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