GCC5_AARCH64_DLINK_XIPFLAGS = -z
> >> common-page-size=0x20
> >>>
> >>>
> >
> >
> >
> 
> 
> 
> 
>