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_const_eval::{ErrKind, ConstEvalErr, note_const_eval_err};
  13 use rustc::middle::lang_items;
  14 use rustc::ty::{self, layout};
  15 use rustc::mir;
  16 use abi::{Abi, FnType, ArgType};
  17 use adt;
  18 use base::{self, Lifetime};
  19 use callee::{Callee, CalleeData, Fn, Intrinsic, NamedTupleConstructor, Virtual};
  20 use builder::Builder;
  21 use common::{self, Funclet};
  22 use common::{C_bool, C_str_slice, C_struct, C_u32, C_undef};
  23 use consts;
  24 use Disr;
  25 use machine::{llalign_of_min, llbitsize_of_real};
  26 use meth;
  27 use type_of::{self, align_of};
  28 use glue;
  29 use type_::Type;
  30
  31 use rustc_data_structures::indexed_vec::IndexVec;
  32 use rustc_data_structures::fx::FxHashMap;
  33 use syntax::symbol::Symbol;
  34
  35 use std::cmp;
  36
  37 use super::{MirContext, LocalRef};
  38 use super::analyze::CleanupKind;
  39 use super::constant::Const;
  40 use super::lvalue::LvalueRef;
  41 use super::operand::OperandRef;
  42 use super::operand::OperandValue::{Pair, Ref, Immediate};
  43
  44 impl<'a, 'tcx> MirContext<'a, 'tcx> {
  45     pub fn trans_block(&mut self, bb: mir::BasicBlock,
  46         funclets: &IndexVec<mir::BasicBlock, Option<Funclet>>) {
  47         let mut bcx = self.get_builder(bb);
  48         let data = &self.mir[bb];
  49
  50         debug!("trans_block({:?}={:?})", bb, data);
  51
  52         let funclet = match self.cleanup_kinds[bb] {
  53             CleanupKind::Internal { funclet } => funclets[funclet].as_ref(),
  54             _ => funclets[bb].as_ref(),
  55         };
  56
  57         // Create the cleanup bundle, if needed.
  58         let cleanup_pad = funclet.map(|lp| lp.cleanuppad());
  59         let cleanup_bundle = funclet.map(|l| l.bundle());
  60
  61         let funclet_br = |this: &Self, bcx: Builder, bb: mir::BasicBlock| {
  62             let lltarget = this.blocks[bb];
  63             if let Some(cp) = cleanup_pad {
  64                 match this.cleanup_kinds[bb] {
  65                     CleanupKind::Funclet => {
  66                         // micro-optimization: generate a `ret` rather than a jump
  67                         // to a return block
  68                         bcx.cleanup_ret(cp, Some(lltarget));
  69                     }
  70                     CleanupKind::Internal { .. } => bcx.br(lltarget),
  71                     CleanupKind::NotCleanup => bug!("jump from cleanup bb to bb {:?}", bb)
  72                 }
  73             } else {
  74                 bcx.br(lltarget);
  75             }
  76         };
  77
  78         let llblock = |this: &mut Self, target: mir::BasicBlock| {
  79             let lltarget = this.blocks[target];
  80
  81             if let Some(cp) = cleanup_pad {
  82                 match this.cleanup_kinds[target] {
  83                     CleanupKind::Funclet => {
  84                         // MSVC cross-funclet jump - need a trampoline
  85
  86                         debug!("llblock: creating cleanup trampoline for {:?}", target);
  87                         let name = &format!("{:?}_cleanup_trampoline_{:?}", bb, target);
  88                         let trampoline = this.new_block(name);
  89                         trampoline.cleanup_ret(cp, Some(lltarget));
  90                         trampoline.llbb()
  91                     }
  92                     CleanupKind::Internal { .. } => lltarget,
  93                     CleanupKind::NotCleanup =>
  94                         bug!("jump from cleanup bb {:?} to bb {:?}", bb, target)
  95                 }
  96             } else {
  97                 if let (CleanupKind::NotCleanup, CleanupKind::Funclet) =
  98                     (this.cleanup_kinds[bb], this.cleanup_kinds[target])
  99                 {
 100                     // jump *into* cleanup - need a landing pad if GNU
 101                     this.landing_pad_to(target)
 102                 } else {
 103                     lltarget
 104                 }
 105             }
 106         };
 107
 108         for statement in &data.statements {
 109             bcx = self.trans_statement(bcx, statement);
 110         }
 111
 112         let terminator = data.terminator();
 113         debug!("trans_block: terminator: {:?}", terminator);
 114
 115         let span = terminator.source_info.span;
 116         self.set_debug_loc(&bcx, terminator.source_info);
 117         match terminator.kind {
 118             mir::TerminatorKind::Resume => {
 119                 if let Some(cleanup_pad) = cleanup_pad {
 120                     bcx.cleanup_ret(cleanup_pad, None);
 121                 } else {
 122                     let ps = self.get_personality_slot(&bcx);
 123                     let lp = bcx.load(ps);
 124                     Lifetime::End.call(&bcx, ps);
 125                     if !bcx.sess().target.target.options.custom_unwind_resume {
 126                         bcx.resume(lp);
 127                     } else {
 128                         let exc_ptr = bcx.extract_value(lp, 0);
 129                         bcx.call(bcx.ccx.eh_unwind_resume(), &[exc_ptr], cleanup_bundle);
 130                         bcx.unreachable();
 131                     }
 132                 }
 133             }
 134
 135             mir::TerminatorKind::Goto { target } => {
 136                 funclet_br(self, bcx, target);
 137             }
 138
 139             mir::TerminatorKind::If { ref cond, targets: (true_bb, false_bb) } => {
 140                 let cond = self.trans_operand(&bcx, cond);
 141
 142                 let lltrue = llblock(self, true_bb);
 143                 let llfalse = llblock(self, false_bb);
 144                 bcx.cond_br(cond.immediate(), lltrue, llfalse);
 145             }
 146
 147             mir::TerminatorKind::Switch { ref discr, ref adt_def, ref targets } => {
 148                 let discr_lvalue = self.trans_lvalue(&bcx, discr);
 149                 let ty = discr_lvalue.ty.to_ty(bcx.tcx());
 150                 let discr = adt::trans_get_discr(&bcx, ty, discr_lvalue.llval, None, true);
 151
 152                 let mut bb_hist = FxHashMap();
 153                 for target in targets {
 154                     *bb_hist.entry(target).or_insert(0) += 1;
 155                 }
 156                 let (default_bb, default_blk) = match bb_hist.iter().max_by_key(|&(_, c)| c) {
 157                     // If a single target basic blocks is predominant, promote that to be the
 158                     // default case for the switch instruction to reduce the size of the generated
 159                     // code. This is especially helpful in cases like an if-let on a huge enum.
 160                     // Note: This optimization is only valid for exhaustive matches.
 161                     Some((&&bb, &c)) if c > targets.len() / 2 => {
 162                         (Some(bb), llblock(self, bb))
 163                     }
 164                     // We're generating an exhaustive switch, so the else branch
 165                     // can't be hit.  Branching to an unreachable instruction
 166                     // lets LLVM know this
 167                     _ => (None, self.unreachable_block())
 168                 };
 169                 let switch = bcx.switch(discr, default_blk, targets.len());
 170                 assert_eq!(adt_def.variants.len(), targets.len());
 171                 for (adt_variant, &target) in adt_def.variants.iter().zip(targets) {
 172                     if default_bb != Some(target) {
 173                         let llbb = llblock(self, target);
 174                         let llval = adt::trans_case(&bcx, ty, Disr::from(adt_variant.disr_val));
 175                         bcx.add_case(switch, llval, llbb)
 176                     }
 177                 }
 178             }
 179
 180             mir::TerminatorKind::SwitchInt { ref discr, switch_ty, ref values, ref targets } => {
 181                 let (otherwise, targets) = targets.split_last().unwrap();
 182                 let discr = bcx.load(self.trans_lvalue(&bcx, discr).llval);
 183                 let discr = base::to_immediate(&bcx, discr, switch_ty);
 184                 let switch = bcx.switch(discr, llblock(self, *otherwise), values.len());
 185                 for (value, target) in values.iter().zip(targets) {
 186                     let val = Const::from_constval(bcx.ccx, value.clone(), switch_ty);
 187                     let llbb = llblock(self, *target);
 188                     bcx.add_case(switch, val.llval, llbb)
 189                 }
 190             }
 191
 192             mir::TerminatorKind::Return => {
 193                 let ret = self.fn_ty.ret;
 194                 if ret.is_ignore() || ret.is_indirect() {
 195                     bcx.ret_void();
 196                     return;
 197                 }
 198
 199                 let llval = if let Some(cast_ty) = ret.cast {
 200                     let op = match self.locals[mir::RETURN_POINTER] {
 201                         LocalRef::Operand(Some(op)) => op,
 202                         LocalRef::Operand(None) => bug!("use of return before def"),
 203                         LocalRef::Lvalue(tr_lvalue) => {
 204                             OperandRef {
 205                                 val: Ref(tr_lvalue.llval),
 206                                 ty: tr_lvalue.ty.to_ty(bcx.tcx())
 207                             }
 208                         }
 209                     };
 210                     let llslot = match op.val {
 211                         Immediate(_) | Pair(..) => {
 212                             let llscratch = bcx.alloca(ret.original_ty, "ret");
 213                             self.store_operand(&bcx, llscratch, op, None);
 214                             llscratch
 215                         }
 216                         Ref(llval) => llval
 217                     };
 218                     let load = bcx.load(bcx.pointercast(llslot, cast_ty.ptr_to()));
 219                     let llalign = llalign_of_min(bcx.ccx, ret.ty);
 220                     unsafe {
 221                         llvm::LLVMSetAlignment(load, llalign);
 222                     }
 223                     load
 224                 } else {
 225                     let op = self.trans_consume(&bcx, &mir::Lvalue::Local(mir::RETURN_POINTER));
 226                     if let Ref(llval) = op.val {
 227                         base::load_ty(&bcx, llval, op.ty)
 228                     } else {
 229                         op.pack_if_pair(&bcx).immediate()
 230                     }
 231                 };
 232                 bcx.ret(llval);
 233             }
 234
 235             mir::TerminatorKind::Unreachable => {
 236                 bcx.unreachable();
 237             }
 238
 239             mir::TerminatorKind::Drop { ref location, target, unwind } => {
 240                 let ty = location.ty(&self.mir, bcx.tcx()).to_ty(bcx.tcx());
 241                 let ty = self.monomorphize(&ty);
 242
 243                 // Double check for necessity to drop
 244                 if !bcx.ccx.shared().type_needs_drop(ty) {
 245                     funclet_br(self, bcx, target);
 246                     return;
 247                 }
 248
 249                 let mut lvalue = self.trans_lvalue(&bcx, location);
 250                 let drop_fn = glue::get_drop_glue(bcx.ccx, ty);
 251                 let drop_ty = glue::get_drop_glue_type(bcx.ccx.shared(), ty);
 252                 if bcx.ccx.shared().type_is_sized(ty) && drop_ty != ty {
 253                     lvalue.llval = bcx.pointercast(
 254                         lvalue.llval, type_of::type_of(bcx.ccx, drop_ty).ptr_to());
 255                 }
 256                 let args = &[lvalue.llval, lvalue.llextra][..1 + lvalue.has_extra() as usize];
 257                 if let Some(unwind) = unwind {
 258                     bcx.invoke(
 259                         drop_fn,
 260                         args,
 261                         self.blocks[target],
 262                         llblock(self, unwind),
 263                         cleanup_bundle
 264                     );
 265                 } else {
 266                     bcx.call(drop_fn, args, cleanup_bundle);
 267                     funclet_br(self, bcx, target);
 268                 }
 269             }
 270
 271             mir::TerminatorKind::Assert { ref cond, expected, ref msg, target, cleanup } => {
 272                 let cond = self.trans_operand(&bcx, cond).immediate();
 273                 let mut const_cond = common::const_to_opt_u128(cond, false).map(|c| c == 1);
 274
 275                 // This case can currently arise only from functions marked
 276                 // with #[rustc_inherit_overflow_checks] and inlined from
 277                 // another crate (mostly core::num generic/#[inline] fns),
 278                 // while the current crate doesn't use overflow checks.
 279                 // NOTE: Unlike binops, negation doesn't have its own
 280                 // checked operation, just a comparison with the minimum
 281                 // value, so we have to check for the assert message.
 282                 if !bcx.ccx.check_overflow() {
 283                     use rustc_const_math::ConstMathErr::Overflow;
 284                     use rustc_const_math::Op::Neg;
 285
 286                     if let mir::AssertMessage::Math(Overflow(Neg)) = *msg {
 287                         const_cond = Some(expected);
 288                     }
 289                 }
 290
 291                 // Don't translate the panic block if success if known.
 292                 if const_cond == Some(expected) {
 293                     funclet_br(self, bcx, target);
 294                     return;
 295                 }
 296
 297                 // Pass the condition through llvm.expect for branch hinting.
 298                 let expect = bcx.ccx.get_intrinsic(&"llvm.expect.i1");
 299                 let cond = bcx.call(expect, &[cond, C_bool(bcx.ccx, expected)], None);
 300
 301                 // Create the failure block and the conditional branch to it.
 302                 let lltarget = llblock(self, target);
 303                 let panic_block = self.new_block("panic");
 304                 if expected {
 305                     bcx.cond_br(cond, lltarget, panic_block.llbb());
 306                 } else {
 307                     bcx.cond_br(cond, panic_block.llbb(), lltarget);
 308                 }
 309
 310                 // After this point, bcx is the block for the call to panic.
 311                 bcx = panic_block;
 312                 self.set_debug_loc(&bcx, terminator.source_info);
 313
 314                 // Get the location information.
 315                 let loc = bcx.sess().codemap().lookup_char_pos(span.lo);
 316                 let filename = Symbol::intern(&loc.file.name).as_str();
 317                 let filename = C_str_slice(bcx.ccx, filename);
 318                 let line = C_u32(bcx.ccx, loc.line as u32);
 319
 320                 // Put together the arguments to the panic entry point.
 321                 let (lang_item, args, const_err) = match *msg {
 322                     mir::AssertMessage::BoundsCheck { ref len, ref index } => {
 323                         let len = self.trans_operand(&mut bcx, len).immediate();
 324                         let index = self.trans_operand(&mut bcx, index).immediate();
 325
 326                         let const_err = common::const_to_opt_u128(len, false)
 327                             .and_then(|len| common::const_to_opt_u128(index, false)
 328                                 .map(|index| ErrKind::IndexOutOfBounds {
 329                                     len: len as u64,
 330                                     index: index as u64
 331                                 }));
 332
 333                         let file_line = C_struct(bcx.ccx, &[filename, line], false);
 334                         let align = llalign_of_min(bcx.ccx, common::val_ty(file_line));
 335                         let file_line = consts::addr_of(bcx.ccx,
 336                                                         file_line,
 337                                                         align,
 338                                                         "panic_bounds_check_loc");
 339                         (lang_items::PanicBoundsCheckFnLangItem,
 340                          vec![file_line, index, len],
 341                          const_err)
 342                     }
 343                     mir::AssertMessage::Math(ref err) => {
 344                         let msg_str = Symbol::intern(err.description()).as_str();
 345                         let msg_str = C_str_slice(bcx.ccx, msg_str);
 346                         let msg_file_line = C_struct(bcx.ccx,
 347                                                      &[msg_str, filename, line],
 348                                                      false);
 349                         let align = llalign_of_min(bcx.ccx, common::val_ty(msg_file_line));
 350                         let msg_file_line = consts::addr_of(bcx.ccx,
 351                                                             msg_file_line,
 352                                                             align,
 353                                                             "panic_loc");
 354                         (lang_items::PanicFnLangItem,
 355                          vec![msg_file_line],
 356                          Some(ErrKind::Math(err.clone())))
 357                     }
 358                 };
 359
 360                 // If we know we always panic, and the error message
 361                 // is also constant, then we can produce a warning.
 362                 if const_cond == Some(!expected) {
 363                     if let Some(err) = const_err {
 364                         let err = ConstEvalErr{ span: span, kind: err };
 365                         let mut diag = bcx.tcx().sess.struct_span_warn(
 366                             span, "this expression will panic at run-time");
 367                         note_const_eval_err(bcx.tcx(), &err, span, "expression", &mut diag);
 368                         diag.emit();
 369                     }
 370                 }
 371
 372                 // Obtain the panic entry point.
 373                 let def_id = common::langcall(bcx.tcx(), Some(span), "", lang_item);
 374                 let callee = Callee::def(bcx.ccx, def_id,
 375                     bcx.ccx.empty_substs_for_def_id(def_id));
 376                 let llfn = callee.reify(bcx.ccx);
 377
 378                 // Translate the actual panic invoke/call.
 379                 if let Some(unwind) = cleanup {
 380                     bcx.invoke(llfn,
 381                                &args,
 382                                self.unreachable_block(),
 383                                llblock(self, unwind),
 384                                cleanup_bundle);
 385                 } else {
 386                     bcx.call(llfn, &args, cleanup_bundle);
 387                     bcx.unreachable();
 388                 }
 389             }
 390
 391             mir::TerminatorKind::DropAndReplace { .. } => {
 392                 bug!("undesugared DropAndReplace in trans: {:?}", data);
 393             }
 394
 395             mir::TerminatorKind::Call { ref func, ref args, ref destination, ref cleanup } => {
 396                 // Create the callee. This is a fn ptr or zero-sized and hence a kind of scalar.
 397                 let callee = self.trans_operand(&bcx, func);
 398
 399                 let (mut callee, abi, sig) = match callee.ty.sty {
 400                     ty::TyFnDef(def_id, substs, f) => {
 401                         (Callee::def(bcx.ccx, def_id, substs), f.abi, &f.sig)
 402                     }
 403                     ty::TyFnPtr(f) => {
 404                         (Callee {
 405                             data: Fn(callee.immediate()),
 406                             ty: callee.ty
 407                         }, f.abi, &f.sig)
 408                     }
 409                     _ => bug!("{} is not callable", callee.ty)
 410                 };
 411
 412                 let sig = bcx.tcx().erase_late_bound_regions_and_normalize(sig);
 413
 414                 // Handle intrinsics old trans wants Expr's for, ourselves.
 415                 let intrinsic = match (&callee.ty.sty, &callee.data) {
 416                     (&ty::TyFnDef(def_id, ..), &Intrinsic) => {
 417                         Some(bcx.tcx().item_name(def_id).as_str())
 418                     }
 419                     _ => None
 420                 };
 421                 let mut intrinsic = intrinsic.as_ref().map(|s| &s[..]);
 422
 423                 if intrinsic == Some("move_val_init") {
 424                     let &(_, target) = destination.as_ref().unwrap();
 425                     // The first argument is a thin destination pointer.
 426                     let llptr = self.trans_operand(&bcx, &args[0]).immediate();
 427                     let val = self.trans_operand(&bcx, &args[1]);
 428                     self.store_operand(&bcx, llptr, val, None);
 429                     funclet_br(self, bcx, target);
 430                     return;
 431                 }
 432
 433                 if intrinsic == Some("transmute") {
 434                     let &(ref dest, target) = destination.as_ref().unwrap();
 435                     self.with_lvalue_ref(&bcx, dest, |this, dest| {
 436                         this.trans_transmute(&bcx, &args[0], dest);
 437                     });
 438
 439                     funclet_br(self, bcx, target);
 440                     return;
 441                 }
 442
 443                 let extra_args = &args[sig.inputs().len()..];
 444                 let extra_args = extra_args.iter().map(|op_arg| {
 445                     let op_ty = op_arg.ty(&self.mir, bcx.tcx());
 446                     self.monomorphize(&op_ty)
 447                 }).collect::<Vec<_>>();
 448                 let fn_ty = callee.direct_fn_type(bcx.ccx, &extra_args);
 449
 450                 if intrinsic == Some("drop_in_place") {
 451                     let &(_, target) = destination.as_ref().unwrap();
 452                     let ty = if let ty::TyFnDef(_, substs, _) = callee.ty.sty {
 453                         substs.type_at(0)
 454                     } else {
 455                         bug!("Unexpected ty: {}", callee.ty);
 456                     };
 457
 458                     // Double check for necessity to drop
 459                     if !bcx.ccx.shared().type_needs_drop(ty) {
 460                         funclet_br(self, bcx, target);
 461                         return;
 462                     }
 463
 464                     let drop_fn = glue::get_drop_glue(bcx.ccx, ty);
 465                     let llty = fn_ty.llvm_type(bcx.ccx).ptr_to();
 466                     callee.data = Fn(bcx.pointercast(drop_fn, llty));
 467                     intrinsic = None;
 468                 }
 469
 470                 // The arguments we'll be passing. Plus one to account for outptr, if used.
 471                 let arg_count = fn_ty.args.len() + fn_ty.ret.is_indirect() as usize;
 472                 let mut llargs = Vec::with_capacity(arg_count);
 473
 474                 // Prepare the return value destination
 475                 let ret_dest = if let Some((ref dest, _)) = *destination {
 476                     let is_intrinsic = if let Intrinsic = callee.data {
 477                         true
 478                     } else {
 479                         false
 480                     };
 481                     self.make_return_dest(&bcx, dest, &fn_ty.ret, &mut llargs, is_intrinsic)
 482                 } else {
 483                     ReturnDest::Nothing
 484                 };
 485
 486                 // Split the rust-call tupled arguments off.
 487                 let (first_args, untuple) = if abi == Abi::RustCall && !args.is_empty() {
 488                     let (tup, args) = args.split_last().unwrap();
 489                     (args, Some(tup))
 490                 } else {
 491                     (&args[..], None)
 492                 };
 493
 494                 let is_shuffle = intrinsic.map_or(false, |name| {
 495                     name.starts_with("simd_shuffle")
 496                 });
 497                 let mut idx = 0;
 498                 for arg in first_args {
 499                     // The indices passed to simd_shuffle* in the
 500                     // third argument must be constant. This is
 501                     // checked by const-qualification, which also
 502                     // promotes any complex rvalues to constants.
 503                     if is_shuffle && idx == 2 {
 504                         match *arg {
 505                             mir::Operand::Consume(_) => {
 506                                 span_bug!(span, "shuffle indices must be constant");
 507                             }
 508                             mir::Operand::Constant(ref constant) => {
 509                                 let val = self.trans_constant(&bcx, constant);
 510                                 llargs.push(val.llval);
 511                                 idx += 1;
 512                                 continue;
 513                             }
 514                         }
 515                     }
 516
 517                     let op = self.trans_operand(&bcx, arg);
 518                     self.trans_argument(&bcx, op, &mut llargs, &fn_ty,
 519                                         &mut idx, &mut callee.data);
 520                 }
 521                 if let Some(tup) = untuple {
 522                     self.trans_arguments_untupled(&bcx, tup, &mut llargs, &fn_ty,
 523                                                   &mut idx, &mut callee.data)
 524                 }
 525
 526                 let fn_ptr = match callee.data {
 527                     NamedTupleConstructor(_) => {
 528                         // FIXME translate this like mir::Rvalue::Aggregate.
 529                         callee.reify(bcx.ccx)
 530                     }
 531                     Intrinsic => {
 532                         use intrinsic::trans_intrinsic_call;
 533
 534                         let (dest, llargs) = match ret_dest {
 535                             _ if fn_ty.ret.is_indirect() => {
 536                                 (llargs[0], &llargs[1..])
 537                             }
 538                             ReturnDest::Nothing => {
 539                                 (C_undef(fn_ty.ret.original_ty.ptr_to()), &llargs[..])
 540                             }
 541                             ReturnDest::IndirectOperand(dst, _) |
 542                             ReturnDest::Store(dst) => (dst, &llargs[..]),
 543                             ReturnDest::DirectOperand(_) =>
 544                                 bug!("Cannot use direct operand with an intrinsic call")
 545                         };
 546
 547                         trans_intrinsic_call(&bcx, callee.ty, &fn_ty, &llargs, dest,
 548                             terminator.source_info.span);
 549
 550                         if let ReturnDest::IndirectOperand(dst, _) = ret_dest {
 551                             // Make a fake operand for store_return
 552                             let op = OperandRef {
 553                                 val: Ref(dst),
 554                                 ty: sig.output(),
 555                             };
 556                             self.store_return(&bcx, ret_dest, fn_ty.ret, op);
 557                         }
 558
 559                         if let Some((_, target)) = *destination {
 560                             funclet_br(self, bcx, target);
 561                         } else {
 562                             bcx.unreachable();
 563                         }
 564
 565                         return;
 566                     }
 567                     Fn(f) => f,
 568                     Virtual(_) => bug!("Virtual fn ptr not extracted")
 569                 };
 570
 571                 // Many different ways to call a function handled here
 572                 if let &Some(cleanup) = cleanup {
 573                     let ret_bcx = if let Some((_, target)) = *destination {
 574                         self.blocks[target]
 575                     } else {
 576                         self.unreachable_block()
 577                     };
 578                     let invokeret = bcx.invoke(fn_ptr,
 579                                                &llargs,
 580                                                ret_bcx,
 581                                                llblock(self, cleanup),
 582                                                cleanup_bundle);
 583                     fn_ty.apply_attrs_callsite(invokeret);
 584
 585                     if let Some((_, target)) = *destination {
 586                         let ret_bcx = self.get_builder(target);
 587                         self.set_debug_loc(&ret_bcx, terminator.source_info);
 588                         let op = OperandRef {
 589                             val: Immediate(invokeret),
 590                             ty: sig.output(),
 591                         };
 592                         self.store_return(&ret_bcx, ret_dest, fn_ty.ret, op);
 593                     }
 594                 } else {
 595                     let llret = bcx.call(fn_ptr, &llargs, cleanup_bundle);
 596                     fn_ty.apply_attrs_callsite(llret);
 597                     if let Some((_, target)) = *destination {
 598                         let op = OperandRef {
 599                             val: Immediate(llret),
 600                             ty: sig.output(),
 601                         };
 602                         self.store_return(&bcx, ret_dest, fn_ty.ret, op);
 603                         funclet_br(self, bcx, target);
 604                     } else {
 605                         bcx.unreachable();
 606                     }
 607                 }
 608             }
 609         }
 610     }
 611
 612     fn trans_argument(&mut self,
 613                       bcx: &Builder<'a, 'tcx>,
 614                       op: OperandRef<'tcx>,
 615                       llargs: &mut Vec<ValueRef>,
 616                       fn_ty: &FnType,
 617                       next_idx: &mut usize,
 618                       callee: &mut CalleeData) {
 619         if let Pair(a, b) = op.val {
 620             // Treat the values in a fat pointer separately.
 621             if common::type_is_fat_ptr(bcx.ccx, op.ty) {
 622                 let (ptr, meta) = (a, b);
 623                 if *next_idx == 0 {
 624                     if let Virtual(idx) = *callee {
 625                         let llfn = meth::get_virtual_method(bcx, meta, idx);
 626                         let llty = fn_ty.llvm_type(bcx.ccx).ptr_to();
 627                         *callee = Fn(bcx.pointercast(llfn, llty));
 628                     }
 629                 }
 630
 631                 let imm_op = |x| OperandRef {
 632                     val: Immediate(x),
 633                     // We won't be checking the type again.
 634                     ty: bcx.tcx().types.err
 635                 };
 636                 self.trans_argument(bcx, imm_op(ptr), llargs, fn_ty, next_idx, callee);
 637                 self.trans_argument(bcx, imm_op(meta), llargs, fn_ty, next_idx, callee);
 638                 return;
 639             }
 640         }
 641
 642         let arg = &fn_ty.args[*next_idx];
 643         *next_idx += 1;
 644
 645         // Fill padding with undef value, where applicable.
 646         if let Some(ty) = arg.pad {
 647             llargs.push(C_undef(ty));
 648         }
 649
 650         if arg.is_ignore() {
 651             return;
 652         }
 653
 654         // Force by-ref if we have to load through a cast pointer.
 655         let (mut llval, by_ref) = match op.val {
 656             Immediate(_) | Pair(..) => {
 657                 if arg.is_indirect() || arg.cast.is_some() {
 658                     let llscratch = bcx.alloca(arg.original_ty, "arg");
 659                     self.store_operand(bcx, llscratch, op, None);
 660                     (llscratch, true)
 661                 } else {
 662                     (op.pack_if_pair(bcx).immediate(), false)
 663                 }
 664             }
 665             Ref(llval) => (llval, true)
 666         };
 667
 668         if by_ref && !arg.is_indirect() {
 669             // Have to load the argument, maybe while casting it.
 670             if arg.original_ty == Type::i1(bcx.ccx) {
 671                 // We store bools as i8 so we need to truncate to i1.
 672                 llval = bcx.load_range_assert(llval, 0, 2, llvm::False);
 673                 llval = bcx.trunc(llval, arg.original_ty);
 674             } else if let Some(ty) = arg.cast {
 675                 llval = bcx.load(bcx.pointercast(llval, ty.ptr_to()));
 676                 let llalign = llalign_of_min(bcx.ccx, arg.ty);
 677                 unsafe {
 678                     llvm::LLVMSetAlignment(llval, llalign);
 679                 }
 680             } else {
 681                 llval = bcx.load(llval);
 682             }
 683         }
 684
 685         llargs.push(llval);
 686     }
 687
 688     fn trans_arguments_untupled(&mut self,
 689                                 bcx: &Builder<'a, 'tcx>,
 690                                 operand: &mir::Operand<'tcx>,
 691                                 llargs: &mut Vec<ValueRef>,
 692                                 fn_ty: &FnType,
 693                                 next_idx: &mut usize,
 694                                 callee: &mut CalleeData) {
 695         let tuple = self.trans_operand(bcx, operand);
 696
 697         let arg_types = match tuple.ty.sty {
 698             ty::TyTuple(ref tys, _) => tys,
 699             _ => span_bug!(self.mir.span,
 700                            "bad final argument to \"rust-call\" fn {:?}", tuple.ty)
 701         };
 702
 703         // Handle both by-ref and immediate tuples.
 704         match tuple.val {
 705             Ref(llval) => {
 706                 for (n, &ty) in arg_types.iter().enumerate() {
 707                     let ptr = LvalueRef::new_sized_ty(llval, tuple.ty);
 708                     let ptr = ptr.trans_field_ptr(bcx, n);
 709                     let val = if common::type_is_fat_ptr(bcx.ccx, ty) {
 710                         let (lldata, llextra) = base::load_fat_ptr(bcx, ptr, ty);
 711                         Pair(lldata, llextra)
 712                     } else {
 713                         // trans_argument will load this if it needs to
 714                         Ref(ptr)
 715                     };
 716                     let op = OperandRef {
 717                         val: val,
 718                         ty: ty
 719                     };
 720                     self.trans_argument(bcx, op, llargs, fn_ty, next_idx, callee);
 721                 }
 722
 723             }
 724             Immediate(llval) => {
 725                 let l = bcx.ccx.layout_of(tuple.ty);
 726                 let v = if let layout::Univariant { ref variant, .. } = *l {
 727                     variant
 728                 } else {
 729                     bug!("Not a tuple.");
 730                 };
 731                 for (n, &ty) in arg_types.iter().enumerate() {
 732                     let mut elem = bcx.extract_value(llval, v.memory_index[n] as usize);
 733                     // Truncate bools to i1, if needed
 734                     if ty.is_bool() && common::val_ty(elem) != Type::i1(bcx.ccx) {
 735                         elem = bcx.trunc(elem, Type::i1(bcx.ccx));
 736                     }
 737                     // If the tuple is immediate, the elements are as well
 738                     let op = OperandRef {
 739                         val: Immediate(elem),
 740                         ty: ty
 741                     };
 742                     self.trans_argument(bcx, op, llargs, fn_ty, next_idx, callee);
 743                 }
 744             }
 745             Pair(a, b) => {
 746                 let elems = [a, b];
 747                 for (n, &ty) in arg_types.iter().enumerate() {
 748                     let mut elem = elems[n];
 749                     // Truncate bools to i1, if needed
 750                     if ty.is_bool() && common::val_ty(elem) != Type::i1(bcx.ccx) {
 751                         elem = bcx.trunc(elem, Type::i1(bcx.ccx));
 752                     }
 753                     // Pair is always made up of immediates
 754                     let op = OperandRef {
 755                         val: Immediate(elem),
 756                         ty: ty
 757                     };
 758                     self.trans_argument(bcx, op, llargs, fn_ty, next_idx, callee);
 759                 }
 760             }
 761         }
 762
 763     }
 764
 765     fn get_personality_slot(&mut self, bcx: &Builder<'a, 'tcx>) -> ValueRef {
 766         let ccx = bcx.ccx;
 767         if let Some(slot) = self.llpersonalityslot {
 768             slot
 769         } else {
 770             let llretty = Type::struct_(ccx, &[Type::i8p(ccx), Type::i32(ccx)], false);
 771             let slot = bcx.alloca(llretty, "personalityslot");
 772             self.llpersonalityslot = Some(slot);
 773             Lifetime::Start.call(bcx, slot);
 774             slot
 775         }
 776     }
 777
 778     /// Return the landingpad wrapper around the given basic block
 779     ///
 780     /// No-op in MSVC SEH scheme.
 781     fn landing_pad_to(&mut self, target_bb: mir::BasicBlock) -> BasicBlockRef {
 782         if let Some(block) = self.landing_pads[target_bb] {
 783             return block;
 784         }
 785
 786         if base::wants_msvc_seh(self.ccx.sess()) {
 787             return self.blocks[target_bb];
 788         }
 789
 790         let target = self.get_builder(target_bb);
 791
 792         let bcx = self.new_block("cleanup");
 793         self.landing_pads[target_bb] = Some(bcx.llbb());
 794
 795         let ccx = bcx.ccx;
 796         let llpersonality = self.ccx.eh_personality();
 797         let llretty = Type::struct_(ccx, &[Type::i8p(ccx), Type::i32(ccx)], false);
 798         let llretval = bcx.landing_pad(llretty, llpersonality, 1, self.llfn);
 799         bcx.set_cleanup(llretval);
 800         let slot = self.get_personality_slot(&bcx);
 801         bcx.store(llretval, slot, None);
 802         bcx.br(target.llbb());
 803         bcx.llbb()
 804     }
 805
 806     fn unreachable_block(&mut self) -> BasicBlockRef {
 807         self.unreachable_block.unwrap_or_else(|| {
 808             let bl = self.new_block("unreachable");
 809             bl.unreachable();
 810             self.unreachable_block = Some(bl.llbb());
 811             bl.llbb()
 812         })
 813     }
 814
 815     pub fn new_block(&self, name: &str) -> Builder<'a, 'tcx> {
 816         Builder::new_block(self.ccx, self.llfn, name)
 817     }
 818
 819     pub fn get_builder(&self, bb: mir::BasicBlock) -> Builder<'a, 'tcx> {
 820         let builder = Builder::with_ccx(self.ccx);
 821         builder.position_at_end(self.blocks[bb]);
 822         builder
 823     }
 824
 825     fn make_return_dest(&mut self, bcx: &Builder<'a, 'tcx>,
 826                         dest: &mir::Lvalue<'tcx>, fn_ret_ty: &ArgType,
 827                         llargs: &mut Vec<ValueRef>, is_intrinsic: bool) -> ReturnDest {
 828         // If the return is ignored, we can just return a do-nothing ReturnDest
 829         if fn_ret_ty.is_ignore() {
 830             return ReturnDest::Nothing;
 831         }
 832         let dest = if let mir::Lvalue::Local(index) = *dest {
 833             let ret_ty = self.monomorphized_lvalue_ty(dest);
 834             match self.locals[index] {
 835                 LocalRef::Lvalue(dest) => dest,
 836                 LocalRef::Operand(None) => {
 837                     // Handle temporary lvalues, specifically Operand ones, as
 838                     // they don't have allocas
 839                     return if fn_ret_ty.is_indirect() {
 840                         // Odd, but possible, case, we have an operand temporary,
 841                         // but the calling convention has an indirect return.
 842                         let tmp = bcx.alloca_ty(ret_ty, "tmp_ret");
 843                         llargs.push(tmp);
 844                         ReturnDest::IndirectOperand(tmp, index)
 845                     } else if is_intrinsic {
 846                         // Currently, intrinsics always need a location to store
 847                         // the result. so we create a temporary alloca for the
 848                         // result
 849                         let tmp = bcx.alloca_ty(ret_ty, "tmp_ret");
 850                         ReturnDest::IndirectOperand(tmp, index)
 851                     } else {
 852                         ReturnDest::DirectOperand(index)
 853                     };
 854                 }
 855                 LocalRef::Operand(Some(_)) => {
 856                     bug!("lvalue local already assigned to");
 857                 }
 858             }
 859         } else {
 860             self.trans_lvalue(bcx, dest)
 861         };
 862         if fn_ret_ty.is_indirect() {
 863             llargs.push(dest.llval);
 864             ReturnDest::Nothing
 865         } else {
 866             ReturnDest::Store(dest.llval)
 867         }
 868     }
 869
 870     fn trans_transmute(&mut self, bcx: &Builder<'a, 'tcx>,
 871                        src: &mir::Operand<'tcx>, dst: LvalueRef<'tcx>) {
 872         let mut val = self.trans_operand(bcx, src);
 873         if let ty::TyFnDef(def_id, substs, _) = val.ty.sty {
 874             let llouttype = type_of::type_of(bcx.ccx, dst.ty.to_ty(bcx.tcx()));
 875             let out_type_size = llbitsize_of_real(bcx.ccx, llouttype);
 876             if out_type_size != 0 {
 877                 // FIXME #19925 Remove this hack after a release cycle.
 878                 let f = Callee::def(bcx.ccx, def_id, substs);
 879                 let ty = match f.ty.sty {
 880                     ty::TyFnDef(.., f) => bcx.tcx().mk_fn_ptr(f),
 881                     _ => f.ty
 882                 };
 883                 val = OperandRef {
 884                     val: Immediate(f.reify(bcx.ccx)),
 885                     ty: ty
 886                 };
 887             }
 888         }
 889
 890         let llty = type_of::type_of(bcx.ccx, val.ty);
 891         let cast_ptr = bcx.pointercast(dst.llval, llty.ptr_to());
 892         let in_type = val.ty;
 893         let out_type = dst.ty.to_ty(bcx.tcx());;
 894         let llalign = cmp::min(align_of(bcx.ccx, in_type), align_of(bcx.ccx, out_type));
 895         self.store_operand(bcx, cast_ptr, val, Some(llalign));
 896     }
 897
 898
 899     // Stores the return value of a function call into it's final location.
 900     fn store_return(&mut self,
 901                     bcx: &Builder<'a, 'tcx>,
 902                     dest: ReturnDest,
 903                     ret_ty: ArgType,
 904                     op: OperandRef<'tcx>) {
 905         use self::ReturnDest::*;
 906
 907         match dest {
 908             Nothing => (),
 909             Store(dst) => ret_ty.store(bcx, op.immediate(), dst),
 910             IndirectOperand(tmp, index) => {
 911                 let op = self.trans_load(bcx, tmp, op.ty);
 912                 self.locals[index] = LocalRef::Operand(Some(op));
 913             }
 914             DirectOperand(index) => {
 915                 // If there is a cast, we have to store and reload.
 916                 let op = if ret_ty.cast.is_some() {
 917                     let tmp = bcx.alloca_ty(op.ty, "tmp_ret");
 918                     ret_ty.store(bcx, op.immediate(), tmp);
 919                     self.trans_load(bcx, tmp, op.ty)
 920                 } else {
 921                     op.unpack_if_pair(bcx)
 922                 };
 923                 self.locals[index] = LocalRef::Operand(Some(op));
 924             }
 925         }
 926     }
 927 }
 928
 929 enum ReturnDest {
 930     // Do nothing, the return value is indirect or ignored
 931     Nothing,
 932     // Store the return value to the pointer
 933     Store(ValueRef),
 934     // Stores an indirect return value to an operand local lvalue
 935     IndirectOperand(ValueRef, mir::Local),
 936     // Stores a direct return value to an operand local lvalue
 937     DirectOperand(mir::Local)
 938 }