| use std::collections::VecDeque; |
| use std::ffi::{CStr, CString}; |
| use std::fmt::Write; |
| use std::path::Path; |
| use std::sync::Once; |
| use std::{ptr, slice, str}; |
| |
| use libc::c_int; |
| use rustc_codegen_ssa::base::wants_wasm_eh; |
| use rustc_codegen_ssa::target_features::cfg_target_feature; |
| use rustc_codegen_ssa::{TargetConfig, target_features}; |
| use rustc_data_structures::fx::FxHashSet; |
| use rustc_data_structures::small_c_str::SmallCStr; |
| use rustc_fs_util::path_to_c_string; |
| use rustc_middle::bug; |
| use rustc_session::Session; |
| use rustc_session::config::{PrintKind, PrintRequest}; |
| use rustc_target::spec::{MergeFunctions, PanicStrategy, SmallDataThresholdSupport}; |
| use smallvec::{SmallVec, smallvec}; |
| |
| use crate::back::write::create_informational_target_machine; |
| use crate::{errors, llvm}; |
| |
| 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); |
| |
| unsafe { |
| llvm::LLVMRustInstallErrorHandlers(); |
| } |
| // 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() { |
| unsafe { |
| 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 wants_wasm_eh(sess) { |
| add("-wasm-enable-eh", false); |
| } |
| |
| if sess.target.os == "emscripten" |
| && !sess.opts.unstable_opts.emscripten_wasm_eh |
| && 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); |
| |
| if sess.print_llvm_stats() { |
| add("-stats", false); |
| } |
| |
| for arg in sess_args { |
| add(&(*arg), true); |
| } |
| |
| match ( |
| sess.opts.unstable_opts.small_data_threshold, |
| sess.target.small_data_threshold_support(), |
| ) { |
| // Set up the small-data optimization limit for architectures that use |
| // an LLVM argument to control this. |
| (Some(threshold), SmallDataThresholdSupport::LlvmArg(arg)) => { |
| add(&format!("--{arg}={threshold}"), false) |
| } |
| _ => (), |
| }; |
| } |
| |
| if sess.opts.unstable_opts.llvm_time_trace { |
| unsafe { llvm::LLVMRustTimeTraceProfilerInitialize() }; |
| } |
| |
| rustc_llvm::initialize_available_targets(); |
| |
| unsafe { llvm::LLVMRustSetLLVMOptions(llvm_args.len() as c_int, llvm_args.as_ptr()) }; |
| } |
| |
| pub(crate) fn time_trace_profiler_finish(file_name: &Path) { |
| unsafe { |
| let file_name = path_to_c_string(file_name); |
| llvm::LLVMRustTimeTraceProfilerFinish(file_name.as_ptr()); |
| } |
| } |
| |
| 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(crate) struct LLVMFeature<'a> { |
| llvm_feature_name: &'a str, |
| dependencies: SmallVec<[TargetFeatureFoldStrength<'a>; 1]>, |
| } |
| |
| impl<'a> LLVMFeature<'a> { |
| fn new(llvm_feature_name: &'a str) -> Self { |
| Self { llvm_feature_name, dependencies: SmallVec::new() } |
| } |
| |
| fn with_dependencies( |
| llvm_feature_name: &'a str, |
| dependencies: SmallVec<[TargetFeatureFoldStrength<'a>; 1]>, |
| ) -> Self { |
| Self { llvm_feature_name, 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.dependencies.into_iter().map(|feat| feat.as_str()); |
| std::iter::once(self.llvm_feature_name).chain(dependencies) |
| } |
| } |
| |
| /// Convert a Rust feature name to an LLVM feature name. Returning `None` means the |
| /// feature should be skipped, usually because it is not supported by the current |
| /// LLVM version. |
| /// |
| /// 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, see llvm-project/llvm/lib/Target/{ARCH}/*.td |
| /// where `{ARCH}` is the architecture name. Look for instances of `SubtargetFeature`. |
| /// |
| /// Check the current rustc fork of LLVM in the repo at |
| /// <https://github.com/rust-lang/llvm-project/>. The commit in use can be found via the |
| /// `llvm-project` submodule in <https://github.com/rust-lang/rust/tree/master/src> 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(crate) fn to_llvm_features<'a>(sess: &Session, s: &'a str) -> Option<LLVMFeature<'a>> { |
| let arch = if sess.target.arch == "x86_64" { |
| "x86" |
| } else if sess.target.arch == "arm64ec" { |
| "aarch64" |
| } else if sess.target.arch == "sparc64" { |
| "sparc" |
| } else if sess.target.arch == "powerpc64" { |
| "powerpc" |
| } else { |
| &*sess.target.arch |
| }; |
| match (arch, s) { |
| ("x86", "sse4.2") => Some(LLVMFeature::with_dependencies( |
| "sse4.2", |
| smallvec![TargetFeatureFoldStrength::EnableOnly("crc32")], |
| )), |
| ("x86", "pclmulqdq") => Some(LLVMFeature::new("pclmul")), |
| ("x86", "rdrand") => Some(LLVMFeature::new("rdrnd")), |
| ("x86", "bmi1") => Some(LLVMFeature::new("bmi")), |
| ("x86", "cmpxchg16b") => Some(LLVMFeature::new("cx16")), |
| ("x86", "lahfsahf") => Some(LLVMFeature::new("sahf")), |
| ("aarch64", "rcpc2") => Some(LLVMFeature::new("rcpc-immo")), |
| ("aarch64", "dpb") => Some(LLVMFeature::new("ccpp")), |
| ("aarch64", "dpb2") => Some(LLVMFeature::new("ccdp")), |
| ("aarch64", "frintts") => Some(LLVMFeature::new("fptoint")), |
| ("aarch64", "fcma") => Some(LLVMFeature::new("complxnum")), |
| ("aarch64", "pmuv3") => Some(LLVMFeature::new("perfmon")), |
| ("aarch64", "paca") => Some(LLVMFeature::new("pauth")), |
| ("aarch64", "pacg") => Some(LLVMFeature::new("pauth")), |
| // Before LLVM 20 those two features were packaged together as b16b16 |
| ("aarch64", "sve-b16b16") if get_version().0 < 20 => Some(LLVMFeature::new("b16b16")), |
| ("aarch64", "sme-b16b16") if get_version().0 < 20 => Some(LLVMFeature::new("b16b16")), |
| ("aarch64", "flagm2") => Some(LLVMFeature::new("altnzcv")), |
| // Rust ties fp and neon together. |
| ("aarch64", "neon") => Some(LLVMFeature::with_dependencies( |
| "neon", |
| smallvec![TargetFeatureFoldStrength::Both("fp-armv8")], |
| )), |
| // In LLVM neon implicitly enables fp, but we manually enable |
| // neon when a feature only implicitly enables fp |
| ("aarch64", "fhm") => Some(LLVMFeature::new("fp16fml")), |
| ("aarch64", "fp16") => Some(LLVMFeature::new("fullfp16")), |
| // Filter out features that are not supported by the current LLVM version |
| ("aarch64", "fpmr") => None, // only existed in 18 |
| ("arm", "fp16") => Some(LLVMFeature::new("fullfp16")), |
| // Filter out features that are not supported by the current LLVM version |
| ("loongarch64", "div32" | "lam-bh" | "lamcas" | "ld-seq-sa" | "scq") |
| if get_version().0 < 20 => |
| { |
| None |
| } |
| // Filter out features that are not supported by the current LLVM version |
| ("riscv32" | "riscv64", "zacas") if get_version().0 < 20 => None, |
| ( |
| "s390x", |
| "message-security-assist-extension12" |
| | "concurrent-functions" |
| | "miscellaneous-extensions-4" |
| | "vector-enhancements-3" |
| | "vector-packed-decimal-enhancement-3", |
| ) if get_version().0 < 20 => None, |
| // Enable the evex512 target feature if an avx512 target feature is enabled. |
| ("x86", s) if s.starts_with("avx512") => Some(LLVMFeature::with_dependencies( |
| s, |
| smallvec![TargetFeatureFoldStrength::EnableOnly("evex512")], |
| )), |
| // Support for `wide-arithmetic` will first land in LLVM 20 as part of |
| // llvm/llvm-project#111598 |
| ("wasm32" | "wasm64", "wide-arithmetic") if get_version() < (20, 0, 0) => None, |
| ("sparc", "leoncasa") => Some(LLVMFeature::new("hasleoncasa")), |
| // In LLVM 19, there is no `v8plus` feature and `v9` means "SPARC-V9 instruction available and SPARC-V8+ ABI used". |
| // https://github.com/llvm/llvm-project/blob/llvmorg-19.1.0/llvm/lib/Target/Sparc/MCTargetDesc/SparcELFObjectWriter.cpp#L27-L28 |
| // Before LLVM 19, there was no `v8plus` feature and `v9` means "SPARC-V9 instruction available". |
| // https://github.com/llvm/llvm-project/blob/llvmorg-18.1.0/llvm/lib/Target/Sparc/MCTargetDesc/SparcELFObjectWriter.cpp#L26 |
| ("sparc", "v8plus") if get_version().0 == 19 => Some(LLVMFeature::new("v9")), |
| ("powerpc", "power8-crypto") => Some(LLVMFeature::new("crypto")), |
| // These new `amx` variants and `movrs` were introduced in LLVM20 |
| ("x86", "amx-avx512" | "amx-fp8" | "amx-movrs" | "amx-tf32" | "amx-transpose") |
| if get_version().0 < 20 => |
| { |
| None |
| } |
| ("x86", "movrs") if get_version().0 < 20 => None, |
| ("x86", "avx10.1") => Some(LLVMFeature::new("avx10.1-512")), |
| ("x86", "avx10.2") if get_version().0 < 20 => None, |
| ("x86", "avx10.2") if get_version().0 >= 20 => Some(LLVMFeature::new("avx10.2-512")), |
| ("x86", "apxf") => Some(LLVMFeature::with_dependencies( |
| "egpr", |
| smallvec![ |
| TargetFeatureFoldStrength::Both("push2pop2"), |
| TargetFeatureFoldStrength::Both("ppx"), |
| TargetFeatureFoldStrength::Both("ndd"), |
| TargetFeatureFoldStrength::Both("ccmp"), |
| TargetFeatureFoldStrength::Both("cf"), |
| TargetFeatureFoldStrength::Both("nf"), |
| TargetFeatureFoldStrength::Both("zu"), |
| ], |
| )), |
| (_, s) => Some(LLVMFeature::new(s)), |
| } |
| } |
| |
| /// Used to generate cfg variables and apply features. |
| /// Must express features in the way Rust understands them. |
| /// |
| /// We do not have to worry about RUSTC_SPECIFIC_FEATURES here, those are handled outside codegen. |
| pub(crate) fn target_config(sess: &Session) -> TargetConfig { |
| // Add base features for the target. |
| // We do *not* add the -Ctarget-features there, and instead duplicate the logic for that below. |
| // The reason is that if LLVM considers a feature implied but we do not, we don't want that to |
| // show up in `cfg`. That way, `cfg` is entirely under our control -- except for the handling of |
| // the target CPU, that is still expanded to target features (with all their implied features) |
| // by LLVM. |
| let target_machine = create_informational_target_machine(sess, true); |
| |
| let (unstable_target_features, target_features) = cfg_target_feature(sess, |feature| { |
| if let Some(feat) = to_llvm_features(sess, feature) { |
| // All the LLVM features this expands to must be enabled. |
| for llvm_feature in feat { |
| let cstr = SmallCStr::new(llvm_feature); |
| // `LLVMRustHasFeature` is moderately expensive. On targets with many |
| // features (e.g. x86) these calls take a non-trivial fraction of runtime |
| // when compiling very small programs. |
| if !unsafe { llvm::LLVMRustHasFeature(target_machine.raw(), cstr.as_ptr()) } { |
| return false; |
| } |
| } |
| true |
| } else { |
| false |
| } |
| }); |
| |
| let mut cfg = TargetConfig { |
| target_features, |
| unstable_target_features, |
| has_reliable_f16: true, |
| has_reliable_f16_math: true, |
| has_reliable_f128: true, |
| has_reliable_f128_math: true, |
| }; |
| |
| update_target_reliable_float_cfg(sess, &mut cfg); |
| cfg |
| } |
| |
| /// Determine whether or not experimental float types are reliable based on known bugs. |
| fn update_target_reliable_float_cfg(sess: &Session, cfg: &mut TargetConfig) { |
| let target_arch = sess.target.arch.as_ref(); |
| let target_os = sess.target.options.os.as_ref(); |
| let target_env = sess.target.options.env.as_ref(); |
| let target_abi = sess.target.options.abi.as_ref(); |
| let target_pointer_width = sess.target.pointer_width; |
| let version = get_version(); |
| |
| cfg.has_reliable_f16 = match (target_arch, target_os) { |
| // Selection failure <https://github.com/llvm/llvm-project/issues/50374> |
| ("s390x", _) => false, |
| // LLVM crash without neon <https://github.com/llvm/llvm-project/issues/129394> (now fixed) |
| ("aarch64", _) |
| if !cfg.target_features.iter().any(|f| f.as_str() == "neon") |
| && version < (20, 1, 1) => |
| { |
| false |
| } |
| // Unsupported <https://github.com/llvm/llvm-project/issues/94434> |
| ("arm64ec", _) => false, |
| // MinGW ABI bugs <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115054> |
| ("x86_64", "windows") if target_env == "gnu" && target_abi != "llvm" => false, |
| // Infinite recursion <https://github.com/llvm/llvm-project/issues/97981> |
| ("csky", _) => false, |
| ("hexagon", _) => false, |
| ("powerpc" | "powerpc64", _) => false, |
| ("sparc" | "sparc64", _) => false, |
| ("wasm32" | "wasm64", _) => false, |
| // `f16` support only requires that symbols converting to and from `f32` are available. We |
| // provide these in `compiler-builtins`, so `f16` should be available on all platforms that |
| // do not have other ABI issues or LLVM crashes. |
| _ => true, |
| }; |
| |
| cfg.has_reliable_f128 = match (target_arch, target_os) { |
| // Unsupported <https://github.com/llvm/llvm-project/issues/94434> |
| ("arm64ec", _) => false, |
| // Selection bug <https://github.com/llvm/llvm-project/issues/96432> |
| ("mips64" | "mips64r6", _) => false, |
| // Selection bug <https://github.com/llvm/llvm-project/issues/95471> |
| ("nvptx64", _) => false, |
| // Unsupported https://github.com/llvm/llvm-project/issues/121122 |
| ("amdgpu", _) => false, |
| // ABI bugs <https://github.com/rust-lang/rust/issues/125109> et al. (full |
| // list at <https://github.com/rust-lang/rust/issues/116909>) |
| ("powerpc" | "powerpc64", _) => false, |
| // ABI unsupported <https://github.com/llvm/llvm-project/issues/41838> |
| ("sparc", _) => false, |
| // Stack alignment bug <https://github.com/llvm/llvm-project/issues/77401>. NB: tests may |
| // not fail if our compiler-builtins is linked. |
| ("x86", _) => false, |
| // MinGW ABI bugs <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115054> |
| ("x86_64", "windows") if target_env == "gnu" && target_abi != "llvm" => false, |
| // There are no known problems on other platforms, so the only requirement is that symbols |
| // are available. `compiler-builtins` provides all symbols required for core `f128` |
| // support, so this should work for everything else. |
| _ => true, |
| }; |
| |
| // Assume that working `f16` means working `f16` math for most platforms, since |
| // operations just go through `f32`. |
| cfg.has_reliable_f16_math = cfg.has_reliable_f16; |
| |
| cfg.has_reliable_f128_math = match (target_arch, target_os) { |
| // LLVM lowers `fp128` math to `long double` symbols even on platforms where |
| // `long double` is not IEEE binary128. See |
| // <https://github.com/llvm/llvm-project/issues/44744>. |
| // |
| // This rules out anything that doesn't have `long double` = `binary128`; <= 32 bits |
| // (ld is `f64`), anything other than Linux (Windows and MacOS use `f64`), and `x86` |
| // (ld is 80-bit extended precision). |
| // |
| // musl does not implement the symbols required for f128 math at all. |
| _ if target_env == "musl" => false, |
| ("x86_64", _) => false, |
| (_, "linux") if target_pointer_width == 64 => true, |
| _ => false, |
| } && cfg.has_reliable_f128; |
| } |
| |
| pub(crate) fn print_version() { |
| let (major, minor, patch) = get_version(); |
| println!("LLVM version: {major}.{minor}.{patch}"); |
| } |
| |
| pub(crate) fn get_version() -> (u32, u32, u32) { |
| // Can be called without initializing LLVM |
| unsafe { |
| (llvm::LLVMRustVersionMajor(), llvm::LLVMRustVersionMinor(), llvm::LLVMRustVersionPatch()) |
| } |
| } |
| |
| pub(crate) 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 |
| } |
| |
| pub(crate) fn print(req: &PrintRequest, out: &mut String, sess: &Session) { |
| require_inited(); |
| let tm = create_informational_target_machine(sess, false); |
| match req.kind { |
| PrintKind::TargetCPUs => print_target_cpus(sess, tm.raw(), out), |
| PrintKind::TargetFeatures => print_target_features(sess, tm.raw(), out), |
| _ => bug!("rustc_codegen_llvm can't handle print request: {:?}", req), |
| } |
| } |
| |
| fn print_target_cpus(sess: &Session, tm: &llvm::TargetMachine, out: &mut String) { |
| let cpu_names = llvm::build_string(|s| unsafe { |
| llvm::LLVMRustPrintTargetCPUs(&tm, s); |
| }) |
| .unwrap(); |
| |
| struct Cpu<'a> { |
| cpu_name: &'a str, |
| remark: String, |
| } |
| // Compare CPU against current target to label the default. |
| let target_cpu = handle_native(&sess.target.cpu); |
| let make_remark = |cpu_name| { |
| if cpu_name == target_cpu { |
| // FIXME(#132514): This prints the LLVM target string, which can be |
| // different from the Rust target string. Is that intended? |
| let target = &sess.target.llvm_target; |
| format!( |
| " - This is the default target CPU for the current build target (currently {target})." |
| ) |
| } else { |
| "".to_owned() |
| } |
| }; |
| let mut cpus = cpu_names |
| .lines() |
| .map(|cpu_name| Cpu { cpu_name, remark: make_remark(cpu_name) }) |
| .collect::<VecDeque<_>>(); |
| |
| // Only print the "native" entry when host and target are the same arch, |
| // since otherwise it could be wrong or misleading. |
| if sess.host.arch == sess.target.arch { |
| let host = get_host_cpu_name(); |
| cpus.push_front(Cpu { |
| cpu_name: "native", |
| remark: format!(" - Select the CPU of the current host (currently {host})."), |
| }); |
| } |
| |
| let max_name_width = cpus.iter().map(|cpu| cpu.cpu_name.len()).max().unwrap_or(0); |
| writeln!(out, "Available CPUs for this target:").unwrap(); |
| for Cpu { cpu_name, remark } in cpus { |
| // Only pad the CPU name if there's a remark to print after it. |
| let width = if remark.is_empty() { 0 } else { max_name_width }; |
| writeln!(out, " {cpu_name:<width$}{remark}").unwrap(); |
| } |
| } |
| |
| fn print_target_features(sess: &Session, tm: &llvm::TargetMachine, out: &mut String) { |
| let mut llvm_target_features = llvm_target_features(tm); |
| let mut known_llvm_target_features = FxHashSet::<&'static str>::default(); |
| let mut rustc_target_features = sess |
| .target |
| .rust_target_features() |
| .iter() |
| .filter_map(|(feature, gate, _implied)| { |
| if !gate.in_cfg() { |
| // Only list (experimentally) supported features. |
| return None; |
| } |
| // LLVM asserts that these are sorted. LLVM and Rust both use byte comparison for these |
| // strings. |
| let llvm_feature = to_llvm_features(sess, *feature)?.llvm_feature_name; |
| let desc = |
| match llvm_target_features.binary_search_by_key(&llvm_feature, |(f, _d)| f).ok() { |
| Some(index) => { |
| known_llvm_target_features.insert(llvm_feature); |
| llvm_target_features[index].1 |
| } |
| None => "", |
| }; |
| |
| Some((*feature, desc)) |
| }) |
| .collect::<Vec<_>>(); |
| |
| // Since we add this at the end ... |
| rustc_target_features.extend_from_slice(&[( |
| "crt-static", |
| "Enables C Run-time Libraries to be statically linked", |
| )]); |
| // ... we need to sort the list again. |
| rustc_target_features.sort(); |
| |
| llvm_target_features.retain(|(f, _d)| !known_llvm_target_features.contains(f)); |
| |
| let max_feature_len = llvm_target_features |
| .iter() |
| .chain(rustc_target_features.iter()) |
| .map(|(feature, _desc)| feature.len()) |
| .max() |
| .unwrap_or(0); |
| |
| writeln!(out, "Features supported by rustc for this target:").unwrap(); |
| for (feature, desc) in &rustc_target_features { |
| writeln!(out, " {feature:max_feature_len$} - {desc}.").unwrap(); |
| } |
| writeln!(out, "\nCode-generation features supported by LLVM for this target:").unwrap(); |
| for (feature, desc) in &llvm_target_features { |
| writeln!(out, " {feature:max_feature_len$} - {desc}.").unwrap(); |
| } |
| if llvm_target_features.is_empty() { |
| writeln!(out, " Target features listing is not supported by this LLVM version.") |
| .unwrap(); |
| } |
| writeln!(out, "\nUse +feature to enable a feature, or -feature to disable it.").unwrap(); |
| writeln!(out, "For example, rustc -C target-cpu=mycpu -C target-feature=+feature1,-feature2\n") |
| .unwrap(); |
| writeln!(out, "Code-generation features cannot be used in cfg or #[target_feature],").unwrap(); |
| writeln!(out, "and may be renamed or removed in a future version of LLVM or rustc.\n").unwrap(); |
| } |
| |
| /// Returns the host CPU name, according to LLVM. |
| fn get_host_cpu_name() -> &'static str { |
| let mut len = 0; |
| // SAFETY: The underlying C++ global function returns a `StringRef` that |
| // isn't tied to any particular backing buffer, so it must be 'static. |
| let slice: &'static [u8] = unsafe { |
| let ptr = llvm::LLVMRustGetHostCPUName(&mut len); |
| assert!(!ptr.is_null()); |
| slice::from_raw_parts(ptr, len) |
| }; |
| str::from_utf8(slice).expect("host CPU name should be UTF-8") |
| } |
| |
| /// If the given string is `"native"`, returns the host CPU name according to |
| /// LLVM. Otherwise, the string is returned as-is. |
| fn handle_native(cpu_name: &str) -> &str { |
| match cpu_name { |
| "native" => get_host_cpu_name(), |
| _ => cpu_name, |
| } |
| } |
| |
| pub(crate) fn target_cpu(sess: &Session) -> &str { |
| let cpu_name = sess.opts.cg.target_cpu.as_deref().unwrap_or_else(|| &sess.target.cpu); |
| handle_native(cpu_name) |
| } |
| |
| /// The target features for compiler flags other than `-Ctarget-features`. |
| fn llvm_features_by_flags(sess: &Session, features: &mut Vec<String>) { |
| target_features::retpoline_features_by_flags(sess, features); |
| |
| // -Zfixed-x18 |
| if sess.opts.unstable_opts.fixed_x18 { |
| if sess.target.arch != "aarch64" { |
| sess.dcx().emit_fatal(errors::FixedX18InvalidArch { arch: &sess.target.arch }); |
| } else { |
| features.push("+reserve-x18".into()); |
| } |
| } |
| } |
| |
| /// 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, |
| only_base_features: 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" => { |
| // We have already figured out the actual CPU name with `LLVMRustGetHostCPUName` and set |
| // that for LLVM, so the features implied by that CPU name will be available everywhere. |
| // However, that is not sufficient: e.g. `skylake` alone is not sufficient to tell if |
| // some of the instructions are available or not. So we have to also explicitly ask for |
| // the exact set of features available on the host, and enable all of them. |
| 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()) |
| // Drop +v8plus feature introduced in LLVM 20. |
| // (Hard-coded target features do not go through `to_llvm_feature` since they already |
| // are LLVM feature names, hence we need a special case here.) |
| .filter(|v| *v != "+v8plus" || get_version() >= (20, 0, 0)) |
| .map(String::from), |
| ); |
| |
| if wants_wasm_eh(sess) && sess.panic_strategy() == PanicStrategy::Unwind { |
| features.push("+exception-handling".into()); |
| } |
| |
| // -Ctarget-features |
| if !only_base_features { |
| target_features::flag_to_backend_features( |
| sess, |
| diagnostics, |
| |feature| { |
| to_llvm_features(sess, feature) |
| .map(|f| SmallVec::<[&str; 2]>::from_iter(f.into_iter())) |
| .unwrap_or_default() |
| }, |
| |feature, enable| { |
| let enable_disable = if enable { '+' } else { '-' }; |
| // 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 Some(llvm_feature) = to_llvm_features(sess, feature) else { return }; |
| |
| features.extend( |
| std::iter::once(format!( |
| "{}{}", |
| enable_disable, llvm_feature.llvm_feature_name |
| )) |
| .chain(llvm_feature.dependencies.into_iter().filter_map( |
| move |feat| match (enable, feat) { |
| (_, TargetFeatureFoldStrength::Both(f)) |
| | (true, TargetFeatureFoldStrength::EnableOnly(f)) => { |
| Some(format!("{enable_disable}{f}")) |
| } |
| _ => None, |
| }, |
| )), |
| ) |
| }, |
| ); |
| } |
| |
| // We add this in the "base target" so that these show up in `sess.unstable_target_features`. |
| llvm_features_by_flags(sess, &mut features); |
| |
| features |
| } |
| |
| pub(crate) fn tune_cpu(sess: &Session) -> Option<&str> { |
| let name = sess.opts.unstable_opts.tune_cpu.as_ref()?; |
| Some(handle_native(name)) |
| } |
