Messages in this thread | | | Subject | Re: [PATCH bpf-next v2] samples/bpf: Update README.rst and Makefile for manually compiling LLVM and clang | From | Tiezhu Yang <> | Date | Wed, 20 Jan 2021 10:32:14 +0800 |
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On 01/20/2021 05:58 AM, Fangrui Song wrote: > On 2021-01-19, Tiezhu Yang wrote: >> The current llvm/clang build procedure in samples/bpf/README.rst is >> out of date. See below that the links are not accessible any more. >> >> $ git clone http://llvm.org/git/llvm.git >> Cloning into 'llvm'... >> fatal: unable to access 'http://llvm.org/git/llvm.git/': Maximum (20) >> redirects followed >> $ git clone --depth 1 http://llvm.org/git/clang.git >> Cloning into 'clang'... >> fatal: unable to access 'http://llvm.org/git/clang.git/': Maximum >> (20) redirects followed >> >> The llvm community has adopted new ways to build the compiler. There are >> different ways to build llvm/clang, the Clang Getting Started page >> [1] has >> one way. As Yonghong said, it is better to just copy the build procedure >> in Documentation/bpf/bpf_devel_QA.rst to keep consistent. >> >> I verified the procedure and it is proved to be feasible, so we should >> update README.rst to reflect the reality. At the same time, update the >> related comment in Makefile. >> >> [1] https://clang.llvm.org/get_started.html >> >> Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn> >> Acked-by: Yonghong Song <yhs@fb.com> >> --- >> >> v2: Update the commit message suggested by Yonghong, >> thank you very much. >> >> samples/bpf/Makefile | 2 +- >> samples/bpf/README.rst | 17 ++++++++++------- >> 2 files changed, 11 insertions(+), 8 deletions(-) >> >> diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile >> index 26fc96c..d061446 100644 >> --- a/samples/bpf/Makefile >> +++ b/samples/bpf/Makefile >> @@ -208,7 +208,7 @@ TPROGLDLIBS_xdpsock += -pthread -lcap >> TPROGLDLIBS_xsk_fwd += -pthread >> >> # Allows pointing LLC/CLANG to a LLVM backend with bpf support, >> redefine on cmdline: >> -# make M=samples/bpf/ LLC=~/git/llvm/build/bin/llc >> CLANG=~/git/llvm/build/bin/clang >> +# make M=samples/bpf LLC=~/git/llvm-project/llvm/build/bin/llc >> CLANG=~/git/llvm-project/llvm/build/bin/clang >> LLC ?= llc >> CLANG ?= clang >> OPT ?= opt >> diff --git a/samples/bpf/README.rst b/samples/bpf/README.rst >> index dd34b2d..d1be438 100644 >> --- a/samples/bpf/README.rst >> +++ b/samples/bpf/README.rst >> @@ -65,17 +65,20 @@ To generate a smaller llc binary one can use:: >> Quick sniplet for manually compiling LLVM and clang >> (build dependencies are cmake and gcc-c++):: >> >> - $ git clone http://llvm.org/git/llvm.git >> - $ cd llvm/tools >> - $ git clone --depth 1 http://llvm.org/git/clang.git >> - $ cd ..; mkdir build; cd build >> - $ cmake .. -DLLVM_TARGETS_TO_BUILD="BPF;X86" >> - $ make -j $(getconf _NPROCESSORS_ONLN) >> + $ git clone https://github.com/llvm/llvm-project.git >> + $ mkdir -p llvm-project/llvm/build/install > > llvm-project/llvm/build/install is not used.
Yes, just mkdir -p llvm-project/llvm/build is OK.
> >> + $ cd llvm-project/llvm/build >> + $ cmake .. -G "Ninja" -DLLVM_TARGETS_TO_BUILD="BPF;X86" \ >> + -DLLVM_ENABLE_PROJECTS="clang" \ >> + -DBUILD_SHARED_LIBS=OFF \ > > -DBUILD_SHARED_LIBS=OFF is the default. It can be omitted.
I search the related doc [1] [2], remove this option is OK for me.
BUILD_SHARED_LIBS:BOOL
Flag indicating if each LLVM component (e.g. Support) is built as a shared library (ON) or as a static library (OFF). Its default value is OFF.
[1] https://www.llvm.org/docs/CMake.html [2] https://cmake.org/cmake/help/latest/variable/BUILD_SHARED_LIBS.html
> >> + -DCMAKE_BUILD_TYPE=Release \ >> + -DLLVM_BUILD_RUNTIME=OFF > > -DLLVM_BUILD_RUNTIME=OFF can be omitted if none of > compiler-rt/libc++/libc++abi is built.
I am not very sure about it because the default value of LLVM_BUILD_RUNTIME is ON? [3]
option(LLVM_BUILD_RUNTIME "Build the LLVM runtime libraries." ON)
[3] https://github.com/llvm/llvm-project/blob/main/llvm/CMakeLists.txt
If anyone has any more suggestions, please let me know. I will send v3 after waiting for other feedback.
By the way, Documentation/bpf/bpf_devel_QA.rst maybe need a separate patch to remove some cmake options?
Thanks, Tiezhu
> >> + $ ninja >> >> It is also possible to point make to the newly compiled 'llc' or >> 'clang' command via redefining LLC or CLANG on the make command line:: >> >> - make M=samples/bpf LLC=~/git/llvm/build/bin/llc >> CLANG=~/git/llvm/build/bin/clang >> + make M=samples/bpf LLC=~/git/llvm-project/llvm/build/bin/llc >> CLANG=~/git/llvm-project/llvm/build/bin/clang >> >> Cross compiling samples >> ----------------------- >> -- >> 2.1.0 >> >> -- >> You received this message because you are subscribed to the Google >> Groups "Clang Built Linux" group. >> To unsubscribe from this group and stop receiving emails from it, >> send an email to clang-built-linux+unsubscribe@googlegroups.com. >> To view this discussion on the web visit >> https://groups.google.com/d/msgid/clang-built-linux/1611042978-21473-1-git-send-email-yangtiezhu%40loongson.cn.
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