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 traits::{IntPredicate,BuilderMethods};
  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, '_, &'ll Value>, 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 = 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 = 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 = 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, cast_ty.llvm_type(bx.cx).ptr_to()),
 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.cx.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 = common::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, C_bool(bx.cx, 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 = C_str_slice(bx.cx, filename);
 368                 let line = C_u32(bx.cx, loc.line as u32);
 369                 let col = C_u32(bx.cx, 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 = C_struct(bx.cx, &[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 = C_str_slice(bx.cx, msg_str);
 392                         let msg_file_line_col = C_struct(bx.cx,
 393                                                          &[msg_str, filename, line, col],
 394                                                          false);
 395                         let msg_file_line_col = consts::addr_of(bx.cx,
 396                                                                 msg_file_line_col,
 397                                                                 align,
 398                                                                 Some("panic_loc"));
 399                         (lang_items::PanicFnLangItem,
 400                          vec![msg_file_line_col])
 401                     }
 402                 };
 403
 404                 // Obtain the panic entry point.
 405                 let def_id = common::langcall(bx.tcx(), Some(span), "", lang_item);
 406                 let instance = ty::Instance::mono(bx.tcx(), def_id);
 407                 let fn_ty = FnType::of_instance(bx.cx, &instance);
 408                 let llfn = callee::get_fn(bx.cx, instance);
 409
 410                 // Codegen the actual panic invoke/call.
 411                 do_call(self, bx, fn_ty, llfn, &args, None, cleanup);
 412             }
 413
 414             mir::TerminatorKind::DropAndReplace { .. } => {
 415                 bug!("undesugared DropAndReplace in codegen: {:?}", terminator);
 416             }
 417
 418             mir::TerminatorKind::Call {
 419                 ref func,
 420                 ref args,
 421                 ref destination,
 422                 cleanup,
 423                 from_hir_call: _
 424             } => {
 425                 // Create the callee. This is a fn ptr or zero-sized and hence a kind of scalar.
 426                 let callee = self.codegen_operand(&bx, func);
 427
 428                 let (instance, mut llfn) = match callee.layout.ty.sty {
 429                     ty::FnDef(def_id, substs) => {
 430                         (Some(ty::Instance::resolve(bx.cx.tcx,
 431                                                     ty::ParamEnv::reveal_all(),
 432                                                     def_id,
 433                                                     substs).unwrap()),
 434                          None)
 435                     }
 436                     ty::FnPtr(_) => {
 437                         (None, Some(callee.immediate()))
 438                     }
 439                     _ => bug!("{} is not callable", callee.layout.ty)
 440                 };
 441                 let def = instance.map(|i| i.def);
 442                 let sig = callee.layout.ty.fn_sig(bx.tcx());
 443                 let sig = bx.tcx().normalize_erasing_late_bound_regions(
 444                     ty::ParamEnv::reveal_all(),
 445                     &sig,
 446                 );
 447                 let abi = sig.abi;
 448
 449                 // Handle intrinsics old codegen wants Expr's for, ourselves.
 450                 let intrinsic = match def {
 451                     Some(ty::InstanceDef::Intrinsic(def_id))
 452                         => Some(bx.tcx().item_name(def_id).as_str()),
 453                     _ => None
 454                 };
 455                 let intrinsic = intrinsic.as_ref().map(|s| &s[..]);
 456
 457                 if intrinsic == Some("transmute") {
 458                     if let Some(destination_ref) = destination.as_ref() {
 459                         let &(ref dest, target) = destination_ref;
 460                         self.codegen_transmute(&bx, &args[0], dest);
 461                         funclet_br(self, bx, target);
 462                     } else {
 463                         // If we are trying to transmute to an uninhabited type,
 464                         // it is likely there is no allotted destination. In fact,
 465                         // transmuting to an uninhabited type is UB, which means
 466                         // we can do what we like. Here, we declare that transmuting
 467                         // into an uninhabited type is impossible, so anything following
 468                         // it must be unreachable.
 469                         assert_eq!(bx.cx.layout_of(sig.output()).abi, layout::Abi::Uninhabited);
 470                         bx.unreachable();
 471                     }
 472                     return;
 473                 }
 474
 475                 let extra_args = &args[sig.inputs().len()..];
 476                 let extra_args = extra_args.iter().map(|op_arg| {
 477                     let op_ty = op_arg.ty(self.mir, bx.tcx());
 478                     self.monomorphize(&op_ty)
 479                 }).collect::<Vec<_>>();
 480
 481                 let fn_ty = match def {
 482                     Some(ty::InstanceDef::Virtual(..)) => {
 483                         FnType::new_vtable(bx.cx, sig, &extra_args)
 484                     }
 485                     Some(ty::InstanceDef::DropGlue(_, None)) => {
 486                         // empty drop glue - a nop.
 487                         let &(_, target) = destination.as_ref().unwrap();
 488                         funclet_br(self, bx, target);
 489                         return;
 490                     }
 491                     _ => FnType::new(bx.cx, sig, &extra_args)
 492                 };
 493
 494                 // emit a panic instead of instantiating an uninhabited type
 495                 if (intrinsic == Some("init") || intrinsic == Some("uninit")) &&
 496                     fn_ty.ret.layout.abi.is_uninhabited()
 497                 {
 498                     let loc = bx.sess().source_map().lookup_char_pos(span.lo());
 499                     let filename = Symbol::intern(&loc.file.name.to_string()).as_str();
 500                     let filename = C_str_slice(bx.cx, filename);
 501                     let line = C_u32(bx.cx, loc.line as u32);
 502                     let col = C_u32(bx.cx, loc.col.to_usize() as u32 + 1);
 503                     let align = tcx.data_layout.aggregate_align
 504                         .max(tcx.data_layout.i32_align)
 505                         .max(tcx.data_layout.pointer_align);
 506
 507                     let str = format!(
 508                         "Attempted to instantiate uninhabited type {} using mem::{}",
 509                         sig.output(),
 510                         if intrinsic == Some("init") { "zeroed" } else { "uninitialized" }
 511                     );
 512                     let msg_str = Symbol::intern(&str).as_str();
 513                     let msg_str = C_str_slice(bx.cx, msg_str);
 514                     let msg_file_line_col = C_struct(bx.cx,
 515                                                      &[msg_str, filename, line, col],
 516                                                      false);
 517                     let msg_file_line_col = consts::addr_of(bx.cx,
 518                                                             msg_file_line_col,
 519                                                             align,
 520                                                             Some("panic_loc"));
 521
 522                     // Obtain the panic entry point.
 523                     let def_id =
 524                         common::langcall(bx.tcx(), Some(span), "", lang_items::PanicFnLangItem);
 525                     let instance = ty::Instance::mono(bx.tcx(), def_id);
 526                     let fn_ty = FnType::of_instance(bx.cx, &instance);
 527                     let llfn = callee::get_fn(bx.cx, instance);
 528
 529                     // Codegen the actual panic invoke/call.
 530                     do_call(
 531                         self,
 532                         bx,
 533                         fn_ty,
 534                         llfn,
 535                         &[msg_file_line_col],
 536                         destination.as_ref().map(|(_, bb)| (ReturnDest::Nothing, *bb)),
 537                         cleanup,
 538                     );
 539                     return;
 540                 }
 541
 542                 // The arguments we'll be passing. Plus one to account for outptr, if used.
 543                 let arg_count = fn_ty.args.len() + fn_ty.ret.is_indirect() as usize;
 544                 let mut llargs = Vec::with_capacity(arg_count);
 545
 546                 // Prepare the return value destination
 547                 let ret_dest = if let Some((ref dest, _)) = *destination {
 548                     let is_intrinsic = intrinsic.is_some();
 549                     self.make_return_dest(&bx, dest, &fn_ty.ret, &mut llargs,
 550                                           is_intrinsic)
 551                 } else {
 552                     ReturnDest::Nothing
 553                 };
 554
 555                 if intrinsic.is_some() && intrinsic != Some("drop_in_place") {
 556                     use intrinsic::codegen_intrinsic_call;
 557
 558                     let dest = match ret_dest {
 559                         _ if fn_ty.ret.is_indirect() => llargs[0],
 560                         ReturnDest::Nothing => {
 561                             C_undef(fn_ty.ret.memory_ty(bx.cx).ptr_to())
 562                         }
 563                         ReturnDest::IndirectOperand(dst, _) |
 564                         ReturnDest::Store(dst) => dst.llval,
 565                         ReturnDest::DirectOperand(_) =>
 566                             bug!("Cannot use direct operand with an intrinsic call")
 567                     };
 568
 569                     let args: Vec<_> = args.iter().enumerate().map(|(i, arg)| {
 570                         // The indices passed to simd_shuffle* in the
 571                         // third argument must be constant. This is
 572                         // checked by const-qualification, which also
 573                         // promotes any complex rvalues to constants.
 574                         if i == 2 && intrinsic.unwrap().starts_with("simd_shuffle") {
 575                             match *arg {
 576                                 // The shuffle array argument is usually not an explicit constant,
 577                                 // but specified directly in the code. This means it gets promoted
 578                                 // and we can then extract the value by evaluating the promoted.
 579                                 mir::Operand::Copy(mir::Place::Promoted(box(index, ty))) |
 580                                 mir::Operand::Move(mir::Place::Promoted(box(index, ty))) => {
 581                                     let param_env = ty::ParamEnv::reveal_all();
 582                                     let cid = mir::interpret::GlobalId {
 583                                         instance: self.instance,
 584                                         promoted: Some(index),
 585                                     };
 586                                     let c = bx.tcx().const_eval(param_env.and(cid));
 587                                     let (llval, ty) = self.simd_shuffle_indices(
 588                                         &bx,
 589                                         terminator.source_info.span,
 590                                         ty,
 591                                         c,
 592                                     );
 593                                     return OperandRef {
 594                                         val: Immediate(llval),
 595                                         layout: bx.cx.layout_of(ty),
 596                                     };
 597
 598                                 },
 599                                 mir::Operand::Copy(_) |
 600                                 mir::Operand::Move(_) => {
 601                                     span_bug!(span, "shuffle indices must be constant");
 602                                 }
 603                                 mir::Operand::Constant(ref constant) => {
 604                                     let c = self.eval_mir_constant(&bx, constant);
 605                                     let (llval, ty) = self.simd_shuffle_indices(
 606                                         &bx,
 607                                         constant.span,
 608                                         constant.ty,
 609                                         c,
 610                                     );
 611                                     return OperandRef {
 612                                         val: Immediate(llval),
 613                                         layout: bx.cx.layout_of(ty)
 614                                     };
 615                                 }
 616                             }
 617                         }
 618
 619                         self.codegen_operand(&bx, arg)
 620                     }).collect();
 621
 622
 623                     let callee_ty = instance.as_ref().unwrap().ty(bx.cx.tcx);
 624                     codegen_intrinsic_call(&bx, callee_ty, &fn_ty, &args, dest,
 625                                            terminator.source_info.span);
 626
 627                     if let ReturnDest::IndirectOperand(dst, _) = ret_dest {
 628                         self.store_return(&bx, ret_dest, &fn_ty.ret, dst.llval);
 629                     }
 630
 631                     if let Some((_, target)) = *destination {
 632                         funclet_br(self, bx, target);
 633                     } else {
 634                         bx.unreachable();
 635                     }
 636
 637                     return;
 638                 }
 639
 640                 // Split the rust-call tupled arguments off.
 641                 let (first_args, untuple) = if abi == Abi::RustCall && !args.is_empty() {
 642                     let (tup, args) = args.split_last().unwrap();
 643                     (args, Some(tup))
 644                 } else {
 645                     (&args[..], None)
 646                 };
 647
 648                 'make_args: for (i, arg) in first_args.iter().enumerate() {
 649                     let mut op = self.codegen_operand(&bx, arg);
 650
 651                     if let (0, Some(ty::InstanceDef::Virtual(_, idx))) = (i, def) {
 652                         if let Pair(..) = op.val {
 653                             // In the case of Rc<Self>, we need to explicitly pass a
 654                             // *mut RcBox<Self> with a Scalar (not ScalarPair) ABI. This is a hack
 655                             // that is understood elsewhere in the compiler as a method on
 656                             // `dyn Trait`.
 657                             // To get a `*mut RcBox<Self>`, we just keep unwrapping newtypes until
 658                             // we get a value of a built-in pointer type
 659                             'descend_newtypes: while !op.layout.ty.is_unsafe_ptr()
 660                                             && !op.layout.ty.is_region_ptr()
 661                             {
 662                                 'iter_fields: for i in 0..op.layout.fields.count() {
 663                                     let field = op.extract_field(&bx, i);
 664                                     if !field.layout.is_zst() {
 665                                         // we found the one non-zero-sized field that is allowed
 666                                         // now find *its* non-zero-sized field, or stop if it's a
 667                                         // pointer
 668                                         op = field;
 669                                         continue 'descend_newtypes
 670                                     }
 671                                 }
 672
 673                                 span_bug!(span, "receiver has no non-zero-sized fields {:?}", op);
 674                             }
 675
 676                             // now that we have `*dyn Trait` or `&dyn Trait`, split it up into its
 677                             // data pointer and vtable. Look up the method in the vtable, and pass
 678                             // the data pointer as the first argument
 679                             match op.val {
 680                                 Pair(data_ptr, meta) => {
 681                                     llfn = Some(meth::VirtualIndex::from_index(idx)
 682                                         .get_fn(&bx, meta, &fn_ty));
 683                                     llargs.push(data_ptr);
 684                                     continue 'make_args
 685                                 }
 686                                 other => bug!("expected a Pair, got {:?}", other)
 687                             }
 688                         } else if let Ref(data_ptr, Some(meta), _) = op.val {
 689                             // by-value dynamic dispatch
 690                             llfn = Some(meth::VirtualIndex::from_index(idx)
 691                                 .get_fn(&bx, meta, &fn_ty));
 692                             llargs.push(data_ptr);
 693                             continue;
 694                         } else {
 695                             span_bug!(span, "can't codegen a virtual call on {:?}", op);
 696                         }
 697                     }
 698
 699                     // The callee needs to own the argument memory if we pass it
 700                     // by-ref, so make a local copy of non-immediate constants.
 701                     match (arg, op.val) {
 702                         (&mir::Operand::Copy(_), Ref(_, None, _)) |
 703                         (&mir::Operand::Constant(_), Ref(_, None, _)) => {
 704                             let tmp = PlaceRef::alloca(&bx, op.layout, "const");
 705                             op.val.store(&bx, tmp);
 706                             op.val = Ref(tmp.llval, None, tmp.align);
 707                         }
 708                         _ => {}
 709                     }
 710
 711                     self.codegen_argument(&bx, op, &mut llargs, &fn_ty.args[i]);
 712                 }
 713                 if let Some(tup) = untuple {
 714                     self.codegen_arguments_untupled(&bx, tup, &mut llargs,
 715                         &fn_ty.args[first_args.len()..])
 716                 }
 717
 718                 let fn_ptr = match (llfn, instance) {
 719                     (Some(llfn), _) => llfn,
 720                     (None, Some(instance)) => callee::get_fn(bx.cx, instance),
 721                     _ => span_bug!(span, "no llfn for call"),
 722                 };
 723
 724                 do_call(self, bx, fn_ty, fn_ptr, &llargs,
 725                         destination.as_ref().map(|&(_, target)| (ret_dest, target)),
 726                         cleanup);
 727             }
 728             mir::TerminatorKind::GeneratorDrop |
 729             mir::TerminatorKind::Yield { .. } => bug!("generator ops in codegen"),
 730             mir::TerminatorKind::FalseEdges { .. } |
 731             mir::TerminatorKind::FalseUnwind { .. } => bug!("borrowck false edges in codegen"),
 732         }
 733     }
 734
 735     fn codegen_argument(&mut self,
 736                       bx: &Builder<'a, 'll, 'tcx>,
 737                       op: OperandRef<'tcx, &'ll Value>,
 738                       llargs: &mut Vec<&'ll Value>,
 739                       arg: &ArgType<'tcx, Ty<'tcx>>) {
 740         // Fill padding with undef value, where applicable.
 741         if let Some(ty) = arg.pad {
 742             llargs.push(C_undef(ty.llvm_type(bx.cx)));
 743         }
 744
 745         if arg.is_ignore() {
 746             return;
 747         }
 748
 749         if let PassMode::Pair(..) = arg.mode {
 750             match op.val {
 751                 Pair(a, b) => {
 752                     llargs.push(a);
 753                     llargs.push(b);
 754                     return;
 755                 }
 756                 _ => bug!("codegen_argument: {:?} invalid for pair argument", op)
 757             }
 758         } else if arg.is_unsized_indirect() {
 759             match op.val {
 760                 Ref(a, Some(b), _) => {
 761                     llargs.push(a);
 762                     llargs.push(b);
 763                     return;
 764                 }
 765                 _ => bug!("codegen_argument: {:?} invalid for unsized indirect argument", op)
 766             }
 767         }
 768
 769         // Force by-ref if we have to load through a cast pointer.
 770         let (mut llval, align, by_ref) = match op.val {
 771             Immediate(_) | Pair(..) => {
 772                 match arg.mode {
 773                     PassMode::Indirect(..) | PassMode::Cast(_) => {
 774                         let scratch = PlaceRef::alloca(bx, arg.layout, "arg");
 775                         op.val.store(bx, scratch);
 776                         (scratch.llval, scratch.align, true)
 777                     }
 778                     _ => {
 779                         (op.immediate_or_packed_pair(bx), arg.layout.align, false)
 780                     }
 781                 }
 782             }
 783             Ref(llval, _, align) => {
 784                 if arg.is_indirect() && align.abi() < arg.layout.align.abi() {
 785                     // `foo(packed.large_field)`. We can't pass the (unaligned) field directly. I
 786                     // think that ATM (Rust 1.16) we only pass temporaries, but we shouldn't
 787                     // have scary latent bugs around.
 788
 789                     let scratch = PlaceRef::alloca(bx, arg.layout, "arg");
 790                     base::memcpy_ty(bx, scratch.llval, scratch.align, llval, align,
 791                                     op.layout, MemFlags::empty());
 792                     (scratch.llval, scratch.align, true)
 793                 } else {
 794                     (llval, align, true)
 795                 }
 796             }
 797         };
 798
 799         if by_ref && !arg.is_indirect() {
 800             // Have to load the argument, maybe while casting it.
 801             if let PassMode::Cast(ty) = arg.mode {
 802                 llval = bx.load(bx.pointercast(llval, ty.llvm_type(bx.cx).ptr_to()),
 803                                 align.min(arg.layout.align));
 804             } else {
 805                 // We can't use `PlaceRef::load` here because the argument
 806                 // may have a type we don't treat as immediate, but the ABI
 807                 // used for this call is passing it by-value. In that case,
 808                 // the load would just produce `OperandValue::Ref` instead
 809                 // of the `OperandValue::Immediate` we need for the call.
 810                 llval = bx.load(llval, align);
 811                 if let layout::Abi::Scalar(ref scalar) = arg.layout.abi {
 812                     if scalar.is_bool() {
 813                         bx.range_metadata(llval, 0..2);
 814                     }
 815                 }
 816                 // We store bools as i8 so we need to truncate to i1.
 817                 llval = base::to_immediate(bx, llval, arg.layout);
 818             }
 819         }
 820
 821         llargs.push(llval);
 822     }
 823
 824     fn codegen_arguments_untupled(&mut self,
 825                                   bx: &Builder<'a, 'll, 'tcx>,
 826                                   operand: &mir::Operand<'tcx>,
 827                                   llargs: &mut Vec<&'ll Value>,
 828                                   args: &[ArgType<'tcx, Ty<'tcx>>]) {
 829         let tuple = self.codegen_operand(bx, operand);
 830
 831         // Handle both by-ref and immediate tuples.
 832         if let Ref(llval, None, align) = tuple.val {
 833             let tuple_ptr = PlaceRef::new_sized(llval, tuple.layout, align);
 834             for i in 0..tuple.layout.fields.count() {
 835                 let field_ptr = tuple_ptr.project_field(bx, i);
 836                 self.codegen_argument(bx, field_ptr.load(bx), llargs, &args[i]);
 837             }
 838         } else if let Ref(_, Some(_), _) = tuple.val {
 839             bug!("closure arguments must be sized")
 840         } else {
 841             // If the tuple is immediate, the elements are as well.
 842             for i in 0..tuple.layout.fields.count() {
 843                 let op = tuple.extract_field(bx, i);
 844                 self.codegen_argument(bx, op, llargs, &args[i]);
 845             }
 846         }
 847     }
 848
 849     fn get_personality_slot(
 850         &mut self,
 851         bx: &Builder<'a, 'll, 'tcx, &'ll Value>
 852     ) -> PlaceRef<'tcx, &'ll Value> {
 853         let cx = bx.cx;
 854         if let Some(slot) = self.personality_slot {
 855             slot
 856         } else {
 857             let layout = cx.layout_of(cx.tcx.intern_tup(&[
 858                 cx.tcx.mk_mut_ptr(cx.tcx.types.u8),
 859                 cx.tcx.types.i32
 860             ]));
 861             let slot = PlaceRef::alloca(bx, layout, "personalityslot");
 862             self.personality_slot = Some(slot);
 863             slot
 864         }
 865     }
 866
 867     /// Return the landingpad wrapper around the given basic block
 868     ///
 869     /// No-op in MSVC SEH scheme.
 870     fn landing_pad_to(&mut self, target_bb: mir::BasicBlock) -> &'ll BasicBlock {
 871         if let Some(block) = self.landing_pads[target_bb] {
 872             return block;
 873         }
 874
 875         let block = self.blocks[target_bb];
 876         let landing_pad = self.landing_pad_uncached(block);
 877         self.landing_pads[target_bb] = Some(landing_pad);
 878         landing_pad
 879     }
 880
 881     fn landing_pad_uncached(&mut self, target_bb: &'ll BasicBlock) -> &'ll BasicBlock {
 882         if base::wants_msvc_seh(self.cx.sess()) {
 883             span_bug!(self.mir.span, "landing pad was not inserted?")
 884         }
 885
 886         let bx = self.new_block("cleanup");
 887
 888         let llpersonality = self.cx.eh_personality();
 889         let llretty = self.landing_pad_type();
 890         let lp = bx.landing_pad(llretty, llpersonality, 1);
 891         bx.set_cleanup(lp);
 892
 893         let slot = self.get_personality_slot(&bx);
 894         slot.storage_live(&bx);
 895         Pair(bx.extract_value(lp, 0), bx.extract_value(lp, 1)).store(&bx, slot);
 896
 897         bx.br(target_bb);
 898         bx.llbb()
 899     }
 900
 901     fn landing_pad_type(&self) -> &'ll Type {
 902         let cx = self.cx;
 903         Type::struct_(cx, &[Type::i8p(cx), Type::i32(cx)], false)
 904     }
 905
 906     fn unreachable_block(&mut self) -> &'ll BasicBlock {
 907         self.unreachable_block.unwrap_or_else(|| {
 908             let bl = self.new_block("unreachable");
 909             bl.unreachable();
 910             self.unreachable_block = Some(bl.llbb());
 911             bl.llbb()
 912         })
 913     }
 914
 915     pub fn new_block(&self, name: &str) -> Builder<'a, 'll, 'tcx> {
 916         Builder::new_block(self.cx, self.llfn, name)
 917     }
 918
 919     pub fn build_block(&self, bb: mir::BasicBlock) -> Builder<'a, 'll, 'tcx> {
 920         let bx = Builder::with_cx(self.cx);
 921         bx.position_at_end(self.blocks[bb]);
 922         bx
 923     }
 924
 925     fn make_return_dest(&mut self, bx: &Builder<'a, 'll, 'tcx>,
 926                         dest: &mir::Place<'tcx>, fn_ret: &ArgType<'tcx, Ty<'tcx>>,
 927                         llargs: &mut Vec<&'ll Value>, is_intrinsic: bool)
 928                         -> ReturnDest<'tcx, &'ll Value> {
 929         // If the return is ignored, we can just return a do-nothing ReturnDest
 930         if fn_ret.is_ignore() {
 931             return ReturnDest::Nothing;
 932         }
 933         let dest = if let mir::Place::Local(index) = *dest {
 934             match self.locals[index] {
 935                 LocalRef::Place(dest) => dest,
 936                 LocalRef::UnsizedPlace(_) => bug!("return type must be sized"),
 937                 LocalRef::Operand(None) => {
 938                     // Handle temporary places, specifically Operand ones, as
 939                     // they don't have allocas
 940                     return if fn_ret.is_indirect() {
 941                         // Odd, but possible, case, we have an operand temporary,
 942                         // but the calling convention has an indirect return.
 943                         let tmp = PlaceRef::alloca(bx, fn_ret.layout, "tmp_ret");
 944                         tmp.storage_live(bx);
 945                         llargs.push(tmp.llval);
 946                         ReturnDest::IndirectOperand(tmp, index)
 947                     } else if is_intrinsic {
 948                         // Currently, intrinsics always need a location to store
 949                         // the result. so we create a temporary alloca for the
 950                         // result
 951                         let tmp = PlaceRef::alloca(bx, fn_ret.layout, "tmp_ret");
 952                         tmp.storage_live(bx);
 953                         ReturnDest::IndirectOperand(tmp, index)
 954                     } else {
 955                         ReturnDest::DirectOperand(index)
 956                     };
 957                 }
 958                 LocalRef::Operand(Some(_)) => {
 959                     bug!("place local already assigned to");
 960                 }
 961             }
 962         } else {
 963             self.codegen_place(bx, dest)
 964         };
 965         if fn_ret.is_indirect() {
 966             if dest.align.abi() < dest.layout.align.abi() {
 967                 // Currently, MIR code generation does not create calls
 968                 // that store directly to fields of packed structs (in
 969                 // fact, the calls it creates write only to temps),
 970                 //
 971                 // If someone changes that, please update this code path
 972                 // to create a temporary.
 973                 span_bug!(self.mir.span, "can't directly store to unaligned value");
 974             }
 975             llargs.push(dest.llval);
 976             ReturnDest::Nothing
 977         } else {
 978             ReturnDest::Store(dest)
 979         }
 980     }
 981
 982     fn codegen_transmute(&mut self, bx: &Builder<'a, 'll, 'tcx>,
 983                          src: &mir::Operand<'tcx>,
 984                          dst: &mir::Place<'tcx>) {
 985         if let mir::Place::Local(index) = *dst {
 986             match self.locals[index] {
 987                 LocalRef::Place(place) => self.codegen_transmute_into(bx, src, place),
 988                 LocalRef::UnsizedPlace(_) => bug!("transmute must not involve unsized locals"),
 989                 LocalRef::Operand(None) => {
 990                     let dst_layout = bx.cx.layout_of(self.monomorphized_place_ty(dst));
 991                     assert!(!dst_layout.ty.has_erasable_regions());
 992                     let place = PlaceRef::alloca(bx, dst_layout, "transmute_temp");
 993                     place.storage_live(bx);
 994                     self.codegen_transmute_into(bx, src, place);
 995                     let op = place.load(bx);
 996                     place.storage_dead(bx);
 997                     self.locals[index] = LocalRef::Operand(Some(op));
 998                 }
 999                 LocalRef::Operand(Some(op)) => {
1000                     assert!(op.layout.is_zst(),
1001                             "assigning to initialized SSAtemp");
1002                 }
1003             }
1004         } else {
1005             let dst = self.codegen_place(bx, dst);
1006             self.codegen_transmute_into(bx, src, dst);
1007         }
1008     }
1009
1010     fn codegen_transmute_into(&mut self, bx: &Builder<'a, 'll, 'tcx>,
1011                               src: &mir::Operand<'tcx>,
1012                               dst: PlaceRef<'tcx, &'ll Value>) {
1013         let src = self.codegen_operand(bx, src);
1014         let llty = src.layout.llvm_type(bx.cx);
1015         let cast_ptr = bx.pointercast(dst.llval, llty.ptr_to());
1016         let align = src.layout.align.min(dst.layout.align);
1017         src.val.store(bx, PlaceRef::new_sized(cast_ptr, src.layout, align));
1018     }
1019
1020
1021     // Stores the return value of a function call into it's final location.
1022     fn store_return(&mut self,
1023                     bx: &Builder<'a, 'll, 'tcx>,
1024                     dest: ReturnDest<'tcx, &'ll Value>,
1025                     ret_ty: &ArgType<'tcx, Ty<'tcx>>,
1026                     llval: &'ll Value) {
1027         use self::ReturnDest::*;
1028
1029         match dest {
1030             Nothing => (),
1031             Store(dst) => ret_ty.store(bx, llval, dst),
1032             IndirectOperand(tmp, index) => {
1033                 let op = tmp.load(bx);
1034                 tmp.storage_dead(bx);
1035                 self.locals[index] = LocalRef::Operand(Some(op));
1036             }
1037             DirectOperand(index) => {
1038                 // If there is a cast, we have to store and reload.
1039                 let op = if let PassMode::Cast(_) = ret_ty.mode {
1040                     let tmp = PlaceRef::alloca(bx, ret_ty.layout, "tmp_ret");
1041                     tmp.storage_live(bx);
1042                     ret_ty.store(bx, llval, tmp);
1043                     let op = tmp.load(bx);
1044                     tmp.storage_dead(bx);
1045                     op
1046                 } else {
1047                     OperandRef::from_immediate_or_packed_pair(bx, llval, ret_ty.layout)
1048                 };
1049                 self.locals[index] = LocalRef::Operand(Some(op));
1050             }
1051         }
1052     }
1053 }
1054
1055 enum ReturnDest<'tcx, V> {
1056     // Do nothing, the return value is indirect or ignored
1057     Nothing,
1058     // Store the return value to the pointer
1059     Store(PlaceRef<'tcx, V>),
1060     // Stores an indirect return value to an operand local place
1061     IndirectOperand(PlaceRef<'tcx, V>, mir::Local),
1062     // Stores a direct return value to an operand local place
1063     DirectOperand(mir::Local)
1064 }