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, LayoutOf};
  16 use rustc::traits;
  17 use rustc::mir;
  18 use abi::{Abi, FnType, ArgType, PassMode};
  19 use base;
  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 meth;
  25 use monomorphize;
  26 use type_of::LayoutLlvmExt;
  27 use type_::Type;
  28
  29 use syntax::symbol::Symbol;
  30 use syntax_pos::Pos;
  31
  32 use super::{FunctionCx, LocalRef};
  33 use super::constant::Const;
  34 use super::place::PlaceRef;
  35 use super::operand::OperandRef;
  36 use super::operand::OperandValue::{Pair, Ref, Immediate};
  37
  38 impl<'a, 'tcx> FunctionCx<'a, 'tcx> {
  39     pub fn trans_block(&mut self, bb: mir::BasicBlock) {
  40         let mut bx = self.build_block(bb);
  41         let data = &self.mir[bb];
  42
  43         debug!("trans_block({:?}={:?})", bb, data);
  44
  45         for statement in &data.statements {
  46             bx = self.trans_statement(bx, statement);
  47         }
  48
  49         self.trans_terminator(bx, bb, data.terminator());
  50     }
  51
  52     fn trans_terminator(&mut self,
  53                         mut bx: Builder<'a, 'tcx>,
  54                         bb: mir::BasicBlock,
  55                         terminator: &mir::Terminator<'tcx>)
  56     {
  57         debug!("trans_terminator: {:?}", terminator);
  58
  59         // Create the cleanup bundle, if needed.
  60         let tcx = bx.tcx();
  61         let span = terminator.source_info.span;
  62         let funclet_bb = self.cleanup_kinds[bb].funclet_bb(bb);
  63         let funclet = funclet_bb.and_then(|funclet_bb| self.funclets[funclet_bb].as_ref());
  64
  65         let cleanup_pad = funclet.map(|lp| lp.cleanuppad());
  66         let cleanup_bundle = funclet.map(|l| l.bundle());
  67
  68         let lltarget = |this: &mut Self, target: mir::BasicBlock| {
  69             let lltarget = this.blocks[target];
  70             let target_funclet = this.cleanup_kinds[target].funclet_bb(target);
  71             match (funclet_bb, target_funclet) {
  72                 (None, None) => (lltarget, false),
  73                 (Some(f), Some(t_f))
  74                     if f == t_f || !base::wants_msvc_seh(tcx.sess)
  75                     => (lltarget, false),
  76                 (None, Some(_)) => {
  77                     // jump *into* cleanup - need a landing pad if GNU
  78                     (this.landing_pad_to(target), false)
  79                 }
  80                 (Some(_), None) => span_bug!(span, "{:?} - jump out of cleanup?", terminator),
  81                 (Some(_), Some(_)) => {
  82                     (this.landing_pad_to(target), true)
  83                 }
  84             }
  85         };
  86
  87         let llblock = |this: &mut Self, target: mir::BasicBlock| {
  88             let (lltarget, is_cleanupret) = lltarget(this, target);
  89             if is_cleanupret {
  90                 // MSVC cross-funclet jump - need a trampoline
  91
  92                 debug!("llblock: creating cleanup trampoline for {:?}", target);
  93                 let name = &format!("{:?}_cleanup_trampoline_{:?}", bb, target);
  94                 let trampoline = this.new_block(name);
  95                 trampoline.cleanup_ret(cleanup_pad.unwrap(), Some(lltarget));
  96                 trampoline.llbb()
  97             } else {
  98                 lltarget
  99             }
 100         };
 101
 102         let funclet_br = |this: &mut Self, bx: Builder, target: mir::BasicBlock| {
 103             let (lltarget, is_cleanupret) = lltarget(this, target);
 104             if is_cleanupret {
 105                 // micro-optimization: generate a `ret` rather than a jump
 106                 // to a trampoline.
 107                 bx.cleanup_ret(cleanup_pad.unwrap(), Some(lltarget));
 108             } else {
 109                 bx.br(lltarget);
 110             }
 111         };
 112
 113         let do_call = |
 114             this: &mut Self,
 115             bx: Builder<'a, 'tcx>,
 116             fn_ty: FnType<'tcx>,
 117             fn_ptr: ValueRef,
 118             llargs: &[ValueRef],
 119             destination: Option<(ReturnDest<'tcx>, mir::BasicBlock)>,
 120             cleanup: Option<mir::BasicBlock>
 121         | {
 122             if let Some(cleanup) = cleanup {
 123                 let ret_bx = if let Some((_, target)) = destination {
 124                     this.blocks[target]
 125                 } else {
 126                     this.unreachable_block()
 127                 };
 128                 let invokeret = bx.invoke(fn_ptr,
 129                                            &llargs,
 130                                            ret_bx,
 131                                            llblock(this, cleanup),
 132                                            cleanup_bundle);
 133                 fn_ty.apply_attrs_callsite(invokeret);
 134
 135                 if let Some((ret_dest, target)) = destination {
 136                     let ret_bx = this.build_block(target);
 137                     this.set_debug_loc(&ret_bx, terminator.source_info);
 138                     this.store_return(&ret_bx, ret_dest, &fn_ty.ret, invokeret);
 139                 }
 140             } else {
 141                 let llret = bx.call(fn_ptr, &llargs, cleanup_bundle);
 142                 fn_ty.apply_attrs_callsite(llret);
 143                 if this.mir[bb].is_cleanup {
 144                     // Cleanup is always the cold path. Don't inline
 145                     // drop glue. Also, when there is a deeply-nested
 146                     // struct, there are "symmetry" issues that cause
 147                     // exponential inlining - see issue #41696.
 148                     llvm::Attribute::NoInline.apply_callsite(llvm::AttributePlace::Function, llret);
 149                 }
 150
 151                 if let Some((ret_dest, target)) = destination {
 152                     this.store_return(&bx, ret_dest, &fn_ty.ret, llret);
 153                     funclet_br(this, bx, target);
 154                 } else {
 155                     bx.unreachable();
 156                 }
 157             }
 158         };
 159
 160         self.set_debug_loc(&bx, terminator.source_info);
 161         match terminator.kind {
 162             mir::TerminatorKind::Resume => {
 163                 if let Some(cleanup_pad) = cleanup_pad {
 164                     bx.cleanup_ret(cleanup_pad, None);
 165                 } else {
 166                     let slot = self.get_personality_slot(&bx);
 167                     let lp0 = slot.project_field(&bx, 0).load(&bx).immediate();
 168                     let lp1 = slot.project_field(&bx, 1).load(&bx).immediate();
 169                     slot.storage_dead(&bx);
 170
 171                     if !bx.sess().target.target.options.custom_unwind_resume {
 172                         let mut lp = C_undef(self.landing_pad_type());
 173                         lp = bx.insert_value(lp, lp0, 0);
 174                         lp = bx.insert_value(lp, lp1, 1);
 175                         bx.resume(lp);
 176                     } else {
 177                         bx.call(bx.cx.eh_unwind_resume(), &[lp0], cleanup_bundle);
 178                         bx.unreachable();
 179                     }
 180                 }
 181             }
 182
 183             mir::TerminatorKind::Abort => {
 184                 // Call core::intrinsics::abort()
 185                 let fnname = bx.cx.get_intrinsic(&("llvm.trap"));
 186                 bx.call(fnname, &[], None);
 187                 bx.unreachable();
 188             }
 189
 190             mir::TerminatorKind::Goto { target } => {
 191                 funclet_br(self, bx, target);
 192             }
 193
 194             mir::TerminatorKind::SwitchInt { ref discr, switch_ty, ref values, ref targets } => {
 195                 let discr = self.trans_operand(&bx, discr);
 196                 if switch_ty == bx.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                         bx.cond_br(discr.immediate(), llfalse, lltrue);
 201                     } else {
 202                         bx.cond_br(discr.immediate(), lltrue, llfalse);
 203                     }
 204                 } else {
 205                     let (otherwise, targets) = targets.split_last().unwrap();
 206                     let switch = bx.switch(discr.immediate(),
 207                                             llblock(self, *otherwise), values.len());
 208                     for (value, target) in values.iter().zip(targets) {
 209                         let val = Const::from_constint(bx.cx, value);
 210                         let llbb = llblock(self, *target);
 211                         bx.add_case(switch, val.llval, llbb)
 212                     }
 213                 }
 214             }
 215
 216             mir::TerminatorKind::Return => {
 217                 let llval = match self.fn_ty.ret.mode {
 218                     PassMode::Ignore | PassMode::Indirect(_) => {
 219                         bx.ret_void();
 220                         return;
 221                     }
 222
 223                     PassMode::Direct(_) | PassMode::Pair(..) => {
 224                         let op = self.trans_consume(&bx, &mir::Place::Local(mir::RETURN_PLACE));
 225                         if let Ref(llval, align) = op.val {
 226                             bx.load(llval, align)
 227                         } else {
 228                             op.immediate_or_packed_pair(&bx)
 229                         }
 230                     }
 231
 232                     PassMode::Cast(cast_ty) => {
 233                         let op = match self.locals[mir::RETURN_PLACE] {
 234                             LocalRef::Operand(Some(op)) => op,
 235                             LocalRef::Operand(None) => bug!("use of return before def"),
 236                             LocalRef::Place(tr_place) => {
 237                                 OperandRef {
 238                                     val: Ref(tr_place.llval, tr_place.align),
 239                                     layout: tr_place.layout
 240                                 }
 241                             }
 242                         };
 243                         let llslot = match op.val {
 244                             Immediate(_) | Pair(..) => {
 245                                 let scratch = PlaceRef::alloca(&bx, self.fn_ty.ret.layout, "ret");
 246                                 op.val.store(&bx, scratch);
 247                                 scratch.llval
 248                             }
 249                             Ref(llval, align) => {
 250                                 assert_eq!(align.abi(), op.layout.align.abi(),
 251                                            "return place is unaligned!");
 252                                 llval
 253                             }
 254                         };
 255                         bx.load(
 256                             bx.pointercast(llslot, cast_ty.llvm_type(bx.cx).ptr_to()),
 257                             self.fn_ty.ret.layout.align)
 258                     }
 259                 };
 260                 bx.ret(llval);
 261             }
 262
 263             mir::TerminatorKind::Unreachable => {
 264                 bx.unreachable();
 265             }
 266
 267             mir::TerminatorKind::Drop { ref location, target, unwind } => {
 268                 let ty = location.ty(self.mir, bx.tcx()).to_ty(bx.tcx());
 269                 let ty = self.monomorphize(&ty);
 270                 let drop_fn = monomorphize::resolve_drop_in_place(bx.cx.tcx, ty);
 271
 272                 if let ty::InstanceDef::DropGlue(_, None) = drop_fn.def {
 273                     // we don't actually need to drop anything.
 274                     funclet_br(self, bx, target);
 275                     return
 276                 }
 277
 278                 let place = self.trans_place(&bx, location);
 279                 let mut args: &[_] = &[place.llval, place.llextra];
 280                 args = &args[..1 + place.has_extra() as usize];
 281                 let (drop_fn, fn_ty) = match ty.sty {
 282                     ty::TyDynamic(..) => {
 283                         let fn_ty = drop_fn.ty(bx.cx.tcx);
 284                         let sig = common::ty_fn_sig(bx.cx, fn_ty);
 285                         let sig = bx.tcx().erase_late_bound_regions_and_normalize(&sig);
 286                         let fn_ty = FnType::new_vtable(bx.cx, sig, &[]);
 287                         args = &args[..1];
 288                         (meth::DESTRUCTOR.get_fn(&bx, place.llextra, &fn_ty), fn_ty)
 289                     }
 290                     _ => {
 291                         (callee::get_fn(bx.cx, drop_fn),
 292                          FnType::of_instance(bx.cx, &drop_fn))
 293                     }
 294                 };
 295                 do_call(self, bx, fn_ty, drop_fn, args,
 296                         Some((ReturnDest::Nothing, target)),
 297                         unwind);
 298             }
 299
 300             mir::TerminatorKind::Assert { ref cond, expected, ref msg, target, cleanup } => {
 301                 let cond = self.trans_operand(&bx, cond).immediate();
 302                 let mut const_cond = common::const_to_opt_u128(cond, false).map(|c| c == 1);
 303
 304                 // This case can currently arise only from functions marked
 305                 // with #[rustc_inherit_overflow_checks] and inlined from
 306                 // another crate (mostly core::num generic/#[inline] fns),
 307                 // while the current crate doesn't use overflow checks.
 308                 // NOTE: Unlike binops, negation doesn't have its own
 309                 // checked operation, just a comparison with the minimum
 310                 // value, so we have to check for the assert message.
 311                 if !bx.cx.check_overflow {
 312                     use rustc_const_math::ConstMathErr::Overflow;
 313                     use rustc_const_math::Op::Neg;
 314
 315                     if let mir::AssertMessage::Math(Overflow(Neg)) = *msg {
 316                         const_cond = Some(expected);
 317                     }
 318                 }
 319
 320                 // Don't translate the panic block if success if known.
 321                 if const_cond == Some(expected) {
 322                     funclet_br(self, bx, target);
 323                     return;
 324                 }
 325
 326                 // Pass the condition through llvm.expect for branch hinting.
 327                 let expect = bx.cx.get_intrinsic(&"llvm.expect.i1");
 328                 let cond = bx.call(expect, &[cond, C_bool(bx.cx, expected)], None);
 329
 330                 // Create the failure block and the conditional branch to it.
 331                 let lltarget = llblock(self, target);
 332                 let panic_block = self.new_block("panic");
 333                 if expected {
 334                     bx.cond_br(cond, lltarget, panic_block.llbb());
 335                 } else {
 336                     bx.cond_br(cond, panic_block.llbb(), lltarget);
 337                 }
 338
 339                 // After this point, bx is the block for the call to panic.
 340                 bx = panic_block;
 341                 self.set_debug_loc(&bx, terminator.source_info);
 342
 343                 // Get the location information.
 344                 let loc = bx.sess().codemap().lookup_char_pos(span.lo());
 345                 let filename = Symbol::intern(&loc.file.name.to_string()).as_str();
 346                 let filename = C_str_slice(bx.cx, filename);
 347                 let line = C_u32(bx.cx, loc.line as u32);
 348                 let col = C_u32(bx.cx, loc.col.to_usize() as u32 + 1);
 349                 let align = tcx.data_layout.aggregate_align
 350                     .max(tcx.data_layout.i32_align)
 351                     .max(tcx.data_layout.pointer_align);
 352
 353                 // Put together the arguments to the panic entry point.
 354                 let (lang_item, args, const_err) = match *msg {
 355                     mir::AssertMessage::BoundsCheck { ref len, ref index } => {
 356                         let len = self.trans_operand(&mut bx, len).immediate();
 357                         let index = self.trans_operand(&mut bx, index).immediate();
 358
 359                         let const_err = common::const_to_opt_u128(len, false)
 360                             .and_then(|len| common::const_to_opt_u128(index, false)
 361                                 .map(|index| ErrKind::IndexOutOfBounds {
 362                                     len: len as u64,
 363                                     index: index as u64
 364                                 }));
 365
 366                         let file_line_col = C_struct(bx.cx, &[filename, line, col], false);
 367                         let file_line_col = consts::addr_of(bx.cx,
 368                                                             file_line_col,
 369                                                             align,
 370                                                             "panic_bounds_check_loc");
 371                         (lang_items::PanicBoundsCheckFnLangItem,
 372                          vec![file_line_col, index, len],
 373                          const_err)
 374                     }
 375                     mir::AssertMessage::Math(ref err) => {
 376                         let msg_str = Symbol::intern(err.description()).as_str();
 377                         let msg_str = C_str_slice(bx.cx, msg_str);
 378                         let msg_file_line_col = C_struct(bx.cx,
 379                                                      &[msg_str, filename, line, col],
 380                                                      false);
 381                         let msg_file_line_col = consts::addr_of(bx.cx,
 382                                                                 msg_file_line_col,
 383                                                                 align,
 384                                                                 "panic_loc");
 385                         (lang_items::PanicFnLangItem,
 386                          vec![msg_file_line_col],
 387                          Some(ErrKind::Math(err.clone())))
 388                     }
 389                     mir::AssertMessage::GeneratorResumedAfterReturn |
 390                     mir::AssertMessage::GeneratorResumedAfterPanic => {
 391                         let str = if let mir::AssertMessage::GeneratorResumedAfterReturn = *msg {
 392                             "generator resumed after completion"
 393                         } else {
 394                             "generator resumed after panicking"
 395                         };
 396                         let msg_str = Symbol::intern(str).as_str();
 397                         let msg_str = C_str_slice(bx.cx, msg_str);
 398                         let msg_file_line_col = C_struct(bx.cx,
 399                                                      &[msg_str, filename, line, col],
 400                                                      false);
 401                         let msg_file_line_col = consts::addr_of(bx.cx,
 402                                                                 msg_file_line_col,
 403                                                                 align,
 404                                                                 "panic_loc");
 405                         (lang_items::PanicFnLangItem,
 406                          vec![msg_file_line_col],
 407                          None)
 408                     }
 409                 };
 410
 411                 // If we know we always panic, and the error message
 412                 // is also constant, then we can produce a warning.
 413                 if const_cond == Some(!expected) {
 414                     if let Some(err) = const_err {
 415                         let err = ConstEvalErr{ span: span, kind: err };
 416                         let mut diag = bx.tcx().sess.struct_span_warn(
 417                             span, "this expression will panic at run-time");
 418                         err.note(bx.tcx(), span, "expression", &mut diag);
 419                         diag.emit();
 420                     }
 421                 }
 422
 423                 // Obtain the panic entry point.
 424                 let def_id = common::langcall(bx.tcx(), Some(span), "", lang_item);
 425                 let instance = ty::Instance::mono(bx.tcx(), def_id);
 426                 let fn_ty = FnType::of_instance(bx.cx, &instance);
 427                 let llfn = callee::get_fn(bx.cx, instance);
 428
 429                 // Translate the actual panic invoke/call.
 430                 do_call(self, bx, fn_ty, llfn, &args, None, cleanup);
 431             }
 432
 433             mir::TerminatorKind::DropAndReplace { .. } => {
 434                 bug!("undesugared DropAndReplace in trans: {:?}", terminator);
 435             }
 436
 437             mir::TerminatorKind::Call { ref func, ref args, ref destination, cleanup } => {
 438                 // Create the callee. This is a fn ptr or zero-sized and hence a kind of scalar.
 439                 let callee = self.trans_operand(&bx, func);
 440
 441                 let (instance, mut llfn) = match callee.layout.ty.sty {
 442                     ty::TyFnDef(def_id, substs) => {
 443                         (Some(ty::Instance::resolve(bx.cx.tcx,
 444                                                     ty::ParamEnv::empty(traits::Reveal::All),
 445                                                     def_id,
 446                                                     substs).unwrap()),
 447                          None)
 448                     }
 449                     ty::TyFnPtr(_) => {
 450                         (None, Some(callee.immediate()))
 451                     }
 452                     _ => bug!("{} is not callable", callee.layout.ty)
 453                 };
 454                 let def = instance.map(|i| i.def);
 455                 let sig = callee.layout.ty.fn_sig(bx.tcx());
 456                 let sig = bx.tcx().erase_late_bound_regions_and_normalize(&sig);
 457                 let abi = sig.abi;
 458
 459                 // Handle intrinsics old trans wants Expr's for, ourselves.
 460                 let intrinsic = match def {
 461                     Some(ty::InstanceDef::Intrinsic(def_id))
 462                         => Some(bx.tcx().item_name(def_id)),
 463                     _ => None
 464                 };
 465                 let intrinsic = intrinsic.as_ref().map(|s| &s[..]);
 466
 467                 if intrinsic == Some("transmute") {
 468                     let &(ref dest, target) = destination.as_ref().unwrap();
 469                     self.trans_transmute(&bx, &args[0], dest);
 470                     funclet_br(self, bx, target);
 471                     return;
 472                 }
 473
 474                 let extra_args = &args[sig.inputs().len()..];
 475                 let extra_args = extra_args.iter().map(|op_arg| {
 476                     let op_ty = op_arg.ty(self.mir, bx.tcx());
 477                     self.monomorphize(&op_ty)
 478                 }).collect::<Vec<_>>();
 479
 480                 let fn_ty = match def {
 481                     Some(ty::InstanceDef::Virtual(..)) => {
 482                         FnType::new_vtable(bx.cx, sig, &extra_args)
 483                     }
 484                     Some(ty::InstanceDef::DropGlue(_, None)) => {
 485                         // empty drop glue - a nop.
 486                         let &(_, target) = destination.as_ref().unwrap();
 487                         funclet_br(self, bx, target);
 488                         return;
 489                     }
 490                     _ => FnType::new(bx.cx, sig, &extra_args)
 491                 };
 492
 493                 // The arguments we'll be passing. Plus one to account for outptr, if used.
 494                 let arg_count = fn_ty.args.len() + fn_ty.ret.is_indirect() as usize;
 495                 let mut llargs = Vec::with_capacity(arg_count);
 496
 497                 // Prepare the return value destination
 498                 let ret_dest = if let Some((ref dest, _)) = *destination {
 499                     let is_intrinsic = intrinsic.is_some();
 500                     self.make_return_dest(&bx, dest, &fn_ty.ret, &mut llargs,
 501                                           is_intrinsic)
 502                 } else {
 503                     ReturnDest::Nothing
 504                 };
 505
 506                 if intrinsic.is_some() && intrinsic != Some("drop_in_place") {
 507                     use intrinsic::trans_intrinsic_call;
 508
 509                     let dest = match ret_dest {
 510                         _ if fn_ty.ret.is_indirect() => llargs[0],
 511                         ReturnDest::Nothing => {
 512                             C_undef(fn_ty.ret.memory_ty(bx.cx).ptr_to())
 513                         }
 514                         ReturnDest::IndirectOperand(dst, _) |
 515                         ReturnDest::Store(dst) => dst.llval,
 516                         ReturnDest::DirectOperand(_) =>
 517                             bug!("Cannot use direct operand with an intrinsic call")
 518                     };
 519
 520                     let args: Vec<_> = args.iter().enumerate().map(|(i, arg)| {
 521                         // The indices passed to simd_shuffle* in the
 522                         // third argument must be constant. This is
 523                         // checked by const-qualification, which also
 524                         // promotes any complex rvalues to constants.
 525                         if i == 2 && intrinsic.unwrap().starts_with("simd_shuffle") {
 526                             match *arg {
 527                                 mir::Operand::Copy(_) |
 528                                 mir::Operand::Move(_) => {
 529                                     span_bug!(span, "shuffle indices must be constant");
 530                                 }
 531                                 mir::Operand::Constant(ref constant) => {
 532                                     let val = self.trans_constant(&bx, constant);
 533                                     return OperandRef {
 534                                         val: Immediate(val.llval),
 535                                         layout: bx.cx.layout_of(val.ty)
 536                                     };
 537                                 }
 538                             }
 539                         }
 540
 541                         self.trans_operand(&bx, arg)
 542                     }).collect();
 543
 544
 545                     let callee_ty = instance.as_ref().unwrap().ty(bx.cx.tcx);
 546                     trans_intrinsic_call(&bx, callee_ty, &fn_ty, &args, dest,
 547                                          terminator.source_info.span);
 548
 549                     if let ReturnDest::IndirectOperand(dst, _) = ret_dest {
 550                         self.store_return(&bx, ret_dest, &fn_ty.ret, dst.llval);
 551                     }
 552
 553                     if let Some((_, target)) = *destination {
 554                         funclet_br(self, bx, target);
 555                     } else {
 556                         bx.unreachable();
 557                     }
 558
 559                     return;
 560                 }
 561
 562                 // Split the rust-call tupled arguments off.
 563                 let (first_args, untuple) = if abi == Abi::RustCall && !args.is_empty() {
 564                     let (tup, args) = args.split_last().unwrap();
 565                     (args, Some(tup))
 566                 } else {
 567                     (&args[..], None)
 568                 };
 569
 570                 for (i, arg) in first_args.iter().enumerate() {
 571                     let mut op = self.trans_operand(&bx, arg);
 572                     if let (0, Some(ty::InstanceDef::Virtual(_, idx))) = (i, def) {
 573                         if let Pair(data_ptr, meta) = op.val {
 574                             llfn = Some(meth::VirtualIndex::from_index(idx)
 575                                 .get_fn(&bx, meta, &fn_ty));
 576                             llargs.push(data_ptr);
 577                             continue;
 578                         }
 579                     }
 580
 581                     // The callee needs to own the argument memory if we pass it
 582                     // by-ref, so make a local copy of non-immediate constants.
 583                     match (arg, op.val) {
 584                         (&mir::Operand::Copy(_), Ref(..)) |
 585                         (&mir::Operand::Constant(_), Ref(..)) => {
 586                             let tmp = PlaceRef::alloca(&bx, op.layout, "const");
 587                             op.val.store(&bx, tmp);
 588                             op.val = Ref(tmp.llval, tmp.align);
 589                         }
 590                         _ => {}
 591                     }
 592
 593                     self.trans_argument(&bx, op, &mut llargs, &fn_ty.args[i]);
 594                 }
 595                 if let Some(tup) = untuple {
 596                     self.trans_arguments_untupled(&bx, tup, &mut llargs,
 597                         &fn_ty.args[first_args.len()..])
 598                 }
 599
 600                 let fn_ptr = match (llfn, instance) {
 601                     (Some(llfn), _) => llfn,
 602                     (None, Some(instance)) => callee::get_fn(bx.cx, instance),
 603                     _ => span_bug!(span, "no llfn for call"),
 604                 };
 605
 606                 do_call(self, bx, fn_ty, fn_ptr, &llargs,
 607                         destination.as_ref().map(|&(_, target)| (ret_dest, target)),
 608                         cleanup);
 609             }
 610             mir::TerminatorKind::GeneratorDrop |
 611             mir::TerminatorKind::Yield { .. } => bug!("generator ops in trans"),
 612             mir::TerminatorKind::FalseEdges { .. } |
 613             mir::TerminatorKind::FalseUnwind { .. } => bug!("borrowck false edges in trans"),
 614         }
 615     }
 616
 617     fn trans_argument(&mut self,
 618                       bx: &Builder<'a, 'tcx>,
 619                       op: OperandRef<'tcx>,
 620                       llargs: &mut Vec<ValueRef>,
 621                       arg: &ArgType<'tcx>) {
 622         // Fill padding with undef value, where applicable.
 623         if let Some(ty) = arg.pad {
 624             llargs.push(C_undef(ty.llvm_type(bx.cx)));
 625         }
 626
 627         if arg.is_ignore() {
 628             return;
 629         }
 630
 631         if let PassMode::Pair(..) = arg.mode {
 632             match op.val {
 633                 Pair(a, b) => {
 634                     llargs.push(a);
 635                     llargs.push(b);
 636                     return;
 637                 }
 638                 _ => bug!("trans_argument: {:?} invalid for pair arugment", op)
 639             }
 640         }
 641
 642         // Force by-ref if we have to load through a cast pointer.
 643         let (mut llval, align, by_ref) = match op.val {
 644             Immediate(_) | Pair(..) => {
 645                 match arg.mode {
 646                     PassMode::Indirect(_) | PassMode::Cast(_) => {
 647                         let scratch = PlaceRef::alloca(bx, arg.layout, "arg");
 648                         op.val.store(bx, scratch);
 649                         (scratch.llval, scratch.align, true)
 650                     }
 651                     _ => {
 652                         (op.immediate_or_packed_pair(bx), arg.layout.align, false)
 653                     }
 654                 }
 655             }
 656             Ref(llval, align) => {
 657                 if arg.is_indirect() && align.abi() < arg.layout.align.abi() {
 658                     // `foo(packed.large_field)`. We can't pass the (unaligned) field directly. I
 659                     // think that ATM (Rust 1.16) we only pass temporaries, but we shouldn't
 660                     // have scary latent bugs around.
 661
 662                     let scratch = PlaceRef::alloca(bx, arg.layout, "arg");
 663                     base::memcpy_ty(bx, scratch.llval, llval, op.layout, align);
 664                     (scratch.llval, scratch.align, true)
 665                 } else {
 666                     (llval, align, true)
 667                 }
 668             }
 669         };
 670
 671         if by_ref && !arg.is_indirect() {
 672             // Have to load the argument, maybe while casting it.
 673             if let PassMode::Cast(ty) = arg.mode {
 674                 llval = bx.load(bx.pointercast(llval, ty.llvm_type(bx.cx).ptr_to()),
 675                                  align.min(arg.layout.align));
 676             } else {
 677                 // We can't use `PlaceRef::load` here because the argument
 678                 // may have a type we don't treat as immediate, but the ABI
 679                 // used for this call is passing it by-value. In that case,
 680                 // the load would just produce `OperandValue::Ref` instead
 681                 // of the `OperandValue::Immediate` we need for the call.
 682                 llval = bx.load(llval, align);
 683                 if let layout::Abi::Scalar(ref scalar) = arg.layout.abi {
 684                     if scalar.is_bool() {
 685                         bx.range_metadata(llval, 0..2);
 686                     }
 687                 }
 688                 // We store bools as i8 so we need to truncate to i1.
 689                 llval = base::to_immediate(bx, llval, arg.layout);
 690             }
 691         }
 692
 693         llargs.push(llval);
 694     }
 695
 696     fn trans_arguments_untupled(&mut self,
 697                                 bx: &Builder<'a, 'tcx>,
 698                                 operand: &mir::Operand<'tcx>,
 699                                 llargs: &mut Vec<ValueRef>,
 700                                 args: &[ArgType<'tcx>]) {
 701         let tuple = self.trans_operand(bx, operand);
 702
 703         // Handle both by-ref and immediate tuples.
 704         if let Ref(llval, align) = tuple.val {
 705             let tuple_ptr = PlaceRef::new_sized(llval, tuple.layout, align);
 706             for i in 0..tuple.layout.fields.count() {
 707                 let field_ptr = tuple_ptr.project_field(bx, i);
 708                 self.trans_argument(bx, field_ptr.load(bx), llargs, &args[i]);
 709             }
 710         } else {
 711             // If the tuple is immediate, the elements are as well.
 712             for i in 0..tuple.layout.fields.count() {
 713                 let op = tuple.extract_field(bx, i);
 714                 self.trans_argument(bx, op, llargs, &args[i]);
 715             }
 716         }
 717     }
 718
 719     fn get_personality_slot(&mut self, bx: &Builder<'a, 'tcx>) -> PlaceRef<'tcx> {
 720         let cx = bx.cx;
 721         if let Some(slot) = self.personality_slot {
 722             slot
 723         } else {
 724             let layout = cx.layout_of(cx.tcx.intern_tup(&[
 725                 cx.tcx.mk_mut_ptr(cx.tcx.types.u8),
 726                 cx.tcx.types.i32
 727             ], false));
 728             let slot = PlaceRef::alloca(bx, layout, "personalityslot");
 729             self.personality_slot = Some(slot);
 730             slot
 731         }
 732     }
 733
 734     /// Return the landingpad wrapper around the given basic block
 735     ///
 736     /// No-op in MSVC SEH scheme.
 737     fn landing_pad_to(&mut self, target_bb: mir::BasicBlock) -> BasicBlockRef {
 738         if let Some(block) = self.landing_pads[target_bb] {
 739             return block;
 740         }
 741
 742         let block = self.blocks[target_bb];
 743         let landing_pad = self.landing_pad_uncached(block);
 744         self.landing_pads[target_bb] = Some(landing_pad);
 745         landing_pad
 746     }
 747
 748     fn landing_pad_uncached(&mut self, target_bb: BasicBlockRef) -> BasicBlockRef {
 749         if base::wants_msvc_seh(self.cx.sess()) {
 750             span_bug!(self.mir.span, "landing pad was not inserted?")
 751         }
 752
 753         let bx = self.new_block("cleanup");
 754
 755         let llpersonality = self.cx.eh_personality();
 756         let llretty = self.landing_pad_type();
 757         let lp = bx.landing_pad(llretty, llpersonality, 1);
 758         bx.set_cleanup(lp);
 759
 760         let slot = self.get_personality_slot(&bx);
 761         slot.storage_live(&bx);
 762         Pair(bx.extract_value(lp, 0), bx.extract_value(lp, 1)).store(&bx, slot);
 763
 764         bx.br(target_bb);
 765         bx.llbb()
 766     }
 767
 768     fn landing_pad_type(&self) -> Type {
 769         let cx = self.cx;
 770         Type::struct_(cx, &[Type::i8p(cx), Type::i32(cx)], false)
 771     }
 772
 773     fn unreachable_block(&mut self) -> BasicBlockRef {
 774         self.unreachable_block.unwrap_or_else(|| {
 775             let bl = self.new_block("unreachable");
 776             bl.unreachable();
 777             self.unreachable_block = Some(bl.llbb());
 778             bl.llbb()
 779         })
 780     }
 781
 782     pub fn new_block(&self, name: &str) -> Builder<'a, 'tcx> {
 783         Builder::new_block(self.cx, self.llfn, name)
 784     }
 785
 786     pub fn build_block(&self, bb: mir::BasicBlock) -> Builder<'a, 'tcx> {
 787         let bx = Builder::with_cx(self.cx);
 788         bx.position_at_end(self.blocks[bb]);
 789         bx
 790     }
 791
 792     fn make_return_dest(&mut self, bx: &Builder<'a, 'tcx>,
 793                         dest: &mir::Place<'tcx>, fn_ret: &ArgType<'tcx>,
 794                         llargs: &mut Vec<ValueRef>, is_intrinsic: bool)
 795                         -> ReturnDest<'tcx> {
 796         // If the return is ignored, we can just return a do-nothing ReturnDest
 797         if fn_ret.is_ignore() {
 798             return ReturnDest::Nothing;
 799         }
 800         let dest = if let mir::Place::Local(index) = *dest {
 801             match self.locals[index] {
 802                 LocalRef::Place(dest) => dest,
 803                 LocalRef::Operand(None) => {
 804                     // Handle temporary places, specifically Operand ones, as
 805                     // they don't have allocas
 806                     return if fn_ret.is_indirect() {
 807                         // Odd, but possible, case, we have an operand temporary,
 808                         // but the calling convention has an indirect return.
 809                         let tmp = PlaceRef::alloca(bx, fn_ret.layout, "tmp_ret");
 810                         tmp.storage_live(bx);
 811                         llargs.push(tmp.llval);
 812                         ReturnDest::IndirectOperand(tmp, index)
 813                     } else if is_intrinsic {
 814                         // Currently, intrinsics always need a location to store
 815                         // the result. so we create a temporary alloca for the
 816                         // result
 817                         let tmp = PlaceRef::alloca(bx, fn_ret.layout, "tmp_ret");
 818                         tmp.storage_live(bx);
 819                         ReturnDest::IndirectOperand(tmp, index)
 820                     } else {
 821                         ReturnDest::DirectOperand(index)
 822                     };
 823                 }
 824                 LocalRef::Operand(Some(_)) => {
 825                     bug!("place local already assigned to");
 826                 }
 827             }
 828         } else {
 829             self.trans_place(bx, dest)
 830         };
 831         if fn_ret.is_indirect() {
 832             if dest.align.abi() < dest.layout.align.abi() {
 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             llargs.push(dest.llval);
 842             ReturnDest::Nothing
 843         } else {
 844             ReturnDest::Store(dest)
 845         }
 846     }
 847
 848     fn trans_transmute(&mut self, bx: &Builder<'a, 'tcx>,
 849                        src: &mir::Operand<'tcx>,
 850                        dst: &mir::Place<'tcx>) {
 851         if let mir::Place::Local(index) = *dst {
 852             match self.locals[index] {
 853                 LocalRef::Place(place) => self.trans_transmute_into(bx, src, place),
 854                 LocalRef::Operand(None) => {
 855                     let dst_layout = bx.cx.layout_of(self.monomorphized_place_ty(dst));
 856                     assert!(!dst_layout.ty.has_erasable_regions());
 857                     let place = PlaceRef::alloca(bx, dst_layout, "transmute_temp");
 858                     place.storage_live(bx);
 859                     self.trans_transmute_into(bx, src, place);
 860                     let op = place.load(bx);
 861                     place.storage_dead(bx);
 862                     self.locals[index] = LocalRef::Operand(Some(op));
 863                 }
 864                 LocalRef::Operand(Some(op)) => {
 865                     assert!(op.layout.is_zst(),
 866                             "assigning to initialized SSAtemp");
 867                 }
 868             }
 869         } else {
 870             let dst = self.trans_place(bx, dst);
 871             self.trans_transmute_into(bx, src, dst);
 872         }
 873     }
 874
 875     fn trans_transmute_into(&mut self, bx: &Builder<'a, 'tcx>,
 876                             src: &mir::Operand<'tcx>,
 877                             dst: PlaceRef<'tcx>) {
 878         let src = self.trans_operand(bx, src);
 879         let llty = src.layout.llvm_type(bx.cx);
 880         let cast_ptr = bx.pointercast(dst.llval, llty.ptr_to());
 881         let align = src.layout.align.min(dst.layout.align);
 882         src.val.store(bx, PlaceRef::new_sized(cast_ptr, src.layout, align));
 883     }
 884
 885
 886     // Stores the return value of a function call into it's final location.
 887     fn store_return(&mut self,
 888                     bx: &Builder<'a, 'tcx>,
 889                     dest: ReturnDest<'tcx>,
 890                     ret_ty: &ArgType<'tcx>,
 891                     llval: ValueRef) {
 892         use self::ReturnDest::*;
 893
 894         match dest {
 895             Nothing => (),
 896             Store(dst) => ret_ty.store(bx, llval, dst),
 897             IndirectOperand(tmp, index) => {
 898                 let op = tmp.load(bx);
 899                 tmp.storage_dead(bx);
 900                 self.locals[index] = LocalRef::Operand(Some(op));
 901             }
 902             DirectOperand(index) => {
 903                 // If there is a cast, we have to store and reload.
 904                 let op = if let PassMode::Cast(_) = ret_ty.mode {
 905                     let tmp = PlaceRef::alloca(bx, ret_ty.layout, "tmp_ret");
 906                     tmp.storage_live(bx);
 907                     ret_ty.store(bx, llval, tmp);
 908                     let op = tmp.load(bx);
 909                     tmp.storage_dead(bx);
 910                     op
 911                 } else {
 912                     OperandRef::from_immediate_or_packed_pair(bx, llval, ret_ty.layout)
 913                 };
 914                 self.locals[index] = LocalRef::Operand(Some(op));
 915             }
 916         }
 917     }
 918 }
 919
 920 enum ReturnDest<'tcx> {
 921     // Do nothing, the return value is indirect or ignored
 922     Nothing,
 923     // Store the return value to the pointer
 924     Store(PlaceRef<'tcx>),
 925     // Stores an indirect return value to an operand local place
 926     IndirectOperand(PlaceRef<'tcx>, mir::Local),
 927     // Stores a direct return value to an operand local place
 928     DirectOperand(mir::Local)
 929 }