On Sat, Oct 30, 2021 at 4:34 PM Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote: > > > Latestest greatness... :-) > > --- > Subject: kbuild: Fix clang/llvm build infra > > Debian (and derived) distros ship their compilers as -$ver suffixed > binaries. For gcc it is sufficent to use: > > $ make CC=gcc-12 > > However, clang builds (esp. clang-lto) need a whole array of tools to be > exactly right, leading to unweildy stuff like: > > $ make CC=clang-13 LD=ld.lld=14 AR=llvm-ar-13 NM=llvm-nm-13 OBJCOPY=llvm-objcopy-13 OBJDUMP=llvm-objdump-13 READELF=llvm-readelf-13 STRIP=llvm-strip-13 LLVM=1 > > which is, quite franktly, totally insane and unusable. Instead make > the CC variable DTRT, enabling one such as myself to use: > > $ make CC=clang-13 > > This also lets one quickly test different clang versions. > Additionally, also support path based LLVM suites like: > > $ make CC=/opt/llvm/bin/clang > Hi Peter, Thanks for bringing this up again. Your issue is not new for Debianist and Linux-LLVM/Clang folks. But let me comment. I agree, it is preferable or should be treated the same way in using clang-$ver like gcc-$ver. Background: Debian uses as meta-package llvm-toolchain-$ver and splits stuff into different Debian packages like the Clang compiler. LLD linker and LLVM (bin)utils. These packages place their files in separate directories to distinguish llvm-toolchain-$ver. Binaries like clang-$ver, ld.lld-$ver, llvm-strip-$ver, etc. you find in the /usr/bin/ directory which are symlinks. Clang compiler is shipped with clang-$ver Debian package. LLD linker is shipped as a separate Debian package called lld-$ver. LLVM (bin)utils like llvm-strip-$ver are shipped with the llvm-$ver Debian package. Link: https://www.kernel.org/doc/html/latest/kbuild/llvm.html#llvm-utilities EXAMPLES (here: llvm-toolchain-13): $ dpkg -S $(which clang-13) clang-13: /usr/bin/clang-13 $ dpkg -S /usr/bin/ld.lld-13 lld-13: /usr/bin/ld.lld-13 $ dpkg -S /usr/bin/llvm-strip-13 llvm-13: /usr/bin/llvm-strip-13 $ LC_ALL=C ll /usr/bin/clang-13 lrwxrwxrwx 1 root root 24 Oct 23 10:33 /usr/bin/clang-13 -> ../lib/llvm-13/bin/clang $ LC_ALL=C ll /usr/bin/ld.lld-13 lrwxrwxrwx 1 root root 25 Oct 23 10:33 /usr/bin/ld.lld-13 -> ../lib/llvm-13/bin/ld.lld $ LC_ALL=C ll /usr/bin/llvm-strip-13 lrwxrwxrwx 1 root root 29 Oct 23 10:33 /usr/bin/llvm-strip-13 -> ../lib/llvm-13/bin/llvm-strip As a compromise I use in my build_linux-llvm-toolchain.sh script $LLVM_TOOLCHAIN_PATH: ... ### GCC and LLVM version settings ##GCC_MAJOR_VER="10" LLVM_MAJOR_VER="13" ### LLVM toolchain path options # Explicitly set PATH to simplify `make LLVM=1` handling (see "LLVM tools options") # Option-1: Use system's LLVM toolchain # Option-2: Use selfmade LLVM toolchain (here: ThinLTO+PGO optimized via tc-build) # Option-3: Set custom PATH in ~/.bashrc ##LLVM_TOOLCHAIN_PATH="/usr/lib/llvm-${LLVM_MAJOR_VER}/bin" LLVM_TOOLCHAIN_PATH="/opt/llvm-toolchain/bin" if [ -d ${LLVM_TOOLCHAIN_PATH} ]; then export PATH="${LLVM_TOOLCHAIN_PATH}:${PATH}" fi ... But... ...for several new features like Clang-LTO we need the LLVM full "eco system". LLVM eco system means compiler, linker and binutils. In several talks at LPC 2021 talkers used the term "LLVM/binutils" like for GNU/binutils. The LLVM/Clang kernel-docs talk about "LLVM util(itie)s" which is set by LLVM=1 or not (LLVM=0). Link: https://www.kernel.org/doc/html/latest/kbuild/llvm.html#llvm-utilities AFAICS your patch has a primary focus to fix the LLVM/Clang infrastructure when CONFIG_LTO_CLANG=y, right? Can you massage the commit message to reflect this? IMHO your patch can be improved to check for CONFIG_LTO_CLANG=y where LLVM=1 is mandatory and IIRC LLVM_IAS=1, too. ( The default to use LLVM/Clang-IAS (Integrated ASsembler) was changed recently for some combinations arches + Clang-LTO? ) Before I forgot: Can you add a comment for the PPC and S390 situation in the commit message. Please remember people also want to use combinations like gcc-$ver and LLVM/binutils like ld.lld-$ver. GCC-10 + LLD-$VER was the fastest combination to build a Linux Debian package here on my Intel SandyBridge CPU system. ( There exists overrides like LD=... STRIP=... and I use XXX_FOR_BUILD=... (see my attached build-script). ) Thanks. Regards, - Sedat - > Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx> > --- > Makefile | 45 +++++++++++++++++++++++++++--------- > tools/scripts/Makefile.include | 50 ++++++++++++++++++++++++++++------------- > 2 files changed, 68 insertions(+), 27 deletions(-) > > --- a/Makefile > +++ b/Makefile > @@ -423,9 +423,29 @@ HOST_LFS_CFLAGS := $(shell getconf LFS_C > 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++ > +# powerpc and s390 don't yet work with LLVM as a whole > +ifeq ($(ARCH),powerpc) > +LLVM = 0 > +endif > +ifeq ($(ARCH),s390) > +LLVM = 0 > +endif > + > +# otherwise, if CC=clang, default to using LLVM to enable LTO > +CC_BASE := $(shell echo $(CC) | sed 's/.*\///') > +CC_NAME := $(shell echo $(CC_BASE) | cut -b "1-5") > +ifeq ($(shell test "$(CC_NAME)" = "clang"; echo $$?),0) > +LLVM ?= 1 > +LLVM_PFX := $(shell echo $(CC) | sed 's/\(.*\/\)\?.*/\1/') > +LLVM_SFX := $(shell echo $(CC_BASE) | cut -b "6-") > +endif > + > +# if not set by now, do not use LLVM > +LLVM ?= 0 > + > +ifneq ($(LLVM),0) > +HOSTCC = $(LLVM_PFX)clang$(LLVM_SFX) > +HOSTCXX = $(LLVM_PFX)clang++$(LLVM_SFX) > else > HOSTCC = gcc > HOSTCXX = g++ > @@ -442,15 +462,15 @@ KBUILD_HOSTLDLIBS := $(HOST_LFS_LIBS) > > # 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 > +ifneq ($(LLVM),0) > +CC = $(LLVM_PFX)clang$(LLVM_SFX) > +LD = $(LLVM_PFX)ld.lld$(LLVM_SFX) > +AR = $(LLVM_PFX)llvm-ar$(LLVM_SFX) > +NM = $(LLVM_PFX)llvm-nm$(LLVM_SFX) > +OBJCOPY = $(LLVM_PFX)llvm-objcopy$(LLVM_SFX) > +OBJDUMP = $(LLVM_PFX)llvm-objdump$(LLVM_SFX) > +READELF = $(LLVM_PFX)llvm-readelf$(LLVM_SFX) > +STRIP = $(LLVM_PFX)llvm-strip$(LLVM_SFX) > else > CC = $(CROSS_COMPILE)gcc > LD = $(CROSS_COMPILE)ld > @@ -461,6 +481,7 @@ OBJDUMP = $(CROSS_COMPILE)objdump > READELF = $(CROSS_COMPILE)readelf > STRIP = $(CROSS_COMPILE)strip > endif > + > PAHOLE = pahole > RESOLVE_BTFIDS = $(objtree)/tools/bpf/resolve_btfids/resolve_btfids > LEX = flex > --- a/tools/scripts/Makefile.include > +++ b/tools/scripts/Makefile.include > @@ -51,12 +51,32 @@ define allow-override > $(eval $(1) = $(2))) > endef > > -ifneq ($(LLVM),) > -$(call allow-override,CC,clang) > -$(call allow-override,AR,llvm-ar) > -$(call allow-override,LD,ld.lld) > -$(call allow-override,CXX,clang++) > -$(call allow-override,STRIP,llvm-strip) > +# powerpc and s390 don't yet work with LLVM as a whole > +ifeq ($(ARCH),powerpc) > +LLVM = 0 > +endif > +ifeq ($(ARCH),s390) > +LLVM = 0 > +endif > + > +# otherwise, if CC=clang, default to using LLVM to enable LTO > +CC_BASE := $(shell echo $(CC) | sed 's/.*\///') > +CC_NAME := $(shell echo $(CC_BASE) | cut -b "1-5") > +ifeq ($(shell test "$(CC_NAME)" = "clang"; echo $$?),0) > +LLVM ?= 1 > +LLVM_PFX := $(shell echo $(CC) | sed 's/\(.*\/\)\?.*/\1/') > +LLVM_SFX := $(shell echo $(CC_BASE) | cut -b "6-") > +endif > + > +# if not set by now, do not use LLVM > +LLVM ?= 0 > + > +ifneq ($(LLVM),0) > +$(call allow-override,CC,$(LLVM_PFX)clang$(LLVM_SFX)) > +$(call allow-override,AR,$(LLVM_PFX)llvm-ar$(LLVM_SFX)) > +$(call allow-override,LD,$(LLVM_PFX)ld.lld$(LLVM_SFX)) > +$(call allow-override,CXX,$(LLVM_PFX)clang++$(LLVM_SFX)) > +$(call allow-override,STRIP,$(LLVM_PFX)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) > @@ -68,10 +88,10 @@ endif > > CC_NO_CLANG := $(shell $(CC) -dM -E -x c /dev/null | grep -Fq "__clang__"; echo $$?) > > -ifneq ($(LLVM),) > -HOSTAR ?= llvm-ar > -HOSTCC ?= clang > -HOSTLD ?= ld.lld > +ifneq ($(LLVM),0) > +HOSTAR ?= $(LLVM_PFX)llvm-ar$(LLVM_SFX) > +HOSTCC ?= $(LLVM_PFX)clang$(LLVM_SFX) > +HOSTLD ?= $(LLVM_PFX)ld.lld$(LLVM_SFX) > else > HOSTAR ?= ar > HOSTCC ?= gcc > @@ -79,11 +99,11 @@ HOSTLD ?= ld > endif > > # Some tools require Clang, LLC and/or LLVM utils > -CLANG ?= clang > -LLC ?= llc > -LLVM_CONFIG ?= llvm-config > -LLVM_OBJCOPY ?= llvm-objcopy > -LLVM_STRIP ?= llvm-strip > +CLANG ?= $(LLVM_PFX)clang$(LLVM_SFX) > +LLC ?= $(LLVM_PFX)llc$(LLVM_SFX) > +LLVM_CONFIG ?= $(LLVM_PFX)llvm-config$(LLVM_SFX) > +LLVM_OBJCOPY ?= $(LLVM_PFX)llvm-objcopy$(LLVM_SFX) > +LLVM_STRIP ?= $(LLVM_PFX)llvm-strip$(LLVM_SFX) > > ifeq ($(CC_NO_CLANG), 1) > EXTRA_WARNINGS += -Wstrict-aliasing=3
Attachment:
build_linux-llvm-toolchain.sh
Description: application/shellscript
