On Thu, Nov 24, 2022 at 5:37 AM Nicolas Schier <[email protected]> wrote:
>
> On Thu 24 Nov 2022 00:18:25 GMT, Masahiro Yamada wrote:
> > Converting clang-min-version is straightforward because the versions
> > are always 6-digit.
> >
> > gcc-min-version is somewhat tricky because the minimal GCC version
> > is GCC 5.2; prepend '0' to the version that is less than 10 so that
> > test-ge is always passed with 6-digit versions.
> >
> > Signed-off-by: Masahiro Yamada <[email protected]>
> > ---
> >
> > Changes in v2:
> > - Covert gcc-min-version in a different way
> >
> > scripts/Makefile.compiler | 8 ++++++--
> > 1 file changed, 6 insertions(+), 2 deletions(-)
> >
> > diff --git a/scripts/Makefile.compiler b/scripts/Makefile.compiler
> > index 20d353dcabfb..cd75f81e88ef 100644
> > --- a/scripts/Makefile.compiler
> > +++ b/scripts/Makefile.compiler
> > @@ -63,11 +63,15 @@ cc-disable-warning = $(call try-run,\
> >
> > # gcc-min-version
> > # Usage: cflags-$(call gcc-min-version, 70100) += -foo
> > -gcc-min-version = $(shell [ $(CONFIG_GCC_VERSION)0 -ge $(1)0 ] && echo y)
> > +
> > +# Preprend 0 to the version that is less than 10 so test-ge works.
> > +gcc-min-version = $(call test-ge, \
> > + $(or $(filter 1%, $(CONFIG_GCC_VERSION)), 0$(CONFIG_GCC_VERSION)), \
> > + $(or $(filter 1%, $1), 0$(strip $1)))
>
> Hm, this silently expects a gcc version < 20, which we should expect in
> about seven-eight years [1]. I am thinking about the possibility of
> silent (but unlikely) breaks when someone in far future uses a gcc 20
> against a kernel with this line. Probably we should not care about
> that today, yet, right?

Yeah, I thought of it.

It depends on which of the following two will happen first.

(a) We raise the min gcc version to 10.0.0 and remove this hack
(b) GCC 20 is released

I am guessing (a) will occur first, so we do not need to care about (b).

If (b) happens first, we will need to add "2%".
It means that the window of supported GCC versions will get larger than 10.
Presumably, we do not want to support such a wide range of compiler
versions.

GCC 5.1 was released in 2015.
So, the current window of GCC versions is 7 years.
I hope it will not get even larger...

--
Best Regards
Masahiro Yamada

2022-11-23 21:54:38

On Thu 24 Nov 2022 06:52:06 GMT, Masahiro Yamada wrote:
> On Thu, Nov 24, 2022 at 6:02 AM Nicolas Schier <[email protected]> wrote:
> >
> > On Thu 24 Nov 2022 00:18:26 GMT, Masahiro Yamada wrote:
> > > Since GMU Make 4.2, $(file ...) supports the read operater '<', which is
> > > useful to read a file without forking any process. No warning is shown even
> > > if the input file is missing.
> > >
> > > For older Make versions, it falls back to the cat command.
> > >
> > > Signed-off-by: Masahiro Yamada <[email protected]>
> > > ---
> > >
> > > (no changes since v1)
> > >
> > > Makefile | 2 +-
> > > scripts/Kbuild.include | 12 ++++++++++++
> > > scripts/Makefile.modfinal | 2 +-
> > > scripts/Makefile.modinst | 2 +-
> > > 4 files changed, 15 insertions(+), 3 deletions(-)
> > >
> > > diff --git a/Makefile b/Makefile
> > > index eb80332f7b51..60ce9dcafc72 100644
> > > --- a/Makefile
> > > +++ b/Makefile
> > > @@ -369,7 +369,7 @@ else # !mixed-build
> > > include $(srctree)/scripts/Kbuild.include
> > >
> > > # Read KERNELRELEASE from include/config/kernel.release (if it exists)
> > > -KERNELRELEASE = $(shell cat include/config/kernel.release 2> /dev/null)
> > > +KERNELRELEASE = $(call read-file, include/config/kernel.release)
> > > KERNELVERSION = $(VERSION)$(if $(PATCHLEVEL),.$(PATCHLEVEL)$(if $(SUBLEVEL),.$(SUBLEVEL)))$(EXTRAVERSION)
> > > export VERSION PATCHLEVEL SUBLEVEL KERNELRELEASE KERNELVERSION
> > >
> > > diff --git a/scripts/Kbuild.include b/scripts/Kbuild.include
> > > index 9996f34327cb..722846c23264 100644
> > > --- a/scripts/Kbuild.include
> > > +++ b/scripts/Kbuild.include
> > > @@ -10,6 +10,10 @@ empty :=
> > > space := $(empty) $(empty)
> > > space_escape := _-_SPACE_-_
> > > pound := \#
> > > +define newline
> > > +
> > > +
> > > +endef
> > >
> > > ###
> > > # Comparison macros.
> > > @@ -55,6 +59,14 @@ stringify = $(squote)$(quote)$1$(quote)$(squote)
> > > kbuild-dir = $(if $(filter /%,$(src)),$(src),$(srctree)/$(src))
> > > kbuild-file = $(or $(wildcard $(kbuild-dir)/Kbuild),$(kbuild-dir)/Makefile)
> > >
> > > +###
> > > +# Read a file, replacing newlines with spaces
> > > +ifeq ($(call test-ge, $(MAKE_VERSION), 4.2),y)
> > > +read-file = $(subst $(newline),$(space),$(file < $1))
> > > +else
> > > +read-file = $(shell cat $1 2>/dev/null)
> > > +endif
> > > +
> >
> > I like the implementation of read-file, but I am afraid that the
> > MAKE_VERSION comparison breaks all make versions w/ a minor version
> > number: 3.99.9x, 4.2.x, 4.3.x.
>
>
> I think these should work correctly
> unless I missed something terribly.
>
>
> In the ASCII-sorting, they are sorted like this:
>
> 3.99.9x 4.2 4.2.x 4.3.x
>
>
>
>
>
>
> The bad scenarios I came up with is GNU Make 4.10
> and GNU Make 10.0 because $(sort ) will sort
>
> 10 4.10 4.2
>
>
>
>
> GNU Make 4.3 was released in Jan 2020
> GNU Make 4.4 was released in Oct 2022
>
>
>
> If the current release pace continues,
> we will have about 10 years until GNU Make hits 4.10
>
> Until then, we can remove this ifeq.
>

yes, you're right. I should have checked my assumption before
bothering you with it.

Reviewed-by: Nicolas Schier <[email protected]>

>
>
> --
> Best Regards
> Masahiro Yamada

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2022-11-24 07:24:27

On Thu, Nov 24, 2022 at 12:19 AM Masahiro Yamada <[email protected]> wrote:
>
> Because GNU Make is only able to handle strings, it is very hard to
> perform arighmetic in Makefiles.

I terribly missed that GNU Make 4.4
introduced the $(intcmp ...) function.

https://www.gnu.org/software/make/manual/make.html#Conditional-Functions

I am thinking if we can do better by using it.

>
> When we compare two integers, we invokes shell. One example is in the
> top Makefile:
>
> ifeq ($(shell test $(CONFIG_LLD_VERSION) -lt 130000; echo $$?),0)
>
> This is more expensive than using built-in functions since it forks a
> process.
>
> If we know the two have the same number of digits, we can do better.
>
> This commit adds four macros, test-le, test-ge, test-lt, test-gt.
>
> $(call test-lt, A, B) is evaluated to 'y' if A is less than B, or
> empty otherwise. This will replace $(call shell test A -lt B).
>
> Again, the limitation is that A and B must have the same number of
> digits because these macros are based on $(sort ) function.
>
> $(call test-lt, 1, 9) --> y (Works!)
> $(call test-lt, 10, 9) --> y (Not work...)
>
> To make the latter work, you need to add '0' prefix to align the number
> of digits:
>
> $(call test-lt, 10, 09) --> empty (Works!)
>
> Actually, we can live with this limitation in many places. As for the
> example above, we know $(CONFIG_LLD_VERSION) is 6-digits because the
> minimal supported version of LLVM is 11.0.0.
>
> So, the shell invocation can be replaced with more efficient code:
>
> ifeq ($(call test-lt, $(CONFIG_LLD_VERSION), 130000),y)
>
> Of course, this assumption will break when LLVM 100 is released, but it
> will be far in the future.
>
> Signed-off-by: Masahiro Yamada <[email protected]>
> ---
>
> (no changes since v1)
>
> Makefile | 2 +-
> arch/riscv/Makefile | 2 +-
> arch/x86/Makefile | 2 +-
> scripts/Kbuild.include | 10 ++++++++++
> 4 files changed, 13 insertions(+), 3 deletions(-)
>
> diff --git a/Makefile b/Makefile
> index 6f846b1f2618..eb80332f7b51 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -986,7 +986,7 @@ KBUILD_LDFLAGS += -mllvm -import-instr-limit=5
> # Check for frame size exceeding threshold during prolog/epilog insertion
> # when using lld < 13.0.0.
> ifneq ($(CONFIG_FRAME_WARN),0)
> -ifeq ($(shell test $(CONFIG_LLD_VERSION) -lt 130000; echo $$?),0)
> +ifeq ($(call test-lt, $(CONFIG_LLD_VERSION), 130000),y)
> KBUILD_LDFLAGS += -plugin-opt=-warn-stack-size=$(CONFIG_FRAME_WARN)
> endif
> endif
> diff --git a/arch/riscv/Makefile b/arch/riscv/Makefile
> index 0d13b597cb55..faf2c2177094 100644
> --- a/arch/riscv/Makefile
> +++ b/arch/riscv/Makefile
> @@ -37,7 +37,7 @@ else
> endif
>
> ifeq ($(CONFIG_LD_IS_LLD),y)
> -ifeq ($(shell test $(CONFIG_LLD_VERSION) -lt 150000; echo $$?),0)
> +ifeq ($(call test-lt, $(CONFIG_LLD_VERSION), 150000),y)
> KBUILD_CFLAGS += -mno-relax
> KBUILD_AFLAGS += -mno-relax
> ifndef CONFIG_AS_IS_LLVM
> diff --git a/arch/x86/Makefile b/arch/x86/Makefile
> index 415a5d138de4..e72c7a49cd59 100644
> --- a/arch/x86/Makefile
> +++ b/arch/x86/Makefile
> @@ -211,7 +211,7 @@ endif
> KBUILD_LDFLAGS += -m elf_$(UTS_MACHINE)
>
> ifdef CONFIG_LTO_CLANG
> -ifeq ($(shell test $(CONFIG_LLD_VERSION) -lt 130000; echo $$?),0)
> +ifeq ($(call test-lt, $(CONFIG_LLD_VERSION), 130000),y)
> KBUILD_LDFLAGS += -plugin-opt=-stack-alignment=$(if $(CONFIG_X86_32),4,8)
> endif
> endif
> diff --git a/scripts/Kbuild.include b/scripts/Kbuild.include
> index cbe28744637b..9996f34327cb 100644
> --- a/scripts/Kbuild.include
> +++ b/scripts/Kbuild.include
> @@ -11,6 +11,16 @@ space := $(empty) $(empty)
> space_escape := _-_SPACE_-_
> pound := \#
>
> +###
> +# Comparison macros.
> +# Usage: $(call test-le, A, B)
> +# works like shell's "test A -le B", but A and B must have the same number of
> +# digits since it is just ASCII sort.
> +test-le = $(if $(filter $1, $(firstword $(sort $1 $2))),y)
> +test-ge = $(call test-le, $2, $1)
> +test-lt = $(if $(filter-out $2, $(firstword $(sort $1 $2))),y)
> +test-gt = $(call test-lt, $2, $1)
> +
> ###
> # Name of target with a '.' as filename prefix. foo/bar.o => foo/.bar.o
> dot-target = $(dir $@).$(notdir $@)
> --
> 2.34.1
>

--
Best Regards
Masahiro Yamada