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, IntPredicate};
  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 interfaces::{BuilderMethods, CommonMethods, TypeMethods};
  30
  31 use syntax::symbol::Symbol;
  32 use syntax_pos::Pos;
  33
  34 use super::{FunctionCx, LocalRef};
  35 use super::place::PlaceRef;
  36 use super::operand::OperandRef;
  37 use super::operand::OperandValue::{Pair, Ref, Immediate};
  38
  39 impl FunctionCx<'a, 'll, 'tcx, &'ll Value> {
  40     pub fn codegen_block(&mut self, bb: mir::BasicBlock) {
  41         let mut bx = self.build_block(bb);
  42         let data = &self.mir[bb];
  43
  44         debug!("codegen_block({:?}={:?})", bb, data);
  45
  46         for statement in &data.statements {
  47             bx = self.codegen_statement(bx, statement);
  48         }
  49
  50         self.codegen_terminator(bx, bb, data.terminator());
  51     }
  52
  53     fn codegen_terminator(&mut self,
  54                           mut bx: Builder<'a, 'll, 'tcx>,
  55                           bb: mir::BasicBlock,
  56                           terminator: &mir::Terminator<'tcx>)
  57     {
  58         debug!("codegen_terminator: {:?}", terminator);
  59
  60         // Create the cleanup bundle, if needed.
  61         let tcx = bx.tcx();
  62         let span = terminator.source_info.span;
  63         let funclet_bb = self.cleanup_kinds[bb].funclet_bb(bb);
  64         let funclet = funclet_bb.and_then(|funclet_bb| self.funclets[funclet_bb].as_ref());
  65
  66         let cleanup_pad = funclet.map(|lp| lp.cleanuppad());
  67         let cleanup_bundle = funclet.map(|l| l.bundle());
  68
  69         let lltarget = |this: &mut Self, target: mir::BasicBlock| {
  70             let lltarget = this.blocks[target];
  71             let target_funclet = this.cleanup_kinds[target].funclet_bb(target);
  72             match (funclet_bb, target_funclet) {
  73                 (None, None) => (lltarget, false),
  74                 (Some(f), Some(t_f))
  75                     if f == t_f || !base::wants_msvc_seh(tcx.sess)
  76                     => (lltarget, false),
  77                 (None, Some(_)) => {
  78                     // jump *into* cleanup - need a landing pad if GNU
  79                     (this.landing_pad_to(target), false)
  80                 }
  81                 (Some(_), None) => span_bug!(span, "{:?} - jump out of cleanup?", terminator),
  82                 (Some(_), Some(_)) => {
  83                     (this.landing_pad_to(target), true)
  84                 }
  85             }
  86         };
  87
  88         let llblock = |this: &mut Self, target: mir::BasicBlock| {
  89             let (lltarget, is_cleanupret) = lltarget(this, target);
  90             if is_cleanupret {
  91                 // MSVC cross-funclet jump - need a trampoline
  92
  93                 debug!("llblock: creating cleanup trampoline for {:?}", target);
  94                 let name = &format!("{:?}_cleanup_trampoline_{:?}", bb, target);
  95                 let trampoline = this.new_block(name);
  96                 trampoline.cleanup_ret(cleanup_pad.unwrap(), Some(lltarget));
  97                 trampoline.llbb()
  98             } else {
  99                 lltarget
 100             }
 101         };
 102
 103         let funclet_br =
 104             |this: &mut Self, bx: Builder<'_, 'll, '_>, target: mir::BasicBlock| {
 105                 let (lltarget, is_cleanupret) = lltarget(this, target);
 106                 if is_cleanupret {
 107                     // micro-optimization: generate a `ret` rather than a jump
 108                     // to a trampoline.
 109                     bx.cleanup_ret(cleanup_pad.unwrap(), Some(lltarget));
 110                 } else {
 111                     bx.br(lltarget);
 112                 }
 113             };
 114
 115         let do_call = |
 116             this: &mut Self,
 117             bx: Builder<'a, 'll, 'tcx>,
 118             fn_ty: FnType<'tcx, Ty<'tcx>>,
 119             fn_ptr: &'ll Value,
 120             llargs: &[&'ll Value],
 121             destination: Option<(ReturnDest<'tcx, &'ll Value>, mir::BasicBlock)>,
 122             cleanup: Option<mir::BasicBlock>
 123         | {
 124             if let Some(cleanup) = cleanup {
 125                 let ret_bx = if let Some((_, target)) = destination {
 126                     this.blocks[target]
 127                 } else {
 128                     this.unreachable_block()
 129                 };
 130                 let invokeret = bx.invoke(fn_ptr,
 131                                           &llargs,
 132                                           ret_bx,
 133                                           llblock(this, cleanup),
 134                                           cleanup_bundle);
 135                 fn_ty.apply_attrs_callsite(&bx, invokeret);
 136
 137                 if let Some((ret_dest, target)) = destination {
 138                     let ret_bx = this.build_block(target);
 139                     this.set_debug_loc(&ret_bx, terminator.source_info);
 140                     this.store_return(&ret_bx, ret_dest, &fn_ty.ret, invokeret);
 141                 }
 142             } else {
 143                 let llret = bx.call(fn_ptr, &llargs, cleanup_bundle);
 144                 fn_ty.apply_attrs_callsite(&bx, llret);
 145                 if this.mir[bb].is_cleanup {
 146                     // Cleanup is always the cold path. Don't inline
 147                     // drop glue. Also, when there is a deeply-nested
 148                     // struct, there are "symmetry" issues that cause
 149                     // exponential inlining - see issue #41696.
 150                     llvm::Attribute::NoInline.apply_callsite(llvm::AttributePlace::Function, llret);
 151                 }
 152
 153                 if let Some((ret_dest, target)) = destination {
 154                     this.store_return(&bx, ret_dest, &fn_ty.ret, llret);
 155                     funclet_br(this, bx, target);
 156                 } else {
 157                     bx.unreachable();
 158                 }
 159             }
 160         };
 161
 162         self.set_debug_loc(&bx, terminator.source_info);
 163         match terminator.kind {
 164             mir::TerminatorKind::Resume => {
 165                 if let Some(cleanup_pad) = cleanup_pad {
 166                     bx.cleanup_ret(cleanup_pad, None);
 167                 } else {
 168                     let slot = self.get_personality_slot(&bx);
 169                     let lp0 = slot.project_field(&bx, 0).load(&bx).immediate();
 170                     let lp1 = slot.project_field(&bx, 1).load(&bx).immediate();
 171                     slot.storage_dead(&bx);
 172
 173                     if !bx.sess().target.target.options.custom_unwind_resume {
 174                         let mut lp = bx.cx().c_undef(self.landing_pad_type());
 175                         lp = bx.insert_value(lp, lp0, 0);
 176                         lp = bx.insert_value(lp, lp1, 1);
 177                         bx.resume(lp);
 178                     } else {
 179                         bx.call(bx.cx().eh_unwind_resume(), &[lp0], cleanup_bundle);
 180                         bx.unreachable();
 181                     }
 182                 }
 183             }
 184
 185             mir::TerminatorKind::Abort => {
 186                 // Call core::intrinsics::abort()
 187                 let fnname = bx.cx().get_intrinsic(&("llvm.trap"));
 188                 bx.call(fnname, &[], None);
 189                 bx.unreachable();
 190             }
 191
 192             mir::TerminatorKind::Goto { target } => {
 193                 funclet_br(self, bx, target);
 194             }
 195
 196             mir::TerminatorKind::SwitchInt { ref discr, switch_ty, ref values, ref targets } => {
 197                 let discr = self.codegen_operand(&bx, discr);
 198                 if targets.len() == 2 {
 199                     // If there are two targets, emit br instead of switch
 200                     let lltrue = llblock(self, targets[0]);
 201                     let llfalse = llblock(self, targets[1]);
 202                     if switch_ty == bx.tcx().types.bool {
 203                         // Don't generate trivial icmps when switching on bool
 204                         if let [0] = values[..] {
 205                             bx.cond_br(discr.immediate(), llfalse, lltrue);
 206                         } else {
 207                             assert_eq!(&values[..], &[1]);
 208                             bx.cond_br(discr.immediate(), lltrue, llfalse);
 209                         }
 210                     } else {
 211                         let switch_llty = bx.cx().layout_of(switch_ty).immediate_llvm_type(bx.cx());
 212                         let llval = bx.cx().c_uint_big(switch_llty, values[0]);
 213                         let cmp = bx.icmp(IntPredicate::IntEQ, discr.immediate(), llval);
 214                         bx.cond_br(cmp, lltrue, llfalse);
 215                     }
 216                 } else {
 217                     let (otherwise, targets) = targets.split_last().unwrap();
 218                     let switch = bx.switch(discr.immediate(),
 219                                            llblock(self, *otherwise),
 220                                            values.len());
 221                     let switch_llty = bx.cx().layout_of(switch_ty).immediate_llvm_type(bx.cx());
 222                     for (&value, target) in values.iter().zip(targets) {
 223                         let llval =bx.cx().c_uint_big(switch_llty, value);
 224                         let llbb = llblock(self, *target);
 225                         bx.add_case(switch, llval, llbb)
 226                     }
 227                 }
 228             }
 229
 230             mir::TerminatorKind::Return => {
 231                 let llval = match self.fn_ty.ret.mode {
 232                     PassMode::Ignore | PassMode::Indirect(..) => {
 233                         bx.ret_void();
 234                         return;
 235                     }
 236
 237                     PassMode::Direct(_) | PassMode::Pair(..) => {
 238                         let op = self.codegen_consume(&bx, &mir::Place::Local(mir::RETURN_PLACE));
 239                         if let Ref(llval, _, align) = op.val {
 240                             bx.load(llval, align)
 241                         } else {
 242                             op.immediate_or_packed_pair(&bx)
 243                         }
 244                     }
 245
 246                     PassMode::Cast(cast_ty) => {
 247                         let op = match self.locals[mir::RETURN_PLACE] {
 248                             LocalRef::Operand(Some(op)) => op,
 249                             LocalRef::Operand(None) => bug!("use of return before def"),
 250                             LocalRef::Place(cg_place) => {
 251                                 OperandRef {
 252                                     val: Ref(cg_place.llval, None, cg_place.align),
 253                                     layout: cg_place.layout
 254                                 }
 255                             }
 256                             LocalRef::UnsizedPlace(_) => bug!("return type must be sized"),
 257                         };
 258                         let llslot = match op.val {
 259                             Immediate(_) | Pair(..) => {
 260                                 let scratch = PlaceRef::alloca(&bx, self.fn_ty.ret.layout, "ret");
 261                                 op.val.store(&bx, scratch);
 262                                 scratch.llval
 263                             }
 264                             Ref(llval, _, align) => {
 265                                 assert_eq!(align.abi(), op.layout.align.abi(),
 266                                            "return place is unaligned!");
 267                                 llval
 268                             }
 269                         };
 270                         bx.load(
 271                             bx.pointercast(llslot, bx.cx().ptr_to(cast_ty.llvm_type(bx.cx()))),
 272                             self.fn_ty.ret.layout.align)
 273                     }
 274                 };
 275                 bx.ret(llval);
 276             }
 277
 278             mir::TerminatorKind::Unreachable => {
 279                 bx.unreachable();
 280             }
 281
 282             mir::TerminatorKind::Drop { ref location, target, unwind } => {
 283                 let ty = location.ty(self.mir, bx.tcx()).to_ty(bx.tcx());
 284                 let ty = self.monomorphize(&ty);
 285                 let drop_fn = monomorphize::resolve_drop_in_place(bx.cx().tcx, ty);
 286
 287                 if let ty::InstanceDef::DropGlue(_, None) = drop_fn.def {
 288                     // we don't actually need to drop anything.
 289                     funclet_br(self, bx, target);
 290                     return
 291                 }
 292
 293                 let place = self.codegen_place(&bx, location);
 294                 let (args1, args2);
 295                 let mut args = if let Some(llextra) = place.llextra {
 296                     args2 = [place.llval, llextra];
 297                     &args2[..]
 298                 } else {
 299                     args1 = [place.llval];
 300                     &args1[..]
 301                 };
 302                 let (drop_fn, fn_ty) = match ty.sty {
 303                     ty::Dynamic(..) => {
 304                         let sig = drop_fn.fn_sig(bx.tcx());
 305                         let sig = bx.tcx().normalize_erasing_late_bound_regions(
 306                             ty::ParamEnv::reveal_all(),
 307                             &sig,
 308                         );
 309                         let fn_ty = FnType::new_vtable(bx.cx(), sig, &[]);
 310                         let vtable = args[1];
 311                         args = &args[..1];
 312                         (meth::DESTRUCTOR.get_fn(&bx, vtable, &fn_ty), fn_ty)
 313                     }
 314                     _ => {
 315                         (callee::get_fn(bx.cx(), drop_fn),
 316                          FnType::of_instance(bx.cx(), &drop_fn))
 317                     }
 318                 };
 319                 do_call(self, bx, fn_ty, drop_fn, args,
 320                         Some((ReturnDest::Nothing, target)),
 321                         unwind);
 322             }
 323
 324             mir::TerminatorKind::Assert { ref cond, expected, ref msg, target, cleanup } => {
 325                 let cond = self.codegen_operand(&bx, cond).immediate();
 326                 let mut const_cond = bx.cx().const_to_opt_u128(cond, false).map(|c| c == 1);
 327
 328                 // This case can currently arise only from functions marked
 329                 // with #[rustc_inherit_overflow_checks] and inlined from
 330                 // another crate (mostly core::num generic/#[inline] fns),
 331                 // while the current crate doesn't use overflow checks.
 332                 // NOTE: Unlike binops, negation doesn't have its own
 333                 // checked operation, just a comparison with the minimum
 334                 // value, so we have to check for the assert message.
 335                 if !bx.cx().check_overflow {
 336                     if let mir::interpret::EvalErrorKind::OverflowNeg = *msg {
 337                         const_cond = Some(expected);
 338                     }
 339                 }
 340
 341                 // Don't codegen the panic block if success if known.
 342                 if const_cond == Some(expected) {
 343                     funclet_br(self, bx, target);
 344                     return;
 345                 }
 346
 347                 // Pass the condition through llvm.expect for branch hinting.
 348                 let expect = bx.cx().get_intrinsic(&"llvm.expect.i1");
 349                 let cond = bx.call(expect, &[cond, bx.cx().c_bool(expected)], None);
 350
 351                 // Create the failure block and the conditional branch to it.
 352                 let lltarget = llblock(self, target);
 353                 let panic_block = self.new_block("panic");
 354                 if expected {
 355                     bx.cond_br(cond, lltarget, panic_block.llbb());
 356                 } else {
 357                     bx.cond_br(cond, panic_block.llbb(), lltarget);
 358                 }
 359
 360                 // After this point, bx is the block for the call to panic.
 361                 bx = panic_block;
 362                 self.set_debug_loc(&bx, terminator.source_info);
 363
 364                 // Get the location information.
 365                 let loc = bx.sess().source_map().lookup_char_pos(span.lo());
 366                 let filename = Symbol::intern(&loc.file.name.to_string()).as_str();
 367                 let filename = bx.cx().c_str_slice(filename);
 368                 let line = bx.cx().c_u32(loc.line as u32);
 369                 let col = bx.cx().c_u32(loc.col.to_usize() as u32 + 1);
 370                 let align = tcx.data_layout.aggregate_align
 371                     .max(tcx.data_layout.i32_align)
 372                     .max(tcx.data_layout.pointer_align);
 373
 374                 // Put together the arguments to the panic entry point.
 375                 let (lang_item, args) = match *msg {
 376                     EvalErrorKind::BoundsCheck { ref len, ref index } => {
 377                         let len = self.codegen_operand(&mut bx, len).immediate();
 378                         let index = self.codegen_operand(&mut bx, index).immediate();
 379
 380                         let file_line_col = bx.cx().c_struct(&[filename, line, col], false);
 381                         let file_line_col = consts::addr_of(bx.cx(),
 382                                                             file_line_col,
 383                                                             align,
 384                                                             Some("panic_bounds_check_loc"));
 385                         (lang_items::PanicBoundsCheckFnLangItem,
 386                          vec![file_line_col, index, len])
 387                     }
 388                     _ => {
 389                         let str = msg.description();
 390                         let msg_str = Symbol::intern(str).as_str();
 391                         let msg_str = bx.cx().c_str_slice(msg_str);
 392                         let msg_file_line_col = bx.cx().c_struct(
 393                             &[msg_str, filename, line, col],
 394                             false
 395                         );
 396                         let msg_file_line_col = consts::addr_of(bx.cx(),
 397                                                                 msg_file_line_col,
 398                                                                 align,
 399                                                                 Some("panic_loc"));
 400                         (lang_items::PanicFnLangItem,
 401                          vec![msg_file_line_col])
 402                     }
 403                 };
 404
 405                 // Obtain the panic entry point.
 406                 let def_id = common::langcall(bx.tcx(), Some(span), "", lang_item);
 407                 let instance = ty::Instance::mono(bx.tcx(), def_id);
 408                 let fn_ty = FnType::of_instance(bx.cx(), &instance);
 409                 let llfn = callee::get_fn(bx.cx(), instance);
 410
 411                 // Codegen the actual panic invoke/call.
 412                 do_call(self, bx, fn_ty, llfn, &args, None, cleanup);
 413             }
 414
 415             mir::TerminatorKind::DropAndReplace { .. } => {
 416                 bug!("undesugared DropAndReplace in codegen: {:?}", terminator);
 417             }
 418
 419             mir::TerminatorKind::Call {
 420                 ref func,
 421                 ref args,
 422                 ref destination,
 423                 cleanup,
 424                 from_hir_call: _
 425             } => {
 426                 // Create the callee. This is a fn ptr or zero-sized and hence a kind of scalar.
 427                 let callee = self.codegen_operand(&bx, func);
 428
 429                 let (instance, mut llfn) = match callee.layout.ty.sty {
 430                     ty::FnDef(def_id, substs) => {
 431                         (Some(ty::Instance::resolve(bx.cx().tcx,
 432                                                     ty::ParamEnv::reveal_all(),
 433                                                     def_id,
 434                                                     substs).unwrap()),
 435                          None)
 436                     }
 437                     ty::FnPtr(_) => {
 438                         (None, Some(callee.immediate()))
 439                     }
 440                     _ => bug!("{} is not callable", callee.layout.ty)
 441                 };
 442                 let def = instance.map(|i| i.def);
 443                 let sig = callee.layout.ty.fn_sig(bx.tcx());
 444                 let sig = bx.tcx().normalize_erasing_late_bound_regions(
 445                     ty::ParamEnv::reveal_all(),
 446                     &sig,
 447                 );
 448                 let abi = sig.abi;
 449
 450                 // Handle intrinsics old codegen wants Expr's for, ourselves.
 451                 let intrinsic = match def {
 452                     Some(ty::InstanceDef::Intrinsic(def_id))
 453                         => Some(bx.tcx().item_name(def_id).as_str()),
 454                     _ => None
 455                 };
 456                 let intrinsic = intrinsic.as_ref().map(|s| &s[..]);
 457
 458                 if intrinsic == Some("transmute") {
 459                     if let Some(destination_ref) = destination.as_ref() {
 460                         let &(ref dest, target) = destination_ref;
 461                         self.codegen_transmute(&bx, &args[0], dest);
 462                         funclet_br(self, bx, target);
 463                     } else {
 464                         // If we are trying to transmute to an uninhabited type,
 465                         // it is likely there is no allotted destination. In fact,
 466                         // transmuting to an uninhabited type is UB, which means
 467                         // we can do what we like. Here, we declare that transmuting
 468                         // into an uninhabited type is impossible, so anything following
 469                         // it must be unreachable.
 470                         assert_eq!(bx.cx().layout_of(sig.output()).abi, layout::Abi::Uninhabited);
 471                         bx.unreachable();
 472                     }
 473                     return;
 474                 }
 475
 476                 let extra_args = &args[sig.inputs().len()..];
 477                 let extra_args = extra_args.iter().map(|op_arg| {
 478                     let op_ty = op_arg.ty(self.mir, bx.tcx());
 479                     self.monomorphize(&op_ty)
 480                 }).collect::<Vec<_>>();
 481
 482                 let fn_ty = match def {
 483                     Some(ty::InstanceDef::Virtual(..)) => {
 484                         FnType::new_vtable(bx.cx(), sig, &extra_args)
 485                     }
 486                     Some(ty::InstanceDef::DropGlue(_, None)) => {
 487                         // empty drop glue - a nop.
 488                         let &(_, target) = destination.as_ref().unwrap();
 489                         funclet_br(self, bx, target);
 490                         return;
 491                     }
 492                     _ => FnType::new(bx.cx(), sig, &extra_args)
 493                 };
 494
 495                 // emit a panic instead of instantiating an uninhabited type
 496                 if (intrinsic == Some("init") || intrinsic == Some("uninit")) &&
 497                     fn_ty.ret.layout.abi.is_uninhabited()
 498                 {
 499                     let loc = bx.sess().source_map().lookup_char_pos(span.lo());
 500                     let filename = Symbol::intern(&loc.file.name.to_string()).as_str();
 501                     let filename = bx.cx.c_str_slice(filename);
 502                     let line = bx.cx.c_u32(loc.line as u32);
 503                     let col = bx.cx.c_u32(loc.col.to_usize() as u32 + 1);
 504                     let align = tcx.data_layout.aggregate_align
 505                         .max(tcx.data_layout.i32_align)
 506                         .max(tcx.data_layout.pointer_align);
 507
 508                     let str = format!(
 509                         "Attempted to instantiate uninhabited type {} using mem::{}",
 510                         sig.output(),
 511                         if intrinsic == Some("init") { "zeroed" } else { "uninitialized" }
 512                     );
 513                     let msg_str = Symbol::intern(&str).as_str();
 514                     let msg_str = bx.cx.c_str_slice(msg_str);
 515                     let msg_file_line_col = bx.cx.c_struct(
 516                         &[msg_str, filename, line, col],
 517                         false,
 518                     );
 519                     let msg_file_line_col = consts::addr_of(bx.cx,
 520                                                             msg_file_line_col,
 521                                                             align,
 522                                                             Some("panic_loc"));
 523
 524                     // Obtain the panic entry point.
 525                     let def_id =
 526                         common::langcall(bx.tcx(), Some(span), "", lang_items::PanicFnLangItem);
 527                     let instance = ty::Instance::mono(bx.tcx(), def_id);
 528                     let fn_ty = FnType::of_instance(bx.cx, &instance);
 529                     let llfn = callee::get_fn(bx.cx, instance);
 530
 531                     // Codegen the actual panic invoke/call.
 532                     do_call(
 533                         self,
 534                         bx,
 535                         fn_ty,
 536                         llfn,
 537                         &[msg_file_line_col],
 538                         destination.as_ref().map(|(_, bb)| (ReturnDest::Nothing, *bb)),
 539                         cleanup,
 540                     );
 541                     return;
 542                 }
 543
 544                 // The arguments we'll be passing. Plus one to account for outptr, if used.
 545                 let arg_count = fn_ty.args.len() + fn_ty.ret.is_indirect() as usize;
 546                 let mut llargs = Vec::with_capacity(arg_count);
 547
 548                 // Prepare the return value destination
 549                 let ret_dest = if let Some((ref dest, _)) = *destination {
 550                     let is_intrinsic = intrinsic.is_some();
 551                     self.make_return_dest(&bx, dest, &fn_ty.ret, &mut llargs,
 552                                           is_intrinsic)
 553                 } else {
 554                     ReturnDest::Nothing
 555                 };
 556
 557                 if intrinsic.is_some() && intrinsic != Some("drop_in_place") {
 558                     use intrinsic::codegen_intrinsic_call;
 559
 560                     let dest = match ret_dest {
 561                         _ if fn_ty.ret.is_indirect() => llargs[0],
 562                         ReturnDest::Nothing => {
 563                             bx.cx().c_undef(bx.cx().ptr_to(fn_ty.ret.memory_ty(bx.cx())))
 564                         }
 565                         ReturnDest::IndirectOperand(dst, _) |
 566                         ReturnDest::Store(dst) => dst.llval,
 567                         ReturnDest::DirectOperand(_) =>
 568                             bug!("Cannot use direct operand with an intrinsic call")
 569                     };
 570
 571                     let args: Vec<_> = args.iter().enumerate().map(|(i, arg)| {
 572                         // The indices passed to simd_shuffle* in the
 573                         // third argument must be constant. This is
 574                         // checked by const-qualification, which also
 575                         // promotes any complex rvalues to constants.
 576                         if i == 2 && intrinsic.unwrap().starts_with("simd_shuffle") {
 577                             match *arg {
 578                                 // The shuffle array argument is usually not an explicit constant,
 579                                 // but specified directly in the code. This means it gets promoted
 580                                 // and we can then extract the value by evaluating the promoted.
 581                                 mir::Operand::Copy(mir::Place::Promoted(box(index, ty))) |
 582                                 mir::Operand::Move(mir::Place::Promoted(box(index, ty))) => {
 583                                     let param_env = ty::ParamEnv::reveal_all();
 584                                     let cid = mir::interpret::GlobalId {
 585                                         instance: self.instance,
 586                                         promoted: Some(index),
 587                                     };
 588                                     let c = bx.tcx().const_eval(param_env.and(cid));
 589                                     let (llval, ty) = self.simd_shuffle_indices(
 590                                         &bx,
 591                                         terminator.source_info.span,
 592                                         ty,
 593                                         c,
 594                                     );
 595                                     return OperandRef {
 596                                         val: Immediate(llval),
 597                                         layout: bx.cx().layout_of(ty),
 598                                     };
 599
 600                                 },
 601                                 mir::Operand::Copy(_) |
 602                                 mir::Operand::Move(_) => {
 603                                     span_bug!(span, "shuffle indices must be constant");
 604                                 }
 605                                 mir::Operand::Constant(ref constant) => {
 606                                     let c = self.eval_mir_constant(&bx, constant);
 607                                     let (llval, ty) = self.simd_shuffle_indices(
 608                                         &bx,
 609                                         constant.span,
 610                                         constant.ty,
 611                                         c,
 612                                     );
 613                                     return OperandRef {
 614                                         val: Immediate(llval),
 615                                         layout: bx.cx().layout_of(ty)
 616                                     };
 617                                 }
 618                             }
 619                         }
 620
 621                         self.codegen_operand(&bx, arg)
 622                     }).collect();
 623
 624
 625                     let callee_ty = instance.as_ref().unwrap().ty(bx.cx().tcx);
 626                     codegen_intrinsic_call(&bx, callee_ty, &fn_ty, &args, dest,
 627                                            terminator.source_info.span);
 628
 629                     if let ReturnDest::IndirectOperand(dst, _) = ret_dest {
 630                         self.store_return(&bx, ret_dest, &fn_ty.ret, dst.llval);
 631                     }
 632
 633                     if let Some((_, target)) = *destination {
 634                         funclet_br(self, bx, target);
 635                     } else {
 636                         bx.unreachable();
 637                     }
 638
 639                     return;
 640                 }
 641
 642                 // Split the rust-call tupled arguments off.
 643                 let (first_args, untuple) = if abi == Abi::RustCall && !args.is_empty() {
 644                     let (tup, args) = args.split_last().unwrap();
 645                     (args, Some(tup))
 646                 } else {
 647                     (&args[..], None)
 648                 };
 649
 650                 'make_args: for (i, arg) in first_args.iter().enumerate() {
 651                     let mut op = self.codegen_operand(&bx, arg);
 652
 653                     if let (0, Some(ty::InstanceDef::Virtual(_, idx))) = (i, def) {
 654                         if let Pair(..) = op.val {
 655                             // In the case of Rc<Self>, we need to explicitly pass a
 656                             // *mut RcBox<Self> with a Scalar (not ScalarPair) ABI. This is a hack
 657                             // that is understood elsewhere in the compiler as a method on
 658                             // `dyn Trait`.
 659                             // To get a `*mut RcBox<Self>`, we just keep unwrapping newtypes until
 660                             // we get a value of a built-in pointer type
 661                             'descend_newtypes: while !op.layout.ty.is_unsafe_ptr()
 662                                             && !op.layout.ty.is_region_ptr()
 663                             {
 664                                 'iter_fields: for i in 0..op.layout.fields.count() {
 665                                     let field = op.extract_field(&bx, i);
 666                                     if !field.layout.is_zst() {
 667                                         // we found the one non-zero-sized field that is allowed
 668                                         // now find *its* non-zero-sized field, or stop if it's a
 669                                         // pointer
 670                                         op = field;
 671                                         continue 'descend_newtypes
 672                                     }
 673                                 }
 674
 675                                 span_bug!(span, "receiver has no non-zero-sized fields {:?}", op);
 676                             }
 677
 678                             // now that we have `*dyn Trait` or `&dyn Trait`, split it up into its
 679                             // data pointer and vtable. Look up the method in the vtable, and pass
 680                             // the data pointer as the first argument
 681                             match op.val {
 682                                 Pair(data_ptr, meta) => {
 683                                     llfn = Some(meth::VirtualIndex::from_index(idx)
 684                                         .get_fn(&bx, meta, &fn_ty));
 685                                     llargs.push(data_ptr);
 686                                     continue 'make_args
 687                                 }
 688                                 other => bug!("expected a Pair, got {:?}", other)
 689                             }
 690                         } else if let Ref(data_ptr, Some(meta), _) = op.val {
 691                             // by-value dynamic dispatch
 692                             llfn = Some(meth::VirtualIndex::from_index(idx)
 693                                 .get_fn(&bx, meta, &fn_ty));
 694                             llargs.push(data_ptr);
 695                             continue;
 696                         } else {
 697                             span_bug!(span, "can't codegen a virtual call on {:?}", op);
 698                         }
 699                     }
 700
 701                     // The callee needs to own the argument memory if we pass it
 702                     // by-ref, so make a local copy of non-immediate constants.
 703                     match (arg, op.val) {
 704                         (&mir::Operand::Copy(_), Ref(_, None, _)) |
 705                         (&mir::Operand::Constant(_), Ref(_, None, _)) => {
 706                             let tmp = PlaceRef::alloca(&bx, op.layout, "const");
 707                             op.val.store(&bx, tmp);
 708                             op.val = Ref(tmp.llval, None, tmp.align);
 709                         }
 710                         _ => {}
 711                     }
 712
 713                     self.codegen_argument(&bx, op, &mut llargs, &fn_ty.args[i]);
 714                 }
 715                 if let Some(tup) = untuple {
 716                     self.codegen_arguments_untupled(&bx, tup, &mut llargs,
 717                         &fn_ty.args[first_args.len()..])
 718                 }
 719
 720                 let fn_ptr = match (llfn, instance) {
 721                     (Some(llfn), _) => llfn,
 722                     (None, Some(instance)) => callee::get_fn(bx.cx(), instance),
 723                     _ => span_bug!(span, "no llfn for call"),
 724                 };
 725
 726                 do_call(self, bx, fn_ty, fn_ptr, &llargs,
 727                         destination.as_ref().map(|&(_, target)| (ret_dest, target)),
 728                         cleanup);
 729             }
 730             mir::TerminatorKind::GeneratorDrop |
 731             mir::TerminatorKind::Yield { .. } => bug!("generator ops in codegen"),
 732             mir::TerminatorKind::FalseEdges { .. } |
 733             mir::TerminatorKind::FalseUnwind { .. } => bug!("borrowck false edges in codegen"),
 734         }
 735     }
 736
 737     fn codegen_argument(&mut self,
 738                       bx: &Builder<'a, 'll, 'tcx>,
 739                       op: OperandRef<'tcx, &'ll Value>,
 740                       llargs: &mut Vec<&'ll Value>,
 741                       arg: &ArgType<'tcx, Ty<'tcx>>) {
 742         // Fill padding with undef value, where applicable.
 743         if let Some(ty) = arg.pad {
 744             llargs.push(bx.cx().c_undef(ty.llvm_type(bx.cx())));
 745         }
 746
 747         if arg.is_ignore() {
 748             return;
 749         }
 750
 751         if let PassMode::Pair(..) = arg.mode {
 752             match op.val {
 753                 Pair(a, b) => {
 754                     llargs.push(a);
 755                     llargs.push(b);
 756                     return;
 757                 }
 758                 _ => bug!("codegen_argument: {:?} invalid for pair argument", op)
 759             }
 760         } else if arg.is_unsized_indirect() {
 761             match op.val {
 762                 Ref(a, Some(b), _) => {
 763                     llargs.push(a);
 764                     llargs.push(b);
 765                     return;
 766                 }
 767                 _ => bug!("codegen_argument: {:?} invalid for unsized indirect argument", op)
 768             }
 769         }
 770
 771         // Force by-ref if we have to load through a cast pointer.
 772         let (mut llval, align, by_ref) = match op.val {
 773             Immediate(_) | Pair(..) => {
 774                 match arg.mode {
 775                     PassMode::Indirect(..) | PassMode::Cast(_) => {
 776                         let scratch = PlaceRef::alloca(bx, arg.layout, "arg");
 777                         op.val.store(bx, scratch);
 778                         (scratch.llval, scratch.align, true)
 779                     }
 780                     _ => {
 781                         (op.immediate_or_packed_pair(bx), arg.layout.align, false)
 782                     }
 783                 }
 784             }
 785             Ref(llval, _, align) => {
 786                 if arg.is_indirect() && align.abi() < arg.layout.align.abi() {
 787                     // `foo(packed.large_field)`. We can't pass the (unaligned) field directly. I
 788                     // think that ATM (Rust 1.16) we only pass temporaries, but we shouldn't
 789                     // have scary latent bugs around.
 790
 791                     let scratch = PlaceRef::alloca(bx, arg.layout, "arg");
 792                     base::memcpy_ty(bx, scratch.llval, scratch.align, llval, align,
 793                                     op.layout, MemFlags::empty());
 794                     (scratch.llval, scratch.align, true)
 795                 } else {
 796                     (llval, align, true)
 797                 }
 798             }
 799         };
 800
 801         if by_ref && !arg.is_indirect() {
 802             // Have to load the argument, maybe while casting it.
 803             if let PassMode::Cast(ty) = arg.mode {
 804                 llval = bx.load(bx.pointercast(llval, bx.cx().ptr_to(ty.llvm_type(bx.cx()))),
 805                                 align.min(arg.layout.align));
 806             } else {
 807                 // We can't use `PlaceRef::load` here because the argument
 808                 // may have a type we don't treat as immediate, but the ABI
 809                 // used for this call is passing it by-value. In that case,
 810                 // the load would just produce `OperandValue::Ref` instead
 811                 // of the `OperandValue::Immediate` we need for the call.
 812                 llval = bx.load(llval, align);
 813                 if let layout::Abi::Scalar(ref scalar) = arg.layout.abi {
 814                     if scalar.is_bool() {
 815                         bx.range_metadata(llval, 0..2);
 816                     }
 817                 }
 818                 // We store bools as i8 so we need to truncate to i1.
 819                 llval = base::to_immediate(bx, llval, arg.layout);
 820             }
 821         }
 822
 823         llargs.push(llval);
 824     }
 825
 826     fn codegen_arguments_untupled(&mut self,
 827                                   bx: &Builder<'a, 'll, 'tcx>,
 828                                   operand: &mir::Operand<'tcx>,
 829                                   llargs: &mut Vec<&'ll Value>,
 830                                   args: &[ArgType<'tcx, Ty<'tcx>>]) {
 831         let tuple = self.codegen_operand(bx, operand);
 832
 833         // Handle both by-ref and immediate tuples.
 834         if let Ref(llval, None, align) = tuple.val {
 835             let tuple_ptr = PlaceRef::new_sized(llval, tuple.layout, align);
 836             for i in 0..tuple.layout.fields.count() {
 837                 let field_ptr = tuple_ptr.project_field(bx, i);
 838                 self.codegen_argument(bx, field_ptr.load(bx), llargs, &args[i]);
 839             }
 840         } else if let Ref(_, Some(_), _) = tuple.val {
 841             bug!("closure arguments must be sized")
 842         } else {
 843             // If the tuple is immediate, the elements are as well.
 844             for i in 0..tuple.layout.fields.count() {
 845                 let op = tuple.extract_field(bx, i);
 846                 self.codegen_argument(bx, op, llargs, &args[i]);
 847             }
 848         }
 849     }
 850
 851     fn get_personality_slot(
 852         &mut self,
 853         bx: &Builder<'a, 'll, 'tcx>
 854     ) -> PlaceRef<'tcx, &'ll Value> {
 855         let cx = bx.cx();
 856         if let Some(slot) = self.personality_slot {
 857             slot
 858         } else {
 859             let layout = cx.layout_of(cx.tcx.intern_tup(&[
 860                 cx.tcx.mk_mut_ptr(cx.tcx.types.u8),
 861                 cx.tcx.types.i32
 862             ]));
 863             let slot = PlaceRef::alloca(bx, layout, "personalityslot");
 864             self.personality_slot = Some(slot);
 865             slot
 866         }
 867     }
 868
 869     /// Return the landingpad wrapper around the given basic block
 870     ///
 871     /// No-op in MSVC SEH scheme.
 872     fn landing_pad_to(&mut self, target_bb: mir::BasicBlock) -> &'ll BasicBlock {
 873         if let Some(block) = self.landing_pads[target_bb] {
 874             return block;
 875         }
 876
 877         let block = self.blocks[target_bb];
 878         let landing_pad = self.landing_pad_uncached(block);
 879         self.landing_pads[target_bb] = Some(landing_pad);
 880         landing_pad
 881     }
 882
 883     fn landing_pad_uncached(&mut self, target_bb: &'ll BasicBlock) -> &'ll BasicBlock {
 884         if base::wants_msvc_seh(self.cx.sess()) {
 885             span_bug!(self.mir.span, "landing pad was not inserted?")
 886         }
 887
 888         let bx = self.new_block("cleanup");
 889
 890         let llpersonality = self.cx.eh_personality();
 891         let llretty = self.landing_pad_type();
 892         let lp = bx.landing_pad(llretty, llpersonality, 1);
 893         bx.set_cleanup(lp);
 894
 895         let slot = self.get_personality_slot(&bx);
 896         slot.storage_live(&bx);
 897         Pair(bx.extract_value(lp, 0), bx.extract_value(lp, 1)).store(&bx, slot);
 898
 899         bx.br(target_bb);
 900         bx.llbb()
 901     }
 902
 903     fn landing_pad_type(&self) -> &'ll Type {
 904         let cx = self.cx;
 905         cx.struct_( &[cx.i8p(), cx.i32()], false)
 906     }
 907
 908     fn unreachable_block(&mut self) -> &'ll BasicBlock {
 909         self.unreachable_block.unwrap_or_else(|| {
 910             let bl = self.new_block("unreachable");
 911             bl.unreachable();
 912             self.unreachable_block = Some(bl.llbb());
 913             bl.llbb()
 914         })
 915     }
 916
 917     pub fn new_block(&self, name: &str) -> Builder<'a, 'll, 'tcx> {
 918         Builder::new_block(self.cx, self.llfn, name)
 919     }
 920
 921     pub fn build_block(&self, bb: mir::BasicBlock) -> Builder<'a, 'll, 'tcx> {
 922         let bx = Builder::with_cx(self.cx);
 923         bx.position_at_end(self.blocks[bb]);
 924         bx
 925     }
 926
 927     fn make_return_dest(&mut self, bx: &Builder<'a, 'll, 'tcx>,
 928                         dest: &mir::Place<'tcx>, fn_ret: &ArgType<'tcx, Ty<'tcx>>,
 929                         llargs: &mut Vec<&'ll Value>, is_intrinsic: bool)
 930                         -> ReturnDest<'tcx, &'ll Value> {
 931         // If the return is ignored, we can just return a do-nothing ReturnDest
 932         if fn_ret.is_ignore() {
 933             return ReturnDest::Nothing;
 934         }
 935         let dest = if let mir::Place::Local(index) = *dest {
 936             match self.locals[index] {
 937                 LocalRef::Place(dest) => dest,
 938                 LocalRef::UnsizedPlace(_) => bug!("return type must be sized"),
 939                 LocalRef::Operand(None) => {
 940                     // Handle temporary places, specifically Operand ones, as
 941                     // they don't have allocas
 942                     return if fn_ret.is_indirect() {
 943                         // Odd, but possible, case, we have an operand temporary,
 944                         // but the calling convention has an indirect return.
 945                         let tmp = PlaceRef::alloca(bx, fn_ret.layout, "tmp_ret");
 946                         tmp.storage_live(bx);
 947                         llargs.push(tmp.llval);
 948                         ReturnDest::IndirectOperand(tmp, index)
 949                     } else if is_intrinsic {
 950                         // Currently, intrinsics always need a location to store
 951                         // the result. so we create a temporary alloca for the
 952                         // result
 953                         let tmp = PlaceRef::alloca(bx, fn_ret.layout, "tmp_ret");
 954                         tmp.storage_live(bx);
 955                         ReturnDest::IndirectOperand(tmp, index)
 956                     } else {
 957                         ReturnDest::DirectOperand(index)
 958                     };
 959                 }
 960                 LocalRef::Operand(Some(_)) => {
 961                     bug!("place local already assigned to");
 962                 }
 963             }
 964         } else {
 965             self.codegen_place(bx, dest)
 966         };
 967         if fn_ret.is_indirect() {
 968             if dest.align.abi() < dest.layout.align.abi() {
 969                 // Currently, MIR code generation does not create calls
 970                 // that store directly to fields of packed structs (in
 971                 // fact, the calls it creates write only to temps),
 972                 //
 973                 // If someone changes that, please update this code path
 974                 // to create a temporary.
 975                 span_bug!(self.mir.span, "can't directly store to unaligned value");
 976             }
 977             llargs.push(dest.llval);
 978             ReturnDest::Nothing
 979         } else {
 980             ReturnDest::Store(dest)
 981         }
 982     }
 983
 984     fn codegen_transmute(&mut self, bx: &Builder<'a, 'll, 'tcx>,
 985                          src: &mir::Operand<'tcx>,
 986                          dst: &mir::Place<'tcx>) {
 987         if let mir::Place::Local(index) = *dst {
 988             match self.locals[index] {
 989                 LocalRef::Place(place) => self.codegen_transmute_into(bx, src, place),
 990                 LocalRef::UnsizedPlace(_) => bug!("transmute must not involve unsized locals"),
 991                 LocalRef::Operand(None) => {
 992                     let dst_layout = bx.cx().layout_of(self.monomorphized_place_ty(dst));
 993                     assert!(!dst_layout.ty.has_erasable_regions());
 994                     let place = PlaceRef::alloca(bx, dst_layout, "transmute_temp");
 995                     place.storage_live(bx);
 996                     self.codegen_transmute_into(bx, src, place);
 997                     let op = place.load(bx);
 998                     place.storage_dead(bx);
 999                     self.locals[index] = LocalRef::Operand(Some(op));
1000                 }
1001                 LocalRef::Operand(Some(op)) => {
1002                     assert!(op.layout.is_zst(),
1003                             "assigning to initialized SSAtemp");
1004                 }
1005             }
1006         } else {
1007             let dst = self.codegen_place(bx, dst);
1008             self.codegen_transmute_into(bx, src, dst);
1009         }
1010     }
1011
1012     fn codegen_transmute_into(&mut self, bx: &Builder<'a, 'll, 'tcx>,
1013                               src: &mir::Operand<'tcx>,
1014                               dst: PlaceRef<'tcx, &'ll Value>) {
1015         let src = self.codegen_operand(bx, src);
1016         let llty = src.layout.llvm_type(bx.cx());
1017         let cast_ptr = bx.pointercast(dst.llval, bx.cx().ptr_to(llty));
1018         let align = src.layout.align.min(dst.layout.align);
1019         src.val.store(bx, PlaceRef::new_sized(cast_ptr, src.layout, align));
1020     }
1021
1022
1023     // Stores the return value of a function call into it's final location.
1024     fn store_return(&mut self,
1025                     bx: &Builder<'a, 'll, 'tcx>,
1026                     dest: ReturnDest<'tcx, &'ll Value>,
1027                     ret_ty: &ArgType<'tcx, Ty<'tcx>>,
1028                     llval: &'ll Value) {
1029         use self::ReturnDest::*;
1030
1031         match dest {
1032             Nothing => (),
1033             Store(dst) => ret_ty.store(bx, llval, dst),
1034             IndirectOperand(tmp, index) => {
1035                 let op = tmp.load(bx);
1036                 tmp.storage_dead(bx);
1037                 self.locals[index] = LocalRef::Operand(Some(op));
1038             }
1039             DirectOperand(index) => {
1040                 // If there is a cast, we have to store and reload.
1041                 let op = if let PassMode::Cast(_) = ret_ty.mode {
1042                     let tmp = PlaceRef::alloca(bx, ret_ty.layout, "tmp_ret");
1043                     tmp.storage_live(bx);
1044                     ret_ty.store(bx, llval, tmp);
1045                     let op = tmp.load(bx);
1046                     tmp.storage_dead(bx);
1047                     op
1048                 } else {
1049                     OperandRef::from_immediate_or_packed_pair(bx, llval, ret_ty.layout)
1050                 };
1051                 self.locals[index] = LocalRef::Operand(Some(op));
1052             }
1053         }
1054     }
1055 }
1056
1057 enum ReturnDest<'tcx, V> {
1058     // Do nothing, the return value is indirect or ignored
1059     Nothing,
1060     // Store the return value to the pointer
1061     Store(PlaceRef<'tcx, V>),
1062     // Stores an indirect return value to an operand local place
1063     IndirectOperand(PlaceRef<'tcx, V>, mir::Local),
1064     // Stores a direct return value to an operand local place
1065     DirectOperand(mir::Local)
1066 }