diff options
Diffstat (limited to 'compiler/rustc_codegen_llvm/src/llvm_util.rs')
| -rw-r--r-- | compiler/rustc_codegen_llvm/src/llvm_util.rs | 648 |
1 files changed, 648 insertions, 0 deletions
diff --git a/compiler/rustc_codegen_llvm/src/llvm_util.rs b/compiler/rustc_codegen_llvm/src/llvm_util.rs new file mode 100644 index 00000000000..5552b381025 --- /dev/null +++ b/compiler/rustc_codegen_llvm/src/llvm_util.rs @@ -0,0 +1,648 @@ +use crate::back::write::create_informational_target_machine; +use crate::errors::{ + InvalidTargetFeaturePrefix, PossibleFeature, TargetFeatureDisableOrEnable, + UnknownCTargetFeature, UnknownCTargetFeaturePrefix, UnstableCTargetFeature, +}; +use crate::llvm; +use libc::c_int; +use rustc_codegen_ssa::base::wants_wasm_eh; +use rustc_codegen_ssa::traits::PrintBackendInfo; +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::{PrintKind, PrintRequest}; +use rustc_session::Session; +use rustc_span::symbol::Symbol; +use rustc_target::spec::{MergeFunctions, PanicStrategy}; +use rustc_target::target_features::RUSTC_SPECIFIC_FEATURES; + +use std::ffi::{c_char, c_void, 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::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() { + 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.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); + } + } + + if sess.opts.unstable_opts.llvm_time_trace { + llvm::LLVMRustTimeTraceProfilerInitialize(); + } + + 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::LLVMRustTimeTraceProfilerFinish(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, 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 fn to_llvm_features<'a>(sess: &Session, s: &'a str) -> LLVMFeature<'a> { + let arch = if sess.target.arch == "x86_64" { + "x86" + } else if sess.target.arch == "arm64ec" { + "aarch64" + } 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"), + ("x86", "lahfsahf") => LLVMFeature::new("sahf"), + ("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"), + ), + // In LLVM 18, `unaligned-scalar-mem` was merged with `unaligned-vector-mem` into a single feature called + // `fast-unaligned-access`. In LLVM 19, it was split back out. + ("riscv32" | "riscv64", "unaligned-scalar-mem") if get_version().0 == 18 => { + LLVMFeature::new("fast-unaligned-access") + } + // For LLVM 18, enable the evex512 target feature if a avx512 target feature is enabled. + ("x86", s) if get_version().0 >= 18 && s.starts_with("avx512") => { + LLVMFeature::with_dependency(s, TargetFeatureFoldStrength::EnableOnly("evex512")) + } + (_, 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 sess.target.tied_target_features() { + // 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); + sess.target + .supported_target_features() + .iter() + .filter_map(|&(feature, gate)| { + if sess.is_nightly_build() || allow_unstable || gate.is_stable() { + 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(out: &mut dyn PrintBackendInfo, 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 = sess + .target + .supported_target_features() + .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); + + writeln!(out, "Features supported by rustc for this target:"); + for (feature, desc) in &rustc_target_features { + writeln!(out, " {feature:max_feature_len$} - {desc}."); + } + writeln!(out, "\nCode-generation features supported by LLVM for this target:"); + for (feature, desc) in &llvm_target_features { + writeln!(out, " {feature:max_feature_len$} - {desc}."); + } + if llvm_target_features.is_empty() { + writeln!(out, " Target features listing is not supported by this LLVM version."); + } + writeln!(out, "\nUse +feature to enable a feature, or -feature to disable it."); + writeln!(out, "For example, rustc -C target-cpu=mycpu -C target-feature=+feature1,-feature2\n"); + writeln!(out, "Code-generation features cannot be used in cfg or #[target_feature],"); + writeln!(out, "and may be renamed or removed in a future version of LLVM or rustc.\n"); +} + +pub(crate) fn print(req: &PrintRequest, mut out: &mut dyn PrintBackendInfo, sess: &Session) { + require_inited(); + let tm = create_informational_target_machine(sess); + match req.kind { + PrintKind::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 extern "C" fn callback(out: *mut c_void, string: *const c_char, len: usize) { + let out = &mut *(out as *mut &mut dyn PrintBackendInfo); + let bytes = slice::from_raw_parts(string as *const u8, len); + write!(out, "{}", String::from_utf8_lossy(bytes)); + } + unsafe { + llvm::LLVMRustPrintTargetCPUs( + &tm, + cpu_cstring.as_ptr(), + callback, + std::ptr::addr_of_mut!(out) as *mut c_void, + ); + } + } + PrintKind::TargetFeatures => print_target_features(out, 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(sess, v).is_some()) + .map(String::from), + ); + + if wants_wasm_eh(sess) && sess.panic_strategy() == PanicStrategy::Unwind { + features.push("+exception-handling".into()); + } + + // -Ctarget-features + let supported_features = sess.target.supported_target_features(); + 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.dcx().emit_warn(UnknownCTargetFeaturePrefix { feature: s }); + } + return None; + } + }; + + let feature = backend_feature_name(sess, s)?; + // Warn against use of LLVM specific feature names and unstable features on the CLI. + if diagnostics { + let feature_state = supported_features.iter().find(|&&(v, _)| v == feature); + if feature_state.is_none() { + 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.dcx().emit_warn(unknown_feature); + } else if feature_state + .is_some_and(|(_name, feature_gate)| !feature_gate.is_stable()) + { + // An unstable feature. Warn about using it. + sess.dcx().emit_warn(UnstableCTargetFeature { 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.dcx().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<'a>(sess: &Session, s: &'a str) -> Option<&'a str> { + // features must start with a `+` or `-`. + let feature = s + .strip_prefix(&['+', '-'][..]) + .unwrap_or_else(|| sess.dcx().emit_fatal(InvalidTargetFeaturePrefix { feature: 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)) +} |