[PATCH v2 1/2] kbuild: replace cc-name test with CONFIG_CC_IS_CLANG

[PATCH v2 1/2] kbuild: replace cc-name test with CONFIG_CC_IS_CLANG

[Masahiro Yamada]

Evaluating cc-name invokes the compiler every time even when you are
not compiling anything, like 'make help'. This is not efficient.

The compiler type has been already detected in the Kconfig stage.
Use CONFIG_CC_IS_CLANG, instead.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc)
---

Changes in v2:
 - Use ifdef/ifndef insteaed of ifeq/ifneq

 Makefile                   | 2 +-
 arch/mips/Makefile         | 2 +-
 arch/mips/vdso/Makefile    | 2 +-
 arch/powerpc/Makefile      | 4 ++--
 scripts/Makefile.extrawarn | 2 +-
 5 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/Makefile b/Makefile
index 0a42d06..1c0696d 100644
--- a/Makefile
+++ b/Makefile
@@ -707,7 +707,7 @@ stackp-flags-$(CONFIG_STACKPROTECTOR_STRONG)      := -fstack-protector-strong
 
 KBUILD_CFLAGS += $(stackp-flags-y)
 
-ifeq ($(cc-name),clang)
+ifdef CONFIG_CC_IS_CLANG
 KBUILD_CPPFLAGS += $(call cc-option,-Qunused-arguments,)
 KBUILD_CFLAGS += $(call cc-disable-warning, format-invalid-specifier)
 KBUILD_CFLAGS += $(call cc-disable-warning, gnu)
diff --git a/arch/mips/Makefile b/arch/mips/Makefile
index 15a84cf..6841049 100644
--- a/arch/mips/Makefile
+++ b/arch/mips/Makefile
@@ -128,7 +128,7 @@ cflags-y += -ffreestanding
 # clang's output will be based upon the build machine. So for clang we simply
 # unconditionally specify -EB or -EL as appropriate.
 #
-ifeq ($(cc-name),clang)
+ifdef CONFIG_CC_IS_CLANG
 cflags-$(CONFIG_CPU_BIG_ENDIAN)		+= -EB
 cflags-$(CONFIG_CPU_LITTLE_ENDIAN)	+= -EL
 else
diff --git a/arch/mips/vdso/Makefile b/arch/mips/vdso/Makefile
index 34605ca..58a0315 100644
--- a/arch/mips/vdso/Makefile
+++ b/arch/mips/vdso/Makefile
@@ -10,7 +10,7 @@ ccflags-vdso := \
 	$(filter -march=%,$(KBUILD_CFLAGS)) \
 	-D__VDSO__
 
-ifeq ($(cc-name),clang)
+ifdef CONFIG_CC_IS_CLANG
 ccflags-vdso += $(filter --target=%,$(KBUILD_CFLAGS))
 endif
 
diff --git a/arch/powerpc/Makefile b/arch/powerpc/Makefile
index 17be664..8a2ce14 100644
--- a/arch/powerpc/Makefile
+++ b/arch/powerpc/Makefile
@@ -96,7 +96,7 @@ aflags-$(CONFIG_CPU_BIG_ENDIAN)		+= $(call cc-option,-mabi=elfv1)
 aflags-$(CONFIG_CPU_LITTLE_ENDIAN)	+= -mabi=elfv2
 endif
 
-ifneq ($(cc-name),clang)
+ifndef CONFIG_CC_IS_CLANG
   cflags-$(CONFIG_CPU_LITTLE_ENDIAN)	+= -mno-strict-align
 endif
 
@@ -175,7 +175,7 @@ endif
 # Work around gcc code-gen bugs with -pg / -fno-omit-frame-pointer in gcc <= 4.8
 # https://gcc.gnu.org/bugzilla/show_bug.cgi?id=44199
 # https://gcc.gnu.org/bugzilla/show_bug.cgi?id=52828
-ifneq ($(cc-name),clang)
+ifndef CONFIG_CC_IS_CLANG
 CC_FLAGS_FTRACE	+= $(call cc-ifversion, -lt, 0409, -mno-sched-epilog)
 endif
 endif
diff --git a/scripts/Makefile.extrawarn b/scripts/Makefile.extrawarn
index 24b2fb1..800a10f 100644
--- a/scripts/Makefile.extrawarn
+++ b/scripts/Makefile.extrawarn
@@ -64,7 +64,7 @@ endif
 KBUILD_CFLAGS += $(warning)
 else
 
-ifeq ($(cc-name),clang)
+ifdef CONFIG_CC_IS_CLANG
 KBUILD_CFLAGS += $(call cc-disable-warning, initializer-overrides)
 KBUILD_CFLAGS += $(call cc-disable-warning, unused-value)
 KBUILD_CFLAGS += $(call cc-disable-warning, format)
-- 
2.7.4

[PATCH v2 2/2] kbuild: remove cc-name variable

[Masahiro Yamada]

There is one more user of $(cc-name) in the top Makefile. It is supposed
to detect Clang before invoking Kconfig, so it should still be there
in the $(shell ...) form. All the other users of $(cc-name) have been
replaced with $(CONFIG_CC_IS_CLANG). Hence, scripts/Kbuild.include does
not need to define cc-name any more.

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

Changes in v2: None

 Makefile               | 2 +-
 scripts/Kbuild.include | 4 ----
 2 files changed, 1 insertion(+), 5 deletions(-)

diff --git a/Makefile b/Makefile
index 1c0696d..25b1518 100644
--- a/Makefile
+++ b/Makefile
@@ -485,7 +485,7 @@ ifneq ($(KBUILD_SRC),)
 	$(Q)$(CONFIG_SHELL) $(srctree)/scripts/mkmakefile $(srctree)
 endif
 
-ifeq ($(cc-name),clang)
+ifneq ($(shell $(CC) --version 2>&1 | head -n 1 | grep clang),)
 ifneq ($(CROSS_COMPILE),)
 CLANG_TARGET	:= --target=$(notdir $(CROSS_COMPILE:%-=%))
 GCC_TOOLCHAIN_DIR := $(dir $(shell which $(LD)))
diff --git a/scripts/Kbuild.include b/scripts/Kbuild.include
index ca21a35..51703ae 100644
--- a/scripts/Kbuild.include
+++ b/scripts/Kbuild.include
@@ -140,10 +140,6 @@ cc-option-yn = $(call try-run,\
 cc-disable-warning = $(call try-run,\
 	$(CC) -Werror $(KBUILD_CPPFLAGS) $(CC_OPTION_CFLAGS) -W$(strip $(1)) -c -x c /dev/null -o "$$TMP",-Wno-$(strip $(1)))
 
-# cc-name
-# Expands to either gcc or clang
-cc-name = $(shell $(CC) -v 2>&1 | grep -q "clang version" && echo clang || echo gcc)
-
 # cc-version
 cc-version = $(shell $(CONFIG_SHELL) $(srctree)/scripts/gcc-version.sh $(CC))
 
-- 
2.7.4

Re: [PATCH v2 1/2] kbuild: replace cc-name test with CONFIG_CC_IS_CLANG

[Paul Burton]

Hi Masahiro,

On Tue, Oct 30, 2018 at 10:26:33PM +0900, Masahiro Yamada wrote:
> Evaluating cc-name invokes the compiler every time even when you are
> not compiling anything, like 'make help'. This is not efficient.
> 
> The compiler type has been already detected in the Kconfig stage.
> Use CONFIG_CC_IS_CLANG, instead.
> 
> Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
> Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc)

Looks good to me:

    Acked-by: Paul Burton <paul.burton@mips.com> (MIPS)

Thanks,
    Paul

Re: [PATCH v2 1/2] kbuild: replace cc-name test with CONFIG_CC_IS_CLANG

[Joel Stanley]

On Tue, 30 Oct 2018 at 23:58, Masahiro Yamada
<yamada.masahiro@socionext.com> wrote:
>
> Evaluating cc-name invokes the compiler every time even when you are
> not compiling anything, like 'make help'. This is not efficient.
>
> The compiler type has been already detected in the Kconfig stage.
> Use CONFIG_CC_IS_CLANG, instead.

Thanks, I didn't know about this.

>
> Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
> Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc)

Acked-by: Joel Stanley <joel@jms.id.au>

Cheers,

Joel