[PATCH 0/2] Remove -fno-unit-at-a-time and -funit-at-a-time compiler flags entirely

[PATCH 0/2] Remove -fno-unit-at-a-time and -funit-at-a-time compiler flags entirely

[Masahiro Yamada]

1/2: remove dead code, which is logically obvious
     because the minimum GCC version is now 4.6

2/2: we can say -funit-at-a-time is no longer useful
     according to GCC 4.6 manual

I hope, this series can be applied through x86 tree.



Masahiro Yamada (2):
  um: remove -fno-unit-at-a-time workaround for pre-4.0 GCC
  x86, powerpc: remove -funit-at-a-time compiler option entirely

 arch/powerpc/Makefile | 4 ----
 arch/x86/Makefile     | 4 ----
 arch/x86/Makefile.um  | 9 ---------
 3 files changed, 17 deletions(-)

-- 
2.7.4

[PATCH 1/2] um: remove -fno-unit-at-a-time workaround for pre-4.0 GCC

[Masahiro Yamada]

Commit cafa0010cd51 ("Raise the minimum required gcc version to 4.6")
bumped the minimum GCC version to 4.6 for all architectures.

'$(call cc-option,-fno-unit-at-a-time)' is now dead code since
'$(cc-version) -lt 0400' is always false.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
---

 arch/x86/Makefile.um | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/arch/x86/Makefile.um b/arch/x86/Makefile.um
index 91085a0..577976b 100644
--- a/arch/x86/Makefile.um
+++ b/arch/x86/Makefile.um
@@ -26,12 +26,8 @@ cflags-y += $(call cc-option,-mpreferred-stack-boundary=2)
 # an unresolved reference.
 cflags-y += -ffreestanding
 
-# Disable unit-at-a-time mode on pre-gcc-4.0 compilers, it makes gcc use
-# a lot more stack due to the lack of sharing of stacklots.  Also, gcc
-# 4.3.0 needs -funit-at-a-time for extern inline functions.
-KBUILD_CFLAGS += $(shell if [ $(cc-version) -lt 0400 ] ; then \
-			echo $(call cc-option,-fno-unit-at-a-time); \
-			else echo $(call cc-option,-funit-at-a-time); fi ;)
+# gcc 4.3.0 needs -funit-at-a-time for extern inline functions.
+KBUILD_CFLAGS += $(call cc-option,-funit-at-a-time)
 
 KBUILD_CFLAGS += $(cflags-y)
 
-- 
2.7.4

[PATCH 2/2] x86, powerpc: remove -funit-at-a-time compiler option entirely

[Masahiro Yamada]

GCC 4.6 manual says:

-funit-at-a-time
  This option is left for compatibility reasons. -funit-at-a-time has
  no effect, while -fno-unit-at-a-time implies -fno-toplevel-reorder
  and -fno-section-anchors.
  Enabled by default.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
---

 arch/powerpc/Makefile | 4 ----
 arch/x86/Makefile     | 4 ----
 arch/x86/Makefile.um  | 5 -----
 3 files changed, 13 deletions(-)

diff --git a/arch/powerpc/Makefile b/arch/powerpc/Makefile
index 8a2ce14..854199c 100644
--- a/arch/powerpc/Makefile
+++ b/arch/powerpc/Makefile
@@ -228,10 +228,6 @@ KBUILD_CFLAGS += $(call cc-option,-mno-vsx)
 KBUILD_CFLAGS += $(call cc-option,-mno-spe)
 KBUILD_CFLAGS += $(call cc-option,-mspe=no)
 
-# Enable unit-at-a-time mode when possible. It shrinks the
-# kernel considerably.
-KBUILD_CFLAGS += $(call cc-option,-funit-at-a-time)
-
 # FIXME: the module load should be taught about the additional relocs
 # generated by this.
 # revert to pre-gcc-4.4 behaviour of .eh_frame
diff --git a/arch/x86/Makefile b/arch/x86/Makefile
index 88398fd..3508049 100644
--- a/arch/x86/Makefile
+++ b/arch/x86/Makefile
@@ -130,10 +130,6 @@ else
 
         KBUILD_CFLAGS += -mno-red-zone
         KBUILD_CFLAGS += -mcmodel=kernel
-
-        # -funit-at-a-time shrinks the kernel .text considerably
-        # unfortunately it makes reading oopses harder.
-        KBUILD_CFLAGS += $(call cc-option,-funit-at-a-time)
 endif
 
 ifdef CONFIG_X86_X32
diff --git a/arch/x86/Makefile.um b/arch/x86/Makefile.um
index 577976b..1db7913 100644
--- a/arch/x86/Makefile.um
+++ b/arch/x86/Makefile.um
@@ -26,9 +26,6 @@ cflags-y += $(call cc-option,-mpreferred-stack-boundary=2)
 # an unresolved reference.
 cflags-y += -ffreestanding
 
-# gcc 4.3.0 needs -funit-at-a-time for extern inline functions.
-KBUILD_CFLAGS += $(call cc-option,-funit-at-a-time)
-
 KBUILD_CFLAGS += $(cflags-y)
 
 else
@@ -50,6 +47,4 @@ ELF_FORMAT := elf64-x86-64
 LINK-$(CONFIG_LD_SCRIPT_DYN) += -Wl,-rpath,/lib64
 LINK-y += -m64
 
-# Do unit-at-a-time unconditionally on x86_64, following the host
-KBUILD_CFLAGS += $(call cc-option,-funit-at-a-time)
 endif
-- 
2.7.4

Re: [PATCH 2/2] x86, powerpc: remove -funit-at-a-time compiler option entirely

[Ingo Molnar]

* Masahiro Yamada <yamada.masahiro@socionext.com> wrote:

> GCC 4.6 manual says:
> 
> -funit-at-a-time
>   This option is left for compatibility reasons. -funit-at-a-time has
>   no effect, while -fno-unit-at-a-time implies -fno-toplevel-reorder
>   and -fno-section-anchors.
>   Enabled by default.
> 
> Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
> ---
> 
>  arch/powerpc/Makefile | 4 ----
>  arch/x86/Makefile     | 4 ----
>  arch/x86/Makefile.um  | 5 -----
>  3 files changed, 13 deletions(-)
> 
> diff --git a/arch/x86/Makefile b/arch/x86/Makefile
> index 88398fd..3508049 100644
> --- a/arch/x86/Makefile
> +++ b/arch/x86/Makefile
> @@ -130,10 +130,6 @@ else
>  
>          KBUILD_CFLAGS += -mno-red-zone
>          KBUILD_CFLAGS += -mcmodel=kernel
> -
> -        # -funit-at-a-time shrinks the kernel .text considerably
> -        # unfortunately it makes reading oopses harder.
> -        KBUILD_CFLAGS += $(call cc-option,-funit-at-a-time)
>  endif
>  
>  ifdef CONFIG_X86_X32
> diff --git a/arch/x86/Makefile.um b/arch/x86/Makefile.um
> index 577976b..1db7913 100644
> --- a/arch/x86/Makefile.um
> +++ b/arch/x86/Makefile.um
> @@ -26,9 +26,6 @@ cflags-y += $(call cc-option,-mpreferred-stack-boundary=2)
>  # an unresolved reference.
>  cflags-y += -ffreestanding
>  
> -# gcc 4.3.0 needs -funit-at-a-time for extern inline functions.
> -KBUILD_CFLAGS += $(call cc-option,-funit-at-a-time)
> -
>  KBUILD_CFLAGS += $(cflags-y)
>  
>  else
> @@ -50,6 +47,4 @@ ELF_FORMAT := elf64-x86-64
>  LINK-$(CONFIG_LD_SCRIPT_DYN) += -Wl,-rpath,/lib64
>  LINK-y += -m64
>  
> -# Do unit-at-a-time unconditionally on x86_64, following the host
> -KBUILD_CFLAGS += $(call cc-option,-funit-at-a-time)
>  endif

Acked-by: Ingo Molnar <mingo@kernel.org>

Thanks,

	Ingo

Re: [PATCH 2/2] x86, powerpc: remove -funit-at-a-time compiler option entirely

[Michael Ellerman]

Masahiro Yamada <yamada.masahiro@socionext.com> writes:

> GCC 4.6 manual says:
>
> -funit-at-a-time
>   This option is left for compatibility reasons. -funit-at-a-time has
>   no effect, while -fno-unit-at-a-time implies -fno-toplevel-reorder
>   and -fno-section-anchors.
>   Enabled by default.
>
> Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
> ---
>
>  arch/powerpc/Makefile | 4 ----
>  arch/x86/Makefile     | 4 ----
>  arch/x86/Makefile.um  | 5 -----
>  3 files changed, 13 deletions(-)
>
> diff --git a/arch/powerpc/Makefile b/arch/powerpc/Makefile
> index 8a2ce14..854199c 100644
> --- a/arch/powerpc/Makefile
> +++ b/arch/powerpc/Makefile
> @@ -228,10 +228,6 @@ KBUILD_CFLAGS += $(call cc-option,-mno-vsx)
>  KBUILD_CFLAGS += $(call cc-option,-mno-spe)
>  KBUILD_CFLAGS += $(call cc-option,-mspe=no)
>  
> -# Enable unit-at-a-time mode when possible. It shrinks the
> -# kernel considerably.
> -KBUILD_CFLAGS += $(call cc-option,-funit-at-a-time)
> -

Thanks for cleaning it up.

Acked-by: Michael Ellerman <mpe@ellerman.id.au>

cheers

Re: [PATCH 1/2] um: remove -fno-unit-at-a-time workaround for pre-4.0 GCC

[Richard Weinberger]

Am Montag, 12. November 2018, 03:35:19 CET schrieb Masahiro Yamada:
> Commit cafa0010cd51 ("Raise the minimum required gcc version to 4.6")
> bumped the minimum GCC version to 4.6 for all architectures.
> 
> '$(call cc-option,-fno-unit-at-a-time)' is now dead code since
> '$(cc-version) -lt 0400' is always false.
> 
> Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
> ---
> 
>  arch/x86/Makefile.um | 8 ++------
>  1 file changed, 2 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/x86/Makefile.um b/arch/x86/Makefile.um
> index 91085a0..577976b 100644
> --- a/arch/x86/Makefile.um
> +++ b/arch/x86/Makefile.um
> @@ -26,12 +26,8 @@ cflags-y += $(call cc-option,-mpreferred-stack-boundary=2)
>  # an unresolved reference.
>  cflags-y += -ffreestanding
>  
> -# Disable unit-at-a-time mode on pre-gcc-4.0 compilers, it makes gcc use
> -# a lot more stack due to the lack of sharing of stacklots.  Also, gcc
> -# 4.3.0 needs -funit-at-a-time for extern inline functions.
> -KBUILD_CFLAGS += $(shell if [ $(cc-version) -lt 0400 ] ; then \
> -			echo $(call cc-option,-fno-unit-at-a-time); \
> -			else echo $(call cc-option,-funit-at-a-time); fi ;)
> +# gcc 4.3.0 needs -funit-at-a-time for extern inline functions.
> +KBUILD_CFLAGS += $(call cc-option,-funit-at-a-time)

Acked-by: Richard Weinberger <richard@nod.at>

Thanks,
//richard

Re: [PATCH 1/2] um: remove -fno-unit-at-a-time workaround for pre-4.0 GCC

[Masahiro Yamada]

x86 maintainers,


Ping.



On Tue, Nov 13, 2018 at 6:48 PM Richard Weinberger <richard@nod.at> wrote:
>
> Am Montag, 12. November 2018, 03:35:19 CET schrieb Masahiro Yamada:
> > Commit cafa0010cd51 ("Raise the minimum required gcc version to 4.6")
> > bumped the minimum GCC version to 4.6 for all architectures.
> >
> > '$(call cc-option,-fno-unit-at-a-time)' is now dead code since
> > '$(cc-version) -lt 0400' is always false.
> >
> > Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
> > ---
> >
> >  arch/x86/Makefile.um | 8 ++------
> >  1 file changed, 2 insertions(+), 6 deletions(-)
> >
> > diff --git a/arch/x86/Makefile.um b/arch/x86/Makefile.um
> > index 91085a0..577976b 100644
> > --- a/arch/x86/Makefile.um
> > +++ b/arch/x86/Makefile.um
> > @@ -26,12 +26,8 @@ cflags-y += $(call cc-option,-mpreferred-stack-boundary=2)
> >  # an unresolved reference.
> >  cflags-y += -ffreestanding
> >
> > -# Disable unit-at-a-time mode on pre-gcc-4.0 compilers, it makes gcc use
> > -# a lot more stack due to the lack of sharing of stacklots.  Also, gcc
> > -# 4.3.0 needs -funit-at-a-time for extern inline functions.
> > -KBUILD_CFLAGS += $(shell if [ $(cc-version) -lt 0400 ] ; then \
> > -                     echo $(call cc-option,-fno-unit-at-a-time); \
> > -                     else echo $(call cc-option,-funit-at-a-time); fi ;)
> > +# gcc 4.3.0 needs -funit-at-a-time for extern inline functions.
> > +KBUILD_CFLAGS += $(call cc-option,-funit-at-a-time)
>
> Acked-by: Richard Weinberger <richard@nod.at>
>
> Thanks,
> //richard
>
>
>


-- 
Best Regards
Masahiro Yamada

Re: [PATCH 2/2] x86, powerpc: remove -funit-at-a-time compiler option entirely

[Masahiro Yamada]

x86 maintainers,

Ping.



On Mon, Nov 12, 2018 at 8:23 PM Michael Ellerman <mpe@ellerman.id.au> wrote:
>
> Masahiro Yamada <yamada.masahiro@socionext.com> writes:
>
> > GCC 4.6 manual says:
> >
> > -funit-at-a-time
> >   This option is left for compatibility reasons. -funit-at-a-time has
> >   no effect, while -fno-unit-at-a-time implies -fno-toplevel-reorder
> >   and -fno-section-anchors.
> >   Enabled by default.
> >
> > Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
> > ---
> >
> >  arch/powerpc/Makefile | 4 ----
> >  arch/x86/Makefile     | 4 ----
> >  arch/x86/Makefile.um  | 5 -----
> >  3 files changed, 13 deletions(-)
> >
> > diff --git a/arch/powerpc/Makefile b/arch/powerpc/Makefile
> > index 8a2ce14..854199c 100644
> > --- a/arch/powerpc/Makefile
> > +++ b/arch/powerpc/Makefile
> > @@ -228,10 +228,6 @@ KBUILD_CFLAGS += $(call cc-option,-mno-vsx)
> >  KBUILD_CFLAGS += $(call cc-option,-mno-spe)
> >  KBUILD_CFLAGS += $(call cc-option,-mspe=no)
> >
> > -# Enable unit-at-a-time mode when possible. It shrinks the
> > -# kernel considerably.
> > -KBUILD_CFLAGS += $(call cc-option,-funit-at-a-time)
> > -
>
> Thanks for cleaning it up.
>
> Acked-by: Michael Ellerman <mpe@ellerman.id.au>
>
> cheers



-- 
Best Regards
Masahiro Yamada

Re: [PATCH 1/2] um: remove -fno-unit-at-a-time workaround for pre-4.0 GCC

[Richard Weinberger]

Am Samstag, 8. Dezember 2018, 07:35:47 CET schrieb Masahiro Yamada:
> x86 maintainers,
> 
> 
> Ping.

I thought you carry this via your kbuild tree.
That said, I can merge it also via the um tree.
x86 is of course also fine. :-)

> 
> 
> On Tue, Nov 13, 2018 at 6:48 PM Richard Weinberger <richard@nod.at> wrote:
> >
> > Am Montag, 12. November 2018, 03:35:19 CET schrieb Masahiro Yamada:
> > > Commit cafa0010cd51 ("Raise the minimum required gcc version to 4.6")
> > > bumped the minimum GCC version to 4.6 for all architectures.
> > >
> > > '$(call cc-option,-fno-unit-at-a-time)' is now dead code since
> > > '$(cc-version) -lt 0400' is always false.
> > >
> > > Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
> > > ---
> > >
> > >  arch/x86/Makefile.um | 8 ++------
> > >  1 file changed, 2 insertions(+), 6 deletions(-)
> > >
> > > diff --git a/arch/x86/Makefile.um b/arch/x86/Makefile.um
> > > index 91085a0..577976b 100644
> > > --- a/arch/x86/Makefile.um
> > > +++ b/arch/x86/Makefile.um
> > > @@ -26,12 +26,8 @@ cflags-y += $(call cc-option,-mpreferred-stack-boundary=2)
> > >  # an unresolved reference.
> > >  cflags-y += -ffreestanding
> > >
> > > -# Disable unit-at-a-time mode on pre-gcc-4.0 compilers, it makes gcc use
> > > -# a lot more stack due to the lack of sharing of stacklots.  Also, gcc
> > > -# 4.3.0 needs -funit-at-a-time for extern inline functions.
> > > -KBUILD_CFLAGS += $(shell if [ $(cc-version) -lt 0400 ] ; then \
> > > -                     echo $(call cc-option,-fno-unit-at-a-time); \
> > > -                     else echo $(call cc-option,-funit-at-a-time); fi ;)
> > > +# gcc 4.3.0 needs -funit-at-a-time for extern inline functions.
> > > +KBUILD_CFLAGS += $(call cc-option,-funit-at-a-time)
> >
> > Acked-by: Richard Weinberger <richard@nod.at>

Thanks,
//richard

Re: [PATCH 2/2] x86, powerpc: remove -funit-at-a-time compiler option entirely

[Borislav Petkov]

On Sat, Dec 08, 2018 at 03:36:52PM +0900, Masahiro Yamada wrote:
> x86 maintainers,
> 
> Ping.

You got the required ACKs. If you want me to carry this one and the
UML one through the tip tree, lemme know. Or you can do what Richard
suggested. Your call.

Thx.

-- 
Regards/Gruss,
    Boris.

Good mailing practices for 400: avoid top-posting and trim the reply.

Re: [PATCH 2/2] x86, powerpc: remove -funit-at-a-time compiler option entirely

[Masahiro Yamada]

Hi Borislav,


On Sat, Dec 8, 2018 at 8:34 PM Borislav Petkov <bp@alien8.de> wrote:
>
> On Sat, Dec 08, 2018 at 03:36:52PM +0900, Masahiro Yamada wrote:
> > x86 maintainers,
> >
> > Ping.
>
> You got the required ACKs. If you want me to carry this one and the
> UML one through the tip tree, lemme know. Or you can do what Richard
> suggested. Your call.


Thank you for your help.
I expect both applied through the tip bot.

Thanks.





> Thx.
>
> --
> Regards/Gruss,
>     Boris.
>
> Good mailing practices for 400: avoid top-posting and trim the reply.



-- 
Best Regards
Masahiro Yamada

Re: [PATCH 1/2] um: remove -fno-unit-at-a-time workaround for pre-4.0 GCC

[Masahiro Yamada]

Hi Richard,

On Sat, Dec 8, 2018 at 5:55 PM Richard Weinberger <richard@nod.at> wrote:
>
> Am Samstag, 8. Dezember 2018, 07:35:47 CET schrieb Masahiro Yamada:
> > x86 maintainers,
> >
> >
> > Ping.
>
> I thought you carry this via your kbuild tree.
> That said, I can merge it also via the um tree.
> x86 is of course also fine. :-)


The second patch also touches x86 Makefiles.

So, I think both should be applied to x86 tree.

Thanks.




> >
> >
> > On Tue, Nov 13, 2018 at 6:48 PM Richard Weinberger <richard@nod.at> wrote:
> > >
> > > Am Montag, 12. November 2018, 03:35:19 CET schrieb Masahiro Yamada:
> > > > Commit cafa0010cd51 ("Raise the minimum required gcc version to 4.6")
> > > > bumped the minimum GCC version to 4.6 for all architectures.
> > > >
> > > > '$(call cc-option,-fno-unit-at-a-time)' is now dead code since
> > > > '$(cc-version) -lt 0400' is always false.
> > > >
> > > > Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
> > > > ---
> > > >
> > > >  arch/x86/Makefile.um | 8 ++------
> > > >  1 file changed, 2 insertions(+), 6 deletions(-)
> > > >
> > > > diff --git a/arch/x86/Makefile.um b/arch/x86/Makefile.um
> > > > index 91085a0..577976b 100644
> > > > --- a/arch/x86/Makefile.um
> > > > +++ b/arch/x86/Makefile.um
> > > > @@ -26,12 +26,8 @@ cflags-y += $(call cc-option,-mpreferred-stack-boundary=2)
> > > >  # an unresolved reference.
> > > >  cflags-y += -ffreestanding
> > > >
> > > > -# Disable unit-at-a-time mode on pre-gcc-4.0 compilers, it makes gcc use
> > > > -# a lot more stack due to the lack of sharing of stacklots.  Also, gcc
> > > > -# 4.3.0 needs -funit-at-a-time for extern inline functions.
> > > > -KBUILD_CFLAGS += $(shell if [ $(cc-version) -lt 0400 ] ; then \
> > > > -                     echo $(call cc-option,-fno-unit-at-a-time); \
> > > > -                     else echo $(call cc-option,-funit-at-a-time); fi ;)
> > > > +# gcc 4.3.0 needs -funit-at-a-time for extern inline functions.
> > > > +KBUILD_CFLAGS += $(call cc-option,-funit-at-a-time)
> > >
> > > Acked-by: Richard Weinberger <richard@nod.at>
>
> Thanks,
> //richard
>
>


-- 
Best Regards
Masahiro Yamada