[libc][bazel] Create libc_release_library for release configurations. #130694
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See PR llvm#130327 for background and motivation. This change expands the libc_support_library and libc_function rules to create filegroups that allow building a collection of llvm-libc functions together, from sources, as a part of a single cc_library that can then be used by the downstream clients. This change also adds an example use of this macro under libc/test/BUILD.bazel to confirm that this macro works as expected.
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@llvm/pr-subscribers-libc Author: Alexey Samsonov (vonosmas) ChangesSee PR #130327 for background and motivation. This change expands the libc_support_library and libc_function rules to create filegroups that allow building a collection of llvm-libc functions together, from sources, as a part of a single cc_library that can then be used by the downstream clients. This change also adds an example use of this macro under libc/test/BUILD.bazel to confirm that this macro works as expected. Full diff: https://github.com/llvm/llvm-project/pull/130694.diff 2 Files Affected:
diff --git a/utils/bazel/llvm-project-overlay/libc/libc_build_rules.bzl b/utils/bazel/llvm-project-overlay/libc/libc_build_rules.bzl
index 09daa9ecb3675..0d60992bbd638 100644
--- a/utils/bazel/llvm-project-overlay/libc/libc_build_rules.bzl
+++ b/utils/bazel/llvm-project-overlay/libc/libc_build_rules.bzl
@@ -64,50 +64,72 @@ def _libc_library(name, copts = [], deps = [], local_defines = [], **kwargs):
**kwargs
)
+def _libc_library_filegroups(
+ name,
+ is_function,
+ srcs = [],
+ hdrs = [],
+ textual_hdrs = [],
+ deps = [],
+ # We're not using kwargs, but instead explicitly list all possible
+ # arguments that can be passed to libc_support_library or
+ # libc_function macros. This is done to limit the configurability
+ # and ensure the consistent and tightly controlled set of flags
+ # (see libc_common_copts and libc_release_copts above) is used to build
+ # libc code both for tests and for release configuration.
+ target_compatible_with = None, # @unused
+ weak = False): # @unused
+ """Internal macro to collect sources and headers required to build a library.
+ """
+
+ # filegroups created from "libc_function" macro has an extra "_fn" in their
+ # name to ensure that no other libc target can depend on libc_function.
+ prefix = name + ("_fn" if is_function else "")
+ native.filegroup(
+ name = prefix + "_srcs",
+ srcs = srcs + hdrs + [dep + "_srcs" for dep in deps],
+ )
+ native.filegroup(
+ name = prefix + "_textual_hdrs",
+ srcs = textual_hdrs + [dep + "_textual_hdrs" for dep in deps],
+ )
+
# A convenience function which should be used to list all libc support libraries.
# Any library which does not define a public function should be listed with
# libc_support_library.
def libc_support_library(name, **kwargs):
_libc_library(name = name, **kwargs)
+ _libc_library_filegroups(name = name, is_function = False, **kwargs)
def libc_function(
name,
- srcs,
weak = False,
- copts = [],
- local_defines = [],
**kwargs):
"""Add target for a libc function.
- The libc function is eventually available as a cc_library target by name
- "name". LLVM libc implementations of libc functions are in C++. So, this
- rule internally generates a C wrapper for the C++ implementation and adds
- it to the source list of the cc_library. This way, the C++ implementation
- and the C wrapper are both available in the cc_library.
+ This macro creates an internal cc_library that can be used to test this
+ function, and creates filegroups required to include this function into
+ a release build of libc.
Args:
name: Target name. It is normally the name of the function this target is
for.
- srcs: The .cpp files which contain the function implementation.
weak: Make the symbol corresponding to the libc function "weak".
- copts: The list of options to add to the C++ compilation command.
- local_defines: The preprocessor defines which will be prepended with -D
- and passed to the compile command of this target but not
- its deps.
**kwargs: Other attributes relevant for a cc_library. For example, deps.
"""
- # We compile the code twice, the first target is suffixed with ".__internal__" and contains the
+ # Build "internal" library with a function, the target has ".__internal__" suffix and contains
# C++ functions in the "LIBC_NAMESPACE" namespace. This allows us to test the function in the
# presence of another libc.
- libc_support_library(
+ _libc_library(
name = libc_internal_target(name),
- srcs = srcs,
- copts = copts,
- local_defines = local_defines,
**kwargs
)
+ _libc_library_filegroups(name = name, is_function = True, **kwargs)
+
+
+ # TODO(PR #130327): Remove this after downstream uses are migrated to libc_release_library.
# This second target is the llvm libc C function with default visibility.
func_attrs = [
"LLVM_LIBC_FUNCTION_ATTR_" + name + "='LLVM_LIBC_EMPTY, [[gnu::weak]]'",
@@ -115,9 +137,49 @@ def libc_function(
_libc_library(
name = name,
- srcs = srcs,
- copts = copts + libc_release_copts(),
- local_defines = local_defines + func_attrs,
+ copts = libc_release_copts(),
+ local_defines = func_attrs,
+ **kwargs
+ )
+
+def libc_release_library(
+ name,
+ libc_functions,
+ weak_symbols = [],
+ **kwargs):
+ """Create the release version of a libc library.
+
+ Args:
+ name: Name of the cc_library target.
+ libc_functions: List of functions to include in the library. They should be
+ created by libc_function macro.
+ weak_symbols: List of function names that should be marked as weak symbols.
+ **kwargs: Other arguments relevant to cc_library.
+ """
+ # Combine all sources into a single filegroup to avoid repeated sources error.
+ native.filegroup(
+ name = name + "_srcs",
+ srcs = [function + "_fn_srcs" for function in libc_functions],
+ )
+
+ native.cc_library(
+ name = name + "_textual_hdr_library",
+ textual_hdrs = [function + "_fn_textual_hdrs" for function in libc_functions],
+ )
+
+ weak_attributes = [
+ "LLVM_LIBC_FUNCTION_ATTR_" + name + "='LLVM_LIBC_EMPTY, [[gnu::weak]]'"
+ for name in weak_symbols
+ ]
+
+ native.cc_library(
+ name = name,
+ srcs = [":" + name + "_srcs"],
+ copts = libc_common_copts() + libc_release_copts(),
+ local_defines = weak_attributes + LIBC_CONFIGURE_OPTIONS,
+ deps = [
+ ":" + name + "_textual_hdr_library",
+ ],
**kwargs
)
diff --git a/utils/bazel/llvm-project-overlay/libc/test/BUILD.bazel b/utils/bazel/llvm-project-overlay/libc/test/BUILD.bazel
index 70b0196469eca..ac9689713fea4 100644
--- a/utils/bazel/llvm-project-overlay/libc/test/BUILD.bazel
+++ b/utils/bazel/llvm-project-overlay/libc/test/BUILD.bazel
@@ -2,6 +2,26 @@
# See https://llvm.org/LICENSE.txt for license information.
# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+load("@bazel_skylib//rules:build_test.bzl", "build_test")
+load("//libc:libc_build_rules.bzl", "libc_release_library")
+
package(default_visibility = ["//visibility:public"])
exports_files(["libc_test_rules.bzl"])
+
+# Sanity check that libc_release_library macro works as intended.
+libc_release_library(
+ name = "libc_release_test",
+ libc_functions = [
+ "//libc:acosf",
+ "//libc:read",
+ ],
+ weak_symbols = [
+ "read",
+ ],
+)
+
+build_test(
+ name = "libc_release_test_build",
+ targets = [":libc_release_test"],
+)
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Joseph, could you elaborate? Do you suggest taking the list of sources/headers required to build a particular set of targets from the cache file CMake constructs? That probably wouldn't work in the Bazel world, where the CMake is never executed. |
I just mean if we have special release configurations if that's something we should export through CMake as well. |
Ah, OK. I would defer to @michaelrj-google and @lntue here, but I believe that CMake is somewhat ahead in terms of "release configuration" support? E.g. it has a concept and implementation of OS/arch-specific entrypoints and sets of headers under /libc/config. Up to this point, Bazel has no way of assembling a list of standalone libc functions into something like "library", this CL is a first small step towards doing that. |
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I don't think we currently have a way for CMake to build all of the library targets as one massive library, right now it's all individual targets that get combined into a |
See PR #130327 for background and motivation. This change expands the libc_support_library and libc_function rules to create filegroups that allow building a collection of llvm-libc functions together, from sources, as a part of a single cc_library that can then be used by the downstream clients.
This change also adds an example use of this macro under libc/test/BUILD.bazel to confirm that this macro works as expected.