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, UnsizedRef, 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 if let UnsizedRef(..) = op.val {
 238                             bug!("return type must be sized");
 239                         } else {
 240                             op.immediate_or_packed_pair(&bx)
 241                         }
 242                     }
 243
 244                     PassMode::Cast(cast_ty) => {
 245                         let op = match self.locals[mir::RETURN_PLACE] {
 246                             LocalRef::Operand(Some(op)) => op,
 247                             LocalRef::Operand(None) => bug!("use of return before def"),
 248                             LocalRef::Place(cg_place) => {
 249                                 OperandRef {
 250                                     val: Ref(cg_place.llval, cg_place.align),
 251                                     layout: cg_place.layout
 252                                 }
 253                             }
 254                             LocalRef::UnsizedPlace(_) => bug!("return type must be sized"),
 255                         };
 256                         let llslot = match op.val {
 257                             Immediate(_) | Pair(..) => {
 258                                 let scratch = PlaceRef::alloca(&bx, self.fn_ty.ret.layout, "ret");
 259                                 op.val.store(&bx, scratch);
 260                                 scratch.llval
 261                             }
 262                             Ref(llval, align) => {
 263                                 assert_eq!(align.abi(), op.layout.align.abi(),
 264                                            "return place is unaligned!");
 265                                 llval
 266                             }
 267                             UnsizedRef(..) => bug!("return type must be sized"),
 268                         };
 269                         bx.load(
 270                             bx.pointercast(llslot, cast_ty.llvm_type(bx.cx).ptr_to()),
 271                             self.fn_ty.ret.layout.align)
 272                     }
 273
 274                     PassMode::UnsizedIndirect(..) => bug!("return value must be sized"),
 275                 };
 276                 bx.ret(llval);
 277             }
 278
 279             mir::TerminatorKind::Unreachable => {
 280                 bx.unreachable();
 281             }
 282
 283             mir::TerminatorKind::Drop { ref location, target, unwind } => {
 284                 let ty = location.ty(self.mir, bx.tcx()).to_ty(bx.tcx());
 285                 let ty = self.monomorphize(&ty);
 286                 let drop_fn = monomorphize::resolve_drop_in_place(bx.cx.tcx, ty);
 287
 288                 if let ty::InstanceDef::DropGlue(_, None) = drop_fn.def {
 289                     // we don't actually need to drop anything.
 290                     funclet_br(self, bx, target);
 291                     return
 292                 }
 293
 294                 let place = self.codegen_place(&bx, location);
 295                 let (args1, args2);
 296                 let mut args = if let Some(llextra) = place.llextra {
 297                     args2 = [place.llval, llextra];
 298                     &args2[..]
 299                 } else {
 300                     args1 = [place.llval];
 301                     &args1[..]
 302                 };
 303                 let (drop_fn, fn_ty) = match ty.sty {
 304                     ty::TyDynamic(..) => {
 305                         let fn_ty = drop_fn.ty(bx.cx.tcx);
 306                         let sig = common::ty_fn_sig(bx.cx, fn_ty);
 307                         let sig = bx.tcx().normalize_erasing_late_bound_regions(
 308                             ty::ParamEnv::reveal_all(),
 309                             &sig,
 310                         );
 311                         let fn_ty = FnType::new_vtable(bx.cx, sig, &[]);
 312                         let vtable = args[1];
 313                         args = &args[..1];
 314                         (meth::DESTRUCTOR.get_fn(&bx, vtable, &fn_ty), fn_ty)
 315                     }
 316                     _ => {
 317                         (callee::get_fn(bx.cx, drop_fn),
 318                          FnType::of_instance(bx.cx, &drop_fn))
 319                     }
 320                 };
 321                 do_call(self, bx, fn_ty, drop_fn, args,
 322                         Some((ReturnDest::Nothing, target)),
 323                         unwind);
 324             }
 325
 326             mir::TerminatorKind::Assert { ref cond, expected, ref msg, target, cleanup } => {
 327                 let cond = self.codegen_operand(&bx, cond).immediate();
 328                 let mut const_cond = common::const_to_opt_u128(cond, false).map(|c| c == 1);
 329
 330                 // This case can currently arise only from functions marked
 331                 // with #[rustc_inherit_overflow_checks] and inlined from
 332                 // another crate (mostly core::num generic/#[inline] fns),
 333                 // while the current crate doesn't use overflow checks.
 334                 // NOTE: Unlike binops, negation doesn't have its own
 335                 // checked operation, just a comparison with the minimum
 336                 // value, so we have to check for the assert message.
 337                 if !bx.cx.check_overflow {
 338                     if let mir::interpret::EvalErrorKind::OverflowNeg = *msg {
 339                         const_cond = Some(expected);
 340                     }
 341                 }
 342
 343                 // Don't codegen the panic block if success if known.
 344                 if const_cond == Some(expected) {
 345                     funclet_br(self, bx, target);
 346                     return;
 347                 }
 348
 349                 // Pass the condition through llvm.expect for branch hinting.
 350                 let expect = bx.cx.get_intrinsic(&"llvm.expect.i1");
 351                 let cond = bx.call(expect, &[cond, C_bool(bx.cx, expected)], None);
 352
 353                 // Create the failure block and the conditional branch to it.
 354                 let lltarget = llblock(self, target);
 355                 let panic_block = self.new_block("panic");
 356                 if expected {
 357                     bx.cond_br(cond, lltarget, panic_block.llbb());
 358                 } else {
 359                     bx.cond_br(cond, panic_block.llbb(), lltarget);
 360                 }
 361
 362                 // After this point, bx is the block for the call to panic.
 363                 bx = panic_block;
 364                 self.set_debug_loc(&bx, terminator.source_info);
 365
 366                 // Get the location information.
 367                 let loc = bx.sess().codemap().lookup_char_pos(span.lo());
 368                 let filename = Symbol::intern(&loc.file.name.to_string()).as_str();
 369                 let filename = C_str_slice(bx.cx, filename);
 370                 let line = C_u32(bx.cx, loc.line as u32);
 371                 let col = C_u32(bx.cx, loc.col.to_usize() as u32 + 1);
 372                 let align = tcx.data_layout.aggregate_align
 373                     .max(tcx.data_layout.i32_align)
 374                     .max(tcx.data_layout.pointer_align);
 375
 376                 // Put together the arguments to the panic entry point.
 377                 let (lang_item, args) = match *msg {
 378                     EvalErrorKind::BoundsCheck { ref len, ref index } => {
 379                         let len = self.codegen_operand(&mut bx, len).immediate();
 380                         let index = self.codegen_operand(&mut bx, index).immediate();
 381
 382                         let file_line_col = C_struct(bx.cx, &[filename, line, col], false);
 383                         let file_line_col = consts::addr_of(bx.cx,
 384                                                             file_line_col,
 385                                                             align,
 386                                                             Some("panic_bounds_check_loc"));
 387                         (lang_items::PanicBoundsCheckFnLangItem,
 388                          vec![file_line_col, index, len])
 389                     }
 390                     _ => {
 391                         let str = msg.description();
 392                         let msg_str = Symbol::intern(str).as_str();
 393                         let msg_str = C_str_slice(bx.cx, msg_str);
 394                         let msg_file_line_col = C_struct(bx.cx,
 395                                                      &[msg_str, filename, line, col],
 396                                                      false);
 397                         let msg_file_line_col = consts::addr_of(bx.cx,
 398                                                                 msg_file_line_col,
 399                                                                 align,
 400                                                                 Some("panic_loc"));
 401                         (lang_items::PanicFnLangItem,
 402                          vec![msg_file_line_col])
 403                     }
 404                 };
 405
 406                 // Obtain the panic entry point.
 407                 let def_id = common::langcall(bx.tcx(), Some(span), "", lang_item);
 408                 let instance = ty::Instance::mono(bx.tcx(), def_id);
 409                 let fn_ty = FnType::of_instance(bx.cx, &instance);
 410                 let llfn = callee::get_fn(bx.cx, instance);
 411
 412                 // Codegen the actual panic invoke/call.
 413                 do_call(self, bx, fn_ty, llfn, &args, None, cleanup);
 414             }
 415
 416             mir::TerminatorKind::DropAndReplace { .. } => {
 417                 bug!("undesugared DropAndReplace in codegen: {:?}", terminator);
 418             }
 419
 420             mir::TerminatorKind::Call { ref func, ref args, ref destination, cleanup } => {
 421                 // Create the callee. This is a fn ptr or zero-sized and hence a kind of scalar.
 422                 let callee = self.codegen_operand(&bx, func);
 423
 424                 let (instance, mut llfn) = match callee.layout.ty.sty {
 425                     ty::TyFnDef(def_id, substs) => {
 426                         (Some(ty::Instance::resolve(bx.cx.tcx,
 427                                                     ty::ParamEnv::reveal_all(),
 428                                                     def_id,
 429                                                     substs).unwrap()),
 430                          None)
 431                     }
 432                     ty::TyFnPtr(_) => {
 433                         (None, Some(callee.immediate()))
 434                     }
 435                     _ => bug!("{} is not callable", callee.layout.ty)
 436                 };
 437                 let def = instance.map(|i| i.def);
 438                 let sig = callee.layout.ty.fn_sig(bx.tcx());
 439                 let sig = bx.tcx().normalize_erasing_late_bound_regions(
 440                     ty::ParamEnv::reveal_all(),
 441                     &sig,
 442                 );
 443                 let abi = sig.abi;
 444
 445                 // Handle intrinsics old codegen wants Expr's for, ourselves.
 446                 let intrinsic = match def {
 447                     Some(ty::InstanceDef::Intrinsic(def_id))
 448                         => Some(bx.tcx().item_name(def_id).as_str()),
 449                     _ => None
 450                 };
 451                 let intrinsic = intrinsic.as_ref().map(|s| &s[..]);
 452
 453                 if intrinsic == Some("transmute") {
 454                     if let Some(destination_ref) = destination.as_ref() {
 455                         let &(ref dest, target) = destination_ref;
 456                         self.codegen_transmute(&bx, &args[0], dest);
 457                         funclet_br(self, bx, target);
 458                     } else {
 459                         // If we are trying to transmute to an uninhabited type,
 460                         // it is likely there is no allotted destination. In fact,
 461                         // transmuting to an uninhabited type is UB, which means
 462                         // we can do what we like. Here, we declare that transmuting
 463                         // into an uninhabited type is impossible, so anything following
 464                         // it must be unreachable.
 465                         assert_eq!(bx.cx.layout_of(sig.output()).abi, layout::Abi::Uninhabited);
 466                         bx.unreachable();
 467                     }
 468                     return;
 469                 }
 470
 471                 let extra_args = &args[sig.inputs().len()..];
 472                 let extra_args = extra_args.iter().map(|op_arg| {
 473                     let op_ty = op_arg.ty(self.mir, bx.tcx());
 474                     self.monomorphize(&op_ty)
 475                 }).collect::<Vec<_>>();
 476
 477                 let fn_ty = match def {
 478                     Some(ty::InstanceDef::Virtual(..)) => {
 479                         FnType::new_vtable(bx.cx, sig, &extra_args)
 480                     }
 481                     Some(ty::InstanceDef::DropGlue(_, None)) => {
 482                         // empty drop glue - a nop.
 483                         let &(_, target) = destination.as_ref().unwrap();
 484                         funclet_br(self, bx, target);
 485                         return;
 486                     }
 487                     _ => FnType::new(bx.cx, sig, &extra_args)
 488                 };
 489
 490                 // The arguments we'll be passing. Plus one to account for outptr, if used.
 491                 let arg_count = fn_ty.args.len() + fn_ty.ret.is_indirect() as usize;
 492                 let mut llargs = Vec::with_capacity(arg_count);
 493
 494                 // Prepare the return value destination
 495                 let ret_dest = if let Some((ref dest, _)) = *destination {
 496                     let is_intrinsic = intrinsic.is_some();
 497                     self.make_return_dest(&bx, dest, &fn_ty.ret, &mut llargs,
 498                                           is_intrinsic)
 499                 } else {
 500                     ReturnDest::Nothing
 501                 };
 502
 503                 if intrinsic.is_some() && intrinsic != Some("drop_in_place") {
 504                     use intrinsic::codegen_intrinsic_call;
 505
 506                     let dest = match ret_dest {
 507                         _ if fn_ty.ret.is_indirect() => llargs[0],
 508                         ReturnDest::Nothing => {
 509                             C_undef(fn_ty.ret.memory_ty(bx.cx).ptr_to())
 510                         }
 511                         ReturnDest::IndirectOperand(dst, _) |
 512                         ReturnDest::Store(dst) => dst.llval,
 513                         ReturnDest::DirectOperand(_) =>
 514                             bug!("Cannot use direct operand with an intrinsic call")
 515                     };
 516
 517                     let args: Vec<_> = args.iter().enumerate().map(|(i, arg)| {
 518                         // The indices passed to simd_shuffle* in the
 519                         // third argument must be constant. This is
 520                         // checked by const-qualification, which also
 521                         // promotes any complex rvalues to constants.
 522                         if i == 2 && intrinsic.unwrap().starts_with("simd_shuffle") {
 523                             match *arg {
 524                                 // The shuffle array argument is usually not an explicit constant,
 525                                 // but specified directly in the code. This means it gets promoted
 526                                 // and we can then extract the value by evaluating the promoted.
 527                                 mir::Operand::Copy(mir::Place::Promoted(box(index, ty))) |
 528                                 mir::Operand::Move(mir::Place::Promoted(box(index, ty))) => {
 529                                     let param_env = ty::ParamEnv::reveal_all();
 530                                     let cid = mir::interpret::GlobalId {
 531                                         instance: self.instance,
 532                                         promoted: Some(index),
 533                                     };
 534                                     let c = bx.tcx().const_eval(param_env.and(cid));
 535                                     let (llval, ty) = self.simd_shuffle_indices(
 536                                         &bx,
 537                                         terminator.source_info.span,
 538                                         ty,
 539                                         c,
 540                                     );
 541                                     return OperandRef {
 542                                         val: Immediate(llval),
 543                                         layout: bx.cx.layout_of(ty),
 544                                     };
 545
 546                                 },
 547                                 mir::Operand::Copy(_) |
 548                                 mir::Operand::Move(_) => {
 549                                     span_bug!(span, "shuffle indices must be constant");
 550                                 }
 551                                 mir::Operand::Constant(ref constant) => {
 552                                     let c = self.eval_mir_constant(&bx, constant);
 553                                     let (llval, ty) = self.simd_shuffle_indices(
 554                                         &bx,
 555                                         constant.span,
 556                                         constant.ty,
 557                                         c,
 558                                     );
 559                                     return OperandRef {
 560                                         val: Immediate(llval),
 561                                         layout: bx.cx.layout_of(ty)
 562                                     };
 563                                 }
 564                             }
 565                         }
 566
 567                         self.codegen_operand(&bx, arg)
 568                     }).collect();
 569
 570
 571                     let callee_ty = instance.as_ref().unwrap().ty(bx.cx.tcx);
 572                     codegen_intrinsic_call(&bx, callee_ty, &fn_ty, &args, dest,
 573                                          terminator.source_info.span);
 574
 575                     if let ReturnDest::IndirectOperand(dst, _) = ret_dest {
 576                         self.store_return(&bx, ret_dest, &fn_ty.ret, dst.llval);
 577                     }
 578
 579                     if let Some((_, target)) = *destination {
 580                         funclet_br(self, bx, target);
 581                     } else {
 582                         bx.unreachable();
 583                     }
 584
 585                     return;
 586                 }
 587
 588                 // Split the rust-call tupled arguments off.
 589                 let (first_args, untuple) = if abi == Abi::RustCall && !args.is_empty() {
 590                     let (tup, args) = args.split_last().unwrap();
 591                     (args, Some(tup))
 592                 } else {
 593                     (&args[..], None)
 594                 };
 595
 596                 for (i, arg) in first_args.iter().enumerate() {
 597                     let mut op = self.codegen_operand(&bx, arg);
 598                     if let (0, Some(ty::InstanceDef::Virtual(_, idx))) = (i, def) {
 599                         if let Pair(data_ptr, meta) = op.val {
 600                             llfn = Some(meth::VirtualIndex::from_index(idx)
 601                                 .get_fn(&bx, meta, &fn_ty));
 602                             llargs.push(data_ptr);
 603                             continue;
 604                         }
 605                     }
 606
 607                     // The callee needs to own the argument memory if we pass it
 608                     // by-ref, so make a local copy of non-immediate constants.
 609                     match (arg, op.val) {
 610                         (&mir::Operand::Copy(_), Ref(..)) |
 611                         (&mir::Operand::Constant(_), Ref(..)) => {
 612                             let tmp = PlaceRef::alloca(&bx, op.layout, "const");
 613                             op.val.store(&bx, tmp);
 614                             op.val = Ref(tmp.llval, tmp.align);
 615                         }
 616                         (&mir::Operand::Copy(_), UnsizedRef(..)) |
 617                         (&mir::Operand::Constant(_), UnsizedRef(..)) => {
 618                             bug!("tried to pass an unsized argument by copy or constant")
 619                         }
 620                         _ => {}
 621                     }
 622
 623                     self.codegen_argument(&bx, op, &mut llargs, &fn_ty.args[i]);
 624                 }
 625                 if let Some(tup) = untuple {
 626                     self.codegen_arguments_untupled(&bx, tup, &mut llargs,
 627                         &fn_ty.args[first_args.len()..])
 628                 }
 629
 630                 let fn_ptr = match (llfn, instance) {
 631                     (Some(llfn), _) => llfn,
 632                     (None, Some(instance)) => callee::get_fn(bx.cx, instance),
 633                     _ => span_bug!(span, "no llfn for call"),
 634                 };
 635
 636                 do_call(self, bx, fn_ty, fn_ptr, &llargs,
 637                         destination.as_ref().map(|&(_, target)| (ret_dest, target)),
 638                         cleanup);
 639             }
 640             mir::TerminatorKind::GeneratorDrop |
 641             mir::TerminatorKind::Yield { .. } => bug!("generator ops in codegen"),
 642             mir::TerminatorKind::FalseEdges { .. } |
 643             mir::TerminatorKind::FalseUnwind { .. } => bug!("borrowck false edges in codegen"),
 644         }
 645     }
 646
 647     fn codegen_argument(&mut self,
 648                       bx: &Builder<'a, 'll, 'tcx>,
 649                       op: OperandRef<'ll, 'tcx>,
 650                       llargs: &mut Vec<&'ll Value>,
 651                       arg: &ArgType<'tcx, Ty<'tcx>>) {
 652         // Fill padding with undef value, where applicable.
 653         if let Some(ty) = arg.pad {
 654             llargs.push(C_undef(ty.llvm_type(bx.cx)));
 655         }
 656
 657         if arg.is_ignore() {
 658             return;
 659         }
 660
 661         if let PassMode::Pair(..) = arg.mode {
 662             match op.val {
 663                 Pair(a, b) => {
 664                     llargs.push(a);
 665                     llargs.push(b);
 666                     return;
 667                 }
 668                 _ => bug!("codegen_argument: {:?} invalid for pair arugment", op)
 669             }
 670         } else if let PassMode::UnsizedIndirect(..) = arg.mode {
 671             match op.val {
 672                 UnsizedRef(a, b) => {
 673                     llargs.push(a);
 674                     llargs.push(b);
 675                     return;
 676                 }
 677                 _ => bug!("codegen_argument: {:?} invalid for unsized indirect argument", op)
 678             }
 679         }
 680
 681         // Force by-ref if we have to load through a cast pointer.
 682         let (mut llval, align, by_ref) = match op.val {
 683             Immediate(_) | Pair(..) => {
 684                 match arg.mode {
 685                     PassMode::Indirect(_) | PassMode::Cast(_) => {
 686                         let scratch = PlaceRef::alloca(bx, arg.layout, "arg");
 687                         op.val.store(bx, scratch);
 688                         (scratch.llval, scratch.align, true)
 689                     }
 690                     _ => {
 691                         (op.immediate_or_packed_pair(bx), arg.layout.align, false)
 692                     }
 693                 }
 694             }
 695             Ref(llval, align) => {
 696                 if arg.is_indirect() && align.abi() < arg.layout.align.abi() {
 697                     // `foo(packed.large_field)`. We can't pass the (unaligned) field directly. I
 698                     // think that ATM (Rust 1.16) we only pass temporaries, but we shouldn't
 699                     // have scary latent bugs around.
 700
 701                     let scratch = PlaceRef::alloca(bx, arg.layout, "arg");
 702                     base::memcpy_ty(bx, scratch.llval, llval, op.layout, align, MemFlags::empty());
 703                     (scratch.llval, scratch.align, true)
 704                 } else {
 705                     (llval, align, true)
 706                 }
 707             }
 708             UnsizedRef(..) =>
 709                 bug!("codegen_argument: tried to pass unsized operand to sized argument"),
 710         };
 711
 712         if by_ref && !arg.is_indirect() {
 713             // Have to load the argument, maybe while casting it.
 714             if let PassMode::Cast(ty) = arg.mode {
 715                 llval = bx.load(bx.pointercast(llval, ty.llvm_type(bx.cx).ptr_to()),
 716                                  align.min(arg.layout.align));
 717             } else {
 718                 // We can't use `PlaceRef::load` here because the argument
 719                 // may have a type we don't treat as immediate, but the ABI
 720                 // used for this call is passing it by-value. In that case,
 721                 // the load would just produce `OperandValue::Ref` instead
 722                 // of the `OperandValue::Immediate` we need for the call.
 723                 llval = bx.load(llval, align);
 724                 if let layout::Abi::Scalar(ref scalar) = arg.layout.abi {
 725                     if scalar.is_bool() {
 726                         bx.range_metadata(llval, 0..2);
 727                     }
 728                 }
 729                 // We store bools as i8 so we need to truncate to i1.
 730                 llval = base::to_immediate(bx, llval, arg.layout);
 731             }
 732         }
 733
 734         llargs.push(llval);
 735     }
 736
 737     fn codegen_arguments_untupled(&mut self,
 738                                 bx: &Builder<'a, 'll, 'tcx>,
 739                                 operand: &mir::Operand<'tcx>,
 740                                 llargs: &mut Vec<&'ll Value>,
 741                                 args: &[ArgType<'tcx, Ty<'tcx>>]) {
 742         let tuple = self.codegen_operand(bx, operand);
 743
 744         // Handle both by-ref and immediate tuples.
 745         if let Ref(llval, align) = tuple.val {
 746             let tuple_ptr = PlaceRef::new_sized(llval, tuple.layout, align);
 747             for i in 0..tuple.layout.fields.count() {
 748                 let field_ptr = tuple_ptr.project_field(bx, i);
 749                 self.codegen_argument(bx, field_ptr.load(bx), llargs, &args[i]);
 750             }
 751         } else if let UnsizedRef(..) = tuple.val {
 752             bug!("closure arguments must be sized")
 753         } else {
 754             // If the tuple is immediate, the elements are as well.
 755             for i in 0..tuple.layout.fields.count() {
 756                 let op = tuple.extract_field(bx, i);
 757                 self.codegen_argument(bx, op, llargs, &args[i]);
 758             }
 759         }
 760     }
 761
 762     fn get_personality_slot(&mut self, bx: &Builder<'a, 'll, 'tcx>) -> PlaceRef<'ll, 'tcx> {
 763         let cx = bx.cx;
 764         if let Some(slot) = self.personality_slot {
 765             slot
 766         } else {
 767             let layout = cx.layout_of(cx.tcx.intern_tup(&[
 768                 cx.tcx.mk_mut_ptr(cx.tcx.types.u8),
 769                 cx.tcx.types.i32
 770             ]));
 771             let slot = PlaceRef::alloca(bx, layout, "personalityslot");
 772             self.personality_slot = Some(slot);
 773             slot
 774         }
 775     }
 776
 777     /// Return the landingpad wrapper around the given basic block
 778     ///
 779     /// No-op in MSVC SEH scheme.
 780     fn landing_pad_to(&mut self, target_bb: mir::BasicBlock) -> &'ll BasicBlock {
 781         if let Some(block) = self.landing_pads[target_bb] {
 782             return block;
 783         }
 784
 785         let block = self.blocks[target_bb];
 786         let landing_pad = self.landing_pad_uncached(block);
 787         self.landing_pads[target_bb] = Some(landing_pad);
 788         landing_pad
 789     }
 790
 791     fn landing_pad_uncached(&mut self, target_bb: &'ll BasicBlock) -> &'ll BasicBlock {
 792         if base::wants_msvc_seh(self.cx.sess()) {
 793             span_bug!(self.mir.span, "landing pad was not inserted?")
 794         }
 795
 796         let bx = self.new_block("cleanup");
 797
 798         let llpersonality = self.cx.eh_personality();
 799         let llretty = self.landing_pad_type();
 800         let lp = bx.landing_pad(llretty, llpersonality, 1);
 801         bx.set_cleanup(lp);
 802
 803         let slot = self.get_personality_slot(&bx);
 804         slot.storage_live(&bx);
 805         Pair(bx.extract_value(lp, 0), bx.extract_value(lp, 1)).store(&bx, slot);
 806
 807         bx.br(target_bb);
 808         bx.llbb()
 809     }
 810
 811     fn landing_pad_type(&self) -> &'ll Type {
 812         let cx = self.cx;
 813         Type::struct_(cx, &[Type::i8p(cx), Type::i32(cx)], false)
 814     }
 815
 816     fn unreachable_block(&mut self) -> &'ll BasicBlock {
 817         self.unreachable_block.unwrap_or_else(|| {
 818             let bl = self.new_block("unreachable");
 819             bl.unreachable();
 820             self.unreachable_block = Some(bl.llbb());
 821             bl.llbb()
 822         })
 823     }
 824
 825     pub fn new_block(&self, name: &str) -> Builder<'a, 'll, 'tcx> {
 826         Builder::new_block(self.cx, self.llfn, name)
 827     }
 828
 829     pub fn build_block(&self, bb: mir::BasicBlock) -> Builder<'a, 'll, 'tcx> {
 830         let bx = Builder::with_cx(self.cx);
 831         bx.position_at_end(self.blocks[bb]);
 832         bx
 833     }
 834
 835     fn make_return_dest(&mut self, bx: &Builder<'a, 'll, 'tcx>,
 836                         dest: &mir::Place<'tcx>, fn_ret: &ArgType<'tcx, Ty<'tcx>>,
 837                         llargs: &mut Vec<&'ll Value>, is_intrinsic: bool)
 838                         -> ReturnDest<'ll, 'tcx> {
 839         // If the return is ignored, we can just return a do-nothing ReturnDest
 840         if fn_ret.is_ignore() {
 841             return ReturnDest::Nothing;
 842         }
 843         let dest = if let mir::Place::Local(index) = *dest {
 844             match self.locals[index] {
 845                 LocalRef::Place(dest) => dest,
 846                 LocalRef::UnsizedPlace(_) => bug!("return type must be sized"),
 847                 LocalRef::Operand(None) => {
 848                     // Handle temporary places, specifically Operand ones, as
 849                     // they don't have allocas
 850                     return if fn_ret.is_indirect() {
 851                         // Odd, but possible, case, we have an operand temporary,
 852                         // but the calling convention has an indirect return.
 853                         let tmp = PlaceRef::alloca(bx, fn_ret.layout, "tmp_ret");
 854                         tmp.storage_live(bx);
 855                         llargs.push(tmp.llval);
 856                         ReturnDest::IndirectOperand(tmp, index)
 857                     } else if is_intrinsic {
 858                         // Currently, intrinsics always need a location to store
 859                         // the result. so we create a temporary alloca for the
 860                         // result
 861                         let tmp = PlaceRef::alloca(bx, fn_ret.layout, "tmp_ret");
 862                         tmp.storage_live(bx);
 863                         ReturnDest::IndirectOperand(tmp, index)
 864                     } else {
 865                         ReturnDest::DirectOperand(index)
 866                     };
 867                 }
 868                 LocalRef::Operand(Some(_)) => {
 869                     bug!("place local already assigned to");
 870                 }
 871             }
 872         } else {
 873             self.codegen_place(bx, dest)
 874         };
 875         if fn_ret.is_indirect() {
 876             if dest.align.abi() < dest.layout.align.abi() {
 877                 // Currently, MIR code generation does not create calls
 878                 // that store directly to fields of packed structs (in
 879                 // fact, the calls it creates write only to temps),
 880                 //
 881                 // If someone changes that, please update this code path
 882                 // to create a temporary.
 883                 span_bug!(self.mir.span, "can't directly store to unaligned value");
 884             }
 885             llargs.push(dest.llval);
 886             ReturnDest::Nothing
 887         } else {
 888             ReturnDest::Store(dest)
 889         }
 890     }
 891
 892     fn codegen_transmute(&mut self, bx: &Builder<'a, 'll, 'tcx>,
 893                        src: &mir::Operand<'tcx>,
 894                        dst: &mir::Place<'tcx>) {
 895         if let mir::Place::Local(index) = *dst {
 896             match self.locals[index] {
 897                 LocalRef::Place(place) => self.codegen_transmute_into(bx, src, place),
 898                 LocalRef::UnsizedPlace(_) => bug!("transmute must not involve unsized locals"),
 899                 LocalRef::Operand(None) => {
 900                     let dst_layout = bx.cx.layout_of(self.monomorphized_place_ty(dst));
 901                     assert!(!dst_layout.ty.has_erasable_regions());
 902                     let place = PlaceRef::alloca(bx, dst_layout, "transmute_temp");
 903                     place.storage_live(bx);
 904                     self.codegen_transmute_into(bx, src, place);
 905                     let op = place.load(bx);
 906                     place.storage_dead(bx);
 907                     self.locals[index] = LocalRef::Operand(Some(op));
 908                 }
 909                 LocalRef::Operand(Some(op)) => {
 910                     assert!(op.layout.is_zst(),
 911                             "assigning to initialized SSAtemp");
 912                 }
 913             }
 914         } else {
 915             let dst = self.codegen_place(bx, dst);
 916             self.codegen_transmute_into(bx, src, dst);
 917         }
 918     }
 919
 920     fn codegen_transmute_into(&mut self, bx: &Builder<'a, 'll, 'tcx>,
 921                             src: &mir::Operand<'tcx>,
 922                             dst: PlaceRef<'ll, 'tcx>) {
 923         let src = self.codegen_operand(bx, src);
 924         let llty = src.layout.llvm_type(bx.cx);
 925         let cast_ptr = bx.pointercast(dst.llval, llty.ptr_to());
 926         let align = src.layout.align.min(dst.layout.align);
 927         src.val.store(bx, PlaceRef::new_sized(cast_ptr, src.layout, align));
 928     }
 929
 930
 931     // Stores the return value of a function call into it's final location.
 932     fn store_return(&mut self,
 933                     bx: &Builder<'a, 'll, 'tcx>,
 934                     dest: ReturnDest<'ll, 'tcx>,
 935                     ret_ty: &ArgType<'tcx, Ty<'tcx>>,
 936                     llval: &'ll Value) {
 937         use self::ReturnDest::*;
 938
 939         match dest {
 940             Nothing => (),
 941             Store(dst) => ret_ty.store(bx, llval, dst),
 942             IndirectOperand(tmp, index) => {
 943                 let op = tmp.load(bx);
 944                 tmp.storage_dead(bx);
 945                 self.locals[index] = LocalRef::Operand(Some(op));
 946             }
 947             DirectOperand(index) => {
 948                 // If there is a cast, we have to store and reload.
 949                 let op = if let PassMode::Cast(_) = ret_ty.mode {
 950                     let tmp = PlaceRef::alloca(bx, ret_ty.layout, "tmp_ret");
 951                     tmp.storage_live(bx);
 952                     ret_ty.store(bx, llval, tmp);
 953                     let op = tmp.load(bx);
 954                     tmp.storage_dead(bx);
 955                     op
 956                 } else {
 957                     OperandRef::from_immediate_or_packed_pair(bx, llval, ret_ty.layout)
 958                 };
 959                 self.locals[index] = LocalRef::Operand(Some(op));
 960             }
 961         }
 962     }
 963 }
 964
 965 enum ReturnDest<'ll, 'tcx> {
 966     // Do nothing, the return value is indirect or ignored
 967     Nothing,
 968     // Store the return value to the pointer
 969     Store(PlaceRef<'ll, 'tcx>),
 970     // Stores an indirect return value to an operand local place
 971     IndirectOperand(PlaceRef<'ll, 'tcx>, mir::Local),
 972     // Stores a direct return value to an operand local place
 973     DirectOperand(mir::Local)
 974 }