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This is the first step to having Clang's runtime libraries fully available for the Carbon toolchain. This PR focuses on the lowest level runtimes, the CRT files and the builtins library. The goal is to intercept Clang runs where it needs these target-dependent pieces to be available, and build them on demand using our Clang-running infrastructure. This avoids most of the subprocess overhead, but there is still some due to missing features in Clang. This requires exporting the sources for these runtimes from the Bazel build, and installing them in our target-independent resource directory. We then build a simplified "build" of these sources within the `ClangRunner` itself to produce the specific artifacts and layout expected by Clang. It also required fixing our use of Clang on macOS to have a default system root in order to successfully compile or link. It also required cleaning up how the `ClangRunner` used target information more generally -- instead of taking the target as a constructor parameter, it manages its target internally and relies on the Clang target-specifying command line flags. I looked at whether we could split this into another layer separate from the `ClangRunner`, but that proved frustratingly difficult to manage. While we support building these on-demand as part of a detected link, that doesn't seem feasible as we don't have the necessary separation between compilation runs of Clang and link runs of Clang. However, I have tried to factor the internals to provide as clear of separation as I could across these. I have also created a stand-alone subcommand to directly build the runtimes which allows for easy testing. It also supports building them into a specific directory, and that directory can in turn be passed to a Clang invocation. This is designed to work both at the API level with `ClangRunner` and at the subcommand level. Currently, the only part of the commandline that is detected and forwarded to the runtimes build is the target. Eventually, the plan is to expand this so that we can build a maximally tailored set of runtimes for a given compilation. The other big TODO here is to actually implement caching storage of these runtimes so they aren't built on every execution. Right now, this uses a somewhat hack-y build of a temporary directory, but this isn't expected to be suitable long-term. Building these runtimes on *every* link makes those commands take approximately 15 seconds with an ASan build like our default development build, and just over 2 seconds in an optimized build. Because of this, I've kept all of this disabled by default for now. The goal is that once caching and some other improvements land, we can enable this by default. --------- Co-authored-by: Jon Ross-Perkins <jperkins@google.com> Co-authored-by: Richard Smith <richard@metafoo.co.uk>
123 lines
4.2 KiB
C++
123 lines
4.2 KiB
C++
// Part of the Carbon Language project, under the Apache License v2.0 with LLVM
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// Exceptions. See /LICENSE for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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#include "toolchain/driver/clang_subcommand.h"
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#include <string>
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#include "llvm/TargetParser/Host.h"
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#include "toolchain/driver/clang_runner.h"
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namespace Carbon {
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auto ClangOptions::Build(CommandLine::CommandBuilder& b) -> void {
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b.AddStringOption(
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{
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.name = "prebuilt-runtimes",
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.value_name = "PATH",
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.help = R"""(
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Path to prebuilt target runtimes for Clang.
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If this option is provided, runtimes will not be built on demand and this path
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will be used instead.
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)""",
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},
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[&](auto& arg_b) { arg_b.Set(&prebuilt_runtimes_path); });
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b.AddFlag(
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{
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.name = "build-runtimes",
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.help = R"""(
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Enables on-demand building of target-specific runtimes.
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When enabled, any link actions using `clang` will build the necessary runtimes
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on-demand. This build will use any customization it can from the link command
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line flags to build the runtimes for the correct target and with any desired
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features enabled.
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Note: this only has an effect when `--prebuilt-runtimes` are not provided. If
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there are no prebuilt runtimes and building runtimes is disabled, then it is
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assumed the installed toolchain has had the necessary target runtimes added to
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the installation tree in the default searched locations.
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)""",
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},
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[&](auto& arg_b) {
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// TODO: Once runtimes are cached properly, the plan is to enable this
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// by default.
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arg_b.Default(false);
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arg_b.Set(&build_runtimes_on_demand);
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});
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b.AddStringPositionalArg(
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{
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.name = "ARG",
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.help = R"""(
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Arguments passed to Clang.
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)""",
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},
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[&](auto& arg_b) { arg_b.Append(&args); });
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}
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static constexpr CommandLine::CommandInfo SubcommandInfo = {
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.name = "clang",
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.help = R"""(
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Runs Clang on arguments.
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This is equivalent to running the `clang` command line directly, and provides
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the full command line interface.
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Use `carbon clang -- ARGS` to pass flags to `clang`. Although there are
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currently no flags for `carbon clang`, the `--` reserves the ability to add
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flags in the future.
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This is provided to help guarantee consistent compilation of C++ files, both
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when Clang is invoked directly and when a Carbon file importing a C++ file
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results in an indirect Clang invocation.
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)""",
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};
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ClangSubcommand::ClangSubcommand() : DriverSubcommand(SubcommandInfo) {}
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// TODO: This lacks a lot of features from the main driver code. We may need to
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// add more.
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// https://github.com/llvm/llvm-project/blob/main/clang/tools/driver/driver.cpp
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auto ClangSubcommand::Run(DriverEnv& driver_env) -> DriverResult {
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ClangRunner runner(
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driver_env.installation, driver_env.fs, driver_env.vlog_stream,
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/*build_runtimes_on_demand=*/options_.build_runtimes_on_demand);
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// Don't run Clang when fuzzing, it is known to not be reliable under fuzzing
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// due to many unfixed issues.
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if (TestAndDiagnoseIfFuzzingExternalLibraries(driver_env, "clang")) {
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return {.success = false};
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}
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// Only enable Clang's leaking of memory if the driver can support that.
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if (driver_env.enable_leaking) {
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runner.EnableLeakingMemory();
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}
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std::optional<std::filesystem::path> prebuilt_resource_dir_path;
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if (!options_.prebuilt_runtimes_path.empty()) {
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prebuilt_resource_dir_path = options_.prebuilt_runtimes_path.str();
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// TODO: Replace the hard coded `clang_resource_dir` subdirectory here with
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// an abstraction that manages the layout of the built runtimes.
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*prebuilt_resource_dir_path /= "clang_resource_dir";
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}
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ErrorOr<bool> run_result =
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runner.Run(options_.args, prebuilt_resource_dir_path);
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if (!run_result.ok()) {
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// This is not a Clang failure, but a failure to even run Clang, so we need
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// to diagnose it here.
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CARBON_DIAGNOSTIC(FailureRunningClang, Error,
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"failure running `clang` subcommand: {0}", std::string);
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driver_env.emitter.Emit(FailureRunningClang, run_result.error().message());
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return {.success = false};
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}
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// Successfully ran Clang, but return whether Clang itself succeeded.
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return {.success = *run_result};
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}
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} // namespace Carbon
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