compiler/rustc_codegen_cranelift/src/driver/jit.rs

   1 //! The JIT driver uses [`cranelift_simplejit`] to JIT execute programs without writing any object
   2 //! files.
   3
   4 use std::cell::RefCell;
   5 use std::ffi::CString;
   6 use std::os::raw::{c_char, c_int};
   7
   8 use rustc_codegen_ssa::CrateInfo;
   9 use rustc_middle::mir::mono::MonoItem;
  10
  11 use cranelift_jit::{JITBuilder, JITModule};
  12
  13 use crate::{prelude::*, BackendConfig};
  14 use crate::{CodegenCx, CodegenMode};
  15
  16 thread_local! {
  17     pub static BACKEND_CONFIG: RefCell<Option<BackendConfig>> = RefCell::new(None);
  18     pub static CURRENT_MODULE: RefCell<Option<JITModule>> = RefCell::new(None);
  19 }
  20
  21 pub(super) fn run_jit(tcx: TyCtxt<'_>, backend_config: BackendConfig) -> ! {
  22     if !tcx.sess.opts.output_types.should_codegen() {
  23         tcx.sess.fatal("JIT mode doesn't work with `cargo check`.");
  24     }
  25
  26     let imported_symbols = load_imported_symbols_for_jit(tcx);
  27
  28     let mut jit_builder =
  29         JITBuilder::with_isa(crate::build_isa(tcx.sess), cranelift_module::default_libcall_names());
  30     jit_builder.hotswap(matches!(backend_config.codegen_mode, CodegenMode::JitLazy));
  31     jit_builder.symbols(imported_symbols);
  32     let mut jit_module = JITModule::new(jit_builder);
  33     assert_eq!(pointer_ty(tcx), jit_module.target_config().pointer_type());
  34
  35     let sig = Signature {
  36         params: vec![
  37             AbiParam::new(jit_module.target_config().pointer_type()),
  38             AbiParam::new(jit_module.target_config().pointer_type()),
  39         ],
  40         returns: vec![AbiParam::new(jit_module.target_config().pointer_type() /*isize*/)],
  41         call_conv: CallConv::triple_default(&crate::target_triple(tcx.sess)),
  42     };
  43     let main_func_id = jit_module.declare_function("main", Linkage::Import, &sig).unwrap();
  44
  45     let (_, cgus) = tcx.collect_and_partition_mono_items(LOCAL_CRATE);
  46     let mono_items = cgus
  47         .iter()
  48         .map(|cgu| cgu.items_in_deterministic_order(tcx).into_iter())
  49         .flatten()
  50         .collect::<FxHashMap<_, (_, _)>>()
  51         .into_iter()
  52         .collect::<Vec<(_, (_, _))>>();
  53
  54     let mut cx = crate::CodegenCx::new(tcx, backend_config, &mut jit_module, false);
  55
  56     super::time(tcx, "codegen mono items", || {
  57         super::predefine_mono_items(&mut cx, &mono_items);
  58         for (mono_item, (linkage, visibility)) in mono_items {
  59             let linkage = crate::linkage::get_clif_linkage(mono_item, linkage, visibility);
  60             match mono_item {
  61                 MonoItem::Fn(inst) => match backend_config.codegen_mode {
  62                     CodegenMode::Aot => unreachable!(),
  63                     CodegenMode::Jit => {
  64                         cx.tcx
  65                             .sess
  66                             .time("codegen fn", || crate::base::codegen_fn(&mut cx, inst, linkage));
  67                     }
  68                     CodegenMode::JitLazy => codegen_shim(&mut cx, inst),
  69                 },
  70                 MonoItem::Static(def_id) => {
  71                     crate::constant::codegen_static(&mut cx.constants_cx, def_id);
  72                 }
  73                 MonoItem::GlobalAsm(item_id) => {
  74                     let item = cx.tcx.hir().item(item_id);
  75                     tcx.sess.span_fatal(item.span, "Global asm is not supported in JIT mode");
  76                 }
  77             }
  78         }
  79     });
  80
  81     let (global_asm, _debug, mut unwind_context) =
  82         tcx.sess.time("finalize CodegenCx", || cx.finalize());
  83     jit_module.finalize_definitions();
  84
  85     if !global_asm.is_empty() {
  86         tcx.sess.fatal("Inline asm is not supported in JIT mode");
  87     }
  88
  89     crate::main_shim::maybe_create_entry_wrapper(tcx, &mut jit_module, &mut unwind_context);
  90     crate::allocator::codegen(tcx, &mut jit_module, &mut unwind_context);
  91
  92     tcx.sess.abort_if_errors();
  93
  94     jit_module.finalize_definitions();
  95
  96     let _unwind_register_guard = unsafe { unwind_context.register_jit(&jit_module) };
  97
  98     let finalized_main: *const u8 = jit_module.get_finalized_function(main_func_id);
  99
 100     println!(
 101         "Rustc codegen cranelift will JIT run the executable, because -Cllvm-args=mode=jit was passed"
 102     );
 103
 104     let f: extern "C" fn(c_int, *const *const c_char) -> c_int =
 105         unsafe { ::std::mem::transmute(finalized_main) };
 106
 107     let args = ::std::env::var("CG_CLIF_JIT_ARGS").unwrap_or_else(|_| String::new());
 108     let args = std::iter::once(&*tcx.crate_name(LOCAL_CRATE).as_str().to_string())
 109         .chain(args.split(' '))
 110         .map(|arg| CString::new(arg).unwrap())
 111         .collect::<Vec<_>>();
 112     let mut argv = args.iter().map(|arg| arg.as_ptr()).collect::<Vec<_>>();
 113
 114     // Push a null pointer as a terminating argument. This is required by POSIX and
 115     // useful as some dynamic linkers use it as a marker to jump over.
 116     argv.push(std::ptr::null());
 117
 118     BACKEND_CONFIG.with(|tls_backend_config| {
 119         assert!(tls_backend_config.borrow_mut().replace(backend_config).is_none())
 120     });
 121     CURRENT_MODULE
 122         .with(|current_module| assert!(current_module.borrow_mut().replace(jit_module).is_none()));
 123
 124     let ret = f(args.len() as c_int, argv.as_ptr());
 125
 126     std::process::exit(ret);
 127 }
 128
 129 #[no_mangle]
 130 extern "C" fn __clif_jit_fn(instance_ptr: *const Instance<'static>) -> *const u8 {
 131     rustc_middle::ty::tls::with(|tcx| {
 132         // lift is used to ensure the correct lifetime for instance.
 133         let instance = tcx.lift(unsafe { *instance_ptr }).unwrap();
 134
 135         CURRENT_MODULE.with(|jit_module| {
 136             let mut jit_module = jit_module.borrow_mut();
 137             let jit_module = jit_module.as_mut().unwrap();
 138             let backend_config =
 139                 BACKEND_CONFIG.with(|backend_config| backend_config.borrow().clone().unwrap());
 140
 141             let name = tcx.symbol_name(instance).name.to_string();
 142             let sig = crate::abi::get_function_sig(tcx, jit_module.isa().triple(), instance);
 143             let func_id = jit_module.declare_function(&name, Linkage::Export, &sig).unwrap();
 144             jit_module.prepare_for_function_redefine(func_id).unwrap();
 145
 146             let mut cx = crate::CodegenCx::new(tcx, backend_config, jit_module, false);
 147             tcx.sess
 148                 .time("codegen fn", || crate::base::codegen_fn(&mut cx, instance, Linkage::Export));
 149
 150             let (global_asm, _debug_context, unwind_context) = cx.finalize();
 151             assert!(global_asm.is_empty());
 152             jit_module.finalize_definitions();
 153             std::mem::forget(unsafe { unwind_context.register_jit(&jit_module) });
 154             jit_module.get_finalized_function(func_id)
 155         })
 156     })
 157 }
 158
 159 fn load_imported_symbols_for_jit(tcx: TyCtxt<'_>) -> Vec<(String, *const u8)> {
 160     use rustc_middle::middle::dependency_format::Linkage;
 161
 162     let mut dylib_paths = Vec::new();
 163
 164     let crate_info = CrateInfo::new(tcx);
 165     let formats = tcx.dependency_formats(LOCAL_CRATE);
 166     let data = &formats
 167         .iter()
 168         .find(|(crate_type, _data)| *crate_type == rustc_session::config::CrateType::Executable)
 169         .unwrap()
 170         .1;
 171     for &(cnum, _) in &crate_info.used_crates_dynamic {
 172         let src = &crate_info.used_crate_source[&cnum];
 173         match data[cnum.as_usize() - 1] {
 174             Linkage::NotLinked | Linkage::IncludedFromDylib => {}
 175             Linkage::Static => {
 176                 let name = tcx.crate_name(cnum);
 177                 let mut err =
 178                     tcx.sess.struct_err(&format!("Can't load static lib {}", name.as_str()));
 179                 err.note("rustc_codegen_cranelift can only load dylibs in JIT mode.");
 180                 err.emit();
 181             }
 182             Linkage::Dynamic => {
 183                 dylib_paths.push(src.dylib.as_ref().unwrap().0.clone());
 184             }
 185         }
 186     }
 187
 188     let mut imported_symbols = Vec::new();
 189     for path in dylib_paths {
 190         use object::{Object, ObjectSymbol};
 191         let lib = libloading::Library::new(&path).unwrap();
 192         let obj = std::fs::read(path).unwrap();
 193         let obj = object::File::parse(&obj).unwrap();
 194         imported_symbols.extend(obj.dynamic_symbols().filter_map(|symbol| {
 195             let name = symbol.name().unwrap().to_string();
 196             if name.is_empty() || !symbol.is_global() || symbol.is_undefined() {
 197                 return None;
 198             }
 199             if name.starts_with("rust_metadata_") {
 200                 // The metadata is part of a section that is not loaded by the dynamic linker in
 201                 // case of cg_llvm.
 202                 return None;
 203             }
 204             let dlsym_name = if cfg!(target_os = "macos") {
 205                 // On macOS `dlsym` expects the name without leading `_`.
 206                 assert!(name.starts_with('_'), "{:?}", name);
 207                 &name[1..]
 208             } else {
 209                 &name
 210             };
 211             let symbol: libloading::Symbol<'_, *const u8> =
 212                 unsafe { lib.get(dlsym_name.as_bytes()) }.unwrap();
 213             Some((name, *symbol))
 214         }));
 215         std::mem::forget(lib)
 216     }
 217
 218     tcx.sess.abort_if_errors();
 219
 220     imported_symbols
 221 }
 222
 223 pub(super) fn codegen_shim<'tcx>(cx: &mut CodegenCx<'_, 'tcx>, inst: Instance<'tcx>) {
 224     let tcx = cx.tcx;
 225
 226     let pointer_type = cx.module.target_config().pointer_type();
 227
 228     let name = tcx.symbol_name(inst).name.to_string();
 229     let sig = crate::abi::get_function_sig(tcx, cx.module.isa().triple(), inst);
 230     let func_id = cx.module.declare_function(&name, Linkage::Export, &sig).unwrap();
 231
 232     let instance_ptr = Box::into_raw(Box::new(inst));
 233
 234     let jit_fn = cx
 235         .module
 236         .declare_function(
 237             "__clif_jit_fn",
 238             Linkage::Import,
 239             &Signature {
 240                 call_conv: cx.module.target_config().default_call_conv,
 241                 params: vec![AbiParam::new(pointer_type)],
 242                 returns: vec![AbiParam::new(pointer_type)],
 243             },
 244         )
 245         .unwrap();
 246
 247     let mut trampoline = Function::with_name_signature(ExternalName::default(), sig.clone());
 248     let mut builder_ctx = FunctionBuilderContext::new();
 249     let mut trampoline_builder = FunctionBuilder::new(&mut trampoline, &mut builder_ctx);
 250
 251     let jit_fn = cx.module.declare_func_in_func(jit_fn, trampoline_builder.func);
 252     let sig_ref = trampoline_builder.func.import_signature(sig);
 253
 254     let entry_block = trampoline_builder.create_block();
 255     trampoline_builder.append_block_params_for_function_params(entry_block);
 256     let fn_args = trampoline_builder.func.dfg.block_params(entry_block).to_vec();
 257
 258     trampoline_builder.switch_to_block(entry_block);
 259     let instance_ptr = trampoline_builder.ins().iconst(pointer_type, instance_ptr as u64 as i64);
 260     let jitted_fn = trampoline_builder.ins().call(jit_fn, &[instance_ptr]);
 261     let jitted_fn = trampoline_builder.func.dfg.inst_results(jitted_fn)[0];
 262     let call_inst = trampoline_builder.ins().call_indirect(sig_ref, jitted_fn, &fn_args);
 263     let ret_vals = trampoline_builder.func.dfg.inst_results(call_inst).to_vec();
 264     trampoline_builder.ins().return_(&ret_vals);
 265
 266     cx.module
 267         .define_function(
 268             func_id,
 269             &mut Context::for_function(trampoline),
 270             &mut cranelift_codegen::binemit::NullTrapSink {},
 271         )
 272         .unwrap();
 273 }