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;
7 use rustc_session::config::PrintRequest;
8 use rustc_session::Session;
9 use rustc_span::symbol::Symbol;
10 use rustc_target::spec::{MergeFunctions, PanicStrategy};
11 use std::ffi::{CStr, CString};
16 use std::sync::atomic::{AtomicBool, Ordering};
19 static POISONED: AtomicBool = AtomicBool::new(false);
20 static INIT: Once = Once::new();
22 pub(crate) fn init(sess: &Session) {
24 // Before we touch LLVM, make sure that multithreading is enabled.
26 if llvm::LLVMStartMultithreaded() != 1 {
27 // use an extra bool to make sure that all future usage of LLVM
28 // cannot proceed despite the Once not running more than once.
29 POISONED.store(true, Ordering::SeqCst);
35 if POISONED.load(Ordering::SeqCst) {
36 bug!("couldn't enable multi-threaded LLVM");
42 INIT.call_once(|| bug!("llvm is not initialized"));
43 if POISONED.load(Ordering::SeqCst) {
44 bug!("couldn't enable multi-threaded LLVM");
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();
55 fn llvm_arg_to_arg_name(full_arg: &str) -> &str {
56 full_arg.trim().split(|c: char| c == '=' || c.is_whitespace()).next().unwrap_or("")
59 let cg_opts = sess.opts.cg.llvm_args.iter();
60 let tg_opts = sess.target.llvm_args.iter();
61 let sess_args = cg_opts.chain(tg_opts);
63 let user_specified_args: FxHashSet<_> =
64 sess_args.clone().map(|s| llvm_arg_to_arg_name(s)).filter(|s| !s.is_empty()).collect();
67 // This adds the given argument to LLVM. Unless `force` is true
68 // user specified arguments are *not* overridden.
69 let mut add = |arg: &str, force: bool| {
70 if force || !user_specified_args.contains(llvm_arg_to_arg_name(arg)) {
71 let s = CString::new(arg).unwrap();
72 llvm_args.push(s.as_ptr());
76 // Set the llvm "program name" to make usage and invalid argument messages more clear.
77 add("rustc -Cllvm-args=\"...\" with", true);
78 if sess.time_llvm_passes() {
79 add("-time-passes", false);
81 if sess.print_llvm_passes() {
82 add("-debug-pass=Structure", false);
84 if !sess.opts.debugging_opts.no_generate_arange_section {
85 add("-generate-arange-section", false);
88 // FIXME(nagisa): disable the machine outliner by default in LLVM versions 11, where it was
91 // This should remain in place until https://reviews.llvm.org/D103167 is fixed. If LLVM
92 // has been upgraded since, consider adjusting the version check below to contain an upper
94 if llvm_util::get_version() >= (11, 0, 0) {
95 add("-enable-machine-outliner=never", false);
98 match sess.opts.debugging_opts.merge_functions.unwrap_or(sess.target.merge_functions) {
99 MergeFunctions::Disabled | MergeFunctions::Trampolines => {}
100 MergeFunctions::Aliases => {
101 add("-mergefunc-use-aliases", false);
105 if sess.target.os == "emscripten" && sess.panic_strategy() == PanicStrategy::Unwind {
106 add("-enable-emscripten-cxx-exceptions", false);
109 // HACK(eddyb) LLVM inserts `llvm.assume` calls to preserve align attributes
110 // during inlining. Unfortunately these may block other optimizations.
111 add("-preserve-alignment-assumptions-during-inlining=false", false);
113 // Use non-zero `import-instr-limit` multiplier for cold callsites.
114 add("-import-cold-multiplier=0.1", false);
116 for arg in sess_args {
121 if sess.opts.debugging_opts.llvm_time_trace {
122 // time-trace is not thread safe and running it in parallel will cause seg faults.
123 if !sess.opts.debugging_opts.no_parallel_llvm {
124 bug!("`-Z llvm-time-trace` requires `-Z no-parallel-llvm")
127 llvm::LLVMTimeTraceProfilerInitialize();
130 llvm::LLVMInitializePasses();
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) -> &'a str {
155 let arch = if sess.target.arch == "x86_64" { "x86" } else { &*sess.target.arch };
157 ("x86", "pclmulqdq") => "pclmul",
158 ("x86", "rdrand") => "rdrnd",
159 ("x86", "bmi1") => "bmi",
160 ("x86", "cmpxchg16b") => "cx16",
161 ("x86", "avx512vaes") => "vaes",
162 ("x86", "avx512gfni") => "gfni",
163 ("x86", "avx512vpclmulqdq") => "vpclmulqdq",
164 ("aarch64", "fp") => "fp-armv8",
165 ("aarch64", "fp16") => "fullfp16",
166 ("aarch64", "fhm") => "fp16fml",
167 ("aarch64", "rcpc2") => "rcpc-immo",
168 ("aarch64", "dpb") => "ccpp",
169 ("aarch64", "dpb2") => "ccdp",
170 ("aarch64", "frintts") => "fptoint",
171 ("aarch64", "fcma") => "complxnum",
176 pub fn target_features(sess: &Session) -> Vec<Symbol> {
177 let target_machine = create_informational_target_machine(sess);
178 supported_target_features(sess)
182 if sess.is_nightly_build() || gate.is_none() { Some(feature) } else { None }
186 let llvm_feature = to_llvm_feature(sess, feature);
187 let cstr = CString::new(llvm_feature).unwrap();
188 unsafe { llvm::LLVMRustHasFeature(target_machine, cstr.as_ptr()) }
190 .map(|feature| Symbol::intern(feature))
194 pub fn print_version() {
195 let (major, minor, patch) = get_version();
196 println!("LLVM version: {}.{}.{}", major, minor, patch);
199 pub fn get_version() -> (u32, u32, u32) {
200 // Can be called without initializing LLVM
202 (llvm::LLVMRustVersionMajor(), llvm::LLVMRustVersionMinor(), llvm::LLVMRustVersionPatch())
206 pub fn print_passes() {
207 // Can be called without initializing LLVM
209 llvm::LLVMRustPrintPasses();
213 fn llvm_target_features(tm: &llvm::TargetMachine) -> Vec<(&str, &str)> {
214 let len = unsafe { llvm::LLVMRustGetTargetFeaturesCount(tm) };
215 let mut ret = Vec::with_capacity(len);
218 let mut feature = ptr::null();
219 let mut desc = ptr::null();
220 llvm::LLVMRustGetTargetFeature(tm, i, &mut feature, &mut desc);
221 if feature.is_null() || desc.is_null() {
222 bug!("LLVM returned a `null` target feature string");
224 let feature = CStr::from_ptr(feature).to_str().unwrap_or_else(|e| {
225 bug!("LLVM returned a non-utf8 feature string: {}", e);
227 let desc = CStr::from_ptr(desc).to_str().unwrap_or_else(|e| {
228 bug!("LLVM returned a non-utf8 feature string: {}", e);
230 ret.push((feature, desc));
236 fn print_target_features(sess: &Session, tm: &llvm::TargetMachine) {
237 let mut target_features = llvm_target_features(tm);
238 let mut rustc_target_features = supported_target_features(sess)
240 .filter_map(|(feature, _gate)| {
241 let llvm_feature = to_llvm_feature(sess, *feature);
242 // LLVM asserts that these are sorted. LLVM and Rust both use byte comparison for these strings.
243 target_features.binary_search_by_key(&llvm_feature, |(f, _d)| *f).ok().map(|index| {
244 let (_f, desc) = target_features.remove(index);
248 .collect::<Vec<_>>();
249 rustc_target_features.extend_from_slice(&[(
251 "Enables C Run-time Libraries to be statically linked",
253 let max_feature_len = target_features
255 .chain(rustc_target_features.iter())
256 .map(|(feature, _desc)| feature.len())
260 println!("Features supported by rustc for this target:");
261 for (feature, desc) in &rustc_target_features {
262 println!(" {1:0$} - {2}.", max_feature_len, feature, desc);
264 println!("\nCode-generation features supported by LLVM for this target:");
265 for (feature, desc) in &target_features {
266 println!(" {1:0$} - {2}.", max_feature_len, feature, desc);
268 if target_features.len() == 0 {
269 println!(" Target features listing is not supported by this LLVM version.");
271 println!("\nUse +feature to enable a feature, or -feature to disable it.");
272 println!("For example, rustc -C target-cpu=mycpu -C target-feature=+feature1,-feature2\n");
273 println!("Code-generation features cannot be used in cfg or #[target_feature],");
274 println!("and may be renamed or removed in a future version of LLVM or rustc.\n");
277 pub(crate) fn print(req: PrintRequest, sess: &Session) {
279 let tm = create_informational_target_machine(sess);
281 PrintRequest::TargetCPUs => unsafe { llvm::LLVMRustPrintTargetCPUs(tm) },
282 PrintRequest::TargetFeatures => print_target_features(sess, tm),
283 _ => bug!("rustc_codegen_llvm can't handle print request: {:?}", req),
287 fn handle_native(name: &str) -> &str {
288 if name != "native" {
294 let ptr = llvm::LLVMRustGetHostCPUName(&mut len);
295 str::from_utf8(slice::from_raw_parts(ptr as *const u8, len)).unwrap()
299 pub fn target_cpu(sess: &Session) -> &str {
300 let name = sess.opts.cg.target_cpu.as_ref().unwrap_or(&sess.target.cpu);
304 /// The list of LLVM features computed from CLI flags (`-Ctarget-cpu`, `-Ctarget-feature`,
305 /// `--target` and similar).
306 // FIXME(nagisa): Cache the output of this somehow? Maybe make this a query? We're calling this
307 // for every function that has `#[target_feature]` on it. The global features won't change between
308 // the functions; only crates, maybe…
309 pub fn llvm_global_features(sess: &Session) -> Vec<String> {
310 // FIXME(nagisa): this should definitely be available more centrally and to other codegen backends.
311 /// These features control behaviour of rustc rather than llvm.
312 const RUSTC_SPECIFIC_FEATURES: &[&str] = &["crt-static"];
314 // Features that come earlier are overriden by conflicting features later in the string.
315 // Typically we'll want more explicit settings to override the implicit ones, so:
317 // * Features from -Ctarget-cpu=*; are overriden by [^1]
318 // * Features implied by --target; are overriden by
319 // * Features from -Ctarget-feature; are overriden by
320 // * function specific features.
322 // [^1]: target-cpu=native is handled here, other target-cpu values are handled implicitly
323 // through LLVM TargetMachine implementation.
325 // FIXME(nagisa): it isn't clear what's the best interaction between features implied by
326 // `-Ctarget-cpu` and `--target` are. On one hand, you'd expect CLI arguments to always
327 // override anything that's implicit, so e.g. when there's no `--target` flag, features implied
328 // the host target are overriden by `-Ctarget-cpu=*`. On the other hand, what about when both
329 // `--target` and `-Ctarget-cpu=*` are specified? Both then imply some target features and both
330 // flags are specified by the user on the CLI. It isn't as clear-cut which order of precedence
331 // should be taken in cases like these.
332 let mut features = vec![];
334 // -Ctarget-cpu=native
335 match sess.opts.cg.target_cpu {
336 Some(ref s) if s == "native" => {
337 let features_string = unsafe {
338 let ptr = llvm::LLVMGetHostCPUFeatures();
339 let features_string = if !ptr.is_null() {
342 .unwrap_or_else(|e| {
343 bug!("LLVM returned a non-utf8 features string: {}", e);
347 bug!("could not allocate host CPU features, LLVM returned a `null` string");
350 llvm::LLVMDisposeMessage(ptr);
354 features.extend(features_string.split(",").map(String::from));
359 let filter = |s: &str| {
363 let feature = if s.starts_with("+") || s.starts_with("-") {
366 return Some(s.to_string());
368 // Rustc-specific feature requests like `+crt-static` or `-crt-static`
369 // are not passed down to LLVM.
370 if RUSTC_SPECIFIC_FEATURES.contains(&feature) {
373 // ... otherwise though we run through `to_llvm_feature` feature when
374 // passing requests down to LLVM. This means that all in-language
375 // features also work on the command line instead of having two
376 // different names when the LLVM name and the Rust name differ.
377 Some(format!("{}{}", &s[..1], to_llvm_feature(sess, feature)))
380 // Features implied by an implicit or explicit `--target`.
381 features.extend(sess.target.features.split(',').filter_map(&filter));
384 features.extend(sess.opts.cg.target_feature.split(',').filter_map(&filter));
389 pub fn tune_cpu(sess: &Session) -> Option<&str> {
390 let name = sess.opts.debugging_opts.tune_cpu.as_ref()?;
391 Some(handle_native(name))