use std::collections::VecDeque;
use std::ffi::{CStr, CString};
use std::fmt::Write;
use std::path::Path;
use std::sync::Once;
use std::{ptr, slice, str};
use libc::c_int;
use rustc_codegen_ssa::base::wants_wasm_eh;
use rustc_codegen_ssa::codegen_attrs::check_tied_features;
use rustc_data_structures::fx::{FxHashMap, FxHashSet};
use rustc_data_structures::small_c_str::SmallCStr;
use rustc_data_structures::unord::UnordSet;
use rustc_fs_util::path_to_c_string;
use rustc_middle::bug;
use rustc_session::Session;
use rustc_session::config::{PrintKind, PrintRequest};
use rustc_span::Symbol;
use rustc_target::spec::{MergeFunctions, PanicStrategy, SmallDataThresholdSupport};
use rustc_target::target_features::{RUSTC_SPECIAL_FEATURES, RUSTC_SPECIFIC_FEATURES};
use crate::back::write::create_informational_target_machine;
use crate::errors::{
FixedX18InvalidArch, ForbiddenCTargetFeature, PossibleFeature, UnknownCTargetFeature,
UnknownCTargetFeaturePrefix, UnstableCTargetFeature,
};
use crate::llvm;
static INIT: Once = Once::new();
pub(crate) fn init(sess: &Session) {
unsafe {
// Before we touch LLVM, make sure that multithreading is enabled.
if llvm::LLVMIsMultithreaded() != 1 {
bug!("LLVM compiled without support for threads");
}
INIT.call_once(|| {
configure_llvm(sess);
});
}
}
fn require_inited() {
if !INIT.is_completed() {
bug!("LLVM is not initialized");
}
}
unsafe fn configure_llvm(sess: &Session) {
let n_args = sess.opts.cg.llvm_args.len() + sess.target.llvm_args.len();
let mut llvm_c_strs = Vec::with_capacity(n_args + 1);
let mut llvm_args = Vec::with_capacity(n_args + 1);
unsafe {
llvm::LLVMRustInstallErrorHandlers();
}
// On Windows, an LLVM assertion will open an Abort/Retry/Ignore dialog
// box for the purpose of launching a debugger. However, on CI this will
// cause it to hang until it times out, which can take several hours.
if std::env::var_os("CI").is_some() {
unsafe {
llvm::LLVMRustDisableSystemDialogsOnCrash();
}
}
fn llvm_arg_to_arg_name(full_arg: &str) -> &str {
full_arg.trim().split(|c: char| c == '=' || c.is_whitespace()).next().unwrap_or("")
}
let cg_opts = sess.opts.cg.llvm_args.iter().map(AsRef::as_ref);
let tg_opts = sess.target.llvm_args.iter().map(AsRef::as_ref);
let sess_args = cg_opts.chain(tg_opts);
let user_specified_args: FxHashSet<_> =
sess_args.clone().map(|s| llvm_arg_to_arg_name(s)).filter(|s| !s.is_empty()).collect();
{
// This adds the given argument to LLVM. Unless `force` is true
// user specified arguments are *not* overridden.
let mut add = |arg: &str, force: bool| {
if force || !user_specified_args.contains(llvm_arg_to_arg_name(arg)) {
let s = CString::new(arg).unwrap();
llvm_args.push(s.as_ptr());
llvm_c_strs.push(s);
}
};
// Set the llvm "program name" to make usage and invalid argument messages more clear.
add("rustc -Cllvm-args=\"...\" with", true);
if sess.opts.unstable_opts.time_llvm_passes {
add("-time-passes", false);
}
if sess.opts.unstable_opts.print_llvm_passes {
add("-debug-pass=Structure", false);
}
if sess.target.generate_arange_section
&& !sess.opts.unstable_opts.no_generate_arange_section
{
add("-generate-arange-section", false);
}
match sess.opts.unstable_opts.merge_functions.unwrap_or(sess.target.merge_functions) {
MergeFunctions::Disabled | MergeFunctions::Trampolines => {}
MergeFunctions::Aliases => {
add("-mergefunc-use-aliases", false);
}
}
if wants_wasm_eh(sess) {
add("-wasm-enable-eh", false);
}
if sess.target.os == "emscripten"
&& !sess.opts.unstable_opts.emscripten_wasm_eh
&& sess.panic_strategy() == PanicStrategy::Unwind
{
add("-enable-emscripten-cxx-exceptions", false);
}
// HACK(eddyb) LLVM inserts `llvm.assume` calls to preserve align attributes
// during inlining. Unfortunately these may block other optimizations.
add("-preserve-alignment-assumptions-during-inlining=false", false);
// Use non-zero `import-instr-limit` multiplier for cold callsites.
add("-import-cold-multiplier=0.1", false);
if sess.print_llvm_stats() {
add("-stats", false);
}
for arg in sess_args {
add(&(*arg), true);
}
match (
sess.opts.unstable_opts.small_data_threshold,
sess.target.small_data_threshold_support(),
) {
// Set up the small-data optimization limit for architectures that use
// an LLVM argument to control this.
(Some(threshold), SmallDataThresholdSupport::LlvmArg(arg)) => {
add(&format!("--{arg}={threshold}"), false)
}
_ => (),
};
}
if sess.opts.unstable_opts.llvm_time_trace {
unsafe { llvm::LLVMRustTimeTraceProfilerInitialize() };
}
rustc_llvm::initialize_available_targets();
unsafe { llvm::LLVMRustSetLLVMOptions(llvm_args.len() as c_int, llvm_args.as_ptr()) };
}
pub(crate) fn time_trace_profiler_finish(file_name: &Path) {
unsafe {
let file_name = path_to_c_string(file_name);
llvm::LLVMRustTimeTraceProfilerFinish(file_name.as_ptr());
}
}
enum TargetFeatureFoldStrength<'a> {
// The feature is only tied when enabling the feature, disabling
// this feature shouldn't disable the tied feature.
EnableOnly(&'a str),
// The feature is tied for both enabling and disabling this feature.
Both(&'a str),
}
impl<'a> TargetFeatureFoldStrength<'a> {
fn as_str(&self) -> &'a str {
match self {
TargetFeatureFoldStrength::EnableOnly(feat) => feat,
TargetFeatureFoldStrength::Both(feat) => feat,
}
}
}
pub(crate) struct LLVMFeature<'a> {
llvm_feature_name: &'a str,
dependency: Option<TargetFeatureFoldStrength<'a>>,
}
impl<'a> LLVMFeature<'a> {
fn new(llvm_feature_name: &'a str) -> Self {
Self { llvm_feature_name, dependency: None }
}
fn with_dependency(
llvm_feature_name: &'a str,
dependency: TargetFeatureFoldStrength<'a>,
) -> Self {
Self { llvm_feature_name, dependency: Some(dependency) }
}
fn contains(&self, feat: &str) -> bool {
self.iter().any(|dep| dep == feat)
}
fn iter(&'a self) -> impl Iterator<Item = &'a str> {
let dependencies = self.dependency.iter().map(|feat| feat.as_str());
std::iter::once(self.llvm_feature_name).chain(dependencies)
}
}
impl<'a> IntoIterator for LLVMFeature<'a> {
type Item = &'a str;
type IntoIter = impl Iterator<Item = &'a str>;
fn into_iter(self) -> Self::IntoIter {
let dependencies = self.dependency.into_iter().map(|feat| feat.as_str());
std::iter::once(self.llvm_feature_name).chain(dependencies)
}
}
// WARNING: the features after applying `to_llvm_features` must be known
// to LLVM or the feature detection code will walk past the end of the feature
// array, leading to crashes.
//
// To find a list of LLVM's names, see llvm-project/llvm/lib/Target/{ARCH}/*.td
// where `{ARCH}` is the architecture name. Look for instances of `SubtargetFeature`.
//
// Check the current rustc fork of LLVM in the repo at https://github.com/rust-lang/llvm-project/.
// The commit in use can be found via the `llvm-project` submodule in
// https://github.com/rust-lang/rust/tree/master/src Though note that Rust can also be build with
// an external precompiled version of LLVM which might lead to failures if the oldest tested /
// supported LLVM version doesn't yet support the relevant intrinsics.
pub(crate) fn to_llvm_features<'a>(sess: &Session, s: &'a str) -> Option<LLVMFeature<'a>> {
let arch = if sess.target.arch == "x86_64" {
"x86"
} else if sess.target.arch == "arm64ec" {
"aarch64"
} else if sess.target.arch == "sparc64" {
"sparc"
} else if sess.target.arch == "powerpc64" {
"powerpc"
} else {
&*sess.target.arch
};
match (arch, s) {
("x86", "sse4.2") => Some(LLVMFeature::with_dependency(
"sse4.2",
TargetFeatureFoldStrength::EnableOnly("crc32"),
)),
("x86", "pclmulqdq") => Some(LLVMFeature::new("pclmul")),
("x86", "rdrand") => Some(LLVMFeature::new("rdrnd")),
("x86", "bmi1") => Some(LLVMFeature::new("bmi")),
("x86", "cmpxchg16b") => Some(LLVMFeature::new("cx16")),
("x86", "lahfsahf") => Some(LLVMFeature::new("sahf")),
("aarch64", "rcpc2") => Some(LLVMFeature::new("rcpc-immo")),
("aarch64", "dpb") => Some(LLVMFeature::new("ccpp")),
("aarch64", "dpb2") => Some(LLVMFeature::new("ccdp")),
("aarch64", "frintts") => Some(LLVMFeature::new("fptoint")),
("aarch64", "fcma") => Some(LLVMFeature::new("complxnum")),
("aarch64", "pmuv3") => Some(LLVMFeature::new("perfmon")),
("aarch64", "paca") => Some(LLVMFeature::new("pauth")),
("aarch64", "pacg") => Some(LLVMFeature::new("pauth")),
("aarch64", "pauth-lr") if get_version().0 < 19 => None,
// Before LLVM 20 those two features were packaged together as b16b16
("aarch64", "sve-b16b16") if get_version().0 < 20 => Some(LLVMFeature::new("b16b16")),
("aarch64", "sme-b16b16") if get_version().0 < 20 => Some(LLVMFeature::new("b16b16")),
("aarch64", "flagm2") => Some(LLVMFeature::new("altnzcv")),
// Rust ties fp and neon together.
("aarch64", "neon") => {
Some(LLVMFeature::with_dependency("neon", TargetFeatureFoldStrength::Both("fp-armv8")))
}
// In LLVM neon implicitly enables fp, but we manually enable
// neon when a feature only implicitly enables fp
("aarch64", "fhm") => Some(LLVMFeature::new("fp16fml")),
("aarch64", "fp16") => Some(LLVMFeature::new("fullfp16")),
// Filter out features that are not supported by the current LLVM version
("aarch64", "fpmr") if get_version().0 != 18 => None,
("arm", "fp16") => Some(LLVMFeature::new("fullfp16")),
// In LLVM 18, `unaligned-scalar-mem` was merged with `unaligned-vector-mem` into a single
// feature called `fast-unaligned-access`. In LLVM 19, it was split back out.
("riscv32" | "riscv64", "unaligned-scalar-mem") if get_version().0 == 18 => {
Some(LLVMFeature::new("fast-unaligned-access"))
}
// Filter out features that are not supported by the current LLVM version
("riscv32" | "riscv64", "zaamo") if get_version().0 < 19 => None,
("riscv32" | "riscv64", "zabha") if get_version().0 < 19 => None,
("riscv32" | "riscv64", "zalrsc") if get_version().0 < 19 => None,
("riscv32" | "riscv64", "zama16b") if get_version().0 < 19 => None,
("riscv32" | "riscv64", "zacas") if get_version().0 < 20 => None,
// Enable the evex512 target feature if an avx512 target feature is enabled.
("x86", s) if s.starts_with("avx512") => {
Some(LLVMFeature::with_dependency(s, TargetFeatureFoldStrength::EnableOnly("evex512")))
}
// Support for `wide-arithmetic` will first land in LLVM 20 as part of
// llvm/llvm-project#111598
("wasm32" | "wasm64", "wide-arithmetic") if get_version() < (20, 0, 0) => None,
("sparc", "leoncasa") => Some(LLVMFeature::new("hasleoncasa")),
// In LLVM 19, there is no `v8plus` feature and `v9` means "SPARC-V9 instruction available and SPARC-V8+ ABI used".
// https://github.com/llvm/llvm-project/blob/llvmorg-19.1.0/llvm/lib/Target/Sparc/MCTargetDesc/SparcELFObjectWriter.cpp#L27-L28
// Before LLVM 19, there is no `v8plus` feature and `v9` means "SPARC-V9 instruction available".
// https://github.com/llvm/llvm-project/blob/llvmorg-18.1.0/llvm/lib/Target/Sparc/MCTargetDesc/SparcELFObjectWriter.cpp#L26
("sparc", "v8plus") if get_version().0 == 19 => Some(LLVMFeature::new("v9")),
("sparc", "v8plus") if get_version().0 < 19 => None,
("powerpc", "power8-crypto") => Some(LLVMFeature::new("crypto")),
(_, s) => Some(LLVMFeature::new(s)),
}
}
/// Used to generate cfg variables and apply features.
/// Must express features in the way Rust understands them.
///
/// We do not have to worry about RUSTC_SPECIFIC_FEATURES here, those are handled outside codegen.
pub(crate) fn target_features_cfg(sess: &Session) -> (Vec<Symbol>, Vec<Symbol>) {
// Add base features for the target.
// We do *not* add the -Ctarget-features there, and instead duplicate the logic for that below.
// The reason is that if LLVM considers a feature implied but we do not, we don't want that to
// show up in `cfg`. That way, `cfg` is entirely under our control -- except for the handling of
// the target CPU, that is still expanded to target features (with all their implied features)
// by LLVM.
let target_machine = create_informational_target_machine(sess, true);
// Compute which of the known target features are enabled in the 'base' target machine. We only
// consider "supported" features; "forbidden" features are not reflected in `cfg` as of now.
let mut features: FxHashSet<Symbol> = sess
.target
.rust_target_features()
.iter()
.filter(|(feature, _, _)| {
// skip checking special features, as LLVM may not understand them
if RUSTC_SPECIAL_FEATURES.contains(feature) {
return true;
}
if let Some(feat) = to_llvm_features(sess, feature) {
for llvm_feature in feat {
let cstr = SmallCStr::new(llvm_feature);
// `LLVMRustHasFeature` is moderately expensive. On targets with many
// features (e.g. x86) these calls take a non-trivial fraction of runtime
// when compiling very small programs.
if !unsafe { llvm::LLVMRustHasFeature(target_machine.raw(), cstr.as_ptr()) } {
return false;
}
}
true
} else {
false
}
})
.map(|(feature, _, _)| Symbol::intern(feature))
.collect();
// Add enabled and remove disabled features.
for (enabled, feature) in
sess.opts.cg.target_feature.split(',').filter_map(|s| match s.chars().next() {
Some('+') => Some((true, Symbol::intern(&s[1..]))),
Some('-') => Some((false, Symbol::intern(&s[1..]))),
_ => None,
})
{
if enabled {
// Also add all transitively implied features.
// We don't care about the order in `features` since the only thing we use it for is the
// `features.contains` below.
#[allow(rustc::potential_query_instability)]
features.extend(
sess.target
.implied_target_features(feature.as_str())
.iter()
.map(|s| Symbol::intern(s)),
);
} else {
// Remove transitively reverse-implied features.
// We don't care about the order in `features` since the only thing we use it for is the
// `features.contains` below.
#[allow(rustc::potential_query_instability)]
features.retain(|f| {
if sess.target.implied_target_features(f.as_str()).contains(&feature.as_str()) {
// If `f` if implies `feature`, then `!feature` implies `!f`, so we have to
// remove `f`. (This is the standard logical contraposition principle.)
false
} else {
// We can keep `f`.
true
}
});
}
}
// Filter enabled features based on feature gates.
let f = |allow_unstable| {
sess.target
.rust_target_features()
.iter()
.filter_map(|(feature, gate, _)| {
// The `allow_unstable` set is used by rustc internally to determined which target
// features are truly available, so we want to return even perma-unstable
// "forbidden" features.
if allow_unstable
|| (gate.in_cfg()
&& (sess.is_nightly_build() || gate.requires_nightly().is_none()))
{
Some(Symbol::intern(feature))
} else {
None
}
})
.filter(|feature| features.contains(&feature))
.collect()
};
let target_features = f(false);
let unstable_target_features = f(true);
(target_features, unstable_target_features)
}
pub(crate) fn print_version() {
let (major, minor, patch) = get_version();
println!("LLVM version: {major}.{minor}.{patch}");
}
pub(crate) fn get_version() -> (u32, u32, u32) {
// Can be called without initializing LLVM
unsafe {
(llvm::LLVMRustVersionMajor(), llvm::LLVMRustVersionMinor(), llvm::LLVMRustVersionPatch())
}
}
pub(crate) fn print_passes() {
// Can be called without initializing LLVM
unsafe {
llvm::LLVMRustPrintPasses();
}
}
fn llvm_target_features(tm: &llvm::TargetMachine) -> Vec<(&str, &str)> {
let len = unsafe { llvm::LLVMRustGetTargetFeaturesCount(tm) };
let mut ret = Vec::with_capacity(len);
for i in 0..len {
unsafe {
let mut feature = ptr::null();
let mut desc = ptr::null();
llvm::LLVMRustGetTargetFeature(tm, i, &mut feature, &mut desc);
if feature.is_null() || desc.is_null() {
bug!("LLVM returned a `null` target feature string");
}
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.raw(), out),
PrintKind::TargetFeatures => print_target_features(sess, tm.raw(), 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();
// 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(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 });
}
}
}
// FIXME(nagisa): figure out how to not allocate a full hashset here.
featsmap.insert(feature, enable);
}
}
// 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))
}