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Diffstat (limited to '')
-rw-r--r-- | compiler/rustc_codegen_llvm/src/llvm_util.rs | 562 |
1 files changed, 562 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 000000000..a0a640473 --- /dev/null +++ b/compiler/rustc_codegen_llvm/src/llvm_util.rs @@ -0,0 +1,562 @@ +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 tracing::debug; + +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); + } + + // Disable the machine outliner by default in LLVM versions 11 and LLVM + // version 12, where it leads to miscompilation. + // + // Ref: + // - https://github.com/rust-lang/rust/issues/85351 + // - https://reviews.llvm.org/D103167 + if llvm_util::get_version() < (13, 0, 0) { + add("-enable-machine-outliner=never", 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 +// 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<Symbol> { + let target_machine = create_informational_target_machine(sess); + let mut features: Vec<Symbol> = 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::<Vec<_>>(); + 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<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()) + .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<bool>, 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)) +} |