compiler/rustc_codegen_llvm/src/llvm_util.rs

   1 use crate::back::write::create_informational_target_machine;
   2 use crate::llvm;
   3 use libc::c_int;
   4 use rustc_codegen_ssa::target_features::supported_target_features;
   5 use rustc_data_structures::fx::FxHashSet;
   6 use rustc_feature::UnstableFeatures;
   7 use rustc_middle::bug;
   8 use rustc_session::config::PrintRequest;
   9 use rustc_session::Session;
  10 use rustc_span::symbol::Symbol;
  11 use rustc_target::spec::{MergeFunctions, PanicStrategy};
  12 use std::ffi::CString;
  13
  14 use std::slice;
  15 use std::str;
  16 use std::sync::atomic::{AtomicBool, Ordering};
  17 use std::sync::Once;
  18
  19 static POISONED: AtomicBool = AtomicBool::new(false);
  20 static INIT: Once = Once::new();
  21
  22 pub(crate) fn init(sess: &Session) {
  23     unsafe {
  24         // Before we touch LLVM, make sure that multithreading is enabled.
  25         INIT.call_once(|| {
  26             if llvm::LLVMStartMultithreaded() != 1 {
  27                 // use an extra bool to make sure that all future usage of LLVM
  28                 // cannot proceed despite the Once not running more than once.
  29                 POISONED.store(true, Ordering::SeqCst);
  30             }
  31
  32             configure_llvm(sess);
  33         });
  34
  35         if POISONED.load(Ordering::SeqCst) {
  36             bug!("couldn't enable multi-threaded LLVM");
  37         }
  38     }
  39 }
  40
  41 fn require_inited() {
  42     INIT.call_once(|| bug!("llvm is not initialized"));
  43     if POISONED.load(Ordering::SeqCst) {
  44         bug!("couldn't enable multi-threaded LLVM");
  45     }
  46 }
  47
  48 unsafe fn configure_llvm(sess: &Session) {
  49     let n_args = sess.opts.cg.llvm_args.len() + sess.target.llvm_args.len();
  50     let mut llvm_c_strs = Vec::with_capacity(n_args + 1);
  51     let mut llvm_args = Vec::with_capacity(n_args + 1);
  52
  53     llvm::LLVMRustInstallFatalErrorHandler();
  54
  55     fn llvm_arg_to_arg_name(full_arg: &str) -> &str {
  56         full_arg.trim().split(|c: char| c == '=' || c.is_whitespace()).next().unwrap_or("")
  57     }
  58
  59     let cg_opts = sess.opts.cg.llvm_args.iter();
  60     let tg_opts = sess.target.llvm_args.iter();
  61     let sess_args = cg_opts.chain(tg_opts);
  62
  63     let user_specified_args: FxHashSet<_> =
  64         sess_args.clone().map(|s| llvm_arg_to_arg_name(s)).filter(|s| !s.is_empty()).collect();
  65
  66     {
  67         // This adds the given argument to LLVM. Unless `force` is true
  68         // user specified arguments are *not* overridden.
  69         let mut add = |arg: &str, force: bool| {
  70             if force || !user_specified_args.contains(llvm_arg_to_arg_name(arg)) {
  71                 let s = CString::new(arg).unwrap();
  72                 llvm_args.push(s.as_ptr());
  73                 llvm_c_strs.push(s);
  74             }
  75         };
  76         // Set the llvm "program name" to make usage and invalid argument messages more clear.
  77         add("rustc -Cllvm-args=\"...\" with", true);
  78         if sess.time_llvm_passes() {
  79             add("-time-passes", false);
  80         }
  81         if sess.print_llvm_passes() {
  82             add("-debug-pass=Structure", false);
  83         }
  84         if !sess.opts.debugging_opts.no_generate_arange_section {
  85             add("-generate-arange-section", false);
  86         }
  87         match sess.opts.debugging_opts.merge_functions.unwrap_or(sess.target.merge_functions) {
  88             MergeFunctions::Disabled | MergeFunctions::Trampolines => {}
  89             MergeFunctions::Aliases => {
  90                 add("-mergefunc-use-aliases", false);
  91             }
  92         }
  93
  94         if sess.target.os == "emscripten" && sess.panic_strategy() == PanicStrategy::Unwind {
  95             add("-enable-emscripten-cxx-exceptions", false);
  96         }
  97
  98         // HACK(eddyb) LLVM inserts `llvm.assume` calls to preserve align attributes
  99         // during inlining. Unfortunately these may block other optimizations.
 100         add("-preserve-alignment-assumptions-during-inlining=false", false);
 101
 102         for arg in sess_args {
 103             add(&(*arg), true);
 104         }
 105     }
 106
 107     if sess.opts.debugging_opts.llvm_time_trace && get_major_version() >= 9 {
 108         // time-trace is not thread safe and running it in parallel will cause seg faults.
 109         if !sess.opts.debugging_opts.no_parallel_llvm {
 110             bug!("`-Z llvm-time-trace` requires `-Z no-parallel-llvm")
 111         }
 112
 113         llvm::LLVMTimeTraceProfilerInitialize();
 114     }
 115
 116     llvm::LLVMInitializePasses();
 117
 118     rustc_llvm::initialize_available_targets();
 119
 120     llvm::LLVMRustSetLLVMOptions(llvm_args.len() as c_int, llvm_args.as_ptr());
 121 }
 122
 123 pub fn time_trace_profiler_finish(file_name: &str) {
 124     unsafe {
 125         if get_major_version() >= 9 {
 126             let file_name = CString::new(file_name).unwrap();
 127             llvm::LLVMTimeTraceProfilerFinish(file_name.as_ptr());
 128         }
 129     }
 130 }
 131
 132 // WARNING: the features after applying `to_llvm_feature` must be known
 133 // to LLVM or the feature detection code will walk past the end of the feature
 134 // array, leading to crashes.
 135 pub fn to_llvm_feature<'a>(sess: &Session, s: &'a str) -> &'a str {
 136     let arch = if sess.target.arch == "x86_64" { "x86" } else { &*sess.target.arch };
 137     match (arch, s) {
 138         ("x86", "pclmulqdq") => "pclmul",
 139         ("x86", "rdrand") => "rdrnd",
 140         ("x86", "bmi1") => "bmi",
 141         ("x86", "cmpxchg16b") => "cx16",
 142         ("aarch64", "fp") => "fp-armv8",
 143         ("aarch64", "fp16") => "fullfp16",
 144         (_, s) => s,
 145     }
 146 }
 147
 148 pub fn target_features(sess: &Session) -> Vec<Symbol> {
 149     let target_machine = create_informational_target_machine(sess);
 150     supported_target_features(sess)
 151         .iter()
 152         .filter_map(|&(feature, gate)| {
 153             if UnstableFeatures::from_environment().is_nightly_build() || gate.is_none() {
 154                 Some(feature)
 155             } else {
 156                 None
 157             }
 158         })
 159         .filter(|feature| {
 160             let llvm_feature = to_llvm_feature(sess, feature);
 161             let cstr = CString::new(llvm_feature).unwrap();
 162             unsafe { llvm::LLVMRustHasFeature(target_machine, cstr.as_ptr()) }
 163         })
 164         .map(|feature| Symbol::intern(feature))
 165         .collect()
 166 }
 167
 168 pub fn print_version() {
 169     // Can be called without initializing LLVM
 170     unsafe {
 171         println!("LLVM version: {}.{}", llvm::LLVMRustVersionMajor(), llvm::LLVMRustVersionMinor());
 172     }
 173 }
 174
 175 pub fn get_major_version() -> u32 {
 176     unsafe { llvm::LLVMRustVersionMajor() }
 177 }
 178
 179 pub fn print_passes() {
 180     // Can be called without initializing LLVM
 181     unsafe {
 182         llvm::LLVMRustPrintPasses();
 183     }
 184 }
 185
 186 pub(crate) fn print(req: PrintRequest, sess: &Session) {
 187     require_inited();
 188     let tm = create_informational_target_machine(sess);
 189     unsafe {
 190         match req {
 191             PrintRequest::TargetCPUs => llvm::LLVMRustPrintTargetCPUs(tm),
 192             PrintRequest::TargetFeatures => llvm::LLVMRustPrintTargetFeatures(tm),
 193             _ => bug!("rustc_codegen_llvm can't handle print request: {:?}", req),
 194         }
 195     }
 196 }
 197
 198 fn handle_native(name: &str) -> &str {
 199     if name != "native" {
 200         return name;
 201     }
 202
 203     unsafe {
 204         let mut len = 0;
 205         let ptr = llvm::LLVMRustGetHostCPUName(&mut len);
 206         str::from_utf8(slice::from_raw_parts(ptr as *const u8, len)).unwrap()
 207     }
 208 }
 209
 210 pub fn target_cpu(sess: &Session) -> &str {
 211     let name = match sess.opts.cg.target_cpu {
 212         Some(ref s) => &**s,
 213         None => &*sess.target.cpu,
 214     };
 215
 216     handle_native(name)
 217 }
 218
 219 pub fn tune_cpu(sess: &Session) -> Option<&str> {
 220     match sess.opts.debugging_opts.tune_cpu {
 221         Some(ref s) => Some(handle_native(&**s)),
 222         None => None,
 223     }
 224 }