| use crate::back::write::create_informational_target_machine; |
| use crate::errors::{ |
| PossibleFeature, TargetFeatureDisableOrEnable, UnknownCTargetFeature, |
| UnknownCTargetFeaturePrefix, |
| }; |
| use crate::llvm; |
| use libc::c_int; |
| 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 std::ffi::{CStr, CString}; |
| |
| 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.opts.unstable_opts.time_llvm_passes { |
| add("-time-passes", false); |
| } |
| if sess.opts.unstable_opts.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(); |
| } |
| |
| 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()); |
| } |
| } |
| |
| pub enum TargetFeatureFoldStrength<'a> { |
| // The feature is only tied when enabling the feature, disabling |
| // this feature shouldn't disable the tied feature. |
| EnableOnly(&'a str), |
| // The feature is tied for both enabling and disabling this feature. |
| Both(&'a str), |
| } |
| |
| impl<'a> TargetFeatureFoldStrength<'a> { |
| fn as_str(&self) -> &'a str { |
| match self { |
| TargetFeatureFoldStrength::EnableOnly(feat) => feat, |
| TargetFeatureFoldStrength::Both(feat) => feat, |
| } |
| } |
| } |
| |
| pub struct LLVMFeature<'a> { |
| pub llvm_feature_name: &'a str, |
| pub dependency: Option<TargetFeatureFoldStrength<'a>>, |
| } |
| |
| impl<'a> LLVMFeature<'a> { |
| pub fn new(llvm_feature_name: &'a str) -> Self { |
| Self { llvm_feature_name, dependency: None } |
| } |
| |
| pub fn with_dependency( |
| llvm_feature_name: &'a str, |
| dependency: TargetFeatureFoldStrength<'a>, |
| ) -> Self { |
| Self { llvm_feature_name, dependency: Some(dependency) } |
| } |
| |
| pub fn contains(&self, feat: &str) -> bool { |
| self.iter().any(|dep| dep == feat) |
| } |
| |
| pub fn iter(&'a self) -> impl Iterator<Item = &'a str> { |
| let dependencies = self.dependency.iter().map(|feat| feat.as_str()); |
| std::iter::once(self.llvm_feature_name).chain(dependencies) |
| } |
| } |
| |
| impl<'a> IntoIterator for LLVMFeature<'a> { |
| type Item = &'a str; |
| type IntoIter = impl Iterator<Item = &'a str>; |
| |
| fn into_iter(self) -> Self::IntoIter { |
| let dependencies = self.dependency.into_iter().map(|feat| feat.as_str()); |
| std::iter::once(self.llvm_feature_name).chain(dependencies) |
| } |
| } |
| |
| // 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) -> LLVMFeature<'a> { |
| let arch = if sess.target.arch == "x86_64" { "x86" } else { &*sess.target.arch }; |
| match (arch, s) { |
| ("x86", "sse4.2") => { |
| LLVMFeature::with_dependency("sse4.2", TargetFeatureFoldStrength::EnableOnly("crc32")) |
| } |
| ("x86", "pclmulqdq") => LLVMFeature::new("pclmul"), |
| ("x86", "rdrand") => LLVMFeature::new("rdrnd"), |
| ("x86", "bmi1") => LLVMFeature::new("bmi"), |
| ("x86", "cmpxchg16b") => LLVMFeature::new("cx16"), |
| ("aarch64", "rcpc2") => LLVMFeature::new("rcpc-immo"), |
| ("aarch64", "dpb") => LLVMFeature::new("ccpp"), |
| ("aarch64", "dpb2") => LLVMFeature::new("ccdp"), |
| ("aarch64", "frintts") => LLVMFeature::new("fptoint"), |
| ("aarch64", "fcma") => LLVMFeature::new("complxnum"), |
| ("aarch64", "pmuv3") => LLVMFeature::new("perfmon"), |
| ("aarch64", "paca") => LLVMFeature::new("pauth"), |
| ("aarch64", "pacg") => LLVMFeature::new("pauth"), |
| // Rust ties fp and neon together. |
| ("aarch64", "neon") => { |
| LLVMFeature::with_dependency("neon", TargetFeatureFoldStrength::Both("fp-armv8")) |
| } |
| // In LLVM neon implicitly enables fp, but we manually enable |
| // neon when a feature only implicitly enables fp |
| ("aarch64", "f32mm") => { |
| LLVMFeature::with_dependency("f32mm", TargetFeatureFoldStrength::EnableOnly("neon")) |
| } |
| ("aarch64", "f64mm") => { |
| LLVMFeature::with_dependency("f64mm", TargetFeatureFoldStrength::EnableOnly("neon")) |
| } |
| ("aarch64", "fhm") => { |
| LLVMFeature::with_dependency("fp16fml", TargetFeatureFoldStrength::EnableOnly("neon")) |
| } |
| ("aarch64", "fp16") => { |
| LLVMFeature::with_dependency("fullfp16", TargetFeatureFoldStrength::EnableOnly("neon")) |
| } |
| ("aarch64", "jsconv") => { |
| LLVMFeature::with_dependency("jsconv", TargetFeatureFoldStrength::EnableOnly("neon")) |
| } |
| ("aarch64", "sve") => { |
| LLVMFeature::with_dependency("sve", TargetFeatureFoldStrength::EnableOnly("neon")) |
| } |
| ("aarch64", "sve2") => { |
| LLVMFeature::with_dependency("sve2", TargetFeatureFoldStrength::EnableOnly("neon")) |
| } |
| ("aarch64", "sve2-aes") => { |
| LLVMFeature::with_dependency("sve2-aes", TargetFeatureFoldStrength::EnableOnly("neon")) |
| } |
| ("aarch64", "sve2-sm4") => { |
| LLVMFeature::with_dependency("sve2-sm4", TargetFeatureFoldStrength::EnableOnly("neon")) |
| } |
| ("aarch64", "sve2-sha3") => { |
| LLVMFeature::with_dependency("sve2-sha3", TargetFeatureFoldStrength::EnableOnly("neon")) |
| } |
| ("aarch64", "sve2-bitperm") => LLVMFeature::with_dependency( |
| "sve2-bitperm", |
| TargetFeatureFoldStrength::EnableOnly("neon"), |
| ), |
| (_, s) => LLVMFeature::new(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<Symbol> { |
| let target_machine = create_informational_target_machine(sess); |
| 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() |
| } |
| |
| 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 llvm_target_features = llvm_target_features(tm); |
| let mut known_llvm_target_features = FxHashSet::<&'static str>::default(); |
| let mut rustc_target_features = supported_target_features(sess) |
| .iter() |
| .map(|(feature, _gate)| { |
| // LLVM asserts that these are sorted. LLVM and Rust both use byte comparison for these strings. |
| let llvm_feature = to_llvm_features(sess, *feature).llvm_feature_name; |
| let desc = |
| match llvm_target_features.binary_search_by_key(&llvm_feature, |(f, _d)| f).ok() { |
| Some(index) => { |
| known_llvm_target_features.insert(llvm_feature); |
| llvm_target_features[index].1 |
| } |
| None => "", |
| }; |
| |
| (*feature, desc) |
| }) |
| .collect::<Vec<_>>(); |
| rustc_target_features.extend_from_slice(&[( |
| "crt-static", |
| "Enables C Run-time Libraries to be statically linked", |
| )]); |
| llvm_target_features.retain(|(f, _d)| !known_llvm_target_features.contains(f)); |
| |
| let max_feature_len = llvm_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$} - {2}.", max_feature_len, feature, desc); |
| } |
| println!("\nCode-generation features supported by LLVM for this target:"); |
| for (feature, desc) in &llvm_target_features { |
| println!(" {1:0$} - {2}.", max_feature_len, feature, desc); |
| } |
| if llvm_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 => { |
| // SAFETY generate a C compatible string from a byte slice to pass |
| // the target CPU name into LLVM, the lifetime of the reference is |
| // at least as long as the C function |
| let cpu_cstring = CString::new(handle_native(sess.target.cpu.as_ref())) |
| .unwrap_or_else(|e| bug!("failed to convert to cstring: {}", e)); |
| unsafe { llvm::LLVMRustPrintTargetCPUs(tm, cpu_cstring.as_ptr()) }; |
| } |
| 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<String> { |
| // 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, |
| Some(_) => { |
| if diagnostics { |
| sess.emit_warning(UnknownCTargetFeaturePrefix { feature: s }); |
| } |
| 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 unknown_feature = if let Some(rust_feature) = rust_feature { |
| UnknownCTargetFeature { |
| feature, |
| rust_feature: PossibleFeature::Some { rust_feature }, |
| } |
| } else { |
| UnknownCTargetFeature { feature, rust_feature: PossibleFeature::None } |
| }; |
| sess.emit_warning(unknown_feature); |
| } |
| |
| 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. |
| let llvm_feature = to_llvm_features(sess, feature); |
| |
| Some( |
| std::iter::once(format!("{}{}", enable_disable, llvm_feature.llvm_feature_name)) |
| .chain(llvm_feature.dependency.into_iter().filter_map(move |feat| { |
| match (enable_disable, feat) { |
| ('-' | '+', TargetFeatureFoldStrength::Both(f)) |
| | ('+', TargetFeatureFoldStrength::EnableOnly(f)) => { |
| Some(format!("{}{}", enable_disable, f)) |
| } |
| _ => None, |
| } |
| })), |
| ) |
| }) |
| .flatten(); |
| features.extend(feats); |
| |
| if diagnostics && let Some(f) = check_tied_features(sess, &featsmap) { |
| sess.emit_err(TargetFeatureDisableOrEnable { |
| features: f, |
| span: None, |
| missing_features: None, |
| }); |
| } |
| |
| 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)) |
| } |
