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, LayoutTyper};
  16 use rustc::mir;
  17 use abi::{Abi, FnType, ArgType};
  18 use adt;
  19 use base::{self, Lifetime};
  20 use callee;
  21 use builder::Builder;
  22 use common::{self, Funclet};
  23 use common::{C_bool, C_str_slice, C_struct, C_u32, C_uint, C_undef};
  24 use consts;
  25 use machine::llalign_of_min;
  26 use meth;
  27 use monomorphize;
  28 use type_of;
  29 use tvec;
  30 use type_::Type;
  31
  32 use rustc_data_structures::indexed_vec::IndexVec;
  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::{Alignment, 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, None);
 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::SwitchInt { ref discr, switch_ty, ref values, ref targets } => {
 140                 let discr = self.trans_operand(&bcx, discr);
 141                 if switch_ty == bcx.tcx().types.bool {
 142                     let lltrue = llblock(self, targets[0]);
 143                     let llfalse = llblock(self, targets[1]);
 144                     if let [ConstInt::U8(0)] = values[..] {
 145                         bcx.cond_br(discr.immediate(), llfalse, lltrue);
 146                     } else {
 147                         bcx.cond_br(discr.immediate(), lltrue, llfalse);
 148                     }
 149                 } else {
 150                     let (otherwise, targets) = targets.split_last().unwrap();
 151                     let switch = bcx.switch(discr.immediate(),
 152                                             llblock(self, *otherwise), values.len());
 153                     for (value, target) in values.iter().zip(targets) {
 154                         let val = Const::from_constint(bcx.ccx, value);
 155                         let llbb = llblock(self, *target);
 156                         bcx.add_case(switch, val.llval, llbb)
 157                     }
 158                 }
 159             }
 160
 161             mir::TerminatorKind::Return => {
 162                 let ret = self.fn_ty.ret;
 163                 if ret.is_ignore() || ret.is_indirect() {
 164                     bcx.ret_void();
 165                     return;
 166                 }
 167
 168                 let llval = if let Some(cast_ty) = ret.cast {
 169                     let op = match self.locals[mir::RETURN_POINTER] {
 170                         LocalRef::Operand(Some(op)) => op,
 171                         LocalRef::Operand(None) => bug!("use of return before def"),
 172                         LocalRef::Lvalue(tr_lvalue) => {
 173                             OperandRef {
 174                                 val: Ref(tr_lvalue.llval, tr_lvalue.alignment),
 175                                 ty: tr_lvalue.ty.to_ty(bcx.tcx())
 176                             }
 177                         }
 178                     };
 179                     let llslot = match op.val {
 180                         Immediate(_) | Pair(..) => {
 181                             let llscratch = bcx.alloca(ret.memory_ty(bcx.ccx), "ret", None);
 182                             self.store_operand(&bcx, llscratch, None, op);
 183                             llscratch
 184                         }
 185                         Ref(llval, align) => {
 186                             assert_eq!(align, Alignment::AbiAligned,
 187                                        "return pointer is unaligned!");
 188                             llval
 189                         }
 190                     };
 191                     let load = bcx.load(
 192                         bcx.pointercast(llslot, cast_ty.ptr_to()),
 193                         Some(ret.layout.align(bcx.ccx).abi() as u32));
 194                     load
 195                 } else {
 196                     let op = self.trans_consume(&bcx, &mir::Lvalue::Local(mir::RETURN_POINTER));
 197                     if let Ref(llval, align) = op.val {
 198                         base::load_ty(&bcx, llval, align, op.ty)
 199                     } else {
 200                         op.pack_if_pair(&bcx).immediate()
 201                     }
 202                 };
 203                 bcx.ret(llval);
 204             }
 205
 206             mir::TerminatorKind::Unreachable => {
 207                 bcx.unreachable();
 208             }
 209
 210             mir::TerminatorKind::Drop { ref location, target, unwind } => {
 211                 let ty = location.ty(&self.mir, bcx.tcx()).to_ty(bcx.tcx());
 212                 let ty = self.monomorphize(&ty);
 213                 let drop_fn = monomorphize::resolve_drop_in_place(bcx.ccx.shared(), ty);
 214
 215                 if let ty::InstanceDef::DropGlue(_, None) = drop_fn.def {
 216                     // we don't actually need to drop anything.
 217                     funclet_br(self, bcx, target);
 218                     return
 219                 }
 220
 221                 let lvalue = self.trans_lvalue(&bcx, location);
 222                 let (drop_fn, need_extra) = match ty.sty {
 223                     ty::TyDynamic(..) => (meth::DESTRUCTOR.get_fn(&bcx, lvalue.llextra),
 224                                           false),
 225                     ty::TyArray(ety, _) | ty::TySlice(ety) => {
 226                         // FIXME: handle panics
 227                         let drop_fn = monomorphize::resolve_drop_in_place(
 228                             bcx.ccx.shared(), ety);
 229                         let drop_fn = callee::get_fn(bcx.ccx, drop_fn);
 230                         let bcx = tvec::slice_for_each(
 231                             &bcx,
 232                             lvalue.project_index(&bcx, C_uint(bcx.ccx, 0u64)),
 233                             ety,
 234                             lvalue.len(bcx.ccx),
 235                             |bcx, llval, loop_bb| {
 236                                 self.set_debug_loc(&bcx, terminator.source_info);
 237                                 if let Some(unwind) = unwind {
 238                                     bcx.invoke(
 239                                         drop_fn,
 240                                         &[llval],
 241                                         loop_bb,
 242                                         llblock(self, unwind),
 243                                         cleanup_bundle
 244                                     );
 245                                 } else {
 246                                     bcx.call(drop_fn, &[llval], cleanup_bundle);
 247                                     bcx.br(loop_bb);
 248                                 }
 249                             });
 250                         funclet_br(self, bcx, target);
 251                         return
 252                     }
 253                     _ => (callee::get_fn(bcx.ccx, drop_fn), lvalue.has_extra())
 254                 };
 255                 let args = &[lvalue.llval, lvalue.llextra][..1 + need_extra as usize];
 256                 if let Some(unwind) = unwind {
 257                     bcx.invoke(
 258                         drop_fn,
 259                         args,
 260                         self.blocks[target],
 261                         llblock(self, unwind),
 262                         cleanup_bundle
 263                     );
 264                 } else {
 265                     bcx.call(drop_fn, args, cleanup_bundle);
 266                     funclet_br(self, bcx, target);
 267                 }
 268             }
 269
 270             mir::TerminatorKind::Assert { ref cond, expected, ref msg, target, cleanup } => {
 271                 let cond = self.trans_operand(&bcx, cond).immediate();
 272                 let mut const_cond = common::const_to_opt_u128(cond, false).map(|c| c == 1);
 273
 274                 // This case can currently arise only from functions marked
 275                 // with #[rustc_inherit_overflow_checks] and inlined from
 276                 // another crate (mostly core::num generic/#[inline] fns),
 277                 // while the current crate doesn't use overflow checks.
 278                 // NOTE: Unlike binops, negation doesn't have its own
 279                 // checked operation, just a comparison with the minimum
 280                 // value, so we have to check for the assert message.
 281                 if !bcx.ccx.check_overflow() {
 282                     use rustc_const_math::ConstMathErr::Overflow;
 283                     use rustc_const_math::Op::Neg;
 284
 285                     if let mir::AssertMessage::Math(Overflow(Neg)) = *msg {
 286                         const_cond = Some(expected);
 287                     }
 288                 }
 289
 290                 // Don't translate the panic block if success if known.
 291                 if const_cond == Some(expected) {
 292                     funclet_br(self, bcx, target);
 293                     return;
 294                 }
 295
 296                 // Pass the condition through llvm.expect for branch hinting.
 297                 let expect = bcx.ccx.get_intrinsic(&"llvm.expect.i1");
 298                 let cond = bcx.call(expect, &[cond, C_bool(bcx.ccx, expected)], None);
 299
 300                 // Create the failure block and the conditional branch to it.
 301                 let lltarget = llblock(self, target);
 302                 let panic_block = self.new_block("panic");
 303                 if expected {
 304                     bcx.cond_br(cond, lltarget, panic_block.llbb());
 305                 } else {
 306                     bcx.cond_br(cond, panic_block.llbb(), lltarget);
 307                 }
 308
 309                 // After this point, bcx is the block for the call to panic.
 310                 bcx = panic_block;
 311                 self.set_debug_loc(&bcx, terminator.source_info);
 312
 313                 // Get the location information.
 314                 let loc = bcx.sess().codemap().lookup_char_pos(span.lo);
 315                 let filename = Symbol::intern(&loc.file.name).as_str();
 316                 let filename = C_str_slice(bcx.ccx, filename);
 317                 let line = C_u32(bcx.ccx, loc.line as u32);
 318
 319                 // Put together the arguments to the panic entry point.
 320                 let (lang_item, args, const_err) = match *msg {
 321                     mir::AssertMessage::BoundsCheck { ref len, ref index } => {
 322                         let len = self.trans_operand(&mut bcx, len).immediate();
 323                         let index = self.trans_operand(&mut bcx, index).immediate();
 324
 325                         let const_err = common::const_to_opt_u128(len, false)
 326                             .and_then(|len| common::const_to_opt_u128(index, false)
 327                                 .map(|index| ErrKind::IndexOutOfBounds {
 328                                     len: len as u64,
 329                                     index: index as u64
 330                                 }));
 331
 332                         let file_line = C_struct(bcx.ccx, &[filename, line], false);
 333                         let align = llalign_of_min(bcx.ccx, common::val_ty(file_line));
 334                         let file_line = consts::addr_of(bcx.ccx,
 335                                                         file_line,
 336                                                         align,
 337                                                         "panic_bounds_check_loc");
 338                         (lang_items::PanicBoundsCheckFnLangItem,
 339                          vec![file_line, index, len],
 340                          const_err)
 341                     }
 342                     mir::AssertMessage::Math(ref err) => {
 343                         let msg_str = Symbol::intern(err.description()).as_str();
 344                         let msg_str = C_str_slice(bcx.ccx, msg_str);
 345                         let msg_file_line = C_struct(bcx.ccx,
 346                                                      &[msg_str, filename, line],
 347                                                      false);
 348                         let align = llalign_of_min(bcx.ccx, common::val_ty(msg_file_line));
 349                         let msg_file_line = consts::addr_of(bcx.ccx,
 350                                                             msg_file_line,
 351                                                             align,
 352                                                             "panic_loc");
 353                         (lang_items::PanicFnLangItem,
 354                          vec![msg_file_line],
 355                          Some(ErrKind::Math(err.clone())))
 356                     }
 357                 };
 358
 359                 // If we know we always panic, and the error message
 360                 // is also constant, then we can produce a warning.
 361                 if const_cond == Some(!expected) {
 362                     if let Some(err) = const_err {
 363                         let err = ConstEvalErr{ span: span, kind: err };
 364                         let mut diag = bcx.tcx().sess.struct_span_warn(
 365                             span, "this expression will panic at run-time");
 366                         err.note(bcx.tcx(), span, "expression", &mut diag);
 367                         diag.emit();
 368                     }
 369                 }
 370
 371                 // Obtain the panic entry point.
 372                 let def_id = common::langcall(bcx.tcx(), Some(span), "", lang_item);
 373                 let instance = ty::Instance::mono(bcx.tcx(), def_id);
 374                 let llfn = callee::get_fn(bcx.ccx, instance);
 375
 376                 // Translate the actual panic invoke/call.
 377                 if let Some(unwind) = cleanup {
 378                     bcx.invoke(llfn,
 379                                &args,
 380                                self.unreachable_block(),
 381                                llblock(self, unwind),
 382                                cleanup_bundle);
 383                 } else {
 384                     bcx.call(llfn, &args, cleanup_bundle);
 385                     bcx.unreachable();
 386                 }
 387             }
 388
 389             mir::TerminatorKind::DropAndReplace { .. } => {
 390                 bug!("undesugared DropAndReplace in trans: {:?}", data);
 391             }
 392
 393             mir::TerminatorKind::Call { ref func, ref args, ref destination, ref cleanup } => {
 394                 // Create the callee. This is a fn ptr or zero-sized and hence a kind of scalar.
 395                 let callee = self.trans_operand(&bcx, func);
 396
 397                 let (instance, mut llfn, sig) = match callee.ty.sty {
 398                     ty::TyFnDef(def_id, substs, sig) => {
 399                         (Some(monomorphize::resolve(bcx.ccx.shared(), def_id, substs)),
 400                          None,
 401                          sig)
 402                     }
 403                     ty::TyFnPtr(sig) => {
 404                         (None,
 405                          Some(callee.immediate()),
 406                          sig)
 407                     }
 408                     _ => bug!("{} is not callable", callee.ty)
 409                 };
 410                 let def = instance.map(|i| i.def);
 411                 let sig = bcx.tcx().erase_late_bound_regions_and_normalize(&sig);
 412                 let abi = sig.abi;
 413
 414                 // Handle intrinsics old trans wants Expr's for, ourselves.
 415                 let intrinsic = match def {
 416                     Some(ty::InstanceDef::Intrinsic(def_id))
 417                         => Some(bcx.tcx().item_name(def_id).as_str()),
 418                     _ => None
 419                 };
 420                 let intrinsic = intrinsic.as_ref().map(|s| &s[..]);
 421
 422                 if intrinsic == Some("transmute") {
 423                     let &(ref dest, target) = destination.as_ref().unwrap();
 424                     self.trans_transmute(&bcx, &args[0], dest);
 425                     funclet_br(self, bcx, target);
 426                     return;
 427                 }
 428
 429                 let extra_args = &args[sig.inputs().len()..];
 430                 let extra_args = extra_args.iter().map(|op_arg| {
 431                     let op_ty = op_arg.ty(&self.mir, bcx.tcx());
 432                     self.monomorphize(&op_ty)
 433                 }).collect::<Vec<_>>();
 434
 435                 let fn_ty = match def {
 436                     Some(ty::InstanceDef::Virtual(..)) => {
 437                         FnType::new_vtable(bcx.ccx, sig, &extra_args)
 438                     }
 439                     Some(ty::InstanceDef::DropGlue(_, None)) => {
 440                         // empty drop glue - a nop.
 441                         let &(_, target) = destination.as_ref().unwrap();
 442                         funclet_br(self, bcx, target);
 443                         return;
 444                     }
 445                     _ => FnType::new(bcx.ccx, sig, &extra_args)
 446                 };
 447
 448                 // The arguments we'll be passing. Plus one to account for outptr, if used.
 449                 let arg_count = fn_ty.args.len() + fn_ty.ret.is_indirect() as usize;
 450                 let mut llargs = Vec::with_capacity(arg_count);
 451
 452                 // Prepare the return value destination
 453                 let ret_dest = if let Some((ref dest, _)) = *destination {
 454                     let is_intrinsic = intrinsic.is_some();
 455                     self.make_return_dest(&bcx, dest, &fn_ty.ret, &mut llargs,
 456                                           is_intrinsic)
 457                 } else {
 458                     ReturnDest::Nothing
 459                 };
 460
 461                 // Split the rust-call tupled arguments off.
 462                 let (first_args, untuple) = if abi == Abi::RustCall && !args.is_empty() {
 463                     let (tup, args) = args.split_last().unwrap();
 464                     (args, Some(tup))
 465                 } else {
 466                     (&args[..], None)
 467                 };
 468
 469                 let is_shuffle = intrinsic.map_or(false, |name| {
 470                     name.starts_with("simd_shuffle")
 471                 });
 472                 let mut idx = 0;
 473                 for arg in first_args {
 474                     // The indices passed to simd_shuffle* in the
 475                     // third argument must be constant. This is
 476                     // checked by const-qualification, which also
 477                     // promotes any complex rvalues to constants.
 478                     if is_shuffle && idx == 2 {
 479                         match *arg {
 480                             mir::Operand::Consume(_) => {
 481                                 span_bug!(span, "shuffle indices must be constant");
 482                             }
 483                             mir::Operand::Constant(ref constant) => {
 484                                 let val = self.trans_constant(&bcx, constant);
 485                                 llargs.push(val.llval);
 486                                 idx += 1;
 487                                 continue;
 488                             }
 489                         }
 490                     }
 491
 492                     let op = self.trans_operand(&bcx, arg);
 493                     self.trans_argument(&bcx, op, &mut llargs, &fn_ty,
 494                                         &mut idx, &mut llfn, &def);
 495                 }
 496                 if let Some(tup) = untuple {
 497                     self.trans_arguments_untupled(&bcx, tup, &mut llargs, &fn_ty,
 498                                                   &mut idx, &mut llfn, &def)
 499                 }
 500
 501                 if intrinsic.is_some() && intrinsic != Some("drop_in_place") {
 502                     use intrinsic::trans_intrinsic_call;
 503
 504                     let (dest, llargs) = match ret_dest {
 505                         _ if fn_ty.ret.is_indirect() => {
 506                             (llargs[0], &llargs[1..])
 507                         }
 508                         ReturnDest::Nothing => {
 509                             (C_undef(fn_ty.ret.memory_ty(bcx.ccx).ptr_to()), &llargs[..])
 510                         }
 511                         ReturnDest::IndirectOperand(dst, _) |
 512                         ReturnDest::Store(dst) => (dst, &llargs[..]),
 513                         ReturnDest::DirectOperand(_) =>
 514                             bug!("Cannot use direct operand with an intrinsic call")
 515                     };
 516
 517                     let callee_ty = common::instance_ty(
 518                         bcx.ccx.shared(), instance.as_ref().unwrap());
 519                     trans_intrinsic_call(&bcx, callee_ty, &fn_ty, &llargs, dest,
 520                                          terminator.source_info.span);
 521
 522                     if let ReturnDest::IndirectOperand(dst, _) = ret_dest {
 523                         // Make a fake operand for store_return
 524                         let op = OperandRef {
 525                             val: Ref(dst, Alignment::AbiAligned),
 526                             ty: sig.output(),
 527                         };
 528                         self.store_return(&bcx, ret_dest, &fn_ty.ret, op);
 529                     }
 530
 531                     if let Some((_, target)) = *destination {
 532                         funclet_br(self, bcx, target);
 533                     } else {
 534                         bcx.unreachable();
 535                     }
 536
 537                     return;
 538                 }
 539
 540                 let fn_ptr = match (llfn, instance) {
 541                     (Some(llfn), _) => llfn,
 542                     (None, Some(instance)) => callee::get_fn(bcx.ccx, instance),
 543                     _ => span_bug!(span, "no llfn for call"),
 544                 };
 545
 546                 // Many different ways to call a function handled here
 547                 if let &Some(cleanup) = cleanup {
 548                     let ret_bcx = if let Some((_, target)) = *destination {
 549                         self.blocks[target]
 550                     } else {
 551                         self.unreachable_block()
 552                     };
 553                     let invokeret = bcx.invoke(fn_ptr,
 554                                                &llargs,
 555                                                ret_bcx,
 556                                                llblock(self, cleanup),
 557                                                cleanup_bundle);
 558                     fn_ty.apply_attrs_callsite(invokeret);
 559
 560                     if let Some((_, target)) = *destination {
 561                         let ret_bcx = self.get_builder(target);
 562                         self.set_debug_loc(&ret_bcx, terminator.source_info);
 563                         let op = OperandRef {
 564                             val: Immediate(invokeret),
 565                             ty: sig.output(),
 566                         };
 567                         self.store_return(&ret_bcx, ret_dest, &fn_ty.ret, op);
 568                     }
 569                 } else {
 570                     let llret = bcx.call(fn_ptr, &llargs, cleanup_bundle);
 571                     fn_ty.apply_attrs_callsite(llret);
 572                     if let Some((_, target)) = *destination {
 573                         let op = OperandRef {
 574                             val: Immediate(llret),
 575                             ty: sig.output(),
 576                         };
 577                         self.store_return(&bcx, ret_dest, &fn_ty.ret, op);
 578                         funclet_br(self, bcx, target);
 579                     } else {
 580                         bcx.unreachable();
 581                     }
 582                 }
 583             }
 584         }
 585     }
 586
 587     fn trans_argument(&mut self,
 588                       bcx: &Builder<'a, 'tcx>,
 589                       op: OperandRef<'tcx>,
 590                       llargs: &mut Vec<ValueRef>,
 591                       fn_ty: &FnType<'tcx>,
 592                       next_idx: &mut usize,
 593                       llfn: &mut Option<ValueRef>,
 594                       def: &Option<ty::InstanceDef<'tcx>>) {
 595         if let Pair(a, b) = op.val {
 596             // Treat the values in a fat pointer separately.
 597             if common::type_is_fat_ptr(bcx.ccx, op.ty) {
 598                 let (ptr, meta) = (a, b);
 599                 if *next_idx == 0 {
 600                     if let Some(ty::InstanceDef::Virtual(_, idx)) = *def {
 601                         let llmeth = meth::VirtualIndex::from_index(idx).get_fn(bcx, meta);
 602                         let llty = fn_ty.llvm_type(bcx.ccx).ptr_to();
 603                         *llfn = Some(bcx.pointercast(llmeth, llty));
 604                     }
 605                 }
 606
 607                 let imm_op = |x| OperandRef {
 608                     val: Immediate(x),
 609                     // We won't be checking the type again.
 610                     ty: bcx.tcx().types.err
 611                 };
 612                 self.trans_argument(bcx, imm_op(ptr), llargs, fn_ty, next_idx, llfn, def);
 613                 self.trans_argument(bcx, imm_op(meta), llargs, fn_ty, next_idx, llfn, def);
 614                 return;
 615             }
 616         }
 617
 618         let arg = &fn_ty.args[*next_idx];
 619         *next_idx += 1;
 620
 621         // Fill padding with undef value, where applicable.
 622         if let Some(ty) = arg.pad {
 623             llargs.push(C_undef(ty));
 624         }
 625
 626         if arg.is_ignore() {
 627             return;
 628         }
 629
 630         // Force by-ref if we have to load through a cast pointer.
 631         let (mut llval, align, by_ref) = match op.val {
 632             Immediate(_) | Pair(..) => {
 633                 if arg.is_indirect() || arg.cast.is_some() {
 634                     let llscratch = bcx.alloca(arg.memory_ty(bcx.ccx), "arg", None);
 635                     self.store_operand(bcx, llscratch, None, op);
 636                     (llscratch, Alignment::AbiAligned, true)
 637                 } else {
 638                     (op.pack_if_pair(bcx).immediate(), Alignment::AbiAligned, false)
 639                 }
 640             }
 641             Ref(llval, Alignment::Packed) if arg.is_indirect() => {
 642                 // `foo(packed.large_field)`. We can't pass the (unaligned) field directly. I
 643                 // think that ATM (Rust 1.16) we only pass temporaries, but we shouldn't
 644                 // have scary latent bugs around.
 645
 646                 let llscratch = bcx.alloca(arg.memory_ty(bcx.ccx), "arg", None);
 647                 base::memcpy_ty(bcx, llscratch, llval, op.ty, Some(1));
 648                 (llscratch, Alignment::AbiAligned, true)
 649             }
 650             Ref(llval, align) => (llval, align, true)
 651         };
 652
 653         if by_ref && !arg.is_indirect() {
 654             // Have to load the argument, maybe while casting it.
 655             if arg.layout.ty == bcx.tcx().types.bool {
 656                 // We store bools as i8 so we need to truncate to i1.
 657                 llval = bcx.load_range_assert(llval, 0, 2, llvm::False, None);
 658                 llval = bcx.trunc(llval, Type::i1(bcx.ccx));
 659             } else if let Some(ty) = arg.cast {
 660                 llval = bcx.load(bcx.pointercast(llval, ty.ptr_to()),
 661                                  align.min_with(arg.layout.align(bcx.ccx).abi() as u32));
 662             } else {
 663                 llval = bcx.load(llval, align.to_align());
 664             }
 665         }
 666
 667         llargs.push(llval);
 668     }
 669
 670     fn trans_arguments_untupled(&mut self,
 671                                 bcx: &Builder<'a, 'tcx>,
 672                                 operand: &mir::Operand<'tcx>,
 673                                 llargs: &mut Vec<ValueRef>,
 674                                 fn_ty: &FnType<'tcx>,
 675                                 next_idx: &mut usize,
 676                                 llfn: &mut Option<ValueRef>,
 677                                 def: &Option<ty::InstanceDef<'tcx>>) {
 678         let tuple = self.trans_operand(bcx, operand);
 679
 680         let arg_types = match tuple.ty.sty {
 681             ty::TyTuple(ref tys, _) => tys,
 682             _ => span_bug!(self.mir.span,
 683                            "bad final argument to \"rust-call\" fn {:?}", tuple.ty)
 684         };
 685
 686         // Handle both by-ref and immediate tuples.
 687         match tuple.val {
 688             Ref(llval, align) => {
 689                 for (n, &ty) in arg_types.iter().enumerate() {
 690                     let ptr = LvalueRef::new_sized_ty(llval, tuple.ty, align);
 691                     let (ptr, align) = ptr.trans_field_ptr(bcx, n);
 692                     let val = if common::type_is_fat_ptr(bcx.ccx, ty) {
 693                         let (lldata, llextra) = base::load_fat_ptr(bcx, ptr, align, ty);
 694                         Pair(lldata, llextra)
 695                     } else {
 696                         // trans_argument will load this if it needs to
 697                         Ref(ptr, align)
 698                     };
 699                     let op = OperandRef {
 700                         val: val,
 701                         ty: ty
 702                     };
 703                     self.trans_argument(bcx, op, llargs, fn_ty, next_idx, llfn, def);
 704                 }
 705
 706             }
 707             Immediate(llval) => {
 708                 let l = bcx.ccx.layout_of(tuple.ty);
 709                 let v = if let layout::Univariant { ref variant, .. } = *l {
 710                     variant
 711                 } else {
 712                     bug!("Not a tuple.");
 713                 };
 714                 for (n, &ty) in arg_types.iter().enumerate() {
 715                     let mut elem = bcx.extract_value(
 716                         llval, adt::struct_llfields_index(v, n));
 717                     // Truncate bools to i1, if needed
 718                     if ty.is_bool() && common::val_ty(elem) != Type::i1(bcx.ccx) {
 719                         elem = bcx.trunc(elem, Type::i1(bcx.ccx));
 720                     }
 721                     // If the tuple is immediate, the elements are as well
 722                     let op = OperandRef {
 723                         val: Immediate(elem),
 724                         ty: ty
 725                     };
 726                     self.trans_argument(bcx, op, llargs, fn_ty, next_idx, llfn, def);
 727                 }
 728             }
 729             Pair(a, b) => {
 730                 let elems = [a, b];
 731                 for (n, &ty) in arg_types.iter().enumerate() {
 732                     let mut elem = elems[n];
 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                     // Pair is always made up of immediates
 738                     let op = OperandRef {
 739                         val: Immediate(elem),
 740                         ty: ty
 741                     };
 742                     self.trans_argument(bcx, op, llargs, fn_ty, next_idx, llfn, def);
 743                 }
 744             }
 745         }
 746
 747     }
 748
 749     fn get_personality_slot(&mut self, bcx: &Builder<'a, 'tcx>) -> ValueRef {
 750         let ccx = bcx.ccx;
 751         if let Some(slot) = self.llpersonalityslot {
 752             slot
 753         } else {
 754             let llretty = Type::struct_(ccx, &[Type::i8p(ccx), Type::i32(ccx)], false);
 755             let slot = bcx.alloca(llretty, "personalityslot", None);
 756             self.llpersonalityslot = Some(slot);
 757             slot
 758         }
 759     }
 760
 761     /// Return the landingpad wrapper around the given basic block
 762     ///
 763     /// No-op in MSVC SEH scheme.
 764     fn landing_pad_to(&mut self, target_bb: mir::BasicBlock) -> BasicBlockRef {
 765         if let Some(block) = self.landing_pads[target_bb] {
 766             return block;
 767         }
 768
 769         let block = self.blocks[target_bb];
 770         let landing_pad = self.landing_pad_uncached(block);
 771         self.landing_pads[target_bb] = Some(landing_pad);
 772         landing_pad
 773     }
 774
 775     fn landing_pad_uncached(&mut self, target_bb: BasicBlockRef) -> BasicBlockRef {
 776         if base::wants_msvc_seh(self.ccx.sess()) {
 777             return target_bb;
 778         }
 779
 780         let bcx = self.new_block("cleanup");
 781
 782         let ccx = bcx.ccx;
 783         let llpersonality = self.ccx.eh_personality();
 784         let llretty = Type::struct_(ccx, &[Type::i8p(ccx), Type::i32(ccx)], false);
 785         let llretval = bcx.landing_pad(llretty, llpersonality, 1, self.llfn);
 786         bcx.set_cleanup(llretval);
 787         let slot = self.get_personality_slot(&bcx);
 788         Lifetime::Start.call(&bcx, slot);
 789         bcx.store(llretval, slot, None);
 790         bcx.br(target_bb);
 791         bcx.llbb()
 792     }
 793
 794     fn unreachable_block(&mut self) -> BasicBlockRef {
 795         self.unreachable_block.unwrap_or_else(|| {
 796             let bl = self.new_block("unreachable");
 797             bl.unreachable();
 798             self.unreachable_block = Some(bl.llbb());
 799             bl.llbb()
 800         })
 801     }
 802
 803     pub fn new_block(&self, name: &str) -> Builder<'a, 'tcx> {
 804         Builder::new_block(self.ccx, self.llfn, name)
 805     }
 806
 807     pub fn get_builder(&self, bb: mir::BasicBlock) -> Builder<'a, 'tcx> {
 808         let builder = Builder::with_ccx(self.ccx);
 809         builder.position_at_end(self.blocks[bb]);
 810         builder
 811     }
 812
 813     fn make_return_dest(&mut self, bcx: &Builder<'a, 'tcx>,
 814                         dest: &mir::Lvalue<'tcx>, fn_ret_ty: &ArgType,
 815                         llargs: &mut Vec<ValueRef>, is_intrinsic: bool) -> ReturnDest {
 816         // If the return is ignored, we can just return a do-nothing ReturnDest
 817         if fn_ret_ty.is_ignore() {
 818             return ReturnDest::Nothing;
 819         }
 820         let dest = if let mir::Lvalue::Local(index) = *dest {
 821             let ret_ty = self.monomorphized_lvalue_ty(dest);
 822             match self.locals[index] {
 823                 LocalRef::Lvalue(dest) => dest,
 824                 LocalRef::Operand(None) => {
 825                     // Handle temporary lvalues, specifically Operand ones, as
 826                     // they don't have allocas
 827                     return if fn_ret_ty.is_indirect() {
 828                         // Odd, but possible, case, we have an operand temporary,
 829                         // but the calling convention has an indirect return.
 830                         let tmp = LvalueRef::alloca(bcx, ret_ty, "tmp_ret");
 831                         llargs.push(tmp.llval);
 832                         ReturnDest::IndirectOperand(tmp.llval, index)
 833                     } else if is_intrinsic {
 834                         // Currently, intrinsics always need a location to store
 835                         // the result. so we create a temporary alloca for the
 836                         // result
 837                         let tmp = LvalueRef::alloca(bcx, ret_ty, "tmp_ret");
 838                         ReturnDest::IndirectOperand(tmp.llval, index)
 839                     } else {
 840                         ReturnDest::DirectOperand(index)
 841                     };
 842                 }
 843                 LocalRef::Operand(Some(_)) => {
 844                     bug!("lvalue local already assigned to");
 845                 }
 846             }
 847         } else {
 848             self.trans_lvalue(bcx, dest)
 849         };
 850         if fn_ret_ty.is_indirect() {
 851             match dest.alignment {
 852                 Alignment::AbiAligned => {
 853                     llargs.push(dest.llval);
 854                     ReturnDest::Nothing
 855                 },
 856                 Alignment::Packed => {
 857                     // Currently, MIR code generation does not create calls
 858                     // that store directly to fields of packed structs (in
 859                     // fact, the calls it creates write only to temps),
 860                     //
 861                     // If someone changes that, please update this code path
 862                     // to create a temporary.
 863                     span_bug!(self.mir.span, "can't directly store to unaligned value");
 864                 }
 865             }
 866         } else {
 867             ReturnDest::Store(dest.llval)
 868         }
 869     }
 870
 871     fn trans_transmute(&mut self, bcx: &Builder<'a, 'tcx>,
 872                        src: &mir::Operand<'tcx>,
 873                        dst: &mir::Lvalue<'tcx>) {
 874         if let mir::Lvalue::Local(index) = *dst {
 875             match self.locals[index] {
 876                 LocalRef::Lvalue(lvalue) => self.trans_transmute_into(bcx, src, &lvalue),
 877                 LocalRef::Operand(None) => {
 878                     let lvalue_ty = self.monomorphized_lvalue_ty(dst);
 879                     assert!(!lvalue_ty.has_erasable_regions());
 880                     let lvalue = LvalueRef::alloca(bcx, lvalue_ty, "transmute_temp");
 881                     self.trans_transmute_into(bcx, src, &lvalue);
 882                     let op = self.trans_load(bcx, lvalue.llval, lvalue.alignment, lvalue_ty);
 883                     self.locals[index] = LocalRef::Operand(Some(op));
 884                 }
 885                 LocalRef::Operand(Some(_)) => {
 886                     let ty = self.monomorphized_lvalue_ty(dst);
 887                     assert!(common::type_is_zero_size(bcx.ccx, ty),
 888                             "assigning to initialized SSAtemp");
 889                 }
 890             }
 891         } else {
 892             let dst = self.trans_lvalue(bcx, dst);
 893             self.trans_transmute_into(bcx, src, &dst);
 894         }
 895     }
 896
 897     fn trans_transmute_into(&mut self, bcx: &Builder<'a, 'tcx>,
 898                             src: &mir::Operand<'tcx>,
 899                             dst: &LvalueRef<'tcx>) {
 900         let val = self.trans_operand(bcx, src);
 901         let llty = type_of::type_of(bcx.ccx, val.ty);
 902         let cast_ptr = bcx.pointercast(dst.llval, llty.ptr_to());
 903         let in_type = val.ty;
 904         let out_type = dst.ty.to_ty(bcx.tcx());
 905         let llalign = cmp::min(bcx.ccx.align_of(in_type), bcx.ccx.align_of(out_type));
 906         self.store_operand(bcx, cast_ptr, Some(llalign), val);
 907     }
 908
 909
 910     // Stores the return value of a function call into it's final location.
 911     fn store_return(&mut self,
 912                     bcx: &Builder<'a, 'tcx>,
 913                     dest: ReturnDest,
 914                     ret_ty: &ArgType<'tcx>,
 915                     op: OperandRef<'tcx>) {
 916         use self::ReturnDest::*;
 917
 918         match dest {
 919             Nothing => (),
 920             Store(dst) => ret_ty.store(bcx, op.immediate(), dst),
 921             IndirectOperand(tmp, index) => {
 922                 let op = self.trans_load(bcx, tmp, Alignment::AbiAligned, op.ty);
 923                 self.locals[index] = LocalRef::Operand(Some(op));
 924             }
 925             DirectOperand(index) => {
 926                 // If there is a cast, we have to store and reload.
 927                 let op = if ret_ty.cast.is_some() {
 928                     let tmp = LvalueRef::alloca(bcx, op.ty, "tmp_ret");
 929                     ret_ty.store(bcx, op.immediate(), tmp.llval);
 930                     self.trans_load(bcx, tmp.llval, tmp.alignment, op.ty)
 931                 } else {
 932                     op.unpack_if_pair(bcx)
 933                 };
 934                 self.locals[index] = LocalRef::Operand(Some(op));
 935             }
 936         }
 937     }
 938 }
 939
 940 enum ReturnDest {
 941     // Do nothing, the return value is indirect or ignored
 942     Nothing,
 943     // Store the return value to the pointer
 944     Store(ValueRef),
 945     // Stores an indirect return value to an operand local lvalue
 946     IndirectOperand(ValueRef, mir::Local),
 947     // Stores a direct return value to an operand local lvalue
 948     DirectOperand(mir::Local)
 949 }