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