src/librustc_codegen_ssa/mir/block.rs

   1 use rustc_index::vec::Idx;
   2 use rustc::middle::lang_items;
   3 use rustc::ty::{self, Ty, TypeFoldable, Instance};
   4 use rustc::ty::layout::{self, LayoutOf, HasTyCtxt, FnTypeExt};
   5 use rustc::mir::{self, Place, PlaceBase, Static, StaticKind};
   6 use rustc::mir::interpret::PanicInfo;
   7 use rustc_target::abi::call::{ArgType, FnType, PassMode};
   8 use rustc_target::spec::abi::Abi;
   9 use crate::base;
  10 use crate::MemFlags;
  11 use crate::common::{self, IntPredicate};
  12 use crate::meth;
  13
  14 use crate::traits::*;
  15
  16 use std::borrow::Cow;
  17
  18 use syntax::symbol::Symbol;
  19 use syntax_pos::Pos;
  20
  21 use super::{FunctionCx, LocalRef};
  22 use super::place::PlaceRef;
  23 use super::operand::OperandRef;
  24 use super::operand::OperandValue::{Pair, Ref, Immediate};
  25
  26 /// Used by `FunctionCx::codegen_terminator` for emitting common patterns
  27 /// e.g., creating a basic block, calling a function, etc.
  28 struct TerminatorCodegenHelper<'a, 'tcx> {
  29     bb: &'a mir::BasicBlock,
  30     terminator: &'a mir::Terminator<'tcx>,
  31     funclet_bb: Option<mir::BasicBlock>,
  32 }
  33
  34 impl<'a, 'tcx> TerminatorCodegenHelper<'a, 'tcx> {
  35     /// Returns the associated funclet from `FunctionCx::funclets` for the
  36     /// `funclet_bb` member if it is not `None`.
  37     fn funclet<'c, 'b, Bx: BuilderMethods<'b, 'tcx>>(
  38         &self,
  39         fx: &'c mut FunctionCx<'b, 'tcx, Bx>,
  40     ) -> Option<&'c Bx::Funclet> {
  41         match self.funclet_bb {
  42             Some(funcl) => fx.funclets[funcl].as_ref(),
  43             None => None,
  44         }
  45     }
  46
  47     fn lltarget<'b, 'c, Bx: BuilderMethods<'b, 'tcx>>(
  48         &self,
  49         fx: &'c mut FunctionCx<'b, 'tcx, Bx>,
  50         target: mir::BasicBlock,
  51     ) -> (Bx::BasicBlock, bool) {
  52         let span = self.terminator.source_info.span;
  53         let lltarget = fx.blocks[target];
  54         let target_funclet = fx.cleanup_kinds[target].funclet_bb(target);
  55         match (self.funclet_bb, target_funclet) {
  56             (None, None) => (lltarget, false),
  57             (Some(f), Some(t_f)) if f == t_f || !base::wants_msvc_seh(fx.cx.tcx().sess) =>
  58                 (lltarget, false),
  59             // jump *into* cleanup - need a landing pad if GNU
  60             (None, Some(_)) => (fx.landing_pad_to(target), false),
  61             (Some(_), None) => span_bug!(span, "{:?} - jump out of cleanup?", self.terminator),
  62             (Some(_), Some(_)) => (fx.landing_pad_to(target), true),
  63         }
  64     }
  65
  66     /// Create a basic block.
  67     fn llblock<'c, 'b, Bx: BuilderMethods<'b, 'tcx>>(
  68         &self,
  69         fx: &'c mut FunctionCx<'b, 'tcx, Bx>,
  70         target: mir::BasicBlock,
  71     ) -> Bx::BasicBlock {
  72         let (lltarget, is_cleanupret) = self.lltarget(fx, target);
  73         if is_cleanupret {
  74             // MSVC cross-funclet jump - need a trampoline
  75
  76             debug!("llblock: creating cleanup trampoline for {:?}", target);
  77             let name = &format!("{:?}_cleanup_trampoline_{:?}", self.bb, target);
  78             let mut trampoline = fx.new_block(name);
  79             trampoline.cleanup_ret(self.funclet(fx).unwrap(),
  80                                    Some(lltarget));
  81             trampoline.llbb()
  82         } else {
  83             lltarget
  84         }
  85     }
  86
  87     fn funclet_br<'c, 'b, Bx: BuilderMethods<'b, 'tcx>>(
  88         &self,
  89         fx: &'c mut FunctionCx<'b, 'tcx, Bx>,
  90         bx: &mut Bx,
  91         target: mir::BasicBlock,
  92     ) {
  93         let (lltarget, is_cleanupret) = self.lltarget(fx, target);
  94         if is_cleanupret {
  95             // micro-optimization: generate a `ret` rather than a jump
  96             // to a trampoline.
  97             bx.cleanup_ret(self.funclet(fx).unwrap(), Some(lltarget));
  98         } else {
  99             bx.br(lltarget);
 100         }
 101     }
 102
 103     /// Call `fn_ptr` of `fn_ty` with the arguments `llargs`, the optional
 104     /// return destination `destination` and the cleanup function `cleanup`.
 105     fn do_call<'c, 'b, Bx: BuilderMethods<'b, 'tcx>>(
 106         &self,
 107         fx: &'c mut FunctionCx<'b, 'tcx, Bx>,
 108         bx: &mut Bx,
 109         fn_ty: FnType<'tcx, Ty<'tcx>>,
 110         fn_ptr: Bx::Value,
 111         llargs: &[Bx::Value],
 112         destination: Option<(ReturnDest<'tcx, Bx::Value>, mir::BasicBlock)>,
 113         cleanup: Option<mir::BasicBlock>,
 114     ) {
 115         if let Some(cleanup) = cleanup {
 116             let ret_bx = if let Some((_, target)) = destination {
 117                 fx.blocks[target]
 118             } else {
 119                 fx.unreachable_block()
 120             };
 121             let invokeret = bx.invoke(fn_ptr,
 122                                       &llargs,
 123                                       ret_bx,
 124                                       self.llblock(fx, cleanup),
 125                                       self.funclet(fx));
 126             bx.apply_attrs_callsite(&fn_ty, invokeret);
 127
 128             if let Some((ret_dest, target)) = destination {
 129                 let mut ret_bx = fx.build_block(target);
 130                 fx.set_debug_loc(&mut ret_bx, self.terminator.source_info);
 131                 fx.store_return(&mut ret_bx, ret_dest, &fn_ty.ret, invokeret);
 132             }
 133         } else {
 134             let llret = bx.call(fn_ptr, &llargs, self.funclet(fx));
 135             bx.apply_attrs_callsite(&fn_ty, llret);
 136             if fx.mir[*self.bb].is_cleanup {
 137                 // Cleanup is always the cold path. Don't inline
 138                 // drop glue. Also, when there is a deeply-nested
 139                 // struct, there are "symmetry" issues that cause
 140                 // exponential inlining - see issue #41696.
 141                 bx.do_not_inline(llret);
 142             }
 143
 144             if let Some((ret_dest, target)) = destination {
 145                 fx.store_return(bx, ret_dest, &fn_ty.ret, llret);
 146                 self.funclet_br(fx, bx, target);
 147             } else {
 148                 bx.unreachable();
 149             }
 150         }
 151     }
 152
 153     // Generate sideeffect intrinsic if jumping to any of the targets can form
 154     // a loop.
 155     fn maybe_sideeffect<'b, 'tcx2: 'b, Bx: BuilderMethods<'b, 'tcx2>>(
 156         &self,
 157         mir: &'b mir::Body<'tcx>,
 158         bx: &mut Bx,
 159         targets: &[mir::BasicBlock],
 160     ) {
 161         if bx.tcx().sess.opts.debugging_opts.insert_sideeffect {
 162             if targets.iter().any(|target| {
 163                 *target <= *self.bb
 164                     && target
 165                         .start_location()
 166                         .is_predecessor_of(self.bb.start_location(), mir)
 167             }) {
 168                 bx.sideeffect();
 169             }
 170         }
 171     }
 172 }
 173
 174 /// Codegen implementations for some terminator variants.
 175 impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
 176     /// Generates code for a `Resume` terminator.
 177     fn codegen_resume_terminator<'b>(
 178         &mut self,
 179         helper: TerminatorCodegenHelper<'b, 'tcx>,
 180         mut bx: Bx,
 181     ) {
 182         if let Some(funclet) = helper.funclet(self) {
 183             bx.cleanup_ret(funclet, None);
 184         } else {
 185             let slot = self.get_personality_slot(&mut bx);
 186             let lp0 = slot.project_field(&mut bx, 0);
 187             let lp0 = bx.load_operand(lp0).immediate();
 188             let lp1 = slot.project_field(&mut bx, 1);
 189             let lp1 = bx.load_operand(lp1).immediate();
 190             slot.storage_dead(&mut bx);
 191
 192             if !bx.sess().target.target.options.custom_unwind_resume {
 193                 let mut lp = bx.const_undef(self.landing_pad_type());
 194                 lp = bx.insert_value(lp, lp0, 0);
 195                 lp = bx.insert_value(lp, lp1, 1);
 196                 bx.resume(lp);
 197             } else {
 198                 bx.call(bx.eh_unwind_resume(), &[lp0],
 199                         helper.funclet(self));
 200                 bx.unreachable();
 201             }
 202         }
 203     }
 204
 205     fn codegen_switchint_terminator<'b>(
 206         &mut self,
 207         helper: TerminatorCodegenHelper<'b, 'tcx>,
 208         mut bx: Bx,
 209         discr: &mir::Operand<'tcx>,
 210         switch_ty: Ty<'tcx>,
 211         values: &Cow<'tcx, [u128]>,
 212         targets: &Vec<mir::BasicBlock>,
 213     ) {
 214         let discr = self.codegen_operand(&mut bx, &discr);
 215         if targets.len() == 2 {
 216             // If there are two targets, emit br instead of switch
 217             let lltrue = helper.llblock(self, targets[0]);
 218             let llfalse = helper.llblock(self, targets[1]);
 219             if switch_ty == bx.tcx().types.bool {
 220                 helper.maybe_sideeffect(self.mir, &mut bx, targets.as_slice());
 221                 // Don't generate trivial icmps when switching on bool
 222                 if let [0] = values[..] {
 223                     bx.cond_br(discr.immediate(), llfalse, lltrue);
 224                 } else {
 225                     assert_eq!(&values[..], &[1]);
 226                     bx.cond_br(discr.immediate(), lltrue, llfalse);
 227                 }
 228             } else {
 229                 let switch_llty = bx.immediate_backend_type(
 230                     bx.layout_of(switch_ty)
 231                 );
 232                 let llval = bx.const_uint_big(switch_llty, values[0]);
 233                 let cmp = bx.icmp(IntPredicate::IntEQ, discr.immediate(), llval);
 234                 helper.maybe_sideeffect(self.mir, &mut bx, targets.as_slice());
 235                 bx.cond_br(cmp, lltrue, llfalse);
 236             }
 237         } else {
 238             helper.maybe_sideeffect(self.mir, &mut bx, targets.as_slice());
 239             let (otherwise, targets) = targets.split_last().unwrap();
 240             bx.switch(
 241                 discr.immediate(),
 242                 helper.llblock(self, *otherwise),
 243                 values.iter().zip(targets).map(|(&value, target)| {
 244                     (value, helper.llblock(self, *target))
 245                 })
 246             );
 247         }
 248     }
 249
 250     fn codegen_return_terminator(&mut self, mut bx: Bx) {
 251         // Call `va_end` if this is the definition of a C-variadic function.
 252         if self.fn_ty.c_variadic {
 253             // The `VaList` "spoofed" argument is just after all the real arguments.
 254             let va_list_arg_idx = self.fn_ty.args.len();
 255             match self.locals[mir::Local::new(1 + va_list_arg_idx)] {
 256                 LocalRef::Place(va_list) => {
 257                     bx.va_end(va_list.llval);
 258                 }
 259                 _ => bug!("C-variadic function must have a `VaList` place"),
 260             }
 261         }
 262         if self.fn_ty.ret.layout.abi.is_uninhabited() {
 263             // Functions with uninhabited return values are marked `noreturn`,
 264             // so we should make sure that we never actually do.
 265             bx.abort();
 266             bx.unreachable();
 267             return;
 268         }
 269         let llval = match self.fn_ty.ret.mode {
 270             PassMode::Ignore | PassMode::Indirect(..) => {
 271                 bx.ret_void();
 272                 return;
 273             }
 274
 275             PassMode::Direct(_) | PassMode::Pair(..) => {
 276                 let op =
 277                     self.codegen_consume(&mut bx, &mir::Place::return_place().as_ref());
 278                 if let Ref(llval, _, align) = op.val {
 279                     bx.load(llval, align)
 280                 } else {
 281                     op.immediate_or_packed_pair(&mut bx)
 282                 }
 283             }
 284
 285             PassMode::Cast(cast_ty) => {
 286                 let op = match self.locals[mir::RETURN_PLACE] {
 287                     LocalRef::Operand(Some(op)) => op,
 288                     LocalRef::Operand(None) => bug!("use of return before def"),
 289                     LocalRef::Place(cg_place) => {
 290                         OperandRef {
 291                             val: Ref(cg_place.llval, None, cg_place.align),
 292                             layout: cg_place.layout
 293                         }
 294                     }
 295                     LocalRef::UnsizedPlace(_) => bug!("return type must be sized"),
 296                 };
 297                 let llslot = match op.val {
 298                     Immediate(_) | Pair(..) => {
 299                         let scratch =
 300                             PlaceRef::alloca(&mut bx, self.fn_ty.ret.layout);
 301                         op.val.store(&mut bx, scratch);
 302                         scratch.llval
 303                     }
 304                     Ref(llval, _, align) => {
 305                         assert_eq!(align, op.layout.align.abi,
 306                                    "return place is unaligned!");
 307                         llval
 308                     }
 309                 };
 310                 let addr = bx.pointercast(llslot, bx.type_ptr_to(
 311                     bx.cast_backend_type(&cast_ty)
 312                 ));
 313                 bx.load(addr, self.fn_ty.ret.layout.align.abi)
 314             }
 315         };
 316         bx.ret(llval);
 317     }
 318
 319
 320     fn codegen_drop_terminator<'b>(
 321         &mut self,
 322         helper: TerminatorCodegenHelper<'b, 'tcx>,
 323         mut bx: Bx,
 324         location: &mir::Place<'tcx>,
 325         target: mir::BasicBlock,
 326         unwind: Option<mir::BasicBlock>,
 327     ) {
 328         let ty = location.ty(self.mir, bx.tcx()).ty;
 329         let ty = self.monomorphize(&ty);
 330         let drop_fn = Instance::resolve_drop_in_place(bx.tcx(), ty);
 331
 332         if let ty::InstanceDef::DropGlue(_, None) = drop_fn.def {
 333             // we don't actually need to drop anything.
 334             helper.maybe_sideeffect(self.mir, &mut bx, &[target]);
 335             helper.funclet_br(self, &mut bx, target);
 336             return
 337         }
 338
 339         let place = self.codegen_place(&mut bx, &location.as_ref());
 340         let (args1, args2);
 341         let mut args = if let Some(llextra) = place.llextra {
 342             args2 = [place.llval, llextra];
 343             &args2[..]
 344         } else {
 345             args1 = [place.llval];
 346             &args1[..]
 347         };
 348         let (drop_fn, fn_ty) = match ty.kind {
 349             ty::Dynamic(..) => {
 350                 let sig = drop_fn.fn_sig(self.cx.tcx());
 351                 let sig = self.cx.tcx().normalize_erasing_late_bound_regions(
 352                     ty::ParamEnv::reveal_all(),
 353                     &sig,
 354                 );
 355                 let fn_ty = FnType::new_vtable(&bx, sig, &[]);
 356                 let vtable = args[1];
 357                 args = &args[..1];
 358                 (meth::DESTRUCTOR.get_fn(&mut bx, vtable, &fn_ty), fn_ty)
 359             }
 360             _ => {
 361                 (bx.get_fn_addr(drop_fn),
 362                  FnType::of_instance(&bx, drop_fn))
 363             }
 364         };
 365         helper.maybe_sideeffect(self.mir, &mut bx, &[target]);
 366         helper.do_call(self, &mut bx, fn_ty, drop_fn, args,
 367                        Some((ReturnDest::Nothing, target)),
 368                        unwind);
 369     }
 370
 371     fn codegen_assert_terminator<'b>(
 372         &mut self,
 373         helper: TerminatorCodegenHelper<'b, 'tcx>,
 374         mut bx: Bx,
 375         terminator: &mir::Terminator<'tcx>,
 376         cond: &mir::Operand<'tcx>,
 377         expected: bool,
 378         msg: &mir::AssertMessage<'tcx>,
 379         target: mir::BasicBlock,
 380         cleanup: Option<mir::BasicBlock>,
 381     ) {
 382         let span = terminator.source_info.span;
 383         let cond = self.codegen_operand(&mut bx, cond).immediate();
 384         let mut const_cond = bx.const_to_opt_u128(cond, false).map(|c| c == 1);
 385
 386         // This case can currently arise only from functions marked
 387         // with #[rustc_inherit_overflow_checks] and inlined from
 388         // another crate (mostly core::num generic/#[inline] fns),
 389         // while the current crate doesn't use overflow checks.
 390         // NOTE: Unlike binops, negation doesn't have its own
 391         // checked operation, just a comparison with the minimum
 392         // value, so we have to check for the assert message.
 393         if !bx.check_overflow() {
 394             if let PanicInfo::OverflowNeg = *msg {
 395                 const_cond = Some(expected);
 396             }
 397         }
 398
 399         // Don't codegen the panic block if success if known.
 400         if const_cond == Some(expected) {
 401             helper.maybe_sideeffect(self.mir, &mut bx, &[target]);
 402             helper.funclet_br(self, &mut bx, target);
 403             return;
 404         }
 405
 406         // Pass the condition through llvm.expect for branch hinting.
 407         let cond = bx.expect(cond, expected);
 408
 409         // Create the failure block and the conditional branch to it.
 410         let lltarget = helper.llblock(self, target);
 411         let panic_block = self.new_block("panic");
 412         helper.maybe_sideeffect(self.mir, &mut bx, &[target]);
 413         if expected {
 414             bx.cond_br(cond, lltarget, panic_block.llbb());
 415         } else {
 416             bx.cond_br(cond, panic_block.llbb(), lltarget);
 417         }
 418
 419         // After this point, bx is the block for the call to panic.
 420         bx = panic_block;
 421         self.set_debug_loc(&mut bx, terminator.source_info);
 422
 423         // Get the location information.
 424         let loc = bx.sess().source_map().lookup_char_pos(span.lo());
 425         let filename = Symbol::intern(&loc.file.name.to_string());
 426         let line = bx.const_u32(loc.line as u32);
 427         let col = bx.const_u32(loc.col.to_usize() as u32 + 1);
 428
 429         // Put together the arguments to the panic entry point.
 430         let (lang_item, args) = match msg {
 431             PanicInfo::BoundsCheck { ref len, ref index } => {
 432                 let len = self.codegen_operand(&mut bx, len).immediate();
 433                 let index = self.codegen_operand(&mut bx, index).immediate();
 434
 435                 let file_line_col = bx.static_panic_msg(
 436                     None,
 437                     filename,
 438                     line,
 439                     col,
 440                     "panic_bounds_check_loc",
 441                 );
 442                 (lang_items::PanicBoundsCheckFnLangItem,
 443                     vec![file_line_col, index, len])
 444             }
 445             _ => {
 446                 let msg_str = Symbol::intern(msg.description());
 447                 let msg_file_line_col = bx.static_panic_msg(
 448                     Some(msg_str),
 449                     filename,
 450                     line,
 451                     col,
 452                     "panic_loc",
 453                 );
 454                 (lang_items::PanicFnLangItem,
 455                     vec![msg_file_line_col])
 456             }
 457         };
 458
 459         // Obtain the panic entry point.
 460         let def_id = common::langcall(bx.tcx(), Some(span), "", lang_item);
 461         let instance = ty::Instance::mono(bx.tcx(), def_id);
 462         let fn_ty = FnType::of_instance(&bx, instance);
 463         let llfn = bx.get_fn_addr(instance);
 464
 465         // Codegen the actual panic invoke/call.
 466         helper.do_call(self, &mut bx, fn_ty, llfn, &args, None, cleanup);
 467     }
 468
 469     fn codegen_call_terminator<'b>(
 470         &mut self,
 471         helper: TerminatorCodegenHelper<'b, 'tcx>,
 472         mut bx: Bx,
 473         terminator: &mir::Terminator<'tcx>,
 474         func: &mir::Operand<'tcx>,
 475         args: &Vec<mir::Operand<'tcx>>,
 476         destination: &Option<(mir::Place<'tcx>, mir::BasicBlock)>,
 477         cleanup: Option<mir::BasicBlock>,
 478     ) {
 479         let span = terminator.source_info.span;
 480         // Create the callee. This is a fn ptr or zero-sized and hence a kind of scalar.
 481         let callee = self.codegen_operand(&mut bx, func);
 482
 483         let (instance, mut llfn) = match callee.layout.ty.kind {
 484             ty::FnDef(def_id, substs) => {
 485                 (Some(ty::Instance::resolve(bx.tcx(),
 486                                             ty::ParamEnv::reveal_all(),
 487                                             def_id,
 488                                             substs).unwrap()),
 489                  None)
 490             }
 491             ty::FnPtr(_) => {
 492                 (None, Some(callee.immediate()))
 493             }
 494             _ => bug!("{} is not callable", callee.layout.ty),
 495         };
 496         let def = instance.map(|i| i.def);
 497         let sig = callee.layout.ty.fn_sig(bx.tcx());
 498         let sig = bx.tcx().normalize_erasing_late_bound_regions(
 499             ty::ParamEnv::reveal_all(),
 500             &sig,
 501         );
 502         let abi = sig.abi;
 503
 504         // Handle intrinsics old codegen wants Expr's for, ourselves.
 505         let intrinsic = match def {
 506             Some(ty::InstanceDef::Intrinsic(def_id)) =>
 507                 Some(bx.tcx().item_name(def_id).as_str()),
 508             _ => None
 509         };
 510         let intrinsic = intrinsic.as_ref().map(|s| &s[..]);
 511
 512         if intrinsic == Some("transmute") {
 513             if let Some(destination_ref) = destination.as_ref() {
 514                 let &(ref dest, target) = destination_ref;
 515                 self.codegen_transmute(&mut bx, &args[0], dest);
 516                 helper.maybe_sideeffect(self.mir, &mut bx, &[target]);
 517                 helper.funclet_br(self, &mut bx, target);
 518             } else {
 519                 // If we are trying to transmute to an uninhabited type,
 520                 // it is likely there is no allotted destination. In fact,
 521                 // transmuting to an uninhabited type is UB, which means
 522                 // we can do what we like. Here, we declare that transmuting
 523                 // into an uninhabited type is impossible, so anything following
 524                 // it must be unreachable.
 525                 assert_eq!(bx.layout_of(sig.output()).abi, layout::Abi::Uninhabited);
 526                 bx.unreachable();
 527             }
 528             return;
 529         }
 530
 531         let extra_args = &args[sig.inputs().len()..];
 532         let extra_args = extra_args.iter().map(|op_arg| {
 533             let op_ty = op_arg.ty(self.mir, bx.tcx());
 534             self.monomorphize(&op_ty)
 535         }).collect::<Vec<_>>();
 536
 537         let fn_ty = match def {
 538             Some(ty::InstanceDef::Virtual(..)) => {
 539                 FnType::new_vtable(&bx, sig, &extra_args)
 540             }
 541             Some(ty::InstanceDef::DropGlue(_, None)) => {
 542                 // Empty drop glue; a no-op.
 543                 let &(_, target) = destination.as_ref().unwrap();
 544                 helper.maybe_sideeffect(self.mir, &mut bx, &[target]);
 545                 helper.funclet_br(self, &mut bx, target);
 546                 return;
 547             }
 548             _ => FnType::new(&bx, sig, &extra_args)
 549         };
 550
 551         // Emit a panic or a no-op for `panic_if_uninhabited`.
 552         if intrinsic == Some("panic_if_uninhabited") {
 553             let ty = instance.unwrap().substs.type_at(0);
 554             let layout = bx.layout_of(ty);
 555             if layout.abi.is_uninhabited() {
 556                 let loc = bx.sess().source_map().lookup_char_pos(span.lo());
 557                 let filename = Symbol::intern(&loc.file.name.to_string());
 558                 let line = bx.const_u32(loc.line as u32);
 559                 let col = bx.const_u32(loc.col.to_usize() as u32 + 1);
 560
 561                 let str = format!(
 562                     "Attempted to instantiate uninhabited type {}",
 563                     ty
 564                 );
 565                 let msg_str = Symbol::intern(&str);
 566                 let msg_file_line_col = bx.static_panic_msg(
 567                     Some(msg_str),
 568                     filename,
 569                     line,
 570                     col,
 571                     "panic_loc",
 572                 );
 573
 574                 // Obtain the panic entry point.
 575                 let def_id =
 576                     common::langcall(bx.tcx(), Some(span), "", lang_items::PanicFnLangItem);
 577                 let instance = ty::Instance::mono(bx.tcx(), def_id);
 578                 let fn_ty = FnType::of_instance(&bx, instance);
 579                 let llfn = bx.get_fn_addr(instance);
 580
 581                 if let Some((_, target)) = destination.as_ref() {
 582                     helper.maybe_sideeffect(self.mir, &mut bx, &[*target]);
 583                 }
 584                 // Codegen the actual panic invoke/call.
 585                 helper.do_call(
 586                     self,
 587                     &mut bx,
 588                     fn_ty,
 589                     llfn,
 590                     &[msg_file_line_col],
 591                     destination.as_ref().map(|(_, bb)| (ReturnDest::Nothing, *bb)),
 592                     cleanup,
 593                 );
 594             } else {
 595                 // a NOP
 596                 let target = destination.as_ref().unwrap().1;
 597                 helper.maybe_sideeffect(self.mir, &mut bx, &[target]);
 598                 helper.funclet_br(self, &mut bx, target);
 599             }
 600             return;
 601         }
 602
 603         // The arguments we'll be passing. Plus one to account for outptr, if used.
 604         let arg_count = fn_ty.args.len() + fn_ty.ret.is_indirect() as usize;
 605         let mut llargs = Vec::with_capacity(arg_count);
 606
 607         // Prepare the return value destination
 608         let ret_dest = if let Some((ref dest, _)) = *destination {
 609             let is_intrinsic = intrinsic.is_some();
 610             self.make_return_dest(&mut bx, dest, &fn_ty.ret, &mut llargs,
 611                                   is_intrinsic)
 612         } else {
 613             ReturnDest::Nothing
 614         };
 615
 616         if intrinsic.is_some() && intrinsic != Some("drop_in_place") {
 617             let dest = match ret_dest {
 618                 _ if fn_ty.ret.is_indirect() => llargs[0],
 619                 ReturnDest::Nothing =>
 620                     bx.const_undef(bx.type_ptr_to(bx.memory_ty(&fn_ty.ret))),
 621                 ReturnDest::IndirectOperand(dst, _) | ReturnDest::Store(dst) =>
 622                     dst.llval,
 623                 ReturnDest::DirectOperand(_) =>
 624                     bug!("Cannot use direct operand with an intrinsic call"),
 625             };
 626
 627             let args: Vec<_> = args.iter().enumerate().map(|(i, arg)| {
 628                 // The indices passed to simd_shuffle* in the
 629                 // third argument must be constant. This is
 630                 // checked by const-qualification, which also
 631                 // promotes any complex rvalues to constants.
 632                 if i == 2 && intrinsic.unwrap().starts_with("simd_shuffle") {
 633                     match *arg {
 634                         // The shuffle array argument is usually not an explicit constant,
 635                         // but specified directly in the code. This means it gets promoted
 636                         // and we can then extract the value by evaluating the promoted.
 637                         mir::Operand::Copy(
 638                             Place {
 639                                 base: PlaceBase::Static(box Static {
 640                                     kind: StaticKind::Promoted(promoted, _),
 641                                     ty,
 642                                     def_id: _,
 643                                 }),
 644                                 projection: box [],
 645                             }
 646                         ) |
 647                         mir::Operand::Move(
 648                             Place {
 649                                 base: PlaceBase::Static(box Static {
 650                                     kind: StaticKind::Promoted(promoted, _),
 651                                     ty,
 652                                     def_id: _,
 653                                 }),
 654                                 projection: box [],
 655                             }
 656                         ) => {
 657                             let param_env = ty::ParamEnv::reveal_all();
 658                             let cid = mir::interpret::GlobalId {
 659                                 instance: self.instance,
 660                                 promoted: Some(promoted),
 661                             };
 662                             let c = bx.tcx().const_eval(param_env.and(cid));
 663                             let (llval, ty) = self.simd_shuffle_indices(
 664                                 &bx,
 665                                 terminator.source_info.span,
 666                                 ty,
 667                                 c,
 668                             );
 669                             return OperandRef {
 670                                 val: Immediate(llval),
 671                                 layout: bx.layout_of(ty),
 672                             };
 673
 674                         }
 675                         mir::Operand::Copy(_) |
 676                         mir::Operand::Move(_) => {
 677                             span_bug!(span, "shuffle indices must be constant");
 678                         }
 679                         mir::Operand::Constant(ref constant) => {
 680                             let c = self.eval_mir_constant(constant);
 681                             let (llval, ty) = self.simd_shuffle_indices(
 682                                 &bx,
 683                                 constant.span,
 684                                 constant.literal.ty,
 685                                 c,
 686                             );
 687                             return OperandRef {
 688                                 val: Immediate(llval),
 689                                 layout: bx.layout_of(ty)
 690                             };
 691                         }
 692                     }
 693                 }
 694
 695                 self.codegen_operand(&mut bx, arg)
 696             }).collect();
 697
 698
 699             bx.codegen_intrinsic_call(*instance.as_ref().unwrap(), &fn_ty, &args, dest,
 700                                       terminator.source_info.span);
 701
 702             if let ReturnDest::IndirectOperand(dst, _) = ret_dest {
 703                 self.store_return(&mut bx, ret_dest, &fn_ty.ret, dst.llval);
 704             }
 705
 706             if let Some((_, target)) = *destination {
 707                 helper.maybe_sideeffect(self.mir, &mut bx, &[target]);
 708                 helper.funclet_br(self, &mut bx, target);
 709             } else {
 710                 bx.unreachable();
 711             }
 712
 713             return;
 714         }
 715
 716         // Split the rust-call tupled arguments off.
 717         let (first_args, untuple) = if abi == Abi::RustCall && !args.is_empty() {
 718             let (tup, args) = args.split_last().unwrap();
 719             (args, Some(tup))
 720         } else {
 721             (&args[..], None)
 722         };
 723
 724         'make_args: for (i, arg) in first_args.iter().enumerate() {
 725             let mut op = self.codegen_operand(&mut bx, arg);
 726
 727             if let (0, Some(ty::InstanceDef::Virtual(_, idx))) = (i, def) {
 728                 if let Pair(..) = op.val {
 729                     // In the case of Rc<Self>, we need to explicitly pass a
 730                     // *mut RcBox<Self> with a Scalar (not ScalarPair) ABI. This is a hack
 731                     // that is understood elsewhere in the compiler as a method on
 732                     // `dyn Trait`.
 733                     // To get a `*mut RcBox<Self>`, we just keep unwrapping newtypes until
 734                     // we get a value of a built-in pointer type
 735                     'descend_newtypes: while !op.layout.ty.is_unsafe_ptr()
 736                                     && !op.layout.ty.is_region_ptr()
 737                     {
 738                         'iter_fields: for i in 0..op.layout.fields.count() {
 739                             let field = op.extract_field(&mut bx, i);
 740                             if !field.layout.is_zst() {
 741                                 // we found the one non-zero-sized field that is allowed
 742                                 // now find *its* non-zero-sized field, or stop if it's a
 743                                 // pointer
 744                                 op = field;
 745                                 continue 'descend_newtypes
 746                             }
 747                         }
 748
 749                         span_bug!(span, "receiver has no non-zero-sized fields {:?}", op);
 750                     }
 751
 752                     // now that we have `*dyn Trait` or `&dyn Trait`, split it up into its
 753                     // data pointer and vtable. Look up the method in the vtable, and pass
 754                     // the data pointer as the first argument
 755                     match op.val {
 756                         Pair(data_ptr, meta) => {
 757                             llfn = Some(meth::VirtualIndex::from_index(idx)
 758                                 .get_fn(&mut bx, meta, &fn_ty));
 759                             llargs.push(data_ptr);
 760                             continue 'make_args
 761                         }
 762                         other => bug!("expected a Pair, got {:?}", other),
 763                     }
 764                 } else if let Ref(data_ptr, Some(meta), _) = op.val {
 765                     // by-value dynamic dispatch
 766                     llfn = Some(meth::VirtualIndex::from_index(idx)
 767                         .get_fn(&mut bx, meta, &fn_ty));
 768                     llargs.push(data_ptr);
 769                     continue;
 770                 } else {
 771                     span_bug!(span, "can't codegen a virtual call on {:?}", op);
 772                 }
 773             }
 774
 775             // The callee needs to own the argument memory if we pass it
 776             // by-ref, so make a local copy of non-immediate constants.
 777             match (arg, op.val) {
 778                 (&mir::Operand::Copy(_), Ref(_, None, _)) |
 779                 (&mir::Operand::Constant(_), Ref(_, None, _)) => {
 780                     let tmp = PlaceRef::alloca(&mut bx, op.layout);
 781                     op.val.store(&mut bx, tmp);
 782                     op.val = Ref(tmp.llval, None, tmp.align);
 783                 }
 784                 _ => {}
 785             }
 786
 787             self.codegen_argument(&mut bx, op, &mut llargs, &fn_ty.args[i]);
 788         }
 789         if let Some(tup) = untuple {
 790             self.codegen_arguments_untupled(&mut bx, tup, &mut llargs,
 791                 &fn_ty.args[first_args.len()..])
 792         }
 793
 794         let fn_ptr = match (llfn, instance) {
 795             (Some(llfn), _) => llfn,
 796             (None, Some(instance)) => bx.get_fn_addr(instance),
 797             _ => span_bug!(span, "no llfn for call"),
 798         };
 799
 800         if let Some((_, target)) = destination.as_ref() {
 801             helper.maybe_sideeffect(self.mir, &mut bx, &[*target]);
 802         }
 803         helper.do_call(self, &mut bx, fn_ty, fn_ptr, &llargs,
 804                        destination.as_ref().map(|&(_, target)| (ret_dest, target)),
 805                        cleanup);
 806     }
 807 }
 808
 809 impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
 810     pub fn codegen_block(
 811         &mut self,
 812         bb: mir::BasicBlock,
 813     ) {
 814         let mut bx = self.build_block(bb);
 815         let data = &self.mir[bb];
 816
 817         debug!("codegen_block({:?}={:?})", bb, data);
 818
 819         for statement in &data.statements {
 820             bx = self.codegen_statement(bx, statement);
 821         }
 822
 823         self.codegen_terminator(bx, bb, data.terminator());
 824     }
 825
 826     fn codegen_terminator(
 827         &mut self,
 828         mut bx: Bx,
 829         bb: mir::BasicBlock,
 830         terminator: &mir::Terminator<'tcx>
 831     ) {
 832         debug!("codegen_terminator: {:?}", terminator);
 833
 834         // Create the cleanup bundle, if needed.
 835         let funclet_bb = self.cleanup_kinds[bb].funclet_bb(bb);
 836         let helper = TerminatorCodegenHelper {
 837             bb: &bb, terminator, funclet_bb
 838         };
 839
 840         self.set_debug_loc(&mut bx, terminator.source_info);
 841         match terminator.kind {
 842             mir::TerminatorKind::Resume => {
 843                 self.codegen_resume_terminator(helper, bx)
 844             }
 845
 846             mir::TerminatorKind::Abort => {
 847                 bx.abort();
 848                 bx.unreachable();
 849             }
 850
 851             mir::TerminatorKind::Goto { target } => {
 852                 helper.maybe_sideeffect(self.mir, &mut bx, &[target]);
 853                 helper.funclet_br(self, &mut bx, target);
 854             }
 855
 856             mir::TerminatorKind::SwitchInt {
 857                 ref discr, switch_ty, ref values, ref targets
 858             } => {
 859                 self.codegen_switchint_terminator(helper, bx, discr, switch_ty,
 860                                                   values, targets);
 861             }
 862
 863             mir::TerminatorKind::Return => {
 864                 self.codegen_return_terminator(bx);
 865             }
 866
 867             mir::TerminatorKind::Unreachable => {
 868                 bx.unreachable();
 869             }
 870
 871             mir::TerminatorKind::Drop { ref location, target, unwind } => {
 872                 self.codegen_drop_terminator(helper, bx, location, target, unwind);
 873             }
 874
 875             mir::TerminatorKind::Assert { ref cond, expected, ref msg, target, cleanup } => {
 876                 self.codegen_assert_terminator(helper, bx, terminator, cond,
 877                                                expected, msg, target, cleanup);
 878             }
 879
 880             mir::TerminatorKind::DropAndReplace { .. } => {
 881                 bug!("undesugared DropAndReplace in codegen: {:?}", terminator);
 882             }
 883
 884             mir::TerminatorKind::Call {
 885                 ref func,
 886                 ref args,
 887                 ref destination,
 888                 cleanup,
 889                 from_hir_call: _
 890             } => {
 891                 self.codegen_call_terminator(helper, bx, terminator, func,
 892                                              args, destination, cleanup);
 893             }
 894             mir::TerminatorKind::GeneratorDrop |
 895             mir::TerminatorKind::Yield { .. } => bug!("generator ops in codegen"),
 896             mir::TerminatorKind::FalseEdges { .. } |
 897             mir::TerminatorKind::FalseUnwind { .. } => bug!("borrowck false edges in codegen"),
 898         }
 899     }
 900
 901     fn codegen_argument(
 902         &mut self,
 903         bx: &mut Bx,
 904         op: OperandRef<'tcx, Bx::Value>,
 905         llargs: &mut Vec<Bx::Value>,
 906         arg: &ArgType<'tcx, Ty<'tcx>>
 907     ) {
 908         // Fill padding with undef value, where applicable.
 909         if let Some(ty) = arg.pad {
 910             llargs.push(bx.const_undef(bx.reg_backend_type(&ty)))
 911         }
 912
 913         if arg.is_ignore() {
 914             return;
 915         }
 916
 917         if let PassMode::Pair(..) = arg.mode {
 918             match op.val {
 919                 Pair(a, b) => {
 920                     llargs.push(a);
 921                     llargs.push(b);
 922                     return;
 923                 }
 924                 _ => bug!("codegen_argument: {:?} invalid for pair argument", op)
 925             }
 926         } else if arg.is_unsized_indirect() {
 927             match op.val {
 928                 Ref(a, Some(b), _) => {
 929                     llargs.push(a);
 930                     llargs.push(b);
 931                     return;
 932                 }
 933                 _ => bug!("codegen_argument: {:?} invalid for unsized indirect argument", op)
 934             }
 935         }
 936
 937         // Force by-ref if we have to load through a cast pointer.
 938         let (mut llval, align, by_ref) = match op.val {
 939             Immediate(_) | Pair(..) => {
 940                 match arg.mode {
 941                     PassMode::Indirect(..) | PassMode::Cast(_) => {
 942                         let scratch = PlaceRef::alloca(bx, arg.layout);
 943                         op.val.store(bx, scratch);
 944                         (scratch.llval, scratch.align, true)
 945                     }
 946                     _ => {
 947                         (op.immediate_or_packed_pair(bx), arg.layout.align.abi, false)
 948                     }
 949                 }
 950             }
 951             Ref(llval, _, align) => {
 952                 if arg.is_indirect() && align < arg.layout.align.abi {
 953                     // `foo(packed.large_field)`. We can't pass the (unaligned) field directly. I
 954                     // think that ATM (Rust 1.16) we only pass temporaries, but we shouldn't
 955                     // have scary latent bugs around.
 956
 957                     let scratch = PlaceRef::alloca(bx, arg.layout);
 958                     base::memcpy_ty(bx, scratch.llval, scratch.align, llval, align,
 959                                     op.layout, MemFlags::empty());
 960                     (scratch.llval, scratch.align, true)
 961                 } else {
 962                     (llval, align, true)
 963                 }
 964             }
 965         };
 966
 967         if by_ref && !arg.is_indirect() {
 968             // Have to load the argument, maybe while casting it.
 969             if let PassMode::Cast(ty) = arg.mode {
 970                 let addr = bx.pointercast(llval, bx.type_ptr_to(
 971                     bx.cast_backend_type(&ty))
 972                 );
 973                 llval = bx.load(addr, align.min(arg.layout.align.abi));
 974             } else {
 975                 // We can't use `PlaceRef::load` here because the argument
 976                 // may have a type we don't treat as immediate, but the ABI
 977                 // used for this call is passing it by-value. In that case,
 978                 // the load would just produce `OperandValue::Ref` instead
 979                 // of the `OperandValue::Immediate` we need for the call.
 980                 llval = bx.load(llval, align);
 981                 if let layout::Abi::Scalar(ref scalar) = arg.layout.abi {
 982                     if scalar.is_bool() {
 983                         bx.range_metadata(llval, 0..2);
 984                     }
 985                 }
 986                 // We store bools as `i8` so we need to truncate to `i1`.
 987                 llval = base::to_immediate(bx, llval, arg.layout);
 988             }
 989         }
 990
 991         llargs.push(llval);
 992     }
 993
 994     fn codegen_arguments_untupled(
 995         &mut self,
 996         bx: &mut Bx,
 997         operand: &mir::Operand<'tcx>,
 998         llargs: &mut Vec<Bx::Value>,
 999         args: &[ArgType<'tcx, Ty<'tcx>>]
1000     ) {
1001         let tuple = self.codegen_operand(bx, operand);
1002
1003         // Handle both by-ref and immediate tuples.
1004         if let Ref(llval, None, align) = tuple.val {
1005             let tuple_ptr = PlaceRef::new_sized_aligned(llval, tuple.layout, align);
1006             for i in 0..tuple.layout.fields.count() {
1007                 let field_ptr = tuple_ptr.project_field(bx, i);
1008                 let field = bx.load_operand(field_ptr);
1009                 self.codegen_argument(bx, field, llargs, &args[i]);
1010             }
1011         } else if let Ref(_, Some(_), _) = tuple.val {
1012             bug!("closure arguments must be sized")
1013         } else {
1014             // If the tuple is immediate, the elements are as well.
1015             for i in 0..tuple.layout.fields.count() {
1016                 let op = tuple.extract_field(bx, i);
1017                 self.codegen_argument(bx, op, llargs, &args[i]);
1018             }
1019         }
1020     }
1021
1022     fn get_personality_slot(
1023         &mut self,
1024         bx: &mut Bx
1025     ) -> PlaceRef<'tcx, Bx::Value> {
1026         let cx = bx.cx();
1027         if let Some(slot) = self.personality_slot {
1028             slot
1029         } else {
1030             let layout = cx.layout_of(cx.tcx().intern_tup(&[
1031                 cx.tcx().mk_mut_ptr(cx.tcx().types.u8),
1032                 cx.tcx().types.i32
1033             ]));
1034             let slot = PlaceRef::alloca(bx, layout);
1035             self.personality_slot = Some(slot);
1036             slot
1037         }
1038     }
1039
1040     /// Returns the landing-pad wrapper around the given basic block.
1041     ///
1042     /// No-op in MSVC SEH scheme.
1043     fn landing_pad_to(
1044         &mut self,
1045         target_bb: mir::BasicBlock
1046     ) -> Bx::BasicBlock {
1047         if let Some(block) = self.landing_pads[target_bb] {
1048             return block;
1049         }
1050
1051         let block = self.blocks[target_bb];
1052         let landing_pad = self.landing_pad_uncached(block);
1053         self.landing_pads[target_bb] = Some(landing_pad);
1054         landing_pad
1055     }
1056
1057     fn landing_pad_uncached(
1058         &mut self,
1059         target_bb: Bx::BasicBlock
1060     ) -> Bx::BasicBlock {
1061         if base::wants_msvc_seh(self.cx.sess()) {
1062             span_bug!(self.mir.span, "landing pad was not inserted?")
1063         }
1064
1065         let mut bx = self.new_block("cleanup");
1066
1067         let llpersonality = self.cx.eh_personality();
1068         let llretty = self.landing_pad_type();
1069         let lp = bx.landing_pad(llretty, llpersonality, 1);
1070         bx.set_cleanup(lp);
1071
1072         let slot = self.get_personality_slot(&mut bx);
1073         slot.storage_live(&mut bx);
1074         Pair(bx.extract_value(lp, 0), bx.extract_value(lp, 1)).store(&mut bx, slot);
1075
1076         bx.br(target_bb);
1077         bx.llbb()
1078     }
1079
1080     fn landing_pad_type(&self) -> Bx::Type {
1081         let cx = self.cx;
1082         cx.type_struct(&[cx.type_i8p(), cx.type_i32()], false)
1083     }
1084
1085     fn unreachable_block(
1086         &mut self
1087     ) -> Bx::BasicBlock {
1088         self.unreachable_block.unwrap_or_else(|| {
1089             let mut bx = self.new_block("unreachable");
1090             bx.unreachable();
1091             self.unreachable_block = Some(bx.llbb());
1092             bx.llbb()
1093         })
1094     }
1095
1096     pub fn new_block(&self, name: &str) -> Bx {
1097         Bx::new_block(self.cx, self.llfn, name)
1098     }
1099
1100     pub fn build_block(
1101         &self,
1102         bb: mir::BasicBlock
1103     ) -> Bx {
1104         let mut bx = Bx::with_cx(self.cx);
1105         bx.position_at_end(self.blocks[bb]);
1106         bx
1107     }
1108
1109     fn make_return_dest(
1110         &mut self,
1111         bx: &mut Bx,
1112         dest: &mir::Place<'tcx>,
1113         fn_ret: &ArgType<'tcx, Ty<'tcx>>,
1114         llargs: &mut Vec<Bx::Value>, is_intrinsic: bool
1115     ) -> ReturnDest<'tcx, Bx::Value> {
1116         // If the return is ignored, we can just return a do-nothing `ReturnDest`.
1117         if fn_ret.is_ignore() {
1118             return ReturnDest::Nothing;
1119         }
1120         let dest = if let mir::Place {
1121             base: mir::PlaceBase::Local(index),
1122             projection: box [],
1123         } = *dest {
1124             match self.locals[index] {
1125                 LocalRef::Place(dest) => dest,
1126                 LocalRef::UnsizedPlace(_) => bug!("return type must be sized"),
1127                 LocalRef::Operand(None) => {
1128                     // Handle temporary places, specifically `Operand` ones, as
1129                     // they don't have `alloca`s.
1130                     return if fn_ret.is_indirect() {
1131                         // Odd, but possible, case, we have an operand temporary,
1132                         // but the calling convention has an indirect return.
1133                         let tmp = PlaceRef::alloca(bx, fn_ret.layout);
1134                         tmp.storage_live(bx);
1135                         llargs.push(tmp.llval);
1136                         ReturnDest::IndirectOperand(tmp, index)
1137                     } else if is_intrinsic {
1138                         // Currently, intrinsics always need a location to store
1139                         // the result, so we create a temporary `alloca` for the
1140                         // result.
1141                         let tmp = PlaceRef::alloca(bx, fn_ret.layout);
1142                         tmp.storage_live(bx);
1143                         ReturnDest::IndirectOperand(tmp, index)
1144                     } else {
1145                         ReturnDest::DirectOperand(index)
1146                     };
1147                 }
1148                 LocalRef::Operand(Some(_)) => {
1149                     bug!("place local already assigned to");
1150                 }
1151             }
1152         } else {
1153             self.codegen_place(bx, &mir::PlaceRef {
1154                 base: &dest.base,
1155                 projection: &dest.projection,
1156             })
1157         };
1158         if fn_ret.is_indirect() {
1159             if dest.align < dest.layout.align.abi {
1160                 // Currently, MIR code generation does not create calls
1161                 // that store directly to fields of packed structs (in
1162                 // fact, the calls it creates write only to temps).
1163                 //
1164                 // If someone changes that, please update this code path
1165                 // to create a temporary.
1166                 span_bug!(self.mir.span, "can't directly store to unaligned value");
1167             }
1168             llargs.push(dest.llval);
1169             ReturnDest::Nothing
1170         } else {
1171             ReturnDest::Store(dest)
1172         }
1173     }
1174
1175     fn codegen_transmute(
1176         &mut self,
1177         bx: &mut Bx,
1178         src: &mir::Operand<'tcx>,
1179         dst: &mir::Place<'tcx>
1180     ) {
1181         if let mir::Place {
1182             base: mir::PlaceBase::Local(index),
1183             projection: box [],
1184         } = *dst {
1185             match self.locals[index] {
1186                 LocalRef::Place(place) => self.codegen_transmute_into(bx, src, place),
1187                 LocalRef::UnsizedPlace(_) => bug!("transmute must not involve unsized locals"),
1188                 LocalRef::Operand(None) => {
1189                     let dst_layout = bx.layout_of(self.monomorphized_place_ty(&dst.as_ref()));
1190                     assert!(!dst_layout.ty.has_erasable_regions());
1191                     let place = PlaceRef::alloca(bx, dst_layout);
1192                     place.storage_live(bx);
1193                     self.codegen_transmute_into(bx, src, place);
1194                     let op = bx.load_operand(place);
1195                     place.storage_dead(bx);
1196                     self.locals[index] = LocalRef::Operand(Some(op));
1197                 }
1198                 LocalRef::Operand(Some(op)) => {
1199                     assert!(op.layout.is_zst(),
1200                             "assigning to initialized SSAtemp");
1201                 }
1202             }
1203         } else {
1204             let dst = self.codegen_place(bx, &dst.as_ref());
1205             self.codegen_transmute_into(bx, src, dst);
1206         }
1207     }
1208
1209     fn codegen_transmute_into(
1210         &mut self,
1211         bx: &mut Bx,
1212         src: &mir::Operand<'tcx>,
1213         dst: PlaceRef<'tcx, Bx::Value>
1214     ) {
1215         let src = self.codegen_operand(bx, src);
1216         let llty = bx.backend_type(src.layout);
1217         let cast_ptr = bx.pointercast(dst.llval, bx.type_ptr_to(llty));
1218         let align = src.layout.align.abi.min(dst.align);
1219         src.val.store(bx, PlaceRef::new_sized_aligned(cast_ptr, src.layout, align));
1220     }
1221
1222
1223     // Stores the return value of a function call into it's final location.
1224     fn store_return(
1225         &mut self,
1226         bx: &mut Bx,
1227         dest: ReturnDest<'tcx, Bx::Value>,
1228         ret_ty: &ArgType<'tcx, Ty<'tcx>>,
1229         llval: Bx::Value
1230     ) {
1231         use self::ReturnDest::*;
1232
1233         match dest {
1234             Nothing => (),
1235             Store(dst) => bx.store_arg_ty(&ret_ty, llval, dst),
1236             IndirectOperand(tmp, index) => {
1237                 let op = bx.load_operand(tmp);
1238                 tmp.storage_dead(bx);
1239                 self.locals[index] = LocalRef::Operand(Some(op));
1240             }
1241             DirectOperand(index) => {
1242                 // If there is a cast, we have to store and reload.
1243                 let op = if let PassMode::Cast(_) = ret_ty.mode {
1244                     let tmp = PlaceRef::alloca(bx, ret_ty.layout);
1245                     tmp.storage_live(bx);
1246                     bx.store_arg_ty(&ret_ty, llval, tmp);
1247                     let op = bx.load_operand(tmp);
1248                     tmp.storage_dead(bx);
1249                     op
1250                 } else {
1251                     OperandRef::from_immediate_or_packed_pair(bx, llval, ret_ty.layout)
1252                 };
1253                 self.locals[index] = LocalRef::Operand(Some(op));
1254             }
1255         }
1256     }
1257 }
1258
1259 enum ReturnDest<'tcx, V> {
1260     // Do nothing; the return value is indirect or ignored.
1261     Nothing,
1262     // Store the return value to the pointer.
1263     Store(PlaceRef<'tcx, V>),
1264     // Store an indirect return value to an operand local place.
1265     IndirectOperand(PlaceRef<'tcx, V>, mir::Local),
1266     // Store a direct return value to an operand local place.
1267     DirectOperand(mir::Local)
1268 }