src/librustc_codegen_llvm/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, BasicBlock};
  12 use rustc::middle::lang_items;
  13 use rustc::ty::{self, Ty, TypeFoldable};
  14 use rustc::ty::layout::{self, LayoutOf};
  15 use rustc::mir;
  16 use rustc::mir::interpret::EvalErrorKind;
  17 use abi::{Abi, ArgType, ArgTypeExt, FnType, FnTypeExt, LlvmType, PassMode};
  18 use base;
  19 use callee;
  20 use builder::{Builder, MemFlags};
  21 use common::{self, C_bool, C_str_slice, C_struct, C_u32, C_uint_big, C_undef};
  22 use consts;
  23 use meth;
  24 use monomorphize;
  25 use type_of::LayoutLlvmExt;
  26 use type_::Type;
  27 use value::Value;
  28
  29 use syntax::symbol::Symbol;
  30 use syntax_pos::Pos;
  31
  32 use super::{FunctionCx, LocalRef};
  33 use super::place::PlaceRef;
  34 use super::operand::OperandRef;
  35 use super::operand::OperandValue::{Pair, Ref, Immediate};
  36
  37 impl FunctionCx<'a, 'll, 'tcx> {
  38     pub fn codegen_block(&mut self, bb: mir::BasicBlock) {
  39         let mut bx = self.build_block(bb);
  40         let data = &self.mir[bb];
  41
  42         debug!("codegen_block({:?}={:?})", bb, data);
  43
  44         for statement in &data.statements {
  45             bx = self.codegen_statement(bx, statement);
  46         }
  47
  48         self.codegen_terminator(bx, bb, data.terminator());
  49     }
  50
  51     fn codegen_terminator(&mut self,
  52                         mut bx: Builder<'a, 'll, 'tcx>,
  53                         bb: mir::BasicBlock,
  54                         terminator: &mir::Terminator<'tcx>)
  55     {
  56         debug!("codegen_terminator: {:?}", terminator);
  57
  58         // Create the cleanup bundle, if needed.
  59         let tcx = bx.tcx();
  60         let span = terminator.source_info.span;
  61         let funclet_bb = self.cleanup_kinds[bb].funclet_bb(bb);
  62         let funclet = funclet_bb.and_then(|funclet_bb| self.funclets[funclet_bb].as_ref());
  63
  64         let cleanup_pad = funclet.map(|lp| lp.cleanuppad());
  65         let cleanup_bundle = funclet.map(|l| l.bundle());
  66
  67         let lltarget = |this: &mut Self, target: mir::BasicBlock| {
  68             let lltarget = this.blocks[target];
  69             let target_funclet = this.cleanup_kinds[target].funclet_bb(target);
  70             match (funclet_bb, target_funclet) {
  71                 (None, None) => (lltarget, false),
  72                 (Some(f), Some(t_f))
  73                     if f == t_f || !base::wants_msvc_seh(tcx.sess)
  74                     => (lltarget, false),
  75                 (None, Some(_)) => {
  76                     // jump *into* cleanup - need a landing pad if GNU
  77                     (this.landing_pad_to(target), false)
  78                 }
  79                 (Some(_), None) => span_bug!(span, "{:?} - jump out of cleanup?", terminator),
  80                 (Some(_), Some(_)) => {
  81                     (this.landing_pad_to(target), true)
  82                 }
  83             }
  84         };
  85
  86         let llblock = |this: &mut Self, target: mir::BasicBlock| {
  87             let (lltarget, is_cleanupret) = lltarget(this, target);
  88             if is_cleanupret {
  89                 // MSVC cross-funclet jump - need a trampoline
  90
  91                 debug!("llblock: creating cleanup trampoline for {:?}", target);
  92                 let name = &format!("{:?}_cleanup_trampoline_{:?}", bb, target);
  93                 let trampoline = this.new_block(name);
  94                 trampoline.cleanup_ret(cleanup_pad.unwrap(), Some(lltarget));
  95                 trampoline.llbb()
  96             } else {
  97                 lltarget
  98             }
  99         };
 100
 101         let funclet_br = |this: &mut Self, bx: Builder<'_, 'll, '_>, target: mir::BasicBlock| {
 102             let (lltarget, is_cleanupret) = lltarget(this, target);
 103             if is_cleanupret {
 104                 // micro-optimization: generate a `ret` rather than a jump
 105                 // to a trampoline.
 106                 bx.cleanup_ret(cleanup_pad.unwrap(), Some(lltarget));
 107             } else {
 108                 bx.br(lltarget);
 109             }
 110         };
 111
 112         let do_call = |
 113             this: &mut Self,
 114             bx: Builder<'a, 'll, 'tcx>,
 115             fn_ty: FnType<'tcx, Ty<'tcx>>,
 116             fn_ptr: &'ll Value,
 117             llargs: &[&'ll Value],
 118             destination: Option<(ReturnDest<'ll, 'tcx>, mir::BasicBlock)>,
 119             cleanup: Option<mir::BasicBlock>
 120         | {
 121             if let Some(cleanup) = cleanup {
 122                 let ret_bx = if let Some((_, target)) = destination {
 123                     this.blocks[target]
 124                 } else {
 125                     this.unreachable_block()
 126                 };
 127                 let invokeret = bx.invoke(fn_ptr,
 128                                            &llargs,
 129                                            ret_bx,
 130                                            llblock(this, cleanup),
 131                                            cleanup_bundle);
 132                 fn_ty.apply_attrs_callsite(&bx, invokeret);
 133
 134                 if let Some((ret_dest, target)) = destination {
 135                     let ret_bx = this.build_block(target);
 136                     this.set_debug_loc(&ret_bx, terminator.source_info);
 137                     this.store_return(&ret_bx, ret_dest, &fn_ty.ret, invokeret);
 138                 }
 139             } else {
 140                 let llret = bx.call(fn_ptr, &llargs, cleanup_bundle);
 141                 fn_ty.apply_attrs_callsite(&bx, llret);
 142                 if this.mir[bb].is_cleanup {
 143                     // Cleanup is always the cold path. Don't inline
 144                     // drop glue. Also, when there is a deeply-nested
 145                     // struct, there are "symmetry" issues that cause
 146                     // exponential inlining - see issue #41696.
 147                     llvm::Attribute::NoInline.apply_callsite(llvm::AttributePlace::Function, llret);
 148                 }
 149
 150                 if let Some((ret_dest, target)) = destination {
 151                     this.store_return(&bx, ret_dest, &fn_ty.ret, llret);
 152                     funclet_br(this, bx, target);
 153                 } else {
 154                     bx.unreachable();
 155                 }
 156             }
 157         };
 158
 159         self.set_debug_loc(&bx, terminator.source_info);
 160         match terminator.kind {
 161             mir::TerminatorKind::Resume => {
 162                 if let Some(cleanup_pad) = cleanup_pad {
 163                     bx.cleanup_ret(cleanup_pad, None);
 164                 } else {
 165                     let slot = self.get_personality_slot(&bx);
 166                     let lp0 = slot.project_field(&bx, 0).load(&bx).immediate();
 167                     let lp1 = slot.project_field(&bx, 1).load(&bx).immediate();
 168                     slot.storage_dead(&bx);
 169
 170                     if !bx.sess().target.target.options.custom_unwind_resume {
 171                         let mut lp = C_undef(self.landing_pad_type());
 172                         lp = bx.insert_value(lp, lp0, 0);
 173                         lp = bx.insert_value(lp, lp1, 1);
 174                         bx.resume(lp);
 175                     } else {
 176                         bx.call(bx.cx.eh_unwind_resume(), &[lp0], cleanup_bundle);
 177                         bx.unreachable();
 178                     }
 179                 }
 180             }
 181
 182             mir::TerminatorKind::Abort => {
 183                 // Call core::intrinsics::abort()
 184                 let fnname = bx.cx.get_intrinsic(&("llvm.trap"));
 185                 bx.call(fnname, &[], None);
 186                 bx.unreachable();
 187             }
 188
 189             mir::TerminatorKind::Goto { target } => {
 190                 funclet_br(self, bx, target);
 191             }
 192
 193             mir::TerminatorKind::SwitchInt { ref discr, switch_ty, ref values, ref targets } => {
 194                 let discr = self.codegen_operand(&bx, discr);
 195                 if targets.len() == 2 {
 196                     // If there are two targets, emit br instead of switch
 197                     let lltrue = llblock(self, targets[0]);
 198                     let llfalse = llblock(self, targets[1]);
 199                     if switch_ty == bx.tcx().types.bool {
 200                         // Don't generate trivial icmps when switching on bool
 201                         if let [0] = values[..] {
 202                             bx.cond_br(discr.immediate(), llfalse, lltrue);
 203                         } else {
 204                             assert_eq!(&values[..], &[1]);
 205                             bx.cond_br(discr.immediate(), lltrue, llfalse);
 206                         }
 207                     } else {
 208                         let switch_llty = bx.cx.layout_of(switch_ty).immediate_llvm_type(bx.cx);
 209                         let llval = C_uint_big(switch_llty, values[0]);
 210                         let cmp = bx.icmp(llvm::IntEQ, discr.immediate(), llval);
 211                         bx.cond_br(cmp, lltrue, llfalse);
 212                     }
 213                 } else {
 214                     let (otherwise, targets) = targets.split_last().unwrap();
 215                     let switch = bx.switch(discr.immediate(),
 216                                             llblock(self, *otherwise), values.len());
 217                     let switch_llty = bx.cx.layout_of(switch_ty).immediate_llvm_type(bx.cx);
 218                     for (&value, target) in values.iter().zip(targets) {
 219                         let llval = C_uint_big(switch_llty, value);
 220                         let llbb = llblock(self, *target);
 221                         bx.add_case(switch, llval, llbb)
 222                     }
 223                 }
 224             }
 225
 226             mir::TerminatorKind::Return => {
 227                 let llval = match self.fn_ty.ret.mode {
 228                     PassMode::Ignore | PassMode::Indirect(..) => {
 229                         bx.ret_void();
 230                         return;
 231                     }
 232
 233                     PassMode::Direct(_) | PassMode::Pair(..) => {
 234                         let op = self.codegen_consume(&bx, &mir::Place::Local(mir::RETURN_PLACE));
 235                         if let Ref(llval, _, align) = op.val {
 236                             bx.load(llval, align)
 237                         } else {
 238                             op.immediate_or_packed_pair(&bx)
 239                         }
 240                     }
 241
 242                     PassMode::Cast(cast_ty) => {
 243                         let op = match self.locals[mir::RETURN_PLACE] {
 244                             LocalRef::Operand(Some(op)) => op,
 245                             LocalRef::Operand(None) => bug!("use of return before def"),
 246                             LocalRef::Place(cg_place) => {
 247                                 OperandRef {
 248                                     val: Ref(cg_place.llval, None, cg_place.align),
 249                                     layout: cg_place.layout
 250                                 }
 251                             }
 252                             LocalRef::UnsizedPlace(_) => bug!("return type must be sized"),
 253                         };
 254                         let llslot = match op.val {
 255                             Immediate(_) | Pair(..) => {
 256                                 let scratch = PlaceRef::alloca(&bx, self.fn_ty.ret.layout, "ret");
 257                                 op.val.store(&bx, scratch);
 258                                 scratch.llval
 259                             }
 260                             Ref(llval, _, align) => {
 261                                 assert_eq!(align.abi(), op.layout.align.abi(),
 262                                            "return place is unaligned!");
 263                                 llval
 264                             }
 265                         };
 266                         bx.load(
 267                             bx.pointercast(llslot, cast_ty.llvm_type(bx.cx).ptr_to()),
 268                             self.fn_ty.ret.layout.align)
 269                     }
 270                 };
 271                 bx.ret(llval);
 272             }
 273
 274             mir::TerminatorKind::Unreachable => {
 275                 bx.unreachable();
 276             }
 277
 278             mir::TerminatorKind::Drop { ref location, target, unwind } => {
 279                 let ty = location.ty(self.mir, bx.tcx()).to_ty(bx.tcx());
 280                 let ty = self.monomorphize(&ty);
 281                 let drop_fn = monomorphize::resolve_drop_in_place(bx.cx.tcx, ty);
 282
 283                 if let ty::InstanceDef::DropGlue(_, None) = drop_fn.def {
 284                     // we don't actually need to drop anything.
 285                     funclet_br(self, bx, target);
 286                     return
 287                 }
 288
 289                 let place = self.codegen_place(&bx, location);
 290                 let (args1, args2);
 291                 let mut args = if let Some(llextra) = place.llextra {
 292                     args2 = [place.llval, llextra];
 293                     &args2[..]
 294                 } else {
 295                     args1 = [place.llval];
 296                     &args1[..]
 297                 };
 298                 let (drop_fn, fn_ty) = match ty.sty {
 299                     ty::TyDynamic(..) => {
 300                         let fn_ty = drop_fn.ty(bx.cx.tcx);
 301                         let sig = common::ty_fn_sig(bx.cx, fn_ty);
 302                         let sig = bx.tcx().normalize_erasing_late_bound_regions(
 303                             ty::ParamEnv::reveal_all(),
 304                             &sig,
 305                         );
 306                         let fn_ty = FnType::new_vtable(bx.cx, sig, &[]);
 307                         let vtable = args[1];
 308                         args = &args[..1];
 309                         (meth::DESTRUCTOR.get_fn(&bx, vtable, &fn_ty), fn_ty)
 310                     }
 311                     _ => {
 312                         (callee::get_fn(bx.cx, drop_fn),
 313                          FnType::of_instance(bx.cx, &drop_fn))
 314                     }
 315                 };
 316                 do_call(self, bx, fn_ty, drop_fn, args,
 317                         Some((ReturnDest::Nothing, target)),
 318                         unwind);
 319             }
 320
 321             mir::TerminatorKind::Assert { ref cond, expected, ref msg, target, cleanup } => {
 322                 let cond = self.codegen_operand(&bx, cond).immediate();
 323                 let mut const_cond = common::const_to_opt_u128(cond, false).map(|c| c == 1);
 324
 325                 // This case can currently arise only from functions marked
 326                 // with #[rustc_inherit_overflow_checks] and inlined from
 327                 // another crate (mostly core::num generic/#[inline] fns),
 328                 // while the current crate doesn't use overflow checks.
 329                 // NOTE: Unlike binops, negation doesn't have its own
 330                 // checked operation, just a comparison with the minimum
 331                 // value, so we have to check for the assert message.
 332                 if !bx.cx.check_overflow {
 333                     if let mir::interpret::EvalErrorKind::OverflowNeg = *msg {
 334                         const_cond = Some(expected);
 335                     }
 336                 }
 337
 338                 // Don't codegen the panic block if success if known.
 339                 if const_cond == Some(expected) {
 340                     funclet_br(self, bx, target);
 341                     return;
 342                 }
 343
 344                 // Pass the condition through llvm.expect for branch hinting.
 345                 let expect = bx.cx.get_intrinsic(&"llvm.expect.i1");
 346                 let cond = bx.call(expect, &[cond, C_bool(bx.cx, expected)], None);
 347
 348                 // Create the failure block and the conditional branch to it.
 349                 let lltarget = llblock(self, target);
 350                 let panic_block = self.new_block("panic");
 351                 if expected {
 352                     bx.cond_br(cond, lltarget, panic_block.llbb());
 353                 } else {
 354                     bx.cond_br(cond, panic_block.llbb(), lltarget);
 355                 }
 356
 357                 // After this point, bx is the block for the call to panic.
 358                 bx = panic_block;
 359                 self.set_debug_loc(&bx, terminator.source_info);
 360
 361                 // Get the location information.
 362                 let loc = bx.sess().codemap().lookup_char_pos(span.lo());
 363                 let filename = Symbol::intern(&loc.file.name.to_string()).as_str();
 364                 let filename = C_str_slice(bx.cx, filename);
 365                 let line = C_u32(bx.cx, loc.line as u32);
 366                 let col = C_u32(bx.cx, loc.col.to_usize() as u32 + 1);
 367                 let align = tcx.data_layout.aggregate_align
 368                     .max(tcx.data_layout.i32_align)
 369                     .max(tcx.data_layout.pointer_align);
 370
 371                 // Put together the arguments to the panic entry point.
 372                 let (lang_item, args) = match *msg {
 373                     EvalErrorKind::BoundsCheck { ref len, ref index } => {
 374                         let len = self.codegen_operand(&mut bx, len).immediate();
 375                         let index = self.codegen_operand(&mut bx, index).immediate();
 376
 377                         let file_line_col = C_struct(bx.cx, &[filename, line, col], false);
 378                         let file_line_col = consts::addr_of(bx.cx,
 379                                                             file_line_col,
 380                                                             align,
 381                                                             Some("panic_bounds_check_loc"));
 382                         (lang_items::PanicBoundsCheckFnLangItem,
 383                          vec![file_line_col, index, len])
 384                     }
 385                     _ => {
 386                         let str = msg.description();
 387                         let msg_str = Symbol::intern(str).as_str();
 388                         let msg_str = C_str_slice(bx.cx, msg_str);
 389                         let msg_file_line_col = C_struct(bx.cx,
 390                                                      &[msg_str, filename, line, col],
 391                                                      false);
 392                         let msg_file_line_col = consts::addr_of(bx.cx,
 393                                                                 msg_file_line_col,
 394                                                                 align,
 395                                                                 Some("panic_loc"));
 396                         (lang_items::PanicFnLangItem,
 397                          vec![msg_file_line_col])
 398                     }
 399                 };
 400
 401                 // Obtain the panic entry point.
 402                 let def_id = common::langcall(bx.tcx(), Some(span), "", lang_item);
 403                 let instance = ty::Instance::mono(bx.tcx(), def_id);
 404                 let fn_ty = FnType::of_instance(bx.cx, &instance);
 405                 let llfn = callee::get_fn(bx.cx, instance);
 406
 407                 // Codegen the actual panic invoke/call.
 408                 do_call(self, bx, fn_ty, llfn, &args, None, cleanup);
 409             }
 410
 411             mir::TerminatorKind::DropAndReplace { .. } => {
 412                 bug!("undesugared DropAndReplace in codegen: {:?}", terminator);
 413             }
 414
 415             mir::TerminatorKind::Call { ref func, ref args, ref destination, cleanup } => {
 416                 // Create the callee. This is a fn ptr or zero-sized and hence a kind of scalar.
 417                 let callee = self.codegen_operand(&bx, func);
 418
 419                 let (instance, mut llfn) = match callee.layout.ty.sty {
 420                     ty::TyFnDef(def_id, substs) => {
 421                         (Some(ty::Instance::resolve(bx.cx.tcx,
 422                                                     ty::ParamEnv::reveal_all(),
 423                                                     def_id,
 424                                                     substs).unwrap()),
 425                          None)
 426                     }
 427                     ty::TyFnPtr(_) => {
 428                         (None, Some(callee.immediate()))
 429                     }
 430                     _ => bug!("{} is not callable", callee.layout.ty)
 431                 };
 432                 let def = instance.map(|i| i.def);
 433                 let sig = callee.layout.ty.fn_sig(bx.tcx());
 434                 let sig = bx.tcx().normalize_erasing_late_bound_regions(
 435                     ty::ParamEnv::reveal_all(),
 436                     &sig,
 437                 );
 438                 let abi = sig.abi;
 439
 440                 // Handle intrinsics old codegen wants Expr's for, ourselves.
 441                 let intrinsic = match def {
 442                     Some(ty::InstanceDef::Intrinsic(def_id))
 443                         => Some(bx.tcx().item_name(def_id).as_str()),
 444                     _ => None
 445                 };
 446                 let intrinsic = intrinsic.as_ref().map(|s| &s[..]);
 447
 448                 if intrinsic == Some("transmute") {
 449                     if let Some(destination_ref) = destination.as_ref() {
 450                         let &(ref dest, target) = destination_ref;
 451                         self.codegen_transmute(&bx, &args[0], dest);
 452                         funclet_br(self, bx, target);
 453                     } else {
 454                         // If we are trying to transmute to an uninhabited type,
 455                         // it is likely there is no allotted destination. In fact,
 456                         // transmuting to an uninhabited type is UB, which means
 457                         // we can do what we like. Here, we declare that transmuting
 458                         // into an uninhabited type is impossible, so anything following
 459                         // it must be unreachable.
 460                         assert_eq!(bx.cx.layout_of(sig.output()).abi, layout::Abi::Uninhabited);
 461                         bx.unreachable();
 462                     }
 463                     return;
 464                 }
 465
 466                 let extra_args = &args[sig.inputs().len()..];
 467                 let extra_args = extra_args.iter().map(|op_arg| {
 468                     let op_ty = op_arg.ty(self.mir, bx.tcx());
 469                     self.monomorphize(&op_ty)
 470                 }).collect::<Vec<_>>();
 471
 472                 let fn_ty = match def {
 473                     Some(ty::InstanceDef::Virtual(..)) => {
 474                         FnType::new_vtable(bx.cx, sig, &extra_args)
 475                     }
 476                     Some(ty::InstanceDef::DropGlue(_, None)) => {
 477                         // empty drop glue - a nop.
 478                         let &(_, target) = destination.as_ref().unwrap();
 479                         funclet_br(self, bx, target);
 480                         return;
 481                     }
 482                     _ => FnType::new(bx.cx, sig, &extra_args)
 483                 };
 484
 485                 // The arguments we'll be passing. Plus one to account for outptr, if used.
 486                 let arg_count = fn_ty.args.len() + fn_ty.ret.is_indirect() as usize;
 487                 let mut llargs = Vec::with_capacity(arg_count);
 488
 489                 // Prepare the return value destination
 490                 let ret_dest = if let Some((ref dest, _)) = *destination {
 491                     let is_intrinsic = intrinsic.is_some();
 492                     self.make_return_dest(&bx, dest, &fn_ty.ret, &mut llargs,
 493                                           is_intrinsic)
 494                 } else {
 495                     ReturnDest::Nothing
 496                 };
 497
 498                 if intrinsic.is_some() && intrinsic != Some("drop_in_place") {
 499                     use intrinsic::codegen_intrinsic_call;
 500
 501                     let dest = match ret_dest {
 502                         _ if fn_ty.ret.is_indirect() => llargs[0],
 503                         ReturnDest::Nothing => {
 504                             C_undef(fn_ty.ret.memory_ty(bx.cx).ptr_to())
 505                         }
 506                         ReturnDest::IndirectOperand(dst, _) |
 507                         ReturnDest::Store(dst) => dst.llval,
 508                         ReturnDest::DirectOperand(_) =>
 509                             bug!("Cannot use direct operand with an intrinsic call")
 510                     };
 511
 512                     let args: Vec<_> = args.iter().enumerate().map(|(i, arg)| {
 513                         // The indices passed to simd_shuffle* in the
 514                         // third argument must be constant. This is
 515                         // checked by const-qualification, which also
 516                         // promotes any complex rvalues to constants.
 517                         if i == 2 && intrinsic.unwrap().starts_with("simd_shuffle") {
 518                             match *arg {
 519                                 // The shuffle array argument is usually not an explicit constant,
 520                                 // but specified directly in the code. This means it gets promoted
 521                                 // and we can then extract the value by evaluating the promoted.
 522                                 mir::Operand::Copy(mir::Place::Promoted(box(index, ty))) |
 523                                 mir::Operand::Move(mir::Place::Promoted(box(index, ty))) => {
 524                                     let param_env = ty::ParamEnv::reveal_all();
 525                                     let cid = mir::interpret::GlobalId {
 526                                         instance: self.instance,
 527                                         promoted: Some(index),
 528                                     };
 529                                     let c = bx.tcx().const_eval(param_env.and(cid));
 530                                     let (llval, ty) = self.simd_shuffle_indices(
 531                                         &bx,
 532                                         terminator.source_info.span,
 533                                         ty,
 534                                         c,
 535                                     );
 536                                     return OperandRef {
 537                                         val: Immediate(llval),
 538                                         layout: bx.cx.layout_of(ty),
 539                                     };
 540
 541                                 },
 542                                 mir::Operand::Copy(_) |
 543                                 mir::Operand::Move(_) => {
 544                                     span_bug!(span, "shuffle indices must be constant");
 545                                 }
 546                                 mir::Operand::Constant(ref constant) => {
 547                                     let c = self.eval_mir_constant(&bx, constant);
 548                                     let (llval, ty) = self.simd_shuffle_indices(
 549                                         &bx,
 550                                         constant.span,
 551                                         constant.ty,
 552                                         c,
 553                                     );
 554                                     return OperandRef {
 555                                         val: Immediate(llval),
 556                                         layout: bx.cx.layout_of(ty)
 557                                     };
 558                                 }
 559                             }
 560                         }
 561
 562                         self.codegen_operand(&bx, arg)
 563                     }).collect();
 564
 565
 566                     let callee_ty = instance.as_ref().unwrap().ty(bx.cx.tcx);
 567                     codegen_intrinsic_call(&bx, callee_ty, &fn_ty, &args, dest,
 568                                          terminator.source_info.span);
 569
 570                     if let ReturnDest::IndirectOperand(dst, _) = ret_dest {
 571                         self.store_return(&bx, ret_dest, &fn_ty.ret, dst.llval);
 572                     }
 573
 574                     if let Some((_, target)) = *destination {
 575                         funclet_br(self, bx, target);
 576                     } else {
 577                         bx.unreachable();
 578                     }
 579
 580                     return;
 581                 }
 582
 583                 // Split the rust-call tupled arguments off.
 584                 let (first_args, untuple) = if abi == Abi::RustCall && !args.is_empty() {
 585                     let (tup, args) = args.split_last().unwrap();
 586                     (args, Some(tup))
 587                 } else {
 588                     (&args[..], None)
 589                 };
 590
 591                 for (i, arg) in first_args.iter().enumerate() {
 592                     let mut op = self.codegen_operand(&bx, arg);
 593                     if let (0, Some(ty::InstanceDef::Virtual(_, idx))) = (i, def) {
 594                         if let Pair(data_ptr, meta) = op.val {
 595                             llfn = Some(meth::VirtualIndex::from_index(idx)
 596                                 .get_fn(&bx, meta, &fn_ty));
 597                             llargs.push(data_ptr);
 598                             continue;
 599                         }
 600                     }
 601
 602                     // The callee needs to own the argument memory if we pass it
 603                     // by-ref, so make a local copy of non-immediate constants.
 604                     match (arg, op.val) {
 605                         (&mir::Operand::Copy(_), Ref(_, None, _)) |
 606                         (&mir::Operand::Constant(_), Ref(_, None, _)) => {
 607                             let tmp = PlaceRef::alloca(&bx, op.layout, "const");
 608                             op.val.store(&bx, tmp);
 609                             op.val = Ref(tmp.llval, None, tmp.align);
 610                         }
 611                         _ => {}
 612                     }
 613
 614                     self.codegen_argument(&bx, op, &mut llargs, &fn_ty.args[i]);
 615                 }
 616                 if let Some(tup) = untuple {
 617                     self.codegen_arguments_untupled(&bx, tup, &mut llargs,
 618                         &fn_ty.args[first_args.len()..])
 619                 }
 620
 621                 let fn_ptr = match (llfn, instance) {
 622                     (Some(llfn), _) => llfn,
 623                     (None, Some(instance)) => callee::get_fn(bx.cx, instance),
 624                     _ => span_bug!(span, "no llfn for call"),
 625                 };
 626
 627                 do_call(self, bx, fn_ty, fn_ptr, &llargs,
 628                         destination.as_ref().map(|&(_, target)| (ret_dest, target)),
 629                         cleanup);
 630             }
 631             mir::TerminatorKind::GeneratorDrop |
 632             mir::TerminatorKind::Yield { .. } => bug!("generator ops in codegen"),
 633             mir::TerminatorKind::FalseEdges { .. } |
 634             mir::TerminatorKind::FalseUnwind { .. } => bug!("borrowck false edges in codegen"),
 635         }
 636     }
 637
 638     fn codegen_argument(&mut self,
 639                       bx: &Builder<'a, 'll, 'tcx>,
 640                       op: OperandRef<'ll, 'tcx>,
 641                       llargs: &mut Vec<&'ll Value>,
 642                       arg: &ArgType<'tcx, Ty<'tcx>>) {
 643         // Fill padding with undef value, where applicable.
 644         if let Some(ty) = arg.pad {
 645             llargs.push(C_undef(ty.llvm_type(bx.cx)));
 646         }
 647
 648         if arg.is_ignore() {
 649             return;
 650         }
 651
 652         if let PassMode::Pair(..) = arg.mode {
 653             match op.val {
 654                 Pair(a, b) => {
 655                     llargs.push(a);
 656                     llargs.push(b);
 657                     return;
 658                 }
 659                 _ => bug!("codegen_argument: {:?} invalid for pair arugment", op)
 660             }
 661         } else if arg.is_unsized_indirect() {
 662             match op.val {
 663                 Ref(a, Some(b), _) => {
 664                     llargs.push(a);
 665                     llargs.push(b);
 666                     return;
 667                 }
 668                 _ => bug!("codegen_argument: {:?} invalid for unsized indirect argument", op)
 669             }
 670         }
 671
 672         // Force by-ref if we have to load through a cast pointer.
 673         let (mut llval, align, by_ref) = match op.val {
 674             Immediate(_) | Pair(..) => {
 675                 match arg.mode {
 676                     PassMode::Indirect(..) | PassMode::Cast(_) => {
 677                         let scratch = PlaceRef::alloca(bx, arg.layout, "arg");
 678                         op.val.store(bx, scratch);
 679                         (scratch.llval, scratch.align, true)
 680                     }
 681                     _ => {
 682                         (op.immediate_or_packed_pair(bx), arg.layout.align, false)
 683                     }
 684                 }
 685             }
 686             Ref(llval, _, align) => {
 687                 if arg.is_indirect() && align.abi() < arg.layout.align.abi() {
 688                     // `foo(packed.large_field)`. We can't pass the (unaligned) field directly. I
 689                     // think that ATM (Rust 1.16) we only pass temporaries, but we shouldn't
 690                     // have scary latent bugs around.
 691
 692                     let scratch = PlaceRef::alloca(bx, arg.layout, "arg");
 693                     base::memcpy_ty(bx, scratch.llval, llval, op.layout, align, MemFlags::empty());
 694                     (scratch.llval, scratch.align, true)
 695                 } else {
 696                     (llval, align, true)
 697                 }
 698             }
 699         };
 700
 701         if by_ref && !arg.is_indirect() {
 702             // Have to load the argument, maybe while casting it.
 703             if let PassMode::Cast(ty) = arg.mode {
 704                 llval = bx.load(bx.pointercast(llval, ty.llvm_type(bx.cx).ptr_to()),
 705                                  align.min(arg.layout.align));
 706             } else {
 707                 // We can't use `PlaceRef::load` here because the argument
 708                 // may have a type we don't treat as immediate, but the ABI
 709                 // used for this call is passing it by-value. In that case,
 710                 // the load would just produce `OperandValue::Ref` instead
 711                 // of the `OperandValue::Immediate` we need for the call.
 712                 llval = bx.load(llval, align);
 713                 if let layout::Abi::Scalar(ref scalar) = arg.layout.abi {
 714                     if scalar.is_bool() {
 715                         bx.range_metadata(llval, 0..2);
 716                     }
 717                 }
 718                 // We store bools as i8 so we need to truncate to i1.
 719                 llval = base::to_immediate(bx, llval, arg.layout);
 720             }
 721         }
 722
 723         llargs.push(llval);
 724     }
 725
 726     fn codegen_arguments_untupled(&mut self,
 727                                 bx: &Builder<'a, 'll, 'tcx>,
 728                                 operand: &mir::Operand<'tcx>,
 729                                 llargs: &mut Vec<&'ll Value>,
 730                                 args: &[ArgType<'tcx, Ty<'tcx>>]) {
 731         let tuple = self.codegen_operand(bx, operand);
 732
 733         // Handle both by-ref and immediate tuples.
 734         if let Ref(llval, None, align) = tuple.val {
 735             let tuple_ptr = PlaceRef::new_sized(llval, tuple.layout, align);
 736             for i in 0..tuple.layout.fields.count() {
 737                 let field_ptr = tuple_ptr.project_field(bx, i);
 738                 self.codegen_argument(bx, field_ptr.load(bx), llargs, &args[i]);
 739             }
 740         } else if let Ref(_, Some(_), _) = tuple.val {
 741             bug!("closure arguments must be sized")
 742         } else {
 743             // If the tuple is immediate, the elements are as well.
 744             for i in 0..tuple.layout.fields.count() {
 745                 let op = tuple.extract_field(bx, i);
 746                 self.codegen_argument(bx, op, llargs, &args[i]);
 747             }
 748         }
 749     }
 750
 751     fn get_personality_slot(&mut self, bx: &Builder<'a, 'll, 'tcx>) -> PlaceRef<'ll, 'tcx> {
 752         let cx = bx.cx;
 753         if let Some(slot) = self.personality_slot {
 754             slot
 755         } else {
 756             let layout = cx.layout_of(cx.tcx.intern_tup(&[
 757                 cx.tcx.mk_mut_ptr(cx.tcx.types.u8),
 758                 cx.tcx.types.i32
 759             ]));
 760             let slot = PlaceRef::alloca(bx, layout, "personalityslot");
 761             self.personality_slot = Some(slot);
 762             slot
 763         }
 764     }
 765
 766     /// Return the landingpad wrapper around the given basic block
 767     ///
 768     /// No-op in MSVC SEH scheme.
 769     fn landing_pad_to(&mut self, target_bb: mir::BasicBlock) -> &'ll BasicBlock {
 770         if let Some(block) = self.landing_pads[target_bb] {
 771             return block;
 772         }
 773
 774         let block = self.blocks[target_bb];
 775         let landing_pad = self.landing_pad_uncached(block);
 776         self.landing_pads[target_bb] = Some(landing_pad);
 777         landing_pad
 778     }
 779
 780     fn landing_pad_uncached(&mut self, target_bb: &'ll BasicBlock) -> &'ll BasicBlock {
 781         if base::wants_msvc_seh(self.cx.sess()) {
 782             span_bug!(self.mir.span, "landing pad was not inserted?")
 783         }
 784
 785         let bx = self.new_block("cleanup");
 786
 787         let llpersonality = self.cx.eh_personality();
 788         let llretty = self.landing_pad_type();
 789         let lp = bx.landing_pad(llretty, llpersonality, 1);
 790         bx.set_cleanup(lp);
 791
 792         let slot = self.get_personality_slot(&bx);
 793         slot.storage_live(&bx);
 794         Pair(bx.extract_value(lp, 0), bx.extract_value(lp, 1)).store(&bx, slot);
 795
 796         bx.br(target_bb);
 797         bx.llbb()
 798     }
 799
 800     fn landing_pad_type(&self) -> &'ll Type {
 801         let cx = self.cx;
 802         Type::struct_(cx, &[Type::i8p(cx), Type::i32(cx)], false)
 803     }
 804
 805     fn unreachable_block(&mut self) -> &'ll BasicBlock {
 806         self.unreachable_block.unwrap_or_else(|| {
 807             let bl = self.new_block("unreachable");
 808             bl.unreachable();
 809             self.unreachable_block = Some(bl.llbb());
 810             bl.llbb()
 811         })
 812     }
 813
 814     pub fn new_block(&self, name: &str) -> Builder<'a, 'll, 'tcx> {
 815         Builder::new_block(self.cx, self.llfn, name)
 816     }
 817
 818     pub fn build_block(&self, bb: mir::BasicBlock) -> Builder<'a, 'll, 'tcx> {
 819         let bx = Builder::with_cx(self.cx);
 820         bx.position_at_end(self.blocks[bb]);
 821         bx
 822     }
 823
 824     fn make_return_dest(&mut self, bx: &Builder<'a, 'll, 'tcx>,
 825                         dest: &mir::Place<'tcx>, fn_ret: &ArgType<'tcx, Ty<'tcx>>,
 826                         llargs: &mut Vec<&'ll Value>, is_intrinsic: bool)
 827                         -> ReturnDest<'ll, 'tcx> {
 828         // If the return is ignored, we can just return a do-nothing ReturnDest
 829         if fn_ret.is_ignore() {
 830             return ReturnDest::Nothing;
 831         }
 832         let dest = if let mir::Place::Local(index) = *dest {
 833             match self.locals[index] {
 834                 LocalRef::Place(dest) => dest,
 835                 LocalRef::UnsizedPlace(_) => bug!("return type must be sized"),
 836                 LocalRef::Operand(None) => {
 837                     // Handle temporary places, specifically Operand ones, as
 838                     // they don't have allocas
 839                     return if fn_ret.is_indirect() {
 840                         // Odd, but possible, case, we have an operand temporary,
 841                         // but the calling convention has an indirect return.
 842                         let tmp = PlaceRef::alloca(bx, fn_ret.layout, "tmp_ret");
 843                         tmp.storage_live(bx);
 844                         llargs.push(tmp.llval);
 845                         ReturnDest::IndirectOperand(tmp, index)
 846                     } else if is_intrinsic {
 847                         // Currently, intrinsics always need a location to store
 848                         // the result. so we create a temporary alloca for the
 849                         // result
 850                         let tmp = PlaceRef::alloca(bx, fn_ret.layout, "tmp_ret");
 851                         tmp.storage_live(bx);
 852                         ReturnDest::IndirectOperand(tmp, index)
 853                     } else {
 854                         ReturnDest::DirectOperand(index)
 855                     };
 856                 }
 857                 LocalRef::Operand(Some(_)) => {
 858                     bug!("place local already assigned to");
 859                 }
 860             }
 861         } else {
 862             self.codegen_place(bx, dest)
 863         };
 864         if fn_ret.is_indirect() {
 865             if dest.align.abi() < dest.layout.align.abi() {
 866                 // Currently, MIR code generation does not create calls
 867                 // that store directly to fields of packed structs (in
 868                 // fact, the calls it creates write only to temps),
 869                 //
 870                 // If someone changes that, please update this code path
 871                 // to create a temporary.
 872                 span_bug!(self.mir.span, "can't directly store to unaligned value");
 873             }
 874             llargs.push(dest.llval);
 875             ReturnDest::Nothing
 876         } else {
 877             ReturnDest::Store(dest)
 878         }
 879     }
 880
 881     fn codegen_transmute(&mut self, bx: &Builder<'a, 'll, 'tcx>,
 882                        src: &mir::Operand<'tcx>,
 883                        dst: &mir::Place<'tcx>) {
 884         if let mir::Place::Local(index) = *dst {
 885             match self.locals[index] {
 886                 LocalRef::Place(place) => self.codegen_transmute_into(bx, src, place),
 887                 LocalRef::UnsizedPlace(_) => bug!("transmute must not involve unsized locals"),
 888                 LocalRef::Operand(None) => {
 889                     let dst_layout = bx.cx.layout_of(self.monomorphized_place_ty(dst));
 890                     assert!(!dst_layout.ty.has_erasable_regions());
 891                     let place = PlaceRef::alloca(bx, dst_layout, "transmute_temp");
 892                     place.storage_live(bx);
 893                     self.codegen_transmute_into(bx, src, place);
 894                     let op = place.load(bx);
 895                     place.storage_dead(bx);
 896                     self.locals[index] = LocalRef::Operand(Some(op));
 897                 }
 898                 LocalRef::Operand(Some(op)) => {
 899                     assert!(op.layout.is_zst(),
 900                             "assigning to initialized SSAtemp");
 901                 }
 902             }
 903         } else {
 904             let dst = self.codegen_place(bx, dst);
 905             self.codegen_transmute_into(bx, src, dst);
 906         }
 907     }
 908
 909     fn codegen_transmute_into(&mut self, bx: &Builder<'a, 'll, 'tcx>,
 910                             src: &mir::Operand<'tcx>,
 911                             dst: PlaceRef<'ll, 'tcx>) {
 912         let src = self.codegen_operand(bx, src);
 913         let llty = src.layout.llvm_type(bx.cx);
 914         let cast_ptr = bx.pointercast(dst.llval, llty.ptr_to());
 915         let align = src.layout.align.min(dst.layout.align);
 916         src.val.store(bx, PlaceRef::new_sized(cast_ptr, src.layout, align));
 917     }
 918
 919
 920     // Stores the return value of a function call into it's final location.
 921     fn store_return(&mut self,
 922                     bx: &Builder<'a, 'll, 'tcx>,
 923                     dest: ReturnDest<'ll, 'tcx>,
 924                     ret_ty: &ArgType<'tcx, Ty<'tcx>>,
 925                     llval: &'ll Value) {
 926         use self::ReturnDest::*;
 927
 928         match dest {
 929             Nothing => (),
 930             Store(dst) => ret_ty.store(bx, llval, dst),
 931             IndirectOperand(tmp, index) => {
 932                 let op = tmp.load(bx);
 933                 tmp.storage_dead(bx);
 934                 self.locals[index] = LocalRef::Operand(Some(op));
 935             }
 936             DirectOperand(index) => {
 937                 // If there is a cast, we have to store and reload.
 938                 let op = if let PassMode::Cast(_) = ret_ty.mode {
 939                     let tmp = PlaceRef::alloca(bx, ret_ty.layout, "tmp_ret");
 940                     tmp.storage_live(bx);
 941                     ret_ty.store(bx, llval, tmp);
 942                     let op = tmp.load(bx);
 943                     tmp.storage_dead(bx);
 944                     op
 945                 } else {
 946                     OperandRef::from_immediate_or_packed_pair(bx, llval, ret_ty.layout)
 947                 };
 948                 self.locals[index] = LocalRef::Operand(Some(op));
 949             }
 950         }
 951     }
 952 }
 953
 954 enum ReturnDest<'ll, 'tcx> {
 955     // Do nothing, the return value is indirect or ignored
 956     Nothing,
 957     // Store the return value to the pointer
 958     Store(PlaceRef<'ll, 'tcx>),
 959     // Stores an indirect return value to an operand local place
 960     IndirectOperand(PlaceRef<'ll, 'tcx>, mir::Local),
 961     // Stores a direct return value to an operand local place
 962     DirectOperand(mir::Local)
 963 }