1 use crate::back::write::create_informational_target_machine;
2 use crate::{llvm, llvm_util};
4 use libloading::Library;
5 use rustc_codegen_ssa::target_features::{
6 supported_target_features, tied_target_features, RUSTC_SPECIFIC_FEATURES,
8 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
9 use rustc_data_structures::small_c_str::SmallCStr;
10 use rustc_fs_util::path_to_c_string;
11 use rustc_middle::bug;
12 use rustc_session::config::PrintRequest;
13 use rustc_session::Session;
14 use rustc_span::symbol::Symbol;
15 use rustc_target::spec::{MergeFunctions, PanicStrategy};
16 use smallvec::{smallvec, SmallVec};
17 use std::ffi::{CStr, CString};
27 static INIT: Once = Once::new();
29 pub(crate) fn init(sess: &Session) {
31 // Before we touch LLVM, make sure that multithreading is enabled.
32 if llvm::LLVMIsMultithreaded() != 1 {
33 bug!("LLVM compiled without support for threads");
42 if !INIT.is_completed() {
43 bug!("LLVM is not initialized");
47 unsafe fn configure_llvm(sess: &Session) {
48 let n_args = sess.opts.cg.llvm_args.len() + sess.target.llvm_args.len();
49 let mut llvm_c_strs = Vec::with_capacity(n_args + 1);
50 let mut llvm_args = Vec::with_capacity(n_args + 1);
52 llvm::LLVMRustInstallFatalErrorHandler();
53 // On Windows, an LLVM assertion will open an Abort/Retry/Ignore dialog
54 // box for the purpose of launching a debugger. However, on CI this will
55 // cause it to hang until it times out, which can take several hours.
56 if std::env::var_os("CI").is_some() {
57 llvm::LLVMRustDisableSystemDialogsOnCrash();
60 fn llvm_arg_to_arg_name(full_arg: &str) -> &str {
61 full_arg.trim().split(|c: char| c == '=' || c.is_whitespace()).next().unwrap_or("")
64 let cg_opts = sess.opts.cg.llvm_args.iter().map(AsRef::as_ref);
65 let tg_opts = sess.target.llvm_args.iter().map(AsRef::as_ref);
66 let sess_args = cg_opts.chain(tg_opts);
68 let user_specified_args: FxHashSet<_> =
69 sess_args.clone().map(|s| llvm_arg_to_arg_name(s)).filter(|s| !s.is_empty()).collect();
72 // This adds the given argument to LLVM. Unless `force` is true
73 // user specified arguments are *not* overridden.
74 let mut add = |arg: &str, force: bool| {
75 if force || !user_specified_args.contains(llvm_arg_to_arg_name(arg)) {
76 let s = CString::new(arg).unwrap();
77 llvm_args.push(s.as_ptr());
81 // Set the llvm "program name" to make usage and invalid argument messages more clear.
82 add("rustc -Cllvm-args=\"...\" with", true);
83 if sess.time_llvm_passes() {
84 add("-time-passes", false);
86 if sess.print_llvm_passes() {
87 add("-debug-pass=Structure", false);
89 if sess.target.generate_arange_section
90 && !sess.opts.unstable_opts.no_generate_arange_section
92 add("-generate-arange-section", false);
95 match sess.opts.unstable_opts.merge_functions.unwrap_or(sess.target.merge_functions) {
96 MergeFunctions::Disabled | MergeFunctions::Trampolines => {}
97 MergeFunctions::Aliases => {
98 add("-mergefunc-use-aliases", false);
102 if sess.target.os == "emscripten" && sess.panic_strategy() == PanicStrategy::Unwind {
103 add("-enable-emscripten-cxx-exceptions", false);
106 // HACK(eddyb) LLVM inserts `llvm.assume` calls to preserve align attributes
107 // during inlining. Unfortunately these may block other optimizations.
108 add("-preserve-alignment-assumptions-during-inlining=false", false);
110 // Use non-zero `import-instr-limit` multiplier for cold callsites.
111 add("-import-cold-multiplier=0.1", false);
113 for arg in sess_args {
118 if sess.opts.unstable_opts.llvm_time_trace {
119 llvm::LLVMTimeTraceProfilerInitialize();
122 llvm::LLVMInitializePasses();
124 // Use the legacy plugin registration if we don't use the new pass manager
125 if !should_use_new_llvm_pass_manager(
126 &sess.opts.unstable_opts.new_llvm_pass_manager,
129 // Register LLVM plugins by loading them into the compiler process.
130 for plugin in &sess.opts.unstable_opts.llvm_plugins {
131 let lib = Library::new(plugin).unwrap_or_else(|e| bug!("couldn't load plugin: {}", e));
132 debug!("LLVM plugin loaded successfully {:?} ({})", lib, plugin);
134 // Intentionally leak the dynamic library. We can't ever unload it
135 // since the library can make things that will live arbitrarily long.
140 rustc_llvm::initialize_available_targets();
142 llvm::LLVMRustSetLLVMOptions(llvm_args.len() as c_int, llvm_args.as_ptr());
145 pub fn time_trace_profiler_finish(file_name: &Path) {
147 let file_name = path_to_c_string(file_name);
148 llvm::LLVMTimeTraceProfilerFinish(file_name.as_ptr());
152 // WARNING: the features after applying `to_llvm_features` must be known
153 // to LLVM or the feature detection code will walk past the end of the feature
154 // array, leading to crashes.
156 // To find a list of LLVM's names, check llvm-project/llvm/include/llvm/Support/*TargetParser.def
157 // where the * matches the architecture's name
158 // Beware to not use the llvm github project for this, but check the git submodule
159 // found in src/llvm-project
160 // Though note that Rust can also be build with an external precompiled version of LLVM
161 // which might lead to failures if the oldest tested / supported LLVM version
162 // doesn't yet support the relevant intrinsics
163 pub fn to_llvm_features<'a>(sess: &Session, s: &'a str) -> SmallVec<[&'a str; 2]> {
164 let arch = if sess.target.arch == "x86_64" { "x86" } else { &*sess.target.arch };
166 ("x86", "sse4.2") => {
167 if get_version() >= (14, 0, 0) {
168 smallvec!["sse4.2", "crc32"]
173 ("x86", "pclmulqdq") => smallvec!["pclmul"],
174 ("x86", "rdrand") => smallvec!["rdrnd"],
175 ("x86", "bmi1") => smallvec!["bmi"],
176 ("x86", "cmpxchg16b") => smallvec!["cx16"],
177 ("x86", "avx512vaes") => smallvec!["vaes"],
178 ("x86", "avx512gfni") => smallvec!["gfni"],
179 ("x86", "avx512vpclmulqdq") => smallvec!["vpclmulqdq"],
180 ("aarch64", "rcpc2") => smallvec!["rcpc-immo"],
181 ("aarch64", "dpb") => smallvec!["ccpp"],
182 ("aarch64", "dpb2") => smallvec!["ccdp"],
183 ("aarch64", "frintts") => smallvec!["fptoint"],
184 ("aarch64", "fcma") => smallvec!["complxnum"],
185 ("aarch64", "pmuv3") => smallvec!["perfmon"],
186 ("aarch64", "paca") => smallvec!["pauth"],
187 ("aarch64", "pacg") => smallvec!["pauth"],
188 // Rust ties fp and neon together. In LLVM neon implicitly enables fp,
189 // but we manually enable neon when a feature only implicitly enables fp
190 ("aarch64", "f32mm") => smallvec!["f32mm", "neon"],
191 ("aarch64", "f64mm") => smallvec!["f64mm", "neon"],
192 ("aarch64", "fhm") => smallvec!["fp16fml", "neon"],
193 ("aarch64", "fp16") => smallvec!["fullfp16", "neon"],
194 ("aarch64", "jsconv") => smallvec!["jsconv", "neon"],
195 ("aarch64", "sve") => smallvec!["sve", "neon"],
196 ("aarch64", "sve2") => smallvec!["sve2", "neon"],
197 ("aarch64", "sve2-aes") => smallvec!["sve2-aes", "neon"],
198 ("aarch64", "sve2-sm4") => smallvec!["sve2-sm4", "neon"],
199 ("aarch64", "sve2-sha3") => smallvec!["sve2-sha3", "neon"],
200 ("aarch64", "sve2-bitperm") => smallvec!["sve2-bitperm", "neon"],
201 (_, s) => smallvec![s],
205 // Given a map from target_features to whether they are enabled or disabled,
206 // ensure only valid combinations are allowed.
207 pub fn check_tied_features(
209 features: &FxHashMap<&str, bool>,
210 ) -> Option<&'static [&'static str]> {
211 if !features.is_empty() {
212 for tied in tied_target_features(sess) {
213 // Tied features must be set to the same value, or not set at all
214 let mut tied_iter = tied.iter();
215 let enabled = features.get(tied_iter.next().unwrap());
216 if tied_iter.any(|f| enabled != features.get(f)) {
224 // Used to generate cfg variables and apply features
225 // Must express features in the way Rust understands them
226 pub fn target_features(sess: &Session, allow_unstable: bool) -> Vec<Symbol> {
227 let target_machine = create_informational_target_machine(sess);
228 let mut features: Vec<Symbol> = supported_target_features(sess)
230 .filter_map(|&(feature, gate)| {
231 if sess.is_nightly_build() || allow_unstable || gate.is_none() {
238 // check that all features in a given smallvec are enabled
239 for llvm_feature in to_llvm_features(sess, feature) {
240 let cstr = SmallCStr::new(llvm_feature);
241 if !unsafe { llvm::LLVMRustHasFeature(target_machine, cstr.as_ptr()) } {
247 .map(|feature| Symbol::intern(feature))
250 // LLVM 14 changed the ABI for i128 arguments to __float/__fix builtins on Win64
251 // (see https://reviews.llvm.org/D110413). This unstable target feature is intended for use
252 // by compiler-builtins, to export the builtins with the expected, LLVM-version-dependent ABI.
253 // The target feature can be dropped once we no longer support older LLVM versions.
254 if sess.is_nightly_build() && get_version() >= (14, 0, 0) {
255 features.push(Symbol::intern("llvm14-builtins-abi"));
260 pub fn print_version() {
261 let (major, minor, patch) = get_version();
262 println!("LLVM version: {}.{}.{}", major, minor, patch);
265 pub fn get_version() -> (u32, u32, u32) {
266 // Can be called without initializing LLVM
268 (llvm::LLVMRustVersionMajor(), llvm::LLVMRustVersionMinor(), llvm::LLVMRustVersionPatch())
272 pub fn print_passes() {
273 // Can be called without initializing LLVM
275 llvm::LLVMRustPrintPasses();
279 fn llvm_target_features(tm: &llvm::TargetMachine) -> Vec<(&str, &str)> {
280 let len = unsafe { llvm::LLVMRustGetTargetFeaturesCount(tm) };
281 let mut ret = Vec::with_capacity(len);
284 let mut feature = ptr::null();
285 let mut desc = ptr::null();
286 llvm::LLVMRustGetTargetFeature(tm, i, &mut feature, &mut desc);
287 if feature.is_null() || desc.is_null() {
288 bug!("LLVM returned a `null` target feature string");
290 let feature = CStr::from_ptr(feature).to_str().unwrap_or_else(|e| {
291 bug!("LLVM returned a non-utf8 feature string: {}", e);
293 let desc = CStr::from_ptr(desc).to_str().unwrap_or_else(|e| {
294 bug!("LLVM returned a non-utf8 feature string: {}", e);
296 ret.push((feature, desc));
302 fn print_target_features(sess: &Session, tm: &llvm::TargetMachine) {
303 let mut target_features = llvm_target_features(tm);
304 let mut rustc_target_features = supported_target_features(sess)
306 .filter_map(|(feature, _gate)| {
307 for llvm_feature in to_llvm_features(sess, *feature) {
308 // LLVM asserts that these are sorted. LLVM and Rust both use byte comparison for these strings.
309 match target_features.binary_search_by_key(&llvm_feature, |(f, _d)| f).ok().map(
311 let (_f, desc) = target_features.remove(index);
315 Some(v) => return Some(v),
321 .collect::<Vec<_>>();
322 rustc_target_features.extend_from_slice(&[(
324 "Enables C Run-time Libraries to be statically linked",
326 let max_feature_len = target_features
328 .chain(rustc_target_features.iter())
329 .map(|(feature, _desc)| feature.len())
333 println!("Features supported by rustc for this target:");
334 for (feature, desc) in &rustc_target_features {
335 println!(" {1:0$} - {2}.", max_feature_len, feature, desc);
337 println!("\nCode-generation features supported by LLVM for this target:");
338 for (feature, desc) in &target_features {
339 println!(" {1:0$} - {2}.", max_feature_len, feature, desc);
341 if target_features.is_empty() {
342 println!(" Target features listing is not supported by this LLVM version.");
344 println!("\nUse +feature to enable a feature, or -feature to disable it.");
345 println!("For example, rustc -C target-cpu=mycpu -C target-feature=+feature1,-feature2\n");
346 println!("Code-generation features cannot be used in cfg or #[target_feature],");
347 println!("and may be renamed or removed in a future version of LLVM or rustc.\n");
350 pub(crate) fn print(req: PrintRequest, sess: &Session) {
352 let tm = create_informational_target_machine(sess);
354 PrintRequest::TargetCPUs => unsafe { llvm::LLVMRustPrintTargetCPUs(tm) },
355 PrintRequest::TargetFeatures => print_target_features(sess, tm),
356 _ => bug!("rustc_codegen_llvm can't handle print request: {:?}", req),
360 fn handle_native(name: &str) -> &str {
361 if name != "native" {
367 let ptr = llvm::LLVMRustGetHostCPUName(&mut len);
368 str::from_utf8(slice::from_raw_parts(ptr as *const u8, len)).unwrap()
372 pub fn target_cpu(sess: &Session) -> &str {
373 match sess.opts.cg.target_cpu {
374 Some(ref name) => handle_native(name),
375 None => handle_native(sess.target.cpu.as_ref()),
379 /// The list of LLVM features computed from CLI flags (`-Ctarget-cpu`, `-Ctarget-feature`,
380 /// `--target` and similar).
381 pub(crate) fn global_llvm_features(sess: &Session, diagnostics: bool) -> Vec<String> {
382 // Features that come earlier are overridden by conflicting features later in the string.
383 // Typically we'll want more explicit settings to override the implicit ones, so:
385 // * Features from -Ctarget-cpu=*; are overridden by [^1]
386 // * Features implied by --target; are overridden by
387 // * Features from -Ctarget-feature; are overridden by
388 // * function specific features.
390 // [^1]: target-cpu=native is handled here, other target-cpu values are handled implicitly
391 // through LLVM TargetMachine implementation.
393 // FIXME(nagisa): it isn't clear what's the best interaction between features implied by
394 // `-Ctarget-cpu` and `--target` are. On one hand, you'd expect CLI arguments to always
395 // override anything that's implicit, so e.g. when there's no `--target` flag, features implied
396 // the host target are overridden by `-Ctarget-cpu=*`. On the other hand, what about when both
397 // `--target` and `-Ctarget-cpu=*` are specified? Both then imply some target features and both
398 // flags are specified by the user on the CLI. It isn't as clear-cut which order of precedence
399 // should be taken in cases like these.
400 let mut features = vec![];
402 // -Ctarget-cpu=native
403 match sess.opts.cg.target_cpu {
404 Some(ref s) if s == "native" => {
405 let features_string = unsafe {
406 let ptr = llvm::LLVMGetHostCPUFeatures();
407 let features_string = if !ptr.is_null() {
410 .unwrap_or_else(|e| {
411 bug!("LLVM returned a non-utf8 features string: {}", e);
415 bug!("could not allocate host CPU features, LLVM returned a `null` string");
418 llvm::LLVMDisposeMessage(ptr);
422 features.extend(features_string.split(',').map(String::from));
427 // Features implied by an implicit or explicit `--target`.
432 .filter(|v| !v.is_empty() && backend_feature_name(v).is_some())
433 // Drop +atomics-32 feature introduced in LLVM 15.
434 .filter(|v| *v != "+atomics-32" || get_version() >= (15, 0, 0))
439 let supported_features = supported_target_features(sess);
440 let mut featsmap = FxHashMap::default();
447 let enable_disable = match s.chars().next() {
449 Some(c @ '+' | c @ '-') => c,
452 let mut diag = sess.struct_warn(&format!(
453 "unknown feature specified for `-Ctarget-feature`: `{}`",
456 diag.note("features must begin with a `+` to enable or `-` to disable it");
463 let feature = backend_feature_name(s)?;
464 // Warn against use of LLVM specific feature names on the CLI.
465 if diagnostics && !supported_features.iter().any(|&(v, _)| v == feature) {
466 let rust_feature = supported_features.iter().find_map(|&(rust_feature, _)| {
467 let llvm_features = to_llvm_features(sess, rust_feature);
468 if llvm_features.contains(&feature) && !llvm_features.contains(&rust_feature) {
474 let mut diag = sess.struct_warn(&format!(
475 "unknown feature specified for `-Ctarget-feature`: `{}`",
478 diag.note("it is still passed through to the codegen backend");
479 if let Some(rust_feature) = rust_feature {
480 diag.help(&format!("you might have meant: `{}`", rust_feature));
482 diag.note("consider filing a feature request");
488 // FIXME(nagisa): figure out how to not allocate a full hashset here.
489 featsmap.insert(feature, enable_disable == '+');
492 // rustc-specific features do not get passed down to LLVM…
493 if RUSTC_SPECIFIC_FEATURES.contains(&feature) {
496 // ... otherwise though we run through `to_llvm_features` when
497 // passing requests down to LLVM. This means that all in-language
498 // features also work on the command line instead of having two
499 // different names when the LLVM name and the Rust name differ.
501 to_llvm_features(sess, feature)
503 .map(move |f| format!("{}{}", enable_disable, f)),
507 features.extend(feats);
509 if diagnostics && let Some(f) = check_tied_features(sess, &featsmap) {
511 "target features {} must all be enabled or disabled together",
519 /// Returns a feature name for the given `+feature` or `-feature` string.
521 /// Only allows features that are backend specific (i.e. not [`RUSTC_SPECIFIC_FEATURES`].)
522 fn backend_feature_name(s: &str) -> Option<&str> {
523 // features must start with a `+` or `-`.
524 let feature = s.strip_prefix(&['+', '-'][..]).unwrap_or_else(|| {
525 bug!("target feature `{}` must begin with a `+` or `-`", s);
527 // Rustc-specific feature requests like `+crt-static` or `-crt-static`
528 // are not passed down to LLVM.
529 if RUSTC_SPECIFIC_FEATURES.contains(&feature) {
535 pub fn tune_cpu(sess: &Session) -> Option<&str> {
536 let name = sess.opts.unstable_opts.tune_cpu.as_ref()?;
537 Some(handle_native(name))
540 pub(crate) fn should_use_new_llvm_pass_manager(user_opt: &Option<bool>, target_arch: &str) -> bool {
541 // The new pass manager is enabled by default for LLVM >= 13.
542 // This matches Clang, which also enables it since Clang 13.
544 // Since LLVM 15, the legacy pass manager is no longer supported.
545 if llvm_util::get_version() >= (15, 0, 0) {
549 // There are some perf issues with the new pass manager when targeting
550 // s390x with LLVM 13, so enable the new pass manager only with LLVM 14.
551 // See https://github.com/rust-lang/rust/issues/89609.
552 let min_version = if target_arch == "s390x" { 14 } else { 13 };
553 user_opt.unwrap_or_else(|| llvm_util::get_version() >= (min_version, 0, 0))