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;
6 use rustc_data_structures::fx::FxHashSet;
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};
21 static INIT: Once = Once::new();
23 pub(crate) fn init(sess: &Session) {
25 // Before we touch LLVM, make sure that multithreading is enabled.
26 if llvm::LLVMIsMultithreaded() != 1 {
27 bug!("LLVM compiled without support for threads");
36 if !INIT.is_completed() {
37 bug!("LLVM is not initialized");
41 unsafe fn configure_llvm(sess: &Session) {
42 let n_args = sess.opts.cg.llvm_args.len() + sess.target.llvm_args.len();
43 let mut llvm_c_strs = Vec::with_capacity(n_args + 1);
44 let mut llvm_args = Vec::with_capacity(n_args + 1);
46 llvm::LLVMRustInstallFatalErrorHandler();
48 fn llvm_arg_to_arg_name(full_arg: &str) -> &str {
49 full_arg.trim().split(|c: char| c == '=' || c.is_whitespace()).next().unwrap_or("")
52 let cg_opts = sess.opts.cg.llvm_args.iter();
53 let tg_opts = sess.target.llvm_args.iter();
54 let sess_args = cg_opts.chain(tg_opts);
56 let user_specified_args: FxHashSet<_> =
57 sess_args.clone().map(|s| llvm_arg_to_arg_name(s)).filter(|s| !s.is_empty()).collect();
60 // This adds the given argument to LLVM. Unless `force` is true
61 // user specified arguments are *not* overridden.
62 let mut add = |arg: &str, force: bool| {
63 if force || !user_specified_args.contains(llvm_arg_to_arg_name(arg)) {
64 let s = CString::new(arg).unwrap();
65 llvm_args.push(s.as_ptr());
69 // Set the llvm "program name" to make usage and invalid argument messages more clear.
70 add("rustc -Cllvm-args=\"...\" with", true);
71 if sess.time_llvm_passes() {
72 add("-time-passes", false);
74 if sess.print_llvm_passes() {
75 add("-debug-pass=Structure", false);
77 if sess.target.generate_arange_section
78 && !sess.opts.debugging_opts.no_generate_arange_section
80 add("-generate-arange-section", false);
83 // Disable the machine outliner by default in LLVM versions 11 and LLVM
84 // version 12, where it leads to miscompilation.
87 // - https://github.com/rust-lang/rust/issues/85351
88 // - https://reviews.llvm.org/D103167
89 if llvm_util::get_version() < (13, 0, 0) {
90 add("-enable-machine-outliner=never", false);
93 match sess.opts.debugging_opts.merge_functions.unwrap_or(sess.target.merge_functions) {
94 MergeFunctions::Disabled | MergeFunctions::Trampolines => {}
95 MergeFunctions::Aliases => {
96 add("-mergefunc-use-aliases", false);
100 if sess.target.os == "emscripten" && sess.panic_strategy() == PanicStrategy::Unwind {
101 add("-enable-emscripten-cxx-exceptions", false);
104 // HACK(eddyb) LLVM inserts `llvm.assume` calls to preserve align attributes
105 // during inlining. Unfortunately these may block other optimizations.
106 add("-preserve-alignment-assumptions-during-inlining=false", false);
108 // Use non-zero `import-instr-limit` multiplier for cold callsites.
109 add("-import-cold-multiplier=0.1", false);
111 for arg in sess_args {
116 if sess.opts.debugging_opts.llvm_time_trace {
117 llvm::LLVMTimeTraceProfilerInitialize();
120 llvm::LLVMInitializePasses();
122 // Register LLVM plugins by loading them into the compiler process.
123 for plugin in &sess.opts.debugging_opts.llvm_plugins {
124 let lib = Library::new(plugin).unwrap_or_else(|e| bug!("couldn't load plugin: {}", e));
125 debug!("LLVM plugin loaded successfully {:?} ({})", lib, plugin);
127 // Intentionally leak the dynamic library. We can't ever unload it
128 // since the library can make things that will live arbitrarily long.
132 rustc_llvm::initialize_available_targets();
134 llvm::LLVMRustSetLLVMOptions(llvm_args.len() as c_int, llvm_args.as_ptr());
137 pub fn time_trace_profiler_finish(file_name: &str) {
139 let file_name = CString::new(file_name).unwrap();
140 llvm::LLVMTimeTraceProfilerFinish(file_name.as_ptr());
144 // WARNING: the features after applying `to_llvm_feature` must be known
145 // to LLVM or the feature detection code will walk past the end of the feature
146 // array, leading to crashes.
147 // To find a list of LLVM's names, check llvm-project/llvm/include/llvm/Support/*TargetParser.def
148 // where the * matches the architecture's name
149 // Beware to not use the llvm github project for this, but check the git submodule
150 // found in src/llvm-project
151 // Though note that Rust can also be build with an external precompiled version of LLVM
152 // which might lead to failures if the oldest tested / supported LLVM version
153 // doesn't yet support the relevant intrinsics
154 pub fn to_llvm_feature<'a>(sess: &Session, s: &'a str) -> Vec<&'a str> {
155 let arch = if sess.target.arch == "x86_64" { "x86" } else { &*sess.target.arch };
157 ("x86", "sse4.2") => {
158 if get_version() >= (14, 0, 0) {
159 vec!["sse4.2", "crc32"]
164 ("x86", "pclmulqdq") => vec!["pclmul"],
165 ("x86", "rdrand") => vec!["rdrnd"],
166 ("x86", "bmi1") => vec!["bmi"],
167 ("x86", "cmpxchg16b") => vec!["cx16"],
168 ("x86", "avx512vaes") => vec!["vaes"],
169 ("x86", "avx512gfni") => vec!["gfni"],
170 ("x86", "avx512vpclmulqdq") => vec!["vpclmulqdq"],
171 ("aarch64", "fp") => vec!["fp-armv8"],
172 ("aarch64", "fp16") => vec!["fullfp16"],
173 ("aarch64", "fhm") => vec!["fp16fml"],
174 ("aarch64", "rcpc2") => vec!["rcpc-immo"],
175 ("aarch64", "dpb") => vec!["ccpp"],
176 ("aarch64", "dpb2") => vec!["ccdp"],
177 ("aarch64", "frintts") => vec!["fptoint"],
178 ("aarch64", "fcma") => vec!["complxnum"],
179 ("aarch64", "pmuv3") => vec!["perfmon"],
184 pub fn target_features(sess: &Session) -> Vec<Symbol> {
185 let target_machine = create_informational_target_machine(sess);
186 supported_target_features(sess)
190 if sess.is_nightly_build() || gate.is_none() { Some(feature) } else { None }
194 for llvm_feature in to_llvm_feature(sess, feature) {
195 let cstr = CString::new(llvm_feature).unwrap();
196 if unsafe { llvm::LLVMRustHasFeature(target_machine, cstr.as_ptr()) } {
202 .map(|feature| Symbol::intern(feature))
206 pub fn print_version() {
207 let (major, minor, patch) = get_version();
208 println!("LLVM version: {}.{}.{}", major, minor, patch);
211 pub fn get_version() -> (u32, u32, u32) {
212 // Can be called without initializing LLVM
214 (llvm::LLVMRustVersionMajor(), llvm::LLVMRustVersionMinor(), llvm::LLVMRustVersionPatch())
218 pub fn print_passes() {
219 // Can be called without initializing LLVM
221 llvm::LLVMRustPrintPasses();
225 fn llvm_target_features(tm: &llvm::TargetMachine) -> Vec<(&str, &str)> {
226 let len = unsafe { llvm::LLVMRustGetTargetFeaturesCount(tm) };
227 let mut ret = Vec::with_capacity(len);
230 let mut feature = ptr::null();
231 let mut desc = ptr::null();
232 llvm::LLVMRustGetTargetFeature(tm, i, &mut feature, &mut desc);
233 if feature.is_null() || desc.is_null() {
234 bug!("LLVM returned a `null` target feature string");
236 let feature = CStr::from_ptr(feature).to_str().unwrap_or_else(|e| {
237 bug!("LLVM returned a non-utf8 feature string: {}", e);
239 let desc = CStr::from_ptr(desc).to_str().unwrap_or_else(|e| {
240 bug!("LLVM returned a non-utf8 feature string: {}", e);
242 ret.push((feature, desc));
248 fn print_target_features(sess: &Session, tm: &llvm::TargetMachine) {
249 let mut target_features = llvm_target_features(tm);
250 let mut rustc_target_features = supported_target_features(sess)
252 .filter_map(|(feature, _gate)| {
253 for llvm_feature in to_llvm_feature(sess, *feature) {
254 // LLVM asserts that these are sorted. LLVM and Rust both use byte comparison for these strings.
255 match target_features.binary_search_by_key(&llvm_feature, |(f, _d)| (*f)).ok().map(
257 let (_f, desc) = target_features.remove(index);
261 Some(v) => return Some(v),
267 .collect::<Vec<_>>();
268 rustc_target_features.extend_from_slice(&[(
270 "Enables C Run-time Libraries to be statically linked",
272 let max_feature_len = target_features
274 .chain(rustc_target_features.iter())
275 .map(|(feature, _desc)| feature.len())
279 println!("Features supported by rustc for this target:");
280 for (feature, desc) in &rustc_target_features {
281 println!(" {1:0$} - {2}.", max_feature_len, feature, desc);
283 println!("\nCode-generation features supported by LLVM for this target:");
284 for (feature, desc) in &target_features {
285 println!(" {1:0$} - {2}.", max_feature_len, feature, desc);
287 if target_features.is_empty() {
288 println!(" Target features listing is not supported by this LLVM version.");
290 println!("\nUse +feature to enable a feature, or -feature to disable it.");
291 println!("For example, rustc -C target-cpu=mycpu -C target-feature=+feature1,-feature2\n");
292 println!("Code-generation features cannot be used in cfg or #[target_feature],");
293 println!("and may be renamed or removed in a future version of LLVM or rustc.\n");
296 pub(crate) fn print(req: PrintRequest, sess: &Session) {
298 let tm = create_informational_target_machine(sess);
300 PrintRequest::TargetCPUs => unsafe { llvm::LLVMRustPrintTargetCPUs(tm) },
301 PrintRequest::TargetFeatures => print_target_features(sess, tm),
302 _ => bug!("rustc_codegen_llvm can't handle print request: {:?}", req),
306 fn handle_native(name: &str) -> &str {
307 if name != "native" {
313 let ptr = llvm::LLVMRustGetHostCPUName(&mut len);
314 str::from_utf8(slice::from_raw_parts(ptr as *const u8, len)).unwrap()
318 pub fn target_cpu(sess: &Session) -> &str {
319 let name = sess.opts.cg.target_cpu.as_ref().unwrap_or(&sess.target.cpu);
323 /// The list of LLVM features computed from CLI flags (`-Ctarget-cpu`, `-Ctarget-feature`,
324 /// `--target` and similar).
325 // FIXME(nagisa): Cache the output of this somehow? Maybe make this a query? We're calling this
326 // for every function that has `#[target_feature]` on it. The global features won't change between
327 // the functions; only crates, maybe…
328 pub fn llvm_global_features(sess: &Session) -> Vec<String> {
329 // FIXME(nagisa): this should definitely be available more centrally and to other codegen backends.
330 /// These features control behaviour of rustc rather than llvm.
331 const RUSTC_SPECIFIC_FEATURES: &[&str] = &["crt-static"];
333 // Features that come earlier are overriden by conflicting features later in the string.
334 // Typically we'll want more explicit settings to override the implicit ones, so:
336 // * Features from -Ctarget-cpu=*; are overriden by [^1]
337 // * Features implied by --target; are overriden by
338 // * Features from -Ctarget-feature; are overriden by
339 // * function specific features.
341 // [^1]: target-cpu=native is handled here, other target-cpu values are handled implicitly
342 // through LLVM TargetMachine implementation.
344 // FIXME(nagisa): it isn't clear what's the best interaction between features implied by
345 // `-Ctarget-cpu` and `--target` are. On one hand, you'd expect CLI arguments to always
346 // override anything that's implicit, so e.g. when there's no `--target` flag, features implied
347 // the host target are overriden by `-Ctarget-cpu=*`. On the other hand, what about when both
348 // `--target` and `-Ctarget-cpu=*` are specified? Both then imply some target features and both
349 // flags are specified by the user on the CLI. It isn't as clear-cut which order of precedence
350 // should be taken in cases like these.
351 let mut features = vec![];
353 // -Ctarget-cpu=native
354 match sess.opts.cg.target_cpu {
355 Some(ref s) if s == "native" => {
356 let features_string = unsafe {
357 let ptr = llvm::LLVMGetHostCPUFeatures();
358 let features_string = if !ptr.is_null() {
361 .unwrap_or_else(|e| {
362 bug!("LLVM returned a non-utf8 features string: {}", e);
366 bug!("could not allocate host CPU features, LLVM returned a `null` string");
369 llvm::LLVMDisposeMessage(ptr);
373 features.extend(features_string.split(',').map(String::from));
378 let filter = |s: &str| {
382 let feature = if s.starts_with('+') || s.starts_with('-') {
385 return vec![s.to_string()];
387 // Rustc-specific feature requests like `+crt-static` or `-crt-static`
388 // are not passed down to LLVM.
389 if RUSTC_SPECIFIC_FEATURES.contains(&feature) {
392 // ... otherwise though we run through `to_llvm_feature` feature when
393 // passing requests down to LLVM. This means that all in-language
394 // features also work on the command line instead of having two
395 // different names when the LLVM name and the Rust name differ.
396 to_llvm_feature(sess, feature).iter().map(|f| format!("{}{}", &s[..1], f)).collect()
399 // Features implied by an implicit or explicit `--target`.
400 features.extend(sess.target.features.split(',').flat_map(&filter));
403 features.extend(sess.opts.cg.target_feature.split(',').flat_map(&filter));
408 pub fn tune_cpu(sess: &Session) -> Option<&str> {
409 let name = sess.opts.debugging_opts.tune_cpu.as_ref()?;
410 Some(handle_native(name))