46580d43fc
Users should generally observe no difference as long as they don't use unintended option forms. Behavior changes: * `-t=d` is removed. Use `-t d` instead. * `--demangle=false` and `--demangle=0` cannot be used. Omit the option or use `--no-demangle`. Other flag-style options don't have `--no-` forms. * `--help-list` is removed. This is a `cl::` specific option. * llvm-readobj now supports grouped short options as well. * `--color` is removed. This is generally not useful (only apply to errors/warnings) but was inherited from Support. Some adjustment to the canonical forms (usually from GNU readelf; currently llvm-readobj has too many redundant aliases): * --dyn-syms is canonical. --dyn-symbols is a hidden alias * --file-header is canonical. --file-headers is a hidden alias * --histogram is canonical. --elf-hash-histogram is a hidden alias * --relocs is canonical. --relocations is a hidden alias * --section-groups is canonical. --elf-section-groups is a hidden alias OptTable avoids global option collision if we decide to support multiplexing for binary utilities. * Most one-dash long options are still supported. `-dt, -sd, -st, -sr` are dropped due to their conflict with grouped short options. * `--section-mapping=false` (D57365) is strange but is kept for now. * Many `cl::opt` variables were unnecessarily external. I added `static` whenever appropriate. Reviewed By: jhenderson Differential Revision: https://reviews.llvm.org/D105532 |
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| .. | ||
| deps_impl | ||
| examples | ||
| llvm_configs | ||
| llvm-project-overlay | ||
| third_party_build | ||
| .bazelignore | ||
| .bazelrc | ||
| .bazelversion | ||
| .gitignore | ||
| BUILD.bazel | ||
| configure.bzl | ||
| overlay_directories.py | ||
| README.md | ||
| terminfo.bzl | ||
| vulkan_sdk.bzl | ||
| WORKSPACE | ||
| zlib.bzl | ||
Introduction
Warning The Bazel build is experimental and best-effort, supported in line with the policy for LLVM's peripheral support tier. LLVM's official build system is CMake. If in doubt use that. If you make changes to LLVM, you're expected to update the CMake build but you don't need to update Bazel build files. Reviewers should not ask authors to update Bazel build files unless the author has opted in to support Bazel. Keeping the Bazel build files up-to-date is on the people who use the Bazel build.
Bazel is a multi-language build system focused on reproducible builds to enable dependency analysis and caching for fast incremental builds.
The main motivation behind the existence of an LLVM Bazel build is that a number of projects that depend on LLVM use Bazel, and Bazel works best when it knows about the whole source tree (as opposed to installing artifacts coming from another build system). Community members are also welcome to use Bazel for their own development as long as they continue to maintain the official CMake build system. See also, the proposal for adding this configuration.
Quick Start
git clone https://github.com/llvm/llvm-project.git; cd llvm-projectif you don't have a checkout yet.- Install Bazel at the version indicated by .bazelversion, following the official instructions, if you don't have it installed yet: https://docs.bazel.build/versions/master/install.html.
cd utils/bazelbazel build --config=generic_clang @llvm-project//...(if building on Unix with Clang).--config=generic_gccand--config=msvcare also available.
Configuration
The repository .bazelrc will import user-specific settings from a
user.bazelrc file (in addition to the standard locations). Adding your typical
config setting is recommended.
build --config=generic_clang
You can enable disk caching, which will cache build results
build --disk_cache=~/.cache/bazel-disk-cache
You can instruct Bazel to use a ramdisk for its sandboxing operations via --sandbox_base, which can help avoid IO bottlenecks for the symlink stragegy used for sandboxing. This is especially important with many inputs and many cores (see https://github.com/bazelbuild/bazel/issues/11868):
build --sandbox_base=/dev/shm
Bear in mind that this requires that your ramdisk is of sufficient size to hold any temporary files. Anecdotally, 1GB should be sufficient.
Coverage
The LLVM, MLIR, and Clang subprojects have configurations for Linux (Clang and GCC), Mac (Clang and GCC), and Windows (MSVC). Configuration options that are platform-specific are selected for in defines. Many are also hardcoded to the values currently used by all supported configurations. If there is a configuration you'd like to use that isn't supported, please send a patch.
Usage
To use in dependent projects using Bazel, you can import LLVM and then use the
provided configuration rule. See example usage in the examples/ directory.