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