1 use crate::back::write::create_informational_target_machine;
3 PossibleFeature, TargetFeatureDisableOrEnable, UnknownCTargetFeature,
4 UnknownCTargetFeaturePrefix,
8 use rustc_codegen_ssa::target_features::{
9 supported_target_features, tied_target_features, RUSTC_SPECIFIC_FEATURES,
11 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
12 use rustc_data_structures::small_c_str::SmallCStr;
13 use rustc_fs_util::path_to_c_string;
14 use rustc_middle::bug;
15 use rustc_session::config::PrintRequest;
16 use rustc_session::Session;
17 use rustc_span::symbol::Symbol;
18 use rustc_target::spec::{MergeFunctions, PanicStrategy};
19 use smallvec::{smallvec, SmallVec};
20 use std::ffi::{CStr, CString};
28 static INIT: Once = Once::new();
30 pub(crate) fn init(sess: &Session) {
32 // Before we touch LLVM, make sure that multithreading is enabled.
33 if llvm::LLVMIsMultithreaded() != 1 {
34 bug!("LLVM compiled without support for threads");
43 if !INIT.is_completed() {
44 bug!("LLVM is not initialized");
48 unsafe fn configure_llvm(sess: &Session) {
49 let n_args = sess.opts.cg.llvm_args.len() + sess.target.llvm_args.len();
50 let mut llvm_c_strs = Vec::with_capacity(n_args + 1);
51 let mut llvm_args = Vec::with_capacity(n_args + 1);
53 llvm::LLVMRustInstallFatalErrorHandler();
54 // On Windows, an LLVM assertion will open an Abort/Retry/Ignore dialog
55 // box for the purpose of launching a debugger. However, on CI this will
56 // cause it to hang until it times out, which can take several hours.
57 if std::env::var_os("CI").is_some() {
58 llvm::LLVMRustDisableSystemDialogsOnCrash();
61 fn llvm_arg_to_arg_name(full_arg: &str) -> &str {
62 full_arg.trim().split(|c: char| c == '=' || c.is_whitespace()).next().unwrap_or("")
65 let cg_opts = sess.opts.cg.llvm_args.iter().map(AsRef::as_ref);
66 let tg_opts = sess.target.llvm_args.iter().map(AsRef::as_ref);
67 let sess_args = cg_opts.chain(tg_opts);
69 let user_specified_args: FxHashSet<_> =
70 sess_args.clone().map(|s| llvm_arg_to_arg_name(s)).filter(|s| !s.is_empty()).collect();
73 // This adds the given argument to LLVM. Unless `force` is true
74 // user specified arguments are *not* overridden.
75 let mut add = |arg: &str, force: bool| {
76 if force || !user_specified_args.contains(llvm_arg_to_arg_name(arg)) {
77 let s = CString::new(arg).unwrap();
78 llvm_args.push(s.as_ptr());
82 // Set the llvm "program name" to make usage and invalid argument messages more clear.
83 add("rustc -Cllvm-args=\"...\" with", true);
84 if sess.time_llvm_passes() {
85 add("-time-passes", false);
87 if sess.print_llvm_passes() {
88 add("-debug-pass=Structure", false);
90 if sess.target.generate_arange_section
91 && !sess.opts.unstable_opts.no_generate_arange_section
93 add("-generate-arange-section", false);
96 match sess.opts.unstable_opts.merge_functions.unwrap_or(sess.target.merge_functions) {
97 MergeFunctions::Disabled | MergeFunctions::Trampolines => {}
98 MergeFunctions::Aliases => {
99 add("-mergefunc-use-aliases", false);
103 if sess.target.os == "emscripten" && sess.panic_strategy() == PanicStrategy::Unwind {
104 add("-enable-emscripten-cxx-exceptions", false);
107 // HACK(eddyb) LLVM inserts `llvm.assume` calls to preserve align attributes
108 // during inlining. Unfortunately these may block other optimizations.
109 add("-preserve-alignment-assumptions-during-inlining=false", false);
111 // Use non-zero `import-instr-limit` multiplier for cold callsites.
112 add("-import-cold-multiplier=0.1", false);
114 for arg in sess_args {
119 if sess.opts.unstable_opts.llvm_time_trace {
120 llvm::LLVMTimeTraceProfilerInitialize();
123 llvm::LLVMInitializePasses();
125 rustc_llvm::initialize_available_targets();
127 llvm::LLVMRustSetLLVMOptions(llvm_args.len() as c_int, llvm_args.as_ptr());
130 pub fn time_trace_profiler_finish(file_name: &Path) {
132 let file_name = path_to_c_string(file_name);
133 llvm::LLVMTimeTraceProfilerFinish(file_name.as_ptr());
137 // WARNING: the features after applying `to_llvm_features` must be known
138 // to LLVM or the feature detection code will walk past the end of the feature
139 // array, leading to crashes.
141 // To find a list of LLVM's names, check llvm-project/llvm/include/llvm/Support/*TargetParser.def
142 // where the * matches the architecture's name
144 // For targets not present in the above location, see llvm-project/llvm/lib/Target/{ARCH}/*.td
145 // where `{ARCH}` is the architecture name. Look for instances of `SubtargetFeature`.
147 // Beware to not use the llvm github project for this, but check the git submodule
148 // found in src/llvm-project
149 // Though note that Rust can also be build with an external precompiled version of LLVM
150 // which might lead to failures if the oldest tested / supported LLVM version
151 // doesn't yet support the relevant intrinsics
152 pub fn to_llvm_features<'a>(sess: &Session, s: &'a str) -> SmallVec<[&'a str; 2]> {
153 let arch = if sess.target.arch == "x86_64" { "x86" } else { &*sess.target.arch };
155 ("x86", "sse4.2") => {
156 if get_version() >= (14, 0, 0) {
157 smallvec!["sse4.2", "crc32"]
162 ("x86", "pclmulqdq") => smallvec!["pclmul"],
163 ("x86", "rdrand") => smallvec!["rdrnd"],
164 ("x86", "bmi1") => smallvec!["bmi"],
165 ("x86", "cmpxchg16b") => smallvec!["cx16"],
166 // FIXME: These aliases are misleading, and should be removed before avx512_target_feature is
167 // stabilized. They must remain until std::arch switches off them.
169 ("x86", "avx512vaes") => smallvec!["vaes"],
170 ("x86", "avx512gfni") => smallvec!["gfni"],
171 ("x86", "avx512vpclmulqdq") => smallvec!["vpclmulqdq"],
172 ("aarch64", "rcpc2") => smallvec!["rcpc-immo"],
173 ("aarch64", "dpb") => smallvec!["ccpp"],
174 ("aarch64", "dpb2") => smallvec!["ccdp"],
175 ("aarch64", "frintts") => smallvec!["fptoint"],
176 ("aarch64", "fcma") => smallvec!["complxnum"],
177 ("aarch64", "pmuv3") => smallvec!["perfmon"],
178 ("aarch64", "paca") => smallvec!["pauth"],
179 ("aarch64", "pacg") => smallvec!["pauth"],
180 // Rust ties fp and neon together. In LLVM neon implicitly enables fp,
181 // but we manually enable neon when a feature only implicitly enables fp
182 ("aarch64", "f32mm") => smallvec!["f32mm", "neon"],
183 ("aarch64", "f64mm") => smallvec!["f64mm", "neon"],
184 ("aarch64", "fhm") => smallvec!["fp16fml", "neon"],
185 ("aarch64", "fp16") => smallvec!["fullfp16", "neon"],
186 ("aarch64", "jsconv") => smallvec!["jsconv", "neon"],
187 ("aarch64", "sve") => smallvec!["sve", "neon"],
188 ("aarch64", "sve2") => smallvec!["sve2", "neon"],
189 ("aarch64", "sve2-aes") => smallvec!["sve2-aes", "neon"],
190 ("aarch64", "sve2-sm4") => smallvec!["sve2-sm4", "neon"],
191 ("aarch64", "sve2-sha3") => smallvec!["sve2-sha3", "neon"],
192 ("aarch64", "sve2-bitperm") => smallvec!["sve2-bitperm", "neon"],
193 (_, s) => smallvec![s],
197 /// Given a map from target_features to whether they are enabled or disabled,
198 /// ensure only valid combinations are allowed.
199 pub fn check_tied_features(
201 features: &FxHashMap<&str, bool>,
202 ) -> Option<&'static [&'static str]> {
203 if !features.is_empty() {
204 for tied in tied_target_features(sess) {
205 // Tied features must be set to the same value, or not set at all
206 let mut tied_iter = tied.iter();
207 let enabled = features.get(tied_iter.next().unwrap());
208 if tied_iter.any(|f| enabled != features.get(f)) {
216 /// Used to generate cfg variables and apply features
217 /// Must express features in the way Rust understands them
218 pub fn target_features(sess: &Session, allow_unstable: bool) -> Vec<Symbol> {
219 let target_machine = create_informational_target_machine(sess);
220 let mut features: Vec<Symbol> = supported_target_features(sess)
222 .filter_map(|&(feature, gate)| {
223 if sess.is_nightly_build() || allow_unstable || gate.is_none() {
230 // check that all features in a given smallvec are enabled
231 for llvm_feature in to_llvm_features(sess, feature) {
232 let cstr = SmallCStr::new(llvm_feature);
233 if !unsafe { llvm::LLVMRustHasFeature(target_machine, cstr.as_ptr()) } {
239 .map(|feature| Symbol::intern(feature))
242 // LLVM 14 changed the ABI for i128 arguments to __float/__fix builtins on Win64
243 // (see https://reviews.llvm.org/D110413). This unstable target feature is intended for use
244 // by compiler-builtins, to export the builtins with the expected, LLVM-version-dependent ABI.
245 // The target feature can be dropped once we no longer support older LLVM versions.
246 if sess.is_nightly_build() && get_version() >= (14, 0, 0) {
247 features.push(Symbol::intern("llvm14-builtins-abi"));
252 pub fn print_version() {
253 let (major, minor, patch) = get_version();
254 println!("LLVM version: {}.{}.{}", major, minor, patch);
257 pub fn get_version() -> (u32, u32, u32) {
258 // Can be called without initializing LLVM
260 (llvm::LLVMRustVersionMajor(), llvm::LLVMRustVersionMinor(), llvm::LLVMRustVersionPatch())
264 pub fn print_passes() {
265 // Can be called without initializing LLVM
267 llvm::LLVMRustPrintPasses();
271 fn llvm_target_features(tm: &llvm::TargetMachine) -> Vec<(&str, &str)> {
272 let len = unsafe { llvm::LLVMRustGetTargetFeaturesCount(tm) };
273 let mut ret = Vec::with_capacity(len);
276 let mut feature = ptr::null();
277 let mut desc = ptr::null();
278 llvm::LLVMRustGetTargetFeature(tm, i, &mut feature, &mut desc);
279 if feature.is_null() || desc.is_null() {
280 bug!("LLVM returned a `null` target feature string");
282 let feature = CStr::from_ptr(feature).to_str().unwrap_or_else(|e| {
283 bug!("LLVM returned a non-utf8 feature string: {}", e);
285 let desc = CStr::from_ptr(desc).to_str().unwrap_or_else(|e| {
286 bug!("LLVM returned a non-utf8 feature string: {}", e);
288 ret.push((feature, desc));
294 fn print_target_features(sess: &Session, tm: &llvm::TargetMachine) {
295 let mut llvm_target_features = llvm_target_features(tm);
296 let mut known_llvm_target_features = FxHashSet::<&'static str>::default();
297 let mut rustc_target_features = supported_target_features(sess)
299 .map(|(feature, _gate)| {
300 let desc = if let Some(llvm_feature) = to_llvm_features(sess, *feature).first() {
301 // LLVM asserts that these are sorted. LLVM and Rust both use byte comparison for these strings.
302 match llvm_target_features.binary_search_by_key(&llvm_feature, |(f, _d)| f).ok() {
304 known_llvm_target_features.insert(llvm_feature);
305 llvm_target_features[index].1
314 .collect::<Vec<_>>();
315 rustc_target_features.extend_from_slice(&[(
317 "Enables C Run-time Libraries to be statically linked",
319 llvm_target_features.retain(|(f, _d)| !known_llvm_target_features.contains(f));
321 let max_feature_len = llvm_target_features
323 .chain(rustc_target_features.iter())
324 .map(|(feature, _desc)| feature.len())
328 println!("Features supported by rustc for this target:");
329 for (feature, desc) in &rustc_target_features {
330 println!(" {1:0$} - {2}.", max_feature_len, feature, desc);
332 println!("\nCode-generation features supported by LLVM for this target:");
333 for (feature, desc) in &llvm_target_features {
334 println!(" {1:0$} - {2}.", max_feature_len, feature, desc);
336 if llvm_target_features.is_empty() {
337 println!(" Target features listing is not supported by this LLVM version.");
339 println!("\nUse +feature to enable a feature, or -feature to disable it.");
340 println!("For example, rustc -C target-cpu=mycpu -C target-feature=+feature1,-feature2\n");
341 println!("Code-generation features cannot be used in cfg or #[target_feature],");
342 println!("and may be renamed or removed in a future version of LLVM or rustc.\n");
345 pub(crate) fn print(req: PrintRequest, sess: &Session) {
347 let tm = create_informational_target_machine(sess);
349 PrintRequest::TargetCPUs => unsafe { llvm::LLVMRustPrintTargetCPUs(tm) },
350 PrintRequest::TargetFeatures => print_target_features(sess, tm),
351 _ => bug!("rustc_codegen_llvm can't handle print request: {:?}", req),
355 fn handle_native(name: &str) -> &str {
356 if name != "native" {
362 let ptr = llvm::LLVMRustGetHostCPUName(&mut len);
363 str::from_utf8(slice::from_raw_parts(ptr as *const u8, len)).unwrap()
367 pub fn target_cpu(sess: &Session) -> &str {
368 match sess.opts.cg.target_cpu {
369 Some(ref name) => handle_native(name),
370 None => handle_native(sess.target.cpu.as_ref()),
374 /// The list of LLVM features computed from CLI flags (`-Ctarget-cpu`, `-Ctarget-feature`,
375 /// `--target` and similar).
376 pub(crate) fn global_llvm_features(sess: &Session, diagnostics: bool) -> Vec<String> {
377 // Features that come earlier are overridden by conflicting features later in the string.
378 // Typically we'll want more explicit settings to override the implicit ones, so:
380 // * Features from -Ctarget-cpu=*; are overridden by [^1]
381 // * Features implied by --target; are overridden by
382 // * Features from -Ctarget-feature; are overridden by
383 // * function specific features.
385 // [^1]: target-cpu=native is handled here, other target-cpu values are handled implicitly
386 // through LLVM TargetMachine implementation.
388 // FIXME(nagisa): it isn't clear what's the best interaction between features implied by
389 // `-Ctarget-cpu` and `--target` are. On one hand, you'd expect CLI arguments to always
390 // override anything that's implicit, so e.g. when there's no `--target` flag, features implied
391 // the host target are overridden by `-Ctarget-cpu=*`. On the other hand, what about when both
392 // `--target` and `-Ctarget-cpu=*` are specified? Both then imply some target features and both
393 // flags are specified by the user on the CLI. It isn't as clear-cut which order of precedence
394 // should be taken in cases like these.
395 let mut features = vec![];
397 // -Ctarget-cpu=native
398 match sess.opts.cg.target_cpu {
399 Some(ref s) if s == "native" => {
400 let features_string = unsafe {
401 let ptr = llvm::LLVMGetHostCPUFeatures();
402 let features_string = if !ptr.is_null() {
405 .unwrap_or_else(|e| {
406 bug!("LLVM returned a non-utf8 features string: {}", e);
410 bug!("could not allocate host CPU features, LLVM returned a `null` string");
413 llvm::LLVMDisposeMessage(ptr);
417 features.extend(features_string.split(',').map(String::from));
422 // Features implied by an implicit or explicit `--target`.
427 .filter(|v| !v.is_empty() && backend_feature_name(v).is_some())
428 // Drop +atomics-32 feature introduced in LLVM 15.
429 .filter(|v| *v != "+atomics-32" || get_version() >= (15, 0, 0))
434 let supported_features = supported_target_features(sess);
435 let mut featsmap = FxHashMap::default();
442 let enable_disable = match s.chars().next() {
444 Some(c @ '+' | c @ '-') => c,
447 sess.emit_warning(UnknownCTargetFeaturePrefix { feature: s });
453 let feature = backend_feature_name(s)?;
454 // Warn against use of LLVM specific feature names on the CLI.
455 if diagnostics && !supported_features.iter().any(|&(v, _)| v == feature) {
456 let rust_feature = supported_features.iter().find_map(|&(rust_feature, _)| {
457 let llvm_features = to_llvm_features(sess, rust_feature);
458 if llvm_features.contains(&feature) && !llvm_features.contains(&rust_feature) {
464 let unknown_feature = if let Some(rust_feature) = rust_feature {
465 UnknownCTargetFeature {
467 rust_feature: PossibleFeature::Some { rust_feature },
470 UnknownCTargetFeature { feature, rust_feature: PossibleFeature::None }
472 sess.emit_warning(unknown_feature);
476 // FIXME(nagisa): figure out how to not allocate a full hashset here.
477 featsmap.insert(feature, enable_disable == '+');
480 // rustc-specific features do not get passed down to LLVM…
481 if RUSTC_SPECIFIC_FEATURES.contains(&feature) {
484 // ... otherwise though we run through `to_llvm_features` when
485 // passing requests down to LLVM. This means that all in-language
486 // features also work on the command line instead of having two
487 // different names when the LLVM name and the Rust name differ.
489 to_llvm_features(sess, feature)
491 .map(move |f| format!("{}{}", enable_disable, f)),
495 features.extend(feats);
497 if diagnostics && let Some(f) = check_tied_features(sess, &featsmap) {
498 sess.emit_err(TargetFeatureDisableOrEnable {
501 missing_features: None,
508 /// Returns a feature name for the given `+feature` or `-feature` string.
510 /// Only allows features that are backend specific (i.e. not [`RUSTC_SPECIFIC_FEATURES`].)
511 fn backend_feature_name(s: &str) -> Option<&str> {
512 // features must start with a `+` or `-`.
513 let feature = s.strip_prefix(&['+', '-'][..]).unwrap_or_else(|| {
514 bug!("target feature `{}` must begin with a `+` or `-`", s);
516 // Rustc-specific feature requests like `+crt-static` or `-crt-static`
517 // are not passed down to LLVM.
518 if RUSTC_SPECIFIC_FEATURES.contains(&feature) {
524 pub fn tune_cpu(sess: &Session) -> Option<&str> {
525 let name = sess.opts.unstable_opts.tune_cpu.as_ref()?;
526 Some(handle_native(name))