use crate::back::write::create_informational_target_machine; use crate::{llvm, llvm_util}; use libc::c_int; use libloading::Library; use rustc_codegen_ssa::target_features::{ supported_target_features, tied_target_features, RUSTC_SPECIFIC_FEATURES, }; use rustc_data_structures::fx::{FxHashMap, FxHashSet}; use rustc_data_structures::small_c_str::SmallCStr; use rustc_fs_util::path_to_c_string; use rustc_middle::bug; use rustc_session::config::PrintRequest; use rustc_session::Session; use rustc_span::symbol::Symbol; use rustc_target::spec::{MergeFunctions, PanicStrategy}; use smallvec::{smallvec, SmallVec}; use std::ffi::{CStr, CString}; use std::mem; use std::path::Path; use std::ptr; use std::slice; use std::str; use std::sync::Once; static INIT: Once = Once::new(); pub(crate) fn init(sess: &Session) { unsafe { // Before we touch LLVM, make sure that multithreading is enabled. if llvm::LLVMIsMultithreaded() != 1 { bug!("LLVM compiled without support for threads"); } INIT.call_once(|| { configure_llvm(sess); }); } } fn require_inited() { if !INIT.is_completed() { bug!("LLVM is not initialized"); } } unsafe fn configure_llvm(sess: &Session) { let n_args = sess.opts.cg.llvm_args.len() + sess.target.llvm_args.len(); let mut llvm_c_strs = Vec::with_capacity(n_args + 1); let mut llvm_args = Vec::with_capacity(n_args + 1); llvm::LLVMRustInstallFatalErrorHandler(); // On Windows, an LLVM assertion will open an Abort/Retry/Ignore dialog // box for the purpose of launching a debugger. However, on CI this will // cause it to hang until it times out, which can take several hours. if std::env::var_os("CI").is_some() { llvm::LLVMRustDisableSystemDialogsOnCrash(); } fn llvm_arg_to_arg_name(full_arg: &str) -> &str { full_arg.trim().split(|c: char| c == '=' || c.is_whitespace()).next().unwrap_or("") } let cg_opts = sess.opts.cg.llvm_args.iter().map(AsRef::as_ref); let tg_opts = sess.target.llvm_args.iter().map(AsRef::as_ref); let sess_args = cg_opts.chain(tg_opts); let user_specified_args: FxHashSet<_> = sess_args.clone().map(|s| llvm_arg_to_arg_name(s)).filter(|s| !s.is_empty()).collect(); { // This adds the given argument to LLVM. Unless `force` is true // user specified arguments are *not* overridden. let mut add = |arg: &str, force: bool| { if force || !user_specified_args.contains(llvm_arg_to_arg_name(arg)) { let s = CString::new(arg).unwrap(); llvm_args.push(s.as_ptr()); llvm_c_strs.push(s); } }; // Set the llvm "program name" to make usage and invalid argument messages more clear. add("rustc -Cllvm-args=\"...\" with", true); if sess.time_llvm_passes() { add("-time-passes", false); } if sess.print_llvm_passes() { add("-debug-pass=Structure", false); } if sess.target.generate_arange_section && !sess.opts.unstable_opts.no_generate_arange_section { add("-generate-arange-section", false); } match sess.opts.unstable_opts.merge_functions.unwrap_or(sess.target.merge_functions) { MergeFunctions::Disabled | MergeFunctions::Trampolines => {} MergeFunctions::Aliases => { add("-mergefunc-use-aliases", false); } } if sess.target.os == "emscripten" && sess.panic_strategy() == PanicStrategy::Unwind { add("-enable-emscripten-cxx-exceptions", false); } // HACK(eddyb) LLVM inserts `llvm.assume` calls to preserve align attributes // during inlining. Unfortunately these may block other optimizations. add("-preserve-alignment-assumptions-during-inlining=false", false); // Use non-zero `import-instr-limit` multiplier for cold callsites. add("-import-cold-multiplier=0.1", false); for arg in sess_args { add(&(*arg), true); } } if sess.opts.unstable_opts.llvm_time_trace { llvm::LLVMTimeTraceProfilerInitialize(); } llvm::LLVMInitializePasses(); // Use the legacy plugin registration if we don't use the new pass manager if !should_use_new_llvm_pass_manager( &sess.opts.unstable_opts.new_llvm_pass_manager, &sess.target.arch, ) { // Register LLVM plugins by loading them into the compiler process. for plugin in &sess.opts.unstable_opts.llvm_plugins { let lib = Library::new(plugin).unwrap_or_else(|e| bug!("couldn't load plugin: {}", e)); debug!("LLVM plugin loaded successfully {:?} ({})", lib, plugin); // Intentionally leak the dynamic library. We can't ever unload it // since the library can make things that will live arbitrarily long. mem::forget(lib); } } rustc_llvm::initialize_available_targets(); llvm::LLVMRustSetLLVMOptions(llvm_args.len() as c_int, llvm_args.as_ptr()); } pub fn time_trace_profiler_finish(file_name: &Path) { unsafe { let file_name = path_to_c_string(file_name); llvm::LLVMTimeTraceProfilerFinish(file_name.as_ptr()); } } // WARNING: the features after applying `to_llvm_features` must be known // to LLVM or the feature detection code will walk past the end of the feature // array, leading to crashes. // // To find a list of LLVM's names, check llvm-project/llvm/include/llvm/Support/*TargetParser.def // where the * matches the architecture's name // // For targets not present in the above location, see llvm-project/llvm/lib/Target/{ARCH}/*.td // where `{ARCH}` is the architecture name. Look for instances of `SubtargetFeature`. // // Beware to not use the llvm github project for this, but check the git submodule // found in src/llvm-project // Though note that Rust can also be build with an external precompiled version of LLVM // which might lead to failures if the oldest tested / supported LLVM version // doesn't yet support the relevant intrinsics pub fn to_llvm_features<'a>(sess: &Session, s: &'a str) -> SmallVec<[&'a str; 2]> { let arch = if sess.target.arch == "x86_64" { "x86" } else { &*sess.target.arch }; match (arch, s) { ("x86", "sse4.2") => { if get_version() >= (14, 0, 0) { smallvec!["sse4.2", "crc32"] } else { smallvec!["sse4.2"] } } ("x86", "pclmulqdq") => smallvec!["pclmul"], ("x86", "rdrand") => smallvec!["rdrnd"], ("x86", "bmi1") => smallvec!["bmi"], ("x86", "cmpxchg16b") => smallvec!["cx16"], ("x86", "avx512vaes") => smallvec!["vaes"], ("x86", "avx512gfni") => smallvec!["gfni"], ("x86", "avx512vpclmulqdq") => smallvec!["vpclmulqdq"], ("aarch64", "rcpc2") => smallvec!["rcpc-immo"], ("aarch64", "dpb") => smallvec!["ccpp"], ("aarch64", "dpb2") => smallvec!["ccdp"], ("aarch64", "frintts") => smallvec!["fptoint"], ("aarch64", "fcma") => smallvec!["complxnum"], ("aarch64", "pmuv3") => smallvec!["perfmon"], ("aarch64", "paca") => smallvec!["pauth"], ("aarch64", "pacg") => smallvec!["pauth"], // Rust ties fp and neon together. In LLVM neon implicitly enables fp, // but we manually enable neon when a feature only implicitly enables fp ("aarch64", "f32mm") => smallvec!["f32mm", "neon"], ("aarch64", "f64mm") => smallvec!["f64mm", "neon"], ("aarch64", "fhm") => smallvec!["fp16fml", "neon"], ("aarch64", "fp16") => smallvec!["fullfp16", "neon"], ("aarch64", "jsconv") => smallvec!["jsconv", "neon"], ("aarch64", "sve") => smallvec!["sve", "neon"], ("aarch64", "sve2") => smallvec!["sve2", "neon"], ("aarch64", "sve2-aes") => smallvec!["sve2-aes", "neon"], ("aarch64", "sve2-sm4") => smallvec!["sve2-sm4", "neon"], ("aarch64", "sve2-sha3") => smallvec!["sve2-sha3", "neon"], ("aarch64", "sve2-bitperm") => smallvec!["sve2-bitperm", "neon"], (_, s) => smallvec![s], } } // Given a map from target_features to whether they are enabled or disabled, // ensure only valid combinations are allowed. pub fn check_tied_features( sess: &Session, features: &FxHashMap<&str, bool>, ) -> Option<&'static [&'static str]> { if !features.is_empty() { for tied in tied_target_features(sess) { // Tied features must be set to the same value, or not set at all let mut tied_iter = tied.iter(); let enabled = features.get(tied_iter.next().unwrap()); if tied_iter.any(|f| enabled != features.get(f)) { return Some(tied); } } } return None; } // Used to generate cfg variables and apply features // Must express features in the way Rust understands them pub fn target_features(sess: &Session, allow_unstable: bool) -> Vec { let target_machine = create_informational_target_machine(sess); let mut features: Vec = supported_target_features(sess) .iter() .filter_map(|&(feature, gate)| { if sess.is_nightly_build() || allow_unstable || gate.is_none() { Some(feature) } else { None } }) .filter(|feature| { // check that all features in a given smallvec are enabled for llvm_feature in to_llvm_features(sess, feature) { let cstr = SmallCStr::new(llvm_feature); if !unsafe { llvm::LLVMRustHasFeature(target_machine, cstr.as_ptr()) } { return false; } } true }) .map(|feature| Symbol::intern(feature)) .collect(); // LLVM 14 changed the ABI for i128 arguments to __float/__fix builtins on Win64 // (see https://reviews.llvm.org/D110413). This unstable target feature is intended for use // by compiler-builtins, to export the builtins with the expected, LLVM-version-dependent ABI. // The target feature can be dropped once we no longer support older LLVM versions. if sess.is_nightly_build() && get_version() >= (14, 0, 0) { features.push(Symbol::intern("llvm14-builtins-abi")); } features } pub fn print_version() { let (major, minor, patch) = get_version(); println!("LLVM version: {}.{}.{}", major, minor, patch); } pub fn get_version() -> (u32, u32, u32) { // Can be called without initializing LLVM unsafe { (llvm::LLVMRustVersionMajor(), llvm::LLVMRustVersionMinor(), llvm::LLVMRustVersionPatch()) } } pub fn print_passes() { // Can be called without initializing LLVM unsafe { llvm::LLVMRustPrintPasses(); } } fn llvm_target_features(tm: &llvm::TargetMachine) -> Vec<(&str, &str)> { let len = unsafe { llvm::LLVMRustGetTargetFeaturesCount(tm) }; let mut ret = Vec::with_capacity(len); for i in 0..len { unsafe { let mut feature = ptr::null(); let mut desc = ptr::null(); llvm::LLVMRustGetTargetFeature(tm, i, &mut feature, &mut desc); if feature.is_null() || desc.is_null() { bug!("LLVM returned a `null` target feature string"); } let feature = CStr::from_ptr(feature).to_str().unwrap_or_else(|e| { bug!("LLVM returned a non-utf8 feature string: {}", e); }); let desc = CStr::from_ptr(desc).to_str().unwrap_or_else(|e| { bug!("LLVM returned a non-utf8 feature string: {}", e); }); ret.push((feature, desc)); } } ret } fn print_target_features(sess: &Session, tm: &llvm::TargetMachine) { let mut target_features = llvm_target_features(tm); let mut rustc_target_features = supported_target_features(sess) .iter() .filter_map(|(feature, _gate)| { for llvm_feature in to_llvm_features(sess, *feature) { // LLVM asserts that these are sorted. LLVM and Rust both use byte comparison for these strings. match target_features.binary_search_by_key(&llvm_feature, |(f, _d)| f).ok().map( |index| { let (_f, desc) = target_features.remove(index); (*feature, desc) }, ) { Some(v) => return Some(v), None => {} } } None }) .collect::>(); rustc_target_features.extend_from_slice(&[( "crt-static", "Enables C Run-time Libraries to be statically linked", )]); let max_feature_len = target_features .iter() .chain(rustc_target_features.iter()) .map(|(feature, _desc)| feature.len()) .max() .unwrap_or(0); println!("Features supported by rustc for this target:"); for (feature, desc) in &rustc_target_features { println!(" {1:0$} - {2}.", max_feature_len, feature, desc); } println!("\nCode-generation features supported by LLVM for this target:"); for (feature, desc) in &target_features { println!(" {1:0$} - {2}.", max_feature_len, feature, desc); } if target_features.is_empty() { println!(" Target features listing is not supported by this LLVM version."); } println!("\nUse +feature to enable a feature, or -feature to disable it."); println!("For example, rustc -C target-cpu=mycpu -C target-feature=+feature1,-feature2\n"); println!("Code-generation features cannot be used in cfg or #[target_feature],"); println!("and may be renamed or removed in a future version of LLVM or rustc.\n"); } pub(crate) fn print(req: PrintRequest, sess: &Session) { require_inited(); let tm = create_informational_target_machine(sess); match req { PrintRequest::TargetCPUs => unsafe { llvm::LLVMRustPrintTargetCPUs(tm) }, PrintRequest::TargetFeatures => print_target_features(sess, tm), _ => bug!("rustc_codegen_llvm can't handle print request: {:?}", req), } } fn handle_native(name: &str) -> &str { if name != "native" { return name; } unsafe { let mut len = 0; let ptr = llvm::LLVMRustGetHostCPUName(&mut len); str::from_utf8(slice::from_raw_parts(ptr as *const u8, len)).unwrap() } } pub fn target_cpu(sess: &Session) -> &str { match sess.opts.cg.target_cpu { Some(ref name) => handle_native(name), None => handle_native(sess.target.cpu.as_ref()), } } /// The list of LLVM features computed from CLI flags (`-Ctarget-cpu`, `-Ctarget-feature`, /// `--target` and similar). pub(crate) fn global_llvm_features(sess: &Session, diagnostics: bool) -> Vec { // Features that come earlier are overridden by conflicting features later in the string. // Typically we'll want more explicit settings to override the implicit ones, so: // // * Features from -Ctarget-cpu=*; are overridden by [^1] // * Features implied by --target; are overridden by // * Features from -Ctarget-feature; are overridden by // * function specific features. // // [^1]: target-cpu=native is handled here, other target-cpu values are handled implicitly // through LLVM TargetMachine implementation. // // FIXME(nagisa): it isn't clear what's the best interaction between features implied by // `-Ctarget-cpu` and `--target` are. On one hand, you'd expect CLI arguments to always // override anything that's implicit, so e.g. when there's no `--target` flag, features implied // the host target are overridden by `-Ctarget-cpu=*`. On the other hand, what about when both // `--target` and `-Ctarget-cpu=*` are specified? Both then imply some target features and both // flags are specified by the user on the CLI. It isn't as clear-cut which order of precedence // should be taken in cases like these. let mut features = vec![]; // -Ctarget-cpu=native match sess.opts.cg.target_cpu { Some(ref s) if s == "native" => { let features_string = unsafe { let ptr = llvm::LLVMGetHostCPUFeatures(); let features_string = if !ptr.is_null() { CStr::from_ptr(ptr) .to_str() .unwrap_or_else(|e| { bug!("LLVM returned a non-utf8 features string: {}", e); }) .to_owned() } else { bug!("could not allocate host CPU features, LLVM returned a `null` string"); }; llvm::LLVMDisposeMessage(ptr); features_string }; features.extend(features_string.split(',').map(String::from)); } Some(_) | None => {} }; // Features implied by an implicit or explicit `--target`. features.extend( sess.target .features .split(',') .filter(|v| !v.is_empty() && backend_feature_name(v).is_some()) // Drop +atomics-32 feature introduced in LLVM 15. .filter(|v| *v != "+atomics-32" || get_version() >= (15, 0, 0)) .map(String::from), ); // -Ctarget-features let supported_features = supported_target_features(sess); let mut featsmap = FxHashMap::default(); let feats = sess .opts .cg .target_feature .split(',') .filter_map(|s| { let enable_disable = match s.chars().next() { None => return None, Some(c @ '+' | c @ '-') => c, Some(_) => { if diagnostics { let mut diag = sess.struct_warn(&format!( "unknown feature specified for `-Ctarget-feature`: `{}`", s )); diag.note("features must begin with a `+` to enable or `-` to disable it"); diag.emit(); } return None; } }; let feature = backend_feature_name(s)?; // Warn against use of LLVM specific feature names on the CLI. if diagnostics && !supported_features.iter().any(|&(v, _)| v == feature) { let rust_feature = supported_features.iter().find_map(|&(rust_feature, _)| { let llvm_features = to_llvm_features(sess, rust_feature); if llvm_features.contains(&feature) && !llvm_features.contains(&rust_feature) { Some(rust_feature) } else { None } }); let mut diag = sess.struct_warn(&format!( "unknown feature specified for `-Ctarget-feature`: `{}`", feature )); diag.note("it is still passed through to the codegen backend"); if let Some(rust_feature) = rust_feature { diag.help(&format!("you might have meant: `{}`", rust_feature)); } else { diag.note("consider filing a feature request"); } diag.emit(); } if diagnostics { // FIXME(nagisa): figure out how to not allocate a full hashset here. featsmap.insert(feature, enable_disable == '+'); } // rustc-specific features do not get passed down to LLVM… if RUSTC_SPECIFIC_FEATURES.contains(&feature) { return None; } // ... otherwise though we run through `to_llvm_features` when // passing requests down to LLVM. This means that all in-language // features also work on the command line instead of having two // different names when the LLVM name and the Rust name differ. Some( to_llvm_features(sess, feature) .into_iter() .map(move |f| format!("{}{}", enable_disable, f)), ) }) .flatten(); features.extend(feats); if diagnostics && let Some(f) = check_tied_features(sess, &featsmap) { sess.err(&format!( "target features {} must all be enabled or disabled together", f.join(", ") )); } features } /// Returns a feature name for the given `+feature` or `-feature` string. /// /// Only allows features that are backend specific (i.e. not [`RUSTC_SPECIFIC_FEATURES`].) fn backend_feature_name(s: &str) -> Option<&str> { // features must start with a `+` or `-`. let feature = s.strip_prefix(&['+', '-'][..]).unwrap_or_else(|| { bug!("target feature `{}` must begin with a `+` or `-`", s); }); // Rustc-specific feature requests like `+crt-static` or `-crt-static` // are not passed down to LLVM. if RUSTC_SPECIFIC_FEATURES.contains(&feature) { return None; } Some(feature) } pub fn tune_cpu(sess: &Session) -> Option<&str> { let name = sess.opts.unstable_opts.tune_cpu.as_ref()?; Some(handle_native(name)) } pub(crate) fn should_use_new_llvm_pass_manager(user_opt: &Option, target_arch: &str) -> bool { // The new pass manager is enabled by default for LLVM >= 13. // This matches Clang, which also enables it since Clang 13. // Since LLVM 15, the legacy pass manager is no longer supported. if llvm_util::get_version() >= (15, 0, 0) { return true; } // There are some perf issues with the new pass manager when targeting // s390x with LLVM 13, so enable the new pass manager only with LLVM 14. // See https://github.com/rust-lang/rust/issues/89609. let min_version = if target_arch == "s390x" { 14 } else { 13 }; user_opt.unwrap_or_else(|| llvm_util::get_version() >= (min_version, 0, 0)) }