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 let llvm_version = llvm_util::get_version();
99 if llvm_version >= (11, 0, 0) && llvm_version < (13, 0, 0) {
100 add("-enable-machine-outliner=never", false);
103 match sess.opts.debugging_opts.merge_functions.unwrap_or(sess.target.merge_functions) {
104 MergeFunctions::Disabled | MergeFunctions::Trampolines => {}
105 MergeFunctions::Aliases => {
106 add("-mergefunc-use-aliases", false);
110 if sess.target.os == "emscripten" && sess.panic_strategy() == PanicStrategy::Unwind {
111 add("-enable-emscripten-cxx-exceptions", false);
114 // HACK(eddyb) LLVM inserts `llvm.assume` calls to preserve align attributes
115 // during inlining. Unfortunately these may block other optimizations.
116 add("-preserve-alignment-assumptions-during-inlining=false", false);
118 // Use non-zero `import-instr-limit` multiplier for cold callsites.
119 add("-import-cold-multiplier=0.1", false);
121 for arg in sess_args {
126 if sess.opts.debugging_opts.llvm_time_trace {
127 // time-trace is not thread safe and running it in parallel will cause seg faults.
128 if !sess.opts.debugging_opts.no_parallel_llvm {
129 bug!("`-Z llvm-time-trace` requires `-Z no-parallel-llvm")
132 llvm::LLVMTimeTraceProfilerInitialize();
135 llvm::LLVMInitializePasses();
137 for plugin in &sess.opts.debugging_opts.llvm_plugins {
138 let path = Path::new(plugin);
139 let res = DynamicLibrary::open(path);
141 Ok(_) => debug!("LLVM plugin loaded succesfully {} ({})", path.display(), plugin),
142 Err(e) => bug!("couldn't load plugin: {}", e),
147 rustc_llvm::initialize_available_targets();
149 llvm::LLVMRustSetLLVMOptions(llvm_args.len() as c_int, llvm_args.as_ptr());
152 pub fn time_trace_profiler_finish(file_name: &str) {
154 let file_name = CString::new(file_name).unwrap();
155 llvm::LLVMTimeTraceProfilerFinish(file_name.as_ptr());
159 // WARNING: the features after applying `to_llvm_feature` must be known
160 // to LLVM or the feature detection code will walk past the end of the feature
161 // array, leading to crashes.
162 // To find a list of LLVM's names, check llvm-project/llvm/include/llvm/Support/*TargetParser.def
163 // where the * matches the architecture's name
164 // Beware to not use the llvm github project for this, but check the git submodule
165 // found in src/llvm-project
166 // Though note that Rust can also be build with an external precompiled version of LLVM
167 // which might lead to failures if the oldest tested / supported LLVM version
168 // doesn't yet support the relevant intrinsics
169 pub fn to_llvm_feature<'a>(sess: &Session, s: &'a str) -> Vec<&'a str> {
170 let arch = if sess.target.arch == "x86_64" { "x86" } else { &*sess.target.arch };
172 ("x86", "sse4.2") => {
173 if get_version() >= (14, 0, 0) {
174 vec!["sse4.2", "crc32"]
179 ("x86", "pclmulqdq") => vec!["pclmul"],
180 ("x86", "rdrand") => vec!["rdrnd"],
181 ("x86", "bmi1") => vec!["bmi"],
182 ("x86", "cmpxchg16b") => vec!["cx16"],
183 ("x86", "avx512vaes") => vec!["vaes"],
184 ("x86", "avx512gfni") => vec!["gfni"],
185 ("x86", "avx512vpclmulqdq") => vec!["vpclmulqdq"],
186 ("aarch64", "fp") => vec!["fp-armv8"],
187 ("aarch64", "fp16") => vec!["fullfp16"],
188 ("aarch64", "fhm") => vec!["fp16fml"],
189 ("aarch64", "rcpc2") => vec!["rcpc-immo"],
190 ("aarch64", "dpb") => vec!["ccpp"],
191 ("aarch64", "dpb2") => vec!["ccdp"],
192 ("aarch64", "frintts") => vec!["fptoint"],
193 ("aarch64", "fcma") => vec!["complxnum"],
198 pub fn target_features(sess: &Session) -> Vec<Symbol> {
199 let target_machine = create_informational_target_machine(sess);
200 supported_target_features(sess)
204 if sess.is_nightly_build() || gate.is_none() { Some(feature) } else { None }
208 for llvm_feature in to_llvm_feature(sess, feature) {
209 let cstr = CString::new(llvm_feature).unwrap();
210 if unsafe { llvm::LLVMRustHasFeature(target_machine, cstr.as_ptr()) } {
216 .map(|feature| Symbol::intern(feature))
220 pub fn print_version() {
221 let (major, minor, patch) = get_version();
222 println!("LLVM version: {}.{}.{}", major, minor, patch);
225 pub fn get_version() -> (u32, u32, u32) {
226 // Can be called without initializing LLVM
228 (llvm::LLVMRustVersionMajor(), llvm::LLVMRustVersionMinor(), llvm::LLVMRustVersionPatch())
232 pub fn print_passes() {
233 // Can be called without initializing LLVM
235 llvm::LLVMRustPrintPasses();
239 fn llvm_target_features(tm: &llvm::TargetMachine) -> Vec<(&str, &str)> {
240 let len = unsafe { llvm::LLVMRustGetTargetFeaturesCount(tm) };
241 let mut ret = Vec::with_capacity(len);
244 let mut feature = ptr::null();
245 let mut desc = ptr::null();
246 llvm::LLVMRustGetTargetFeature(tm, i, &mut feature, &mut desc);
247 if feature.is_null() || desc.is_null() {
248 bug!("LLVM returned a `null` target feature string");
250 let feature = CStr::from_ptr(feature).to_str().unwrap_or_else(|e| {
251 bug!("LLVM returned a non-utf8 feature string: {}", e);
253 let desc = CStr::from_ptr(desc).to_str().unwrap_or_else(|e| {
254 bug!("LLVM returned a non-utf8 feature string: {}", e);
256 ret.push((feature, desc));
262 fn print_target_features(sess: &Session, tm: &llvm::TargetMachine) {
263 let mut target_features = llvm_target_features(tm);
264 let mut rustc_target_features = supported_target_features(sess)
266 .filter_map(|(feature, _gate)| {
267 for llvm_feature in to_llvm_feature(sess, *feature) {
268 // LLVM asserts that these are sorted. LLVM and Rust both use byte comparison for these strings.
269 match target_features.binary_search_by_key(&llvm_feature, |(f, _d)| (*f)).ok().map(
271 let (_f, desc) = target_features.remove(index);
275 Some(v) => return Some(v),
281 .collect::<Vec<_>>();
282 rustc_target_features.extend_from_slice(&[(
284 "Enables C Run-time Libraries to be statically linked",
286 let max_feature_len = target_features
288 .chain(rustc_target_features.iter())
289 .map(|(feature, _desc)| feature.len())
293 println!("Features supported by rustc for this target:");
294 for (feature, desc) in &rustc_target_features {
295 println!(" {1:0$} - {2}.", max_feature_len, feature, desc);
297 println!("\nCode-generation features supported by LLVM for this target:");
298 for (feature, desc) in &target_features {
299 println!(" {1:0$} - {2}.", max_feature_len, feature, desc);
301 if target_features.len() == 0 {
302 println!(" Target features listing is not supported by this LLVM version.");
304 println!("\nUse +feature to enable a feature, or -feature to disable it.");
305 println!("For example, rustc -C target-cpu=mycpu -C target-feature=+feature1,-feature2\n");
306 println!("Code-generation features cannot be used in cfg or #[target_feature],");
307 println!("and may be renamed or removed in a future version of LLVM or rustc.\n");
310 pub(crate) fn print(req: PrintRequest, sess: &Session) {
312 let tm = create_informational_target_machine(sess);
314 PrintRequest::TargetCPUs => unsafe { llvm::LLVMRustPrintTargetCPUs(tm) },
315 PrintRequest::TargetFeatures => print_target_features(sess, tm),
316 _ => bug!("rustc_codegen_llvm can't handle print request: {:?}", req),
320 fn handle_native(name: &str) -> &str {
321 if name != "native" {
327 let ptr = llvm::LLVMRustGetHostCPUName(&mut len);
328 str::from_utf8(slice::from_raw_parts(ptr as *const u8, len)).unwrap()
332 pub fn target_cpu(sess: &Session) -> &str {
333 let name = sess.opts.cg.target_cpu.as_ref().unwrap_or(&sess.target.cpu);
337 /// The list of LLVM features computed from CLI flags (`-Ctarget-cpu`, `-Ctarget-feature`,
338 /// `--target` and similar).
339 // FIXME(nagisa): Cache the output of this somehow? Maybe make this a query? We're calling this
340 // for every function that has `#[target_feature]` on it. The global features won't change between
341 // the functions; only crates, maybe…
342 pub fn llvm_global_features(sess: &Session) -> Vec<String> {
343 // FIXME(nagisa): this should definitely be available more centrally and to other codegen backends.
344 /// These features control behaviour of rustc rather than llvm.
345 const RUSTC_SPECIFIC_FEATURES: &[&str] = &["crt-static"];
347 // Features that come earlier are overriden by conflicting features later in the string.
348 // Typically we'll want more explicit settings to override the implicit ones, so:
350 // * Features from -Ctarget-cpu=*; are overriden by [^1]
351 // * Features implied by --target; are overriden by
352 // * Features from -Ctarget-feature; are overriden by
353 // * function specific features.
355 // [^1]: target-cpu=native is handled here, other target-cpu values are handled implicitly
356 // through LLVM TargetMachine implementation.
358 // FIXME(nagisa): it isn't clear what's the best interaction between features implied by
359 // `-Ctarget-cpu` and `--target` are. On one hand, you'd expect CLI arguments to always
360 // override anything that's implicit, so e.g. when there's no `--target` flag, features implied
361 // the host target are overriden by `-Ctarget-cpu=*`. On the other hand, what about when both
362 // `--target` and `-Ctarget-cpu=*` are specified? Both then imply some target features and both
363 // flags are specified by the user on the CLI. It isn't as clear-cut which order of precedence
364 // should be taken in cases like these.
365 let mut features = vec![];
367 // -Ctarget-cpu=native
368 match sess.opts.cg.target_cpu {
369 Some(ref s) if s == "native" => {
370 let features_string = unsafe {
371 let ptr = llvm::LLVMGetHostCPUFeatures();
372 let features_string = if !ptr.is_null() {
375 .unwrap_or_else(|e| {
376 bug!("LLVM returned a non-utf8 features string: {}", e);
380 bug!("could not allocate host CPU features, LLVM returned a `null` string");
383 llvm::LLVMDisposeMessage(ptr);
387 features.extend(features_string.split(',').map(String::from));
392 let filter = |s: &str| {
396 let feature = if s.starts_with('+') || s.starts_with('-') {
399 return vec![s.to_string()];
401 // Rustc-specific feature requests like `+crt-static` or `-crt-static`
402 // are not passed down to LLVM.
403 if RUSTC_SPECIFIC_FEATURES.contains(&feature) {
406 // ... otherwise though we run through `to_llvm_feature` feature when
407 // passing requests down to LLVM. This means that all in-language
408 // features also work on the command line instead of having two
409 // different names when the LLVM name and the Rust name differ.
410 to_llvm_feature(sess, feature).iter().map(|f| format!("{}{}", &s[..1], f)).collect()
413 // Features implied by an implicit or explicit `--target`.
414 features.extend(sess.target.features.split(',').flat_map(&filter));
417 features.extend(sess.opts.cg.target_feature.split(',').flat_map(&filter));
422 pub fn tune_cpu(sess: &Session) -> Option<&str> {
423 let name = sess.opts.debugging_opts.tune_cpu.as_ref()?;
424 Some(handle_native(name))