src/librustc_codegen_ssa/mir/block.rs

   1 use rustc::middle::lang_items;
   2 use rustc::ty::{self, Ty, TypeFoldable, Instance};
   3 use rustc::ty::layout::{self, LayoutOf, HasTyCtxt, FnTypeExt};
   4 use rustc::mir::{self, Place, PlaceBase, Static, StaticKind};
   5 use rustc::mir::interpret::PanicInfo;
   6 use rustc_target::abi::call::{ArgType, FnType, PassMode, IgnoreMode};
   7 use rustc_target::spec::abi::Abi;
   8 use crate::base;
   9 use crate::MemFlags;
  10 use crate::common::{self, IntPredicate};
  11 use crate::meth;
  12
  13 use crate::traits::*;
  14
  15 use std::borrow::Cow;
  16
  17 use syntax::symbol::LocalInternedString;
  18 use syntax_pos::Pos;
  19
  20 use super::{FunctionCx, LocalRef};
  21 use super::place::PlaceRef;
  22 use super::operand::OperandRef;
  23 use super::operand::OperandValue::{Pair, Ref, Immediate};
  24
  25 /// Used by `FunctionCx::codegen_terminator` for emitting common patterns
  26 /// e.g., creating a basic block, calling a function, etc.
  27 struct TerminatorCodegenHelper<'a, 'tcx> {
  28     bb: &'a mir::BasicBlock,
  29     terminator: &'a mir::Terminator<'tcx>,
  30     funclet_bb: Option<mir::BasicBlock>,
  31 }
  32
  33 impl<'a, 'tcx> TerminatorCodegenHelper<'a, 'tcx> {
  34     /// Returns the associated funclet from `FunctionCx::funclets` for the
  35     /// `funclet_bb` member if it is not `None`.
  36     fn funclet<'c, 'b, Bx: BuilderMethods<'b, 'tcx>>(
  37         &self,
  38         fx: &'c mut FunctionCx<'b, 'tcx, Bx>,
  39     ) -> Option<&'c Bx::Funclet> {
  40         match self.funclet_bb {
  41             Some(funcl) => fx.funclets[funcl].as_ref(),
  42             None => None,
  43         }
  44     }
  45
  46     fn lltarget<'b, 'c, Bx: BuilderMethods<'b, 'tcx>>(
  47         &self,
  48         fx: &'c mut FunctionCx<'b, 'tcx, Bx>,
  49         target: mir::BasicBlock,
  50     ) -> (Bx::BasicBlock, bool) {
  51         let span = self.terminator.source_info.span;
  52         let lltarget = fx.blocks[target];
  53         let target_funclet = fx.cleanup_kinds[target].funclet_bb(target);
  54         match (self.funclet_bb, target_funclet) {
  55             (None, None) => (lltarget, false),
  56             (Some(f), Some(t_f)) if f == t_f || !base::wants_msvc_seh(fx.cx.tcx().sess) =>
  57                 (lltarget, false),
  58             // jump *into* cleanup - need a landing pad if GNU
  59             (None, Some(_)) => (fx.landing_pad_to(target), false),
  60             (Some(_), None) => span_bug!(span, "{:?} - jump out of cleanup?", self.terminator),
  61             (Some(_), Some(_)) => (fx.landing_pad_to(target), true),
  62         }
  63     }
  64
  65     /// Create a basic block.
  66     fn llblock<'c, 'b, Bx: BuilderMethods<'b, 'tcx>>(
  67         &self,
  68         fx: &'c mut FunctionCx<'b, 'tcx, Bx>,
  69         target: mir::BasicBlock,
  70     ) -> Bx::BasicBlock {
  71         let (lltarget, is_cleanupret) = self.lltarget(fx, target);
  72         if is_cleanupret {
  73             // MSVC cross-funclet jump - need a trampoline
  74
  75             debug!("llblock: creating cleanup trampoline for {:?}", target);
  76             let name = &format!("{:?}_cleanup_trampoline_{:?}", self.bb, target);
  77             let mut trampoline = fx.new_block(name);
  78             trampoline.cleanup_ret(self.funclet(fx).unwrap(),
  79                                    Some(lltarget));
  80             trampoline.llbb()
  81         } else {
  82             lltarget
  83         }
  84     }
  85
  86     fn funclet_br<'c, 'b, Bx: BuilderMethods<'b, 'tcx>>(
  87         &self,
  88         fx: &'c mut FunctionCx<'b, 'tcx, Bx>,
  89         bx: &mut Bx,
  90         target: mir::BasicBlock,
  91     ) {
  92         let (lltarget, is_cleanupret) = self.lltarget(fx, target);
  93         if is_cleanupret {
  94             // micro-optimization: generate a `ret` rather than a jump
  95             // to a trampoline.
  96             bx.cleanup_ret(self.funclet(fx).unwrap(), Some(lltarget));
  97         } else {
  98             bx.br(lltarget);
  99         }
 100     }
 101
 102     /// Call `fn_ptr` of `fn_ty` with the arguments `llargs`, the optional
 103     /// return destination `destination` and the cleanup function `cleanup`.
 104     fn do_call<'c, 'b, Bx: BuilderMethods<'b, 'tcx>>(
 105         &self,
 106         fx: &'c mut FunctionCx<'b, 'tcx, Bx>,
 107         bx: &mut Bx,
 108         fn_ty: FnType<'tcx, Ty<'tcx>>,
 109         fn_ptr: Bx::Value,
 110         llargs: &[Bx::Value],
 111         destination: Option<(ReturnDest<'tcx, Bx::Value>, mir::BasicBlock)>,
 112         cleanup: Option<mir::BasicBlock>,
 113     ) {
 114         if let Some(cleanup) = cleanup {
 115             let ret_bx = if let Some((_, target)) = destination {
 116                 fx.blocks[target]
 117             } else {
 118                 fx.unreachable_block()
 119             };
 120             let invokeret = bx.invoke(fn_ptr,
 121                                       &llargs,
 122                                       ret_bx,
 123                                       self.llblock(fx, cleanup),
 124                                       self.funclet(fx));
 125             bx.apply_attrs_callsite(&fn_ty, invokeret);
 126
 127             if let Some((ret_dest, target)) = destination {
 128                 let mut ret_bx = fx.build_block(target);
 129                 fx.set_debug_loc(&mut ret_bx, self.terminator.source_info);
 130                 fx.store_return(&mut ret_bx, ret_dest, &fn_ty.ret, invokeret);
 131             }
 132         } else {
 133             let llret = bx.call(fn_ptr, &llargs, self.funclet(fx));
 134             bx.apply_attrs_callsite(&fn_ty, llret);
 135             if fx.mir[*self.bb].is_cleanup {
 136                 // Cleanup is always the cold path. Don't inline
 137                 // drop glue. Also, when there is a deeply-nested
 138                 // struct, there are "symmetry" issues that cause
 139                 // exponential inlining - see issue #41696.
 140                 bx.do_not_inline(llret);
 141             }
 142
 143             if let Some((ret_dest, target)) = destination {
 144                 fx.store_return(bx, ret_dest, &fn_ty.ret, llret);
 145                 self.funclet_br(fx, bx, target);
 146             } else {
 147                 bx.unreachable();
 148             }
 149         }
 150     }
 151 }
 152
 153 /// Codegen implementations for some terminator variants.
 154 impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
 155     /// Generates code for a `Resume` terminator.
 156     fn codegen_resume_terminator<'b>(
 157         &mut self,
 158         helper: TerminatorCodegenHelper<'b, 'tcx>,
 159         mut bx: Bx,
 160     ) {
 161         if let Some(funclet) = helper.funclet(self) {
 162             bx.cleanup_ret(funclet, None);
 163         } else {
 164             let slot = self.get_personality_slot(&mut bx);
 165             let lp0 = slot.project_field(&mut bx, 0);
 166             let lp0 = bx.load_operand(lp0).immediate();
 167             let lp1 = slot.project_field(&mut bx, 1);
 168             let lp1 = bx.load_operand(lp1).immediate();
 169             slot.storage_dead(&mut bx);
 170
 171             if !bx.sess().target.target.options.custom_unwind_resume {
 172                 let mut lp = bx.const_undef(self.landing_pad_type());
 173                 lp = bx.insert_value(lp, lp0, 0);
 174                 lp = bx.insert_value(lp, lp1, 1);
 175                 bx.resume(lp);
 176             } else {
 177                 bx.call(bx.eh_unwind_resume(), &[lp0],
 178                         helper.funclet(self));
 179                 bx.unreachable();
 180             }
 181         }
 182     }
 183
 184     fn codegen_switchint_terminator<'b>(
 185         &mut self,
 186         helper: TerminatorCodegenHelper<'b, 'tcx>,
 187         mut bx: Bx,
 188         discr: &mir::Operand<'tcx>,
 189         switch_ty: Ty<'tcx>,
 190         values: &Cow<'tcx, [u128]>,
 191         targets: &Vec<mir::BasicBlock>,
 192     ) {
 193         let discr = self.codegen_operand(&mut bx, &discr);
 194         if targets.len() == 2 {
 195             // If there are two targets, emit br instead of switch
 196             let lltrue = helper.llblock(self, targets[0]);
 197             let llfalse = helper.llblock(self, targets[1]);
 198             if switch_ty == bx.tcx().types.bool {
 199                 // Don't generate trivial icmps when switching on bool
 200                 if let [0] = values[..] {
 201                     bx.cond_br(discr.immediate(), llfalse, lltrue);
 202                 } else {
 203                     assert_eq!(&values[..], &[1]);
 204                     bx.cond_br(discr.immediate(), lltrue, llfalse);
 205                 }
 206             } else {
 207                 let switch_llty = bx.immediate_backend_type(
 208                     bx.layout_of(switch_ty)
 209                 );
 210                 let llval = bx.const_uint_big(switch_llty, values[0]);
 211                 let cmp = bx.icmp(IntPredicate::IntEQ, discr.immediate(), llval);
 212                 bx.cond_br(cmp, lltrue, llfalse);
 213             }
 214         } else {
 215             let (otherwise, targets) = targets.split_last().unwrap();
 216             bx.switch(
 217                 discr.immediate(),
 218                 helper.llblock(self, *otherwise),
 219                 values.iter().zip(targets).map(|(&value, target)| {
 220                     (value, helper.llblock(self, *target))
 221                 })
 222             );
 223         }
 224     }
 225
 226     fn codegen_return_terminator(&mut self, mut bx: Bx) {
 227         if self.fn_ty.c_variadic {
 228             match self.va_list_ref {
 229                 Some(va_list) => {
 230                     bx.va_end(va_list.llval);
 231                 }
 232                 None => {
 233                     bug!("C-variadic function must have a `va_list_ref`");
 234                 }
 235             }
 236         }
 237         if self.fn_ty.ret.layout.abi.is_uninhabited() {
 238             // Functions with uninhabited return values are marked `noreturn`,
 239             // so we should make sure that we never actually do.
 240             bx.abort();
 241             bx.unreachable();
 242             return;
 243         }
 244         let llval = match self.fn_ty.ret.mode {
 245             PassMode::Ignore(IgnoreMode::Zst) | PassMode::Indirect(..) => {
 246                 bx.ret_void();
 247                 return;
 248             }
 249
 250             PassMode::Ignore(IgnoreMode::CVarArgs) => {
 251                 bug!("C-variadic arguments should never be the return type");
 252             }
 253
 254             PassMode::Direct(_) | PassMode::Pair(..) => {
 255                 let op =
 256                     self.codegen_consume(&mut bx, &mir::Place::RETURN_PLACE.as_ref());
 257                 if let Ref(llval, _, align) = op.val {
 258                     bx.load(llval, align)
 259                 } else {
 260                     op.immediate_or_packed_pair(&mut bx)
 261                 }
 262             }
 263
 264             PassMode::Cast(cast_ty) => {
 265                 let op = match self.locals[mir::RETURN_PLACE] {
 266                     LocalRef::Operand(Some(op)) => op,
 267                     LocalRef::Operand(None) => bug!("use of return before def"),
 268                     LocalRef::Place(cg_place) => {
 269                         OperandRef {
 270                             val: Ref(cg_place.llval, None, cg_place.align),
 271                             layout: cg_place.layout
 272                         }
 273                     }
 274                     LocalRef::UnsizedPlace(_) => bug!("return type must be sized"),
 275                 };
 276                 let llslot = match op.val {
 277                     Immediate(_) | Pair(..) => {
 278                         let scratch =
 279                             PlaceRef::alloca(&mut bx, self.fn_ty.ret.layout, "ret");
 280                         op.val.store(&mut bx, scratch);
 281                         scratch.llval
 282                     }
 283                     Ref(llval, _, align) => {
 284                         assert_eq!(align, op.layout.align.abi,
 285                                    "return place is unaligned!");
 286                         llval
 287                     }
 288                 };
 289                 let addr = bx.pointercast(llslot, bx.type_ptr_to(
 290                     bx.cast_backend_type(&cast_ty)
 291                 ));
 292                 bx.load(addr, self.fn_ty.ret.layout.align.abi)
 293             }
 294         };
 295         bx.ret(llval);
 296     }
 297
 298
 299     fn codegen_drop_terminator<'b>(
 300         &mut self,
 301         helper: TerminatorCodegenHelper<'b, 'tcx>,
 302         mut bx: Bx,
 303         location: &mir::Place<'tcx>,
 304         target: mir::BasicBlock,
 305         unwind: Option<mir::BasicBlock>,
 306     ) {
 307         let ty = location.ty(self.mir, bx.tcx()).ty;
 308         let ty = self.monomorphize(&ty);
 309         let drop_fn = Instance::resolve_drop_in_place(bx.tcx(), ty);
 310
 311         if let ty::InstanceDef::DropGlue(_, None) = drop_fn.def {
 312             // we don't actually need to drop anything.
 313             helper.funclet_br(self, &mut bx, target);
 314             return
 315         }
 316
 317         let place = self.codegen_place(&mut bx, &location.as_ref());
 318         let (args1, args2);
 319         let mut args = if let Some(llextra) = place.llextra {
 320             args2 = [place.llval, llextra];
 321             &args2[..]
 322         } else {
 323             args1 = [place.llval];
 324             &args1[..]
 325         };
 326         let (drop_fn, fn_ty) = match ty.sty {
 327             ty::Dynamic(..) => {
 328                 let sig = drop_fn.fn_sig(self.cx.tcx());
 329                 let sig = self.cx.tcx().normalize_erasing_late_bound_regions(
 330                     ty::ParamEnv::reveal_all(),
 331                     &sig,
 332                 );
 333                 let fn_ty = FnType::new_vtable(&bx, sig, &[]);
 334                 let vtable = args[1];
 335                 args = &args[..1];
 336                 (meth::DESTRUCTOR.get_fn(&mut bx, vtable, &fn_ty), fn_ty)
 337             }
 338             _ => {
 339                 (bx.get_fn(drop_fn),
 340                  FnType::of_instance(&bx, drop_fn))
 341             }
 342         };
 343         helper.do_call(self, &mut bx, fn_ty, drop_fn, args,
 344                        Some((ReturnDest::Nothing, target)),
 345                        unwind);
 346     }
 347
 348     fn codegen_assert_terminator<'b>(
 349         &mut self,
 350         helper: TerminatorCodegenHelper<'b, 'tcx>,
 351         mut bx: Bx,
 352         terminator: &mir::Terminator<'tcx>,
 353         cond: &mir::Operand<'tcx>,
 354         expected: bool,
 355         msg: &mir::AssertMessage<'tcx>,
 356         target: mir::BasicBlock,
 357         cleanup: Option<mir::BasicBlock>,
 358     ) {
 359         let span = terminator.source_info.span;
 360         let cond = self.codegen_operand(&mut bx, cond).immediate();
 361         let mut const_cond = bx.const_to_opt_u128(cond, false).map(|c| c == 1);
 362
 363         // This case can currently arise only from functions marked
 364         // with #[rustc_inherit_overflow_checks] and inlined from
 365         // another crate (mostly core::num generic/#[inline] fns),
 366         // while the current crate doesn't use overflow checks.
 367         // NOTE: Unlike binops, negation doesn't have its own
 368         // checked operation, just a comparison with the minimum
 369         // value, so we have to check for the assert message.
 370         if !bx.check_overflow() {
 371             if let PanicInfo::OverflowNeg = *msg {
 372                 const_cond = Some(expected);
 373             }
 374         }
 375
 376         // Don't codegen the panic block if success if known.
 377         if const_cond == Some(expected) {
 378             helper.funclet_br(self, &mut bx, target);
 379             return;
 380         }
 381
 382         // Pass the condition through llvm.expect for branch hinting.
 383         let cond = bx.expect(cond, expected);
 384
 385         // Create the failure block and the conditional branch to it.
 386         let lltarget = helper.llblock(self, target);
 387         let panic_block = self.new_block("panic");
 388         if expected {
 389             bx.cond_br(cond, lltarget, panic_block.llbb());
 390         } else {
 391             bx.cond_br(cond, panic_block.llbb(), lltarget);
 392         }
 393
 394         // After this point, bx is the block for the call to panic.
 395         bx = panic_block;
 396         self.set_debug_loc(&mut bx, terminator.source_info);
 397
 398         // Get the location information.
 399         let loc = bx.sess().source_map().lookup_char_pos(span.lo());
 400         let filename = LocalInternedString::intern(&loc.file.name.to_string());
 401         let line = bx.const_u32(loc.line as u32);
 402         let col = bx.const_u32(loc.col.to_usize() as u32 + 1);
 403
 404         // Put together the arguments to the panic entry point.
 405         let (lang_item, args) = match msg {
 406             PanicInfo::BoundsCheck { ref len, ref index } => {
 407                 let len = self.codegen_operand(&mut bx, len).immediate();
 408                 let index = self.codegen_operand(&mut bx, index).immediate();
 409
 410                 let file_line_col = bx.static_panic_msg(
 411                     None,
 412                     filename,
 413                     line,
 414                     col,
 415                     "panic_bounds_check_loc",
 416                 );
 417                 (lang_items::PanicBoundsCheckFnLangItem,
 418                     vec![file_line_col, index, len])
 419             }
 420             _ => {
 421                 let str = msg.description();
 422                 let msg_str = LocalInternedString::intern(str);
 423                 let msg_file_line_col = bx.static_panic_msg(
 424                     Some(msg_str),
 425                     filename,
 426                     line,
 427                     col,
 428                     "panic_loc",
 429                 );
 430                 (lang_items::PanicFnLangItem,
 431                     vec![msg_file_line_col])
 432             }
 433         };
 434
 435         // Obtain the panic entry point.
 436         let def_id = common::langcall(bx.tcx(), Some(span), "", lang_item);
 437         let instance = ty::Instance::mono(bx.tcx(), def_id);
 438         let fn_ty = FnType::of_instance(&bx, instance);
 439         let llfn = bx.get_fn(instance);
 440
 441         // Codegen the actual panic invoke/call.
 442         helper.do_call(self, &mut bx, fn_ty, llfn, &args, None, cleanup);
 443     }
 444
 445     fn codegen_call_terminator<'b>(
 446         &mut self,
 447         helper: TerminatorCodegenHelper<'b, 'tcx>,
 448         mut bx: Bx,
 449         terminator: &mir::Terminator<'tcx>,
 450         func: &mir::Operand<'tcx>,
 451         args: &Vec<mir::Operand<'tcx>>,
 452         destination: &Option<(mir::Place<'tcx>, mir::BasicBlock)>,
 453         cleanup: Option<mir::BasicBlock>,
 454     ) {
 455         let span = terminator.source_info.span;
 456         // Create the callee. This is a fn ptr or zero-sized and hence a kind of scalar.
 457         let callee = self.codegen_operand(&mut bx, func);
 458
 459         let (instance, mut llfn) = match callee.layout.ty.sty {
 460             ty::FnDef(def_id, substs) => {
 461                 (Some(ty::Instance::resolve(bx.tcx(),
 462                                             ty::ParamEnv::reveal_all(),
 463                                             def_id,
 464                                             substs).unwrap()),
 465                  None)
 466             }
 467             ty::FnPtr(_) => {
 468                 (None, Some(callee.immediate()))
 469             }
 470             _ => bug!("{} is not callable", callee.layout.ty),
 471         };
 472         let def = instance.map(|i| i.def);
 473         let sig = callee.layout.ty.fn_sig(bx.tcx());
 474         let sig = bx.tcx().normalize_erasing_late_bound_regions(
 475             ty::ParamEnv::reveal_all(),
 476             &sig,
 477         );
 478         let abi = sig.abi;
 479
 480         // Handle intrinsics old codegen wants Expr's for, ourselves.
 481         let intrinsic = match def {
 482             Some(ty::InstanceDef::Intrinsic(def_id)) =>
 483                 Some(bx.tcx().item_name(def_id).as_str()),
 484             _ => None
 485         };
 486         let intrinsic = intrinsic.as_ref().map(|s| &s[..]);
 487
 488         if intrinsic == Some("transmute") {
 489             if let Some(destination_ref) = destination.as_ref() {
 490                 let &(ref dest, target) = destination_ref;
 491                 self.codegen_transmute(&mut bx, &args[0], dest);
 492                 helper.funclet_br(self, &mut bx, target);
 493             } else {
 494                 // If we are trying to transmute to an uninhabited type,
 495                 // it is likely there is no allotted destination. In fact,
 496                 // transmuting to an uninhabited type is UB, which means
 497                 // we can do what we like. Here, we declare that transmuting
 498                 // into an uninhabited type is impossible, so anything following
 499                 // it must be unreachable.
 500                 assert_eq!(bx.layout_of(sig.output()).abi, layout::Abi::Uninhabited);
 501                 bx.unreachable();
 502             }
 503             return;
 504         }
 505
 506         // The "spoofed" `VaListImpl` added to a C-variadic functions signature
 507         // should not be included in the `extra_args` calculation.
 508         let extra_args_start_idx = sig.inputs().len() - if sig.c_variadic { 1 } else { 0 };
 509         let extra_args = &args[extra_args_start_idx..];
 510         let extra_args = extra_args.iter().map(|op_arg| {
 511             let op_ty = op_arg.ty(self.mir, bx.tcx());
 512             self.monomorphize(&op_ty)
 513         }).collect::<Vec<_>>();
 514
 515         let fn_ty = match def {
 516             Some(ty::InstanceDef::Virtual(..)) => {
 517                 FnType::new_vtable(&bx, sig, &extra_args)
 518             }
 519             Some(ty::InstanceDef::DropGlue(_, None)) => {
 520                 // Empty drop glue; a no-op.
 521                 let &(_, target) = destination.as_ref().unwrap();
 522                 helper.funclet_br(self, &mut bx, target);
 523                 return;
 524             }
 525             _ => FnType::new(&bx, sig, &extra_args)
 526         };
 527
 528         // Emit a panic or a no-op for `panic_if_uninhabited`.
 529         if intrinsic == Some("panic_if_uninhabited") {
 530             let ty = instance.unwrap().substs.type_at(0);
 531             let layout = bx.layout_of(ty);
 532             if layout.abi.is_uninhabited() {
 533                 let loc = bx.sess().source_map().lookup_char_pos(span.lo());
 534                 let filename = LocalInternedString::intern(&loc.file.name.to_string());
 535                 let line = bx.const_u32(loc.line as u32);
 536                 let col = bx.const_u32(loc.col.to_usize() as u32 + 1);
 537
 538                 let str = format!(
 539                     "Attempted to instantiate uninhabited type {}",
 540                     ty
 541                 );
 542                 let msg_str = LocalInternedString::intern(&str);
 543                 let msg_file_line_col = bx.static_panic_msg(
 544                     Some(msg_str),
 545                     filename,
 546                     line,
 547                     col,
 548                     "panic_loc",
 549                 );
 550
 551                 // Obtain the panic entry point.
 552                 let def_id =
 553                     common::langcall(bx.tcx(), Some(span), "", lang_items::PanicFnLangItem);
 554                 let instance = ty::Instance::mono(bx.tcx(), def_id);
 555                 let fn_ty = FnType::of_instance(&bx, instance);
 556                 let llfn = bx.get_fn(instance);
 557
 558                 // Codegen the actual panic invoke/call.
 559                 helper.do_call(
 560                     self,
 561                     &mut bx,
 562                     fn_ty,
 563                     llfn,
 564                     &[msg_file_line_col],
 565                     destination.as_ref().map(|(_, bb)| (ReturnDest::Nothing, *bb)),
 566                     cleanup,
 567                 );
 568             } else {
 569                 // a NOP
 570                 helper.funclet_br(self, &mut bx, destination.as_ref().unwrap().1)
 571             }
 572             return;
 573         }
 574
 575         // The arguments we'll be passing. Plus one to account for outptr, if used.
 576         let arg_count = fn_ty.args.len() + fn_ty.ret.is_indirect() as usize;
 577         let mut llargs = Vec::with_capacity(arg_count);
 578
 579         // Prepare the return value destination
 580         let ret_dest = if let Some((ref dest, _)) = *destination {
 581             let is_intrinsic = intrinsic.is_some();
 582             self.make_return_dest(&mut bx, dest, &fn_ty.ret, &mut llargs,
 583                                   is_intrinsic)
 584         } else {
 585             ReturnDest::Nothing
 586         };
 587
 588         if intrinsic.is_some() && intrinsic != Some("drop_in_place") {
 589             let dest = match ret_dest {
 590                 _ if fn_ty.ret.is_indirect() => llargs[0],
 591                 ReturnDest::Nothing =>
 592                     bx.const_undef(bx.type_ptr_to(bx.memory_ty(&fn_ty.ret))),
 593                 ReturnDest::IndirectOperand(dst, _) | ReturnDest::Store(dst) =>
 594                     dst.llval,
 595                 ReturnDest::DirectOperand(_) =>
 596                     bug!("Cannot use direct operand with an intrinsic call"),
 597             };
 598
 599             let args: Vec<_> = args.iter().enumerate().map(|(i, arg)| {
 600                 // The indices passed to simd_shuffle* in the
 601                 // third argument must be constant. This is
 602                 // checked by const-qualification, which also
 603                 // promotes any complex rvalues to constants.
 604                 if i == 2 && intrinsic.unwrap().starts_with("simd_shuffle") {
 605                     match *arg {
 606                         // The shuffle array argument is usually not an explicit constant,
 607                         // but specified directly in the code. This means it gets promoted
 608                         // and we can then extract the value by evaluating the promoted.
 609                         mir::Operand::Copy(
 610                             Place {
 611                                 base: PlaceBase::Static(box Static {
 612                                     kind: StaticKind::Promoted(promoted),
 613                                     ty,
 614                                 }),
 615                                 projection: None,
 616                             }
 617                         ) |
 618                         mir::Operand::Move(
 619                             Place {
 620                                 base: PlaceBase::Static(box Static {
 621                                     kind: StaticKind::Promoted(promoted),
 622                                     ty,
 623                                 }),
 624                                 projection: None,
 625                             }
 626                         ) => {
 627                             let param_env = ty::ParamEnv::reveal_all();
 628                             let cid = mir::interpret::GlobalId {
 629                                 instance: self.instance,
 630                                 promoted: Some(promoted),
 631                             };
 632                             let c = bx.tcx().const_eval(param_env.and(cid));
 633                             let (llval, ty) = self.simd_shuffle_indices(
 634                                 &bx,
 635                                 terminator.source_info.span,
 636                                 ty,
 637                                 c,
 638                             );
 639                             return OperandRef {
 640                                 val: Immediate(llval),
 641                                 layout: bx.layout_of(ty),
 642                             };
 643
 644                         }
 645                         mir::Operand::Copy(_) |
 646                         mir::Operand::Move(_) => {
 647                             span_bug!(span, "shuffle indices must be constant");
 648                         }
 649                         mir::Operand::Constant(ref constant) => {
 650                             let c = self.eval_mir_constant(constant);
 651                             let (llval, ty) = self.simd_shuffle_indices(
 652                                 &bx,
 653                                 constant.span,
 654                                 constant.ty,
 655                                 c,
 656                             );
 657                             return OperandRef {
 658                                 val: Immediate(llval),
 659                                 layout: bx.layout_of(ty)
 660                             };
 661                         }
 662                     }
 663                 }
 664
 665                 self.codegen_operand(&mut bx, arg)
 666             }).collect();
 667
 668
 669             let callee_ty = instance.as_ref().unwrap().ty(bx.tcx());
 670             bx.codegen_intrinsic_call(callee_ty, &fn_ty, &args, dest,
 671                                       terminator.source_info.span);
 672
 673             if let ReturnDest::IndirectOperand(dst, _) = ret_dest {
 674                 self.store_return(&mut bx, ret_dest, &fn_ty.ret, dst.llval);
 675             }
 676
 677             if let Some((_, target)) = *destination {
 678                 helper.funclet_br(self, &mut bx, target);
 679             } else {
 680                 bx.unreachable();
 681             }
 682
 683             return;
 684         }
 685
 686         // Split the rust-call tupled arguments off.
 687         let (first_args, untuple) = if abi == Abi::RustCall && !args.is_empty() {
 688             let (tup, args) = args.split_last().unwrap();
 689             (args, Some(tup))
 690         } else {
 691             (&args[..], None)
 692         };
 693
 694         // Useful determining if the current argument is the "spoofed" `VaListImpl`
 695         let last_arg_idx = if sig.inputs().is_empty() {
 696             None
 697         } else {
 698             Some(sig.inputs().len() - 1)
 699         };
 700         'make_args: for (i, arg) in first_args.iter().enumerate() {
 701             // If this is a C-variadic function the function signature contains
 702             // an "spoofed" `VaListImpl`. This argument is ignored, but we need to
 703             // populate it with a dummy operand so that the users real arguments
 704             // are not overwritten.
 705             let i = if sig.c_variadic && last_arg_idx.map(|x| i >= x).unwrap_or(false) {
 706                 if i + 1 < fn_ty.args.len() {
 707                     i + 1
 708                 } else {
 709                     break 'make_args
 710                 }
 711             } else {
 712                 i
 713             };
 714             let mut op = self.codegen_operand(&mut bx, arg);
 715
 716             if let (0, Some(ty::InstanceDef::Virtual(_, idx))) = (i, def) {
 717                 if let Pair(..) = op.val {
 718                     // In the case of Rc<Self>, we need to explicitly pass a
 719                     // *mut RcBox<Self> with a Scalar (not ScalarPair) ABI. This is a hack
 720                     // that is understood elsewhere in the compiler as a method on
 721                     // `dyn Trait`.
 722                     // To get a `*mut RcBox<Self>`, we just keep unwrapping newtypes until
 723                     // we get a value of a built-in pointer type
 724                     'descend_newtypes: while !op.layout.ty.is_unsafe_ptr()
 725                                     && !op.layout.ty.is_region_ptr()
 726                     {
 727                         'iter_fields: for i in 0..op.layout.fields.count() {
 728                             let field = op.extract_field(&mut bx, i);
 729                             if !field.layout.is_zst() {
 730                                 // we found the one non-zero-sized field that is allowed
 731                                 // now find *its* non-zero-sized field, or stop if it's a
 732                                 // pointer
 733                                 op = field;
 734                                 continue 'descend_newtypes
 735                             }
 736                         }
 737
 738                         span_bug!(span, "receiver has no non-zero-sized fields {:?}", op);
 739                     }
 740
 741                     // now that we have `*dyn Trait` or `&dyn Trait`, split it up into its
 742                     // data pointer and vtable. Look up the method in the vtable, and pass
 743                     // the data pointer as the first argument
 744                     match op.val {
 745                         Pair(data_ptr, meta) => {
 746                             llfn = Some(meth::VirtualIndex::from_index(idx)
 747                                 .get_fn(&mut bx, meta, &fn_ty));
 748                             llargs.push(data_ptr);
 749                             continue 'make_args
 750                         }
 751                         other => bug!("expected a Pair, got {:?}", other),
 752                     }
 753                 } else if let Ref(data_ptr, Some(meta), _) = op.val {
 754                     // by-value dynamic dispatch
 755                     llfn = Some(meth::VirtualIndex::from_index(idx)
 756                         .get_fn(&mut bx, meta, &fn_ty));
 757                     llargs.push(data_ptr);
 758                     continue;
 759                 } else {
 760                     span_bug!(span, "can't codegen a virtual call on {:?}", op);
 761                 }
 762             }
 763
 764             // The callee needs to own the argument memory if we pass it
 765             // by-ref, so make a local copy of non-immediate constants.
 766             match (arg, op.val) {
 767                 (&mir::Operand::Copy(_), Ref(_, None, _)) |
 768                 (&mir::Operand::Constant(_), Ref(_, None, _)) => {
 769                     let tmp = PlaceRef::alloca(&mut bx, op.layout, "const");
 770                     op.val.store(&mut bx, tmp);
 771                     op.val = Ref(tmp.llval, None, tmp.align);
 772                 }
 773                 _ => {}
 774             }
 775
 776             self.codegen_argument(&mut bx, op, &mut llargs, &fn_ty.args[i]);
 777         }
 778         if let Some(tup) = untuple {
 779             self.codegen_arguments_untupled(&mut bx, tup, &mut llargs,
 780                 &fn_ty.args[first_args.len()..])
 781         }
 782
 783         let fn_ptr = match (llfn, instance) {
 784             (Some(llfn), _) => llfn,
 785             (None, Some(instance)) => bx.get_fn(instance),
 786             _ => span_bug!(span, "no llfn for call"),
 787         };
 788
 789         helper.do_call(self, &mut bx, fn_ty, fn_ptr, &llargs,
 790                        destination.as_ref().map(|&(_, target)| (ret_dest, target)),
 791                        cleanup);
 792     }
 793 }
 794
 795 impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
 796     pub fn codegen_block(
 797         &mut self,
 798         bb: mir::BasicBlock,
 799     ) {
 800         let mut bx = self.build_block(bb);
 801         let data = &self.mir[bb];
 802
 803         debug!("codegen_block({:?}={:?})", bb, data);
 804
 805         for statement in &data.statements {
 806             bx = self.codegen_statement(bx, statement);
 807         }
 808
 809         self.codegen_terminator(bx, bb, data.terminator());
 810     }
 811
 812     fn codegen_terminator(
 813         &mut self,
 814         mut bx: Bx,
 815         bb: mir::BasicBlock,
 816         terminator: &mir::Terminator<'tcx>
 817     ) {
 818         debug!("codegen_terminator: {:?}", terminator);
 819
 820         // Create the cleanup bundle, if needed.
 821         let funclet_bb = self.cleanup_kinds[bb].funclet_bb(bb);
 822         let helper = TerminatorCodegenHelper {
 823             bb: &bb, terminator, funclet_bb
 824         };
 825
 826         self.set_debug_loc(&mut bx, terminator.source_info);
 827         match terminator.kind {
 828             mir::TerminatorKind::Resume => {
 829                 self.codegen_resume_terminator(helper, bx)
 830             }
 831
 832             mir::TerminatorKind::Abort => {
 833                 bx.abort();
 834                 bx.unreachable();
 835             }
 836
 837             mir::TerminatorKind::Goto { target } => {
 838                 helper.funclet_br(self, &mut bx, target);
 839             }
 840
 841             mir::TerminatorKind::SwitchInt {
 842                 ref discr, switch_ty, ref values, ref targets
 843             } => {
 844                 self.codegen_switchint_terminator(helper, bx, discr, switch_ty,
 845                                                   values, targets);
 846             }
 847
 848             mir::TerminatorKind::Return => {
 849                 self.codegen_return_terminator(bx);
 850             }
 851
 852             mir::TerminatorKind::Unreachable => {
 853                 bx.unreachable();
 854             }
 855
 856             mir::TerminatorKind::Drop { ref location, target, unwind } => {
 857                 self.codegen_drop_terminator(helper, bx, location, target, unwind);
 858             }
 859
 860             mir::TerminatorKind::Assert { ref cond, expected, ref msg, target, cleanup } => {
 861                 self.codegen_assert_terminator(helper, bx, terminator, cond,
 862                                                expected, msg, target, cleanup);
 863             }
 864
 865             mir::TerminatorKind::DropAndReplace { .. } => {
 866                 bug!("undesugared DropAndReplace in codegen: {:?}", terminator);
 867             }
 868
 869             mir::TerminatorKind::Call {
 870                 ref func,
 871                 ref args,
 872                 ref destination,
 873                 cleanup,
 874                 from_hir_call: _
 875             } => {
 876                 self.codegen_call_terminator(helper, bx, terminator, func,
 877                                              args, destination, cleanup);
 878             }
 879             mir::TerminatorKind::GeneratorDrop |
 880             mir::TerminatorKind::Yield { .. } => bug!("generator ops in codegen"),
 881             mir::TerminatorKind::FalseEdges { .. } |
 882             mir::TerminatorKind::FalseUnwind { .. } => bug!("borrowck false edges in codegen"),
 883         }
 884     }
 885
 886     fn codegen_argument(
 887         &mut self,
 888         bx: &mut Bx,
 889         op: OperandRef<'tcx, Bx::Value>,
 890         llargs: &mut Vec<Bx::Value>,
 891         arg: &ArgType<'tcx, Ty<'tcx>>
 892     ) {
 893         // Fill padding with undef value, where applicable.
 894         if let Some(ty) = arg.pad {
 895             llargs.push(bx.const_undef(bx.reg_backend_type(&ty)))
 896         }
 897
 898         if arg.is_ignore() {
 899             return;
 900         }
 901
 902         if let PassMode::Pair(..) = arg.mode {
 903             match op.val {
 904                 Pair(a, b) => {
 905                     llargs.push(a);
 906                     llargs.push(b);
 907                     return;
 908                 }
 909                 _ => bug!("codegen_argument: {:?} invalid for pair argument", op)
 910             }
 911         } else if arg.is_unsized_indirect() {
 912             match op.val {
 913                 Ref(a, Some(b), _) => {
 914                     llargs.push(a);
 915                     llargs.push(b);
 916                     return;
 917                 }
 918                 _ => bug!("codegen_argument: {:?} invalid for unsized indirect argument", op)
 919             }
 920         }
 921
 922         // Force by-ref if we have to load through a cast pointer.
 923         let (mut llval, align, by_ref) = match op.val {
 924             Immediate(_) | Pair(..) => {
 925                 match arg.mode {
 926                     PassMode::Indirect(..) | PassMode::Cast(_) => {
 927                         let scratch = PlaceRef::alloca(bx, arg.layout, "arg");
 928                         op.val.store(bx, scratch);
 929                         (scratch.llval, scratch.align, true)
 930                     }
 931                     _ => {
 932                         (op.immediate_or_packed_pair(bx), arg.layout.align.abi, false)
 933                     }
 934                 }
 935             }
 936             Ref(llval, _, align) => {
 937                 if arg.is_indirect() && align < arg.layout.align.abi {
 938                     // `foo(packed.large_field)`. We can't pass the (unaligned) field directly. I
 939                     // think that ATM (Rust 1.16) we only pass temporaries, but we shouldn't
 940                     // have scary latent bugs around.
 941
 942                     let scratch = PlaceRef::alloca(bx, arg.layout, "arg");
 943                     base::memcpy_ty(bx, scratch.llval, scratch.align, llval, align,
 944                                     op.layout, MemFlags::empty());
 945                     (scratch.llval, scratch.align, true)
 946                 } else {
 947                     (llval, align, true)
 948                 }
 949             }
 950         };
 951
 952         if by_ref && !arg.is_indirect() {
 953             // Have to load the argument, maybe while casting it.
 954             if let PassMode::Cast(ty) = arg.mode {
 955                 let addr = bx.pointercast(llval, bx.type_ptr_to(
 956                     bx.cast_backend_type(&ty))
 957                 );
 958                 llval = bx.load(addr, align.min(arg.layout.align.abi));
 959             } else {
 960                 // We can't use `PlaceRef::load` here because the argument
 961                 // may have a type we don't treat as immediate, but the ABI
 962                 // used for this call is passing it by-value. In that case,
 963                 // the load would just produce `OperandValue::Ref` instead
 964                 // of the `OperandValue::Immediate` we need for the call.
 965                 llval = bx.load(llval, align);
 966                 if let layout::Abi::Scalar(ref scalar) = arg.layout.abi {
 967                     if scalar.is_bool() {
 968                         bx.range_metadata(llval, 0..2);
 969                     }
 970                 }
 971                 // We store bools as `i8` so we need to truncate to `i1`.
 972                 llval = base::to_immediate(bx, llval, arg.layout);
 973             }
 974         }
 975
 976         llargs.push(llval);
 977     }
 978
 979     fn codegen_arguments_untupled(
 980         &mut self,
 981         bx: &mut Bx,
 982         operand: &mir::Operand<'tcx>,
 983         llargs: &mut Vec<Bx::Value>,
 984         args: &[ArgType<'tcx, Ty<'tcx>>]
 985     ) {
 986         let tuple = self.codegen_operand(bx, operand);
 987
 988         // Handle both by-ref and immediate tuples.
 989         if let Ref(llval, None, align) = tuple.val {
 990             let tuple_ptr = PlaceRef::new_sized(llval, tuple.layout, align);
 991             for i in 0..tuple.layout.fields.count() {
 992                 let field_ptr = tuple_ptr.project_field(bx, i);
 993                 let field = bx.load_operand(field_ptr);
 994                 self.codegen_argument(bx, field, llargs, &args[i]);
 995             }
 996         } else if let Ref(_, Some(_), _) = tuple.val {
 997             bug!("closure arguments must be sized")
 998         } else {
 999             // If the tuple is immediate, the elements are as well.
1000             for i in 0..tuple.layout.fields.count() {
1001                 let op = tuple.extract_field(bx, i);
1002                 self.codegen_argument(bx, op, llargs, &args[i]);
1003             }
1004         }
1005     }
1006
1007     fn get_personality_slot(
1008         &mut self,
1009         bx: &mut Bx
1010     ) -> PlaceRef<'tcx, Bx::Value> {
1011         let cx = bx.cx();
1012         if let Some(slot) = self.personality_slot {
1013             slot
1014         } else {
1015             let layout = cx.layout_of(cx.tcx().intern_tup(&[
1016                 cx.tcx().mk_mut_ptr(cx.tcx().types.u8),
1017                 cx.tcx().types.i32
1018             ]));
1019             let slot = PlaceRef::alloca(bx, layout, "personalityslot");
1020             self.personality_slot = Some(slot);
1021             slot
1022         }
1023     }
1024
1025     /// Returns the landing-pad wrapper around the given basic block.
1026     ///
1027     /// No-op in MSVC SEH scheme.
1028     fn landing_pad_to(
1029         &mut self,
1030         target_bb: mir::BasicBlock
1031     ) -> Bx::BasicBlock {
1032         if let Some(block) = self.landing_pads[target_bb] {
1033             return block;
1034         }
1035
1036         let block = self.blocks[target_bb];
1037         let landing_pad = self.landing_pad_uncached(block);
1038         self.landing_pads[target_bb] = Some(landing_pad);
1039         landing_pad
1040     }
1041
1042     fn landing_pad_uncached(
1043         &mut self,
1044         target_bb: Bx::BasicBlock
1045     ) -> Bx::BasicBlock {
1046         if base::wants_msvc_seh(self.cx.sess()) {
1047             span_bug!(self.mir.span, "landing pad was not inserted?")
1048         }
1049
1050         let mut bx = self.new_block("cleanup");
1051
1052         let llpersonality = self.cx.eh_personality();
1053         let llretty = self.landing_pad_type();
1054         let lp = bx.landing_pad(llretty, llpersonality, 1);
1055         bx.set_cleanup(lp);
1056
1057         let slot = self.get_personality_slot(&mut bx);
1058         slot.storage_live(&mut bx);
1059         Pair(bx.extract_value(lp, 0), bx.extract_value(lp, 1)).store(&mut bx, slot);
1060
1061         bx.br(target_bb);
1062         bx.llbb()
1063     }
1064
1065     fn landing_pad_type(&self) -> Bx::Type {
1066         let cx = self.cx;
1067         cx.type_struct(&[cx.type_i8p(), cx.type_i32()], false)
1068     }
1069
1070     fn unreachable_block(
1071         &mut self
1072     ) -> Bx::BasicBlock {
1073         self.unreachable_block.unwrap_or_else(|| {
1074             let mut bx = self.new_block("unreachable");
1075             bx.unreachable();
1076             self.unreachable_block = Some(bx.llbb());
1077             bx.llbb()
1078         })
1079     }
1080
1081     pub fn new_block(&self, name: &str) -> Bx {
1082         Bx::new_block(self.cx, self.llfn, name)
1083     }
1084
1085     pub fn build_block(
1086         &self,
1087         bb: mir::BasicBlock
1088     ) -> Bx {
1089         let mut bx = Bx::with_cx(self.cx);
1090         bx.position_at_end(self.blocks[bb]);
1091         bx
1092     }
1093
1094     fn make_return_dest(
1095         &mut self,
1096         bx: &mut Bx,
1097         dest: &mir::Place<'tcx>,
1098         fn_ret: &ArgType<'tcx, Ty<'tcx>>,
1099         llargs: &mut Vec<Bx::Value>, is_intrinsic: bool
1100     ) -> ReturnDest<'tcx, Bx::Value> {
1101         // If the return is ignored, we can just return a do-nothing `ReturnDest`.
1102         if fn_ret.is_ignore() {
1103             return ReturnDest::Nothing;
1104         }
1105         let dest = if let mir::Place {
1106             base: mir::PlaceBase::Local(index),
1107             projection: None,
1108         } = *dest {
1109             match self.locals[index] {
1110                 LocalRef::Place(dest) => dest,
1111                 LocalRef::UnsizedPlace(_) => bug!("return type must be sized"),
1112                 LocalRef::Operand(None) => {
1113                     // Handle temporary places, specifically `Operand` ones, as
1114                     // they don't have `alloca`s.
1115                     return if fn_ret.is_indirect() {
1116                         // Odd, but possible, case, we have an operand temporary,
1117                         // but the calling convention has an indirect return.
1118                         let tmp = PlaceRef::alloca(bx, fn_ret.layout, "tmp_ret");
1119                         tmp.storage_live(bx);
1120                         llargs.push(tmp.llval);
1121                         ReturnDest::IndirectOperand(tmp, index)
1122                     } else if is_intrinsic {
1123                         // Currently, intrinsics always need a location to store
1124                         // the result, so we create a temporary `alloca` for the
1125                         // result.
1126                         let tmp = PlaceRef::alloca(bx, fn_ret.layout, "tmp_ret");
1127                         tmp.storage_live(bx);
1128                         ReturnDest::IndirectOperand(tmp, index)
1129                     } else {
1130                         ReturnDest::DirectOperand(index)
1131                     };
1132                 }
1133                 LocalRef::Operand(Some(_)) => {
1134                     bug!("place local already assigned to");
1135                 }
1136             }
1137         } else {
1138             self.codegen_place(bx, &mir::PlaceRef {
1139                 base: &dest.base,
1140                 projection: &dest.projection,
1141             })
1142         };
1143         if fn_ret.is_indirect() {
1144             if dest.align < dest.layout.align.abi {
1145                 // Currently, MIR code generation does not create calls
1146                 // that store directly to fields of packed structs (in
1147                 // fact, the calls it creates write only to temps).
1148                 //
1149                 // If someone changes that, please update this code path
1150                 // to create a temporary.
1151                 span_bug!(self.mir.span, "can't directly store to unaligned value");
1152             }
1153             llargs.push(dest.llval);
1154             ReturnDest::Nothing
1155         } else {
1156             ReturnDest::Store(dest)
1157         }
1158     }
1159
1160     fn codegen_transmute(
1161         &mut self,
1162         bx: &mut Bx,
1163         src: &mir::Operand<'tcx>,
1164         dst: &mir::Place<'tcx>
1165     ) {
1166         if let mir::Place {
1167             base: mir::PlaceBase::Local(index),
1168             projection: None,
1169         } = *dst {
1170             match self.locals[index] {
1171                 LocalRef::Place(place) => self.codegen_transmute_into(bx, src, place),
1172                 LocalRef::UnsizedPlace(_) => bug!("transmute must not involve unsized locals"),
1173                 LocalRef::Operand(None) => {
1174                     let dst_layout = bx.layout_of(self.monomorphized_place_ty(&dst.as_ref()));
1175                     assert!(!dst_layout.ty.has_erasable_regions());
1176                     let place = PlaceRef::alloca(bx, dst_layout, "transmute_temp");
1177                     place.storage_live(bx);
1178                     self.codegen_transmute_into(bx, src, place);
1179                     let op = bx.load_operand(place);
1180                     place.storage_dead(bx);
1181                     self.locals[index] = LocalRef::Operand(Some(op));
1182                 }
1183                 LocalRef::Operand(Some(op)) => {
1184                     assert!(op.layout.is_zst(),
1185                             "assigning to initialized SSAtemp");
1186                 }
1187             }
1188         } else {
1189             let dst = self.codegen_place(bx, &dst.as_ref());
1190             self.codegen_transmute_into(bx, src, dst);
1191         }
1192     }
1193
1194     fn codegen_transmute_into(
1195         &mut self,
1196         bx: &mut Bx,
1197         src: &mir::Operand<'tcx>,
1198         dst: PlaceRef<'tcx, Bx::Value>
1199     ) {
1200         let src = self.codegen_operand(bx, src);
1201         let llty = bx.backend_type(src.layout);
1202         let cast_ptr = bx.pointercast(dst.llval, bx.type_ptr_to(llty));
1203         let align = src.layout.align.abi.min(dst.align);
1204         src.val.store(bx, PlaceRef::new_sized(cast_ptr, src.layout, align));
1205     }
1206
1207
1208     // Stores the return value of a function call into it's final location.
1209     fn store_return(
1210         &mut self,
1211         bx: &mut Bx,
1212         dest: ReturnDest<'tcx, Bx::Value>,
1213         ret_ty: &ArgType<'tcx, Ty<'tcx>>,
1214         llval: Bx::Value
1215     ) {
1216         use self::ReturnDest::*;
1217
1218         match dest {
1219             Nothing => (),
1220             Store(dst) => bx.store_arg_ty(&ret_ty, llval, dst),
1221             IndirectOperand(tmp, index) => {
1222                 let op = bx.load_operand(tmp);
1223                 tmp.storage_dead(bx);
1224                 self.locals[index] = LocalRef::Operand(Some(op));
1225             }
1226             DirectOperand(index) => {
1227                 // If there is a cast, we have to store and reload.
1228                 let op = if let PassMode::Cast(_) = ret_ty.mode {
1229                     let tmp = PlaceRef::alloca(bx, ret_ty.layout, "tmp_ret");
1230                     tmp.storage_live(bx);
1231                     bx.store_arg_ty(&ret_ty, llval, tmp);
1232                     let op = bx.load_operand(tmp);
1233                     tmp.storage_dead(bx);
1234                     op
1235                 } else {
1236                     OperandRef::from_immediate_or_packed_pair(bx, llval, ret_ty.layout)
1237                 };
1238                 self.locals[index] = LocalRef::Operand(Some(op));
1239             }
1240         }
1241     }
1242 }
1243
1244 enum ReturnDest<'tcx, V> {
1245     // Do nothing; the return value is indirect or ignored.
1246     Nothing,
1247     // Store the return value to the pointer.
1248     Store(PlaceRef<'tcx, V>),
1249     // Store an indirect return value to an operand local place.
1250     IndirectOperand(PlaceRef<'tcx, V>, mir::Local),
1251     // Store a direct return value to an operand local place.
1252     DirectOperand(mir::Local)
1253 }