src/librustc_trans/mir/block.rs

   1 // Copyright 2012-2014 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 use llvm::{self, ValueRef, BasicBlockRef};
  12 use rustc::middle::lang_items;
  13 use rustc::middle::const_val::{ConstEvalErr, ConstInt, ErrKind};
  14 use rustc::ty::{self, TypeFoldable};
  15 use rustc::ty::layout::{self, LayoutOf};
  16 use rustc::traits;
  17 use rustc::mir;
  18 use abi::{Abi, FnType, ArgType, PassMode};
  19 use base;
  20 use callee;
  21 use builder::Builder;
  22 use common::{self, C_bool, C_str_slice, C_struct, C_u32, C_undef};
  23 use consts;
  24 use meth;
  25 use monomorphize;
  26 use type_of::LayoutLlvmExt;
  27 use type_::Type;
  28
  29 use syntax::symbol::Symbol;
  30 use syntax_pos::Pos;
  31
  32 use super::{MirContext, LocalRef};
  33 use super::constant::Const;
  34 use super::lvalue::{Alignment, LvalueRef};
  35 use super::operand::OperandRef;
  36 use super::operand::OperandValue::{Pair, Ref, Immediate};
  37
  38 impl<'a, 'tcx> MirContext<'a, 'tcx> {
  39     pub fn trans_block(&mut self, bb: mir::BasicBlock) {
  40         let mut bcx = self.get_builder(bb);
  41         let data = &self.mir[bb];
  42
  43         debug!("trans_block({:?}={:?})", bb, data);
  44
  45         for statement in &data.statements {
  46             bcx = self.trans_statement(bcx, statement);
  47         }
  48
  49         self.trans_terminator(bcx, bb, data.terminator());
  50     }
  51
  52     fn trans_terminator(&mut self,
  53                         mut bcx: Builder<'a, 'tcx>,
  54                         bb: mir::BasicBlock,
  55                         terminator: &mir::Terminator<'tcx>)
  56     {
  57         debug!("trans_terminator: {:?}", terminator);
  58
  59         // Create the cleanup bundle, if needed.
  60         let tcx = bcx.tcx();
  61         let span = terminator.source_info.span;
  62         let funclet_bb = self.cleanup_kinds[bb].funclet_bb(bb);
  63         let funclet = funclet_bb.and_then(|funclet_bb| self.funclets[funclet_bb].as_ref());
  64
  65         let cleanup_pad = funclet.map(|lp| lp.cleanuppad());
  66         let cleanup_bundle = funclet.map(|l| l.bundle());
  67
  68         let lltarget = |this: &mut Self, target: mir::BasicBlock| {
  69             let lltarget = this.blocks[target];
  70             let target_funclet = this.cleanup_kinds[target].funclet_bb(target);
  71             match (funclet_bb, target_funclet) {
  72                 (None, None) => (lltarget, false),
  73                 (Some(f), Some(t_f))
  74                     if f == t_f || !base::wants_msvc_seh(tcx.sess)
  75                     => (lltarget, false),
  76                 (None, Some(_)) => {
  77                     // jump *into* cleanup - need a landing pad if GNU
  78                     (this.landing_pad_to(target), false)
  79                 }
  80                 (Some(_), None) => span_bug!(span, "{:?} - jump out of cleanup?", terminator),
  81                 (Some(_), Some(_)) => {
  82                     (this.landing_pad_to(target), true)
  83                 }
  84             }
  85         };
  86
  87         let llblock = |this: &mut Self, target: mir::BasicBlock| {
  88             let (lltarget, is_cleanupret) = lltarget(this, target);
  89             if is_cleanupret {
  90                 // MSVC cross-funclet jump - need a trampoline
  91
  92                 debug!("llblock: creating cleanup trampoline for {:?}", target);
  93                 let name = &format!("{:?}_cleanup_trampoline_{:?}", bb, target);
  94                 let trampoline = this.new_block(name);
  95                 trampoline.cleanup_ret(cleanup_pad.unwrap(), Some(lltarget));
  96                 trampoline.llbb()
  97             } else {
  98                 lltarget
  99             }
 100         };
 101
 102         let funclet_br = |this: &mut Self, bcx: Builder, target: mir::BasicBlock| {
 103             let (lltarget, is_cleanupret) = lltarget(this, target);
 104             if is_cleanupret {
 105                 // micro-optimization: generate a `ret` rather than a jump
 106                 // to a trampoline.
 107                 bcx.cleanup_ret(cleanup_pad.unwrap(), Some(lltarget));
 108             } else {
 109                 bcx.br(lltarget);
 110             }
 111         };
 112
 113         let do_call = |
 114             this: &mut Self,
 115             bcx: Builder<'a, 'tcx>,
 116             fn_ty: FnType<'tcx>,
 117             fn_ptr: ValueRef,
 118             llargs: &[ValueRef],
 119             destination: Option<(ReturnDest<'tcx>, mir::BasicBlock)>,
 120             cleanup: Option<mir::BasicBlock>
 121         | {
 122             if let Some(cleanup) = cleanup {
 123                 let ret_bcx = if let Some((_, target)) = destination {
 124                     this.blocks[target]
 125                 } else {
 126                     this.unreachable_block()
 127                 };
 128                 let invokeret = bcx.invoke(fn_ptr,
 129                                            &llargs,
 130                                            ret_bcx,
 131                                            llblock(this, cleanup),
 132                                            cleanup_bundle);
 133                 fn_ty.apply_attrs_callsite(invokeret);
 134
 135                 if let Some((ret_dest, target)) = destination {
 136                     let ret_bcx = this.get_builder(target);
 137                     this.set_debug_loc(&ret_bcx, terminator.source_info);
 138                     this.store_return(&ret_bcx, ret_dest, &fn_ty.ret, invokeret);
 139                 }
 140             } else {
 141                 let llret = bcx.call(fn_ptr, &llargs, cleanup_bundle);
 142                 fn_ty.apply_attrs_callsite(llret);
 143                 if this.mir[bb].is_cleanup {
 144                     // Cleanup is always the cold path. Don't inline
 145                     // drop glue. Also, when there is a deeply-nested
 146                     // struct, there are "symmetry" issues that cause
 147                     // exponential inlining - see issue #41696.
 148                     llvm::Attribute::NoInline.apply_callsite(llvm::AttributePlace::Function, llret);
 149                 }
 150
 151                 if let Some((ret_dest, target)) = destination {
 152                     this.store_return(&bcx, ret_dest, &fn_ty.ret, llret);
 153                     funclet_br(this, bcx, target);
 154                 } else {
 155                     bcx.unreachable();
 156                 }
 157             }
 158         };
 159
 160         self.set_debug_loc(&bcx, terminator.source_info);
 161         match terminator.kind {
 162             mir::TerminatorKind::Resume => {
 163                 if let Some(cleanup_pad) = cleanup_pad {
 164                     bcx.cleanup_ret(cleanup_pad, None);
 165                 } else {
 166                     let slot = self.get_personality_slot(&bcx);
 167                     let lp0 = slot.project_field(&bcx, 0).load(&bcx).immediate();
 168                     let lp1 = slot.project_field(&bcx, 1).load(&bcx).immediate();
 169                     slot.storage_dead(&bcx);
 170
 171                     if !bcx.sess().target.target.options.custom_unwind_resume {
 172                         let mut lp = C_undef(self.landing_pad_type());
 173                         lp = bcx.insert_value(lp, lp0, 0);
 174                         lp = bcx.insert_value(lp, lp1, 1);
 175                         bcx.resume(lp);
 176                     } else {
 177                         bcx.call(bcx.ccx.eh_unwind_resume(), &[lp0], cleanup_bundle);
 178                         bcx.unreachable();
 179                     }
 180                 }
 181             }
 182
 183             mir::TerminatorKind::Goto { target } => {
 184                 funclet_br(self, bcx, target);
 185             }
 186
 187             mir::TerminatorKind::SwitchInt { ref discr, switch_ty, ref values, ref targets } => {
 188                 let discr = self.trans_operand(&bcx, discr);
 189                 if switch_ty == bcx.tcx().types.bool {
 190                     let lltrue = llblock(self, targets[0]);
 191                     let llfalse = llblock(self, targets[1]);
 192                     if let [ConstInt::U8(0)] = values[..] {
 193                         bcx.cond_br(discr.immediate(), llfalse, lltrue);
 194                     } else {
 195                         bcx.cond_br(discr.immediate(), lltrue, llfalse);
 196                     }
 197                 } else {
 198                     let (otherwise, targets) = targets.split_last().unwrap();
 199                     let switch = bcx.switch(discr.immediate(),
 200                                             llblock(self, *otherwise), values.len());
 201                     for (value, target) in values.iter().zip(targets) {
 202                         let val = Const::from_constint(bcx.ccx, value);
 203                         let llbb = llblock(self, *target);
 204                         bcx.add_case(switch, val.llval, llbb)
 205                     }
 206                 }
 207             }
 208
 209             mir::TerminatorKind::Return => {
 210                 let llval = match self.fn_ty.ret.mode {
 211                     PassMode::Ignore | PassMode::Indirect(_) => {
 212                         bcx.ret_void();
 213                         return;
 214                     }
 215
 216                     PassMode::Direct(_) | PassMode::Pair(..) => {
 217                         let op = self.trans_consume(&bcx, &mir::Lvalue::Local(mir::RETURN_POINTER));
 218                         if let Ref(llval, align) = op.val {
 219                             bcx.load(llval, align.non_abi())
 220                         } else {
 221                             op.immediate_or_packed_pair(&bcx)
 222                         }
 223                     }
 224
 225                     PassMode::Cast(cast_ty) => {
 226                         let op = match self.locals[mir::RETURN_POINTER] {
 227                             LocalRef::Operand(Some(op)) => op,
 228                             LocalRef::Operand(None) => bug!("use of return before def"),
 229                             LocalRef::Lvalue(tr_lvalue) => {
 230                                 OperandRef {
 231                                     val: Ref(tr_lvalue.llval, tr_lvalue.alignment),
 232                                     layout: tr_lvalue.layout
 233                                 }
 234                             }
 235                         };
 236                         let llslot = match op.val {
 237                             Immediate(_) | Pair(..) => {
 238                                 let scratch = LvalueRef::alloca(&bcx, self.fn_ty.ret.layout, "ret");
 239                                 op.val.store(&bcx, scratch);
 240                                 scratch.llval
 241                             }
 242                             Ref(llval, align) => {
 243                                 assert_eq!(align, Alignment::AbiAligned,
 244                                            "return pointer is unaligned!");
 245                                 llval
 246                             }
 247                         };
 248                         bcx.load(
 249                             bcx.pointercast(llslot, cast_ty.llvm_type(bcx.ccx).ptr_to()),
 250                             Some(self.fn_ty.ret.layout.align))
 251                     }
 252                 };
 253                 bcx.ret(llval);
 254             }
 255
 256             mir::TerminatorKind::Unreachable => {
 257                 bcx.unreachable();
 258             }
 259
 260             mir::TerminatorKind::Drop { ref location, target, unwind } => {
 261                 let ty = location.ty(self.mir, bcx.tcx()).to_ty(bcx.tcx());
 262                 let ty = self.monomorphize(&ty);
 263                 let drop_fn = monomorphize::resolve_drop_in_place(bcx.ccx.tcx(), ty);
 264
 265                 if let ty::InstanceDef::DropGlue(_, None) = drop_fn.def {
 266                     // we don't actually need to drop anything.
 267                     funclet_br(self, bcx, target);
 268                     return
 269                 }
 270
 271                 let lvalue = self.trans_lvalue(&bcx, location);
 272                 let mut args: &[_] = &[lvalue.llval, lvalue.llextra];
 273                 args = &args[..1 + lvalue.has_extra() as usize];
 274                 let (drop_fn, fn_ty) = match ty.sty {
 275                     ty::TyDynamic(..) => {
 276                         let fn_ty = common::instance_ty(bcx.ccx.tcx(), &drop_fn);
 277                         let sig = common::ty_fn_sig(bcx.ccx, fn_ty);
 278                         let sig = bcx.tcx().erase_late_bound_regions_and_normalize(&sig);
 279                         let fn_ty = FnType::new_vtable(bcx.ccx, sig, &[]);
 280                         args = &args[..1];
 281                         (meth::DESTRUCTOR.get_fn(&bcx, lvalue.llextra, &fn_ty), fn_ty)
 282                     }
 283                     _ => {
 284                         (callee::get_fn(bcx.ccx, drop_fn),
 285                          FnType::of_instance(bcx.ccx, &drop_fn))
 286                     }
 287                 };
 288                 do_call(self, bcx, fn_ty, drop_fn, args,
 289                         Some((ReturnDest::Nothing, target)),
 290                         unwind);
 291             }
 292
 293             mir::TerminatorKind::Assert { ref cond, expected, ref msg, target, cleanup } => {
 294                 let cond = self.trans_operand(&bcx, cond).immediate();
 295                 let mut const_cond = common::const_to_opt_u128(cond, false).map(|c| c == 1);
 296
 297                 // This case can currently arise only from functions marked
 298                 // with #[rustc_inherit_overflow_checks] and inlined from
 299                 // another crate (mostly core::num generic/#[inline] fns),
 300                 // while the current crate doesn't use overflow checks.
 301                 // NOTE: Unlike binops, negation doesn't have its own
 302                 // checked operation, just a comparison with the minimum
 303                 // value, so we have to check for the assert message.
 304                 if !bcx.ccx.check_overflow() {
 305                     use rustc_const_math::ConstMathErr::Overflow;
 306                     use rustc_const_math::Op::Neg;
 307
 308                     if let mir::AssertMessage::Math(Overflow(Neg)) = *msg {
 309                         const_cond = Some(expected);
 310                     }
 311                 }
 312
 313                 // Don't translate the panic block if success if known.
 314                 if const_cond == Some(expected) {
 315                     funclet_br(self, bcx, target);
 316                     return;
 317                 }
 318
 319                 // Pass the condition through llvm.expect for branch hinting.
 320                 let expect = bcx.ccx.get_intrinsic(&"llvm.expect.i1");
 321                 let cond = bcx.call(expect, &[cond, C_bool(bcx.ccx, expected)], None);
 322
 323                 // Create the failure block and the conditional branch to it.
 324                 let lltarget = llblock(self, target);
 325                 let panic_block = self.new_block("panic");
 326                 if expected {
 327                     bcx.cond_br(cond, lltarget, panic_block.llbb());
 328                 } else {
 329                     bcx.cond_br(cond, panic_block.llbb(), lltarget);
 330                 }
 331
 332                 // After this point, bcx is the block for the call to panic.
 333                 bcx = panic_block;
 334                 self.set_debug_loc(&bcx, terminator.source_info);
 335
 336                 // Get the location information.
 337                 let loc = bcx.sess().codemap().lookup_char_pos(span.lo());
 338                 let filename = Symbol::intern(&loc.file.name).as_str();
 339                 let filename = C_str_slice(bcx.ccx, filename);
 340                 let line = C_u32(bcx.ccx, loc.line as u32);
 341                 let col = C_u32(bcx.ccx, loc.col.to_usize() as u32 + 1);
 342                 let align = tcx.data_layout.aggregate_align
 343                     .max(tcx.data_layout.i32_align)
 344                     .max(tcx.data_layout.pointer_align);
 345
 346                 // Put together the arguments to the panic entry point.
 347                 let (lang_item, args, const_err) = match *msg {
 348                     mir::AssertMessage::BoundsCheck { ref len, ref index } => {
 349                         let len = self.trans_operand(&mut bcx, len).immediate();
 350                         let index = self.trans_operand(&mut bcx, index).immediate();
 351
 352                         let const_err = common::const_to_opt_u128(len, false)
 353                             .and_then(|len| common::const_to_opt_u128(index, false)
 354                                 .map(|index| ErrKind::IndexOutOfBounds {
 355                                     len: len as u64,
 356                                     index: index as u64
 357                                 }));
 358
 359                         let file_line_col = C_struct(bcx.ccx, &[filename, line, col], false);
 360                         let file_line_col = consts::addr_of(bcx.ccx,
 361                                                             file_line_col,
 362                                                             align,
 363                                                             "panic_bounds_check_loc");
 364                         (lang_items::PanicBoundsCheckFnLangItem,
 365                          vec![file_line_col, index, len],
 366                          const_err)
 367                     }
 368                     mir::AssertMessage::Math(ref err) => {
 369                         let msg_str = Symbol::intern(err.description()).as_str();
 370                         let msg_str = C_str_slice(bcx.ccx, msg_str);
 371                         let msg_file_line_col = C_struct(bcx.ccx,
 372                                                      &[msg_str, filename, line, col],
 373                                                      false);
 374                         let msg_file_line_col = consts::addr_of(bcx.ccx,
 375                                                                 msg_file_line_col,
 376                                                                 align,
 377                                                                 "panic_loc");
 378                         (lang_items::PanicFnLangItem,
 379                          vec![msg_file_line_col],
 380                          Some(ErrKind::Math(err.clone())))
 381                     }
 382                     mir::AssertMessage::GeneratorResumedAfterReturn |
 383                     mir::AssertMessage::GeneratorResumedAfterPanic => {
 384                         let str = if let mir::AssertMessage::GeneratorResumedAfterReturn = *msg {
 385                             "generator resumed after completion"
 386                         } else {
 387                             "generator resumed after panicking"
 388                         };
 389                         let msg_str = Symbol::intern(str).as_str();
 390                         let msg_str = C_str_slice(bcx.ccx, msg_str);
 391                         let msg_file_line_col = C_struct(bcx.ccx,
 392                                                      &[msg_str, filename, line, col],
 393                                                      false);
 394                         let msg_file_line_col = consts::addr_of(bcx.ccx,
 395                                                                 msg_file_line_col,
 396                                                                 align,
 397                                                                 "panic_loc");
 398                         (lang_items::PanicFnLangItem,
 399                          vec![msg_file_line_col],
 400                          None)
 401                     }
 402                 };
 403
 404                 // If we know we always panic, and the error message
 405                 // is also constant, then we can produce a warning.
 406                 if const_cond == Some(!expected) {
 407                     if let Some(err) = const_err {
 408                         let err = ConstEvalErr{ span: span, kind: err };
 409                         let mut diag = bcx.tcx().sess.struct_span_warn(
 410                             span, "this expression will panic at run-time");
 411                         err.note(bcx.tcx(), span, "expression", &mut diag);
 412                         diag.emit();
 413                     }
 414                 }
 415
 416                 // Obtain the panic entry point.
 417                 let def_id = common::langcall(bcx.tcx(), Some(span), "", lang_item);
 418                 let instance = ty::Instance::mono(bcx.tcx(), def_id);
 419                 let fn_ty = FnType::of_instance(bcx.ccx, &instance);
 420                 let llfn = callee::get_fn(bcx.ccx, instance);
 421
 422                 // Translate the actual panic invoke/call.
 423                 do_call(self, bcx, fn_ty, llfn, &args, None, cleanup);
 424             }
 425
 426             mir::TerminatorKind::DropAndReplace { .. } => {
 427                 bug!("undesugared DropAndReplace in trans: {:?}", terminator);
 428             }
 429
 430             mir::TerminatorKind::Call { ref func, ref args, ref destination, cleanup } => {
 431                 // Create the callee. This is a fn ptr or zero-sized and hence a kind of scalar.
 432                 let callee = self.trans_operand(&bcx, func);
 433
 434                 let (instance, mut llfn) = match callee.layout.ty.sty {
 435                     ty::TyFnDef(def_id, substs) => {
 436                         (Some(ty::Instance::resolve(bcx.ccx.tcx(),
 437                                                     ty::ParamEnv::empty(traits::Reveal::All),
 438                                                     def_id,
 439                                                     substs).unwrap()),
 440                          None)
 441                     }
 442                     ty::TyFnPtr(_) => {
 443                         (None, Some(callee.immediate()))
 444                     }
 445                     _ => bug!("{} is not callable", callee.layout.ty)
 446                 };
 447                 let def = instance.map(|i| i.def);
 448                 let sig = callee.layout.ty.fn_sig(bcx.tcx());
 449                 let sig = bcx.tcx().erase_late_bound_regions_and_normalize(&sig);
 450                 let abi = sig.abi;
 451
 452                 // Handle intrinsics old trans wants Expr's for, ourselves.
 453                 let intrinsic = match def {
 454                     Some(ty::InstanceDef::Intrinsic(def_id))
 455                         => Some(bcx.tcx().item_name(def_id)),
 456                     _ => None
 457                 };
 458                 let intrinsic = intrinsic.as_ref().map(|s| &s[..]);
 459
 460                 if intrinsic == Some("transmute") {
 461                     let &(ref dest, target) = destination.as_ref().unwrap();
 462                     self.trans_transmute(&bcx, &args[0], dest);
 463                     funclet_br(self, bcx, target);
 464                     return;
 465                 }
 466
 467                 let extra_args = &args[sig.inputs().len()..];
 468                 let extra_args = extra_args.iter().map(|op_arg| {
 469                     let op_ty = op_arg.ty(self.mir, bcx.tcx());
 470                     self.monomorphize(&op_ty)
 471                 }).collect::<Vec<_>>();
 472
 473                 let fn_ty = match def {
 474                     Some(ty::InstanceDef::Virtual(..)) => {
 475                         FnType::new_vtable(bcx.ccx, sig, &extra_args)
 476                     }
 477                     Some(ty::InstanceDef::DropGlue(_, None)) => {
 478                         // empty drop glue - a nop.
 479                         let &(_, target) = destination.as_ref().unwrap();
 480                         funclet_br(self, bcx, target);
 481                         return;
 482                     }
 483                     _ => FnType::new(bcx.ccx, sig, &extra_args)
 484                 };
 485
 486                 // The arguments we'll be passing. Plus one to account for outptr, if used.
 487                 let arg_count = fn_ty.args.len() + fn_ty.ret.is_indirect() as usize;
 488                 let mut llargs = Vec::with_capacity(arg_count);
 489
 490                 // Prepare the return value destination
 491                 let ret_dest = if let Some((ref dest, _)) = *destination {
 492                     let is_intrinsic = intrinsic.is_some();
 493                     self.make_return_dest(&bcx, dest, &fn_ty.ret, &mut llargs,
 494                                           is_intrinsic)
 495                 } else {
 496                     ReturnDest::Nothing
 497                 };
 498
 499                 if intrinsic.is_some() && intrinsic != Some("drop_in_place") {
 500                     use intrinsic::trans_intrinsic_call;
 501
 502                     let dest = match ret_dest {
 503                         _ if fn_ty.ret.is_indirect() => llargs[0],
 504                         ReturnDest::Nothing => {
 505                             C_undef(fn_ty.ret.memory_ty(bcx.ccx).ptr_to())
 506                         }
 507                         ReturnDest::IndirectOperand(dst, _) |
 508                         ReturnDest::Store(dst) => dst.llval,
 509                         ReturnDest::DirectOperand(_) =>
 510                             bug!("Cannot use direct operand with an intrinsic call")
 511                     };
 512
 513                     let args: Vec<_> = args.iter().enumerate().map(|(i, arg)| {
 514                         // The indices passed to simd_shuffle* in the
 515                         // third argument must be constant. This is
 516                         // checked by const-qualification, which also
 517                         // promotes any complex rvalues to constants.
 518                         if i == 2 && intrinsic.unwrap().starts_with("simd_shuffle") {
 519                             match *arg {
 520                                 mir::Operand::Copy(_) |
 521                                 mir::Operand::Move(_) => {
 522                                     span_bug!(span, "shuffle indices must be constant");
 523                                 }
 524                                 mir::Operand::Constant(ref constant) => {
 525                                     let val = self.trans_constant(&bcx, constant);
 526                                     return OperandRef {
 527                                         val: Immediate(val.llval),
 528                                         layout: bcx.ccx.layout_of(val.ty)
 529                                     };
 530                                 }
 531                             }
 532                         }
 533
 534                         self.trans_operand(&bcx, arg)
 535                     }).collect();
 536
 537
 538                     let callee_ty = common::instance_ty(
 539                         bcx.ccx.tcx(), instance.as_ref().unwrap());
 540                     trans_intrinsic_call(&bcx, callee_ty, &fn_ty, &args, dest,
 541                                          terminator.source_info.span);
 542
 543                     if let ReturnDest::IndirectOperand(dst, _) = ret_dest {
 544                         self.store_return(&bcx, ret_dest, &fn_ty.ret, dst.llval);
 545                     }
 546
 547                     if let Some((_, target)) = *destination {
 548                         funclet_br(self, bcx, target);
 549                     } else {
 550                         bcx.unreachable();
 551                     }
 552
 553                     return;
 554                 }
 555
 556                 // Split the rust-call tupled arguments off.
 557                 let (first_args, untuple) = if abi == Abi::RustCall && !args.is_empty() {
 558                     let (tup, args) = args.split_last().unwrap();
 559                     (args, Some(tup))
 560                 } else {
 561                     (&args[..], None)
 562                 };
 563
 564                 for (i, arg) in first_args.iter().enumerate() {
 565                     let mut op = self.trans_operand(&bcx, arg);
 566                     if let (0, Some(ty::InstanceDef::Virtual(_, idx))) = (i, def) {
 567                         if let Pair(data_ptr, meta) = op.val {
 568                             llfn = Some(meth::VirtualIndex::from_index(idx)
 569                                 .get_fn(&bcx, meta, &fn_ty));
 570                             llargs.push(data_ptr);
 571                             continue;
 572                         }
 573                     }
 574
 575                     // The callee needs to own the argument memory if we pass it
 576                     // by-ref, so make a local copy of non-immediate constants.
 577                     match (arg, op.val) {
 578                         (&mir::Operand::Copy(_), Ref(..)) |
 579                         (&mir::Operand::Constant(_), Ref(..)) => {
 580                             let tmp = LvalueRef::alloca(&bcx, op.layout, "const");
 581                             op.val.store(&bcx, tmp);
 582                             op.val = Ref(tmp.llval, tmp.alignment);
 583                         }
 584                         _ => {}
 585                     }
 586
 587                     self.trans_argument(&bcx, op, &mut llargs, &fn_ty.args[i]);
 588                 }
 589                 if let Some(tup) = untuple {
 590                     self.trans_arguments_untupled(&bcx, tup, &mut llargs,
 591                         &fn_ty.args[first_args.len()..])
 592                 }
 593
 594                 let fn_ptr = match (llfn, instance) {
 595                     (Some(llfn), _) => llfn,
 596                     (None, Some(instance)) => callee::get_fn(bcx.ccx, instance),
 597                     _ => span_bug!(span, "no llfn for call"),
 598                 };
 599
 600                 do_call(self, bcx, fn_ty, fn_ptr, &llargs,
 601                         destination.as_ref().map(|&(_, target)| (ret_dest, target)),
 602                         cleanup);
 603             }
 604             mir::TerminatorKind::GeneratorDrop |
 605             mir::TerminatorKind::Yield { .. } |
 606             mir::TerminatorKind::FalseEdges { .. } => bug!("generator ops in trans"),
 607         }
 608     }
 609
 610     fn trans_argument(&mut self,
 611                       bcx: &Builder<'a, 'tcx>,
 612                       op: OperandRef<'tcx>,
 613                       llargs: &mut Vec<ValueRef>,
 614                       arg: &ArgType<'tcx>) {
 615         // Fill padding with undef value, where applicable.
 616         if let Some(ty) = arg.pad {
 617             llargs.push(C_undef(ty.llvm_type(bcx.ccx)));
 618         }
 619
 620         if arg.is_ignore() {
 621             return;
 622         }
 623
 624         if let PassMode::Pair(..) = arg.mode {
 625             match op.val {
 626                 Pair(a, b) => {
 627                     llargs.push(a);
 628                     llargs.push(b);
 629                     return;
 630                 }
 631                 _ => bug!("trans_argument: {:?} invalid for pair arugment", op)
 632             }
 633         }
 634
 635         // Force by-ref if we have to load through a cast pointer.
 636         let (mut llval, align, by_ref) = match op.val {
 637             Immediate(_) | Pair(..) => {
 638                 match arg.mode {
 639                     PassMode::Indirect(_) | PassMode::Cast(_) => {
 640                         let scratch = LvalueRef::alloca(bcx, arg.layout, "arg");
 641                         op.val.store(bcx, scratch);
 642                         (scratch.llval, Alignment::AbiAligned, true)
 643                     }
 644                     _ => {
 645                         (op.immediate_or_packed_pair(bcx), Alignment::AbiAligned, false)
 646                     }
 647                 }
 648             }
 649             Ref(llval, align @ Alignment::Packed(_)) if arg.is_indirect() => {
 650                 // `foo(packed.large_field)`. We can't pass the (unaligned) field directly. I
 651                 // think that ATM (Rust 1.16) we only pass temporaries, but we shouldn't
 652                 // have scary latent bugs around.
 653
 654                 let scratch = LvalueRef::alloca(bcx, arg.layout, "arg");
 655                 base::memcpy_ty(bcx, scratch.llval, llval, op.layout, align.non_abi());
 656                 (scratch.llval, Alignment::AbiAligned, true)
 657             }
 658             Ref(llval, align) => (llval, align, true)
 659         };
 660
 661         if by_ref && !arg.is_indirect() {
 662             // Have to load the argument, maybe while casting it.
 663             if let PassMode::Cast(ty) = arg.mode {
 664                 llval = bcx.load(bcx.pointercast(llval, ty.llvm_type(bcx.ccx).ptr_to()),
 665                                  (align | Alignment::Packed(arg.layout.align))
 666                                     .non_abi());
 667             } else {
 668                 // We can't use `LvalueRef::load` here because the argument
 669                 // may have a type we don't treat as immediate, but the ABI
 670                 // used for this call is passing it by-value. In that case,
 671                 // the load would just produce `OperandValue::Ref` instead
 672                 // of the `OperandValue::Immediate` we need for the call.
 673                 llval = bcx.load(llval, align.non_abi());
 674                 if let layout::Abi::Scalar(ref scalar) = arg.layout.abi {
 675                     if scalar.is_bool() {
 676                         bcx.range_metadata(llval, 0..2);
 677                     }
 678                 }
 679                 // We store bools as i8 so we need to truncate to i1.
 680                 llval = base::to_immediate(bcx, llval, arg.layout);
 681             }
 682         }
 683
 684         llargs.push(llval);
 685     }
 686
 687     fn trans_arguments_untupled(&mut self,
 688                                 bcx: &Builder<'a, 'tcx>,
 689                                 operand: &mir::Operand<'tcx>,
 690                                 llargs: &mut Vec<ValueRef>,
 691                                 args: &[ArgType<'tcx>]) {
 692         let tuple = self.trans_operand(bcx, operand);
 693
 694         // Handle both by-ref and immediate tuples.
 695         if let Ref(llval, align) = tuple.val {
 696             let tuple_ptr = LvalueRef::new_sized(llval, tuple.layout, align);
 697             for i in 0..tuple.layout.fields.count() {
 698                 let field_ptr = tuple_ptr.project_field(bcx, i);
 699                 self.trans_argument(bcx, field_ptr.load(bcx), llargs, &args[i]);
 700             }
 701         } else {
 702             // If the tuple is immediate, the elements are as well.
 703             for i in 0..tuple.layout.fields.count() {
 704                 let op = tuple.extract_field(bcx, i);
 705                 self.trans_argument(bcx, op, llargs, &args[i]);
 706             }
 707         }
 708     }
 709
 710     fn get_personality_slot(&mut self, bcx: &Builder<'a, 'tcx>) -> LvalueRef<'tcx> {
 711         let ccx = bcx.ccx;
 712         if let Some(slot) = self.personality_slot {
 713             slot
 714         } else {
 715             let layout = ccx.layout_of(ccx.tcx().intern_tup(&[
 716                 ccx.tcx().mk_mut_ptr(ccx.tcx().types.u8),
 717                 ccx.tcx().types.i32
 718             ], false));
 719             let slot = LvalueRef::alloca(bcx, layout, "personalityslot");
 720             self.personality_slot = Some(slot);
 721             slot
 722         }
 723     }
 724
 725     /// Return the landingpad wrapper around the given basic block
 726     ///
 727     /// No-op in MSVC SEH scheme.
 728     fn landing_pad_to(&mut self, target_bb: mir::BasicBlock) -> BasicBlockRef {
 729         if let Some(block) = self.landing_pads[target_bb] {
 730             return block;
 731         }
 732
 733         let block = self.blocks[target_bb];
 734         let landing_pad = self.landing_pad_uncached(block);
 735         self.landing_pads[target_bb] = Some(landing_pad);
 736         landing_pad
 737     }
 738
 739     fn landing_pad_uncached(&mut self, target_bb: BasicBlockRef) -> BasicBlockRef {
 740         if base::wants_msvc_seh(self.ccx.sess()) {
 741             span_bug!(self.mir.span, "landing pad was not inserted?")
 742         }
 743
 744         let bcx = self.new_block("cleanup");
 745
 746         let llpersonality = self.ccx.eh_personality();
 747         let llretty = self.landing_pad_type();
 748         let lp = bcx.landing_pad(llretty, llpersonality, 1, self.llfn);
 749         bcx.set_cleanup(lp);
 750
 751         let slot = self.get_personality_slot(&bcx);
 752         slot.storage_live(&bcx);
 753         Pair(bcx.extract_value(lp, 0), bcx.extract_value(lp, 1)).store(&bcx, slot);
 754
 755         bcx.br(target_bb);
 756         bcx.llbb()
 757     }
 758
 759     fn landing_pad_type(&self) -> Type {
 760         let ccx = self.ccx;
 761         Type::struct_(ccx, &[Type::i8p(ccx), Type::i32(ccx)], false)
 762     }
 763
 764     fn unreachable_block(&mut self) -> BasicBlockRef {
 765         self.unreachable_block.unwrap_or_else(|| {
 766             let bl = self.new_block("unreachable");
 767             bl.unreachable();
 768             self.unreachable_block = Some(bl.llbb());
 769             bl.llbb()
 770         })
 771     }
 772
 773     pub fn new_block(&self, name: &str) -> Builder<'a, 'tcx> {
 774         Builder::new_block(self.ccx, self.llfn, name)
 775     }
 776
 777     pub fn get_builder(&self, bb: mir::BasicBlock) -> Builder<'a, 'tcx> {
 778         let builder = Builder::with_ccx(self.ccx);
 779         builder.position_at_end(self.blocks[bb]);
 780         builder
 781     }
 782
 783     fn make_return_dest(&mut self, bcx: &Builder<'a, 'tcx>,
 784                         dest: &mir::Lvalue<'tcx>, fn_ret: &ArgType<'tcx>,
 785                         llargs: &mut Vec<ValueRef>, is_intrinsic: bool)
 786                         -> ReturnDest<'tcx> {
 787         // If the return is ignored, we can just return a do-nothing ReturnDest
 788         if fn_ret.is_ignore() {
 789             return ReturnDest::Nothing;
 790         }
 791         let dest = if let mir::Lvalue::Local(index) = *dest {
 792             match self.locals[index] {
 793                 LocalRef::Lvalue(dest) => dest,
 794                 LocalRef::Operand(None) => {
 795                     // Handle temporary lvalues, specifically Operand ones, as
 796                     // they don't have allocas
 797                     return if fn_ret.is_indirect() {
 798                         // Odd, but possible, case, we have an operand temporary,
 799                         // but the calling convention has an indirect return.
 800                         let tmp = LvalueRef::alloca(bcx, fn_ret.layout, "tmp_ret");
 801                         tmp.storage_live(bcx);
 802                         llargs.push(tmp.llval);
 803                         ReturnDest::IndirectOperand(tmp, index)
 804                     } else if is_intrinsic {
 805                         // Currently, intrinsics always need a location to store
 806                         // the result. so we create a temporary alloca for the
 807                         // result
 808                         let tmp = LvalueRef::alloca(bcx, fn_ret.layout, "tmp_ret");
 809                         tmp.storage_live(bcx);
 810                         ReturnDest::IndirectOperand(tmp, index)
 811                     } else {
 812                         ReturnDest::DirectOperand(index)
 813                     };
 814                 }
 815                 LocalRef::Operand(Some(_)) => {
 816                     bug!("lvalue local already assigned to");
 817                 }
 818             }
 819         } else {
 820             self.trans_lvalue(bcx, dest)
 821         };
 822         if fn_ret.is_indirect() {
 823             match dest.alignment {
 824                 Alignment::AbiAligned => {
 825                     llargs.push(dest.llval);
 826                     ReturnDest::Nothing
 827                 },
 828                 Alignment::Packed(_) => {
 829                     // Currently, MIR code generation does not create calls
 830                     // that store directly to fields of packed structs (in
 831                     // fact, the calls it creates write only to temps),
 832                     //
 833                     // If someone changes that, please update this code path
 834                     // to create a temporary.
 835                     span_bug!(self.mir.span, "can't directly store to unaligned value");
 836                 }
 837             }
 838         } else {
 839             ReturnDest::Store(dest)
 840         }
 841     }
 842
 843     fn trans_transmute(&mut self, bcx: &Builder<'a, 'tcx>,
 844                        src: &mir::Operand<'tcx>,
 845                        dst: &mir::Lvalue<'tcx>) {
 846         if let mir::Lvalue::Local(index) = *dst {
 847             match self.locals[index] {
 848                 LocalRef::Lvalue(lvalue) => self.trans_transmute_into(bcx, src, lvalue),
 849                 LocalRef::Operand(None) => {
 850                     let dst_layout = bcx.ccx.layout_of(self.monomorphized_lvalue_ty(dst));
 851                     assert!(!dst_layout.ty.has_erasable_regions());
 852                     let lvalue = LvalueRef::alloca(bcx, dst_layout, "transmute_temp");
 853                     lvalue.storage_live(bcx);
 854                     self.trans_transmute_into(bcx, src, lvalue);
 855                     let op = lvalue.load(bcx);
 856                     lvalue.storage_dead(bcx);
 857                     self.locals[index] = LocalRef::Operand(Some(op));
 858                 }
 859                 LocalRef::Operand(Some(op)) => {
 860                     assert!(op.layout.is_zst(),
 861                             "assigning to initialized SSAtemp");
 862                 }
 863             }
 864         } else {
 865             let dst = self.trans_lvalue(bcx, dst);
 866             self.trans_transmute_into(bcx, src, dst);
 867         }
 868     }
 869
 870     fn trans_transmute_into(&mut self, bcx: &Builder<'a, 'tcx>,
 871                             src: &mir::Operand<'tcx>,
 872                             dst: LvalueRef<'tcx>) {
 873         let src = self.trans_operand(bcx, src);
 874         let llty = src.layout.llvm_type(bcx.ccx);
 875         let cast_ptr = bcx.pointercast(dst.llval, llty.ptr_to());
 876         let align = src.layout.align.min(dst.layout.align);
 877         src.val.store(bcx,
 878             LvalueRef::new_sized(cast_ptr, src.layout, Alignment::Packed(align)));
 879     }
 880
 881
 882     // Stores the return value of a function call into it's final location.
 883     fn store_return(&mut self,
 884                     bcx: &Builder<'a, 'tcx>,
 885                     dest: ReturnDest<'tcx>,
 886                     ret_ty: &ArgType<'tcx>,
 887                     llval: ValueRef) {
 888         use self::ReturnDest::*;
 889
 890         match dest {
 891             Nothing => (),
 892             Store(dst) => ret_ty.store(bcx, llval, dst),
 893             IndirectOperand(tmp, index) => {
 894                 let op = tmp.load(bcx);
 895                 tmp.storage_dead(bcx);
 896                 self.locals[index] = LocalRef::Operand(Some(op));
 897             }
 898             DirectOperand(index) => {
 899                 // If there is a cast, we have to store and reload.
 900                 let op = if let PassMode::Cast(_) = ret_ty.mode {
 901                     let tmp = LvalueRef::alloca(bcx, ret_ty.layout, "tmp_ret");
 902                     tmp.storage_live(bcx);
 903                     ret_ty.store(bcx, llval, tmp);
 904                     let op = tmp.load(bcx);
 905                     tmp.storage_dead(bcx);
 906                     op
 907                 } else {
 908                     OperandRef::from_immediate_or_packed_pair(bcx, llval, ret_ty.layout)
 909                 };
 910                 self.locals[index] = LocalRef::Operand(Some(op));
 911             }
 912         }
 913     }
 914 }
 915
 916 enum ReturnDest<'tcx> {
 917     // Do nothing, the return value is indirect or ignored
 918     Nothing,
 919     // Store the return value to the pointer
 920     Store(LvalueRef<'tcx>),
 921     // Stores an indirect return value to an operand local lvalue
 922     IndirectOperand(LvalueRef<'tcx>, mir::Local),
 923     // Stores a direct return value to an operand local lvalue
 924     DirectOperand(mir::Local)
 925 }