[PATCH v2 3/5] Makefile.compiler: replace cc-ifversion with compiler-specific macros
Masahiro Yamada
masahiroy at kernel.org
Mon Sep 5 06:44:01 UTC 2022
On Thu, Sep 1, 2022 at 3:44 AM Nick Desaulniers <ndesaulniers at google.com> wrote:
>
> cc-ifversion is GCC specific. Replace it with compiler specific
> variants. Update the users of cc-ifversion to use these new macros.
> Provide a helper for checking compiler versions for GCC and Clang
> simultaneously, that will be used in a follow up patch.
>
> Cc: Jonathan Corbet <corbet at lwn.net>
> Cc: linux-doc at vger.kernel.org
> Cc: amd-gfx at lists.freedesktop.org
> Cc: dri-devel at lists.freedesktop.org
> Link: https://github.com/ClangBuiltLinux/linux/issues/350
> Link: https://lore.kernel.org/llvm/CAGG=3QWSAUakO42kubrCap8fp-gm1ERJJAYXTnP1iHk_wrH=BQ@mail.gmail.com/
> Suggested-by: Bill Wendling <morbo at google.com>
> Signed-off-by: Nick Desaulniers <ndesaulniers at google.com>
> ---
> Changes v1 -> v2:
> * New patch.
>
> Documentation/kbuild/makefiles.rst | 44 +++++++++++++++------
> Makefile | 4 +-
> drivers/gpu/drm/amd/display/dc/dml/Makefile | 12 ++----
> scripts/Makefile.compiler | 15 +++++--
> 4 files changed, 49 insertions(+), 26 deletions(-)
>
> diff --git a/Documentation/kbuild/makefiles.rst b/Documentation/kbuild/makefiles.rst
> index 11a296e52d68..e46f5b45c422 100644
> --- a/Documentation/kbuild/makefiles.rst
> +++ b/Documentation/kbuild/makefiles.rst
> @@ -682,22 +682,42 @@ more details, with real examples.
> In the above example, -Wno-unused-but-set-variable will be added to
> KBUILD_CFLAGS only if gcc really accepts it.
>
> - cc-ifversion
> - cc-ifversion tests the version of $(CC) and equals the fourth parameter
> - if version expression is true, or the fifth (if given) if the version
> - expression is false.
> + gcc-min-version
> + gcc-min-version tests if the value of $(CONFIG_GCC_VERSION) is greater than
> + or equal to the provided value and evaluates to y if so.
>
> Example::
>
> - #fs/reiserfs/Makefile
> - ccflags-y := $(call cc-ifversion, -lt, 0402, -O1)
> + cflags-$(call gcc-min-version, 70100) := -foo
>
> - In this example, ccflags-y will be assigned the value -O1 if the
> - $(CC) version is less than 4.2.
> - cc-ifversion takes all the shell operators:
> - -eq, -ne, -lt, -le, -gt, and -ge
> - The third parameter may be a text as in this example, but it may also
> - be an expanded variable or a macro.
> + In this example, cflags-y will be assigned the value -foo if $(CC) is gcc and
> + $(CONFIG_GCC_VERSION) is >= 7.1.
> +
> + clang-min-version
> + clang-min-version tests if the value of $(CONFIG_CLANG_VERSION) is greater
> + than or equal to the provided value and evaluates to y if so.
> +
> + Example::
> +
> + cflags-$(call clang-min-version, 110000) := -foo
> +
> + In this example, cflags-y will be assigned the value -foo if $(CC) is clang
> + and $(CONFIG_CLANG_VERSION) is >= 11.0.0.
> +
> + cc-min-version
> + cc-min-version tests if the value of $(CONFIG_GCC_VERSION) is greater
> + than or equal to the first value provided, or if the value of
> + $(CONFIG_CLANG_VERSION) is greater than or equal to the second value
> + provided, and evaluates
> + to y if so.
> +
> + Example::
> +
> + cflags-$(call cc-min-version, 70100, 110000) := -foo
> +
> + In this example, cflags-y will be assigned the value -foo if $(CC) is gcc and
> + $(CONFIG_GCC_VERSION) is >= 7.1, or if $(CC) is clang and
> + $(CONFIG_CLANG_VERSION) is >= 11.0.0.
>
> cc-cross-prefix
> cc-cross-prefix is used to check if there exists a $(CC) in path with
> diff --git a/Makefile b/Makefile
> index 952d354069a4..caa39ecb1136 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -972,7 +972,7 @@ ifdef CONFIG_CC_IS_GCC
> KBUILD_CFLAGS += -Wno-maybe-uninitialized
> endif
>
> -ifdef CONFIG_CC_IS_GCC
> +ifeq ($(call gcc-min-version, 90100),y)
> # The allocators already balk at large sizes, so silence the compiler
> # warnings for bounds checks involving those possible values. While
> # -Wno-alloc-size-larger-than would normally be used here, earlier versions
> @@ -984,7 +984,7 @@ ifdef CONFIG_CC_IS_GCC
> # ignored, continuing to default to PTRDIFF_MAX. So, left with no other
> # choice, we must perform a versioned check to disable this warning.
> # https://lore.kernel.org/lkml/20210824115859.187f272f@canb.auug.org.au
> -KBUILD_CFLAGS += $(call cc-ifversion, -ge, 0901, -Wno-alloc-size-larger-than)
> +KBUILD_CFLAGS += -Wno-alloc-size-larger-than
> endif
>
> # disable invalid "can't wrap" optimizations for signed / pointers
> diff --git a/drivers/gpu/drm/amd/display/dc/dml/Makefile b/drivers/gpu/drm/amd/display/dc/dml/Makefile
> index 86a3b5bfd699..d8ee4743b2e3 100644
> --- a/drivers/gpu/drm/amd/display/dc/dml/Makefile
> +++ b/drivers/gpu/drm/amd/display/dc/dml/Makefile
> @@ -33,20 +33,14 @@ ifdef CONFIG_PPC64
> dml_ccflags := -mhard-float -maltivec
> endif
>
> -ifdef CONFIG_CC_IS_GCC
> -ifeq ($(call cc-ifversion, -lt, 0701, y), y)
> -IS_OLD_GCC = 1
> -endif
> -endif
> -
> ifdef CONFIG_X86
> -ifdef IS_OLD_GCC
> +ifeq ($(call gcc-min-version, 70100),y)
> +dml_ccflags += -msse2
> +else
> # Stack alignment mismatch, proceed with caution.
> # GCC < 7.1 cannot compile code using `double` and -mpreferred-stack-boundary=3
> # (8B stack alignment).
> dml_ccflags += -mpreferred-stack-boundary=4
> -else
> -dml_ccflags += -msse2
> endif
> endif
>
> diff --git a/scripts/Makefile.compiler b/scripts/Makefile.compiler
> index d1739f0d3ce3..13dade724fa3 100644
> --- a/scripts/Makefile.compiler
> +++ b/scripts/Makefile.compiler
> @@ -61,9 +61,18 @@ cc-option-yn = $(call try-run,\
> cc-disable-warning = $(call try-run,\
> $(CC) -Werror $(KBUILD_CPPFLAGS) $(KBUILD_CFLAGS) -W$(strip $(1)) -c -x c /dev/null -o "$$TMP",-Wno-$(strip $(1)))
>
> -# cc-ifversion
> -# Usage: EXTRA_CFLAGS += $(call cc-ifversion, -lt, 0402, -O1)
> -cc-ifversion = $(shell [ $(CONFIG_GCC_VERSION)0 $(1) $(2)000 ] && echo $(3) || echo $(4))
> +# gcc-min-version
> +# Usage: cflags-$(call gcc-min-version, 70100) += -foo
> +gcc-min-version = $(shell [ $(CONFIG_GCC_VERSION) -ge $(1) ] && echo y)
> +
> +# clang-min-version
> +# Usage: cflags-$(call clang-min-version, 110000) += -foo
> +clang-min-version = $(shell [ $(CONFIG_CLANG_VERSION) -ge $(1) ] && echo y)
> +
> +# cc-min-version
> +# Usage: cflags-$(call cc-min-version, 701000, 110000)
> +# ^ GCC ^ Clang
> +cc-min-version = $(filter y, $(call gcc-min-version, $(1)), $(call clang-min-version, $(2)))
A more intuitive and more efficient form would be:
cc-min-version = $(or $(call gcc-min-version, $(1)), $(call
clang-min-version, $(2)))
In your implementation, both gcc-min-version and clang-min-version are
expanded before being passed to $(filter ...).
So the shell is always invoked twice.
$(or A, B) is lazily expanded; A is evaluated first.
If and only if A is empty, B is expanded.
If gcc-min-version is met, the shell invocation in clang-min-version
will be short-cut.
But, I do not find a place where cc-min-version is useful.
Looking at the next patch,
# gcc-11+, clang-14+
ifeq ($(call cc-min-version, 110000, 140000),y)
dwarf-version-y := 5
else
dwarf-version-y := 4
endif
... can be written in a more simpler way:
dwarf-version-y := 4
dwarf-version-$(call gcc-min-version, 110000) := 5
dwarf-version-$(call clang-min-version, 140000) := 5
With $(call cc-min-version, 110000, 140000),
you never know the meaning of 110000, 140000
until you see the definition of this macro.
So, you feel like adding the comment "gcc-11+, clang-14+".
The latter form, the code is self-documenting.
> # ld-option
> # Usage: KBUILD_LDFLAGS += $(call ld-option, -X, -Y)
> --
> 2.37.2.672.g94769d06f0-goog
>
--
Best Regards
Masahiro Yamada
More information about the amd-gfx
mailing list