mirror of
https://github.com/rust-lang/rust.git
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844 lines
35 KiB
Rust
844 lines
35 KiB
Rust
use std::collections::VecDeque;
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use std::ffi::{CStr, CString};
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use std::fmt::Write;
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use std::path::Path;
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use std::sync::Once;
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use std::{ptr, slice, str};
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use libc::c_int;
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use rustc_codegen_ssa::base::wants_wasm_eh;
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use rustc_codegen_ssa::codegen_attrs::check_tied_features;
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use rustc_data_structures::fx::{FxHashMap, FxHashSet};
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use rustc_data_structures::small_c_str::SmallCStr;
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use rustc_data_structures::unord::UnordSet;
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use rustc_fs_util::path_to_c_string;
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use rustc_middle::bug;
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use rustc_session::Session;
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use rustc_session::config::{PrintKind, PrintRequest};
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use rustc_span::Symbol;
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use rustc_target::spec::{MergeFunctions, PanicStrategy, SmallDataThresholdSupport};
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use rustc_target::target_features::{RUSTC_SPECIAL_FEATURES, RUSTC_SPECIFIC_FEATURES};
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use crate::back::write::create_informational_target_machine;
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use crate::errors::{
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FixedX18InvalidArch, ForbiddenCTargetFeature, PossibleFeature, UnknownCTargetFeature,
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UnknownCTargetFeaturePrefix, UnstableCTargetFeature,
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};
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use crate::llvm;
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static INIT: Once = Once::new();
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pub(crate) fn init(sess: &Session) {
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unsafe {
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// Before we touch LLVM, make sure that multithreading is enabled.
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if llvm::LLVMIsMultithreaded() != 1 {
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bug!("LLVM compiled without support for threads");
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}
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INIT.call_once(|| {
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configure_llvm(sess);
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});
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}
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}
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fn require_inited() {
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if !INIT.is_completed() {
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bug!("LLVM is not initialized");
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}
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}
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unsafe fn configure_llvm(sess: &Session) {
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let n_args = sess.opts.cg.llvm_args.len() + sess.target.llvm_args.len();
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let mut llvm_c_strs = Vec::with_capacity(n_args + 1);
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let mut llvm_args = Vec::with_capacity(n_args + 1);
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unsafe {
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llvm::LLVMRustInstallErrorHandlers();
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}
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// On Windows, an LLVM assertion will open an Abort/Retry/Ignore dialog
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// box for the purpose of launching a debugger. However, on CI this will
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// cause it to hang until it times out, which can take several hours.
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if std::env::var_os("CI").is_some() {
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unsafe {
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llvm::LLVMRustDisableSystemDialogsOnCrash();
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}
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}
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fn llvm_arg_to_arg_name(full_arg: &str) -> &str {
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full_arg.trim().split(|c: char| c == '=' || c.is_whitespace()).next().unwrap_or("")
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}
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let cg_opts = sess.opts.cg.llvm_args.iter().map(AsRef::as_ref);
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let tg_opts = sess.target.llvm_args.iter().map(AsRef::as_ref);
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let sess_args = cg_opts.chain(tg_opts);
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let user_specified_args: FxHashSet<_> =
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sess_args.clone().map(|s| llvm_arg_to_arg_name(s)).filter(|s| !s.is_empty()).collect();
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{
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// This adds the given argument to LLVM. Unless `force` is true
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// user specified arguments are *not* overridden.
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let mut add = |arg: &str, force: bool| {
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if force || !user_specified_args.contains(llvm_arg_to_arg_name(arg)) {
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let s = CString::new(arg).unwrap();
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llvm_args.push(s.as_ptr());
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llvm_c_strs.push(s);
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}
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};
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// Set the llvm "program name" to make usage and invalid argument messages more clear.
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add("rustc -Cllvm-args=\"...\" with", true);
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if sess.opts.unstable_opts.time_llvm_passes {
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add("-time-passes", false);
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}
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if sess.opts.unstable_opts.print_llvm_passes {
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add("-debug-pass=Structure", false);
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}
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if sess.target.generate_arange_section
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&& !sess.opts.unstable_opts.no_generate_arange_section
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{
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add("-generate-arange-section", false);
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}
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match sess.opts.unstable_opts.merge_functions.unwrap_or(sess.target.merge_functions) {
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MergeFunctions::Disabled | MergeFunctions::Trampolines => {}
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MergeFunctions::Aliases => {
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add("-mergefunc-use-aliases", false);
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}
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}
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if wants_wasm_eh(sess) {
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add("-wasm-enable-eh", false);
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}
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if sess.target.os == "emscripten" && sess.panic_strategy() == PanicStrategy::Unwind {
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add("-enable-emscripten-cxx-exceptions", false);
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}
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// HACK(eddyb) LLVM inserts `llvm.assume` calls to preserve align attributes
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// during inlining. Unfortunately these may block other optimizations.
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add("-preserve-alignment-assumptions-during-inlining=false", false);
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// Use non-zero `import-instr-limit` multiplier for cold callsites.
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add("-import-cold-multiplier=0.1", false);
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if sess.print_llvm_stats() {
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add("-stats", false);
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}
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for arg in sess_args {
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add(&(*arg), true);
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}
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match (
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sess.opts.unstable_opts.small_data_threshold,
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sess.target.small_data_threshold_support(),
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) {
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// Set up the small-data optimization limit for architectures that use
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// an LLVM argument to control this.
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(Some(threshold), SmallDataThresholdSupport::LlvmArg(arg)) => {
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add(&format!("--{arg}={threshold}"), false)
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}
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_ => (),
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};
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}
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if sess.opts.unstable_opts.llvm_time_trace {
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unsafe { llvm::LLVMRustTimeTraceProfilerInitialize() };
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}
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rustc_llvm::initialize_available_targets();
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unsafe { llvm::LLVMRustSetLLVMOptions(llvm_args.len() as c_int, llvm_args.as_ptr()) };
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}
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pub(crate) fn time_trace_profiler_finish(file_name: &Path) {
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unsafe {
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let file_name = path_to_c_string(file_name);
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llvm::LLVMRustTimeTraceProfilerFinish(file_name.as_ptr());
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}
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}
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enum TargetFeatureFoldStrength<'a> {
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// The feature is only tied when enabling the feature, disabling
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// this feature shouldn't disable the tied feature.
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EnableOnly(&'a str),
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// The feature is tied for both enabling and disabling this feature.
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Both(&'a str),
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}
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impl<'a> TargetFeatureFoldStrength<'a> {
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fn as_str(&self) -> &'a str {
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match self {
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TargetFeatureFoldStrength::EnableOnly(feat) => feat,
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TargetFeatureFoldStrength::Both(feat) => feat,
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}
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}
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}
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pub(crate) struct LLVMFeature<'a> {
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llvm_feature_name: &'a str,
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dependency: Option<TargetFeatureFoldStrength<'a>>,
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}
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impl<'a> LLVMFeature<'a> {
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fn new(llvm_feature_name: &'a str) -> Self {
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Self { llvm_feature_name, dependency: None }
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}
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fn with_dependency(
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llvm_feature_name: &'a str,
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dependency: TargetFeatureFoldStrength<'a>,
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) -> Self {
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Self { llvm_feature_name, dependency: Some(dependency) }
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}
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fn contains(&self, feat: &str) -> bool {
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self.iter().any(|dep| dep == feat)
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}
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fn iter(&'a self) -> impl Iterator<Item = &'a str> {
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let dependencies = self.dependency.iter().map(|feat| feat.as_str());
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std::iter::once(self.llvm_feature_name).chain(dependencies)
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}
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}
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impl<'a> IntoIterator for LLVMFeature<'a> {
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type Item = &'a str;
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type IntoIter = impl Iterator<Item = &'a str>;
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fn into_iter(self) -> Self::IntoIter {
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let dependencies = self.dependency.into_iter().map(|feat| feat.as_str());
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std::iter::once(self.llvm_feature_name).chain(dependencies)
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}
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}
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// WARNING: the features after applying `to_llvm_features` must be known
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// to LLVM or the feature detection code will walk past the end of the feature
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// array, leading to crashes.
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//
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// To find a list of LLVM's names, see llvm-project/llvm/lib/Target/{ARCH}/*.td
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// where `{ARCH}` is the architecture name. Look for instances of `SubtargetFeature`.
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//
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// Check the current rustc fork of LLVM in the repo at https://github.com/rust-lang/llvm-project/.
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// The commit in use can be found via the `llvm-project` submodule in
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// https://github.com/rust-lang/rust/tree/master/src Though note that Rust can also be build with
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// an external precompiled version of LLVM which might lead to failures if the oldest tested /
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// supported LLVM version doesn't yet support the relevant intrinsics.
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pub(crate) fn to_llvm_features<'a>(sess: &Session, s: &'a str) -> Option<LLVMFeature<'a>> {
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let arch = if sess.target.arch == "x86_64" {
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"x86"
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} else if sess.target.arch == "arm64ec" {
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"aarch64"
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} else if sess.target.arch == "sparc64" {
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"sparc"
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} else if sess.target.arch == "powerpc64" {
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"powerpc"
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} else {
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&*sess.target.arch
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};
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match (arch, s) {
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("x86", "sse4.2") => Some(LLVMFeature::with_dependency(
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"sse4.2",
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TargetFeatureFoldStrength::EnableOnly("crc32"),
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)),
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("x86", "pclmulqdq") => Some(LLVMFeature::new("pclmul")),
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("x86", "rdrand") => Some(LLVMFeature::new("rdrnd")),
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("x86", "bmi1") => Some(LLVMFeature::new("bmi")),
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("x86", "cmpxchg16b") => Some(LLVMFeature::new("cx16")),
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("x86", "lahfsahf") => Some(LLVMFeature::new("sahf")),
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("aarch64", "rcpc2") => Some(LLVMFeature::new("rcpc-immo")),
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("aarch64", "dpb") => Some(LLVMFeature::new("ccpp")),
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("aarch64", "dpb2") => Some(LLVMFeature::new("ccdp")),
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("aarch64", "frintts") => Some(LLVMFeature::new("fptoint")),
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("aarch64", "fcma") => Some(LLVMFeature::new("complxnum")),
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("aarch64", "pmuv3") => Some(LLVMFeature::new("perfmon")),
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("aarch64", "paca") => Some(LLVMFeature::new("pauth")),
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("aarch64", "pacg") => Some(LLVMFeature::new("pauth")),
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("aarch64", "pauth-lr") if get_version().0 < 19 => None,
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// Before LLVM 20 those two features were packaged together as b16b16
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("aarch64", "sve-b16b16") if get_version().0 < 20 => Some(LLVMFeature::new("b16b16")),
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("aarch64", "sme-b16b16") if get_version().0 < 20 => Some(LLVMFeature::new("b16b16")),
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("aarch64", "flagm2") => Some(LLVMFeature::new("altnzcv")),
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// Rust ties fp and neon together.
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("aarch64", "neon") => {
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Some(LLVMFeature::with_dependency("neon", TargetFeatureFoldStrength::Both("fp-armv8")))
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}
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// In LLVM neon implicitly enables fp, but we manually enable
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// neon when a feature only implicitly enables fp
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("aarch64", "fhm") => Some(LLVMFeature::new("fp16fml")),
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("aarch64", "fp16") => Some(LLVMFeature::new("fullfp16")),
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// Filter out features that are not supported by the current LLVM version
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("aarch64", "fpmr") if get_version().0 != 18 => None,
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// In LLVM 18, `unaligned-scalar-mem` was merged with `unaligned-vector-mem` into a single
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// feature called `fast-unaligned-access`. In LLVM 19, it was split back out.
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("riscv32" | "riscv64", "unaligned-scalar-mem") if get_version().0 == 18 => {
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Some(LLVMFeature::new("fast-unaligned-access"))
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}
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// Filter out features that are not supported by the current LLVM version
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("riscv32" | "riscv64", "zaamo") if get_version().0 < 19 => None,
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("riscv32" | "riscv64", "zabha") if get_version().0 < 19 => None,
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("riscv32" | "riscv64", "zalrsc") if get_version().0 < 19 => None,
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// Enable the evex512 target feature if an avx512 target feature is enabled.
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("x86", s) if s.starts_with("avx512") => {
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Some(LLVMFeature::with_dependency(s, TargetFeatureFoldStrength::EnableOnly("evex512")))
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}
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// Support for `wide-arithmetic` will first land in LLVM 20 as part of
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// llvm/llvm-project#111598
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("wasm32" | "wasm64", "wide-arithmetic") if get_version() < (20, 0, 0) => None,
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("sparc", "leoncasa") => Some(LLVMFeature::new("hasleoncasa")),
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// In LLVM 19, there is no `v8plus` feature and `v9` means "SPARC-V9 instruction available and SPARC-V8+ ABI used".
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// https://github.com/llvm/llvm-project/blob/llvmorg-19.1.0/llvm/lib/Target/Sparc/MCTargetDesc/SparcELFObjectWriter.cpp#L27-L28
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// Before LLVM 19, there is no `v8plus` feature and `v9` means "SPARC-V9 instruction available".
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// https://github.com/llvm/llvm-project/blob/llvmorg-18.1.0/llvm/lib/Target/Sparc/MCTargetDesc/SparcELFObjectWriter.cpp#L26
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("sparc", "v8plus") if get_version().0 == 19 => Some(LLVMFeature::new("v9")),
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("sparc", "v8plus") if get_version().0 < 19 => None,
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("powerpc", "power8-crypto") => Some(LLVMFeature::new("crypto")),
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(_, s) => Some(LLVMFeature::new(s)),
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}
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}
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/// Used to generate cfg variables and apply features.
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/// Must express features in the way Rust understands them.
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///
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/// We do not have to worry about RUSTC_SPECIFIC_FEATURES here, those are handled outside codegen.
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pub fn target_features_cfg(sess: &Session, allow_unstable: bool) -> Vec<Symbol> {
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let mut features: FxHashSet<Symbol> = Default::default();
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// Add base features for the target.
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// We do *not* add the -Ctarget-features there, and instead duplicate the logic for that below.
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// The reason is that if LLVM considers a feature implied but we do not, we don't want that to
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// show up in `cfg`. That way, `cfg` is entirely under our control -- except for the handling of
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// the target CPU, that is still expanded to target features (with all their implied features) by
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// LLVM.
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let target_machine = create_informational_target_machine(sess, true);
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// Compute which of the known target features are enabled in the 'base' target machine.
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// We only consider "supported" features; "forbidden" features are not reflected in `cfg` as of now.
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features.extend(
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sess.target
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.rust_target_features()
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.iter()
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.filter(|(_, gate, _)| gate.in_cfg())
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.filter(|(feature, _, _)| {
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// skip checking special features, as LLVM may not understand them
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if RUSTC_SPECIAL_FEATURES.contains(feature) {
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return true;
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}
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// check that all features in a given smallvec are enabled
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if let Some(feat) = to_llvm_features(sess, feature) {
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for llvm_feature in feat {
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let cstr = SmallCStr::new(llvm_feature);
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if !unsafe { llvm::LLVMRustHasFeature(&target_machine, cstr.as_ptr()) } {
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return false;
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}
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}
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true
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} else {
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false
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}
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})
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.map(|(feature, _, _)| Symbol::intern(feature)),
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);
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// Add enabled features
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for (enabled, feature) in
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sess.opts.cg.target_feature.split(',').filter_map(|s| match s.chars().next() {
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Some('+') => Some((true, Symbol::intern(&s[1..]))),
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Some('-') => Some((false, Symbol::intern(&s[1..]))),
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_ => None,
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})
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{
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if enabled {
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// Also add all transitively implied features.
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// We don't care about the order in `features` since the only thing we use it for is the
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// `features.contains` below.
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#[allow(rustc::potential_query_instability)]
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features.extend(
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sess.target
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.implied_target_features(std::iter::once(feature.as_str()))
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.iter()
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.map(|s| Symbol::intern(s)),
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);
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} else {
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// Remove transitively reverse-implied features.
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|
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// We don't care about the order in `features` since the only thing we use it for is the
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// `features.contains` below.
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#[allow(rustc::potential_query_instability)]
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features.retain(|f| {
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if sess
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.target
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.implied_target_features(std::iter::once(f.as_str()))
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.contains(&feature.as_str())
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{
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// If `f` if implies `feature`, then `!feature` implies `!f`, so we have to
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// remove `f`. (This is the standard logical contraposition principle.)
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false
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} else {
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// We can keep `f`.
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true
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}
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});
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}
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}
|
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|
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// Filter enabled features based on feature gates
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sess.target
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.rust_target_features()
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.iter()
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.filter(|(_, gate, _)| gate.in_cfg())
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.filter_map(|(feature, gate, _)| {
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if sess.is_nightly_build() || allow_unstable || gate.requires_nightly().is_none() {
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Some(*feature)
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} else {
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None
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}
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})
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.filter(|feature| features.contains(&Symbol::intern(feature)))
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.map(|feature| Symbol::intern(feature))
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.collect()
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}
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|
|
pub(crate) fn print_version() {
|
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let (major, minor, patch) = get_version();
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println!("LLVM version: {major}.{minor}.{patch}");
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}
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pub(crate) fn get_version() -> (u32, u32, u32) {
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// Can be called without initializing LLVM
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unsafe {
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(llvm::LLVMRustVersionMajor(), llvm::LLVMRustVersionMinor(), llvm::LLVMRustVersionPatch())
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}
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}
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|
|
pub(crate) fn print_passes() {
|
|
// Can be called without initializing LLVM
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|
unsafe {
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llvm::LLVMRustPrintPasses();
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}
|
|
}
|
|
|
|
fn llvm_target_features(tm: &llvm::TargetMachine) -> Vec<(&str, &str)> {
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|
let len = unsafe { llvm::LLVMRustGetTargetFeaturesCount(tm) };
|
|
let mut ret = Vec::with_capacity(len);
|
|
for i in 0..len {
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unsafe {
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let mut feature = ptr::null();
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let mut desc = ptr::null();
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|
llvm::LLVMRustGetTargetFeature(tm, i, &mut feature, &mut desc);
|
|
if feature.is_null() || desc.is_null() {
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bug!("LLVM returned a `null` target feature string");
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}
|
|
let feature = CStr::from_ptr(feature).to_str().unwrap_or_else(|e| {
|
|
bug!("LLVM returned a non-utf8 feature string: {}", e);
|
|
});
|
|
let desc = CStr::from_ptr(desc).to_str().unwrap_or_else(|e| {
|
|
bug!("LLVM returned a non-utf8 feature string: {}", e);
|
|
});
|
|
ret.push((feature, desc));
|
|
}
|
|
}
|
|
ret
|
|
}
|
|
|
|
pub(crate) fn print(req: &PrintRequest, out: &mut String, sess: &Session) {
|
|
require_inited();
|
|
let tm = create_informational_target_machine(sess, false);
|
|
match req.kind {
|
|
PrintKind::TargetCPUs => print_target_cpus(sess, &tm, out),
|
|
PrintKind::TargetFeatures => print_target_features(sess, &tm, out),
|
|
_ => bug!("rustc_codegen_llvm can't handle print request: {:?}", req),
|
|
}
|
|
}
|
|
|
|
fn print_target_cpus(sess: &Session, tm: &llvm::TargetMachine, out: &mut String) {
|
|
let cpu_names = llvm::build_string(|s| unsafe {
|
|
llvm::LLVMRustPrintTargetCPUs(&tm, s);
|
|
})
|
|
.unwrap();
|
|
|
|
struct Cpu<'a> {
|
|
cpu_name: &'a str,
|
|
remark: String,
|
|
}
|
|
// Compare CPU against current target to label the default.
|
|
let target_cpu = handle_native(&sess.target.cpu);
|
|
let make_remark = |cpu_name| {
|
|
if cpu_name == target_cpu {
|
|
// FIXME(#132514): This prints the LLVM target string, which can be
|
|
// different from the Rust target string. Is that intended?
|
|
let target = &sess.target.llvm_target;
|
|
format!(
|
|
" - This is the default target CPU for the current build target (currently {target})."
|
|
)
|
|
} else {
|
|
"".to_owned()
|
|
}
|
|
};
|
|
let mut cpus = cpu_names
|
|
.lines()
|
|
.map(|cpu_name| Cpu { cpu_name, remark: make_remark(cpu_name) })
|
|
.collect::<VecDeque<_>>();
|
|
|
|
// Only print the "native" entry when host and target are the same arch,
|
|
// since otherwise it could be wrong or misleading.
|
|
if sess.host.arch == sess.target.arch {
|
|
let host = get_host_cpu_name();
|
|
cpus.push_front(Cpu {
|
|
cpu_name: "native",
|
|
remark: format!(" - Select the CPU of the current host (currently {host})."),
|
|
});
|
|
}
|
|
|
|
let max_name_width = cpus.iter().map(|cpu| cpu.cpu_name.len()).max().unwrap_or(0);
|
|
writeln!(out, "Available CPUs for this target:").unwrap();
|
|
for Cpu { cpu_name, remark } in cpus {
|
|
// Only pad the CPU name if there's a remark to print after it.
|
|
let width = if remark.is_empty() { 0 } else { max_name_width };
|
|
writeln!(out, " {cpu_name:<width$}{remark}").unwrap();
|
|
}
|
|
}
|
|
|
|
fn print_target_features(sess: &Session, tm: &llvm::TargetMachine, out: &mut String) {
|
|
let mut llvm_target_features = llvm_target_features(tm);
|
|
let mut known_llvm_target_features = FxHashSet::<&'static str>::default();
|
|
let mut rustc_target_features = sess
|
|
.target
|
|
.rust_target_features()
|
|
.iter()
|
|
.filter_map(|(feature, gate, _implied)| {
|
|
if !gate.in_cfg() {
|
|
// Only list (experimentally) supported features.
|
|
return None;
|
|
}
|
|
// LLVM asserts that these are sorted. LLVM and Rust both use byte comparison for these
|
|
// strings.
|
|
let llvm_feature = to_llvm_features(sess, *feature)?.llvm_feature_name;
|
|
let desc =
|
|
match llvm_target_features.binary_search_by_key(&llvm_feature, |(f, _d)| f).ok() {
|
|
Some(index) => {
|
|
known_llvm_target_features.insert(llvm_feature);
|
|
llvm_target_features[index].1
|
|
}
|
|
None => "",
|
|
};
|
|
|
|
Some((*feature, desc))
|
|
})
|
|
.collect::<Vec<_>>();
|
|
|
|
// Since we add this at the end ...
|
|
rustc_target_features.extend_from_slice(&[(
|
|
"crt-static",
|
|
"Enables C Run-time Libraries to be statically linked",
|
|
)]);
|
|
// ... we need to sort the list again.
|
|
rustc_target_features.sort();
|
|
|
|
llvm_target_features.retain(|(f, _d)| !known_llvm_target_features.contains(f));
|
|
|
|
let max_feature_len = llvm_target_features
|
|
.iter()
|
|
.chain(rustc_target_features.iter())
|
|
.map(|(feature, _desc)| feature.len())
|
|
.max()
|
|
.unwrap_or(0);
|
|
|
|
writeln!(out, "Features supported by rustc for this target:").unwrap();
|
|
for (feature, desc) in &rustc_target_features {
|
|
writeln!(out, " {feature:max_feature_len$} - {desc}.").unwrap();
|
|
}
|
|
writeln!(out, "\nCode-generation features supported by LLVM for this target:").unwrap();
|
|
for (feature, desc) in &llvm_target_features {
|
|
writeln!(out, " {feature:max_feature_len$} - {desc}.").unwrap();
|
|
}
|
|
if llvm_target_features.is_empty() {
|
|
writeln!(out, " Target features listing is not supported by this LLVM version.")
|
|
.unwrap();
|
|
}
|
|
writeln!(out, "\nUse +feature to enable a feature, or -feature to disable it.").unwrap();
|
|
writeln!(out, "For example, rustc -C target-cpu=mycpu -C target-feature=+feature1,-feature2\n")
|
|
.unwrap();
|
|
writeln!(out, "Code-generation features cannot be used in cfg or #[target_feature],").unwrap();
|
|
writeln!(out, "and may be renamed or removed in a future version of LLVM or rustc.\n").unwrap();
|
|
}
|
|
|
|
/// Returns the host CPU name, according to LLVM.
|
|
fn get_host_cpu_name() -> &'static str {
|
|
let mut len = 0;
|
|
// SAFETY: The underlying C++ global function returns a `StringRef` that
|
|
// isn't tied to any particular backing buffer, so it must be 'static.
|
|
let slice: &'static [u8] = unsafe {
|
|
let ptr = llvm::LLVMRustGetHostCPUName(&mut len);
|
|
assert!(!ptr.is_null());
|
|
slice::from_raw_parts(ptr, len)
|
|
};
|
|
str::from_utf8(slice).expect("host CPU name should be UTF-8")
|
|
}
|
|
|
|
/// If the given string is `"native"`, returns the host CPU name according to
|
|
/// LLVM. Otherwise, the string is returned as-is.
|
|
fn handle_native(cpu_name: &str) -> &str {
|
|
match cpu_name {
|
|
"native" => get_host_cpu_name(),
|
|
_ => cpu_name,
|
|
}
|
|
}
|
|
|
|
pub(crate) fn target_cpu(sess: &Session) -> &str {
|
|
let cpu_name = sess.opts.cg.target_cpu.as_deref().unwrap_or_else(|| &sess.target.cpu);
|
|
handle_native(cpu_name)
|
|
}
|
|
|
|
/// The list of LLVM features computed from CLI flags (`-Ctarget-cpu`, `-Ctarget-feature`,
|
|
/// `--target` and similar).
|
|
pub(crate) fn global_llvm_features(
|
|
sess: &Session,
|
|
diagnostics: bool,
|
|
only_base_features: bool,
|
|
) -> Vec<String> {
|
|
// Features that come earlier are overridden by conflicting features later in the string.
|
|
// Typically we'll want more explicit settings to override the implicit ones, so:
|
|
//
|
|
// * Features from -Ctarget-cpu=*; are overridden by [^1]
|
|
// * Features implied by --target; are overridden by
|
|
// * Features from -Ctarget-feature; are overridden by
|
|
// * function specific features.
|
|
//
|
|
// [^1]: target-cpu=native is handled here, other target-cpu values are handled implicitly
|
|
// through LLVM TargetMachine implementation.
|
|
//
|
|
// FIXME(nagisa): it isn't clear what's the best interaction between features implied by
|
|
// `-Ctarget-cpu` and `--target` are. On one hand, you'd expect CLI arguments to always
|
|
// override anything that's implicit, so e.g. when there's no `--target` flag, features implied
|
|
// the host target are overridden by `-Ctarget-cpu=*`. On the other hand, what about when both
|
|
// `--target` and `-Ctarget-cpu=*` are specified? Both then imply some target features and both
|
|
// flags are specified by the user on the CLI. It isn't as clear-cut which order of precedence
|
|
// should be taken in cases like these.
|
|
let mut features = vec![];
|
|
|
|
// -Ctarget-cpu=native
|
|
match sess.opts.cg.target_cpu {
|
|
Some(ref s) if s == "native" => {
|
|
// We have already figured out the actual CPU name with `LLVMRustGetHostCPUName` and set
|
|
// that for LLVM, so the features implied by that CPU name will be available everywhere.
|
|
// However, that is not sufficient: e.g. `skylake` alone is not sufficient to tell if
|
|
// some of the instructions are available or not. So we have to also explicitly ask for
|
|
// the exact set of features available on the host, and enable all of them.
|
|
let features_string = unsafe {
|
|
let ptr = llvm::LLVMGetHostCPUFeatures();
|
|
let features_string = if !ptr.is_null() {
|
|
CStr::from_ptr(ptr)
|
|
.to_str()
|
|
.unwrap_or_else(|e| {
|
|
bug!("LLVM returned a non-utf8 features string: {}", e);
|
|
})
|
|
.to_owned()
|
|
} else {
|
|
bug!("could not allocate host CPU features, LLVM returned a `null` string");
|
|
};
|
|
|
|
llvm::LLVMDisposeMessage(ptr);
|
|
|
|
features_string
|
|
};
|
|
features.extend(features_string.split(',').map(String::from));
|
|
}
|
|
Some(_) | None => {}
|
|
};
|
|
|
|
// Features implied by an implicit or explicit `--target`.
|
|
features.extend(
|
|
sess.target
|
|
.features
|
|
.split(',')
|
|
.filter(|v| !v.is_empty())
|
|
// Drop +v8plus feature introduced in LLVM 20.
|
|
.filter(|v| *v != "+v8plus" || get_version() >= (20, 0, 0))
|
|
.map(String::from),
|
|
);
|
|
|
|
if wants_wasm_eh(sess) && sess.panic_strategy() == PanicStrategy::Unwind {
|
|
features.push("+exception-handling".into());
|
|
}
|
|
|
|
// -Ctarget-features
|
|
if !only_base_features {
|
|
let known_features = sess.target.rust_target_features();
|
|
// Will only be filled when `diagnostics` is set!
|
|
let mut featsmap = FxHashMap::default();
|
|
|
|
// Ensure that all ABI-required features are enabled, and the ABI-forbidden ones
|
|
// are disabled.
|
|
let (abi_enable, abi_disable) = sess.target.abi_required_features();
|
|
let abi_enable_set = FxHashSet::from_iter(abi_enable.iter().copied());
|
|
let abi_disable_set = FxHashSet::from_iter(abi_disable.iter().copied());
|
|
|
|
// Compute implied features
|
|
let mut all_rust_features = vec![];
|
|
for feature in sess.opts.cg.target_feature.split(',') {
|
|
if let Some(feature) = feature.strip_prefix('+') {
|
|
all_rust_features.extend(
|
|
UnordSet::from(sess.target.implied_target_features(std::iter::once(feature)))
|
|
.to_sorted_stable_ord()
|
|
.iter()
|
|
.map(|&&s| (true, s)),
|
|
)
|
|
} else if let Some(feature) = feature.strip_prefix('-') {
|
|
// FIXME: Why do we not remove implied features on "-" here?
|
|
// We do the equivalent above in `target_features_cfg`.
|
|
// See <https://github.com/rust-lang/rust/issues/134792>.
|
|
all_rust_features.push((false, feature));
|
|
} else if !feature.is_empty() {
|
|
if diagnostics {
|
|
sess.dcx().emit_warn(UnknownCTargetFeaturePrefix { feature });
|
|
}
|
|
}
|
|
}
|
|
// Remove features that are meant for rustc, not LLVM.
|
|
all_rust_features.retain(|(_, feature)| {
|
|
// Retain if it is not a rustc feature
|
|
!RUSTC_SPECIFIC_FEATURES.contains(feature)
|
|
});
|
|
|
|
// Check feature validity.
|
|
if diagnostics {
|
|
for &(enable, feature) in &all_rust_features {
|
|
let feature_state = known_features.iter().find(|&&(v, _, _)| v == feature);
|
|
match feature_state {
|
|
None => {
|
|
let rust_feature =
|
|
known_features.iter().find_map(|&(rust_feature, _, _)| {
|
|
let llvm_features = to_llvm_features(sess, rust_feature)?;
|
|
if llvm_features.contains(feature)
|
|
&& !llvm_features.contains(rust_feature)
|
|
{
|
|
Some(rust_feature)
|
|
} else {
|
|
None
|
|
}
|
|
});
|
|
let unknown_feature = if let Some(rust_feature) = rust_feature {
|
|
UnknownCTargetFeature {
|
|
feature,
|
|
rust_feature: PossibleFeature::Some { rust_feature },
|
|
}
|
|
} else {
|
|
UnknownCTargetFeature { feature, rust_feature: PossibleFeature::None }
|
|
};
|
|
sess.dcx().emit_warn(unknown_feature);
|
|
}
|
|
Some((_, stability, _)) => {
|
|
if let Err(reason) = stability.toggle_allowed() {
|
|
sess.dcx().emit_warn(ForbiddenCTargetFeature {
|
|
feature,
|
|
enabled: if enable { "enabled" } else { "disabled" },
|
|
reason,
|
|
});
|
|
} else if stability.requires_nightly().is_some() {
|
|
// An unstable feature. Warn about using it. It makes little sense
|
|
// to hard-error here since we just warn about fully unknown
|
|
// features above.
|
|
sess.dcx().emit_warn(UnstableCTargetFeature { feature });
|
|
}
|
|
}
|
|
}
|
|
|
|
// Ensure that the features we enable/disable are compatible with the ABI.
|
|
if enable {
|
|
if abi_disable_set.contains(feature) {
|
|
sess.dcx().emit_warn(ForbiddenCTargetFeature {
|
|
feature,
|
|
enabled: "enabled",
|
|
reason: "this feature is incompatible with the target ABI",
|
|
});
|
|
}
|
|
} else {
|
|
// FIXME: we have to request implied features here since
|
|
// negative features do not handle implied features above.
|
|
#[allow(rustc::potential_query_instability)] // order does not matter
|
|
for &required in abi_enable_set.iter() {
|
|
let implied =
|
|
sess.target.implied_target_features(std::iter::once(required));
|
|
if implied.contains(feature) {
|
|
sess.dcx().emit_warn(ForbiddenCTargetFeature {
|
|
feature,
|
|
enabled: "disabled",
|
|
reason: "this feature is required by the target ABI",
|
|
});
|
|
}
|
|
}
|
|
}
|
|
|
|
// FIXME(nagisa): figure out how to not allocate a full hashset here.
|
|
featsmap.insert(feature, enable);
|
|
}
|
|
}
|
|
|
|
// To be sure the ABI-relevant features are all in the right state, we explicitly
|
|
// (un)set them here. This means if the target spec sets those features wrong,
|
|
// we will silently correct them rather than silently producing wrong code.
|
|
// (The target sanity check tries to catch this, but we can't know which features are
|
|
// enabled in LLVM by default so we can't be fully sure about that check.)
|
|
// We add these at the beginning of the list so that `-Ctarget-features` can
|
|
// still override it... that's unsound, but more compatible with past behavior.
|
|
all_rust_features.splice(
|
|
0..0,
|
|
abi_enable.iter().map(|&f| (true, f)).chain(abi_disable.iter().map(|&f| (false, f))),
|
|
);
|
|
|
|
// Translate this into LLVM features.
|
|
let feats = all_rust_features
|
|
.iter()
|
|
.filter_map(|&(enable, feature)| {
|
|
let enable_disable = if enable { '+' } else { '-' };
|
|
// We run through `to_llvm_features` when
|
|
// passing requests down to LLVM. This means that all in-language
|
|
// features also work on the command line instead of having two
|
|
// different names when the LLVM name and the Rust name differ.
|
|
let llvm_feature = to_llvm_features(sess, feature)?;
|
|
|
|
Some(
|
|
std::iter::once(format!(
|
|
"{}{}",
|
|
enable_disable, llvm_feature.llvm_feature_name
|
|
))
|
|
.chain(llvm_feature.dependency.into_iter().filter_map(
|
|
move |feat| match (enable, feat) {
|
|
(_, TargetFeatureFoldStrength::Both(f))
|
|
| (true, TargetFeatureFoldStrength::EnableOnly(f)) => {
|
|
Some(format!("{enable_disable}{f}"))
|
|
}
|
|
_ => None,
|
|
},
|
|
)),
|
|
)
|
|
})
|
|
.flatten();
|
|
features.extend(feats);
|
|
|
|
if diagnostics && let Some(f) = check_tied_features(sess, &featsmap) {
|
|
sess.dcx().emit_err(rustc_codegen_ssa::errors::TargetFeatureDisableOrEnable {
|
|
features: f,
|
|
span: None,
|
|
missing_features: None,
|
|
});
|
|
}
|
|
}
|
|
|
|
// -Zfixed-x18
|
|
if sess.opts.unstable_opts.fixed_x18 {
|
|
if sess.target.arch != "aarch64" {
|
|
sess.dcx().emit_fatal(FixedX18InvalidArch { arch: &sess.target.arch });
|
|
} else {
|
|
features.push("+reserve-x18".into());
|
|
}
|
|
}
|
|
|
|
features
|
|
}
|
|
|
|
pub(crate) fn tune_cpu(sess: &Session) -> Option<&str> {
|
|
let name = sess.opts.unstable_opts.tune_cpu.as_ref()?;
|
|
Some(handle_native(name))
|
|
}
|