[llvm] [bazel] Add support for LLVM_TOOL_LLVM_DRIVER_BUILD (PR #86879)

[Jordan Rupprecht via llvm-commits]

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+# 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
+
+"""Configuration for the llvm-driver tool."""
+
+load("@bazel_skylib//rules:common_settings.bzl", "BuildSettingInfo")
+load("@bazel_skylib//rules:expand_template.bzl", "expand_template")
+
+# Mapping from every tool to the cc_library that implements the tool's entrypoint.
+# TODO: uncomment the remaining targets after splitting them
+# into separate library/binary targets.
+_TOOLS = {
+    # "clang": "//clang:clang-driver",
+    # "clang-scan-deps": "//clang:clang-scan-deps-lib",
+    # "dsymutil": "//llvm:dsymutil-lib",
+    "llvm-ar": "//llvm:llvm-ar-lib",
+    # "llvm-cxxfilt": "//llvm:llvm-cxxfilt-lib",
+    # "llvm-dwp": "//llvm:llvm-dwp-lib",
+    # "llvm-gsymutil": "//llvm:llvm-gsymutil-lib",
+    # "llvm-ifs": "//llvm:llvm-ifs-lib",
+    # "llvm-libtool-darwin": "//llvm:llvm-libtool-darwin-lib",
+    # "llvm-lipo": "//llvm:llvm-lipo-lib",
+    # "llvm-ml": "//llvm:llvm-ml-lib",
+    # "llvm-mt": "//llvm:llvm-mt-lib",
+    "llvm-nm": "//llvm:llvm-nm-lib",
+    # "llvm-objcopy": "//llvm:llvm-objcopy-lib",
+    # "llvm-objdump": "//llvm:llvm-objdump-lib",
+    # "llvm-profdata": "//llvm:llvm-profdata-lib",
+    # "llvm-rc": "//llvm:llvm-rc-lib",
+    # "llvm-readobj": "//llvm:llvm-readobj-lib",
+    "llvm-size": "//llvm:llvm-size-lib",
+    # "llvm-symbolizer": "//llvm:llvm-symbolizer-lib",
+    # "sancov": "//llvm:sancov-lib",
+    # "lld": "//lld:lld-lib",
+}
+
+# Tools automatically get their own name as an alias, but there may be additional
+# aliases for a given tool.
+_EXTRA_ALIASES = {
+    "clang": ["clang++", "clang-cl", "clang-cpp"],
+    "lld": ["lld-link", "ld.lld", "ld64.lld", "wasm-ld"],
+    "llvm-ar": ["ranlib", "lib", "dlltool"],
+    "llvm-objcopy": ["bitcode-strip", "install-name-tool", "strip"],
+    "llvm-objdump": ["otool"],
+    "llvm-rc": ["windres"],
+    "llvm-readobj": ["readelf"],
+    "llvm-symbolizer": ["addr2line"],
+}
+
+def _validated_string_list_flag_impl(ctx):
+    invalid_values = [v for v in ctx.build_setting_value if v not in ctx.attr.values]
+    if invalid_values:
+        fail("Tool(s) [{}] are not in the known list of tools: {}".format(
+            ", ".join(invalid_values),
+            ", ".join(ctx.attr.values),
+        ))
+    return BuildSettingInfo(value = ctx.build_setting_value)
+
+# Like string_list_flag, but with the validation that string_flag provides.
+_validated_string_list_flag = rule(
+    implementation = _validated_string_list_flag_impl,
+    build_setting = config.string_list(flag = True),
+    attrs = {
+        "values": attr.string_list(
+            doc = "The list of allowed values for this setting. An error is raised if any other value is given.",
+        ),
+    },
+    doc = "A string list-typed build setting that can be set on the command line",
+)
+
+def generate_driver_selects(name):
+    """Generates flags and config settings to configure the tool list.
+
+    By default, all tools in LLVM are included in the "llvm" driver binary.
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rupprecht wrote:

Yep, that's right -- done.

This is also temporarily wrong since it's just nm/ar/size in this patch, but I'll fix that up with a followup commit soon enough.

https://github.com/llvm/llvm-project/pull/86879