1 use crate::back::write::create_informational_target_machine;
2 use crate::{llvm, llvm_util};
4 use rustc_codegen_ssa::target_features::supported_target_features;
5 use rustc_data_structures::fx::FxHashSet;
6 use rustc_metadata::dynamic_lib::DynamicLibrary;
8 use rustc_session::config::PrintRequest;
9 use rustc_session::Session;
10 use rustc_span::symbol::Symbol;
11 use rustc_target::spec::{MergeFunctions, PanicStrategy};
12 use std::ffi::{CStr, CString};
20 use std::sync::atomic::{AtomicBool, Ordering};
23 static POISONED: AtomicBool = AtomicBool::new(false);
24 static INIT: Once = Once::new();
26 pub(crate) fn init(sess: &Session) {
28 // Before we touch LLVM, make sure that multithreading is enabled.
30 if llvm::LLVMStartMultithreaded() != 1 {
31 // use an extra bool to make sure that all future usage of LLVM
32 // cannot proceed despite the Once not running more than once.
33 POISONED.store(true, Ordering::SeqCst);
39 if POISONED.load(Ordering::SeqCst) {
40 bug!("couldn't enable multi-threaded LLVM");
46 INIT.call_once(|| bug!("llvm is not initialized"));
47 if POISONED.load(Ordering::SeqCst) {
48 bug!("couldn't enable multi-threaded LLVM");
52 unsafe fn configure_llvm(sess: &Session) {
53 let n_args = sess.opts.cg.llvm_args.len() + sess.target.llvm_args.len();
54 let mut llvm_c_strs = Vec::with_capacity(n_args + 1);
55 let mut llvm_args = Vec::with_capacity(n_args + 1);
57 llvm::LLVMRustInstallFatalErrorHandler();
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();
64 let tg_opts = sess.target.llvm_args.iter();
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.opts.debugging_opts.no_generate_arange_section {
89 add("-generate-arange-section", false);
92 // Disable the machine outliner by default in LLVM versions 11 and LLVM
93 // version 12, where it leads to miscompilation.
96 // - https://github.com/rust-lang/rust/issues/85351
97 // - https://reviews.llvm.org/D103167
98 if llvm_util::get_version() < (13, 0, 0) {
99 add("-enable-machine-outliner=never", false);
102 match sess.opts.debugging_opts.merge_functions.unwrap_or(sess.target.merge_functions) {
103 MergeFunctions::Disabled | MergeFunctions::Trampolines => {}
104 MergeFunctions::Aliases => {
105 add("-mergefunc-use-aliases", false);
109 if sess.target.os == "emscripten" && sess.panic_strategy() == PanicStrategy::Unwind {
110 add("-enable-emscripten-cxx-exceptions", false);
113 // HACK(eddyb) LLVM inserts `llvm.assume` calls to preserve align attributes
114 // during inlining. Unfortunately these may block other optimizations.
115 add("-preserve-alignment-assumptions-during-inlining=false", false);
117 // Use non-zero `import-instr-limit` multiplier for cold callsites.
118 add("-import-cold-multiplier=0.1", false);
120 for arg in sess_args {
125 if sess.opts.debugging_opts.llvm_time_trace {
126 // time-trace is not thread safe and running it in parallel will cause seg faults.
127 if !sess.opts.debugging_opts.no_parallel_llvm {
128 bug!("`-Z llvm-time-trace` requires `-Z no-parallel-llvm")
131 llvm::LLVMTimeTraceProfilerInitialize();
134 llvm::LLVMInitializePasses();
136 for plugin in &sess.opts.debugging_opts.llvm_plugins {
137 let path = Path::new(plugin);
138 let res = DynamicLibrary::open(path);
140 Ok(_) => debug!("LLVM plugin loaded succesfully {} ({})", path.display(), plugin),
141 Err(e) => bug!("couldn't load plugin: {}", e),
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: &str) {
153 let file_name = CString::new(file_name).unwrap();
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"],
197 pub fn target_features(sess: &Session) -> Vec<Symbol> {
198 let target_machine = create_informational_target_machine(sess);
199 supported_target_features(sess)
203 if sess.is_nightly_build() || gate.is_none() { Some(feature) } else { None }
207 for llvm_feature in to_llvm_feature(sess, feature) {
208 let cstr = CString::new(llvm_feature).unwrap();
209 if unsafe { llvm::LLVMRustHasFeature(target_machine, cstr.as_ptr()) } {
215 .map(|feature| Symbol::intern(feature))
219 pub fn print_version() {
220 let (major, minor, patch) = get_version();
221 println!("LLVM version: {}.{}.{}", major, minor, patch);
224 pub fn get_version() -> (u32, u32, u32) {
225 // Can be called without initializing LLVM
227 (llvm::LLVMRustVersionMajor(), llvm::LLVMRustVersionMinor(), llvm::LLVMRustVersionPatch())
231 pub fn print_passes() {
232 // Can be called without initializing LLVM
234 llvm::LLVMRustPrintPasses();
238 fn llvm_target_features(tm: &llvm::TargetMachine) -> Vec<(&str, &str)> {
239 let len = unsafe { llvm::LLVMRustGetTargetFeaturesCount(tm) };
240 let mut ret = Vec::with_capacity(len);
243 let mut feature = ptr::null();
244 let mut desc = ptr::null();
245 llvm::LLVMRustGetTargetFeature(tm, i, &mut feature, &mut desc);
246 if feature.is_null() || desc.is_null() {
247 bug!("LLVM returned a `null` target feature string");
249 let feature = CStr::from_ptr(feature).to_str().unwrap_or_else(|e| {
250 bug!("LLVM returned a non-utf8 feature string: {}", e);
252 let desc = CStr::from_ptr(desc).to_str().unwrap_or_else(|e| {
253 bug!("LLVM returned a non-utf8 feature string: {}", e);
255 ret.push((feature, desc));
261 fn print_target_features(sess: &Session, tm: &llvm::TargetMachine) {
262 let mut target_features = llvm_target_features(tm);
263 let mut rustc_target_features = supported_target_features(sess)
265 .filter_map(|(feature, _gate)| {
266 for llvm_feature in to_llvm_feature(sess, *feature) {
267 // LLVM asserts that these are sorted. LLVM and Rust both use byte comparison for these strings.
268 match target_features.binary_search_by_key(&llvm_feature, |(f, _d)| (*f)).ok().map(
270 let (_f, desc) = target_features.remove(index);
274 Some(v) => return Some(v),
280 .collect::<Vec<_>>();
281 rustc_target_features.extend_from_slice(&[(
283 "Enables C Run-time Libraries to be statically linked",
285 let max_feature_len = target_features
287 .chain(rustc_target_features.iter())
288 .map(|(feature, _desc)| feature.len())
292 println!("Features supported by rustc for this target:");
293 for (feature, desc) in &rustc_target_features {
294 println!(" {1:0$} - {2}.", max_feature_len, feature, desc);
296 println!("\nCode-generation features supported by LLVM for this target:");
297 for (feature, desc) in &target_features {
298 println!(" {1:0$} - {2}.", max_feature_len, feature, desc);
300 if target_features.is_empty() {
301 println!(" Target features listing is not supported by this LLVM version.");
303 println!("\nUse +feature to enable a feature, or -feature to disable it.");
304 println!("For example, rustc -C target-cpu=mycpu -C target-feature=+feature1,-feature2\n");
305 println!("Code-generation features cannot be used in cfg or #[target_feature],");
306 println!("and may be renamed or removed in a future version of LLVM or rustc.\n");
309 pub(crate) fn print(req: PrintRequest, sess: &Session) {
311 let tm = create_informational_target_machine(sess);
313 PrintRequest::TargetCPUs => unsafe { llvm::LLVMRustPrintTargetCPUs(tm) },
314 PrintRequest::TargetFeatures => print_target_features(sess, tm),
315 _ => bug!("rustc_codegen_llvm can't handle print request: {:?}", req),
319 fn handle_native(name: &str) -> &str {
320 if name != "native" {
326 let ptr = llvm::LLVMRustGetHostCPUName(&mut len);
327 str::from_utf8(slice::from_raw_parts(ptr as *const u8, len)).unwrap()
331 pub fn target_cpu(sess: &Session) -> &str {
332 let name = sess.opts.cg.target_cpu.as_ref().unwrap_or(&sess.target.cpu);
336 /// The list of LLVM features computed from CLI flags (`-Ctarget-cpu`, `-Ctarget-feature`,
337 /// `--target` and similar).
338 // FIXME(nagisa): Cache the output of this somehow? Maybe make this a query? We're calling this
339 // for every function that has `#[target_feature]` on it. The global features won't change between
340 // the functions; only crates, maybe…
341 pub fn llvm_global_features(sess: &Session) -> Vec<String> {
342 // FIXME(nagisa): this should definitely be available more centrally and to other codegen backends.
343 /// These features control behaviour of rustc rather than llvm.
344 const RUSTC_SPECIFIC_FEATURES: &[&str] = &["crt-static"];
346 // Features that come earlier are overriden by conflicting features later in the string.
347 // Typically we'll want more explicit settings to override the implicit ones, so:
349 // * Features from -Ctarget-cpu=*; are overriden by [^1]
350 // * Features implied by --target; are overriden by
351 // * Features from -Ctarget-feature; are overriden by
352 // * function specific features.
354 // [^1]: target-cpu=native is handled here, other target-cpu values are handled implicitly
355 // through LLVM TargetMachine implementation.
357 // FIXME(nagisa): it isn't clear what's the best interaction between features implied by
358 // `-Ctarget-cpu` and `--target` are. On one hand, you'd expect CLI arguments to always
359 // override anything that's implicit, so e.g. when there's no `--target` flag, features implied
360 // the host target are overriden by `-Ctarget-cpu=*`. On the other hand, what about when both
361 // `--target` and `-Ctarget-cpu=*` are specified? Both then imply some target features and both
362 // flags are specified by the user on the CLI. It isn't as clear-cut which order of precedence
363 // should be taken in cases like these.
364 let mut features = vec![];
366 // -Ctarget-cpu=native
367 match sess.opts.cg.target_cpu {
368 Some(ref s) if s == "native" => {
369 let features_string = unsafe {
370 let ptr = llvm::LLVMGetHostCPUFeatures();
371 let features_string = if !ptr.is_null() {
374 .unwrap_or_else(|e| {
375 bug!("LLVM returned a non-utf8 features string: {}", e);
379 bug!("could not allocate host CPU features, LLVM returned a `null` string");
382 llvm::LLVMDisposeMessage(ptr);
386 features.extend(features_string.split(',').map(String::from));
391 let filter = |s: &str| {
395 let feature = if s.starts_with('+') || s.starts_with('-') {
398 return vec![s.to_string()];
400 // Rustc-specific feature requests like `+crt-static` or `-crt-static`
401 // are not passed down to LLVM.
402 if RUSTC_SPECIFIC_FEATURES.contains(&feature) {
405 // ... otherwise though we run through `to_llvm_feature` feature when
406 // passing requests down to LLVM. This means that all in-language
407 // features also work on the command line instead of having two
408 // different names when the LLVM name and the Rust name differ.
409 to_llvm_feature(sess, feature).iter().map(|f| format!("{}{}", &s[..1], f)).collect()
412 // Features implied by an implicit or explicit `--target`.
413 features.extend(sess.target.features.split(',').flat_map(&filter));
416 features.extend(sess.opts.cg.target_feature.split(',').flat_map(&filter));
418 // FIXME: Move outline-atomics to target definition when earliest supported LLVM is 12.
419 if get_version() >= (12, 0, 0) && sess.target.llvm_target.contains("aarch64-unknown-linux") {
420 features.push("+outline-atomics".to_string());
426 pub fn tune_cpu(sess: &Session) -> Option<&str> {
427 let name = sess.opts.debugging_opts.tune_cpu.as_ref()?;
428 Some(handle_native(name))