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Build LLVM with the Repo Compiler

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rgal edited this page Sep 25, 2019 · 11 revisions

This page shows how to build the llvm-project-prepo project from source then use the resulting compiler to re-build LLVM on Linux.

Table of Contents

Building the initial repo compiler

  1. Clone the llvm-project-prepo repository.

    $ REPO_DIR="/the/directory/into/which/the/LLVM/source/code/will/be/cloned"
$ cd $REPO_DIR
$ git clone https://github.com/SNSystems/llvm-project-prepo.git

  2. Clone pstore.

    $ cd $REPO_DIR/llvm-project-prepo
$ git clone https://github.com/SNSystems/pstore.git

  3. (Temporary step) Checkout the branch named “build_llvm_project_repo_using_built_repo_compiler”.

    $ cd $REPO_DIR/llvm-project-prepo
$ git checkout build_llvm_project_repo_using_built_repo_compiler
$ cd $REPO_DIR/llvm-project-prepo/pstore
$ git checkout build_llvm_project_repo_using_built_repo_compiler

  4. Build LLVM enabling the clang and pstore subprojects.

    $ cd $REPO_DIR/llvm-project-prepo
$ mkdir build
$ cd build
$ cmake -G Ninja \
        -DCMAKE_BUILD_TYPE=Release \
        -DLLVM_ENABLE_PROJECTS="clang;pstore" \
        -DLLVM_TARGETS_TO_BUILD=X86 \
        -DLLVM_TOOL_CLANG_TOOLS_EXTRA_BUILD=OFF \
        ../llvm
$ ninja

Using the initial repo compiler to build LLVM

The process of using the compiler that we just built to compile LLVM consists of the following steps:

  • Compile the llvm-project-prepo project targeting the program repository using the initial repo compiler.
  • Convert the repository ticket files to ELF object files using repo2obj.
  • Link the ELF object files to generate an executable.
  • Repeat the above steps once to verify the database (i.e. all fragments are in the database).

These are now described in detail:

  1. Copy repo.json to any parent directory of $REPO_DIR/llvm-project-prepo/build.

     $ cd $REPO_DIR/llvm-project-prepo
 $ cp ./llvm/utils/repo/repo.json .
 $ cat repo.json
 {
 	"ar": "/usr/bin/ar",
 	"link": "/usr/bin/clang++",
 	"repo2obj": "/point/to/the/repo2obj/tool/in/llvm-pstore/build/directory"
 }

  2. Modify the repo2obj option to point to the full path of the repo2obj tool in your build directory.

    Continue to use your default ar and clang++ for the archiving and linking; modify the repo2obj option to point to the repo2obj tool in your build directory. Note: this must be an absolute path. e.g.:

     "repo2obj": "/home/username/llvm-project-prepo/build/bin/repo2obj"

  3. Generate a release build using the repo.cmake toolchain file.

     $ cd $REPO_DIR/llvm-project-prepo
 $ mkdir build_repo_release
 $ cd build_repo_release
 $ cmake -G Ninja \
         -DCMAKE_BUILD_TYPE=Release \
         -DLLVM_TARGETS_TO_BUILD=X86 \
         -DLLVM_ENABLE_PROJECTS="clang;pstore" \
         -DLLVM_TOOL_CLANG_TOOLS_EXTRA_BUILD=OFF \
         -DLLVM_DISABLE_DYNAMIC_LIBRARY_UNITTEST=ON \
         -DPSTORE_ENABLE_BROKER=OFF \
         -DCMAKE_TOOLCHAIN_FILE=$REPO_DIR/llvm-project-prepo/llvm/utils/repo/repo.cmake \
         -DCMAKE_CXX_COMPILER=$REPO_DIR/llvm-project-prepo/build/bin/clang++ \
         -DCMAKE_C_COMPILER=$REPO_DIR/llvm-project-prepo/build/bin/clang \
         -Dutils_dir=$REPO_DIR/llvm-project-prepo/llvm/utils/repo \
         ../llvm

    The CMake variables being defined here are:

    1. -DPSTORE_ENABLE_BROKER=OFF. Disable the pstore broker projects since they rely on exception handling which the repo compiler does not currently support.
    2. -DLLVM_DISABLE_DYNAMIC_LIBRARY_UNITTEST=ON. Disable the LLVM dynamic library unit tests (issue #12).
    3. -DCMAKE_TOOLCHAIN_FILE=…/repo.cmake. CMake uses the toolchain to describe the tools and how they should be run; we use it here to set compiler switches such as the target-triple and to run repo2obj before linking.
    4. -DCMAKE_CXX_COMPILER=…/clang++. Tell CMake where to find the repo C++ compiler that we built.
    5. -DCMAKE_C_COMPILER=…/clang. As above for the C compiler.
    6. -Dutils_dir=…/llvm/utils/repo. Specify the repo utilities directory, which contains additional scripts required for the build.

  4. Build LLVM.

    $ ninja

  5. To rebuild, you can clean/delete all ticket files. Code fragments created by the original build will be retained within the database.

    $ ninja clean
$ ninja

Running unit and regression tests

Currently, for a debug build, there are 30552 tests passed out of 30567 tests (99.95%) and for the release build, there are 30583 tests passed out of 30717 tests (99.56%). The issues found by the failing tests are being worked on.

	$ ninja check-all

Current build status

llvm-project-prepo has been built and run with the tests twice in both debug and release configurations.

Debug build with compiler switches: -O0 -fno-exceptions -fno-rtti.

Release build with compiler switches: -O3 -fno-exceptions -fno-rtti.

Configuration 1st build 1st run test 2nd build 2nd run test
Debug ✔ 99.95% tests passed ✔ 99.95% tests passed
Release ✔ 99.56% tests passed ✔ 99.56% tests passed

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