Introduce a Bazel build configuration

This patch introduces configuration for a Bazel BUILD in a side
directory in the monorepo.

This is following the approval of
https://github.com/llvm/llvm-www/blob/main/proposals/LP0002-BazelBuildConfiguration.md

As detailed in the README, the Bazel BUILD is not supported
by the community in general, and is maintained only by interested
parties. It follows the requirements of the LLVM peripheral tier:
https://llvm.org/docs/SupportPolicy.html#peripheral-tier.

This is largely copied from https://github.com/google/llvm-bazel,
with a few filepath tweaks and the addition of the README.

Reviewed By: echristo, keith, dblaikie, kuhar

Differential Revision: https://reviews.llvm.org/D90352

1 files changed, 150 insertions, 0 deletions

diff --git a/utils/bazel/.bazelrc b/utils/bazel/.bazelrc
new file mode 100644
index 0000000..ce1d654
--- /dev/null
+++ b/utils/bazel/.bazelrc
@@ -0,0 +1,150 @@
+# This file is licensed under the Apache License v2.0 with LLVM Exceptions.
+# See https://llvm.org/LICENSE.txt for license information.
+# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+###############################################################################
+# Common flags that apply to all configurations.
+# Use sparingly for things common to all compilers and platforms.
+###############################################################################
+# Prevent invalid caching if input files are modified during a build.
+build --experimental_guard_against_concurrent_changes
+
+###############################################################################
+# Options to select different strategies for linking potential dependent
+# libraries. The default leaves it disabled.
+###############################################################################
+
+build:zlib_external --repo_env=BAZEL_LLVM_ZLIB_STRATEGY=external
+build:zlib_system --repo_env=BAZEL_LLVM_ZLIB_STRATEGY=system
+
+build:terminfo_external --repo_env=BAZEL_LLVM_TERMINFO_STRATEGY=external
+build:terminfo_system --repo_env=BAZEL_LLVM_TERMINFO_STRATEGY=system
+
+###############################################################################
+# Options for "generic_clang" builds: these options should generally apply to
+# builds using a Clang-based compiler, and default to the `clang` executable on
+# the `PATH`. While these are provided for convenience and may serve as a
+# reference, it would be preferable for users to configure an explicit C++
+# toolchain instead of relying on `.bazelrc` files.
+###############################################################################
+
+# Set the default compiler to the `clang` binary on the `PATH`.
+build:generic_clang --repo_env=CC=clang
+
+# C++14 standard version is required.
+build:generic_clang --cxxopt=-std=c++14 --host_cxxopt=-std=c++14
+
+# The Clang available on MacOS has a warning that isn't clean on MLIR code. The
+# warning doesn't show up with more recent Clangs, so just disable for now.
+build:generic_clang --cxxopt=-Wno-range-loop-analysis --host_cxxopt=-Wno-range-loop-analysis
+
+# Use `-Wall` and `-Werror` for Clang.
+build:generic_clang --copt=-Wall --copt=-Werror --host_copt=-Wall --host_copt=-Werror
+# This doesn't appear to be enforced by any upstream bot.
+build:generic_clang --copt=-Wno-unused --host_copt=-Wno-unused
+
+###############################################################################
+# Options for "generic_gcc" builds: these options should generally apply to
+# builds using a GCC-based compiler, and default to the `gcc` executable on
+# the `PATH`. While these are provided for convenience and may serve as a
+# reference, it would be preferable for users to configure an explicit C++
+# toolchain instead of relying on `.bazelrc` files.
+###############################################################################
+
+# Set the default compiler to the `gcc` binary on the `PATH`.
+build:generic_gcc --repo_env=CC=gcc
+
+# C++14 standard version is required.
+build:generic_gcc --cxxopt=-std=c++14 --host_cxxopt=-std=c++14
+
+# Disable GCC warnings that are noisy and/or false positives on LLVM code.
+# These need to be global as some code triggering these is in header files.
+build:generic_gcc --copt=-Wno-unused-parameter --host_copt=-Wno-unused-parameter
+build:generic_gcc --copt=-Wno-comment --host_copt=-Wno-comment
+build:generic_gcc --cxxopt=-Wno-class-memaccess --host_cxxopt=-Wno-class-memaccess
+build:generic_gcc --copt=-Wno-maybe-uninitialized --host_copt=-Wno-maybe-uninitialized
+build:generic_gcc --copt=-Wno-misleading-indentation --host_copt=-Wno-misleading-indentation
+
+# Use `-Werror` for GCC to make sure warnings don't slip past.
+build:generic_gcc --copt=-Werror --host_copt=-Werror
+
+###############################################################################
+# Windows specific flags for building with VC.
+###############################################################################
+
+build:msvc --copt=/WX --host_copt=/WX    # Treat warnings as errors...
+# ...but disable the ones that are violated
+build:msvc --copt=/wd4141 --host_copt=/wd4141 # inline used more than once
+build:msvc --copt=/wd4244 --host_copt=/wd4244 # conversion type -> type
+build:msvc --copt=/wd4267 --host_copt=/wd4267 # conversion size_t -> type
+build:msvc --copt=/wd4273 --host_copt=/wd4273 # multiple definitions with different dllimport
+build:msvc --copt=/wd4319 --host_copt=/wd4319 # zero-extending after complement
+build:msvc --copt=/wd4624 --host_copt=/wd4624 # destructor was implicitly defined as deleted
+build:msvc --copt=/wd4804 --host_copt=/wd4804 # comparisons between bool and int
+build:msvc --copt=/wd4805 --host_copt=/wd4805 # comparisons between bool and int
+
+build:msvc --linkopt=/WX --host_linkopt=/WX # Treat warnings as errors...
+# ...but disable the ones that are violated.
+build:msvc --linkopt=/IGNORE:4001 --host_linkopt=/IGNORE:4001 # no object files
+
+# Yay for security warnings. Boo for non-standard.
+build:msvc --copt=/D_CRT_SECURE_NO_WARNINGS --host_copt=/D_CRT_SECURE_NO_WARNINGS
+
+###############################################################################
+
+###############################################################################
+# Configuration for building remotely using Remote Build Execution (RBE)
+# Based on https://github.com/bazelbuild/bazel-toolchains/blob/master/bazelrc/bazel-1.0.0.bazelrc
+###############################################################################
+
+build:rbe --remote_instance_name=projects/llvm-bazel/instances/default_instance
+
+# Depending on how many machines are in the remote execution instance, setting
+# this higher can make builds faster by allowing more jobs to run in parallel.
+# Setting it too high can result in jobs that timeout, however, while waiting
+# for a remote machine to execute them.
+build:rbe --jobs=150
+
+# Set several flags related to specifying the platform, toolchain and java
+# properties.
+# These flags should only be used as is for the rbe-ubuntu16-04 container
+# and need to be adapted to work with other toolchain containers.
+build:rbe --host_javabase=@rbe_default//java:jdk
+build:rbe --javabase=@rbe_default//java:jdk
+build:rbe --host_java_toolchain=@bazel_tools//tools/jdk:toolchain_hostjdk8
+build:rbe --java_toolchain=@bazel_tools//tools/jdk:toolchain_hostjdk8
+build:rbe --crosstool_top=@rbe_default//cc:toolchain
+build:rbe --action_env=BAZEL_DO_NOT_DETECT_CPP_TOOLCHAIN=1
+# Platform flags:
+# The toolchain container used for execution is defined in the target indicated
+# by "extra_execution_platforms", "host_platform" and "platforms".
+# More about platforms: https://docs.bazel.build/versions/master/platforms.html
+build:rbe --extra_toolchains=@rbe_default//config:cc-toolchain
+build:rbe --extra_execution_platforms=@rbe_default//config:platform
+build:rbe --host_platform=@rbe_default//config:platform
+build:rbe --platforms=@rbe_default//config:platform
+
+build:rbe --define=EXECUTOR=remote
+
+# Enable remote execution so actions are performed on the remote systems.
+build:rbe --remote_executor=grpcs://remotebuildexecution.googleapis.com
+
+# Enforce stricter environment rules, which eliminates some non-hermetic
+# behavior and therefore improves both the remote cache hit rate and the
+# correctness and repeatability of the build.
+build:rbe --incompatible_strict_action_env=true
+
+# Set a higher timeout value, just in case.
+build:rbe --remote_timeout=3600
+
+# Local disk cache is incompatible with remote execution (for obvious reasons).
+build:rbe --disk_cache=""
+
+# Enable authentication. This will pick up application default credentials by
+# default. You can use --google_credentials=some_file.json to use a service
+# account credential instead.
+build:rbe --google_default_credentials=true
+
+# The user.bazelrc file is not checked in but available for local mods.
+# Always keep this at the end of the file so that user flags override.
+try-import %workspace%/user.bazelrc