src/librustc_codegen_ssa/base.rs

   1 //! Codegen the completed AST to the LLVM IR.
   2 //!
   3 //! Some functions here, such as `codegen_block` and `codegen_expr`, return a value --
   4 //! the result of the codegen to LLVM -- while others, such as `codegen_fn`
   5 //! and `mono_item`, are called only for the side effect of adding a
   6 //! particular definition to the LLVM IR output we're producing.
   7 //!
   8 //! Hopefully useful general knowledge about codegen:
   9 //!
  10 //! * There's no way to find out the `Ty` type of a `Value`. Doing so
  11 //!   would be "trying to get the eggs out of an omelette" (credit:
  12 //!   pcwalton). You can, instead, find out its `llvm::Type` by calling `val_ty`,
  13 //!   but one `llvm::Type` corresponds to many `Ty`s; for instance, `tup(int, int,
  14 //!   int)` and `rec(x=int, y=int, z=int)` will have the same `llvm::Type`.
  15
  16 use crate::back::write::{
  17     start_async_codegen, submit_codegened_module_to_llvm, submit_post_lto_module_to_llvm,
  18     submit_pre_lto_module_to_llvm, OngoingCodegen,
  19 };
  20 use crate::common::{IntPredicate, RealPredicate, TypeKind};
  21 use crate::meth;
  22 use crate::mir;
  23 use crate::mir::operand::OperandValue;
  24 use crate::mir::place::PlaceRef;
  25 use crate::traits::*;
  26 use crate::{CachedModuleCodegen, CrateInfo, MemFlags, ModuleCodegen, ModuleKind};
  27
  28 use rustc::middle::codegen_fn_attrs::CodegenFnAttrs;
  29 use rustc::middle::cstore::EncodedMetadata;
  30 use rustc::middle::cstore::{self, LinkagePreference};
  31 use rustc::middle::lang_items::StartFnLangItem;
  32 use rustc::middle::weak_lang_items;
  33 use rustc::mir::mono::{CodegenUnit, CodegenUnitNameBuilder, MonoItem};
  34 use rustc::session::config::{self, EntryFnType, Lto};
  35 use rustc::session::Session;
  36 use rustc::ty::layout::{self, Align, HasTyCtxt, LayoutOf, TyLayout, VariantIdx};
  37 use rustc::ty::layout::{FAT_PTR_ADDR, FAT_PTR_EXTRA};
  38 use rustc::ty::query::Providers;
  39 use rustc::ty::{self, Instance, Ty, TyCtxt};
  40 use rustc_codegen_utils::{check_for_rustc_errors_attr, symbol_names_test};
  41 use rustc_data_structures::fx::FxHashMap;
  42 use rustc_data_structures::profiling::print_time_passes_entry;
  43 use rustc_data_structures::sync::{par_iter, Lock, ParallelIterator};
  44 use rustc_hir as hir;
  45 use rustc_hir::def_id::{DefId, LOCAL_CRATE};
  46 use rustc_index::vec::Idx;
  47 use rustc_session::cgu_reuse_tracker::CguReuse;
  48 use rustc_span::Span;
  49 use syntax::attr;
  50
  51 use std::cmp;
  52 use std::ops::{Deref, DerefMut};
  53 use std::time::{Duration, Instant};
  54
  55 pub fn bin_op_to_icmp_predicate(op: hir::BinOpKind, signed: bool) -> IntPredicate {
  56     match op {
  57         hir::BinOpKind::Eq => IntPredicate::IntEQ,
  58         hir::BinOpKind::Ne => IntPredicate::IntNE,
  59         hir::BinOpKind::Lt => {
  60             if signed {
  61                 IntPredicate::IntSLT
  62             } else {
  63                 IntPredicate::IntULT
  64             }
  65         }
  66         hir::BinOpKind::Le => {
  67             if signed {
  68                 IntPredicate::IntSLE
  69             } else {
  70                 IntPredicate::IntULE
  71             }
  72         }
  73         hir::BinOpKind::Gt => {
  74             if signed {
  75                 IntPredicate::IntSGT
  76             } else {
  77                 IntPredicate::IntUGT
  78             }
  79         }
  80         hir::BinOpKind::Ge => {
  81             if signed {
  82                 IntPredicate::IntSGE
  83             } else {
  84                 IntPredicate::IntUGE
  85             }
  86         }
  87         op => bug!(
  88             "comparison_op_to_icmp_predicate: expected comparison operator, \
  89              found {:?}",
  90             op
  91         ),
  92     }
  93 }
  94
  95 pub fn bin_op_to_fcmp_predicate(op: hir::BinOpKind) -> RealPredicate {
  96     match op {
  97         hir::BinOpKind::Eq => RealPredicate::RealOEQ,
  98         hir::BinOpKind::Ne => RealPredicate::RealUNE,
  99         hir::BinOpKind::Lt => RealPredicate::RealOLT,
 100         hir::BinOpKind::Le => RealPredicate::RealOLE,
 101         hir::BinOpKind::Gt => RealPredicate::RealOGT,
 102         hir::BinOpKind::Ge => RealPredicate::RealOGE,
 103         op => {
 104             bug!(
 105                 "comparison_op_to_fcmp_predicate: expected comparison operator, \
 106                  found {:?}",
 107                 op
 108             );
 109         }
 110     }
 111 }
 112
 113 pub fn compare_simd_types<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
 114     bx: &mut Bx,
 115     lhs: Bx::Value,
 116     rhs: Bx::Value,
 117     t: Ty<'tcx>,
 118     ret_ty: Bx::Type,
 119     op: hir::BinOpKind,
 120 ) -> Bx::Value {
 121     let signed = match t.kind {
 122         ty::Float(_) => {
 123             let cmp = bin_op_to_fcmp_predicate(op);
 124             let cmp = bx.fcmp(cmp, lhs, rhs);
 125             return bx.sext(cmp, ret_ty);
 126         }
 127         ty::Uint(_) => false,
 128         ty::Int(_) => true,
 129         _ => bug!("compare_simd_types: invalid SIMD type"),
 130     };
 131
 132     let cmp = bin_op_to_icmp_predicate(op, signed);
 133     let cmp = bx.icmp(cmp, lhs, rhs);
 134     // LLVM outputs an `< size x i1 >`, so we need to perform a sign extension
 135     // to get the correctly sized type. This will compile to a single instruction
 136     // once the IR is converted to assembly if the SIMD instruction is supported
 137     // by the target architecture.
 138     bx.sext(cmp, ret_ty)
 139 }
 140
 141 /// Retrieves the information we are losing (making dynamic) in an unsizing
 142 /// adjustment.
 143 ///
 144 /// The `old_info` argument is a bit odd. It is intended for use in an upcast,
 145 /// where the new vtable for an object will be derived from the old one.
 146 pub fn unsized_info<'tcx, Cx: CodegenMethods<'tcx>>(
 147     cx: &Cx,
 148     source: Ty<'tcx>,
 149     target: Ty<'tcx>,
 150     old_info: Option<Cx::Value>,
 151 ) -> Cx::Value {
 152     let (source, target) =
 153         cx.tcx().struct_lockstep_tails_erasing_lifetimes(source, target, cx.param_env());
 154     match (&source.kind, &target.kind) {
 155         (&ty::Array(_, len), &ty::Slice(_)) => {
 156             cx.const_usize(len.eval_usize(cx.tcx(), ty::ParamEnv::reveal_all()))
 157         }
 158         (&ty::Dynamic(..), &ty::Dynamic(..)) => {
 159             // For now, upcasts are limited to changes in marker
 160             // traits, and hence never actually require an actual
 161             // change to the vtable.
 162             old_info.expect("unsized_info: missing old info for trait upcast")
 163         }
 164         (_, &ty::Dynamic(ref data, ..)) => {
 165             let vtable_ptr = cx.layout_of(cx.tcx().mk_mut_ptr(target)).field(cx, FAT_PTR_EXTRA);
 166             cx.const_ptrcast(
 167                 meth::get_vtable(cx, source, data.principal()),
 168                 cx.backend_type(vtable_ptr),
 169             )
 170         }
 171         _ => bug!("unsized_info: invalid unsizing {:?} -> {:?}", source, target),
 172     }
 173 }
 174
 175 /// Coerces `src` to `dst_ty`. `src_ty` must be a thin pointer.
 176 pub fn unsize_thin_ptr<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
 177     bx: &mut Bx,
 178     src: Bx::Value,
 179     src_ty: Ty<'tcx>,
 180     dst_ty: Ty<'tcx>,
 181 ) -> (Bx::Value, Bx::Value) {
 182     debug!("unsize_thin_ptr: {:?} => {:?}", src_ty, dst_ty);
 183     match (&src_ty.kind, &dst_ty.kind) {
 184         (&ty::Ref(_, a, _), &ty::Ref(_, b, _))
 185         | (&ty::Ref(_, a, _), &ty::RawPtr(ty::TypeAndMut { ty: b, .. }))
 186         | (&ty::RawPtr(ty::TypeAndMut { ty: a, .. }), &ty::RawPtr(ty::TypeAndMut { ty: b, .. })) => {
 187             assert!(bx.cx().type_is_sized(a));
 188             let ptr_ty = bx.cx().type_ptr_to(bx.cx().backend_type(bx.cx().layout_of(b)));
 189             (bx.pointercast(src, ptr_ty), unsized_info(bx.cx(), a, b, None))
 190         }
 191         (&ty::Adt(def_a, _), &ty::Adt(def_b, _)) => {
 192             assert_eq!(def_a, def_b);
 193
 194             let src_layout = bx.cx().layout_of(src_ty);
 195             let dst_layout = bx.cx().layout_of(dst_ty);
 196             let mut result = None;
 197             for i in 0..src_layout.fields.count() {
 198                 let src_f = src_layout.field(bx.cx(), i);
 199                 assert_eq!(src_layout.fields.offset(i).bytes(), 0);
 200                 assert_eq!(dst_layout.fields.offset(i).bytes(), 0);
 201                 if src_f.is_zst() {
 202                     continue;
 203                 }
 204                 assert_eq!(src_layout.size, src_f.size);
 205
 206                 let dst_f = dst_layout.field(bx.cx(), i);
 207                 assert_ne!(src_f.ty, dst_f.ty);
 208                 assert_eq!(result, None);
 209                 result = Some(unsize_thin_ptr(bx, src, src_f.ty, dst_f.ty));
 210             }
 211             let (lldata, llextra) = result.unwrap();
 212             // HACK(eddyb) have to bitcast pointers until LLVM removes pointee types.
 213             // FIXME(eddyb) move these out of this `match` arm, so they're always
 214             // applied, uniformly, no matter the source/destination types.
 215             (
 216                 bx.bitcast(lldata, bx.cx().scalar_pair_element_backend_type(dst_layout, 0, true)),
 217                 bx.bitcast(llextra, bx.cx().scalar_pair_element_backend_type(dst_layout, 1, true)),
 218             )
 219         }
 220         _ => bug!("unsize_thin_ptr: called on bad types"),
 221     }
 222 }
 223
 224 /// Coerces `src`, which is a reference to a value of type `src_ty`,
 225 /// to a value of type `dst_ty`, and stores the result in `dst`.
 226 pub fn coerce_unsized_into<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
 227     bx: &mut Bx,
 228     src: PlaceRef<'tcx, Bx::Value>,
 229     dst: PlaceRef<'tcx, Bx::Value>,
 230 ) {
 231     let src_ty = src.layout.ty;
 232     let dst_ty = dst.layout.ty;
 233     match (&src_ty.kind, &dst_ty.kind) {
 234         (&ty::Ref(..), &ty::Ref(..))
 235         | (&ty::Ref(..), &ty::RawPtr(..))
 236         | (&ty::RawPtr(..), &ty::RawPtr(..)) => {
 237             let (base, info) = match bx.load_operand(src).val {
 238                 OperandValue::Pair(base, info) => {
 239                     // fat-ptr to fat-ptr unsize preserves the vtable
 240                     // i.e., &'a fmt::Debug+Send => &'a fmt::Debug
 241                     // So we need to pointercast the base to ensure
 242                     // the types match up.
 243                     // FIXME(eddyb) use `scalar_pair_element_backend_type` here,
 244                     // like `unsize_thin_ptr` does.
 245                     let thin_ptr = dst.layout.field(bx.cx(), FAT_PTR_ADDR);
 246                     (bx.pointercast(base, bx.cx().backend_type(thin_ptr)), info)
 247                 }
 248                 OperandValue::Immediate(base) => unsize_thin_ptr(bx, base, src_ty, dst_ty),
 249                 OperandValue::Ref(..) => bug!(),
 250             };
 251             OperandValue::Pair(base, info).store(bx, dst);
 252         }
 253
 254         (&ty::Adt(def_a, _), &ty::Adt(def_b, _)) => {
 255             assert_eq!(def_a, def_b);
 256
 257             for i in 0..def_a.variants[VariantIdx::new(0)].fields.len() {
 258                 let src_f = src.project_field(bx, i);
 259                 let dst_f = dst.project_field(bx, i);
 260
 261                 if dst_f.layout.is_zst() {
 262                     continue;
 263                 }
 264
 265                 if src_f.layout.ty == dst_f.layout.ty {
 266                     memcpy_ty(
 267                         bx,
 268                         dst_f.llval,
 269                         dst_f.align,
 270                         src_f.llval,
 271                         src_f.align,
 272                         src_f.layout,
 273                         MemFlags::empty(),
 274                     );
 275                 } else {
 276                     coerce_unsized_into(bx, src_f, dst_f);
 277                 }
 278             }
 279         }
 280         _ => bug!("coerce_unsized_into: invalid coercion {:?} -> {:?}", src_ty, dst_ty,),
 281     }
 282 }
 283
 284 pub fn cast_shift_expr_rhs<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
 285     bx: &mut Bx,
 286     op: hir::BinOpKind,
 287     lhs: Bx::Value,
 288     rhs: Bx::Value,
 289 ) -> Bx::Value {
 290     cast_shift_rhs(bx, op, lhs, rhs)
 291 }
 292
 293 fn cast_shift_rhs<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
 294     bx: &mut Bx,
 295     op: hir::BinOpKind,
 296     lhs: Bx::Value,
 297     rhs: Bx::Value,
 298 ) -> Bx::Value {
 299     // Shifts may have any size int on the rhs
 300     if op.is_shift() {
 301         let mut rhs_llty = bx.cx().val_ty(rhs);
 302         let mut lhs_llty = bx.cx().val_ty(lhs);
 303         if bx.cx().type_kind(rhs_llty) == TypeKind::Vector {
 304             rhs_llty = bx.cx().element_type(rhs_llty)
 305         }
 306         if bx.cx().type_kind(lhs_llty) == TypeKind::Vector {
 307             lhs_llty = bx.cx().element_type(lhs_llty)
 308         }
 309         let rhs_sz = bx.cx().int_width(rhs_llty);
 310         let lhs_sz = bx.cx().int_width(lhs_llty);
 311         if lhs_sz < rhs_sz {
 312             bx.trunc(rhs, lhs_llty)
 313         } else if lhs_sz > rhs_sz {
 314             // FIXME (#1877: If in the future shifting by negative
 315             // values is no longer undefined then this is wrong.
 316             bx.zext(rhs, lhs_llty)
 317         } else {
 318             rhs
 319         }
 320     } else {
 321         rhs
 322     }
 323 }
 324
 325 /// Returns `true` if this session's target will use SEH-based unwinding.
 326 ///
 327 /// This is only true for MSVC targets, and even then the 64-bit MSVC target
 328 /// currently uses SEH-ish unwinding with DWARF info tables to the side (same as
 329 /// 64-bit MinGW) instead of "full SEH".
 330 pub fn wants_msvc_seh(sess: &Session) -> bool {
 331     sess.target.target.options.is_like_msvc
 332 }
 333
 334 pub fn from_immediate<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
 335     bx: &mut Bx,
 336     val: Bx::Value,
 337 ) -> Bx::Value {
 338     if bx.cx().val_ty(val) == bx.cx().type_i1() { bx.zext(val, bx.cx().type_i8()) } else { val }
 339 }
 340
 341 pub fn to_immediate<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
 342     bx: &mut Bx,
 343     val: Bx::Value,
 344     layout: layout::TyLayout<'_>,
 345 ) -> Bx::Value {
 346     if let layout::Abi::Scalar(ref scalar) = layout.abi {
 347         return to_immediate_scalar(bx, val, scalar);
 348     }
 349     val
 350 }
 351
 352 pub fn to_immediate_scalar<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
 353     bx: &mut Bx,
 354     val: Bx::Value,
 355     scalar: &layout::Scalar,
 356 ) -> Bx::Value {
 357     if scalar.is_bool() {
 358         return bx.trunc(val, bx.cx().type_i1());
 359     }
 360     val
 361 }
 362
 363 pub fn memcpy_ty<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
 364     bx: &mut Bx,
 365     dst: Bx::Value,
 366     dst_align: Align,
 367     src: Bx::Value,
 368     src_align: Align,
 369     layout: TyLayout<'tcx>,
 370     flags: MemFlags,
 371 ) {
 372     let size = layout.size.bytes();
 373     if size == 0 {
 374         return;
 375     }
 376
 377     bx.memcpy(dst, dst_align, src, src_align, bx.cx().const_usize(size), flags);
 378 }
 379
 380 pub fn codegen_instance<'a, 'tcx: 'a, Bx: BuilderMethods<'a, 'tcx>>(
 381     cx: &'a Bx::CodegenCx,
 382     instance: Instance<'tcx>,
 383 ) {
 384     // this is an info! to allow collecting monomorphization statistics
 385     // and to allow finding the last function before LLVM aborts from
 386     // release builds.
 387     info!("codegen_instance({})", instance);
 388
 389     mir::codegen_mir::<Bx>(cx, instance);
 390 }
 391
 392 /// Creates the `main` function which will initialize the rust runtime and call
 393 /// users main function.
 394 pub fn maybe_create_entry_wrapper<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(cx: &'a Bx::CodegenCx) {
 395     let (main_def_id, span) = match cx.tcx().entry_fn(LOCAL_CRATE) {
 396         Some((def_id, _)) => (def_id, cx.tcx().def_span(def_id)),
 397         None => return,
 398     };
 399
 400     let instance = Instance::mono(cx.tcx(), main_def_id);
 401
 402     if !cx.codegen_unit().contains_item(&MonoItem::Fn(instance)) {
 403         // We want to create the wrapper in the same codegen unit as Rust's main
 404         // function.
 405         return;
 406     }
 407
 408     let main_llfn = cx.get_fn_addr(instance);
 409
 410     let et = cx.tcx().entry_fn(LOCAL_CRATE).map(|e| e.1);
 411     match et {
 412         Some(EntryFnType::Main) => create_entry_fn::<Bx>(cx, span, main_llfn, main_def_id, true),
 413         Some(EntryFnType::Start) => create_entry_fn::<Bx>(cx, span, main_llfn, main_def_id, false),
 414         None => {} // Do nothing.
 415     }
 416
 417     fn create_entry_fn<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
 418         cx: &'a Bx::CodegenCx,
 419         sp: Span,
 420         rust_main: Bx::Value,
 421         rust_main_def_id: DefId,
 422         use_start_lang_item: bool,
 423     ) {
 424         // The entry function is either `int main(void)` or `int main(int argc, char **argv)`,
 425         // depending on whether the target needs `argc` and `argv` to be passed in.
 426         let llfty = if cx.sess().target.target.options.main_needs_argc_argv {
 427             cx.type_func(&[cx.type_int(), cx.type_ptr_to(cx.type_i8p())], cx.type_int())
 428         } else {
 429             cx.type_func(&[], cx.type_int())
 430         };
 431
 432         let main_ret_ty = cx.tcx().fn_sig(rust_main_def_id).output();
 433         // Given that `main()` has no arguments,
 434         // then its return type cannot have
 435         // late-bound regions, since late-bound
 436         // regions must appear in the argument
 437         // listing.
 438         let main_ret_ty = cx.tcx().erase_regions(&main_ret_ty.no_bound_vars().unwrap());
 439
 440         if cx.get_defined_value("main").is_some() {
 441             // FIXME: We should be smart and show a better diagnostic here.
 442             cx.sess()
 443                 .struct_span_err(sp, "entry symbol `main` defined multiple times")
 444                 .help("did you use `#[no_mangle]` on `fn main`? Use `#[start]` instead")
 445                 .emit();
 446             cx.sess().abort_if_errors();
 447             bug!();
 448         }
 449         let llfn = cx.declare_cfn("main", llfty);
 450
 451         // `main` should respect same config for frame pointer elimination as rest of code
 452         cx.set_frame_pointer_elimination(llfn);
 453         cx.apply_target_cpu_attr(llfn);
 454
 455         let mut bx = Bx::new_block(&cx, llfn, "top");
 456
 457         bx.insert_reference_to_gdb_debug_scripts_section_global();
 458
 459         let (arg_argc, arg_argv) = get_argc_argv(cx, &mut bx);
 460
 461         let (start_fn, args) = if use_start_lang_item {
 462             let start_def_id = cx.tcx().require_lang_item(StartFnLangItem, None);
 463             let start_fn = cx.get_fn_addr(
 464                 ty::Instance::resolve(
 465                     cx.tcx(),
 466                     ty::ParamEnv::reveal_all(),
 467                     start_def_id,
 468                     cx.tcx().intern_substs(&[main_ret_ty.into()]),
 469                 )
 470                 .unwrap(),
 471             );
 472             (
 473                 start_fn,
 474                 vec![bx.pointercast(rust_main, cx.type_ptr_to(cx.type_i8p())), arg_argc, arg_argv],
 475             )
 476         } else {
 477             debug!("using user-defined start fn");
 478             (rust_main, vec![arg_argc, arg_argv])
 479         };
 480
 481         let result = bx.call(start_fn, &args, None);
 482         let cast = bx.intcast(result, cx.type_int(), true);
 483         bx.ret(cast);
 484     }
 485 }
 486
 487 /// Obtain the `argc` and `argv` values to pass to the rust start function.
 488 fn get_argc_argv<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
 489     cx: &'a Bx::CodegenCx,
 490     bx: &mut Bx,
 491 ) -> (Bx::Value, Bx::Value) {
 492     if cx.sess().target.target.options.main_needs_argc_argv {
 493         // Params from native `main()` used as args for rust start function
 494         let param_argc = bx.get_param(0);
 495         let param_argv = bx.get_param(1);
 496         let arg_argc = bx.intcast(param_argc, cx.type_isize(), true);
 497         let arg_argv = param_argv;
 498         (arg_argc, arg_argv)
 499     } else {
 500         // The Rust start function doesn't need `argc` and `argv`, so just pass zeros.
 501         let arg_argc = bx.const_int(cx.type_int(), 0);
 502         let arg_argv = bx.const_null(cx.type_ptr_to(cx.type_i8p()));
 503         (arg_argc, arg_argv)
 504     }
 505 }
 506
 507 pub const CODEGEN_WORKER_ID: usize = ::std::usize::MAX;
 508
 509 pub fn codegen_crate<B: ExtraBackendMethods>(
 510     backend: B,
 511     tcx: TyCtxt<'tcx>,
 512     metadata: EncodedMetadata,
 513     need_metadata_module: bool,
 514 ) -> OngoingCodegen<B> {
 515     check_for_rustc_errors_attr(tcx);
 516
 517     // Skip crate items and just output metadata in -Z no-codegen mode.
 518     if tcx.sess.opts.debugging_opts.no_codegen || !tcx.sess.opts.output_types.should_codegen() {
 519         let ongoing_codegen = start_async_codegen(backend, tcx, metadata, 1);
 520
 521         ongoing_codegen.codegen_finished(tcx);
 522
 523         finalize_tcx(tcx);
 524
 525         ongoing_codegen.check_for_errors(tcx.sess);
 526
 527         return ongoing_codegen;
 528     }
 529
 530     let cgu_name_builder = &mut CodegenUnitNameBuilder::new(tcx);
 531
 532     // Run the monomorphization collector and partition the collected items into
 533     // codegen units.
 534     let codegen_units = tcx.collect_and_partition_mono_items(LOCAL_CRATE).1;
 535     let codegen_units = (*codegen_units).clone();
 536
 537     // Force all codegen_unit queries so they are already either red or green
 538     // when compile_codegen_unit accesses them. We are not able to re-execute
 539     // the codegen_unit query from just the DepNode, so an unknown color would
 540     // lead to having to re-execute compile_codegen_unit, possibly
 541     // unnecessarily.
 542     if tcx.dep_graph.is_fully_enabled() {
 543         for cgu in &codegen_units {
 544             tcx.codegen_unit(cgu.name());
 545         }
 546     }
 547
 548     let ongoing_codegen = start_async_codegen(backend.clone(), tcx, metadata, codegen_units.len());
 549     let ongoing_codegen = AbortCodegenOnDrop::<B>(Some(ongoing_codegen));
 550
 551     // Codegen an allocator shim, if necessary.
 552     //
 553     // If the crate doesn't have an `allocator_kind` set then there's definitely
 554     // no shim to generate. Otherwise we also check our dependency graph for all
 555     // our output crate types. If anything there looks like its a `Dynamic`
 556     // linkage, then it's already got an allocator shim and we'll be using that
 557     // one instead. If nothing exists then it's our job to generate the
 558     // allocator!
 559     let any_dynamic_crate = tcx.dependency_formats(LOCAL_CRATE).iter().any(|(_, list)| {
 560         use rustc::middle::dependency_format::Linkage;
 561         list.iter().any(|&linkage| linkage == Linkage::Dynamic)
 562     });
 563     let allocator_module = if any_dynamic_crate {
 564         None
 565     } else if let Some(kind) = tcx.allocator_kind() {
 566         let llmod_id =
 567             cgu_name_builder.build_cgu_name(LOCAL_CRATE, &["crate"], Some("allocator")).to_string();
 568         let mut modules = backend.new_metadata(tcx, &llmod_id);
 569         tcx.sess
 570             .time("write_allocator_module", || backend.codegen_allocator(tcx, &mut modules, kind));
 571
 572         Some(ModuleCodegen { name: llmod_id, module_llvm: modules, kind: ModuleKind::Allocator })
 573     } else {
 574         None
 575     };
 576
 577     if let Some(allocator_module) = allocator_module {
 578         ongoing_codegen.submit_pre_codegened_module_to_llvm(tcx, allocator_module);
 579     }
 580
 581     if need_metadata_module {
 582         // Codegen the encoded metadata.
 583         let metadata_cgu_name =
 584             cgu_name_builder.build_cgu_name(LOCAL_CRATE, &["crate"], Some("metadata")).to_string();
 585         let mut metadata_llvm_module = backend.new_metadata(tcx, &metadata_cgu_name);
 586         tcx.sess.time("write_compressed_metadata", || {
 587             backend.write_compressed_metadata(
 588                 tcx,
 589                 &ongoing_codegen.metadata,
 590                 &mut metadata_llvm_module,
 591             );
 592         });
 593
 594         let metadata_module = ModuleCodegen {
 595             name: metadata_cgu_name,
 596             module_llvm: metadata_llvm_module,
 597             kind: ModuleKind::Metadata,
 598         };
 599         ongoing_codegen.submit_pre_codegened_module_to_llvm(tcx, metadata_module);
 600     }
 601
 602     // We sort the codegen units by size. This way we can schedule work for LLVM
 603     // a bit more efficiently.
 604     let codegen_units = {
 605         let mut codegen_units = codegen_units;
 606         codegen_units.sort_by_cached_key(|cgu| cmp::Reverse(cgu.size_estimate()));
 607         codegen_units
 608     };
 609
 610     let total_codegen_time = Lock::new(Duration::new(0, 0));
 611
 612     // The non-parallel compiler can only translate codegen units to LLVM IR
 613     // on a single thread, leading to a staircase effect where the N LLVM
 614     // threads have to wait on the single codegen threads to generate work
 615     // for them. The parallel compiler does not have this restriction, so
 616     // we can pre-load the LLVM queue in parallel before handing off
 617     // coordination to the OnGoingCodegen scheduler.
 618     //
 619     // This likely is a temporary measure. Once we don't have to support the
 620     // non-parallel compiler anymore, we can compile CGUs end-to-end in
 621     // parallel and get rid of the complicated scheduling logic.
 622     let pre_compile_cgus = |cgu_reuse: &[CguReuse]| {
 623         if cfg!(parallel_compiler) {
 624             tcx.sess.time("compile_first_CGU_batch", || {
 625                 // Try to find one CGU to compile per thread.
 626                 let cgus: Vec<_> = cgu_reuse
 627                     .iter()
 628                     .enumerate()
 629                     .filter(|&(_, reuse)| reuse == &CguReuse::No)
 630                     .take(tcx.sess.threads())
 631                     .collect();
 632
 633                 // Compile the found CGUs in parallel.
 634                 par_iter(cgus)
 635                     .map(|(i, _)| {
 636                         let start_time = Instant::now();
 637                         let module = backend.compile_codegen_unit(tcx, codegen_units[i].name());
 638                         let mut time = total_codegen_time.lock();
 639                         *time += start_time.elapsed();
 640                         (i, module)
 641                     })
 642                     .collect()
 643             })
 644         } else {
 645             FxHashMap::default()
 646         }
 647     };
 648
 649     let mut cgu_reuse = Vec::new();
 650     let mut pre_compiled_cgus: Option<FxHashMap<usize, _>> = None;
 651
 652     for (i, cgu) in codegen_units.iter().enumerate() {
 653         ongoing_codegen.wait_for_signal_to_codegen_item();
 654         ongoing_codegen.check_for_errors(tcx.sess);
 655
 656         // Do some setup work in the first iteration
 657         if pre_compiled_cgus.is_none() {
 658             // Calculate the CGU reuse
 659             cgu_reuse = tcx.sess.time("find_cgu_reuse", || {
 660                 codegen_units.iter().map(|cgu| determine_cgu_reuse(tcx, &cgu)).collect()
 661             });
 662             // Pre compile some CGUs
 663             pre_compiled_cgus = Some(pre_compile_cgus(&cgu_reuse));
 664         }
 665
 666         let cgu_reuse = cgu_reuse[i];
 667         tcx.sess.cgu_reuse_tracker.set_actual_reuse(&cgu.name().as_str(), cgu_reuse);
 668
 669         match cgu_reuse {
 670             CguReuse::No => {
 671                 let (module, cost) =
 672                     if let Some(cgu) = pre_compiled_cgus.as_mut().unwrap().remove(&i) {
 673                         cgu
 674                     } else {
 675                         let start_time = Instant::now();
 676                         let module = backend.compile_codegen_unit(tcx, cgu.name());
 677                         let mut time = total_codegen_time.lock();
 678                         *time += start_time.elapsed();
 679                         module
 680                     };
 681                 submit_codegened_module_to_llvm(
 682                     &backend,
 683                     &ongoing_codegen.coordinator_send,
 684                     module,
 685                     cost,
 686                 );
 687                 false
 688             }
 689             CguReuse::PreLto => {
 690                 submit_pre_lto_module_to_llvm(
 691                     &backend,
 692                     tcx,
 693                     &ongoing_codegen.coordinator_send,
 694                     CachedModuleCodegen {
 695                         name: cgu.name().to_string(),
 696                         source: cgu.work_product(tcx),
 697                     },
 698                 );
 699                 true
 700             }
 701             CguReuse::PostLto => {
 702                 submit_post_lto_module_to_llvm(
 703                     &backend,
 704                     &ongoing_codegen.coordinator_send,
 705                     CachedModuleCodegen {
 706                         name: cgu.name().to_string(),
 707                         source: cgu.work_product(tcx),
 708                     },
 709                 );
 710                 true
 711             }
 712         };
 713     }
 714
 715     ongoing_codegen.codegen_finished(tcx);
 716
 717     // Since the main thread is sometimes blocked during codegen, we keep track
 718     // -Ztime-passes output manually.
 719     print_time_passes_entry(
 720         tcx.sess.time_passes(),
 721         "codegen_to_LLVM_IR",
 722         total_codegen_time.into_inner(),
 723     );
 724
 725     ::rustc_incremental::assert_module_sources::assert_module_sources(tcx);
 726
 727     symbol_names_test::report_symbol_names(tcx);
 728
 729     ongoing_codegen.check_for_errors(tcx.sess);
 730
 731     finalize_tcx(tcx);
 732
 733     ongoing_codegen.into_inner()
 734 }
 735
 736 /// A curious wrapper structure whose only purpose is to call `codegen_aborted`
 737 /// when it's dropped abnormally.
 738 ///
 739 /// In the process of working on rust-lang/rust#55238 a mysterious segfault was
 740 /// stumbled upon. The segfault was never reproduced locally, but it was
 741 /// suspected to be related to the fact that codegen worker threads were
 742 /// sticking around by the time the main thread was exiting, causing issues.
 743 ///
 744 /// This structure is an attempt to fix that issue where the `codegen_aborted`
 745 /// message will block until all workers have finished. This should ensure that
 746 /// even if the main codegen thread panics we'll wait for pending work to
 747 /// complete before returning from the main thread, hopefully avoiding
 748 /// segfaults.
 749 ///
 750 /// If you see this comment in the code, then it means that this workaround
 751 /// worked! We may yet one day track down the mysterious cause of that
 752 /// segfault...
 753 struct AbortCodegenOnDrop<B: ExtraBackendMethods>(Option<OngoingCodegen<B>>);
 754
 755 impl<B: ExtraBackendMethods> AbortCodegenOnDrop<B> {
 756     fn into_inner(mut self) -> OngoingCodegen<B> {
 757         self.0.take().unwrap()
 758     }
 759 }
 760
 761 impl<B: ExtraBackendMethods> Deref for AbortCodegenOnDrop<B> {
 762     type Target = OngoingCodegen<B>;
 763
 764     fn deref(&self) -> &OngoingCodegen<B> {
 765         self.0.as_ref().unwrap()
 766     }
 767 }
 768
 769 impl<B: ExtraBackendMethods> DerefMut for AbortCodegenOnDrop<B> {
 770     fn deref_mut(&mut self) -> &mut OngoingCodegen<B> {
 771         self.0.as_mut().unwrap()
 772     }
 773 }
 774
 775 impl<B: ExtraBackendMethods> Drop for AbortCodegenOnDrop<B> {
 776     fn drop(&mut self) {
 777         if let Some(codegen) = self.0.take() {
 778             codegen.codegen_aborted();
 779         }
 780     }
 781 }
 782
 783 fn finalize_tcx(tcx: TyCtxt<'_>) {
 784     tcx.sess.time("assert_dep_graph", || ::rustc_incremental::assert_dep_graph(tcx));
 785     tcx.sess.time("serialize_dep_graph", || ::rustc_incremental::save_dep_graph(tcx));
 786
 787     // We assume that no queries are run past here. If there are new queries
 788     // after this point, they'll show up as "<unknown>" in self-profiling data.
 789     {
 790         let _prof_timer = tcx.prof.generic_activity("self_profile_alloc_query_strings");
 791         tcx.alloc_self_profile_query_strings();
 792     }
 793 }
 794
 795 impl CrateInfo {
 796     pub fn new(tcx: TyCtxt<'_>) -> CrateInfo {
 797         let mut info = CrateInfo {
 798             panic_runtime: None,
 799             compiler_builtins: None,
 800             profiler_runtime: None,
 801             is_no_builtins: Default::default(),
 802             native_libraries: Default::default(),
 803             used_libraries: tcx.native_libraries(LOCAL_CRATE),
 804             link_args: tcx.link_args(LOCAL_CRATE),
 805             crate_name: Default::default(),
 806             used_crates_dynamic: cstore::used_crates(tcx, LinkagePreference::RequireDynamic),
 807             used_crates_static: cstore::used_crates(tcx, LinkagePreference::RequireStatic),
 808             used_crate_source: Default::default(),
 809             lang_item_to_crate: Default::default(),
 810             missing_lang_items: Default::default(),
 811             dependency_formats: tcx.dependency_formats(LOCAL_CRATE),
 812         };
 813         let lang_items = tcx.lang_items();
 814
 815         let crates = tcx.crates();
 816
 817         let n_crates = crates.len();
 818         info.native_libraries.reserve(n_crates);
 819         info.crate_name.reserve(n_crates);
 820         info.used_crate_source.reserve(n_crates);
 821         info.missing_lang_items.reserve(n_crates);
 822
 823         for &cnum in crates.iter() {
 824             info.native_libraries.insert(cnum, tcx.native_libraries(cnum));
 825             info.crate_name.insert(cnum, tcx.crate_name(cnum).to_string());
 826             info.used_crate_source.insert(cnum, tcx.used_crate_source(cnum));
 827             if tcx.is_panic_runtime(cnum) {
 828                 info.panic_runtime = Some(cnum);
 829             }
 830             if tcx.is_compiler_builtins(cnum) {
 831                 info.compiler_builtins = Some(cnum);
 832             }
 833             if tcx.is_profiler_runtime(cnum) {
 834                 info.profiler_runtime = Some(cnum);
 835             }
 836             if tcx.is_no_builtins(cnum) {
 837                 info.is_no_builtins.insert(cnum);
 838             }
 839             let missing = tcx.missing_lang_items(cnum);
 840             for &item in missing.iter() {
 841                 if let Ok(id) = lang_items.require(item) {
 842                     info.lang_item_to_crate.insert(item, id.krate);
 843                 }
 844             }
 845
 846             // No need to look for lang items that are whitelisted and don't
 847             // actually need to exist.
 848             let missing = missing
 849                 .iter()
 850                 .cloned()
 851                 .filter(|&l| !weak_lang_items::whitelisted(tcx, l))
 852                 .collect();
 853             info.missing_lang_items.insert(cnum, missing);
 854         }
 855
 856         return info;
 857     }
 858 }
 859
 860 pub fn provide_both(providers: &mut Providers<'_>) {
 861     providers.backend_optimization_level = |tcx, cratenum| {
 862         let for_speed = match tcx.sess.opts.optimize {
 863             // If globally no optimisation is done, #[optimize] has no effect.
 864             //
 865             // This is done because if we ended up "upgrading" to `-O2` here, we’d populate the
 866             // pass manager and it is likely that some module-wide passes (such as inliner or
 867             // cross-function constant propagation) would ignore the `optnone` annotation we put
 868             // on the functions, thus necessarily involving these functions into optimisations.
 869             config::OptLevel::No => return config::OptLevel::No,
 870             // If globally optimise-speed is already specified, just use that level.
 871             config::OptLevel::Less => return config::OptLevel::Less,
 872             config::OptLevel::Default => return config::OptLevel::Default,
 873             config::OptLevel::Aggressive => return config::OptLevel::Aggressive,
 874             // If globally optimize-for-size has been requested, use -O2 instead (if optimize(size)
 875             // are present).
 876             config::OptLevel::Size => config::OptLevel::Default,
 877             config::OptLevel::SizeMin => config::OptLevel::Default,
 878         };
 879
 880         let (defids, _) = tcx.collect_and_partition_mono_items(cratenum);
 881         for id in &*defids {
 882             let CodegenFnAttrs { optimize, .. } = tcx.codegen_fn_attrs(*id);
 883             match optimize {
 884                 attr::OptimizeAttr::None => continue,
 885                 attr::OptimizeAttr::Size => continue,
 886                 attr::OptimizeAttr::Speed => {
 887                     return for_speed;
 888                 }
 889             }
 890         }
 891         return tcx.sess.opts.optimize;
 892     };
 893
 894     providers.dllimport_foreign_items = |tcx, krate| {
 895         let module_map = tcx.foreign_modules(krate);
 896         let module_map =
 897             module_map.iter().map(|lib| (lib.def_id, lib)).collect::<FxHashMap<_, _>>();
 898
 899         let dllimports = tcx
 900             .native_libraries(krate)
 901             .iter()
 902             .filter(|lib| {
 903                 if lib.kind != cstore::NativeLibraryKind::NativeUnknown {
 904                     return false;
 905                 }
 906                 let cfg = match lib.cfg {
 907                     Some(ref cfg) => cfg,
 908                     None => return true,
 909                 };
 910                 attr::cfg_matches(cfg, &tcx.sess.parse_sess, None)
 911             })
 912             .filter_map(|lib| lib.foreign_module)
 913             .map(|id| &module_map[&id])
 914             .flat_map(|module| module.foreign_items.iter().cloned())
 915             .collect();
 916         tcx.arena.alloc(dllimports)
 917     };
 918
 919     providers.is_dllimport_foreign_item =
 920         |tcx, def_id| tcx.dllimport_foreign_items(def_id.krate).contains(&def_id);
 921 }
 922
 923 fn determine_cgu_reuse<'tcx>(tcx: TyCtxt<'tcx>, cgu: &CodegenUnit<'tcx>) -> CguReuse {
 924     if !tcx.dep_graph.is_fully_enabled() {
 925         return CguReuse::No;
 926     }
 927
 928     let work_product_id = &cgu.work_product_id();
 929     if tcx.dep_graph.previous_work_product(work_product_id).is_none() {
 930         // We don't have anything cached for this CGU. This can happen
 931         // if the CGU did not exist in the previous session.
 932         return CguReuse::No;
 933     }
 934
 935     // Try to mark the CGU as green. If it we can do so, it means that nothing
 936     // affecting the LLVM module has changed and we can re-use a cached version.
 937     // If we compile with any kind of LTO, this means we can re-use the bitcode
 938     // of the Pre-LTO stage (possibly also the Post-LTO version but we'll only
 939     // know that later). If we are not doing LTO, there is only one optimized
 940     // version of each module, so we re-use that.
 941     let dep_node = cgu.codegen_dep_node(tcx);
 942     assert!(
 943         !tcx.dep_graph.dep_node_exists(&dep_node),
 944         "CompileCodegenUnit dep-node for CGU `{}` already exists before marking.",
 945         cgu.name()
 946     );
 947
 948     if tcx.dep_graph.try_mark_green(tcx, &dep_node).is_some() {
 949         // We can re-use either the pre- or the post-thinlto state
 950         if tcx.sess.lto() != Lto::No { CguReuse::PreLto } else { CguReuse::PostLto }
 951     } else {
 952         CguReuse::No
 953     }
 954 }