The current LLVM and Clang build procedure in samples/bpf/README.rst is out of date.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 and Clang, the Clang Getting Started page [1] has one way. As Yonghong said, it is better to 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. Additionally, as Fangrui said, the dir llvm-project/llvm/build/install is not used, BUILD_SHARED_LIBS=OFF is the default option [2], so also change Documentation/bpf/bpf_devel_QA.rst together. At last, we recommend that developers who want the fastest incremental builds use the Ninja build system [1], you can find it in your system's package manager, usually the package is ninja or ninja-build [3], so add ninja to build dependencies suggested by Nathan. [1] https://clang.llvm.org/get_started.html [2] https://www.llvm.org/docs/CMake.html [3] https://github.com/ninja-build/ninja/wiki/Pre-built-Ninja-packages Signed-off-by: Tiezhu Yang <yangtiezhu@xxxxxxxxxxx> Acked-by: Yonghong Song <yhs@xxxxxx> Reviewed-by: Nathan Chancellor <natechancellor@xxxxxxxxx> --- v2: Update the commit message suggested by Yonghong, thank you very much. v3: Remove the default option BUILD_SHARED_LIBS=OFF and just mkdir llvm-project/llvm/build suggested by Fangrui. v4: Add some description about ninja suggested by Nathan. Documentation/bpf/bpf_devel_QA.rst | 11 +++++++---- samples/bpf/Makefile | 2 +- samples/bpf/README.rst | 22 ++++++++++++++-------- 3 files changed, 22 insertions(+), 13 deletions(-) diff --git a/Documentation/bpf/bpf_devel_QA.rst b/Documentation/bpf/bpf_devel_QA.rst index 5b613d2..2ed89ab 100644 --- a/Documentation/bpf/bpf_devel_QA.rst +++ b/Documentation/bpf/bpf_devel_QA.rst @@ -501,16 +501,19 @@ All LLVM releases can be found at: http://releases.llvm.org/ Q: Got it, so how do I build LLVM manually anyway? -------------------------------------------------- -A: You need cmake and gcc-c++ as build requisites for LLVM. Once you have -that set up, proceed with building the latest LLVM and clang version +A: We recommend that developers who want the fastest incremental builds +use the Ninja build system, you can find it in your system's package +manager, usually the package is ninja or ninja-build. + +You need ninja, cmake and gcc-c++ as build requisites for LLVM. Once you +have that set up, proceed with building the latest LLVM and clang version from the git repositories:: $ git clone https://github.com/llvm/llvm-project.git - $ mkdir -p llvm-project/llvm/build/install + $ mkdir -p llvm-project/llvm/build $ cd llvm-project/llvm/build $ cmake .. -G "Ninja" -DLLVM_TARGETS_TO_BUILD="BPF;X86" \ -DLLVM_ENABLE_PROJECTS="clang" \ - -DBUILD_SHARED_LIBS=OFF \ -DCMAKE_BUILD_TYPE=Release \ -DLLVM_BUILD_RUNTIME=OFF $ ninja 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..60c6494 100644 --- a/samples/bpf/README.rst +++ b/samples/bpf/README.rst @@ -62,20 +62,26 @@ To generate a smaller llc binary one can use:: -DLLVM_TARGETS_TO_BUILD="BPF" +We recommend that developers who want the fastest incremental builds +use the Ninja build system, you can find it in your system's package +manager, usually the package is ninja or ninja-build. + Quick sniplet for manually compiling LLVM and clang -(build dependencies are cmake and gcc-c++):: +(build dependencies are ninja, 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 + $ cd llvm-project/llvm/build + $ cmake .. -G "Ninja" -DLLVM_TARGETS_TO_BUILD="BPF;X86" \ + -DLLVM_ENABLE_PROJECTS="clang" \ + -DCMAKE_BUILD_TYPE=Release \ + -DLLVM_BUILD_RUNTIME=OFF + $ 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
