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::{supported_target_features, tied_target_features};
6 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
7 use rustc_fs_util::path_to_c_string;
9 use rustc_session::config::PrintRequest;
10 use rustc_session::Session;
11 use rustc_span::symbol::Symbol;
12 use rustc_target::spec::{MergeFunctions, PanicStrategy};
13 use std::ffi::{CStr, CString};
23 static INIT: Once = Once::new();
25 pub(crate) fn init(sess: &Session) {
27 // Before we touch LLVM, make sure that multithreading is enabled.
28 if llvm::LLVMIsMultithreaded() != 1 {
29 bug!("LLVM compiled without support for threads");
38 if !INIT.is_completed() {
39 bug!("LLVM is not initialized");
43 unsafe fn configure_llvm(sess: &Session) {
44 let n_args = sess.opts.cg.llvm_args.len() + sess.target.llvm_args.len();
45 let mut llvm_c_strs = Vec::with_capacity(n_args + 1);
46 let mut llvm_args = Vec::with_capacity(n_args + 1);
48 llvm::LLVMRustInstallFatalErrorHandler();
49 // On Windows, an LLVM assertion will open an Abort/Retry/Ignore dialog
50 // box for the purpose of launching a debugger. However, on CI this will
51 // cause it to hang until it times out, which can take several hours.
52 if std::env::var_os("CI").is_some() {
53 llvm::LLVMRustDisableSystemDialogsOnCrash();
56 fn llvm_arg_to_arg_name(full_arg: &str) -> &str {
57 full_arg.trim().split(|c: char| c == '=' || c.is_whitespace()).next().unwrap_or("")
60 let cg_opts = sess.opts.cg.llvm_args.iter();
61 let tg_opts = sess.target.llvm_args.iter();
62 let sess_args = cg_opts.chain(tg_opts);
64 let user_specified_args: FxHashSet<_> =
65 sess_args.clone().map(|s| llvm_arg_to_arg_name(s)).filter(|s| !s.is_empty()).collect();
68 // This adds the given argument to LLVM. Unless `force` is true
69 // user specified arguments are *not* overridden.
70 let mut add = |arg: &str, force: bool| {
71 if force || !user_specified_args.contains(llvm_arg_to_arg_name(arg)) {
72 let s = CString::new(arg).unwrap();
73 llvm_args.push(s.as_ptr());
77 // Set the llvm "program name" to make usage and invalid argument messages more clear.
78 add("rustc -Cllvm-args=\"...\" with", true);
79 if sess.time_llvm_passes() {
80 add("-time-passes", false);
82 if sess.print_llvm_passes() {
83 add("-debug-pass=Structure", false);
85 if sess.target.generate_arange_section
86 && !sess.opts.debugging_opts.no_generate_arange_section
88 add("-generate-arange-section", false);
91 // Disable the machine outliner by default in LLVM versions 11 and LLVM
92 // version 12, where it leads to miscompilation.
95 // - https://github.com/rust-lang/rust/issues/85351
96 // - https://reviews.llvm.org/D103167
97 if llvm_util::get_version() < (13, 0, 0) {
98 add("-enable-machine-outliner=never", false);
101 match sess.opts.debugging_opts.merge_functions.unwrap_or(sess.target.merge_functions) {
102 MergeFunctions::Disabled | MergeFunctions::Trampolines => {}
103 MergeFunctions::Aliases => {
104 add("-mergefunc-use-aliases", false);
108 if sess.target.os == "emscripten" && sess.panic_strategy() == PanicStrategy::Unwind {
109 add("-enable-emscripten-cxx-exceptions", false);
112 // HACK(eddyb) LLVM inserts `llvm.assume` calls to preserve align attributes
113 // during inlining. Unfortunately these may block other optimizations.
114 add("-preserve-alignment-assumptions-during-inlining=false", false);
116 // Use non-zero `import-instr-limit` multiplier for cold callsites.
117 add("-import-cold-multiplier=0.1", false);
119 for arg in sess_args {
124 if sess.opts.debugging_opts.llvm_time_trace {
125 llvm::LLVMTimeTraceProfilerInitialize();
128 llvm::LLVMInitializePasses();
130 // Use the legacy plugin registration if we don't use the new pass manager
131 if !should_use_new_llvm_pass_manager(
132 &sess.opts.debugging_opts.new_llvm_pass_manager,
135 // Register LLVM plugins by loading them into the compiler process.
136 for plugin in &sess.opts.debugging_opts.llvm_plugins {
137 let lib = Library::new(plugin).unwrap_or_else(|e| bug!("couldn't load plugin: {}", e));
138 debug!("LLVM plugin loaded successfully {:?} ({})", lib, plugin);
140 // Intentionally leak the dynamic library. We can't ever unload it
141 // since the library can make things that will live arbitrarily long.
146 rustc_llvm::initialize_available_targets();
148 llvm::LLVMRustSetLLVMOptions(llvm_args.len() as c_int, llvm_args.as_ptr());
151 pub fn time_trace_profiler_finish(file_name: &Path) {
153 let file_name = path_to_c_string(file_name);
154 llvm::LLVMTimeTraceProfilerFinish(file_name.as_ptr());
158 // WARNING: the features after applying `to_llvm_feature` must be known
159 // to LLVM or the feature detection code will walk past the end of the feature
160 // array, leading to crashes.
161 // To find a list of LLVM's names, check llvm-project/llvm/include/llvm/Support/*TargetParser.def
162 // where the * matches the architecture's name
163 // Beware to not use the llvm github project for this, but check the git submodule
164 // found in src/llvm-project
165 // Though note that Rust can also be build with an external precompiled version of LLVM
166 // which might lead to failures if the oldest tested / supported LLVM version
167 // doesn't yet support the relevant intrinsics
168 pub fn to_llvm_feature<'a>(sess: &Session, s: &'a str) -> Vec<&'a str> {
169 let arch = if sess.target.arch == "x86_64" { "x86" } else { &*sess.target.arch };
171 ("x86", "sse4.2") => {
172 if get_version() >= (14, 0, 0) {
173 vec!["sse4.2", "crc32"]
178 ("x86", "pclmulqdq") => vec!["pclmul"],
179 ("x86", "rdrand") => vec!["rdrnd"],
180 ("x86", "bmi1") => vec!["bmi"],
181 ("x86", "cmpxchg16b") => vec!["cx16"],
182 ("x86", "avx512vaes") => vec!["vaes"],
183 ("x86", "avx512gfni") => vec!["gfni"],
184 ("x86", "avx512vpclmulqdq") => vec!["vpclmulqdq"],
185 ("aarch64", "fp") => vec!["fp-armv8"],
186 ("aarch64", "fp16") => vec!["fullfp16"],
187 ("aarch64", "fhm") => vec!["fp16fml"],
188 ("aarch64", "rcpc2") => vec!["rcpc-immo"],
189 ("aarch64", "dpb") => vec!["ccpp"],
190 ("aarch64", "dpb2") => vec!["ccdp"],
191 ("aarch64", "frintts") => vec!["fptoint"],
192 ("aarch64", "fcma") => vec!["complxnum"],
193 ("aarch64", "pmuv3") => vec!["perfmon"],
194 ("aarch64", "paca") => vec!["pauth"],
195 ("aarch64", "pacg") => vec!["pauth"],
200 // Given a map from target_features to whether they are enabled or disabled,
201 // ensure only valid combinations are allowed.
202 pub fn check_tied_features(
204 features: &FxHashMap<&str, bool>,
205 ) -> Option<&'static [&'static str]> {
206 for tied in tied_target_features(sess) {
207 // Tied features must be set to the same value, or not set at all
208 let mut tied_iter = tied.iter();
209 let enabled = features.get(tied_iter.next().unwrap());
211 if tied_iter.any(|f| enabled != features.get(f)) {
218 pub fn target_features(sess: &Session) -> Vec<Symbol> {
219 let target_machine = create_informational_target_machine(sess);
220 supported_target_features(sess)
224 if sess.is_nightly_build() || gate.is_none() { Some(feature) } else { None }
228 for llvm_feature in to_llvm_feature(sess, feature) {
229 let cstr = CString::new(llvm_feature).unwrap();
230 if unsafe { llvm::LLVMRustHasFeature(target_machine, cstr.as_ptr()) } {
236 .map(|feature| Symbol::intern(feature))
240 pub fn print_version() {
241 let (major, minor, patch) = get_version();
242 println!("LLVM version: {}.{}.{}", major, minor, patch);
245 pub fn get_version() -> (u32, u32, u32) {
246 // Can be called without initializing LLVM
248 (llvm::LLVMRustVersionMajor(), llvm::LLVMRustVersionMinor(), llvm::LLVMRustVersionPatch())
252 /// Returns `true` if this LLVM is Rust's bundled LLVM (and not system LLVM).
253 pub fn is_rust_llvm() -> bool {
254 // Can be called without initializing LLVM
255 unsafe { llvm::LLVMRustIsRustLLVM() }
258 pub fn print_passes() {
259 // Can be called without initializing LLVM
261 llvm::LLVMRustPrintPasses();
265 fn llvm_target_features(tm: &llvm::TargetMachine) -> Vec<(&str, &str)> {
266 let len = unsafe { llvm::LLVMRustGetTargetFeaturesCount(tm) };
267 let mut ret = Vec::with_capacity(len);
270 let mut feature = ptr::null();
271 let mut desc = ptr::null();
272 llvm::LLVMRustGetTargetFeature(tm, i, &mut feature, &mut desc);
273 if feature.is_null() || desc.is_null() {
274 bug!("LLVM returned a `null` target feature string");
276 let feature = CStr::from_ptr(feature).to_str().unwrap_or_else(|e| {
277 bug!("LLVM returned a non-utf8 feature string: {}", e);
279 let desc = CStr::from_ptr(desc).to_str().unwrap_or_else(|e| {
280 bug!("LLVM returned a non-utf8 feature string: {}", e);
282 ret.push((feature, desc));
288 fn print_target_features(sess: &Session, tm: &llvm::TargetMachine) {
289 let mut target_features = llvm_target_features(tm);
290 let mut rustc_target_features = supported_target_features(sess)
292 .filter_map(|(feature, _gate)| {
293 for llvm_feature in to_llvm_feature(sess, *feature) {
294 // LLVM asserts that these are sorted. LLVM and Rust both use byte comparison for these strings.
295 match target_features.binary_search_by_key(&llvm_feature, |(f, _d)| (*f)).ok().map(
297 let (_f, desc) = target_features.remove(index);
301 Some(v) => return Some(v),
307 .collect::<Vec<_>>();
308 rustc_target_features.extend_from_slice(&[(
310 "Enables C Run-time Libraries to be statically linked",
312 let max_feature_len = target_features
314 .chain(rustc_target_features.iter())
315 .map(|(feature, _desc)| feature.len())
319 println!("Features supported by rustc for this target:");
320 for (feature, desc) in &rustc_target_features {
321 println!(" {1:0$} - {2}.", max_feature_len, feature, desc);
323 println!("\nCode-generation features supported by LLVM for this target:");
324 for (feature, desc) in &target_features {
325 println!(" {1:0$} - {2}.", max_feature_len, feature, desc);
327 if target_features.is_empty() {
328 println!(" Target features listing is not supported by this LLVM version.");
330 println!("\nUse +feature to enable a feature, or -feature to disable it.");
331 println!("For example, rustc -C target-cpu=mycpu -C target-feature=+feature1,-feature2\n");
332 println!("Code-generation features cannot be used in cfg or #[target_feature],");
333 println!("and may be renamed or removed in a future version of LLVM or rustc.\n");
336 pub(crate) fn print(req: PrintRequest, sess: &Session) {
338 let tm = create_informational_target_machine(sess);
340 PrintRequest::TargetCPUs => unsafe { llvm::LLVMRustPrintTargetCPUs(tm) },
341 PrintRequest::TargetFeatures => print_target_features(sess, tm),
342 _ => bug!("rustc_codegen_llvm can't handle print request: {:?}", req),
346 fn handle_native(name: &str) -> &str {
347 if name != "native" {
353 let ptr = llvm::LLVMRustGetHostCPUName(&mut len);
354 str::from_utf8(slice::from_raw_parts(ptr as *const u8, len)).unwrap()
358 pub fn target_cpu(sess: &Session) -> &str {
359 let name = sess.opts.cg.target_cpu.as_ref().unwrap_or(&sess.target.cpu);
363 /// The list of LLVM features computed from CLI flags (`-Ctarget-cpu`, `-Ctarget-feature`,
364 /// `--target` and similar).
365 // FIXME(nagisa): Cache the output of this somehow? Maybe make this a query? We're calling this
366 // for every function that has `#[target_feature]` on it. The global features won't change between
367 // the functions; only crates, maybe…
368 pub fn llvm_global_features(sess: &Session) -> Vec<String> {
369 // FIXME(nagisa): this should definitely be available more centrally and to other codegen backends.
370 /// These features control behaviour of rustc rather than llvm.
371 const RUSTC_SPECIFIC_FEATURES: &[&str] = &["crt-static"];
373 // Features that come earlier are overriden by conflicting features later in the string.
374 // Typically we'll want more explicit settings to override the implicit ones, so:
376 // * Features from -Ctarget-cpu=*; are overriden by [^1]
377 // * Features implied by --target; are overriden by
378 // * Features from -Ctarget-feature; are overriden by
379 // * function specific features.
381 // [^1]: target-cpu=native is handled here, other target-cpu values are handled implicitly
382 // through LLVM TargetMachine implementation.
384 // FIXME(nagisa): it isn't clear what's the best interaction between features implied by
385 // `-Ctarget-cpu` and `--target` are. On one hand, you'd expect CLI arguments to always
386 // override anything that's implicit, so e.g. when there's no `--target` flag, features implied
387 // the host target are overriden by `-Ctarget-cpu=*`. On the other hand, what about when both
388 // `--target` and `-Ctarget-cpu=*` are specified? Both then imply some target features and both
389 // flags are specified by the user on the CLI. It isn't as clear-cut which order of precedence
390 // should be taken in cases like these.
391 let mut features = vec![];
393 // -Ctarget-cpu=native
394 match sess.opts.cg.target_cpu {
395 Some(ref s) if s == "native" => {
396 let features_string = unsafe {
397 let ptr = llvm::LLVMGetHostCPUFeatures();
398 let features_string = if !ptr.is_null() {
401 .unwrap_or_else(|e| {
402 bug!("LLVM returned a non-utf8 features string: {}", e);
406 bug!("could not allocate host CPU features, LLVM returned a `null` string");
409 llvm::LLVMDisposeMessage(ptr);
413 features.extend(features_string.split(',').map(String::from));
418 fn strip(s: &str) -> &str {
419 s.strip_prefix(&['+', '-']).unwrap_or(s)
422 let filter = |s: &str| {
426 let feature = strip(s);
428 return vec![s.to_string()];
431 // Rustc-specific feature requests like `+crt-static` or `-crt-static`
432 // are not passed down to LLVM.
433 if RUSTC_SPECIFIC_FEATURES.contains(&feature) {
436 // ... otherwise though we run through `to_llvm_feature` feature when
437 // passing requests down to LLVM. This means that all in-language
438 // features also work on the command line instead of having two
439 // different names when the LLVM name and the Rust name differ.
440 to_llvm_feature(sess, feature).iter().map(|f| format!("{}{}", &s[..1], f)).collect()
443 // Features implied by an implicit or explicit `--target`.
444 features.extend(sess.target.features.split(',').flat_map(&filter));
447 let feats: Vec<&str> = sess.opts.cg.target_feature.split(',').collect();
448 // LLVM enables based on the last occurence of a feature
450 check_tied_features(sess, &feats.iter().map(|f| (strip(f), !f.starts_with("-"))).collect())
453 "Target features {} must all be enabled or disabled together",
457 features.extend(feats.iter().flat_map(|&f| filter(f)));
461 pub fn tune_cpu(sess: &Session) -> Option<&str> {
462 let name = sess.opts.debugging_opts.tune_cpu.as_ref()?;
463 Some(handle_native(name))
466 pub(crate) fn should_use_new_llvm_pass_manager(user_opt: &Option<bool>, target_arch: &str) -> bool {
467 // The new pass manager is enabled by default for LLVM >= 13.
468 // This matches Clang, which also enables it since Clang 13.
470 // FIXME: There are some perf issues with the new pass manager
471 // when targeting s390x, so it is temporarily disabled for that
472 // arch, see https://github.com/rust-lang/rust/issues/89609
473 user_opt.unwrap_or_else(|| target_arch != "s390x" && llvm_util::get_version() >= (13, 0, 0))