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BACKPORT: Makefile: infer --target from ARCH for CC=clang

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We get constant feedback that the command line invocation of make is too
long when compiling with LLVM. CROSS_COMPILE is helpful when a toolchain
has a prefix of the target triple, or is an absolute path outside of
$PATH.

Since a Clang binary is generally multi-targeted, we can infer a given
target from SRCARCH/ARCH.  If CROSS_COMPILE is not set, simply set
--target= for CLANG_FLAGS, KBUILD_CFLAGS, and KBUILD_AFLAGS based on
$SRCARCH.

Previously, we'd cross compile via:
$ ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- make LLVM=1 LLVM_IAS=1
Now:
$ ARCH=arm64 make LLVM=1 LLVM_IAS=1

For native builds (not involving cross compilation) we now explicitly
specify a target triple rather than rely on the implicit host triple.

Link: https://github.com/ClangBuiltLinux/linux/issues/1399
Suggested-by: Arnd Bergmann <arnd@kernel.org>
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Suggested-by: Masahiro Yamada <masahiroy@kernel.org>
Suggested-by: Nathan Chancellor <nathan@kernel.org>
Acked-by: Arnd Bergmann <arnd@kernel.org>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Acked-by: Miguel Ojeda <ojeda@kernel.org>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Bug: 209655537
(cherry picked from commit 231ad7f409f16b9f9505f69e058dff488a7e6bde)
Change-Id: I6f61a4937e6af22deda66eeaac6c667c889dc683
This commit is contained in:
Nick Desaulniers 2021-08-02 11:39:09 -07:00 committed by Michael Bestas
parent 980f272ee9
commit b3d8ffe52f
No known key found for this signature in database
GPG Key ID: CC95044519BE6669
1 changed files with 23 additions and 2 deletions
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25
Makefile
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@ -560,9 +560,30 @@ endif
CC_VERSION_TEXT = $(shell $(CC) --version 2>/dev/null | head -n 1 | sed 's/\#//g') CC_VERSION_TEXT = $(shell $(CC) --version 2>/dev/null | head -n 1 | sed 's/\#//g')
ifneq ($(findstring clang,$(CC_VERSION_TEXT)),) ifneq ($(findstring clang,$(CC_VERSION_TEXT)),)
ifneq ($(CROSS_COMPILE),) # Individual arch/{arch}/Makefiles should use -EL/-EB to set intended
# endianness and -m32/-m64 to set word size based on Kconfigs instead of
# relying on the target triple.
CLANG_TARGET_FLAGS_arm := arm-linux-gnueabi
CLANG_TARGET_FLAGS_arm64 := aarch64-linux-gnu
CLANG_TARGET_FLAGS_hexagon := hexagon-linux-musl
CLANG_TARGET_FLAGS_m68k := m68k-linux-gnu
CLANG_TARGET_FLAGS_mips := mipsel-linux-gnu
CLANG_TARGET_FLAGS_powerpc := powerpc64le-linux-gnu
CLANG_TARGET_FLAGS_riscv := riscv64-linux-gnu
CLANG_TARGET_FLAGS_s390 := s390x-linux-gnu
CLANG_TARGET_FLAGS_x86 := x86_64-linux-gnu
CLANG_TARGET_FLAGS := $(CLANG_TARGET_FLAGS_$(SRCARCH))
ifeq ($(CROSS_COMPILE),)
ifeq ($(CLANG_TARGET_FLAGS),)
$(error Specify CROSS_COMPILE or add '--target=' option to Makefile)
else
CLANG_FLAGS += --target=$(CLANG_TARGET_FLAGS)
endif # CLANG_TARGET_FLAGS
else
CLANG_FLAGS += --target=$(notdir $(CROSS_COMPILE:%-=%)) CLANG_FLAGS += --target=$(notdir $(CROSS_COMPILE:%-=%))
endif endif # CROSS_COMPILE
ifneq ($(LLVM_IAS),1) ifneq ($(LLVM_IAS),1)
CLANG_FLAGS += -no-integrated-as CLANG_FLAGS += -no-integrated-as
GCC_TOOLCHAIN_DIR := $(dir $(shell which $(CROSS_COMPILE)elfedit)) GCC_TOOLCHAIN_DIR := $(dir $(shell which $(CROSS_COMPILE)elfedit))