src/librustc_codegen_llvm/mir/block.rs

   1 // Copyright 2012-2014 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 use llvm::{self, BasicBlock};
  12 use rustc::middle::lang_items;
  13 use rustc::ty::{self, Ty, TypeFoldable};
  14 use rustc::ty::layout::{self, LayoutOf};
  15 use rustc::mir;
  16 use rustc::mir::interpret::EvalErrorKind;
  17 use abi::{Abi, ArgType, ArgTypeExt, FnType, FnTypeExt, LlvmType, PassMode};
  18 use base;
  19 use callee;
  20 use builder::{Builder, MemFlags};
  21 use common::{self, IntPredicate};
  22 use context::CodegenCx;
  23 use consts;
  24 use meth;
  25 use monomorphize;
  26 use type_of::LayoutLlvmExt;
  27 use type_::Type;
  28 use value::Value;
  29
  30 use interfaces::{BuilderMethods, CommonMethods};
  31
  32 use syntax::symbol::Symbol;
  33 use syntax_pos::Pos;
  34
  35 use super::{FunctionCx, LocalRef};
  36 use super::place::PlaceRef;
  37 use super::operand::OperandRef;
  38 use super::operand::OperandValue::{Pair, Ref, Immediate};
  39
  40 impl FunctionCx<'a, 'll, 'tcx, &'ll Value> {
  41     pub fn codegen_block(&mut self, bb: mir::BasicBlock) {
  42         let mut bx = self.build_block(bb);
  43         let data = &self.mir[bb];
  44
  45         debug!("codegen_block({:?}={:?})", bb, data);
  46
  47         for statement in &data.statements {
  48             bx = self.codegen_statement(bx, statement);
  49         }
  50
  51         self.codegen_terminator(bx, bb, data.terminator());
  52     }
  53
  54     fn codegen_terminator(&mut self,
  55                           mut bx: Builder<'a, 'll, 'tcx>,
  56                           bb: mir::BasicBlock,
  57                           terminator: &mir::Terminator<'tcx>)
  58     {
  59         debug!("codegen_terminator: {:?}", terminator);
  60
  61         // Create the cleanup bundle, if needed.
  62         let tcx = bx.tcx();
  63         let span = terminator.source_info.span;
  64         let funclet_bb = self.cleanup_kinds[bb].funclet_bb(bb);
  65         let funclet = funclet_bb.and_then(|funclet_bb| self.funclets[funclet_bb].as_ref());
  66
  67         let cleanup_pad = funclet.map(|lp| lp.cleanuppad());
  68         let cleanup_bundle = funclet.map(|l| l.bundle());
  69
  70         let lltarget = |this: &mut Self, target: mir::BasicBlock| {
  71             let lltarget = this.blocks[target];
  72             let target_funclet = this.cleanup_kinds[target].funclet_bb(target);
  73             match (funclet_bb, target_funclet) {
  74                 (None, None) => (lltarget, false),
  75                 (Some(f), Some(t_f))
  76                     if f == t_f || !base::wants_msvc_seh(tcx.sess)
  77                     => (lltarget, false),
  78                 (None, Some(_)) => {
  79                     // jump *into* cleanup - need a landing pad if GNU
  80                     (this.landing_pad_to(target), false)
  81                 }
  82                 (Some(_), None) => span_bug!(span, "{:?} - jump out of cleanup?", terminator),
  83                 (Some(_), Some(_)) => {
  84                     (this.landing_pad_to(target), true)
  85                 }
  86             }
  87         };
  88
  89         let llblock = |this: &mut Self, target: mir::BasicBlock| {
  90             let (lltarget, is_cleanupret) = lltarget(this, target);
  91             if is_cleanupret {
  92                 // MSVC cross-funclet jump - need a trampoline
  93
  94                 debug!("llblock: creating cleanup trampoline for {:?}", target);
  95                 let name = &format!("{:?}_cleanup_trampoline_{:?}", bb, target);
  96                 let trampoline = this.new_block(name);
  97                 trampoline.cleanup_ret(cleanup_pad.unwrap(), Some(lltarget));
  98                 trampoline.llbb()
  99             } else {
 100                 lltarget
 101             }
 102         };
 103
 104         let funclet_br =
 105             |this: &mut Self, bx: Builder<'_, 'll, '_>, target: mir::BasicBlock| {
 106                 let (lltarget, is_cleanupret) = lltarget(this, target);
 107                 if is_cleanupret {
 108                     // micro-optimization: generate a `ret` rather than a jump
 109                     // to a trampoline.
 110                     bx.cleanup_ret(cleanup_pad.unwrap(), Some(lltarget));
 111                 } else {
 112                     bx.br(lltarget);
 113                 }
 114             };
 115
 116         let do_call = |
 117             this: &mut Self,
 118             bx: Builder<'a, 'll, 'tcx>,
 119             fn_ty: FnType<'tcx, Ty<'tcx>>,
 120             fn_ptr: &'ll Value,
 121             llargs: &[&'ll Value],
 122             destination: Option<(ReturnDest<'tcx, &'ll Value>, mir::BasicBlock)>,
 123             cleanup: Option<mir::BasicBlock>
 124         | {
 125             if let Some(cleanup) = cleanup {
 126                 let ret_bx = if let Some((_, target)) = destination {
 127                     this.blocks[target]
 128                 } else {
 129                     this.unreachable_block()
 130                 };
 131                 let invokeret = bx.invoke(fn_ptr,
 132                                           &llargs,
 133                                           ret_bx,
 134                                           llblock(this, cleanup),
 135                                           cleanup_bundle);
 136                 fn_ty.apply_attrs_callsite(&bx, invokeret);
 137
 138                 if let Some((ret_dest, target)) = destination {
 139                     let ret_bx = this.build_block(target);
 140                     this.set_debug_loc(&ret_bx, terminator.source_info);
 141                     this.store_return(&ret_bx, ret_dest, &fn_ty.ret, invokeret);
 142                 }
 143             } else {
 144                 let llret = bx.call(fn_ptr, &llargs, cleanup_bundle);
 145                 fn_ty.apply_attrs_callsite(&bx, llret);
 146                 if this.mir[bb].is_cleanup {
 147                     // Cleanup is always the cold path. Don't inline
 148                     // drop glue. Also, when there is a deeply-nested
 149                     // struct, there are "symmetry" issues that cause
 150                     // exponential inlining - see issue #41696.
 151                     llvm::Attribute::NoInline.apply_callsite(llvm::AttributePlace::Function, llret);
 152                 }
 153
 154                 if let Some((ret_dest, target)) = destination {
 155                     this.store_return(&bx, ret_dest, &fn_ty.ret, llret);
 156                     funclet_br(this, bx, target);
 157                 } else {
 158                     bx.unreachable();
 159                 }
 160             }
 161         };
 162
 163         self.set_debug_loc(&bx, terminator.source_info);
 164         match terminator.kind {
 165             mir::TerminatorKind::Resume => {
 166                 if let Some(cleanup_pad) = cleanup_pad {
 167                     bx.cleanup_ret(cleanup_pad, None);
 168                 } else {
 169                     let slot = self.get_personality_slot(&bx);
 170                     let lp0 = slot.project_field(&bx, 0).load(&bx).immediate();
 171                     let lp1 = slot.project_field(&bx, 1).load(&bx).immediate();
 172                     slot.storage_dead(&bx);
 173
 174                     if !bx.sess().target.target.options.custom_unwind_resume {
 175                         let mut lp = bx.cx().c_undef(self.landing_pad_type());
 176                         lp = bx.insert_value(lp, lp0, 0);
 177                         lp = bx.insert_value(lp, lp1, 1);
 178                         bx.resume(lp);
 179                     } else {
 180                         bx.call(bx.cx().eh_unwind_resume(), &[lp0], cleanup_bundle);
 181                         bx.unreachable();
 182                     }
 183                 }
 184             }
 185
 186             mir::TerminatorKind::Abort => {
 187                 // Call core::intrinsics::abort()
 188                 let fnname = bx.cx().get_intrinsic(&("llvm.trap"));
 189                 bx.call(fnname, &[], None);
 190                 bx.unreachable();
 191             }
 192
 193             mir::TerminatorKind::Goto { target } => {
 194                 funclet_br(self, bx, target);
 195             }
 196
 197             mir::TerminatorKind::SwitchInt { ref discr, switch_ty, ref values, ref targets } => {
 198                 let discr = self.codegen_operand(&bx, discr);
 199                 if targets.len() == 2 {
 200                     // If there are two targets, emit br instead of switch
 201                     let lltrue = llblock(self, targets[0]);
 202                     let llfalse = llblock(self, targets[1]);
 203                     if switch_ty == bx.tcx().types.bool {
 204                         // Don't generate trivial icmps when switching on bool
 205                         if let [0] = values[..] {
 206                             bx.cond_br(discr.immediate(), llfalse, lltrue);
 207                         } else {
 208                             assert_eq!(&values[..], &[1]);
 209                             bx.cond_br(discr.immediate(), lltrue, llfalse);
 210                         }
 211                     } else {
 212                         let switch_llty = bx.cx().layout_of(switch_ty).immediate_llvm_type(bx.cx());
 213                         let llval = bx.cx().c_uint_big(switch_llty, values[0]);
 214                         let cmp = bx.icmp(IntPredicate::IntEQ, discr.immediate(), llval);
 215                         bx.cond_br(cmp, lltrue, llfalse);
 216                     }
 217                 } else {
 218                     let (otherwise, targets) = targets.split_last().unwrap();
 219                     let switch = bx.switch(discr.immediate(),
 220                                            llblock(self, *otherwise),
 221                                            values.len());
 222                     let switch_llty = bx.cx().layout_of(switch_ty).immediate_llvm_type(bx.cx());
 223                     for (&value, target) in values.iter().zip(targets) {
 224                         let llval =bx.cx().c_uint_big(switch_llty, value);
 225                         let llbb = llblock(self, *target);
 226                         bx.add_case(switch, llval, llbb)
 227                     }
 228                 }
 229             }
 230
 231             mir::TerminatorKind::Return => {
 232                 let llval = match self.fn_ty.ret.mode {
 233                     PassMode::Ignore | PassMode::Indirect(..) => {
 234                         bx.ret_void();
 235                         return;
 236                     }
 237
 238                     PassMode::Direct(_) | PassMode::Pair(..) => {
 239                         let op = self.codegen_consume(&bx, &mir::Place::Local(mir::RETURN_PLACE));
 240                         if let Ref(llval, _, align) = op.val {
 241                             bx.load(llval, align)
 242                         } else {
 243                             op.immediate_or_packed_pair(&bx)
 244                         }
 245                     }
 246
 247                     PassMode::Cast(cast_ty) => {
 248                         let op = match self.locals[mir::RETURN_PLACE] {
 249                             LocalRef::Operand(Some(op)) => op,
 250                             LocalRef::Operand(None) => bug!("use of return before def"),
 251                             LocalRef::Place(cg_place) => {
 252                                 OperandRef {
 253                                     val: Ref(cg_place.llval, None, cg_place.align),
 254                                     layout: cg_place.layout
 255                                 }
 256                             }
 257                             LocalRef::UnsizedPlace(_) => bug!("return type must be sized"),
 258                         };
 259                         let llslot = match op.val {
 260                             Immediate(_) | Pair(..) => {
 261                                 let scratch = PlaceRef::alloca(&bx, self.fn_ty.ret.layout, "ret");
 262                                 op.val.store(&bx, scratch);
 263                                 scratch.llval
 264                             }
 265                             Ref(llval, _, align) => {
 266                                 assert_eq!(align.abi(), op.layout.align.abi(),
 267                                            "return place is unaligned!");
 268                                 llval
 269                             }
 270                         };
 271                         bx.load(
 272                             bx.pointercast(llslot, cast_ty.llvm_type(bx.cx()).ptr_to()),
 273                             self.fn_ty.ret.layout.align)
 274                     }
 275                 };
 276                 bx.ret(llval);
 277             }
 278
 279             mir::TerminatorKind::Unreachable => {
 280                 bx.unreachable();
 281             }
 282
 283             mir::TerminatorKind::Drop { ref location, target, unwind } => {
 284                 let ty = location.ty(self.mir, bx.tcx()).to_ty(bx.tcx());
 285                 let ty = self.monomorphize(&ty);
 286                 let drop_fn = monomorphize::resolve_drop_in_place(bx.cx().tcx, ty);
 287
 288                 if let ty::InstanceDef::DropGlue(_, None) = drop_fn.def {
 289                     // we don't actually need to drop anything.
 290                     funclet_br(self, bx, target);
 291                     return
 292                 }
 293
 294                 let place = self.codegen_place(&bx, location);
 295                 let (args1, args2);
 296                 let mut args = if let Some(llextra) = place.llextra {
 297                     args2 = [place.llval, llextra];
 298                     &args2[..]
 299                 } else {
 300                     args1 = [place.llval];
 301                     &args1[..]
 302                 };
 303                 let (drop_fn, fn_ty) = match ty.sty {
 304                     ty::Dynamic(..) => {
 305                         let sig = drop_fn.fn_sig(bx.tcx());
 306                         let sig = bx.tcx().normalize_erasing_late_bound_regions(
 307                             ty::ParamEnv::reveal_all(),
 308                             &sig,
 309                         );
 310                         let fn_ty = FnType::new_vtable(bx.cx(), sig, &[]);
 311                         let vtable = args[1];
 312                         args = &args[..1];
 313                         (meth::DESTRUCTOR.get_fn(&bx, vtable, &fn_ty), fn_ty)
 314                     }
 315                     _ => {
 316                         (callee::get_fn(bx.cx(), drop_fn),
 317                          FnType::of_instance(bx.cx(), &drop_fn))
 318                     }
 319                 };
 320                 do_call(self, bx, fn_ty, drop_fn, args,
 321                         Some((ReturnDest::Nothing, target)),
 322                         unwind);
 323             }
 324
 325             mir::TerminatorKind::Assert { ref cond, expected, ref msg, target, cleanup } => {
 326                 let cond = self.codegen_operand(&bx, cond).immediate();
 327                 let mut const_cond = CodegenCx::const_to_opt_u128(cond, false).map(|c| c == 1);
 328
 329                 // This case can currently arise only from functions marked
 330                 // with #[rustc_inherit_overflow_checks] and inlined from
 331                 // another crate (mostly core::num generic/#[inline] fns),
 332                 // while the current crate doesn't use overflow checks.
 333                 // NOTE: Unlike binops, negation doesn't have its own
 334                 // checked operation, just a comparison with the minimum
 335                 // value, so we have to check for the assert message.
 336                 if !bx.cx().check_overflow {
 337                     if let mir::interpret::EvalErrorKind::OverflowNeg = *msg {
 338                         const_cond = Some(expected);
 339                     }
 340                 }
 341
 342                 // Don't codegen the panic block if success if known.
 343                 if const_cond == Some(expected) {
 344                     funclet_br(self, bx, target);
 345                     return;
 346                 }
 347
 348                 // Pass the condition through llvm.expect for branch hinting.
 349                 let expect = bx.cx().get_intrinsic(&"llvm.expect.i1");
 350                 let cond = bx.call(expect, &[cond, CodegenCx::c_bool(bx.cx(), expected)], None);
 351
 352                 // Create the failure block and the conditional branch to it.
 353                 let lltarget = llblock(self, target);
 354                 let panic_block = self.new_block("panic");
 355                 if expected {
 356                     bx.cond_br(cond, lltarget, panic_block.llbb());
 357                 } else {
 358                     bx.cond_br(cond, panic_block.llbb(), lltarget);
 359                 }
 360
 361                 // After this point, bx is the block for the call to panic.
 362                 bx = panic_block;
 363                 self.set_debug_loc(&bx, terminator.source_info);
 364
 365                 // Get the location information.
 366                 let loc = bx.sess().source_map().lookup_char_pos(span.lo());
 367                 let filename = Symbol::intern(&loc.file.name.to_string()).as_str();
 368                 let filename = CodegenCx::c_str_slice(bx.cx(), filename);
 369                 let line = CodegenCx::c_u32(bx.cx(), loc.line as u32);
 370                 let col = CodegenCx::c_u32(bx.cx(), loc.col.to_usize() as u32 + 1);
 371                 let align = tcx.data_layout.aggregate_align
 372                     .max(tcx.data_layout.i32_align)
 373                     .max(tcx.data_layout.pointer_align);
 374
 375                 // Put together the arguments to the panic entry point.
 376                 let (lang_item, args) = match *msg {
 377                     EvalErrorKind::BoundsCheck { ref len, ref index } => {
 378                         let len = self.codegen_operand(&mut bx, len).immediate();
 379                         let index = self.codegen_operand(&mut bx, index).immediate();
 380
 381                         let file_line_col = CodegenCx::c_struct(bx.cx(),
 382                              &[filename, line, col], false);
 383                         let file_line_col = consts::addr_of(bx.cx(),
 384                                                             file_line_col,
 385                                                             align,
 386                                                             Some("panic_bounds_check_loc"));
 387                         (lang_items::PanicBoundsCheckFnLangItem,
 388                          vec![file_line_col, index, len])
 389                     }
 390                     _ => {
 391                         let str = msg.description();
 392                         let msg_str = Symbol::intern(str).as_str();
 393                         let msg_str = CodegenCx::c_str_slice(bx.cx(), msg_str);
 394                         let msg_file_line_col = CodegenCx::c_struct(
 395                             bx.cx(),
 396                             &[msg_str, filename, line, col],
 397                             false
 398                         );
 399                         let msg_file_line_col = consts::addr_of(bx.cx(),
 400                                                                 msg_file_line_col,
 401                                                                 align,
 402                                                                 Some("panic_loc"));
 403                         (lang_items::PanicFnLangItem,
 404                          vec![msg_file_line_col])
 405                     }
 406                 };
 407
 408                 // Obtain the panic entry point.
 409                 let def_id = common::langcall(bx.tcx(), Some(span), "", lang_item);
 410                 let instance = ty::Instance::mono(bx.tcx(), def_id);
 411                 let fn_ty = FnType::of_instance(bx.cx(), &instance);
 412                 let llfn = callee::get_fn(bx.cx(), instance);
 413
 414                 // Codegen the actual panic invoke/call.
 415                 do_call(self, bx, fn_ty, llfn, &args, None, cleanup);
 416             }
 417
 418             mir::TerminatorKind::DropAndReplace { .. } => {
 419                 bug!("undesugared DropAndReplace in codegen: {:?}", terminator);
 420             }
 421
 422             mir::TerminatorKind::Call {
 423                 ref func,
 424                 ref args,
 425                 ref destination,
 426                 cleanup,
 427                 from_hir_call: _
 428             } => {
 429                 // Create the callee. This is a fn ptr or zero-sized and hence a kind of scalar.
 430                 let callee = self.codegen_operand(&bx, func);
 431
 432                 let (instance, mut llfn) = match callee.layout.ty.sty {
 433                     ty::FnDef(def_id, substs) => {
 434                         (Some(ty::Instance::resolve(bx.cx().tcx,
 435                                                     ty::ParamEnv::reveal_all(),
 436                                                     def_id,
 437                                                     substs).unwrap()),
 438                          None)
 439                     }
 440                     ty::FnPtr(_) => {
 441                         (None, Some(callee.immediate()))
 442                     }
 443                     _ => bug!("{} is not callable", callee.layout.ty)
 444                 };
 445                 let def = instance.map(|i| i.def);
 446                 let sig = callee.layout.ty.fn_sig(bx.tcx());
 447                 let sig = bx.tcx().normalize_erasing_late_bound_regions(
 448                     ty::ParamEnv::reveal_all(),
 449                     &sig,
 450                 );
 451                 let abi = sig.abi;
 452
 453                 // Handle intrinsics old codegen wants Expr's for, ourselves.
 454                 let intrinsic = match def {
 455                     Some(ty::InstanceDef::Intrinsic(def_id))
 456                         => Some(bx.tcx().item_name(def_id).as_str()),
 457                     _ => None
 458                 };
 459                 let intrinsic = intrinsic.as_ref().map(|s| &s[..]);
 460
 461                 if intrinsic == Some("transmute") {
 462                     if let Some(destination_ref) = destination.as_ref() {
 463                         let &(ref dest, target) = destination_ref;
 464                         self.codegen_transmute(&bx, &args[0], dest);
 465                         funclet_br(self, bx, target);
 466                     } else {
 467                         // If we are trying to transmute to an uninhabited type,
 468                         // it is likely there is no allotted destination. In fact,
 469                         // transmuting to an uninhabited type is UB, which means
 470                         // we can do what we like. Here, we declare that transmuting
 471                         // into an uninhabited type is impossible, so anything following
 472                         // it must be unreachable.
 473                         assert_eq!(bx.cx().layout_of(sig.output()).abi, layout::Abi::Uninhabited);
 474                         bx.unreachable();
 475                     }
 476                     return;
 477                 }
 478
 479                 let extra_args = &args[sig.inputs().len()..];
 480                 let extra_args = extra_args.iter().map(|op_arg| {
 481                     let op_ty = op_arg.ty(self.mir, bx.tcx());
 482                     self.monomorphize(&op_ty)
 483                 }).collect::<Vec<_>>();
 484
 485                 let fn_ty = match def {
 486                     Some(ty::InstanceDef::Virtual(..)) => {
 487                         FnType::new_vtable(bx.cx(), sig, &extra_args)
 488                     }
 489                     Some(ty::InstanceDef::DropGlue(_, None)) => {
 490                         // empty drop glue - a nop.
 491                         let &(_, target) = destination.as_ref().unwrap();
 492                         funclet_br(self, bx, target);
 493                         return;
 494                     }
 495                     _ => FnType::new(bx.cx(), sig, &extra_args)
 496                 };
 497
 498                 // emit a panic instead of instantiating an uninhabited type
 499                 if (intrinsic == Some("init") || intrinsic == Some("uninit")) &&
 500                     fn_ty.ret.layout.abi.is_uninhabited()
 501                 {
 502                     let loc = bx.sess().source_map().lookup_char_pos(span.lo());
 503                     let filename = Symbol::intern(&loc.file.name.to_string()).as_str();
 504                     let filename = bx.cx.c_str_slice(filename);
 505                     let line = bx.cx.c_u32(loc.line as u32);
 506                     let col = bx.cx.c_u32(loc.col.to_usize() as u32 + 1);
 507                     let align = tcx.data_layout.aggregate_align
 508                         .max(tcx.data_layout.i32_align)
 509                         .max(tcx.data_layout.pointer_align);
 510
 511                     let str = format!(
 512                         "Attempted to instantiate uninhabited type {} using mem::{}",
 513                         sig.output(),
 514                         if intrinsic == Some("init") { "zeroed" } else { "uninitialized" }
 515                     );
 516                     let msg_str = Symbol::intern(&str).as_str();
 517                     let msg_str = bx.cx.c_str_slice(msg_str);
 518                     let msg_file_line_col = bx.cx.c_struct(
 519                         &[msg_str, filename, line, col],
 520                         false,
 521                     );
 522                     let msg_file_line_col = consts::addr_of(bx.cx,
 523                                                             msg_file_line_col,
 524                                                             align,
 525                                                             Some("panic_loc"));
 526
 527                     // Obtain the panic entry point.
 528                     let def_id =
 529                         common::langcall(bx.tcx(), Some(span), "", lang_items::PanicFnLangItem);
 530                     let instance = ty::Instance::mono(bx.tcx(), def_id);
 531                     let fn_ty = FnType::of_instance(bx.cx, &instance);
 532                     let llfn = callee::get_fn(bx.cx, instance);
 533
 534                     // Codegen the actual panic invoke/call.
 535                     do_call(
 536                         self,
 537                         bx,
 538                         fn_ty,
 539                         llfn,
 540                         &[msg_file_line_col],
 541                         destination.as_ref().map(|(_, bb)| (ReturnDest::Nothing, *bb)),
 542                         cleanup,
 543                     );
 544                     return;
 545                 }
 546
 547                 // The arguments we'll be passing. Plus one to account for outptr, if used.
 548                 let arg_count = fn_ty.args.len() + fn_ty.ret.is_indirect() as usize;
 549                 let mut llargs = Vec::with_capacity(arg_count);
 550
 551                 // Prepare the return value destination
 552                 let ret_dest = if let Some((ref dest, _)) = *destination {
 553                     let is_intrinsic = intrinsic.is_some();
 554                     self.make_return_dest(&bx, dest, &fn_ty.ret, &mut llargs,
 555                                           is_intrinsic)
 556                 } else {
 557                     ReturnDest::Nothing
 558                 };
 559
 560                 if intrinsic.is_some() && intrinsic != Some("drop_in_place") {
 561                     use intrinsic::codegen_intrinsic_call;
 562
 563                     let dest = match ret_dest {
 564                         _ if fn_ty.ret.is_indirect() => llargs[0],
 565                         ReturnDest::Nothing => {
 566                             bx.cx().c_undef(fn_ty.ret.memory_ty(bx.cx()).ptr_to())
 567                         }
 568                         ReturnDest::IndirectOperand(dst, _) |
 569                         ReturnDest::Store(dst) => dst.llval,
 570                         ReturnDest::DirectOperand(_) =>
 571                             bug!("Cannot use direct operand with an intrinsic call")
 572                     };
 573
 574                     let args: Vec<_> = args.iter().enumerate().map(|(i, arg)| {
 575                         // The indices passed to simd_shuffle* in the
 576                         // third argument must be constant. This is
 577                         // checked by const-qualification, which also
 578                         // promotes any complex rvalues to constants.
 579                         if i == 2 && intrinsic.unwrap().starts_with("simd_shuffle") {
 580                             match *arg {
 581                                 // The shuffle array argument is usually not an explicit constant,
 582                                 // but specified directly in the code. This means it gets promoted
 583                                 // and we can then extract the value by evaluating the promoted.
 584                                 mir::Operand::Copy(mir::Place::Promoted(box(index, ty))) |
 585                                 mir::Operand::Move(mir::Place::Promoted(box(index, ty))) => {
 586                                     let param_env = ty::ParamEnv::reveal_all();
 587                                     let cid = mir::interpret::GlobalId {
 588                                         instance: self.instance,
 589                                         promoted: Some(index),
 590                                     };
 591                                     let c = bx.tcx().const_eval(param_env.and(cid));
 592                                     let (llval, ty) = self.simd_shuffle_indices(
 593                                         &bx,
 594                                         terminator.source_info.span,
 595                                         ty,
 596                                         c,
 597                                     );
 598                                     return OperandRef {
 599                                         val: Immediate(llval),
 600                                         layout: bx.cx().layout_of(ty),
 601                                     };
 602
 603                                 },
 604                                 mir::Operand::Copy(_) |
 605                                 mir::Operand::Move(_) => {
 606                                     span_bug!(span, "shuffle indices must be constant");
 607                                 }
 608                                 mir::Operand::Constant(ref constant) => {
 609                                     let c = self.eval_mir_constant(&bx, constant);
 610                                     let (llval, ty) = self.simd_shuffle_indices(
 611                                         &bx,
 612                                         constant.span,
 613                                         constant.ty,
 614                                         c,
 615                                     );
 616                                     return OperandRef {
 617                                         val: Immediate(llval),
 618                                         layout: bx.cx().layout_of(ty)
 619                                     };
 620                                 }
 621                             }
 622                         }
 623
 624                         self.codegen_operand(&bx, arg)
 625                     }).collect();
 626
 627
 628                     let callee_ty = instance.as_ref().unwrap().ty(bx.cx().tcx);
 629                     codegen_intrinsic_call(&bx, callee_ty, &fn_ty, &args, dest,
 630                                            terminator.source_info.span);
 631
 632                     if let ReturnDest::IndirectOperand(dst, _) = ret_dest {
 633                         self.store_return(&bx, ret_dest, &fn_ty.ret, dst.llval);
 634                     }
 635
 636                     if let Some((_, target)) = *destination {
 637                         funclet_br(self, bx, target);
 638                     } else {
 639                         bx.unreachable();
 640                     }
 641
 642                     return;
 643                 }
 644
 645                 // Split the rust-call tupled arguments off.
 646                 let (first_args, untuple) = if abi == Abi::RustCall && !args.is_empty() {
 647                     let (tup, args) = args.split_last().unwrap();
 648                     (args, Some(tup))
 649                 } else {
 650                     (&args[..], None)
 651                 };
 652
 653                 'make_args: for (i, arg) in first_args.iter().enumerate() {
 654                     let mut op = self.codegen_operand(&bx, arg);
 655
 656                     if let (0, Some(ty::InstanceDef::Virtual(_, idx))) = (i, def) {
 657                         if let Pair(..) = op.val {
 658                             // In the case of Rc<Self>, we need to explicitly pass a
 659                             // *mut RcBox<Self> with a Scalar (not ScalarPair) ABI. This is a hack
 660                             // that is understood elsewhere in the compiler as a method on
 661                             // `dyn Trait`.
 662                             // To get a `*mut RcBox<Self>`, we just keep unwrapping newtypes until
 663                             // we get a value of a built-in pointer type
 664                             'descend_newtypes: while !op.layout.ty.is_unsafe_ptr()
 665                                             && !op.layout.ty.is_region_ptr()
 666                             {
 667                                 'iter_fields: for i in 0..op.layout.fields.count() {
 668                                     let field = op.extract_field(&bx, i);
 669                                     if !field.layout.is_zst() {
 670                                         // we found the one non-zero-sized field that is allowed
 671                                         // now find *its* non-zero-sized field, or stop if it's a
 672                                         // pointer
 673                                         op = field;
 674                                         continue 'descend_newtypes
 675                                     }
 676                                 }
 677
 678                                 span_bug!(span, "receiver has no non-zero-sized fields {:?}", op);
 679                             }
 680
 681                             // now that we have `*dyn Trait` or `&dyn Trait`, split it up into its
 682                             // data pointer and vtable. Look up the method in the vtable, and pass
 683                             // the data pointer as the first argument
 684                             match op.val {
 685                                 Pair(data_ptr, meta) => {
 686                                     llfn = Some(meth::VirtualIndex::from_index(idx)
 687                                         .get_fn(&bx, meta, &fn_ty));
 688                                     llargs.push(data_ptr);
 689                                     continue 'make_args
 690                                 }
 691                                 other => bug!("expected a Pair, got {:?}", other)
 692                             }
 693                         } else if let Ref(data_ptr, Some(meta), _) = op.val {
 694                             // by-value dynamic dispatch
 695                             llfn = Some(meth::VirtualIndex::from_index(idx)
 696                                 .get_fn(&bx, meta, &fn_ty));
 697                             llargs.push(data_ptr);
 698                             continue;
 699                         } else {
 700                             span_bug!(span, "can't codegen a virtual call on {:?}", op);
 701                         }
 702                     }
 703
 704                     // The callee needs to own the argument memory if we pass it
 705                     // by-ref, so make a local copy of non-immediate constants.
 706                     match (arg, op.val) {
 707                         (&mir::Operand::Copy(_), Ref(_, None, _)) |
 708                         (&mir::Operand::Constant(_), Ref(_, None, _)) => {
 709                             let tmp = PlaceRef::alloca(&bx, op.layout, "const");
 710                             op.val.store(&bx, tmp);
 711                             op.val = Ref(tmp.llval, None, tmp.align);
 712                         }
 713                         _ => {}
 714                     }
 715
 716                     self.codegen_argument(&bx, op, &mut llargs, &fn_ty.args[i]);
 717                 }
 718                 if let Some(tup) = untuple {
 719                     self.codegen_arguments_untupled(&bx, tup, &mut llargs,
 720                         &fn_ty.args[first_args.len()..])
 721                 }
 722
 723                 let fn_ptr = match (llfn, instance) {
 724                     (Some(llfn), _) => llfn,
 725                     (None, Some(instance)) => callee::get_fn(bx.cx(), instance),
 726                     _ => span_bug!(span, "no llfn for call"),
 727                 };
 728
 729                 do_call(self, bx, fn_ty, fn_ptr, &llargs,
 730                         destination.as_ref().map(|&(_, target)| (ret_dest, target)),
 731                         cleanup);
 732             }
 733             mir::TerminatorKind::GeneratorDrop |
 734             mir::TerminatorKind::Yield { .. } => bug!("generator ops in codegen"),
 735             mir::TerminatorKind::FalseEdges { .. } |
 736             mir::TerminatorKind::FalseUnwind { .. } => bug!("borrowck false edges in codegen"),
 737         }
 738     }
 739
 740     fn codegen_argument(&mut self,
 741                       bx: &Builder<'a, 'll, 'tcx>,
 742                       op: OperandRef<'tcx, &'ll Value>,
 743                       llargs: &mut Vec<&'ll Value>,
 744                       arg: &ArgType<'tcx, Ty<'tcx>>) {
 745         // Fill padding with undef value, where applicable.
 746         if let Some(ty) = arg.pad {
 747             llargs.push(bx.cx().c_undef(ty.llvm_type(bx.cx())));
 748         }
 749
 750         if arg.is_ignore() {
 751             return;
 752         }
 753
 754         if let PassMode::Pair(..) = arg.mode {
 755             match op.val {
 756                 Pair(a, b) => {
 757                     llargs.push(a);
 758                     llargs.push(b);
 759                     return;
 760                 }
 761                 _ => bug!("codegen_argument: {:?} invalid for pair argument", op)
 762             }
 763         } else if arg.is_unsized_indirect() {
 764             match op.val {
 765                 Ref(a, Some(b), _) => {
 766                     llargs.push(a);
 767                     llargs.push(b);
 768                     return;
 769                 }
 770                 _ => bug!("codegen_argument: {:?} invalid for unsized indirect argument", op)
 771             }
 772         }
 773
 774         // Force by-ref if we have to load through a cast pointer.
 775         let (mut llval, align, by_ref) = match op.val {
 776             Immediate(_) | Pair(..) => {
 777                 match arg.mode {
 778                     PassMode::Indirect(..) | PassMode::Cast(_) => {
 779                         let scratch = PlaceRef::alloca(bx, arg.layout, "arg");
 780                         op.val.store(bx, scratch);
 781                         (scratch.llval, scratch.align, true)
 782                     }
 783                     _ => {
 784                         (op.immediate_or_packed_pair(bx), arg.layout.align, false)
 785                     }
 786                 }
 787             }
 788             Ref(llval, _, align) => {
 789                 if arg.is_indirect() && align.abi() < arg.layout.align.abi() {
 790                     // `foo(packed.large_field)`. We can't pass the (unaligned) field directly. I
 791                     // think that ATM (Rust 1.16) we only pass temporaries, but we shouldn't
 792                     // have scary latent bugs around.
 793
 794                     let scratch = PlaceRef::alloca(bx, arg.layout, "arg");
 795                     base::memcpy_ty(bx, scratch.llval, scratch.align, llval, align,
 796                                     op.layout, MemFlags::empty());
 797                     (scratch.llval, scratch.align, true)
 798                 } else {
 799                     (llval, align, true)
 800                 }
 801             }
 802         };
 803
 804         if by_ref && !arg.is_indirect() {
 805             // Have to load the argument, maybe while casting it.
 806             if let PassMode::Cast(ty) = arg.mode {
 807                 llval = bx.load(bx.pointercast(llval, ty.llvm_type(bx.cx()).ptr_to()),
 808                                 align.min(arg.layout.align));
 809             } else {
 810                 // We can't use `PlaceRef::load` here because the argument
 811                 // may have a type we don't treat as immediate, but the ABI
 812                 // used for this call is passing it by-value. In that case,
 813                 // the load would just produce `OperandValue::Ref` instead
 814                 // of the `OperandValue::Immediate` we need for the call.
 815                 llval = bx.load(llval, align);
 816                 if let layout::Abi::Scalar(ref scalar) = arg.layout.abi {
 817                     if scalar.is_bool() {
 818                         bx.range_metadata(llval, 0..2);
 819                     }
 820                 }
 821                 // We store bools as i8 so we need to truncate to i1.
 822                 llval = base::to_immediate(bx, llval, arg.layout);
 823             }
 824         }
 825
 826         llargs.push(llval);
 827     }
 828
 829     fn codegen_arguments_untupled(&mut self,
 830                                   bx: &Builder<'a, 'll, 'tcx>,
 831                                   operand: &mir::Operand<'tcx>,
 832                                   llargs: &mut Vec<&'ll Value>,
 833                                   args: &[ArgType<'tcx, Ty<'tcx>>]) {
 834         let tuple = self.codegen_operand(bx, operand);
 835
 836         // Handle both by-ref and immediate tuples.
 837         if let Ref(llval, None, align) = tuple.val {
 838             let tuple_ptr = PlaceRef::new_sized(llval, tuple.layout, align);
 839             for i in 0..tuple.layout.fields.count() {
 840                 let field_ptr = tuple_ptr.project_field(bx, i);
 841                 self.codegen_argument(bx, field_ptr.load(bx), llargs, &args[i]);
 842             }
 843         } else if let Ref(_, Some(_), _) = tuple.val {
 844             bug!("closure arguments must be sized")
 845         } else {
 846             // If the tuple is immediate, the elements are as well.
 847             for i in 0..tuple.layout.fields.count() {
 848                 let op = tuple.extract_field(bx, i);
 849                 self.codegen_argument(bx, op, llargs, &args[i]);
 850             }
 851         }
 852     }
 853
 854     fn get_personality_slot(
 855         &mut self,
 856         bx: &Builder<'a, 'll, 'tcx>
 857     ) -> PlaceRef<'tcx, &'ll Value> {
 858         let cx = bx.cx();
 859         if let Some(slot) = self.personality_slot {
 860             slot
 861         } else {
 862             let layout = cx.layout_of(cx.tcx.intern_tup(&[
 863                 cx.tcx.mk_mut_ptr(cx.tcx.types.u8),
 864                 cx.tcx.types.i32
 865             ]));
 866             let slot = PlaceRef::alloca(bx, layout, "personalityslot");
 867             self.personality_slot = Some(slot);
 868             slot
 869         }
 870     }
 871
 872     /// Return the landingpad wrapper around the given basic block
 873     ///
 874     /// No-op in MSVC SEH scheme.
 875     fn landing_pad_to(&mut self, target_bb: mir::BasicBlock) -> &'ll BasicBlock {
 876         if let Some(block) = self.landing_pads[target_bb] {
 877             return block;
 878         }
 879
 880         let block = self.blocks[target_bb];
 881         let landing_pad = self.landing_pad_uncached(block);
 882         self.landing_pads[target_bb] = Some(landing_pad);
 883         landing_pad
 884     }
 885
 886     fn landing_pad_uncached(&mut self, target_bb: &'ll BasicBlock) -> &'ll BasicBlock {
 887         if base::wants_msvc_seh(self.cx.sess()) {
 888             span_bug!(self.mir.span, "landing pad was not inserted?")
 889         }
 890
 891         let bx = self.new_block("cleanup");
 892
 893         let llpersonality = self.cx.eh_personality();
 894         let llretty = self.landing_pad_type();
 895         let lp = bx.landing_pad(llretty, llpersonality, 1);
 896         bx.set_cleanup(lp);
 897
 898         let slot = self.get_personality_slot(&bx);
 899         slot.storage_live(&bx);
 900         Pair(bx.extract_value(lp, 0), bx.extract_value(lp, 1)).store(&bx, slot);
 901
 902         bx.br(target_bb);
 903         bx.llbb()
 904     }
 905
 906     fn landing_pad_type(&self) -> &'ll Type {
 907         let cx = self.cx;
 908         Type::struct_(cx, &[Type::i8p(cx), Type::i32(cx)], false)
 909     }
 910
 911     fn unreachable_block(&mut self) -> &'ll BasicBlock {
 912         self.unreachable_block.unwrap_or_else(|| {
 913             let bl = self.new_block("unreachable");
 914             bl.unreachable();
 915             self.unreachable_block = Some(bl.llbb());
 916             bl.llbb()
 917         })
 918     }
 919
 920     pub fn new_block(&self, name: &str) -> Builder<'a, 'll, 'tcx> {
 921         Builder::new_block(self.cx, self.llfn, name)
 922     }
 923
 924     pub fn build_block(&self, bb: mir::BasicBlock) -> Builder<'a, 'll, 'tcx> {
 925         let bx = Builder::with_cx(self.cx);
 926         bx.position_at_end(self.blocks[bb]);
 927         bx
 928     }
 929
 930     fn make_return_dest(&mut self, bx: &Builder<'a, 'll, 'tcx>,
 931                         dest: &mir::Place<'tcx>, fn_ret: &ArgType<'tcx, Ty<'tcx>>,
 932                         llargs: &mut Vec<&'ll Value>, is_intrinsic: bool)
 933                         -> ReturnDest<'tcx, &'ll Value> {
 934         // If the return is ignored, we can just return a do-nothing ReturnDest
 935         if fn_ret.is_ignore() {
 936             return ReturnDest::Nothing;
 937         }
 938         let dest = if let mir::Place::Local(index) = *dest {
 939             match self.locals[index] {
 940                 LocalRef::Place(dest) => dest,
 941                 LocalRef::UnsizedPlace(_) => bug!("return type must be sized"),
 942                 LocalRef::Operand(None) => {
 943                     // Handle temporary places, specifically Operand ones, as
 944                     // they don't have allocas
 945                     return if fn_ret.is_indirect() {
 946                         // Odd, but possible, case, we have an operand temporary,
 947                         // but the calling convention has an indirect return.
 948                         let tmp = PlaceRef::alloca(bx, fn_ret.layout, "tmp_ret");
 949                         tmp.storage_live(bx);
 950                         llargs.push(tmp.llval);
 951                         ReturnDest::IndirectOperand(tmp, index)
 952                     } else if is_intrinsic {
 953                         // Currently, intrinsics always need a location to store
 954                         // the result. so we create a temporary alloca for the
 955                         // result
 956                         let tmp = PlaceRef::alloca(bx, fn_ret.layout, "tmp_ret");
 957                         tmp.storage_live(bx);
 958                         ReturnDest::IndirectOperand(tmp, index)
 959                     } else {
 960                         ReturnDest::DirectOperand(index)
 961                     };
 962                 }
 963                 LocalRef::Operand(Some(_)) => {
 964                     bug!("place local already assigned to");
 965                 }
 966             }
 967         } else {
 968             self.codegen_place(bx, dest)
 969         };
 970         if fn_ret.is_indirect() {
 971             if dest.align.abi() < dest.layout.align.abi() {
 972                 // Currently, MIR code generation does not create calls
 973                 // that store directly to fields of packed structs (in
 974                 // fact, the calls it creates write only to temps),
 975                 //
 976                 // If someone changes that, please update this code path
 977                 // to create a temporary.
 978                 span_bug!(self.mir.span, "can't directly store to unaligned value");
 979             }
 980             llargs.push(dest.llval);
 981             ReturnDest::Nothing
 982         } else {
 983             ReturnDest::Store(dest)
 984         }
 985     }
 986
 987     fn codegen_transmute(&mut self, bx: &Builder<'a, 'll, 'tcx>,
 988                          src: &mir::Operand<'tcx>,
 989                          dst: &mir::Place<'tcx>) {
 990         if let mir::Place::Local(index) = *dst {
 991             match self.locals[index] {
 992                 LocalRef::Place(place) => self.codegen_transmute_into(bx, src, place),
 993                 LocalRef::UnsizedPlace(_) => bug!("transmute must not involve unsized locals"),
 994                 LocalRef::Operand(None) => {
 995                     let dst_layout = bx.cx().layout_of(self.monomorphized_place_ty(dst));
 996                     assert!(!dst_layout.ty.has_erasable_regions());
 997                     let place = PlaceRef::alloca(bx, dst_layout, "transmute_temp");
 998                     place.storage_live(bx);
 999                     self.codegen_transmute_into(bx, src, place);
1000                     let op = place.load(bx);
1001                     place.storage_dead(bx);
1002                     self.locals[index] = LocalRef::Operand(Some(op));
1003                 }
1004                 LocalRef::Operand(Some(op)) => {
1005                     assert!(op.layout.is_zst(),
1006                             "assigning to initialized SSAtemp");
1007                 }
1008             }
1009         } else {
1010             let dst = self.codegen_place(bx, dst);
1011             self.codegen_transmute_into(bx, src, dst);
1012         }
1013     }
1014
1015     fn codegen_transmute_into(&mut self, bx: &Builder<'a, 'll, 'tcx>,
1016                               src: &mir::Operand<'tcx>,
1017                               dst: PlaceRef<'tcx, &'ll Value>) {
1018         let src = self.codegen_operand(bx, src);
1019         let llty = src.layout.llvm_type(bx.cx());
1020         let cast_ptr = bx.pointercast(dst.llval, llty.ptr_to());
1021         let align = src.layout.align.min(dst.layout.align);
1022         src.val.store(bx, PlaceRef::new_sized(cast_ptr, src.layout, align));
1023     }
1024
1025
1026     // Stores the return value of a function call into it's final location.
1027     fn store_return(&mut self,
1028                     bx: &Builder<'a, 'll, 'tcx>,
1029                     dest: ReturnDest<'tcx, &'ll Value>,
1030                     ret_ty: &ArgType<'tcx, Ty<'tcx>>,
1031                     llval: &'ll Value) {
1032         use self::ReturnDest::*;
1033
1034         match dest {
1035             Nothing => (),
1036             Store(dst) => ret_ty.store(bx, llval, dst),
1037             IndirectOperand(tmp, index) => {
1038                 let op = tmp.load(bx);
1039                 tmp.storage_dead(bx);
1040                 self.locals[index] = LocalRef::Operand(Some(op));
1041             }
1042             DirectOperand(index) => {
1043                 // If there is a cast, we have to store and reload.
1044                 let op = if let PassMode::Cast(_) = ret_ty.mode {
1045                     let tmp = PlaceRef::alloca(bx, ret_ty.layout, "tmp_ret");
1046                     tmp.storage_live(bx);
1047                     ret_ty.store(bx, llval, tmp);
1048                     let op = tmp.load(bx);
1049                     tmp.storage_dead(bx);
1050                     op
1051                 } else {
1052                     OperandRef::from_immediate_or_packed_pair(bx, llval, ret_ty.layout)
1053                 };
1054                 self.locals[index] = LocalRef::Operand(Some(op));
1055             }
1056         }
1057     }
1058 }
1059
1060 enum ReturnDest<'tcx, V> {
1061     // Do nothing, the return value is indirect or ignored
1062     Nothing,
1063     // Store the return value to the pointer
1064     Store(PlaceRef<'tcx, V>),
1065     // Stores an indirect return value to an operand local place
1066     IndirectOperand(PlaceRef<'tcx, V>, mir::Local),
1067     // Stores a direct return value to an operand local place
1068     DirectOperand(mir::Local)
1069 }