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