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