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};
26 static INIT: Once = Once::new();
28 pub(crate) fn init(sess: &Session) {
30 // Before we touch LLVM, make sure that multithreading is enabled.
31 if llvm::LLVMIsMultithreaded() != 1 {
32 bug!("LLVM compiled without support for threads");
41 if !INIT.is_completed() {
42 bug!("LLVM is not initialized");
46 unsafe fn configure_llvm(sess: &Session) {
47 let n_args = sess.opts.cg.llvm_args.len() + sess.target.llvm_args.len();
48 let mut llvm_c_strs = Vec::with_capacity(n_args + 1);
49 let mut llvm_args = Vec::with_capacity(n_args + 1);
51 llvm::LLVMRustInstallFatalErrorHandler();
52 // On Windows, an LLVM assertion will open an Abort/Retry/Ignore dialog
53 // box for the purpose of launching a debugger. However, on CI this will
54 // cause it to hang until it times out, which can take several hours.
55 if std::env::var_os("CI").is_some() {
56 llvm::LLVMRustDisableSystemDialogsOnCrash();
59 fn llvm_arg_to_arg_name(full_arg: &str) -> &str {
60 full_arg.trim().split(|c: char| c == '=' || c.is_whitespace()).next().unwrap_or("")
63 let cg_opts = sess.opts.cg.llvm_args.iter().map(AsRef::as_ref);
64 let tg_opts = sess.target.llvm_args.iter().map(AsRef::as_ref);
65 let sess_args = cg_opts.chain(tg_opts);
67 let user_specified_args: FxHashSet<_> =
68 sess_args.clone().map(|s| llvm_arg_to_arg_name(s)).filter(|s| !s.is_empty()).collect();
71 // This adds the given argument to LLVM. Unless `force` is true
72 // user specified arguments are *not* overridden.
73 let mut add = |arg: &str, force: bool| {
74 if force || !user_specified_args.contains(llvm_arg_to_arg_name(arg)) {
75 let s = CString::new(arg).unwrap();
76 llvm_args.push(s.as_ptr());
80 // Set the llvm "program name" to make usage and invalid argument messages more clear.
81 add("rustc -Cllvm-args=\"...\" with", true);
82 if sess.time_llvm_passes() {
83 add("-time-passes", false);
85 if sess.print_llvm_passes() {
86 add("-debug-pass=Structure", false);
88 if sess.target.generate_arange_section
89 && !sess.opts.unstable_opts.no_generate_arange_section
91 add("-generate-arange-section", false);
94 match sess.opts.unstable_opts.merge_functions.unwrap_or(sess.target.merge_functions) {
95 MergeFunctions::Disabled | MergeFunctions::Trampolines => {}
96 MergeFunctions::Aliases => {
97 add("-mergefunc-use-aliases", false);
101 if sess.target.os == "emscripten" && sess.panic_strategy() == PanicStrategy::Unwind {
102 add("-enable-emscripten-cxx-exceptions", false);
105 // HACK(eddyb) LLVM inserts `llvm.assume` calls to preserve align attributes
106 // during inlining. Unfortunately these may block other optimizations.
107 add("-preserve-alignment-assumptions-during-inlining=false", false);
109 // Use non-zero `import-instr-limit` multiplier for cold callsites.
110 add("-import-cold-multiplier=0.1", false);
112 for arg in sess_args {
117 if sess.opts.unstable_opts.llvm_time_trace {
118 llvm::LLVMTimeTraceProfilerInitialize();
121 llvm::LLVMInitializePasses();
123 // Use the legacy plugin registration if we don't use the new pass manager
124 if !should_use_new_llvm_pass_manager(
125 &sess.opts.unstable_opts.new_llvm_pass_manager,
128 // Register LLVM plugins by loading them into the compiler process.
129 for plugin in &sess.opts.unstable_opts.llvm_plugins {
130 let lib = Library::new(plugin).unwrap_or_else(|e| bug!("couldn't load plugin: {}", e));
131 debug!("LLVM plugin loaded successfully {:?} ({})", lib, plugin);
133 // Intentionally leak the dynamic library. We can't ever unload it
134 // since the library can make things that will live arbitrarily long.
139 rustc_llvm::initialize_available_targets();
141 llvm::LLVMRustSetLLVMOptions(llvm_args.len() as c_int, llvm_args.as_ptr());
144 pub fn time_trace_profiler_finish(file_name: &Path) {
146 let file_name = path_to_c_string(file_name);
147 llvm::LLVMTimeTraceProfilerFinish(file_name.as_ptr());
151 // WARNING: the features after applying `to_llvm_features` must be known
152 // to LLVM or the feature detection code will walk past the end of the feature
153 // array, leading to crashes.
155 // To find a list of LLVM's names, check llvm-project/llvm/include/llvm/Support/*TargetParser.def
156 // where the * matches the architecture's name
158 // For targets not present in the above location, see llvm-project/llvm/lib/Target/{ARCH}/*.td
159 // where `{ARCH}` is the architecture name. Look for instances of `SubtargetFeature`.
161 // Beware to not use the llvm github project for this, but check the git submodule
162 // found in src/llvm-project
163 // Though note that Rust can also be build with an external precompiled version of LLVM
164 // which might lead to failures if the oldest tested / supported LLVM version
165 // doesn't yet support the relevant intrinsics
166 pub fn to_llvm_features<'a>(sess: &Session, s: &'a str) -> SmallVec<[&'a str; 2]> {
167 let arch = if sess.target.arch == "x86_64" { "x86" } else { &*sess.target.arch };
169 ("x86", "sse4.2") => {
170 if get_version() >= (14, 0, 0) {
171 smallvec!["sse4.2", "crc32"]
176 ("x86", "pclmulqdq") => smallvec!["pclmul"],
177 ("x86", "rdrand") => smallvec!["rdrnd"],
178 ("x86", "bmi1") => smallvec!["bmi"],
179 ("x86", "cmpxchg16b") => smallvec!["cx16"],
180 ("x86", "avx512vaes") => smallvec!["vaes"],
181 ("x86", "avx512gfni") => smallvec!["gfni"],
182 ("x86", "avx512vpclmulqdq") => smallvec!["vpclmulqdq"],
183 ("aarch64", "rcpc2") => smallvec!["rcpc-immo"],
184 ("aarch64", "dpb") => smallvec!["ccpp"],
185 ("aarch64", "dpb2") => smallvec!["ccdp"],
186 ("aarch64", "frintts") => smallvec!["fptoint"],
187 ("aarch64", "fcma") => smallvec!["complxnum"],
188 ("aarch64", "pmuv3") => smallvec!["perfmon"],
189 ("aarch64", "paca") => smallvec!["pauth"],
190 ("aarch64", "pacg") => smallvec!["pauth"],
191 // Rust ties fp and neon together. In LLVM neon implicitly enables fp,
192 // but we manually enable neon when a feature only implicitly enables fp
193 ("aarch64", "f32mm") => smallvec!["f32mm", "neon"],
194 ("aarch64", "f64mm") => smallvec!["f64mm", "neon"],
195 ("aarch64", "fhm") => smallvec!["fp16fml", "neon"],
196 ("aarch64", "fp16") => smallvec!["fullfp16", "neon"],
197 ("aarch64", "jsconv") => smallvec!["jsconv", "neon"],
198 ("aarch64", "sve") => smallvec!["sve", "neon"],
199 ("aarch64", "sve2") => smallvec!["sve2", "neon"],
200 ("aarch64", "sve2-aes") => smallvec!["sve2-aes", "neon"],
201 ("aarch64", "sve2-sm4") => smallvec!["sve2-sm4", "neon"],
202 ("aarch64", "sve2-sha3") => smallvec!["sve2-sha3", "neon"],
203 ("aarch64", "sve2-bitperm") => smallvec!["sve2-bitperm", "neon"],
204 (_, s) => smallvec![s],
208 // Given a map from target_features to whether they are enabled or disabled,
209 // ensure only valid combinations are allowed.
210 pub fn check_tied_features(
212 features: &FxHashMap<&str, bool>,
213 ) -> Option<&'static [&'static str]> {
214 if !features.is_empty() {
215 for tied in tied_target_features(sess) {
216 // Tied features must be set to the same value, or not set at all
217 let mut tied_iter = tied.iter();
218 let enabled = features.get(tied_iter.next().unwrap());
219 if tied_iter.any(|f| enabled != features.get(f)) {
227 // Used to generate cfg variables and apply features
228 // Must express features in the way Rust understands them
229 pub fn target_features(sess: &Session, allow_unstable: bool) -> Vec<Symbol> {
230 let target_machine = create_informational_target_machine(sess);
231 let mut features: Vec<Symbol> = supported_target_features(sess)
233 .filter_map(|&(feature, gate)| {
234 if sess.is_nightly_build() || allow_unstable || gate.is_none() {
241 // check that all features in a given smallvec are enabled
242 for llvm_feature in to_llvm_features(sess, feature) {
243 let cstr = SmallCStr::new(llvm_feature);
244 if !unsafe { llvm::LLVMRustHasFeature(target_machine, cstr.as_ptr()) } {
250 .map(|feature| Symbol::intern(feature))
253 // LLVM 14 changed the ABI for i128 arguments to __float/__fix builtins on Win64
254 // (see https://reviews.llvm.org/D110413). This unstable target feature is intended for use
255 // by compiler-builtins, to export the builtins with the expected, LLVM-version-dependent ABI.
256 // The target feature can be dropped once we no longer support older LLVM versions.
257 if sess.is_nightly_build() && get_version() >= (14, 0, 0) {
258 features.push(Symbol::intern("llvm14-builtins-abi"));
263 pub fn print_version() {
264 let (major, minor, patch) = get_version();
265 println!("LLVM version: {}.{}.{}", major, minor, patch);
268 pub fn get_version() -> (u32, u32, u32) {
269 // Can be called without initializing LLVM
271 (llvm::LLVMRustVersionMajor(), llvm::LLVMRustVersionMinor(), llvm::LLVMRustVersionPatch())
275 pub fn print_passes() {
276 // Can be called without initializing LLVM
278 llvm::LLVMRustPrintPasses();
282 fn llvm_target_features(tm: &llvm::TargetMachine) -> Vec<(&str, &str)> {
283 let len = unsafe { llvm::LLVMRustGetTargetFeaturesCount(tm) };
284 let mut ret = Vec::with_capacity(len);
287 let mut feature = ptr::null();
288 let mut desc = ptr::null();
289 llvm::LLVMRustGetTargetFeature(tm, i, &mut feature, &mut desc);
290 if feature.is_null() || desc.is_null() {
291 bug!("LLVM returned a `null` target feature string");
293 let feature = CStr::from_ptr(feature).to_str().unwrap_or_else(|e| {
294 bug!("LLVM returned a non-utf8 feature string: {}", e);
296 let desc = CStr::from_ptr(desc).to_str().unwrap_or_else(|e| {
297 bug!("LLVM returned a non-utf8 feature string: {}", e);
299 ret.push((feature, desc));
305 fn print_target_features(sess: &Session, tm: &llvm::TargetMachine) {
306 let mut target_features = llvm_target_features(tm);
307 let mut rustc_target_features = supported_target_features(sess)
309 .filter_map(|(feature, _gate)| {
310 for llvm_feature in to_llvm_features(sess, *feature) {
311 // LLVM asserts that these are sorted. LLVM and Rust both use byte comparison for these strings.
312 match target_features.binary_search_by_key(&llvm_feature, |(f, _d)| f).ok().map(
314 let (_f, desc) = target_features.remove(index);
318 Some(v) => return Some(v),
324 .collect::<Vec<_>>();
325 rustc_target_features.extend_from_slice(&[(
327 "Enables C Run-time Libraries to be statically linked",
329 let max_feature_len = target_features
331 .chain(rustc_target_features.iter())
332 .map(|(feature, _desc)| feature.len())
336 println!("Features supported by rustc for this target:");
337 for (feature, desc) in &rustc_target_features {
338 println!(" {1:0$} - {2}.", max_feature_len, feature, desc);
340 println!("\nCode-generation features supported by LLVM for this target:");
341 for (feature, desc) in &target_features {
342 println!(" {1:0$} - {2}.", max_feature_len, feature, desc);
344 if target_features.is_empty() {
345 println!(" Target features listing is not supported by this LLVM version.");
347 println!("\nUse +feature to enable a feature, or -feature to disable it.");
348 println!("For example, rustc -C target-cpu=mycpu -C target-feature=+feature1,-feature2\n");
349 println!("Code-generation features cannot be used in cfg or #[target_feature],");
350 println!("and may be renamed or removed in a future version of LLVM or rustc.\n");
353 pub(crate) fn print(req: PrintRequest, sess: &Session) {
355 let tm = create_informational_target_machine(sess);
357 PrintRequest::TargetCPUs => unsafe { llvm::LLVMRustPrintTargetCPUs(tm) },
358 PrintRequest::TargetFeatures => print_target_features(sess, tm),
359 _ => bug!("rustc_codegen_llvm can't handle print request: {:?}", req),
363 fn handle_native(name: &str) -> &str {
364 if name != "native" {
370 let ptr = llvm::LLVMRustGetHostCPUName(&mut len);
371 str::from_utf8(slice::from_raw_parts(ptr as *const u8, len)).unwrap()
375 pub fn target_cpu(sess: &Session) -> &str {
376 match sess.opts.cg.target_cpu {
377 Some(ref name) => handle_native(name),
378 None => handle_native(sess.target.cpu.as_ref()),
382 /// The list of LLVM features computed from CLI flags (`-Ctarget-cpu`, `-Ctarget-feature`,
383 /// `--target` and similar).
384 pub(crate) fn global_llvm_features(sess: &Session, diagnostics: bool) -> Vec<String> {
385 // Features that come earlier are overridden by conflicting features later in the string.
386 // Typically we'll want more explicit settings to override the implicit ones, so:
388 // * Features from -Ctarget-cpu=*; are overridden by [^1]
389 // * Features implied by --target; are overridden by
390 // * Features from -Ctarget-feature; are overridden by
391 // * function specific features.
393 // [^1]: target-cpu=native is handled here, other target-cpu values are handled implicitly
394 // through LLVM TargetMachine implementation.
396 // FIXME(nagisa): it isn't clear what's the best interaction between features implied by
397 // `-Ctarget-cpu` and `--target` are. On one hand, you'd expect CLI arguments to always
398 // override anything that's implicit, so e.g. when there's no `--target` flag, features implied
399 // the host target are overridden by `-Ctarget-cpu=*`. On the other hand, what about when both
400 // `--target` and `-Ctarget-cpu=*` are specified? Both then imply some target features and both
401 // flags are specified by the user on the CLI. It isn't as clear-cut which order of precedence
402 // should be taken in cases like these.
403 let mut features = vec![];
405 // -Ctarget-cpu=native
406 match sess.opts.cg.target_cpu {
407 Some(ref s) if s == "native" => {
408 let features_string = unsafe {
409 let ptr = llvm::LLVMGetHostCPUFeatures();
410 let features_string = if !ptr.is_null() {
413 .unwrap_or_else(|e| {
414 bug!("LLVM returned a non-utf8 features string: {}", e);
418 bug!("could not allocate host CPU features, LLVM returned a `null` string");
421 llvm::LLVMDisposeMessage(ptr);
425 features.extend(features_string.split(',').map(String::from));
430 // Features implied by an implicit or explicit `--target`.
435 .filter(|v| !v.is_empty() && backend_feature_name(v).is_some())
436 // Drop +atomics-32 feature introduced in LLVM 15.
437 .filter(|v| *v != "+atomics-32" || get_version() >= (15, 0, 0))
442 let supported_features = supported_target_features(sess);
443 let mut featsmap = FxHashMap::default();
450 let enable_disable = match s.chars().next() {
452 Some(c @ '+' | c @ '-') => c,
455 let mut diag = sess.struct_warn(&format!(
456 "unknown feature specified for `-Ctarget-feature`: `{}`",
459 diag.note("features must begin with a `+` to enable or `-` to disable it");
466 let feature = backend_feature_name(s)?;
467 // Warn against use of LLVM specific feature names on the CLI.
468 if diagnostics && !supported_features.iter().any(|&(v, _)| v == feature) {
469 let rust_feature = supported_features.iter().find_map(|&(rust_feature, _)| {
470 let llvm_features = to_llvm_features(sess, rust_feature);
471 if llvm_features.contains(&feature) && !llvm_features.contains(&rust_feature) {
477 let mut diag = sess.struct_warn(&format!(
478 "unknown feature specified for `-Ctarget-feature`: `{}`",
481 diag.note("it is still passed through to the codegen backend");
482 if let Some(rust_feature) = rust_feature {
483 diag.help(&format!("you might have meant: `{}`", rust_feature));
485 diag.note("consider filing a feature request");
491 // FIXME(nagisa): figure out how to not allocate a full hashset here.
492 featsmap.insert(feature, enable_disable == '+');
495 // rustc-specific features do not get passed down to LLVM…
496 if RUSTC_SPECIFIC_FEATURES.contains(&feature) {
499 // ... otherwise though we run through `to_llvm_features` when
500 // passing requests down to LLVM. This means that all in-language
501 // features also work on the command line instead of having two
502 // different names when the LLVM name and the Rust name differ.
504 to_llvm_features(sess, feature)
506 .map(move |f| format!("{}{}", enable_disable, f)),
510 features.extend(feats);
512 if diagnostics && let Some(f) = check_tied_features(sess, &featsmap) {
514 "target features {} must all be enabled or disabled together",
522 /// Returns a feature name for the given `+feature` or `-feature` string.
524 /// Only allows features that are backend specific (i.e. not [`RUSTC_SPECIFIC_FEATURES`].)
525 fn backend_feature_name(s: &str) -> Option<&str> {
526 // features must start with a `+` or `-`.
527 let feature = s.strip_prefix(&['+', '-'][..]).unwrap_or_else(|| {
528 bug!("target feature `{}` must begin with a `+` or `-`", s);
530 // Rustc-specific feature requests like `+crt-static` or `-crt-static`
531 // are not passed down to LLVM.
532 if RUSTC_SPECIFIC_FEATURES.contains(&feature) {
538 pub fn tune_cpu(sess: &Session) -> Option<&str> {
539 let name = sess.opts.unstable_opts.tune_cpu.as_ref()?;
540 Some(handle_native(name))
543 pub(crate) fn should_use_new_llvm_pass_manager(user_opt: &Option<bool>, target_arch: &str) -> bool {
544 // The new pass manager is enabled by default for LLVM >= 13.
545 // This matches Clang, which also enables it since Clang 13.
547 // Since LLVM 15, the legacy pass manager is no longer supported.
548 if llvm_util::get_version() >= (15, 0, 0) {
552 // There are some perf issues with the new pass manager when targeting
553 // s390x with LLVM 13, so enable the new pass manager only with LLVM 14.
554 // See https://github.com/rust-lang/rust/issues/89609.
555 let min_version = if target_arch == "s390x" { 14 } else { 13 };
556 user_opt.unwrap_or_else(|| llvm_util::get_version() >= (min_version, 0, 0))