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 // Disable the machine outliner by default in LLVM versions 11 and LLVM
96 // version 12, where it leads to miscompilation.
99 // - https://github.com/rust-lang/rust/issues/85351
100 // - https://reviews.llvm.org/D103167
101 if llvm_util::get_version() < (13, 0, 0) {
102 add("-enable-machine-outliner=never", false);
105 match sess.opts.unstable_opts.merge_functions.unwrap_or(sess.target.merge_functions) {
106 MergeFunctions::Disabled | MergeFunctions::Trampolines => {}
107 MergeFunctions::Aliases => {
108 add("-mergefunc-use-aliases", false);
112 if sess.target.os == "emscripten" && sess.panic_strategy() == PanicStrategy::Unwind {
113 add("-enable-emscripten-cxx-exceptions", false);
116 // HACK(eddyb) LLVM inserts `llvm.assume` calls to preserve align attributes
117 // during inlining. Unfortunately these may block other optimizations.
118 add("-preserve-alignment-assumptions-during-inlining=false", false);
120 // Use non-zero `import-instr-limit` multiplier for cold callsites.
121 add("-import-cold-multiplier=0.1", false);
123 for arg in sess_args {
128 if sess.opts.unstable_opts.llvm_time_trace {
129 llvm::LLVMTimeTraceProfilerInitialize();
132 llvm::LLVMInitializePasses();
134 // Use the legacy plugin registration if we don't use the new pass manager
135 if !should_use_new_llvm_pass_manager(
136 &sess.opts.unstable_opts.new_llvm_pass_manager,
139 // Register LLVM plugins by loading them into the compiler process.
140 for plugin in &sess.opts.unstable_opts.llvm_plugins {
141 let lib = Library::new(plugin).unwrap_or_else(|e| bug!("couldn't load plugin: {}", e));
142 debug!("LLVM plugin loaded successfully {:?} ({})", lib, plugin);
144 // Intentionally leak the dynamic library. We can't ever unload it
145 // since the library can make things that will live arbitrarily long.
150 rustc_llvm::initialize_available_targets();
152 llvm::LLVMRustSetLLVMOptions(llvm_args.len() as c_int, llvm_args.as_ptr());
155 pub fn time_trace_profiler_finish(file_name: &Path) {
157 let file_name = path_to_c_string(file_name);
158 llvm::LLVMTimeTraceProfilerFinish(file_name.as_ptr());
162 // WARNING: the features after applying `to_llvm_features` must be known
163 // to LLVM or the feature detection code will walk past the end of the feature
164 // array, leading to crashes.
166 // To find a list of LLVM's names, check llvm-project/llvm/include/llvm/Support/*TargetParser.def
167 // where the * matches the architecture's name
168 // Beware to not use the llvm github project for this, but check the git submodule
169 // found in src/llvm-project
170 // Though note that Rust can also be build with an external precompiled version of LLVM
171 // which might lead to failures if the oldest tested / supported LLVM version
172 // doesn't yet support the relevant intrinsics
173 pub fn to_llvm_features<'a>(sess: &Session, s: &'a str) -> SmallVec<[&'a str; 2]> {
174 let arch = if sess.target.arch == "x86_64" { "x86" } else { &*sess.target.arch };
176 ("x86", "sse4.2") => {
177 if get_version() >= (14, 0, 0) {
178 smallvec!["sse4.2", "crc32"]
183 ("x86", "pclmulqdq") => smallvec!["pclmul"],
184 ("x86", "rdrand") => smallvec!["rdrnd"],
185 ("x86", "bmi1") => smallvec!["bmi"],
186 ("x86", "cmpxchg16b") => smallvec!["cx16"],
187 ("x86", "avx512vaes") => smallvec!["vaes"],
188 ("x86", "avx512gfni") => smallvec!["gfni"],
189 ("x86", "avx512vpclmulqdq") => smallvec!["vpclmulqdq"],
190 ("aarch64", "rcpc2") => smallvec!["rcpc-immo"],
191 ("aarch64", "dpb") => smallvec!["ccpp"],
192 ("aarch64", "dpb2") => smallvec!["ccdp"],
193 ("aarch64", "frintts") => smallvec!["fptoint"],
194 ("aarch64", "fcma") => smallvec!["complxnum"],
195 ("aarch64", "pmuv3") => smallvec!["perfmon"],
196 ("aarch64", "paca") => smallvec!["pauth"],
197 ("aarch64", "pacg") => smallvec!["pauth"],
198 // Rust ties fp and neon together. In LLVM neon implicitly enables fp,
199 // but we manually enable neon when a feature only implicitly enables fp
200 ("aarch64", "f32mm") => smallvec!["f32mm", "neon"],
201 ("aarch64", "f64mm") => smallvec!["f64mm", "neon"],
202 ("aarch64", "fhm") => smallvec!["fp16fml", "neon"],
203 ("aarch64", "fp16") => smallvec!["fullfp16", "neon"],
204 ("aarch64", "jsconv") => smallvec!["jsconv", "neon"],
205 ("aarch64", "sve") => smallvec!["sve", "neon"],
206 ("aarch64", "sve2") => smallvec!["sve2", "neon"],
207 ("aarch64", "sve2-aes") => smallvec!["sve2-aes", "neon"],
208 ("aarch64", "sve2-sm4") => smallvec!["sve2-sm4", "neon"],
209 ("aarch64", "sve2-sha3") => smallvec!["sve2-sha3", "neon"],
210 ("aarch64", "sve2-bitperm") => smallvec!["sve2-bitperm", "neon"],
211 (_, s) => smallvec![s],
215 // Given a map from target_features to whether they are enabled or disabled,
216 // ensure only valid combinations are allowed.
217 pub fn check_tied_features(
219 features: &FxHashMap<&str, bool>,
220 ) -> Option<&'static [&'static str]> {
221 if !features.is_empty() {
222 for tied in tied_target_features(sess) {
223 // Tied features must be set to the same value, or not set at all
224 let mut tied_iter = tied.iter();
225 let enabled = features.get(tied_iter.next().unwrap());
226 if tied_iter.any(|f| enabled != features.get(f)) {
234 // Used to generate cfg variables and apply features
235 // Must express features in the way Rust understands them
236 pub fn target_features(sess: &Session, allow_unstable: bool) -> Vec<Symbol> {
237 let target_machine = create_informational_target_machine(sess);
238 let mut features: Vec<Symbol> = supported_target_features(sess)
240 .filter_map(|&(feature, gate)| {
241 if sess.is_nightly_build() || allow_unstable || gate.is_none() {
248 // check that all features in a given smallvec are enabled
249 for llvm_feature in to_llvm_features(sess, feature) {
250 let cstr = SmallCStr::new(llvm_feature);
251 if !unsafe { llvm::LLVMRustHasFeature(target_machine, cstr.as_ptr()) } {
257 .map(|feature| Symbol::intern(feature))
260 // LLVM 14 changed the ABI for i128 arguments to __float/__fix builtins on Win64
261 // (see https://reviews.llvm.org/D110413). This unstable target feature is intended for use
262 // by compiler-builtins, to export the builtins with the expected, LLVM-version-dependent ABI.
263 // The target feature can be dropped once we no longer support older LLVM versions.
264 if sess.is_nightly_build() && get_version() >= (14, 0, 0) {
265 features.push(Symbol::intern("llvm14-builtins-abi"));
270 pub fn print_version() {
271 let (major, minor, patch) = get_version();
272 println!("LLVM version: {}.{}.{}", major, minor, patch);
275 pub fn get_version() -> (u32, u32, u32) {
276 // Can be called without initializing LLVM
278 (llvm::LLVMRustVersionMajor(), llvm::LLVMRustVersionMinor(), llvm::LLVMRustVersionPatch())
282 pub fn print_passes() {
283 // Can be called without initializing LLVM
285 llvm::LLVMRustPrintPasses();
289 fn llvm_target_features(tm: &llvm::TargetMachine) -> Vec<(&str, &str)> {
290 let len = unsafe { llvm::LLVMRustGetTargetFeaturesCount(tm) };
291 let mut ret = Vec::with_capacity(len);
294 let mut feature = ptr::null();
295 let mut desc = ptr::null();
296 llvm::LLVMRustGetTargetFeature(tm, i, &mut feature, &mut desc);
297 if feature.is_null() || desc.is_null() {
298 bug!("LLVM returned a `null` target feature string");
300 let feature = CStr::from_ptr(feature).to_str().unwrap_or_else(|e| {
301 bug!("LLVM returned a non-utf8 feature string: {}", e);
303 let desc = CStr::from_ptr(desc).to_str().unwrap_or_else(|e| {
304 bug!("LLVM returned a non-utf8 feature string: {}", e);
306 ret.push((feature, desc));
312 fn print_target_features(sess: &Session, tm: &llvm::TargetMachine) {
313 let mut target_features = llvm_target_features(tm);
314 let mut rustc_target_features = supported_target_features(sess)
316 .filter_map(|(feature, _gate)| {
317 for llvm_feature in to_llvm_features(sess, *feature) {
318 // LLVM asserts that these are sorted. LLVM and Rust both use byte comparison for these strings.
319 match target_features.binary_search_by_key(&llvm_feature, |(f, _d)| f).ok().map(
321 let (_f, desc) = target_features.remove(index);
325 Some(v) => return Some(v),
331 .collect::<Vec<_>>();
332 rustc_target_features.extend_from_slice(&[(
334 "Enables C Run-time Libraries to be statically linked",
336 let max_feature_len = target_features
338 .chain(rustc_target_features.iter())
339 .map(|(feature, _desc)| feature.len())
343 println!("Features supported by rustc for this target:");
344 for (feature, desc) in &rustc_target_features {
345 println!(" {1:0$} - {2}.", max_feature_len, feature, desc);
347 println!("\nCode-generation features supported by LLVM for this target:");
348 for (feature, desc) in &target_features {
349 println!(" {1:0$} - {2}.", max_feature_len, feature, desc);
351 if target_features.is_empty() {
352 println!(" Target features listing is not supported by this LLVM version.");
354 println!("\nUse +feature to enable a feature, or -feature to disable it.");
355 println!("For example, rustc -C target-cpu=mycpu -C target-feature=+feature1,-feature2\n");
356 println!("Code-generation features cannot be used in cfg or #[target_feature],");
357 println!("and may be renamed or removed in a future version of LLVM or rustc.\n");
360 pub(crate) fn print(req: PrintRequest, sess: &Session) {
362 let tm = create_informational_target_machine(sess);
364 PrintRequest::TargetCPUs => unsafe { llvm::LLVMRustPrintTargetCPUs(tm) },
365 PrintRequest::TargetFeatures => print_target_features(sess, tm),
366 _ => bug!("rustc_codegen_llvm can't handle print request: {:?}", req),
370 fn handle_native(name: &str) -> &str {
371 if name != "native" {
377 let ptr = llvm::LLVMRustGetHostCPUName(&mut len);
378 str::from_utf8(slice::from_raw_parts(ptr as *const u8, len)).unwrap()
382 pub fn target_cpu(sess: &Session) -> &str {
383 match sess.opts.cg.target_cpu {
384 Some(ref name) => handle_native(name),
385 None => handle_native(sess.target.cpu.as_ref()),
389 /// The list of LLVM features computed from CLI flags (`-Ctarget-cpu`, `-Ctarget-feature`,
390 /// `--target` and similar).
391 pub(crate) fn global_llvm_features(sess: &Session, diagnostics: bool) -> Vec<String> {
392 // Features that come earlier are overridden by conflicting features later in the string.
393 // Typically we'll want more explicit settings to override the implicit ones, so:
395 // * Features from -Ctarget-cpu=*; are overridden by [^1]
396 // * Features implied by --target; are overridden by
397 // * Features from -Ctarget-feature; are overridden by
398 // * function specific features.
400 // [^1]: target-cpu=native is handled here, other target-cpu values are handled implicitly
401 // through LLVM TargetMachine implementation.
403 // FIXME(nagisa): it isn't clear what's the best interaction between features implied by
404 // `-Ctarget-cpu` and `--target` are. On one hand, you'd expect CLI arguments to always
405 // override anything that's implicit, so e.g. when there's no `--target` flag, features implied
406 // the host target are overridden by `-Ctarget-cpu=*`. On the other hand, what about when both
407 // `--target` and `-Ctarget-cpu=*` are specified? Both then imply some target features and both
408 // flags are specified by the user on the CLI. It isn't as clear-cut which order of precedence
409 // should be taken in cases like these.
410 let mut features = vec![];
412 // -Ctarget-cpu=native
413 match sess.opts.cg.target_cpu {
414 Some(ref s) if s == "native" => {
415 let features_string = unsafe {
416 let ptr = llvm::LLVMGetHostCPUFeatures();
417 let features_string = if !ptr.is_null() {
420 .unwrap_or_else(|e| {
421 bug!("LLVM returned a non-utf8 features string: {}", e);
425 bug!("could not allocate host CPU features, LLVM returned a `null` string");
428 llvm::LLVMDisposeMessage(ptr);
432 features.extend(features_string.split(',').map(String::from));
437 // Features implied by an implicit or explicit `--target`.
442 .filter(|v| !v.is_empty() && backend_feature_name(v).is_some())
443 // Drop +atomics-32 feature introduced in LLVM 15.
444 .filter(|v| *v != "+atomics-32" || get_version() >= (15, 0, 0))
449 let supported_features = supported_target_features(sess);
450 let mut featsmap = FxHashMap::default();
457 let enable_disable = match s.chars().next() {
459 Some(c @ '+' | c @ '-') => c,
462 let mut diag = sess.struct_warn(&format!(
463 "unknown feature specified for `-Ctarget-feature`: `{}`",
466 diag.note("features must begin with a `+` to enable or `-` to disable it");
473 let feature = backend_feature_name(s)?;
474 // Warn against use of LLVM specific feature names on the CLI.
475 if diagnostics && !supported_features.iter().any(|&(v, _)| v == feature) {
476 let rust_feature = supported_features.iter().find_map(|&(rust_feature, _)| {
477 let llvm_features = to_llvm_features(sess, rust_feature);
478 if llvm_features.contains(&feature) && !llvm_features.contains(&rust_feature) {
484 let mut diag = sess.struct_warn(&format!(
485 "unknown feature specified for `-Ctarget-feature`: `{}`",
488 diag.note("it is still passed through to the codegen backend");
489 if let Some(rust_feature) = rust_feature {
490 diag.help(&format!("you might have meant: `{}`", rust_feature));
492 diag.note("consider filing a feature request");
498 // FIXME(nagisa): figure out how to not allocate a full hashset here.
499 featsmap.insert(feature, enable_disable == '+');
502 // rustc-specific features do not get passed down to LLVM…
503 if RUSTC_SPECIFIC_FEATURES.contains(&feature) {
506 // ... otherwise though we run through `to_llvm_features` when
507 // passing requests down to LLVM. This means that all in-language
508 // features also work on the command line instead of having two
509 // different names when the LLVM name and the Rust name differ.
511 to_llvm_features(sess, feature)
513 .map(move |f| format!("{}{}", enable_disable, f)),
517 features.extend(feats);
519 if diagnostics && let Some(f) = check_tied_features(sess, &featsmap) {
521 "target features {} must all be enabled or disabled together",
529 /// Returns a feature name for the given `+feature` or `-feature` string.
531 /// Only allows features that are backend specific (i.e. not [`RUSTC_SPECIFIC_FEATURES`].)
532 fn backend_feature_name(s: &str) -> Option<&str> {
533 // features must start with a `+` or `-`.
534 let feature = s.strip_prefix(&['+', '-'][..]).unwrap_or_else(|| {
535 bug!("target feature `{}` must begin with a `+` or `-`", s);
537 // Rustc-specific feature requests like `+crt-static` or `-crt-static`
538 // are not passed down to LLVM.
539 if RUSTC_SPECIFIC_FEATURES.contains(&feature) {
545 pub fn tune_cpu(sess: &Session) -> Option<&str> {
546 let name = sess.opts.unstable_opts.tune_cpu.as_ref()?;
547 Some(handle_native(name))
550 pub(crate) fn should_use_new_llvm_pass_manager(user_opt: &Option<bool>, target_arch: &str) -> bool {
551 // The new pass manager is enabled by default for LLVM >= 13.
552 // This matches Clang, which also enables it since Clang 13.
554 // Since LLVM 15, the legacy pass manager is no longer supported.
555 if llvm_util::get_version() >= (15, 0, 0) {
559 // There are some perf issues with the new pass manager when targeting
560 // s390x with LLVM 13, so enable the new pass manager only with LLVM 14.
561 // See https://github.com/rust-lang/rust/issues/89609.
562 let min_version = if target_arch == "s390x" { 14 } else { 13 };
563 user_opt.unwrap_or_else(|| llvm_util::get_version() >= (min_version, 0, 0))