src/librustc_codegen_llvm/mir/block.rs

   1 // Copyright 2012-2014 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 use llvm::{self, BasicBlock};
  12 use rustc::middle::lang_items;
  13 use rustc::ty::{self, Ty, TypeFoldable};
  14 use rustc::ty::layout::{self, LayoutOf};
  15 use rustc::mir;
  16 use rustc::mir::interpret::EvalErrorKind;
  17 use abi::{Abi, ArgType, ArgTypeExt, FnType, FnTypeExt, LlvmType, PassMode};
  18 use base;
  19 use callee;
  20 use builder::{Builder, MemFlags};
  21 use common::{self, C_bool, C_str_slice, C_struct, C_u32, C_uint_big, C_undef};
  22 use consts;
  23 use meth;
  24 use monomorphize;
  25 use type_of::LayoutLlvmExt;
  26 use type_::Type;
  27 use value::Value;
  28
  29 use syntax::symbol::Symbol;
  30 use syntax_pos::Pos;
  31
  32 use super::{FunctionCx, LocalRef};
  33 use super::place::PlaceRef;
  34 use super::operand::OperandRef;
  35 use super::operand::OperandValue::{Pair, Ref, Immediate};
  36
  37 impl FunctionCx<'a, 'll, 'tcx> {
  38     pub fn codegen_block(&mut self, bb: mir::BasicBlock) {
  39         let mut bx = self.build_block(bb);
  40         let data = &self.mir[bb];
  41
  42         debug!("codegen_block({:?}={:?})", bb, data);
  43
  44         for statement in &data.statements {
  45             bx = self.codegen_statement(bx, statement);
  46         }
  47
  48         self.codegen_terminator(bx, bb, data.terminator());
  49     }
  50
  51     fn codegen_terminator(&mut self,
  52                         mut bx: Builder<'a, 'll, 'tcx>,
  53                         bb: mir::BasicBlock,
  54                         terminator: &mir::Terminator<'tcx>)
  55     {
  56         debug!("codegen_terminator: {:?}", terminator);
  57
  58         // Create the cleanup bundle, if needed.
  59         let tcx = bx.tcx();
  60         let span = terminator.source_info.span;
  61         let funclet_bb = self.cleanup_kinds[bb].funclet_bb(bb);
  62         let funclet = funclet_bb.and_then(|funclet_bb| self.funclets[funclet_bb].as_ref());
  63
  64         let cleanup_pad = funclet.map(|lp| lp.cleanuppad());
  65         let cleanup_bundle = funclet.map(|l| l.bundle());
  66
  67         let lltarget = |this: &mut Self, target: mir::BasicBlock| {
  68             let lltarget = this.blocks[target];
  69             let target_funclet = this.cleanup_kinds[target].funclet_bb(target);
  70             match (funclet_bb, target_funclet) {
  71                 (None, None) => (lltarget, false),
  72                 (Some(f), Some(t_f))
  73                     if f == t_f || !base::wants_msvc_seh(tcx.sess)
  74                     => (lltarget, false),
  75                 (None, Some(_)) => {
  76                     // jump *into* cleanup - need a landing pad if GNU
  77                     (this.landing_pad_to(target), false)
  78                 }
  79                 (Some(_), None) => span_bug!(span, "{:?} - jump out of cleanup?", terminator),
  80                 (Some(_), Some(_)) => {
  81                     (this.landing_pad_to(target), true)
  82                 }
  83             }
  84         };
  85
  86         let llblock = |this: &mut Self, target: mir::BasicBlock| {
  87             let (lltarget, is_cleanupret) = lltarget(this, target);
  88             if is_cleanupret {
  89                 // MSVC cross-funclet jump - need a trampoline
  90
  91                 debug!("llblock: creating cleanup trampoline for {:?}", target);
  92                 let name = &format!("{:?}_cleanup_trampoline_{:?}", bb, target);
  93                 let trampoline = this.new_block(name);
  94                 trampoline.cleanup_ret(cleanup_pad.unwrap(), Some(lltarget));
  95                 trampoline.llbb()
  96             } else {
  97                 lltarget
  98             }
  99         };
 100
 101         let funclet_br = |this: &mut Self, bx: Builder<'_, 'll, '_>, target: mir::BasicBlock| {
 102             let (lltarget, is_cleanupret) = lltarget(this, target);
 103             if is_cleanupret {
 104                 // micro-optimization: generate a `ret` rather than a jump
 105                 // to a trampoline.
 106                 bx.cleanup_ret(cleanup_pad.unwrap(), Some(lltarget));
 107             } else {
 108                 bx.br(lltarget);
 109             }
 110         };
 111
 112         let do_call = |
 113             this: &mut Self,
 114             bx: Builder<'a, 'll, 'tcx>,
 115             fn_ty: FnType<'tcx, Ty<'tcx>>,
 116             fn_ptr: &'ll Value,
 117             llargs: &[&'ll Value],
 118             destination: Option<(ReturnDest<'ll, 'tcx>, mir::BasicBlock)>,
 119             cleanup: Option<mir::BasicBlock>
 120         | {
 121             if let Some(cleanup) = cleanup {
 122                 let ret_bx = if let Some((_, target)) = destination {
 123                     this.blocks[target]
 124                 } else {
 125                     this.unreachable_block()
 126                 };
 127                 let invokeret = bx.invoke(fn_ptr,
 128                                            &llargs,
 129                                            ret_bx,
 130                                            llblock(this, cleanup),
 131                                            cleanup_bundle);
 132                 fn_ty.apply_attrs_callsite(&bx, invokeret);
 133
 134                 if let Some((ret_dest, target)) = destination {
 135                     let ret_bx = this.build_block(target);
 136                     this.set_debug_loc(&ret_bx, terminator.source_info);
 137                     this.store_return(&ret_bx, ret_dest, &fn_ty.ret, invokeret);
 138                 }
 139             } else {
 140                 let llret = bx.call(fn_ptr, &llargs, cleanup_bundle);
 141                 fn_ty.apply_attrs_callsite(&bx, llret);
 142                 if this.mir[bb].is_cleanup {
 143                     // Cleanup is always the cold path. Don't inline
 144                     // drop glue. Also, when there is a deeply-nested
 145                     // struct, there are "symmetry" issues that cause
 146                     // exponential inlining - see issue #41696.
 147                     llvm::Attribute::NoInline.apply_callsite(llvm::AttributePlace::Function, llret);
 148                 }
 149
 150                 if let Some((ret_dest, target)) = destination {
 151                     this.store_return(&bx, ret_dest, &fn_ty.ret, llret);
 152                     funclet_br(this, bx, target);
 153                 } else {
 154                     bx.unreachable();
 155                 }
 156             }
 157         };
 158
 159         self.set_debug_loc(&bx, terminator.source_info);
 160         match terminator.kind {
 161             mir::TerminatorKind::Resume => {
 162                 if let Some(cleanup_pad) = cleanup_pad {
 163                     bx.cleanup_ret(cleanup_pad, None);
 164                 } else {
 165                     let slot = self.get_personality_slot(&bx);
 166                     let lp0 = slot.project_field(&bx, 0).load(&bx).immediate();
 167                     let lp1 = slot.project_field(&bx, 1).load(&bx).immediate();
 168                     slot.storage_dead(&bx);
 169
 170                     if !bx.sess().target.target.options.custom_unwind_resume {
 171                         let mut lp = C_undef(self.landing_pad_type());
 172                         lp = bx.insert_value(lp, lp0, 0);
 173                         lp = bx.insert_value(lp, lp1, 1);
 174                         bx.resume(lp);
 175                     } else {
 176                         bx.call(bx.cx.eh_unwind_resume(), &[lp0], cleanup_bundle);
 177                         bx.unreachable();
 178                     }
 179                 }
 180             }
 181
 182             mir::TerminatorKind::Abort => {
 183                 // Call core::intrinsics::abort()
 184                 let fnname = bx.cx.get_intrinsic(&("llvm.trap"));
 185                 bx.call(fnname, &[], None);
 186                 bx.unreachable();
 187             }
 188
 189             mir::TerminatorKind::Goto { target } => {
 190                 funclet_br(self, bx, target);
 191             }
 192
 193             mir::TerminatorKind::SwitchInt { ref discr, switch_ty, ref values, ref targets } => {
 194                 let discr = self.codegen_operand(&bx, discr);
 195                 if targets.len() == 2 {
 196                     // If there are two targets, emit br instead of switch
 197                     let lltrue = llblock(self, targets[0]);
 198                     let llfalse = llblock(self, targets[1]);
 199                     if switch_ty == bx.tcx().types.bool {
 200                         // Don't generate trivial icmps when switching on bool
 201                         if let [0] = values[..] {
 202                             bx.cond_br(discr.immediate(), llfalse, lltrue);
 203                         } else {
 204                             assert_eq!(&values[..], &[1]);
 205                             bx.cond_br(discr.immediate(), lltrue, llfalse);
 206                         }
 207                     } else {
 208                         let switch_llty = bx.cx.layout_of(switch_ty).immediate_llvm_type(bx.cx);
 209                         let llval = C_uint_big(switch_llty, values[0]);
 210                         let cmp = bx.icmp(llvm::IntEQ, discr.immediate(), llval);
 211                         bx.cond_br(cmp, lltrue, llfalse);
 212                     }
 213                 } else {
 214                     let (otherwise, targets) = targets.split_last().unwrap();
 215                     let switch = bx.switch(discr.immediate(),
 216                                             llblock(self, *otherwise), values.len());
 217                     let switch_llty = bx.cx.layout_of(switch_ty).immediate_llvm_type(bx.cx);
 218                     for (&value, target) in values.iter().zip(targets) {
 219                         let llval = C_uint_big(switch_llty, value);
 220                         let llbb = llblock(self, *target);
 221                         bx.add_case(switch, llval, llbb)
 222                     }
 223                 }
 224             }
 225
 226             mir::TerminatorKind::Return => {
 227                 let llval = match self.fn_ty.ret.mode {
 228                     PassMode::Ignore | PassMode::Indirect(..) => {
 229                         bx.ret_void();
 230                         return;
 231                     }
 232
 233                     PassMode::Direct(_) | PassMode::Pair(..) => {
 234                         let op = self.codegen_consume(&bx, &mir::Place::Local(mir::RETURN_PLACE));
 235                         if let Ref(llval, _, align) = op.val {
 236                             bx.load(llval, align)
 237                         } else {
 238                             op.immediate_or_packed_pair(&bx)
 239                         }
 240                     }
 241
 242                     PassMode::Cast(cast_ty) => {
 243                         let op = match self.locals[mir::RETURN_PLACE] {
 244                             LocalRef::Operand(Some(op)) => op,
 245                             LocalRef::Operand(None) => bug!("use of return before def"),
 246                             LocalRef::Place(cg_place) => {
 247                                 OperandRef {
 248                                     val: Ref(cg_place.llval, None, cg_place.align),
 249                                     layout: cg_place.layout
 250                                 }
 251                             }
 252                             LocalRef::UnsizedPlace(_) => bug!("return type must be sized"),
 253                         };
 254                         let llslot = match op.val {
 255                             Immediate(_) | Pair(..) => {
 256                                 let scratch = PlaceRef::alloca(&bx, self.fn_ty.ret.layout, "ret");
 257                                 op.val.store(&bx, scratch);
 258                                 scratch.llval
 259                             }
 260                             Ref(llval, _, align) => {
 261                                 assert_eq!(align.abi(), op.layout.align.abi(),
 262                                            "return place is unaligned!");
 263                                 llval
 264                             }
 265                         };
 266                         bx.load(
 267                             bx.pointercast(llslot, cast_ty.llvm_type(bx.cx).ptr_to()),
 268                             self.fn_ty.ret.layout.align)
 269                     }
 270                 };
 271                 bx.ret(llval);
 272             }
 273
 274             mir::TerminatorKind::Unreachable => {
 275                 bx.unreachable();
 276             }
 277
 278             mir::TerminatorKind::Drop { ref location, target, unwind } => {
 279                 let ty = location.ty(self.mir, bx.tcx()).to_ty(bx.tcx());
 280                 let ty = self.monomorphize(&ty);
 281                 let drop_fn = monomorphize::resolve_drop_in_place(bx.cx.tcx, ty);
 282
 283                 if let ty::InstanceDef::DropGlue(_, None) = drop_fn.def {
 284                     // we don't actually need to drop anything.
 285                     funclet_br(self, bx, target);
 286                     return
 287                 }
 288
 289                 let place = self.codegen_place(&bx, location);
 290                 let (args1, args2);
 291                 let mut args = if let Some(llextra) = place.llextra {
 292                     args2 = [place.llval, llextra];
 293                     &args2[..]
 294                 } else {
 295                     args1 = [place.llval];
 296                     &args1[..]
 297                 };
 298                 let (drop_fn, fn_ty) = match ty.sty {
 299                     ty::Dynamic(..) => {
 300                         let fn_ty = drop_fn.ty(bx.cx.tcx);
 301                         let sig = common::ty_fn_sig(bx.cx, fn_ty);
 302                         let sig = bx.tcx().normalize_erasing_late_bound_regions(
 303                             ty::ParamEnv::reveal_all(),
 304                             &sig,
 305                         );
 306                         let fn_ty = FnType::new_vtable(bx.cx, sig, &[]);
 307                         let vtable = args[1];
 308                         args = &args[..1];
 309                         (meth::DESTRUCTOR.get_fn(&bx, vtable, &fn_ty), fn_ty)
 310                     }
 311                     _ => {
 312                         (callee::get_fn(bx.cx, drop_fn),
 313                          FnType::of_instance(bx.cx, &drop_fn))
 314                     }
 315                 };
 316                 do_call(self, bx, fn_ty, drop_fn, args,
 317                         Some((ReturnDest::Nothing, target)),
 318                         unwind);
 319             }
 320
 321             mir::TerminatorKind::Assert { ref cond, expected, ref msg, target, cleanup } => {
 322                 let cond = self.codegen_operand(&bx, cond).immediate();
 323                 let mut const_cond = common::const_to_opt_u128(cond, false).map(|c| c == 1);
 324
 325                 // This case can currently arise only from functions marked
 326                 // with #[rustc_inherit_overflow_checks] and inlined from
 327                 // another crate (mostly core::num generic/#[inline] fns),
 328                 // while the current crate doesn't use overflow checks.
 329                 // NOTE: Unlike binops, negation doesn't have its own
 330                 // checked operation, just a comparison with the minimum
 331                 // value, so we have to check for the assert message.
 332                 if !bx.cx.check_overflow {
 333                     if let mir::interpret::EvalErrorKind::OverflowNeg = *msg {
 334                         const_cond = Some(expected);
 335                     }
 336                 }
 337
 338                 // Don't codegen the panic block if success if known.
 339                 if const_cond == Some(expected) {
 340                     funclet_br(self, bx, target);
 341                     return;
 342                 }
 343
 344                 // Pass the condition through llvm.expect for branch hinting.
 345                 let expect = bx.cx.get_intrinsic(&"llvm.expect.i1");
 346                 let cond = bx.call(expect, &[cond, C_bool(bx.cx, expected)], None);
 347
 348                 // Create the failure block and the conditional branch to it.
 349                 let lltarget = llblock(self, target);
 350                 let panic_block = self.new_block("panic");
 351                 if expected {
 352                     bx.cond_br(cond, lltarget, panic_block.llbb());
 353                 } else {
 354                     bx.cond_br(cond, panic_block.llbb(), lltarget);
 355                 }
 356
 357                 // After this point, bx is the block for the call to panic.
 358                 bx = panic_block;
 359                 self.set_debug_loc(&bx, terminator.source_info);
 360
 361                 // Get the location information.
 362                 let loc = bx.sess().source_map().lookup_char_pos(span.lo());
 363                 let filename = Symbol::intern(&loc.file.name.to_string()).as_str();
 364                 let filename = C_str_slice(bx.cx, filename);
 365                 let line = C_u32(bx.cx, loc.line as u32);
 366                 let col = C_u32(bx.cx, loc.col.to_usize() as u32 + 1);
 367                 let align = tcx.data_layout.aggregate_align
 368                     .max(tcx.data_layout.i32_align)
 369                     .max(tcx.data_layout.pointer_align);
 370
 371                 // Put together the arguments to the panic entry point.
 372                 let (lang_item, args) = match *msg {
 373                     EvalErrorKind::BoundsCheck { ref len, ref index } => {
 374                         let len = self.codegen_operand(&mut bx, len).immediate();
 375                         let index = self.codegen_operand(&mut bx, index).immediate();
 376
 377                         let file_line_col = C_struct(bx.cx, &[filename, line, col], false);
 378                         let file_line_col = consts::addr_of(bx.cx,
 379                                                             file_line_col,
 380                                                             align,
 381                                                             Some("panic_bounds_check_loc"));
 382                         (lang_items::PanicBoundsCheckFnLangItem,
 383                          vec![file_line_col, index, len])
 384                     }
 385                     _ => {
 386                         let str = msg.description();
 387                         let msg_str = Symbol::intern(str).as_str();
 388                         let msg_str = C_str_slice(bx.cx, msg_str);
 389                         let msg_file_line_col = C_struct(bx.cx,
 390                                                      &[msg_str, filename, line, col],
 391                                                      false);
 392                         let msg_file_line_col = consts::addr_of(bx.cx,
 393                                                                 msg_file_line_col,
 394                                                                 align,
 395                                                                 Some("panic_loc"));
 396                         (lang_items::PanicFnLangItem,
 397                          vec![msg_file_line_col])
 398                     }
 399                 };
 400
 401                 // Obtain the panic entry point.
 402                 let def_id = common::langcall(bx.tcx(), Some(span), "", lang_item);
 403                 let instance = ty::Instance::mono(bx.tcx(), def_id);
 404                 let fn_ty = FnType::of_instance(bx.cx, &instance);
 405                 let llfn = callee::get_fn(bx.cx, instance);
 406
 407                 // Codegen the actual panic invoke/call.
 408                 do_call(self, bx, fn_ty, llfn, &args, None, cleanup);
 409             }
 410
 411             mir::TerminatorKind::DropAndReplace { .. } => {
 412                 bug!("undesugared DropAndReplace in codegen: {:?}", terminator);
 413             }
 414
 415             mir::TerminatorKind::Call { ref func, ref args, ref destination, cleanup } => {
 416                 // Create the callee. This is a fn ptr or zero-sized and hence a kind of scalar.
 417                 let callee = self.codegen_operand(&bx, func);
 418
 419                 let (instance, mut llfn) = match callee.layout.ty.sty {
 420                     ty::FnDef(def_id, substs) => {
 421                         (Some(ty::Instance::resolve(bx.cx.tcx,
 422                                                     ty::ParamEnv::reveal_all(),
 423                                                     def_id,
 424                                                     substs).unwrap()),
 425                          None)
 426                     }
 427                     ty::FnPtr(_) => {
 428                         (None, Some(callee.immediate()))
 429                     }
 430                     _ => bug!("{} is not callable", callee.layout.ty)
 431                 };
 432                 let def = instance.map(|i| i.def);
 433                 let sig = callee.layout.ty.fn_sig(bx.tcx());
 434                 let sig = bx.tcx().normalize_erasing_late_bound_regions(
 435                     ty::ParamEnv::reveal_all(),
 436                     &sig,
 437                 );
 438                 let abi = sig.abi;
 439
 440                 // Handle intrinsics old codegen wants Expr's for, ourselves.
 441                 let intrinsic = match def {
 442                     Some(ty::InstanceDef::Intrinsic(def_id))
 443                         => Some(bx.tcx().item_name(def_id).as_str()),
 444                     _ => None
 445                 };
 446                 let intrinsic = intrinsic.as_ref().map(|s| &s[..]);
 447
 448                 if intrinsic == Some("transmute") {
 449                     if let Some(destination_ref) = destination.as_ref() {
 450                         let &(ref dest, target) = destination_ref;
 451                         self.codegen_transmute(&bx, &args[0], dest);
 452                         funclet_br(self, bx, target);
 453                     } else {
 454                         // If we are trying to transmute to an uninhabited type,
 455                         // it is likely there is no allotted destination. In fact,
 456                         // transmuting to an uninhabited type is UB, which means
 457                         // we can do what we like. Here, we declare that transmuting
 458                         // into an uninhabited type is impossible, so anything following
 459                         // it must be unreachable.
 460                         assert_eq!(bx.cx.layout_of(sig.output()).abi, layout::Abi::Uninhabited);
 461                         bx.unreachable();
 462                     }
 463                     return;
 464                 }
 465
 466                 if (intrinsic == Some("init") || intrinsic == Some("uninit")) &&
 467                     bx.cx.layout_of(sig.output()).abi.is_uninhabited()
 468                 {
 469                     let loc = bx.sess().codemap().lookup_char_pos(span.lo());
 470                     let filename = Symbol::intern(&loc.file.name.to_string()).as_str();
 471                     let filename = C_str_slice(bx.cx, filename);
 472                     let line = C_u32(bx.cx, loc.line as u32);
 473                     let col = C_u32(bx.cx, loc.col.to_usize() as u32 + 1);
 474                     let align = tcx.data_layout.aggregate_align
 475                         .max(tcx.data_layout.i32_align)
 476                         .max(tcx.data_layout.pointer_align);
 477
 478                     let str = if intrinsic == Some("init") {
 479                         "Attempted to instantiate an uninhabited type (e.g. `!`) \
 480                          using mem::zeroed()"
 481                     } else {
 482                         "Attempted to instantiate an uninhabited type (e.g. `!`) \
 483                          using mem::uninitialized()"
 484                     };
 485                     let msg_str = Symbol::intern(str).as_str();
 486                     let msg_str = C_str_slice(bx.cx, msg_str);
 487                     let msg_file_line_col = C_struct(bx.cx,
 488                                                     &[msg_str, filename, line, col],
 489                                                     false);
 490                     let msg_file_line_col = consts::addr_of(bx.cx,
 491                                                             msg_file_line_col,
 492                                                             align,
 493                                                             Some("panic_loc"));
 494
 495                     // Obtain the panic entry point.
 496                     let def_id =
 497                         common::langcall(bx.tcx(), Some(span), "", lang_items::PanicFnLangItem);
 498                     let instance = ty::Instance::mono(bx.tcx(), def_id);
 499                     let fn_ty = FnType::of_instance(bx.cx, &instance);
 500                     let llfn = callee::get_fn(bx.cx, instance);
 501
 502                     // Codegen the actual panic invoke/call.
 503                     do_call(
 504                         self,
 505                         bx,
 506                         fn_ty,
 507                         llfn,
 508                         &[msg_file_line_col],
 509                         destination.as_ref().map(|(_, bb)| (ReturnDest::Nothing, *bb)),
 510                         cleanup,
 511                     );
 512                     return;
 513                 }
 514
 515                 let extra_args = &args[sig.inputs().len()..];
 516                 let extra_args = extra_args.iter().map(|op_arg| {
 517                     let op_ty = op_arg.ty(self.mir, bx.tcx());
 518                     self.monomorphize(&op_ty)
 519                 }).collect::<Vec<_>>();
 520
 521                 let fn_ty = match def {
 522                     Some(ty::InstanceDef::Virtual(..)) => {
 523                         FnType::new_vtable(bx.cx, sig, &extra_args)
 524                     }
 525                     Some(ty::InstanceDef::DropGlue(_, None)) => {
 526                         // empty drop glue - a nop.
 527                         let &(_, target) = destination.as_ref().unwrap();
 528                         funclet_br(self, bx, target);
 529                         return;
 530                     }
 531                     _ => FnType::new(bx.cx, sig, &extra_args)
 532                 };
 533
 534                 // The arguments we'll be passing. Plus one to account for outptr, if used.
 535                 let arg_count = fn_ty.args.len() + fn_ty.ret.is_indirect() as usize;
 536                 let mut llargs = Vec::with_capacity(arg_count);
 537
 538                 // Prepare the return value destination
 539                 let ret_dest = if let Some((ref dest, _)) = *destination {
 540                     let is_intrinsic = intrinsic.is_some();
 541                     self.make_return_dest(&bx, dest, &fn_ty.ret, &mut llargs,
 542                                           is_intrinsic)
 543                 } else {
 544                     ReturnDest::Nothing
 545                 };
 546
 547                 if intrinsic.is_some() && intrinsic != Some("drop_in_place") {
 548                     use intrinsic::codegen_intrinsic_call;
 549
 550                     let dest = match ret_dest {
 551                         _ if fn_ty.ret.is_indirect() => llargs[0],
 552                         ReturnDest::Nothing => {
 553                             C_undef(fn_ty.ret.memory_ty(bx.cx).ptr_to())
 554                         }
 555                         ReturnDest::IndirectOperand(dst, _) |
 556                         ReturnDest::Store(dst) => dst.llval,
 557                         ReturnDest::DirectOperand(_) =>
 558                             bug!("Cannot use direct operand with an intrinsic call")
 559                     };
 560
 561                     let args: Vec<_> = args.iter().enumerate().map(|(i, arg)| {
 562                         // The indices passed to simd_shuffle* in the
 563                         // third argument must be constant. This is
 564                         // checked by const-qualification, which also
 565                         // promotes any complex rvalues to constants.
 566                         if i == 2 && intrinsic.unwrap().starts_with("simd_shuffle") {
 567                             match *arg {
 568                                 // The shuffle array argument is usually not an explicit constant,
 569                                 // but specified directly in the code. This means it gets promoted
 570                                 // and we can then extract the value by evaluating the promoted.
 571                                 mir::Operand::Copy(mir::Place::Promoted(box(index, ty))) |
 572                                 mir::Operand::Move(mir::Place::Promoted(box(index, ty))) => {
 573                                     let param_env = ty::ParamEnv::reveal_all();
 574                                     let cid = mir::interpret::GlobalId {
 575                                         instance: self.instance,
 576                                         promoted: Some(index),
 577                                     };
 578                                     let c = bx.tcx().const_eval(param_env.and(cid));
 579                                     let (llval, ty) = self.simd_shuffle_indices(
 580                                         &bx,
 581                                         terminator.source_info.span,
 582                                         ty,
 583                                         c,
 584                                     );
 585                                     return OperandRef {
 586                                         val: Immediate(llval),
 587                                         layout: bx.cx.layout_of(ty),
 588                                     };
 589
 590                                 },
 591                                 mir::Operand::Copy(_) |
 592                                 mir::Operand::Move(_) => {
 593                                     span_bug!(span, "shuffle indices must be constant");
 594                                 }
 595                                 mir::Operand::Constant(ref constant) => {
 596                                     let c = self.eval_mir_constant(&bx, constant);
 597                                     let (llval, ty) = self.simd_shuffle_indices(
 598                                         &bx,
 599                                         constant.span,
 600                                         constant.ty,
 601                                         c,
 602                                     );
 603                                     return OperandRef {
 604                                         val: Immediate(llval),
 605                                         layout: bx.cx.layout_of(ty)
 606                                     };
 607                                 }
 608                             }
 609                         }
 610
 611                         self.codegen_operand(&bx, arg)
 612                     }).collect();
 613
 614
 615                     let callee_ty = instance.as_ref().unwrap().ty(bx.cx.tcx);
 616                     codegen_intrinsic_call(&bx, callee_ty, &fn_ty, &args, dest,
 617                                          terminator.source_info.span);
 618
 619                     if let ReturnDest::IndirectOperand(dst, _) = ret_dest {
 620                         self.store_return(&bx, ret_dest, &fn_ty.ret, dst.llval);
 621                     }
 622
 623                     if let Some((_, target)) = *destination {
 624                         funclet_br(self, bx, target);
 625                     } else {
 626                         bx.unreachable();
 627                     }
 628
 629                     return;
 630                 }
 631
 632                 // Split the rust-call tupled arguments off.
 633                 let (first_args, untuple) = if abi == Abi::RustCall && !args.is_empty() {
 634                     let (tup, args) = args.split_last().unwrap();
 635                     (args, Some(tup))
 636                 } else {
 637                     (&args[..], None)
 638                 };
 639
 640                 for (i, arg) in first_args.iter().enumerate() {
 641                     let mut op = self.codegen_operand(&bx, arg);
 642                     if let (0, Some(ty::InstanceDef::Virtual(_, idx))) = (i, def) {
 643                         if let Pair(data_ptr, meta) = op.val {
 644                             llfn = Some(meth::VirtualIndex::from_index(idx)
 645                                 .get_fn(&bx, meta, &fn_ty));
 646                             llargs.push(data_ptr);
 647                             continue;
 648                         }
 649                     }
 650
 651                     // The callee needs to own the argument memory if we pass it
 652                     // by-ref, so make a local copy of non-immediate constants.
 653                     match (arg, op.val) {
 654                         (&mir::Operand::Copy(_), Ref(_, None, _)) |
 655                         (&mir::Operand::Constant(_), Ref(_, None, _)) => {
 656                             let tmp = PlaceRef::alloca(&bx, op.layout, "const");
 657                             op.val.store(&bx, tmp);
 658                             op.val = Ref(tmp.llval, None, tmp.align);
 659                         }
 660                         _ => {}
 661                     }
 662
 663                     self.codegen_argument(&bx, op, &mut llargs, &fn_ty.args[i]);
 664                 }
 665                 if let Some(tup) = untuple {
 666                     self.codegen_arguments_untupled(&bx, tup, &mut llargs,
 667                         &fn_ty.args[first_args.len()..])
 668                 }
 669
 670                 let fn_ptr = match (llfn, instance) {
 671                     (Some(llfn), _) => llfn,
 672                     (None, Some(instance)) => callee::get_fn(bx.cx, instance),
 673                     _ => span_bug!(span, "no llfn for call"),
 674                 };
 675
 676                 do_call(self, bx, fn_ty, fn_ptr, &llargs,
 677                         destination.as_ref().map(|&(_, target)| (ret_dest, target)),
 678                         cleanup);
 679             }
 680             mir::TerminatorKind::GeneratorDrop |
 681             mir::TerminatorKind::Yield { .. } => bug!("generator ops in codegen"),
 682             mir::TerminatorKind::FalseEdges { .. } |
 683             mir::TerminatorKind::FalseUnwind { .. } => bug!("borrowck false edges in codegen"),
 684         }
 685     }
 686
 687     fn codegen_argument(&mut self,
 688                       bx: &Builder<'a, 'll, 'tcx>,
 689                       op: OperandRef<'ll, 'tcx>,
 690                       llargs: &mut Vec<&'ll Value>,
 691                       arg: &ArgType<'tcx, Ty<'tcx>>) {
 692         // Fill padding with undef value, where applicable.
 693         if let Some(ty) = arg.pad {
 694             llargs.push(C_undef(ty.llvm_type(bx.cx)));
 695         }
 696
 697         if arg.is_ignore() {
 698             return;
 699         }
 700
 701         if let PassMode::Pair(..) = arg.mode {
 702             match op.val {
 703                 Pair(a, b) => {
 704                     llargs.push(a);
 705                     llargs.push(b);
 706                     return;
 707                 }
 708                 _ => bug!("codegen_argument: {:?} invalid for pair argument", op)
 709             }
 710         } else if arg.is_unsized_indirect() {
 711             match op.val {
 712                 Ref(a, Some(b), _) => {
 713                     llargs.push(a);
 714                     llargs.push(b);
 715                     return;
 716                 }
 717                 _ => bug!("codegen_argument: {:?} invalid for unsized indirect argument", op)
 718             }
 719         }
 720
 721         // Force by-ref if we have to load through a cast pointer.
 722         let (mut llval, align, by_ref) = match op.val {
 723             Immediate(_) | Pair(..) => {
 724                 match arg.mode {
 725                     PassMode::Indirect(..) | PassMode::Cast(_) => {
 726                         let scratch = PlaceRef::alloca(bx, arg.layout, "arg");
 727                         op.val.store(bx, scratch);
 728                         (scratch.llval, scratch.align, true)
 729                     }
 730                     _ => {
 731                         (op.immediate_or_packed_pair(bx), arg.layout.align, false)
 732                     }
 733                 }
 734             }
 735             Ref(llval, _, align) => {
 736                 if arg.is_indirect() && align.abi() < arg.layout.align.abi() {
 737                     // `foo(packed.large_field)`. We can't pass the (unaligned) field directly. I
 738                     // think that ATM (Rust 1.16) we only pass temporaries, but we shouldn't
 739                     // have scary latent bugs around.
 740
 741                     let scratch = PlaceRef::alloca(bx, arg.layout, "arg");
 742                     base::memcpy_ty(bx, scratch.llval, llval, op.layout, align, MemFlags::empty());
 743                     (scratch.llval, scratch.align, true)
 744                 } else {
 745                     (llval, align, true)
 746                 }
 747             }
 748         };
 749
 750         if by_ref && !arg.is_indirect() {
 751             // Have to load the argument, maybe while casting it.
 752             if let PassMode::Cast(ty) = arg.mode {
 753                 llval = bx.load(bx.pointercast(llval, ty.llvm_type(bx.cx).ptr_to()),
 754                                  align.min(arg.layout.align));
 755             } else {
 756                 // We can't use `PlaceRef::load` here because the argument
 757                 // may have a type we don't treat as immediate, but the ABI
 758                 // used for this call is passing it by-value. In that case,
 759                 // the load would just produce `OperandValue::Ref` instead
 760                 // of the `OperandValue::Immediate` we need for the call.
 761                 llval = bx.load(llval, align);
 762                 if let layout::Abi::Scalar(ref scalar) = arg.layout.abi {
 763                     if scalar.is_bool() {
 764                         bx.range_metadata(llval, 0..2);
 765                     }
 766                 }
 767                 // We store bools as i8 so we need to truncate to i1.
 768                 llval = base::to_immediate(bx, llval, arg.layout);
 769             }
 770         }
 771
 772         llargs.push(llval);
 773     }
 774
 775     fn codegen_arguments_untupled(&mut self,
 776                                 bx: &Builder<'a, 'll, 'tcx>,
 777                                 operand: &mir::Operand<'tcx>,
 778                                 llargs: &mut Vec<&'ll Value>,
 779                                 args: &[ArgType<'tcx, Ty<'tcx>>]) {
 780         let tuple = self.codegen_operand(bx, operand);
 781
 782         // Handle both by-ref and immediate tuples.
 783         if let Ref(llval, None, align) = tuple.val {
 784             let tuple_ptr = PlaceRef::new_sized(llval, tuple.layout, align);
 785             for i in 0..tuple.layout.fields.count() {
 786                 let field_ptr = tuple_ptr.project_field(bx, i);
 787                 self.codegen_argument(bx, field_ptr.load(bx), llargs, &args[i]);
 788             }
 789         } else if let Ref(_, Some(_), _) = tuple.val {
 790             bug!("closure arguments must be sized")
 791         } else {
 792             // If the tuple is immediate, the elements are as well.
 793             for i in 0..tuple.layout.fields.count() {
 794                 let op = tuple.extract_field(bx, i);
 795                 self.codegen_argument(bx, op, llargs, &args[i]);
 796             }
 797         }
 798     }
 799
 800     fn get_personality_slot(&mut self, bx: &Builder<'a, 'll, 'tcx>) -> PlaceRef<'ll, 'tcx> {
 801         let cx = bx.cx;
 802         if let Some(slot) = self.personality_slot {
 803             slot
 804         } else {
 805             let layout = cx.layout_of(cx.tcx.intern_tup(&[
 806                 cx.tcx.mk_mut_ptr(cx.tcx.types.u8),
 807                 cx.tcx.types.i32
 808             ]));
 809             let slot = PlaceRef::alloca(bx, layout, "personalityslot");
 810             self.personality_slot = Some(slot);
 811             slot
 812         }
 813     }
 814
 815     /// Return the landingpad wrapper around the given basic block
 816     ///
 817     /// No-op in MSVC SEH scheme.
 818     fn landing_pad_to(&mut self, target_bb: mir::BasicBlock) -> &'ll BasicBlock {
 819         if let Some(block) = self.landing_pads[target_bb] {
 820             return block;
 821         }
 822
 823         let block = self.blocks[target_bb];
 824         let landing_pad = self.landing_pad_uncached(block);
 825         self.landing_pads[target_bb] = Some(landing_pad);
 826         landing_pad
 827     }
 828
 829     fn landing_pad_uncached(&mut self, target_bb: &'ll BasicBlock) -> &'ll BasicBlock {
 830         if base::wants_msvc_seh(self.cx.sess()) {
 831             span_bug!(self.mir.span, "landing pad was not inserted?")
 832         }
 833
 834         let bx = self.new_block("cleanup");
 835
 836         let llpersonality = self.cx.eh_personality();
 837         let llretty = self.landing_pad_type();
 838         let lp = bx.landing_pad(llretty, llpersonality, 1);
 839         bx.set_cleanup(lp);
 840
 841         let slot = self.get_personality_slot(&bx);
 842         slot.storage_live(&bx);
 843         Pair(bx.extract_value(lp, 0), bx.extract_value(lp, 1)).store(&bx, slot);
 844
 845         bx.br(target_bb);
 846         bx.llbb()
 847     }
 848
 849     fn landing_pad_type(&self) -> &'ll Type {
 850         let cx = self.cx;
 851         Type::struct_(cx, &[Type::i8p(cx), Type::i32(cx)], false)
 852     }
 853
 854     fn unreachable_block(&mut self) -> &'ll BasicBlock {
 855         self.unreachable_block.unwrap_or_else(|| {
 856             let bl = self.new_block("unreachable");
 857             bl.unreachable();
 858             self.unreachable_block = Some(bl.llbb());
 859             bl.llbb()
 860         })
 861     }
 862
 863     pub fn new_block(&self, name: &str) -> Builder<'a, 'll, 'tcx> {
 864         Builder::new_block(self.cx, self.llfn, name)
 865     }
 866
 867     pub fn build_block(&self, bb: mir::BasicBlock) -> Builder<'a, 'll, 'tcx> {
 868         let bx = Builder::with_cx(self.cx);
 869         bx.position_at_end(self.blocks[bb]);
 870         bx
 871     }
 872
 873     fn make_return_dest(&mut self, bx: &Builder<'a, 'll, 'tcx>,
 874                         dest: &mir::Place<'tcx>, fn_ret: &ArgType<'tcx, Ty<'tcx>>,
 875                         llargs: &mut Vec<&'ll Value>, is_intrinsic: bool)
 876                         -> ReturnDest<'ll, 'tcx> {
 877         // If the return is ignored, we can just return a do-nothing ReturnDest
 878         if fn_ret.is_ignore() {
 879             return ReturnDest::Nothing;
 880         }
 881         let dest = if let mir::Place::Local(index) = *dest {
 882             match self.locals[index] {
 883                 LocalRef::Place(dest) => dest,
 884                 LocalRef::UnsizedPlace(_) => bug!("return type must be sized"),
 885                 LocalRef::Operand(None) => {
 886                     // Handle temporary places, specifically Operand ones, as
 887                     // they don't have allocas
 888                     return if fn_ret.is_indirect() {
 889                         // Odd, but possible, case, we have an operand temporary,
 890                         // but the calling convention has an indirect return.
 891                         let tmp = PlaceRef::alloca(bx, fn_ret.layout, "tmp_ret");
 892                         tmp.storage_live(bx);
 893                         llargs.push(tmp.llval);
 894                         ReturnDest::IndirectOperand(tmp, index)
 895                     } else if is_intrinsic {
 896                         // Currently, intrinsics always need a location to store
 897                         // the result. so we create a temporary alloca for the
 898                         // result
 899                         let tmp = PlaceRef::alloca(bx, fn_ret.layout, "tmp_ret");
 900                         tmp.storage_live(bx);
 901                         ReturnDest::IndirectOperand(tmp, index)
 902                     } else {
 903                         ReturnDest::DirectOperand(index)
 904                     };
 905                 }
 906                 LocalRef::Operand(Some(_)) => {
 907                     bug!("place local already assigned to");
 908                 }
 909             }
 910         } else {
 911             self.codegen_place(bx, dest)
 912         };
 913         if fn_ret.is_indirect() {
 914             if dest.align.abi() < dest.layout.align.abi() {
 915                 // Currently, MIR code generation does not create calls
 916                 // that store directly to fields of packed structs (in
 917                 // fact, the calls it creates write only to temps),
 918                 //
 919                 // If someone changes that, please update this code path
 920                 // to create a temporary.
 921                 span_bug!(self.mir.span, "can't directly store to unaligned value");
 922             }
 923             llargs.push(dest.llval);
 924             ReturnDest::Nothing
 925         } else {
 926             ReturnDest::Store(dest)
 927         }
 928     }
 929
 930     fn codegen_transmute(&mut self, bx: &Builder<'a, 'll, 'tcx>,
 931                        src: &mir::Operand<'tcx>,
 932                        dst: &mir::Place<'tcx>) {
 933         if let mir::Place::Local(index) = *dst {
 934             match self.locals[index] {
 935                 LocalRef::Place(place) => self.codegen_transmute_into(bx, src, place),
 936                 LocalRef::UnsizedPlace(_) => bug!("transmute must not involve unsized locals"),
 937                 LocalRef::Operand(None) => {
 938                     let dst_layout = bx.cx.layout_of(self.monomorphized_place_ty(dst));
 939                     assert!(!dst_layout.ty.has_erasable_regions());
 940                     let place = PlaceRef::alloca(bx, dst_layout, "transmute_temp");
 941                     place.storage_live(bx);
 942                     self.codegen_transmute_into(bx, src, place);
 943                     let op = place.load(bx);
 944                     place.storage_dead(bx);
 945                     self.locals[index] = LocalRef::Operand(Some(op));
 946                 }
 947                 LocalRef::Operand(Some(op)) => {
 948                     assert!(op.layout.is_zst(),
 949                             "assigning to initialized SSAtemp");
 950                 }
 951             }
 952         } else {
 953             let dst = self.codegen_place(bx, dst);
 954             self.codegen_transmute_into(bx, src, dst);
 955         }
 956     }
 957
 958     fn codegen_transmute_into(&mut self, bx: &Builder<'a, 'll, 'tcx>,
 959                             src: &mir::Operand<'tcx>,
 960                             dst: PlaceRef<'ll, 'tcx>) {
 961         let src = self.codegen_operand(bx, src);
 962         let llty = src.layout.llvm_type(bx.cx);
 963         let cast_ptr = bx.pointercast(dst.llval, llty.ptr_to());
 964         let align = src.layout.align.min(dst.layout.align);
 965         src.val.store(bx, PlaceRef::new_sized(cast_ptr, src.layout, align));
 966     }
 967
 968
 969     // Stores the return value of a function call into it's final location.
 970     fn store_return(&mut self,
 971                     bx: &Builder<'a, 'll, 'tcx>,
 972                     dest: ReturnDest<'ll, 'tcx>,
 973                     ret_ty: &ArgType<'tcx, Ty<'tcx>>,
 974                     llval: &'ll Value) {
 975         use self::ReturnDest::*;
 976
 977         match dest {
 978             Nothing => (),
 979             Store(dst) => ret_ty.store(bx, llval, dst),
 980             IndirectOperand(tmp, index) => {
 981                 let op = tmp.load(bx);
 982                 tmp.storage_dead(bx);
 983                 self.locals[index] = LocalRef::Operand(Some(op));
 984             }
 985             DirectOperand(index) => {
 986                 // If there is a cast, we have to store and reload.
 987                 let op = if let PassMode::Cast(_) = ret_ty.mode {
 988                     let tmp = PlaceRef::alloca(bx, ret_ty.layout, "tmp_ret");
 989                     tmp.storage_live(bx);
 990                     ret_ty.store(bx, llval, tmp);
 991                     let op = tmp.load(bx);
 992                     tmp.storage_dead(bx);
 993                     op
 994                 } else {
 995                     OperandRef::from_immediate_or_packed_pair(bx, llval, ret_ty.layout)
 996                 };
 997                 self.locals[index] = LocalRef::Operand(Some(op));
 998             }
 999         }
1000     }
1001 }
1002
1003 enum ReturnDest<'ll, 'tcx> {
1004     // Do nothing, the return value is indirect or ignored
1005     Nothing,
1006     // Store the return value to the pointer
1007     Store(PlaceRef<'ll, 'tcx>),
1008     // Stores an indirect return value to an operand local place
1009     IndirectOperand(PlaceRef<'ll, 'tcx>, mir::Local),
1010     // Stores a direct return value to an operand local place
1011     DirectOperand(mir::Local)
1012 }