src/librustc_codegen_ssa/mir/block.rs

   1 use super::operand::OperandRef;
   2 use super::operand::OperandValue::{Immediate, Pair, Ref};
   3 use super::place::PlaceRef;
   4 use super::{FunctionCx, LocalRef};
   5
   6 use crate::base;
   7 use crate::common::{self, IntPredicate};
   8 use crate::meth;
   9 use crate::traits::*;
  10 use crate::MemFlags;
  11
  12 use rustc_ast::ast;
  13 use rustc_hir::lang_items;
  14 use rustc_index::vec::Idx;
  15 use rustc_middle::mir;
  16 use rustc_middle::mir::interpret::{AllocId, ConstValue, Pointer, Scalar};
  17 use rustc_middle::mir::AssertKind;
  18 use rustc_middle::ty::layout::{FnAbiExt, HasTyCtxt};
  19 use rustc_middle::ty::{self, Instance, Ty, TypeFoldable};
  20 use rustc_span::{source_map::Span, symbol::Symbol};
  21 use rustc_target::abi::call::{ArgAbi, FnAbi, PassMode};
  22 use rustc_target::abi::{self, LayoutOf};
  23 use rustc_target::spec::abi::Abi;
  24
  25 use std::borrow::Cow;
  26
  27 /// Used by `FunctionCx::codegen_terminator` for emitting common patterns
  28 /// e.g., creating a basic block, calling a function, etc.
  29 struct TerminatorCodegenHelper<'tcx> {
  30     bb: mir::BasicBlock,
  31     terminator: &'tcx mir::Terminator<'tcx>,
  32     funclet_bb: Option<mir::BasicBlock>,
  33 }
  34
  35 impl<'a, 'tcx> TerminatorCodegenHelper<'tcx> {
  36     /// Returns the associated funclet from `FunctionCx::funclets` for the
  37     /// `funclet_bb` member if it is not `None`.
  38     fn funclet<'b, Bx: BuilderMethods<'a, 'tcx>>(
  39         &self,
  40         fx: &'b mut FunctionCx<'a, 'tcx, Bx>,
  41     ) -> Option<&'b Bx::Funclet> {
  42         match self.funclet_bb {
  43             Some(funcl) => fx.funclets[funcl].as_ref(),
  44             None => None,
  45         }
  46     }
  47
  48     fn lltarget<Bx: BuilderMethods<'a, 'tcx>>(
  49         &self,
  50         fx: &mut FunctionCx<'a, 'tcx, Bx>,
  51         target: mir::BasicBlock,
  52     ) -> (Bx::BasicBlock, bool) {
  53         let span = self.terminator.source_info.span;
  54         let lltarget = fx.blocks[target];
  55         let target_funclet = fx.cleanup_kinds[target].funclet_bb(target);
  56         match (self.funclet_bb, target_funclet) {
  57             (None, None) => (lltarget, false),
  58             (Some(f), Some(t_f)) if f == t_f || !base::wants_msvc_seh(fx.cx.tcx().sess) => {
  59                 (lltarget, false)
  60             }
  61             // jump *into* cleanup - need a landing pad if GNU
  62             (None, Some(_)) => (fx.landing_pad_to(target), false),
  63             (Some(_), None) => span_bug!(span, "{:?} - jump out of cleanup?", self.terminator),
  64             (Some(_), Some(_)) => (fx.landing_pad_to(target), true),
  65         }
  66     }
  67
  68     /// Create a basic block.
  69     fn llblock<Bx: BuilderMethods<'a, 'tcx>>(
  70         &self,
  71         fx: &mut FunctionCx<'a, 'tcx, Bx>,
  72         target: mir::BasicBlock,
  73     ) -> Bx::BasicBlock {
  74         let (lltarget, is_cleanupret) = self.lltarget(fx, target);
  75         if is_cleanupret {
  76             // MSVC cross-funclet jump - need a trampoline
  77
  78             debug!("llblock: creating cleanup trampoline for {:?}", target);
  79             let name = &format!("{:?}_cleanup_trampoline_{:?}", self.bb, target);
  80             let mut trampoline = fx.new_block(name);
  81             trampoline.cleanup_ret(self.funclet(fx).unwrap(), Some(lltarget));
  82             trampoline.llbb()
  83         } else {
  84             lltarget
  85         }
  86     }
  87
  88     fn funclet_br<Bx: BuilderMethods<'a, 'tcx>>(
  89         &self,
  90         fx: &mut FunctionCx<'a, 'tcx, Bx>,
  91         bx: &mut Bx,
  92         target: mir::BasicBlock,
  93     ) {
  94         let (lltarget, is_cleanupret) = self.lltarget(fx, target);
  95         if is_cleanupret {
  96             // micro-optimization: generate a `ret` rather than a jump
  97             // to a trampoline.
  98             bx.cleanup_ret(self.funclet(fx).unwrap(), Some(lltarget));
  99         } else {
 100             bx.br(lltarget);
 101         }
 102     }
 103
 104     /// Call `fn_ptr` of `fn_abi` with the arguments `llargs`, the optional
 105     /// return destination `destination` and the cleanup function `cleanup`.
 106     fn do_call<Bx: BuilderMethods<'a, 'tcx>>(
 107         &self,
 108         fx: &mut FunctionCx<'a, 'tcx, Bx>,
 109         bx: &mut Bx,
 110         fn_abi: FnAbi<'tcx, Ty<'tcx>>,
 111         fn_ptr: Bx::Value,
 112         llargs: &[Bx::Value],
 113         destination: Option<(ReturnDest<'tcx, Bx::Value>, mir::BasicBlock)>,
 114         cleanup: Option<mir::BasicBlock>,
 115     ) {
 116         // If there is a cleanup block and the function we're calling can unwind, then
 117         // do an invoke, otherwise do a call.
 118         if let Some(cleanup) = cleanup.filter(|_| fn_abi.can_unwind) {
 119             let ret_bx = if let Some((_, target)) = destination {
 120                 fx.blocks[target]
 121             } else {
 122                 fx.unreachable_block()
 123             };
 124             let invokeret =
 125                 bx.invoke(fn_ptr, &llargs, ret_bx, self.llblock(fx, cleanup), self.funclet(fx));
 126             bx.apply_attrs_callsite(&fn_abi, invokeret);
 127
 128             if let Some((ret_dest, target)) = destination {
 129                 let mut ret_bx = fx.build_block(target);
 130                 fx.set_debug_loc(&mut ret_bx, self.terminator.source_info);
 131                 fx.store_return(&mut ret_bx, ret_dest, &fn_abi.ret, invokeret);
 132             }
 133         } else {
 134             let llret = bx.call(fn_ptr, &llargs, self.funclet(fx));
 135             bx.apply_attrs_callsite(&fn_abi, llret);
 136             if fx.mir[self.bb].is_cleanup {
 137                 // Cleanup is always the cold path. Don't inline
 138                 // drop glue. Also, when there is a deeply-nested
 139                 // struct, there are "symmetry" issues that cause
 140                 // exponential inlining - see issue #41696.
 141                 bx.do_not_inline(llret);
 142             }
 143
 144             if let Some((ret_dest, target)) = destination {
 145                 fx.store_return(bx, ret_dest, &fn_abi.ret, llret);
 146                 self.funclet_br(fx, bx, target);
 147             } else {
 148                 bx.unreachable();
 149             }
 150         }
 151     }
 152
 153     // Generate sideeffect intrinsic if jumping to any of the targets can form
 154     // a loop.
 155     fn maybe_sideeffect<Bx: BuilderMethods<'a, 'tcx>>(
 156         &self,
 157         mir: &'tcx mir::Body<'tcx>,
 158         bx: &mut Bx,
 159         targets: &[mir::BasicBlock],
 160     ) {
 161         if bx.tcx().sess.opts.debugging_opts.insert_sideeffect {
 162             if targets.iter().any(|&target| {
 163                 target <= self.bb
 164                     && target.start_location().is_predecessor_of(self.bb.start_location(), mir)
 165             }) {
 166                 bx.sideeffect();
 167             }
 168         }
 169     }
 170 }
 171
 172 /// Codegen implementations for some terminator variants.
 173 impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
 174     /// Generates code for a `Resume` terminator.
 175     fn codegen_resume_terminator(&mut self, helper: TerminatorCodegenHelper<'tcx>, mut bx: Bx) {
 176         if let Some(funclet) = helper.funclet(self) {
 177             bx.cleanup_ret(funclet, None);
 178         } else {
 179             let slot = self.get_personality_slot(&mut bx);
 180             let lp0 = slot.project_field(&mut bx, 0);
 181             let lp0 = bx.load_operand(lp0).immediate();
 182             let lp1 = slot.project_field(&mut bx, 1);
 183             let lp1 = bx.load_operand(lp1).immediate();
 184             slot.storage_dead(&mut bx);
 185
 186             let mut lp = bx.const_undef(self.landing_pad_type());
 187             lp = bx.insert_value(lp, lp0, 0);
 188             lp = bx.insert_value(lp, lp1, 1);
 189             bx.resume(lp);
 190         }
 191     }
 192
 193     fn codegen_switchint_terminator(
 194         &mut self,
 195         helper: TerminatorCodegenHelper<'tcx>,
 196         mut bx: Bx,
 197         discr: &mir::Operand<'tcx>,
 198         switch_ty: Ty<'tcx>,
 199         values: &Cow<'tcx, [u128]>,
 200         targets: &Vec<mir::BasicBlock>,
 201     ) {
 202         let discr = self.codegen_operand(&mut bx, &discr);
 203         // `switch_ty` is redundant, sanity-check that.
 204         assert_eq!(discr.layout.ty, switch_ty);
 205         if targets.len() == 2 {
 206             // If there are two targets, emit br instead of switch
 207             let lltrue = helper.llblock(self, targets[0]);
 208             let llfalse = helper.llblock(self, targets[1]);
 209             if switch_ty == bx.tcx().types.bool {
 210                 helper.maybe_sideeffect(self.mir, &mut bx, targets.as_slice());
 211                 // Don't generate trivial icmps when switching on bool
 212                 if let [0] = values[..] {
 213                     bx.cond_br(discr.immediate(), llfalse, lltrue);
 214                 } else {
 215                     assert_eq!(&values[..], &[1]);
 216                     bx.cond_br(discr.immediate(), lltrue, llfalse);
 217                 }
 218             } else {
 219                 let switch_llty = bx.immediate_backend_type(bx.layout_of(switch_ty));
 220                 let llval = bx.const_uint_big(switch_llty, values[0]);
 221                 let cmp = bx.icmp(IntPredicate::IntEQ, discr.immediate(), llval);
 222                 helper.maybe_sideeffect(self.mir, &mut bx, targets.as_slice());
 223                 bx.cond_br(cmp, lltrue, llfalse);
 224             }
 225         } else {
 226             helper.maybe_sideeffect(self.mir, &mut bx, targets.as_slice());
 227             let (otherwise, targets) = targets.split_last().unwrap();
 228             bx.switch(
 229                 discr.immediate(),
 230                 helper.llblock(self, *otherwise),
 231                 values
 232                     .iter()
 233                     .zip(targets)
 234                     .map(|(&value, target)| (value, helper.llblock(self, *target))),
 235             );
 236         }
 237     }
 238
 239     fn codegen_return_terminator(&mut self, mut bx: Bx) {
 240         // Call `va_end` if this is the definition of a C-variadic function.
 241         if self.fn_abi.c_variadic {
 242             // The `VaList` "spoofed" argument is just after all the real arguments.
 243             let va_list_arg_idx = self.fn_abi.args.len();
 244             match self.locals[mir::Local::new(1 + va_list_arg_idx)] {
 245                 LocalRef::Place(va_list) => {
 246                     bx.va_end(va_list.llval);
 247                 }
 248                 _ => bug!("C-variadic function must have a `VaList` place"),
 249             }
 250         }
 251         if self.fn_abi.ret.layout.abi.is_uninhabited() {
 252             // Functions with uninhabited return values are marked `noreturn`,
 253             // so we should make sure that we never actually do.
 254             // We play it safe by using a well-defined `abort`, but we could go for immediate UB
 255             // if that turns out to be helpful.
 256             bx.abort();
 257             // `abort` does not terminate the block, so we still need to generate
 258             // an `unreachable` terminator after it.
 259             bx.unreachable();
 260             return;
 261         }
 262         let llval = match self.fn_abi.ret.mode {
 263             PassMode::Ignore | PassMode::Indirect(..) => {
 264                 bx.ret_void();
 265                 return;
 266             }
 267
 268             PassMode::Direct(_) | PassMode::Pair(..) => {
 269                 let op = self.codegen_consume(&mut bx, mir::Place::return_place().as_ref());
 270                 if let Ref(llval, _, align) = op.val {
 271                     bx.load(llval, align)
 272                 } else {
 273                     op.immediate_or_packed_pair(&mut bx)
 274                 }
 275             }
 276
 277             PassMode::Cast(cast_ty) => {
 278                 let op = match self.locals[mir::RETURN_PLACE] {
 279                     LocalRef::Operand(Some(op)) => op,
 280                     LocalRef::Operand(None) => bug!("use of return before def"),
 281                     LocalRef::Place(cg_place) => OperandRef {
 282                         val: Ref(cg_place.llval, None, cg_place.align),
 283                         layout: cg_place.layout,
 284                     },
 285                     LocalRef::UnsizedPlace(_) => bug!("return type must be sized"),
 286                 };
 287                 let llslot = match op.val {
 288                     Immediate(_) | Pair(..) => {
 289                         let scratch = PlaceRef::alloca(&mut bx, self.fn_abi.ret.layout);
 290                         op.val.store(&mut bx, scratch);
 291                         scratch.llval
 292                     }
 293                     Ref(llval, _, align) => {
 294                         assert_eq!(align, op.layout.align.abi, "return place is unaligned!");
 295                         llval
 296                     }
 297                 };
 298                 let addr = bx.pointercast(llslot, bx.type_ptr_to(bx.cast_backend_type(&cast_ty)));
 299                 bx.load(addr, self.fn_abi.ret.layout.align.abi)
 300             }
 301         };
 302         bx.ret(llval);
 303     }
 304
 305     fn codegen_drop_terminator(
 306         &mut self,
 307         helper: TerminatorCodegenHelper<'tcx>,
 308         mut bx: Bx,
 309         location: mir::Place<'tcx>,
 310         target: mir::BasicBlock,
 311         unwind: Option<mir::BasicBlock>,
 312     ) {
 313         let ty = location.ty(self.mir, bx.tcx()).ty;
 314         let ty = self.monomorphize(&ty);
 315         let drop_fn = Instance::resolve_drop_in_place(bx.tcx(), ty);
 316
 317         if let ty::InstanceDef::DropGlue(_, None) = drop_fn.def {
 318             // we don't actually need to drop anything.
 319             helper.maybe_sideeffect(self.mir, &mut bx, &[target]);
 320             helper.funclet_br(self, &mut bx, target);
 321             return;
 322         }
 323
 324         let place = self.codegen_place(&mut bx, location.as_ref());
 325         let (args1, args2);
 326         let mut args = if let Some(llextra) = place.llextra {
 327             args2 = [place.llval, llextra];
 328             &args2[..]
 329         } else {
 330             args1 = [place.llval];
 331             &args1[..]
 332         };
 333         let (drop_fn, fn_abi) = match ty.kind {
 334             // FIXME(eddyb) perhaps move some of this logic into
 335             // `Instance::resolve_drop_in_place`?
 336             ty::Dynamic(..) => {
 337                 let virtual_drop = Instance {
 338                     def: ty::InstanceDef::Virtual(drop_fn.def_id(), 0),
 339                     substs: drop_fn.substs,
 340                 };
 341                 let fn_abi = FnAbi::of_instance(&bx, virtual_drop, &[]);
 342                 let vtable = args[1];
 343                 args = &args[..1];
 344                 (meth::DESTRUCTOR.get_fn(&mut bx, vtable, &fn_abi), fn_abi)
 345             }
 346             _ => (bx.get_fn_addr(drop_fn), FnAbi::of_instance(&bx, drop_fn, &[])),
 347         };
 348         helper.maybe_sideeffect(self.mir, &mut bx, &[target]);
 349         helper.do_call(
 350             self,
 351             &mut bx,
 352             fn_abi,
 353             drop_fn,
 354             args,
 355             Some((ReturnDest::Nothing, target)),
 356             unwind,
 357         );
 358     }
 359
 360     fn codegen_assert_terminator(
 361         &mut self,
 362         helper: TerminatorCodegenHelper<'tcx>,
 363         mut bx: Bx,
 364         terminator: &mir::Terminator<'tcx>,
 365         cond: &mir::Operand<'tcx>,
 366         expected: bool,
 367         msg: &mir::AssertMessage<'tcx>,
 368         target: mir::BasicBlock,
 369         cleanup: Option<mir::BasicBlock>,
 370     ) {
 371         let span = terminator.source_info.span;
 372         let cond = self.codegen_operand(&mut bx, cond).immediate();
 373         let mut const_cond = bx.const_to_opt_u128(cond, false).map(|c| c == 1);
 374
 375         // This case can currently arise only from functions marked
 376         // with #[rustc_inherit_overflow_checks] and inlined from
 377         // another crate (mostly core::num generic/#[inline] fns),
 378         // while the current crate doesn't use overflow checks.
 379         // NOTE: Unlike binops, negation doesn't have its own
 380         // checked operation, just a comparison with the minimum
 381         // value, so we have to check for the assert message.
 382         if !bx.check_overflow() {
 383             if let AssertKind::OverflowNeg(_) = *msg {
 384                 const_cond = Some(expected);
 385             }
 386         }
 387
 388         // Don't codegen the panic block if success if known.
 389         if const_cond == Some(expected) {
 390             helper.maybe_sideeffect(self.mir, &mut bx, &[target]);
 391             helper.funclet_br(self, &mut bx, target);
 392             return;
 393         }
 394
 395         // Pass the condition through llvm.expect for branch hinting.
 396         let cond = bx.expect(cond, expected);
 397
 398         // Create the failure block and the conditional branch to it.
 399         let lltarget = helper.llblock(self, target);
 400         let panic_block = self.new_block("panic");
 401         helper.maybe_sideeffect(self.mir, &mut bx, &[target]);
 402         if expected {
 403             bx.cond_br(cond, lltarget, panic_block.llbb());
 404         } else {
 405             bx.cond_br(cond, panic_block.llbb(), lltarget);
 406         }
 407
 408         // After this point, bx is the block for the call to panic.
 409         bx = panic_block;
 410         self.set_debug_loc(&mut bx, terminator.source_info);
 411
 412         // Get the location information.
 413         let location = self.get_caller_location(&mut bx, span).immediate();
 414
 415         // Put together the arguments to the panic entry point.
 416         let (lang_item, args) = match msg {
 417             AssertKind::BoundsCheck { ref len, ref index } => {
 418                 let len = self.codegen_operand(&mut bx, len).immediate();
 419                 let index = self.codegen_operand(&mut bx, index).immediate();
 420                 // It's `fn panic_bounds_check(index: usize, len: usize)`,
 421                 // and `#[track_caller]` adds an implicit third argument.
 422                 (lang_items::PanicBoundsCheckFnLangItem, vec![index, len, location])
 423             }
 424             _ => {
 425                 let msg_str = Symbol::intern(msg.description());
 426                 let msg = bx.const_str(msg_str);
 427                 // It's `pub fn panic(expr: &str)`, with the wide reference being passed
 428                 // as two arguments, and `#[track_caller]` adds an implicit third argument.
 429                 (lang_items::PanicFnLangItem, vec![msg.0, msg.1, location])
 430             }
 431         };
 432
 433         // Obtain the panic entry point.
 434         let def_id = common::langcall(bx.tcx(), Some(span), "", lang_item);
 435         let instance = ty::Instance::mono(bx.tcx(), def_id);
 436         let fn_abi = FnAbi::of_instance(&bx, instance, &[]);
 437         let llfn = bx.get_fn_addr(instance);
 438
 439         // Codegen the actual panic invoke/call.
 440         helper.do_call(self, &mut bx, fn_abi, llfn, &args, None, cleanup);
 441     }
 442
 443     /// Returns `true` if this is indeed a panic intrinsic and codegen is done.
 444     fn codegen_panic_intrinsic(
 445         &mut self,
 446         helper: &TerminatorCodegenHelper<'tcx>,
 447         bx: &mut Bx,
 448         intrinsic: Option<&str>,
 449         instance: Option<Instance<'tcx>>,
 450         span: Span,
 451         destination: &Option<(mir::Place<'tcx>, mir::BasicBlock)>,
 452         cleanup: Option<mir::BasicBlock>,
 453     ) -> bool {
 454         // Emit a panic or a no-op for `assert_*` intrinsics.
 455         // These are intrinsics that compile to panics so that we can get a message
 456         // which mentions the offending type, even from a const context.
 457         #[derive(Debug, PartialEq)]
 458         enum AssertIntrinsic {
 459             Inhabited,
 460             ZeroValid,
 461             UninitValid,
 462         };
 463         let panic_intrinsic = intrinsic.and_then(|i| match i {
 464             // FIXME: Move to symbols instead of strings.
 465             "assert_inhabited" => Some(AssertIntrinsic::Inhabited),
 466             "assert_zero_valid" => Some(AssertIntrinsic::ZeroValid),
 467             "assert_uninit_valid" => Some(AssertIntrinsic::UninitValid),
 468             _ => None,
 469         });
 470         if let Some(intrinsic) = panic_intrinsic {
 471             use AssertIntrinsic::*;
 472             let ty = instance.unwrap().substs.type_at(0);
 473             let layout = bx.layout_of(ty);
 474             let do_panic = match intrinsic {
 475                 Inhabited => layout.abi.is_uninhabited(),
 476                 // We unwrap as the error type is `!`.
 477                 ZeroValid => !layout.might_permit_raw_init(bx, /*zero:*/ true).unwrap(),
 478                 // We unwrap as the error type is `!`.
 479                 UninitValid => !layout.might_permit_raw_init(bx, /*zero:*/ false).unwrap(),
 480             };
 481             if do_panic {
 482                 let msg_str = if layout.abi.is_uninhabited() {
 483                     // Use this error even for the other intrinsics as it is more precise.
 484                     format!("attempted to instantiate uninhabited type `{}`", ty)
 485                 } else if intrinsic == ZeroValid {
 486                     format!("attempted to zero-initialize type `{}`, which is invalid", ty)
 487                 } else {
 488                     format!("attempted to leave type `{}` uninitialized, which is invalid", ty)
 489                 };
 490                 let msg = bx.const_str(Symbol::intern(&msg_str));
 491                 let location = self.get_caller_location(bx, span).immediate();
 492
 493                 // Obtain the panic entry point.
 494                 // FIXME: dedup this with `codegen_assert_terminator` above.
 495                 let def_id =
 496                     common::langcall(bx.tcx(), Some(span), "", lang_items::PanicFnLangItem);
 497                 let instance = ty::Instance::mono(bx.tcx(), def_id);
 498                 let fn_abi = FnAbi::of_instance(bx, instance, &[]);
 499                 let llfn = bx.get_fn_addr(instance);
 500
 501                 if let Some((_, target)) = destination.as_ref() {
 502                     helper.maybe_sideeffect(self.mir, bx, &[*target]);
 503                 }
 504                 // Codegen the actual panic invoke/call.
 505                 helper.do_call(
 506                     self,
 507                     bx,
 508                     fn_abi,
 509                     llfn,
 510                     &[msg.0, msg.1, location],
 511                     destination.as_ref().map(|(_, bb)| (ReturnDest::Nothing, *bb)),
 512                     cleanup,
 513                 );
 514             } else {
 515                 // a NOP
 516                 let target = destination.as_ref().unwrap().1;
 517                 helper.maybe_sideeffect(self.mir, bx, &[target]);
 518                 helper.funclet_br(self, bx, target)
 519             }
 520             true
 521         } else {
 522             false
 523         }
 524     }
 525
 526     fn codegen_call_terminator(
 527         &mut self,
 528         helper: TerminatorCodegenHelper<'tcx>,
 529         mut bx: Bx,
 530         terminator: &mir::Terminator<'tcx>,
 531         func: &mir::Operand<'tcx>,
 532         args: &Vec<mir::Operand<'tcx>>,
 533         destination: &Option<(mir::Place<'tcx>, mir::BasicBlock)>,
 534         cleanup: Option<mir::BasicBlock>,
 535         fn_span: Span,
 536     ) {
 537         let span = terminator.source_info.span;
 538         // Create the callee. This is a fn ptr or zero-sized and hence a kind of scalar.
 539         let callee = self.codegen_operand(&mut bx, func);
 540
 541         let (instance, mut llfn) = match callee.layout.ty.kind {
 542             ty::FnDef(def_id, substs) => (
 543                 Some(
 544                     ty::Instance::resolve(bx.tcx(), ty::ParamEnv::reveal_all(), def_id, substs)
 545                         .unwrap()
 546                         .unwrap(),
 547                 ),
 548                 None,
 549             ),
 550             ty::FnPtr(_) => (None, Some(callee.immediate())),
 551             _ => bug!("{} is not callable", callee.layout.ty),
 552         };
 553         let def = instance.map(|i| i.def);
 554
 555         if let Some(ty::InstanceDef::DropGlue(_, None)) = def {
 556             // Empty drop glue; a no-op.
 557             let &(_, target) = destination.as_ref().unwrap();
 558             helper.maybe_sideeffect(self.mir, &mut bx, &[target]);
 559             helper.funclet_br(self, &mut bx, target);
 560             return;
 561         }
 562
 563         // FIXME(eddyb) avoid computing this if possible, when `instance` is
 564         // available - right now `sig` is only needed for getting the `abi`
 565         // and figuring out how many extra args were passed to a C-variadic `fn`.
 566         let sig = callee.layout.ty.fn_sig(bx.tcx());
 567         let abi = sig.abi();
 568
 569         // Handle intrinsics old codegen wants Expr's for, ourselves.
 570         let intrinsic = match def {
 571             Some(ty::InstanceDef::Intrinsic(def_id)) => Some(bx.tcx().item_name(def_id).as_str()),
 572             _ => None,
 573         };
 574         let intrinsic = intrinsic.as_ref().map(|s| &s[..]);
 575
 576         let extra_args = &args[sig.inputs().skip_binder().len()..];
 577         let extra_args = extra_args
 578             .iter()
 579             .map(|op_arg| {
 580                 let op_ty = op_arg.ty(self.mir, bx.tcx());
 581                 self.monomorphize(&op_ty)
 582             })
 583             .collect::<Vec<_>>();
 584
 585         let fn_abi = match instance {
 586             Some(instance) => FnAbi::of_instance(&bx, instance, &extra_args),
 587             None => FnAbi::of_fn_ptr(&bx, sig, &extra_args),
 588         };
 589
 590         if intrinsic == Some("transmute") {
 591             if let Some(destination_ref) = destination.as_ref() {
 592                 let &(dest, target) = destination_ref;
 593                 self.codegen_transmute(&mut bx, &args[0], dest);
 594                 helper.maybe_sideeffect(self.mir, &mut bx, &[target]);
 595                 helper.funclet_br(self, &mut bx, target);
 596             } else {
 597                 // If we are trying to transmute to an uninhabited type,
 598                 // it is likely there is no allotted destination. In fact,
 599                 // transmuting to an uninhabited type is UB, which means
 600                 // we can do what we like. Here, we declare that transmuting
 601                 // into an uninhabited type is impossible, so anything following
 602                 // it must be unreachable.
 603                 assert_eq!(fn_abi.ret.layout.abi, abi::Abi::Uninhabited);
 604                 bx.unreachable();
 605             }
 606             return;
 607         }
 608
 609         // For normal codegen, this Miri-specific intrinsic should never occur.
 610         if intrinsic == Some("miri_start_panic") {
 611             bug!("`miri_start_panic` should never end up in compiled code");
 612         }
 613
 614         if self.codegen_panic_intrinsic(
 615             &helper,
 616             &mut bx,
 617             intrinsic,
 618             instance,
 619             span,
 620             destination,
 621             cleanup,
 622         ) {
 623             return;
 624         }
 625
 626         // The arguments we'll be passing. Plus one to account for outptr, if used.
 627         let arg_count = fn_abi.args.len() + fn_abi.ret.is_indirect() as usize;
 628         let mut llargs = Vec::with_capacity(arg_count);
 629
 630         // Prepare the return value destination
 631         let ret_dest = if let Some((dest, _)) = *destination {
 632             let is_intrinsic = intrinsic.is_some();
 633             self.make_return_dest(&mut bx, dest, &fn_abi.ret, &mut llargs, is_intrinsic)
 634         } else {
 635             ReturnDest::Nothing
 636         };
 637
 638         if intrinsic == Some("caller_location") {
 639             if let Some((_, target)) = destination.as_ref() {
 640                 let location = self.get_caller_location(&mut bx, fn_span);
 641
 642                 if let ReturnDest::IndirectOperand(tmp, _) = ret_dest {
 643                     location.val.store(&mut bx, tmp);
 644                 }
 645                 self.store_return(&mut bx, ret_dest, &fn_abi.ret, location.immediate());
 646
 647                 helper.maybe_sideeffect(self.mir, &mut bx, &[*target]);
 648                 helper.funclet_br(self, &mut bx, *target);
 649             }
 650             return;
 651         }
 652
 653         if intrinsic.is_some() && intrinsic != Some("drop_in_place") {
 654             let dest = match ret_dest {
 655                 _ if fn_abi.ret.is_indirect() => llargs[0],
 656                 ReturnDest::Nothing => {
 657                     bx.const_undef(bx.type_ptr_to(bx.arg_memory_ty(&fn_abi.ret)))
 658                 }
 659                 ReturnDest::IndirectOperand(dst, _) | ReturnDest::Store(dst) => dst.llval,
 660                 ReturnDest::DirectOperand(_) => {
 661                     bug!("Cannot use direct operand with an intrinsic call")
 662                 }
 663             };
 664
 665             let args: Vec<_> = args
 666                 .iter()
 667                 .enumerate()
 668                 .map(|(i, arg)| {
 669                     // The indices passed to simd_shuffle* in the
 670                     // third argument must be constant. This is
 671                     // checked by const-qualification, which also
 672                     // promotes any complex rvalues to constants.
 673                     if i == 2 && intrinsic.unwrap().starts_with("simd_shuffle") {
 674                         if let mir::Operand::Constant(constant) = arg {
 675                             let c = self.eval_mir_constant(constant);
 676                             let (llval, ty) = self.simd_shuffle_indices(
 677                                 &bx,
 678                                 constant.span,
 679                                 constant.literal.ty,
 680                                 c,
 681                             );
 682                             return OperandRef { val: Immediate(llval), layout: bx.layout_of(ty) };
 683                         } else {
 684                             span_bug!(span, "shuffle indices must be constant");
 685                         }
 686                     }
 687
 688                     self.codegen_operand(&mut bx, arg)
 689                 })
 690                 .collect();
 691
 692             bx.codegen_intrinsic_call(
 693                 *instance.as_ref().unwrap(),
 694                 &fn_abi,
 695                 &args,
 696                 dest,
 697                 terminator.source_info.span,
 698                 self.instance,
 699             );
 700
 701             if let ReturnDest::IndirectOperand(dst, _) = ret_dest {
 702                 self.store_return(&mut bx, ret_dest, &fn_abi.ret, dst.llval);
 703             }
 704
 705             if let Some((_, target)) = *destination {
 706                 helper.maybe_sideeffect(self.mir, &mut bx, &[target]);
 707                 helper.funclet_br(self, &mut bx, target);
 708             } else {
 709                 bx.unreachable();
 710             }
 711
 712             return;
 713         }
 714
 715         // Split the rust-call tupled arguments off.
 716         let (first_args, untuple) = if abi == Abi::RustCall && !args.is_empty() {
 717             let (tup, args) = args.split_last().unwrap();
 718             (args, Some(tup))
 719         } else {
 720             (&args[..], None)
 721         };
 722
 723         'make_args: for (i, arg) in first_args.iter().enumerate() {
 724             let mut op = self.codegen_operand(&mut bx, arg);
 725
 726             if let (0, Some(ty::InstanceDef::Virtual(_, idx))) = (i, def) {
 727                 if let Pair(..) = op.val {
 728                     // In the case of Rc<Self>, we need to explicitly pass a
 729                     // *mut RcBox<Self> with a Scalar (not ScalarPair) ABI. This is a hack
 730                     // that is understood elsewhere in the compiler as a method on
 731                     // `dyn Trait`.
 732                     // To get a `*mut RcBox<Self>`, we just keep unwrapping newtypes until
 733                     // we get a value of a built-in pointer type
 734                     'descend_newtypes: while !op.layout.ty.is_unsafe_ptr()
 735                         && !op.layout.ty.is_region_ptr()
 736                     {
 737                         for i in 0..op.layout.fields.count() {
 738                             let field = op.extract_field(&mut bx, i);
 739                             if !field.layout.is_zst() {
 740                                 // we found the one non-zero-sized field that is allowed
 741                                 // now find *its* non-zero-sized field, or stop if it's a
 742                                 // pointer
 743                                 op = field;
 744                                 continue 'descend_newtypes;
 745                             }
 746                         }
 747
 748                         span_bug!(span, "receiver has no non-zero-sized fields {:?}", op);
 749                     }
 750
 751                     // now that we have `*dyn Trait` or `&dyn Trait`, split it up into its
 752                     // data pointer and vtable. Look up the method in the vtable, and pass
 753                     // the data pointer as the first argument
 754                     match op.val {
 755                         Pair(data_ptr, meta) => {
 756                             llfn = Some(
 757                                 meth::VirtualIndex::from_index(idx).get_fn(&mut bx, meta, &fn_abi),
 758                             );
 759                             llargs.push(data_ptr);
 760                             continue 'make_args;
 761                         }
 762                         other => bug!("expected a Pair, got {:?}", other),
 763                     }
 764                 } else if let Ref(data_ptr, Some(meta), _) = op.val {
 765                     // by-value dynamic dispatch
 766                     llfn = Some(meth::VirtualIndex::from_index(idx).get_fn(&mut bx, meta, &fn_abi));
 767                     llargs.push(data_ptr);
 768                     continue;
 769                 } else {
 770                     span_bug!(span, "can't codegen a virtual call on {:?}", op);
 771                 }
 772             }
 773
 774             // The callee needs to own the argument memory if we pass it
 775             // by-ref, so make a local copy of non-immediate constants.
 776             match (arg, op.val) {
 777                 (&mir::Operand::Copy(_), Ref(_, None, _))
 778                 | (&mir::Operand::Constant(_), Ref(_, None, _)) => {
 779                     let tmp = PlaceRef::alloca(&mut bx, op.layout);
 780                     op.val.store(&mut bx, tmp);
 781                     op.val = Ref(tmp.llval, None, tmp.align);
 782                 }
 783                 _ => {}
 784             }
 785
 786             self.codegen_argument(&mut bx, op, &mut llargs, &fn_abi.args[i]);
 787         }
 788         if let Some(tup) = untuple {
 789             self.codegen_arguments_untupled(
 790                 &mut bx,
 791                 tup,
 792                 &mut llargs,
 793                 &fn_abi.args[first_args.len()..],
 794             )
 795         }
 796
 797         let needs_location =
 798             instance.map_or(false, |i| i.def.requires_caller_location(self.cx.tcx()));
 799         if needs_location {
 800             assert_eq!(
 801                 fn_abi.args.len(),
 802                 args.len() + 1,
 803                 "#[track_caller] fn's must have 1 more argument in their ABI than in their MIR",
 804             );
 805             let location = self.get_caller_location(&mut bx, fn_span);
 806             debug!(
 807                 "codegen_call_terminator({:?}): location={:?} (fn_span {:?})",
 808                 terminator, location, fn_span
 809             );
 810
 811             let last_arg = fn_abi.args.last().unwrap();
 812             self.codegen_argument(&mut bx, location, &mut llargs, last_arg);
 813         }
 814
 815         let fn_ptr = match (llfn, instance) {
 816             (Some(llfn), _) => llfn,
 817             (None, Some(instance)) => bx.get_fn_addr(instance),
 818             _ => span_bug!(span, "no llfn for call"),
 819         };
 820
 821         if let Some((_, target)) = destination.as_ref() {
 822             helper.maybe_sideeffect(self.mir, &mut bx, &[*target]);
 823         }
 824         helper.do_call(
 825             self,
 826             &mut bx,
 827             fn_abi,
 828             fn_ptr,
 829             &llargs,
 830             destination.as_ref().map(|&(_, target)| (ret_dest, target)),
 831             cleanup,
 832         );
 833     }
 834
 835     fn codegen_asm_terminator(
 836         &mut self,
 837         helper: TerminatorCodegenHelper<'tcx>,
 838         mut bx: Bx,
 839         terminator: &mir::Terminator<'tcx>,
 840         template: &[ast::InlineAsmTemplatePiece],
 841         operands: &[mir::InlineAsmOperand<'tcx>],
 842         options: ast::InlineAsmOptions,
 843         line_spans: &[Span],
 844         destination: Option<mir::BasicBlock>,
 845     ) {
 846         let span = terminator.source_info.span;
 847
 848         let operands: Vec<_> = operands
 849             .iter()
 850             .map(|op| match *op {
 851                 mir::InlineAsmOperand::In { reg, ref value } => {
 852                     let value = self.codegen_operand(&mut bx, value);
 853                     InlineAsmOperandRef::In { reg, value }
 854                 }
 855                 mir::InlineAsmOperand::Out { reg, late, ref place } => {
 856                     let place = place.map(|place| self.codegen_place(&mut bx, place.as_ref()));
 857                     InlineAsmOperandRef::Out { reg, late, place }
 858                 }
 859                 mir::InlineAsmOperand::InOut { reg, late, ref in_value, ref out_place } => {
 860                     let in_value = self.codegen_operand(&mut bx, in_value);
 861                     let out_place =
 862                         out_place.map(|out_place| self.codegen_place(&mut bx, out_place.as_ref()));
 863                     InlineAsmOperandRef::InOut { reg, late, in_value, out_place }
 864                 }
 865                 mir::InlineAsmOperand::Const { ref value } => {
 866                     if let mir::Operand::Constant(constant) = value {
 867                         let const_value = self
 868                             .eval_mir_constant(constant)
 869                             .unwrap_or_else(|_| span_bug!(span, "asm const cannot be resolved"));
 870                         let ty = constant.literal.ty;
 871                         let size = bx.layout_of(ty).size;
 872                         let scalar = match const_value {
 873                             // Promoted constants are evaluated into a ByRef instead of a Scalar,
 874                             // but we want the scalar value here.
 875                             ConstValue::ByRef { alloc, offset } => {
 876                                 let ptr = Pointer::new(AllocId(0), offset);
 877                                 alloc
 878                                     .read_scalar(&bx, ptr, size)
 879                                     .and_then(|s| s.not_undef())
 880                                     .unwrap_or_else(|e| {
 881                                         bx.tcx().sess.span_err(
 882                                             span,
 883                                             &format!("Could not evaluate asm const: {}", e),
 884                                         );
 885
 886                                         // We are erroring out, just emit a dummy constant.
 887                                         Scalar::from_u64(0)
 888                                     })
 889                             }
 890                             _ => span_bug!(span, "expected ByRef for promoted asm const"),
 891                         };
 892                         let value = scalar.assert_bits(size);
 893                         let string = match ty.kind {
 894                             ty::Uint(_) => value.to_string(),
 895                             ty::Int(int_ty) => {
 896                                 match int_ty.normalize(bx.tcx().sess.target.ptr_width) {
 897                                     ast::IntTy::I8 => (value as i8).to_string(),
 898                                     ast::IntTy::I16 => (value as i16).to_string(),
 899                                     ast::IntTy::I32 => (value as i32).to_string(),
 900                                     ast::IntTy::I64 => (value as i64).to_string(),
 901                                     ast::IntTy::I128 => (value as i128).to_string(),
 902                                     ast::IntTy::Isize => unreachable!(),
 903                                 }
 904                             }
 905                             ty::Float(ast::FloatTy::F32) => {
 906                                 f32::from_bits(value as u32).to_string()
 907                             }
 908                             ty::Float(ast::FloatTy::F64) => {
 909                                 f64::from_bits(value as u64).to_string()
 910                             }
 911                             _ => span_bug!(span, "asm const has bad type {}", ty),
 912                         };
 913                         InlineAsmOperandRef::Const { string }
 914                     } else {
 915                         span_bug!(span, "asm const is not a constant");
 916                     }
 917                 }
 918                 mir::InlineAsmOperand::SymFn { ref value } => {
 919                     let literal = self.monomorphize(&value.literal);
 920                     if let ty::FnDef(def_id, substs) = literal.ty.kind {
 921                         let instance = ty::Instance::resolve_for_fn_ptr(
 922                             bx.tcx(),
 923                             ty::ParamEnv::reveal_all(),
 924                             def_id,
 925                             substs,
 926                         )
 927                         .unwrap();
 928                         InlineAsmOperandRef::SymFn { instance }
 929                     } else {
 930                         span_bug!(span, "invalid type for asm sym (fn)");
 931                     }
 932                 }
 933                 mir::InlineAsmOperand::SymStatic { def_id } => {
 934                     InlineAsmOperandRef::SymStatic { def_id }
 935                 }
 936             })
 937             .collect();
 938
 939         bx.codegen_inline_asm(template, &operands, options, line_spans);
 940
 941         if let Some(target) = destination {
 942             helper.funclet_br(self, &mut bx, target);
 943         } else {
 944             bx.unreachable();
 945         }
 946     }
 947 }
 948
 949 impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
 950     pub fn codegen_block(&mut self, bb: mir::BasicBlock) {
 951         let mut bx = self.build_block(bb);
 952         let mir = self.mir;
 953         let data = &mir[bb];
 954
 955         debug!("codegen_block({:?}={:?})", bb, data);
 956
 957         for statement in &data.statements {
 958             bx = self.codegen_statement(bx, statement);
 959         }
 960
 961         self.codegen_terminator(bx, bb, data.terminator());
 962     }
 963
 964     fn codegen_terminator(
 965         &mut self,
 966         mut bx: Bx,
 967         bb: mir::BasicBlock,
 968         terminator: &'tcx mir::Terminator<'tcx>,
 969     ) {
 970         debug!("codegen_terminator: {:?}", terminator);
 971
 972         // Create the cleanup bundle, if needed.
 973         let funclet_bb = self.cleanup_kinds[bb].funclet_bb(bb);
 974         let helper = TerminatorCodegenHelper { bb, terminator, funclet_bb };
 975
 976         self.set_debug_loc(&mut bx, terminator.source_info);
 977         match terminator.kind {
 978             mir::TerminatorKind::Resume => self.codegen_resume_terminator(helper, bx),
 979
 980             mir::TerminatorKind::Abort => {
 981                 bx.abort();
 982                 // `abort` does not terminate the block, so we still need to generate
 983                 // an `unreachable` terminator after it.
 984                 bx.unreachable();
 985             }
 986
 987             mir::TerminatorKind::Goto { target } => {
 988                 helper.maybe_sideeffect(self.mir, &mut bx, &[target]);
 989                 helper.funclet_br(self, &mut bx, target);
 990             }
 991
 992             mir::TerminatorKind::SwitchInt { ref discr, switch_ty, ref values, ref targets } => {
 993                 self.codegen_switchint_terminator(helper, bx, discr, switch_ty, values, targets);
 994             }
 995
 996             mir::TerminatorKind::Return => {
 997                 self.codegen_return_terminator(bx);
 998             }
 999
1000             mir::TerminatorKind::Unreachable => {
1001                 bx.unreachable();
1002             }
1003
1004             mir::TerminatorKind::Drop { place, target, unwind } => {
1005                 self.codegen_drop_terminator(helper, bx, place, target, unwind);
1006             }
1007
1008             mir::TerminatorKind::Assert { ref cond, expected, ref msg, target, cleanup } => {
1009                 self.codegen_assert_terminator(
1010                     helper, bx, terminator, cond, expected, msg, target, cleanup,
1011                 );
1012             }
1013
1014             mir::TerminatorKind::DropAndReplace { .. } => {
1015                 bug!("undesugared DropAndReplace in codegen: {:?}", terminator);
1016             }
1017
1018             mir::TerminatorKind::Call {
1019                 ref func,
1020                 ref args,
1021                 ref destination,
1022                 cleanup,
1023                 from_hir_call: _,
1024                 fn_span,
1025             } => {
1026                 self.codegen_call_terminator(
1027                     helper,
1028                     bx,
1029                     terminator,
1030                     func,
1031                     args,
1032                     destination,
1033                     cleanup,
1034                     fn_span,
1035                 );
1036             }
1037             mir::TerminatorKind::GeneratorDrop | mir::TerminatorKind::Yield { .. } => {
1038                 bug!("generator ops in codegen")
1039             }
1040             mir::TerminatorKind::FalseEdge { .. } | mir::TerminatorKind::FalseUnwind { .. } => {
1041                 bug!("borrowck false edges in codegen")
1042             }
1043
1044             mir::TerminatorKind::InlineAsm {
1045                 template,
1046                 ref operands,
1047                 options,
1048                 line_spans,
1049                 destination,
1050             } => {
1051                 self.codegen_asm_terminator(
1052                     helper,
1053                     bx,
1054                     terminator,
1055                     template,
1056                     operands,
1057                     options,
1058                     line_spans,
1059                     destination,
1060                 );
1061             }
1062         }
1063     }
1064
1065     fn codegen_argument(
1066         &mut self,
1067         bx: &mut Bx,
1068         op: OperandRef<'tcx, Bx::Value>,
1069         llargs: &mut Vec<Bx::Value>,
1070         arg: &ArgAbi<'tcx, Ty<'tcx>>,
1071     ) {
1072         // Fill padding with undef value, where applicable.
1073         if let Some(ty) = arg.pad {
1074             llargs.push(bx.const_undef(bx.reg_backend_type(&ty)))
1075         }
1076
1077         if arg.is_ignore() {
1078             return;
1079         }
1080
1081         if let PassMode::Pair(..) = arg.mode {
1082             match op.val {
1083                 Pair(a, b) => {
1084                     llargs.push(a);
1085                     llargs.push(b);
1086                     return;
1087                 }
1088                 _ => bug!("codegen_argument: {:?} invalid for pair argument", op),
1089             }
1090         } else if arg.is_unsized_indirect() {
1091             match op.val {
1092                 Ref(a, Some(b), _) => {
1093                     llargs.push(a);
1094                     llargs.push(b);
1095                     return;
1096                 }
1097                 _ => bug!("codegen_argument: {:?} invalid for unsized indirect argument", op),
1098             }
1099         }
1100
1101         // Force by-ref if we have to load through a cast pointer.
1102         let (mut llval, align, by_ref) = match op.val {
1103             Immediate(_) | Pair(..) => match arg.mode {
1104                 PassMode::Indirect(..) | PassMode::Cast(_) => {
1105                     let scratch = PlaceRef::alloca(bx, arg.layout);
1106                     op.val.store(bx, scratch);
1107                     (scratch.llval, scratch.align, true)
1108                 }
1109                 _ => (op.immediate_or_packed_pair(bx), arg.layout.align.abi, false),
1110             },
1111             Ref(llval, _, align) => {
1112                 if arg.is_indirect() && align < arg.layout.align.abi {
1113                     // `foo(packed.large_field)`. We can't pass the (unaligned) field directly. I
1114                     // think that ATM (Rust 1.16) we only pass temporaries, but we shouldn't
1115                     // have scary latent bugs around.
1116
1117                     let scratch = PlaceRef::alloca(bx, arg.layout);
1118                     base::memcpy_ty(
1119                         bx,
1120                         scratch.llval,
1121                         scratch.align,
1122                         llval,
1123                         align,
1124                         op.layout,
1125                         MemFlags::empty(),
1126                     );
1127                     (scratch.llval, scratch.align, true)
1128                 } else {
1129                     (llval, align, true)
1130                 }
1131             }
1132         };
1133
1134         if by_ref && !arg.is_indirect() {
1135             // Have to load the argument, maybe while casting it.
1136             if let PassMode::Cast(ty) = arg.mode {
1137                 let addr = bx.pointercast(llval, bx.type_ptr_to(bx.cast_backend_type(&ty)));
1138                 llval = bx.load(addr, align.min(arg.layout.align.abi));
1139             } else {
1140                 // We can't use `PlaceRef::load` here because the argument
1141                 // may have a type we don't treat as immediate, but the ABI
1142                 // used for this call is passing it by-value. In that case,
1143                 // the load would just produce `OperandValue::Ref` instead
1144                 // of the `OperandValue::Immediate` we need for the call.
1145                 llval = bx.load(llval, align);
1146                 if let abi::Abi::Scalar(ref scalar) = arg.layout.abi {
1147                     if scalar.is_bool() {
1148                         bx.range_metadata(llval, 0..2);
1149                     }
1150                 }
1151                 // We store bools as `i8` so we need to truncate to `i1`.
1152                 llval = base::to_immediate(bx, llval, arg.layout);
1153             }
1154         }
1155
1156         llargs.push(llval);
1157     }
1158
1159     fn codegen_arguments_untupled(
1160         &mut self,
1161         bx: &mut Bx,
1162         operand: &mir::Operand<'tcx>,
1163         llargs: &mut Vec<Bx::Value>,
1164         args: &[ArgAbi<'tcx, Ty<'tcx>>],
1165     ) {
1166         let tuple = self.codegen_operand(bx, operand);
1167
1168         // Handle both by-ref and immediate tuples.
1169         if let Ref(llval, None, align) = tuple.val {
1170             let tuple_ptr = PlaceRef::new_sized_aligned(llval, tuple.layout, align);
1171             for i in 0..tuple.layout.fields.count() {
1172                 let field_ptr = tuple_ptr.project_field(bx, i);
1173                 let field = bx.load_operand(field_ptr);
1174                 self.codegen_argument(bx, field, llargs, &args[i]);
1175             }
1176         } else if let Ref(_, Some(_), _) = tuple.val {
1177             bug!("closure arguments must be sized")
1178         } else {
1179             // If the tuple is immediate, the elements are as well.
1180             for i in 0..tuple.layout.fields.count() {
1181                 let op = tuple.extract_field(bx, i);
1182                 self.codegen_argument(bx, op, llargs, &args[i]);
1183             }
1184         }
1185     }
1186
1187     fn get_caller_location(&mut self, bx: &mut Bx, span: Span) -> OperandRef<'tcx, Bx::Value> {
1188         self.caller_location.unwrap_or_else(|| {
1189             let topmost = span.ctxt().outer_expn().expansion_cause().unwrap_or(span);
1190             let caller = bx.tcx().sess.source_map().lookup_char_pos(topmost.lo());
1191             let const_loc = bx.tcx().const_caller_location((
1192                 Symbol::intern(&caller.file.name.to_string()),
1193                 caller.line as u32,
1194                 caller.col_display as u32 + 1,
1195             ));
1196             OperandRef::from_const(bx, const_loc, bx.tcx().caller_location_ty())
1197         })
1198     }
1199
1200     fn get_personality_slot(&mut self, bx: &mut Bx) -> PlaceRef<'tcx, Bx::Value> {
1201         let cx = bx.cx();
1202         if let Some(slot) = self.personality_slot {
1203             slot
1204         } else {
1205             let layout = cx.layout_of(
1206                 cx.tcx().intern_tup(&[cx.tcx().mk_mut_ptr(cx.tcx().types.u8), cx.tcx().types.i32]),
1207             );
1208             let slot = PlaceRef::alloca(bx, layout);
1209             self.personality_slot = Some(slot);
1210             slot
1211         }
1212     }
1213
1214     /// Returns the landing-pad wrapper around the given basic block.
1215     ///
1216     /// No-op in MSVC SEH scheme.
1217     fn landing_pad_to(&mut self, target_bb: mir::BasicBlock) -> Bx::BasicBlock {
1218         if let Some(block) = self.landing_pads[target_bb] {
1219             return block;
1220         }
1221
1222         let block = self.blocks[target_bb];
1223         let landing_pad = self.landing_pad_uncached(block);
1224         self.landing_pads[target_bb] = Some(landing_pad);
1225         landing_pad
1226     }
1227
1228     fn landing_pad_uncached(&mut self, target_bb: Bx::BasicBlock) -> Bx::BasicBlock {
1229         if base::wants_msvc_seh(self.cx.sess()) {
1230             span_bug!(self.mir.span, "landing pad was not inserted?")
1231         }
1232
1233         let mut bx = self.new_block("cleanup");
1234
1235         let llpersonality = self.cx.eh_personality();
1236         let llretty = self.landing_pad_type();
1237         let lp = bx.landing_pad(llretty, llpersonality, 1);
1238         bx.set_cleanup(lp);
1239
1240         let slot = self.get_personality_slot(&mut bx);
1241         slot.storage_live(&mut bx);
1242         Pair(bx.extract_value(lp, 0), bx.extract_value(lp, 1)).store(&mut bx, slot);
1243
1244         bx.br(target_bb);
1245         bx.llbb()
1246     }
1247
1248     fn landing_pad_type(&self) -> Bx::Type {
1249         let cx = self.cx;
1250         cx.type_struct(&[cx.type_i8p(), cx.type_i32()], false)
1251     }
1252
1253     fn unreachable_block(&mut self) -> Bx::BasicBlock {
1254         self.unreachable_block.unwrap_or_else(|| {
1255             let mut bx = self.new_block("unreachable");
1256             bx.unreachable();
1257             self.unreachable_block = Some(bx.llbb());
1258             bx.llbb()
1259         })
1260     }
1261
1262     pub fn new_block(&self, name: &str) -> Bx {
1263         Bx::new_block(self.cx, self.llfn, name)
1264     }
1265
1266     pub fn build_block(&self, bb: mir::BasicBlock) -> Bx {
1267         let mut bx = Bx::with_cx(self.cx);
1268         bx.position_at_end(self.blocks[bb]);
1269         bx
1270     }
1271
1272     fn make_return_dest(
1273         &mut self,
1274         bx: &mut Bx,
1275         dest: mir::Place<'tcx>,
1276         fn_ret: &ArgAbi<'tcx, Ty<'tcx>>,
1277         llargs: &mut Vec<Bx::Value>,
1278         is_intrinsic: bool,
1279     ) -> ReturnDest<'tcx, Bx::Value> {
1280         // If the return is ignored, we can just return a do-nothing `ReturnDest`.
1281         if fn_ret.is_ignore() {
1282             return ReturnDest::Nothing;
1283         }
1284         let dest = if let Some(index) = dest.as_local() {
1285             match self.locals[index] {
1286                 LocalRef::Place(dest) => dest,
1287                 LocalRef::UnsizedPlace(_) => bug!("return type must be sized"),
1288                 LocalRef::Operand(None) => {
1289                     // Handle temporary places, specifically `Operand` ones, as
1290                     // they don't have `alloca`s.
1291                     return if fn_ret.is_indirect() {
1292                         // Odd, but possible, case, we have an operand temporary,
1293                         // but the calling convention has an indirect return.
1294                         let tmp = PlaceRef::alloca(bx, fn_ret.layout);
1295                         tmp.storage_live(bx);
1296                         llargs.push(tmp.llval);
1297                         ReturnDest::IndirectOperand(tmp, index)
1298                     } else if is_intrinsic {
1299                         // Currently, intrinsics always need a location to store
1300                         // the result, so we create a temporary `alloca` for the
1301                         // result.
1302                         let tmp = PlaceRef::alloca(bx, fn_ret.layout);
1303                         tmp.storage_live(bx);
1304                         ReturnDest::IndirectOperand(tmp, index)
1305                     } else {
1306                         ReturnDest::DirectOperand(index)
1307                     };
1308                 }
1309                 LocalRef::Operand(Some(_)) => {
1310                     bug!("place local already assigned to");
1311                 }
1312             }
1313         } else {
1314             self.codegen_place(
1315                 bx,
1316                 mir::PlaceRef { local: dest.local, projection: &dest.projection },
1317             )
1318         };
1319         if fn_ret.is_indirect() {
1320             if dest.align < dest.layout.align.abi {
1321                 // Currently, MIR code generation does not create calls
1322                 // that store directly to fields of packed structs (in
1323                 // fact, the calls it creates write only to temps).
1324                 //
1325                 // If someone changes that, please update this code path
1326                 // to create a temporary.
1327                 span_bug!(self.mir.span, "can't directly store to unaligned value");
1328             }
1329             llargs.push(dest.llval);
1330             ReturnDest::Nothing
1331         } else {
1332             ReturnDest::Store(dest)
1333         }
1334     }
1335
1336     fn codegen_transmute(&mut self, bx: &mut Bx, src: &mir::Operand<'tcx>, dst: mir::Place<'tcx>) {
1337         if let Some(index) = dst.as_local() {
1338             match self.locals[index] {
1339                 LocalRef::Place(place) => self.codegen_transmute_into(bx, src, place),
1340                 LocalRef::UnsizedPlace(_) => bug!("transmute must not involve unsized locals"),
1341                 LocalRef::Operand(None) => {
1342                     let dst_layout = bx.layout_of(self.monomorphized_place_ty(dst.as_ref()));
1343                     assert!(!dst_layout.ty.has_erasable_regions());
1344                     let place = PlaceRef::alloca(bx, dst_layout);
1345                     place.storage_live(bx);
1346                     self.codegen_transmute_into(bx, src, place);
1347                     let op = bx.load_operand(place);
1348                     place.storage_dead(bx);
1349                     self.locals[index] = LocalRef::Operand(Some(op));
1350                     self.debug_introduce_local(bx, index);
1351                 }
1352                 LocalRef::Operand(Some(op)) => {
1353                     assert!(op.layout.is_zst(), "assigning to initialized SSAtemp");
1354                 }
1355             }
1356         } else {
1357             let dst = self.codegen_place(bx, dst.as_ref());
1358             self.codegen_transmute_into(bx, src, dst);
1359         }
1360     }
1361
1362     fn codegen_transmute_into(
1363         &mut self,
1364         bx: &mut Bx,
1365         src: &mir::Operand<'tcx>,
1366         dst: PlaceRef<'tcx, Bx::Value>,
1367     ) {
1368         let src = self.codegen_operand(bx, src);
1369         let llty = bx.backend_type(src.layout);
1370         let cast_ptr = bx.pointercast(dst.llval, bx.type_ptr_to(llty));
1371         let align = src.layout.align.abi.min(dst.align);
1372         src.val.store(bx, PlaceRef::new_sized_aligned(cast_ptr, src.layout, align));
1373     }
1374
1375     // Stores the return value of a function call into it's final location.
1376     fn store_return(
1377         &mut self,
1378         bx: &mut Bx,
1379         dest: ReturnDest<'tcx, Bx::Value>,
1380         ret_abi: &ArgAbi<'tcx, Ty<'tcx>>,
1381         llval: Bx::Value,
1382     ) {
1383         use self::ReturnDest::*;
1384
1385         match dest {
1386             Nothing => (),
1387             Store(dst) => bx.store_arg(&ret_abi, llval, dst),
1388             IndirectOperand(tmp, index) => {
1389                 let op = bx.load_operand(tmp);
1390                 tmp.storage_dead(bx);
1391                 self.locals[index] = LocalRef::Operand(Some(op));
1392                 self.debug_introduce_local(bx, index);
1393             }
1394             DirectOperand(index) => {
1395                 // If there is a cast, we have to store and reload.
1396                 let op = if let PassMode::Cast(_) = ret_abi.mode {
1397                     let tmp = PlaceRef::alloca(bx, ret_abi.layout);
1398                     tmp.storage_live(bx);
1399                     bx.store_arg(&ret_abi, llval, tmp);
1400                     let op = bx.load_operand(tmp);
1401                     tmp.storage_dead(bx);
1402                     op
1403                 } else {
1404                     OperandRef::from_immediate_or_packed_pair(bx, llval, ret_abi.layout)
1405                 };
1406                 self.locals[index] = LocalRef::Operand(Some(op));
1407                 self.debug_introduce_local(bx, index);
1408             }
1409         }
1410     }
1411 }
1412
1413 enum ReturnDest<'tcx, V> {
1414     // Do nothing; the return value is indirect or ignored.
1415     Nothing,
1416     // Store the return value to the pointer.
1417     Store(PlaceRef<'tcx, V>),
1418     // Store an indirect return value to an operand local place.
1419     IndirectOperand(PlaceRef<'tcx, V>, mir::Local),
1420     // Store a direct return value to an operand local place.
1421     DirectOperand(mir::Local),
1422 }