[standalone-build-x86_64]: build lld

[kwk]

Summary

This adds building lld to the standalone-build-x86_64 script.

[serge-sans-paille]

zorg/buildbot/builders/annotated/standalone-build.sh

87

looks redundant :-)

128

It basically means that lld currently does not build in standalone mode, correct?
What is the impact on the change below, It doesn't provide any actual file, is lld still functional in that setup?

[kwk]

• Remove redundant info

[kwk]

zorg/buildbot/builders/annotated/standalone-build.sh

128

lld during build time tries to resolve a path to an include file by going first to the llvm directory only to go back to ../ and then going into libunwind/include/. Indeed, this won't work in standalone build mode unless we checkout the llvm directory which is exactly what we don't want. But as a compromise I create an empty llvm dir so that at least the path resolve process does work without consuming files from this location. I can run lld and it outputs:

$~/llvm-build-standalone/install/lld/bin $ ./lld --help
lld is a generic driver.
Invoke ld.lld (Unix), ld64.lld (macOS), lld-link (Windows), wasm-ld (WebAssembly) instead

I think it really is only the include path that is broken and there's an old PR by @tstellar that touches on this subject: https://reviews.llvm.org/D32595.

zorg/buildbot/builders/annotated/standalone-build.sh

build_llvm() {
     cmake --build ${LLVM_BUILD_DIR}
 
     build_step "Installing llvm"
     rm -rf ${LLVM_INSTALL_DIR}
     cmake --install ${LLVM_BUILD_DIR}
 
     # This is meant to extinguish any dependency on files being taken
     # from the llvm build dir when building clang.
-    build_step "Removing llvm build directory"
+    build_step "Removing llvm build dir"
     rm -rf "${LLVM_BUILD_DIR}"
 }
 
 build_clang() {
     local LLVM_INSTALL_DIR=$(install_dir llvm)
     local CLANG_BUILD_DIR=$(build_dir clang)
     local CLANG_INSTALL_DIR=$(install_dir clang)
 
     build_step "Sparse checkout out clang"
     git -C "${LLVM_ROOT}" sparse-checkout set clang cmake
cmake \
         -DLLVM_ROOT=${LLVM_INSTALL_DIR}
 
     build_step "Building clang"
     LD_LIBRARY_PATH="${LLVM_INSTALL_DIR}/lib64" cmake --build ${CLANG_BUILD_DIR}
 
     build_step "Installing clang"
     rm -rf ${CLANG_INSTALL_DIR}
     cmake --install ${CLANG_BUILD_DIR}
+
+    build_step "Removing clang build dir"
+    rm -rf ${CLANG_BUILD_DIR}
+}
+
+build_lld() {
+    local LLVM_INSTALL_DIR=$(install_dir llvm)
+    local LLD_BUILD_DIR=$(build_dir lld)
+    local LLD_INSTALL_DIR=$(install_dir lld)
+
+    build_step "Sparse checkout out lld"
+    git -C "${LLVM_ROOT}" sparse-checkout set lld cmake libunwind
+    
+    # We don't want to checkout the llvm source tree but sadly there are paths
+    # like ${LLVM_MAIN_SRC_DIR}/../libunwind/include in lld source code. They
+    # resolve to /<SOMEPATH>/../llvm/../libunwind/include which makes absolutely
+    # no sense when the llvm dir doesn't exist. Let's fix this by just providing
+    # the empty llvm dir so that paths are resolved without errors.
+    # TODO: I don't know how to fix this easily
+    rm -rf "${LLVM_ROOT}"/llvm && mkdir "${LLVM_ROOT}"/llvm
+    rm -rf ${LLD_INSTALL_DIR}
+    rm -rf ${LLD_BUILD_DIR}
+
+    build_step "Configuring lld"
+    cmake \
+        -S ${LLVM_ROOT}/lld \
+        -B ${LLD_BUILD_DIR} \
+        -G Ninja \
+        -DCMAKE_BUILD_TYPE=${BUILD_TYPE} \
+        -DLLVM_LINK_LLVM_DYLIB=ON \
+        -DCLANG_INCLUDE_TESTS=ON \
+        -DLLVM_EXTERNAL_LIT=${LLVM_INSTALL_DIR}/bin/lit \
+        -DCMAKE_INSTALL_PREFIX=${LLD_INSTALL_DIR} \
+        -DLLVM_ROOT=${LLVM_INSTALL_DIR}
+
+    build_step "Building lld"
+    LD_LIBRARY_PATH="${LLVM_INSTALL_DIR}/lib64" cmake --build ${LLD_BUILD_DIR}
+
+    build_step "Installing lld"
+    rm -rf ${LLD_INSTALL_DIR}
+    cmake --install ${LLD_BUILD_DIR}
+
+    build_step "Removing lld build dir"
+    rm -rf ${LLD_BUILD_DIR}
 }
 
 setup_llvm_project
 pre_build_cleanup
 
 build_llvm
 build_clang
+build_lld
 
 exit 0