The LLVM make variable allows a developer to quickly switch between the GNU and LLVM tools. However, it does not handle versioned binaries, such as the ones shipped by Debian, as LLVM=1 just defines the tool variables with the unversioned binaries.
There was some discussion during the review of the patch that introduces LLVM=1 around versioned binaries, ultimately coming to the conclusion that developers can just add the folder that contains the unversioned binaries to their PATH, as Debian's versioned suffixed binaries are really just symlinks to the unversioned binaries in /usr/lib/llvm-#/bin:
$ realpath /usr/bin/clang-14 /usr/lib/llvm-14/bin/clang
$ PATH=/usr/lib/llvm-14/bin:$PATH make ... LLVM=1
However, that can be cumbersome to developers who are constantly testing series with different toolchains and versions. It is simple enough to support these versioned binaries directly in the Kbuild system by allowing the developer to specify the version suffix with LLVM=, which is shorter than the above suggestion:
$ make ... LLVM=-14
It does not change the meaning of LLVM=1 (which will continue to use unversioned binaries) and it does not add too much additional complexity to the existing $(LLVM) code, while allowing developers to quickly test their series with different versions of the whole LLVM suite of tools.
Link: https://lore.kernel.org/r/20200317215515.226917-1-ndesaulniers@google.com/ Link: https://lore.kernel.org/r/20220224151322.072632223@infradead.org/ Suggested-by: Peter Zijlstra peterz@infradead.org Reviewed-by: Kees Cook keescook@chromium.org Reviewed-by: Nick Desaulniers ndesaulniers@google.com Signed-off-by: Nathan Chancellor nathan@kernel.org ---
RFC -> v1: https://lore.kernel.org/r/Yh%2FegU1LZudfrgVy@dev-arch.thelio-3990X/
* Tidy up commit message slightly.
* Add tags.
* Add links to prior discussions for context.
* Add change to tools/testing/selftests/lib.mk.
I would like for this to go through the Kbuild tree, please ack as necessary.
Documentation/kbuild/llvm.rst | 7 +++++++ Makefile | 24 ++++++++++++++---------- tools/scripts/Makefile.include | 20 ++++++++++++-------- tools/testing/selftests/lib.mk | 6 +++++- 4 files changed, 38 insertions(+), 19 deletions(-)
diff --git a/Documentation/kbuild/llvm.rst b/Documentation/kbuild/llvm.rst index d32616891dcf..5805a8473a36 100644 --- a/Documentation/kbuild/llvm.rst +++ b/Documentation/kbuild/llvm.rst @@ -60,6 +60,13 @@ They can be enabled individually. The full list of the parameters: :: OBJCOPY=llvm-objcopy OBJDUMP=llvm-objdump READELF=llvm-readelf \ HOSTCC=clang HOSTCXX=clang++ HOSTAR=llvm-ar HOSTLD=ld.lld
+If your LLVM tools have a suffix and you prefer to test an explicit version rather +than the unsuffixed executables, use ``LLVM=<suffix>``. For example: :: + + make LLVM=-14 + +will use ``clang-14``, ``ld.lld-14``, etc. + The integrated assembler is enabled by default. You can pass ``LLVM_IAS=0`` to disable it.
diff --git a/Makefile b/Makefile index a82095c69fdd..963840c00eae 100644 --- a/Makefile +++ b/Makefile @@ -424,8 +424,12 @@ HOST_LFS_LDFLAGS := $(shell getconf LFS_LDFLAGS 2>/dev/null) HOST_LFS_LIBS := $(shell getconf LFS_LIBS 2>/dev/null)
ifneq ($(LLVM),) -HOSTCC = clang -HOSTCXX = clang++ +ifneq ($(LLVM),1) +LLVM_SFX := $(LLVM) +endif + +HOSTCC = clang$(LLVM_SFX) +HOSTCXX = clang++$(LLVM_SFX) else HOSTCC = gcc HOSTCXX = g++ @@ -444,14 +448,14 @@ KBUILD_HOSTLDLIBS := $(HOST_LFS_LIBS) $(HOSTLDLIBS) # Make variables (CC, etc...) CPP = $(CC) -E ifneq ($(LLVM),) -CC = clang -LD = ld.lld -AR = llvm-ar -NM = llvm-nm -OBJCOPY = llvm-objcopy -OBJDUMP = llvm-objdump -READELF = llvm-readelf -STRIP = llvm-strip +CC = clang$(LLVM_SFX) +LD = ld.lld$(LLVM_SFX) +AR = llvm-ar$(LLVM_SFX) +NM = llvm-nm$(LLVM_SFX) +OBJCOPY = llvm-objcopy$(LLVM_SFX) +OBJDUMP = llvm-objdump$(LLVM_SFX) +READELF = llvm-readelf$(LLVM_SFX) +STRIP = llvm-strip$(LLVM_SFX) else CC = $(CROSS_COMPILE)gcc LD = $(CROSS_COMPILE)ld diff --git a/tools/scripts/Makefile.include b/tools/scripts/Makefile.include index 79d102304470..ab3b2a7dcc94 100644 --- a/tools/scripts/Makefile.include +++ b/tools/scripts/Makefile.include @@ -52,11 +52,15 @@ define allow-override endef
ifneq ($(LLVM),) -$(call allow-override,CC,clang) -$(call allow-override,AR,llvm-ar) -$(call allow-override,LD,ld.lld) -$(call allow-override,CXX,clang++) -$(call allow-override,STRIP,llvm-strip) +ifneq ($(LLVM),1) +LLVM_SFX := $(LLVM) +endif + +$(call allow-override,CC,clang$(LLVM_SFX)) +$(call allow-override,AR,llvm-ar$(LLVM_SFX)) +$(call allow-override,LD,ld.lld$(LLVM_SFX)) +$(call allow-override,CXX,clang++$(LLVM_SFX)) +$(call allow-override,STRIP,llvm-strip$(LLVM_SFX)) else # Allow setting various cross-compile vars or setting CROSS_COMPILE as a prefix. $(call allow-override,CC,$(CROSS_COMPILE)gcc) @@ -69,9 +73,9 @@ endif CC_NO_CLANG := $(shell $(CC) -dM -E -x c /dev/null | grep -Fq "__clang__"; echo $$?)
ifneq ($(LLVM),) -HOSTAR ?= llvm-ar -HOSTCC ?= clang -HOSTLD ?= ld.lld +HOSTAR ?= llvm-ar$(LLVM_SFX) +HOSTCC ?= clang$(LLVM_SFX) +HOSTLD ?= ld.lld$(LLVM_SFX) else HOSTAR ?= ar HOSTCC ?= gcc diff --git a/tools/testing/selftests/lib.mk b/tools/testing/selftests/lib.mk index a40add31a2e3..b3ab713537c6 100644 --- a/tools/testing/selftests/lib.mk +++ b/tools/testing/selftests/lib.mk @@ -1,7 +1,11 @@ # This mimics the top-level Makefile. We do it explicitly here so that this # Makefile can operate with or without the kbuild infrastructure. ifneq ($(LLVM),) -CC := clang +ifneq ($(LLVM),1) +LLVM_SFX := $(LLVM) +endif + +CC := clang$(LLVM_SFX) else CC := $(CROSS_COMPILE)gcc endif
base-commit: 55de8686df7ed2b5237867b130e30c728bbd9db4