1 //! See docs in `build/expr/mod.rs`.
3 use rustc_index::vec::Idx;
4 use rustc_middle::ty::util::IntTypeExt;
5 use rustc_target::abi::{Abi, Primitive};
7 use crate::build::expr::as_place::PlaceBase;
8 use crate::build::expr::category::{Category, RvalueFunc};
9 use crate::build::{BlockAnd, BlockAndExtension, Builder, NeedsTemporary};
10 use rustc_hir::lang_items::LangItem;
11 use rustc_middle::middle::region;
12 use rustc_middle::mir::AssertKind;
13 use rustc_middle::mir::Place;
14 use rustc_middle::mir::*;
15 use rustc_middle::thir::*;
16 use rustc_middle::ty::cast::{mir_cast_kind, CastTy};
17 use rustc_middle::ty::{self, Ty, UpvarSubsts};
20 impl<'a, 'tcx> Builder<'a, 'tcx> {
21 /// Returns an rvalue suitable for use until the end of the current
24 /// The operand returned from this function will *not be valid* after
25 /// an ExprKind::Scope is passed, so please do *not* return it from
26 /// functions to avoid bad miscompiles.
27 pub(crate) fn as_local_rvalue(
31 ) -> BlockAnd<Rvalue<'tcx>> {
32 let local_scope = self.local_scope();
33 self.as_rvalue(block, Some(local_scope), expr)
36 /// Compile `expr`, yielding an rvalue.
37 pub(crate) fn as_rvalue(
39 mut block: BasicBlock,
40 scope: Option<region::Scope>,
42 ) -> BlockAnd<Rvalue<'tcx>> {
43 debug!("expr_as_rvalue(block={:?}, scope={:?}, expr={:?})", block, scope, expr);
46 let expr_span = expr.span;
47 let source_info = this.source_info(expr_span);
50 ExprKind::ThreadLocalRef(did) => block.and(Rvalue::ThreadLocalRef(did)),
51 ExprKind::Scope { region_scope, lint_level, value } => {
52 let region_scope = (region_scope, source_info);
53 this.in_scope(region_scope, lint_level, |this| {
54 this.as_rvalue(block, scope, &this.thir[value])
57 ExprKind::Repeat { value, count } => {
58 if Some(0) == count.try_eval_usize(this.tcx, this.param_env) {
59 this.build_zero_repeat(block, value, scope, source_info)
61 let value_operand = unpack!(
62 block = this.as_operand(
70 block.and(Rvalue::Repeat(value_operand, count))
73 ExprKind::Binary { op, lhs, rhs } => {
76 this.as_operand(block, scope, &this.thir[lhs], None, NeedsTemporary::Maybe)
80 this.as_operand(block, scope, &this.thir[rhs], None, NeedsTemporary::No)
82 this.build_binary_op(block, op, expr_span, expr.ty, lhs, rhs)
84 ExprKind::Unary { op, arg } => {
87 this.as_operand(block, scope, &this.thir[arg], None, NeedsTemporary::No)
89 // Check for -MIN on signed integers
90 if this.check_overflow && op == UnOp::Neg && expr.ty.is_signed() {
91 let bool_ty = this.tcx.types.bool;
93 let minval = this.minval_literal(expr_span, expr.ty);
94 let is_min = this.temp(bool_ty, expr_span);
100 Rvalue::BinaryOp(BinOp::Eq, Box::new((arg.to_copy(), minval))),
105 Operand::Move(is_min),
107 AssertKind::OverflowNeg(arg.to_copy()),
111 block.and(Rvalue::UnaryOp(op, arg))
113 ExprKind::Box { value } => {
114 let value = &this.thir[value];
117 // `exchange_malloc` is unsafe but box is safe, so need a new scope.
118 let synth_scope = this.new_source_scope(
120 LintLevel::Inherited,
121 Some(Safety::BuiltinUnsafe),
123 let synth_info = SourceInfo { span: expr_span, scope: synth_scope };
125 let size = this.temp(tcx.types.usize, expr_span);
126 this.cfg.push_assign(
130 Rvalue::NullaryOp(NullOp::SizeOf, value.ty),
133 let align = this.temp(tcx.types.usize, expr_span);
134 this.cfg.push_assign(
138 Rvalue::NullaryOp(NullOp::AlignOf, value.ty),
141 // malloc some memory of suitable size and align:
142 let exchange_malloc = Operand::function_handle(
144 tcx.require_lang_item(LangItem::ExchangeMalloc, Some(expr_span)),
148 let storage = this.temp(tcx.mk_mut_ptr(tcx.types.u8), expr_span);
149 let success = this.cfg.start_new_block();
153 TerminatorKind::Call {
154 func: exchange_malloc,
155 args: vec![Operand::Move(size), Operand::Move(align)],
156 destination: storage,
157 target: Some(success),
159 from_hir_call: false,
163 this.diverge_from(block);
166 // The `Box<T>` temporary created here is not a part of the HIR,
167 // and therefore is not considered during generator auto-trait
168 // determination. See the comment about `box` at `yield_in_scope`.
169 let result = this.local_decls.push(LocalDecl::new(expr.ty, expr_span).internal());
172 Statement { source_info, kind: StatementKind::StorageLive(result) },
174 if let Some(scope) = scope {
175 // schedule a shallow free of that memory, lest we unwind:
176 this.schedule_drop_storage_and_value(expr_span, scope, result);
179 // Transmute `*mut u8` to the box (thus far, uninitialized):
180 let box_ = Rvalue::ShallowInitBox(Operand::Move(storage), value.ty);
181 this.cfg.push_assign(block, source_info, Place::from(result), box_);
183 // initialize the box contents:
185 block = this.expr_into_dest(
186 this.tcx.mk_place_deref(Place::from(result)),
191 block.and(Rvalue::Use(Operand::Move(Place::from(result))))
193 ExprKind::Cast { source } => {
194 let source = &this.thir[source];
196 // Casting an enum to an integer is equivalent to computing the discriminant and casting the
197 // discriminant. Previously every backend had to repeat the logic for this operation. Now we
198 // create all the steps directly in MIR with operations all backends need to support anyway.
199 let (source, ty) = if let ty::Adt(adt_def, ..) = source.ty.kind() && adt_def.is_enum() {
200 let discr_ty = adt_def.repr().discr_type().to_ty(this.tcx);
201 let temp = unpack!(block = this.as_temp(block, scope, source, Mutability::Not));
202 let layout = this.tcx.layout_of(this.param_env.and(source.ty));
203 let discr = this.temp(discr_ty, source.span);
204 this.cfg.push_assign(
208 Rvalue::Discriminant(temp.into()),
210 let (op,ty) = (Operand::Move(discr), discr_ty);
212 if let Abi::Scalar(scalar) = layout.unwrap().abi{
213 if let Primitive::Int(_, signed) = scalar.primitive() {
214 let range = scalar.valid_range(&this.tcx);
215 // FIXME: Handle wraparound cases too.
216 if range.end >= range.start {
217 let mut assumer = |range: u128, bin_op: BinOp| {
218 // We will be overwriting this val if our scalar is signed value
219 // because sign extension on unsigned types might cause unintended things
221 ConstantKind::from_bits(this.tcx, range, ty::ParamEnv::empty().and(discr_ty));
222 let bool_ty = this.tcx.types.bool;
224 let scalar_size_extend = scalar.size(&this.tcx).sign_extend(range);
225 let discr_layout = this.tcx.layout_of(this.param_env.and(discr_ty));
226 let truncated_val = discr_layout.unwrap().size.truncate(scalar_size_extend);
227 range_val = ConstantKind::from_bits(
230 ty::ParamEnv::empty().and(discr_ty),
233 let lit_op = this.literal_operand(expr.span, range_val);
234 let is_bin_op = this.temp(bool_ty, expr_span);
235 this.cfg.push_assign(
239 Rvalue::BinaryOp(bin_op, Box::new(((lit_op), (Operand::Copy(discr))))),
245 kind: StatementKind::Intrinsic(Box::new(NonDivergingIntrinsic::Assume(
246 Operand::Copy(is_bin_op),
251 assumer(range.end, BinOp::Ge);
252 assumer(range.start, BinOp::Le);
261 let source = unpack!(
262 block = this.as_operand(block, scope, source, None, NeedsTemporary::No)
266 let from_ty = CastTy::from_ty(ty);
267 let cast_ty = CastTy::from_ty(expr.ty);
268 debug!("ExprKind::Cast from_ty={from_ty:?}, cast_ty={:?}/{cast_ty:?}", expr.ty,);
269 let cast_kind = mir_cast_kind(ty, expr.ty);
270 block.and(Rvalue::Cast(cast_kind, source, expr.ty))
272 ExprKind::Pointer { cast, source } => {
273 let source = unpack!(
275 this.as_operand(block, scope, &this.thir[source], None, NeedsTemporary::No)
277 block.and(Rvalue::Cast(CastKind::Pointer(cast), source, expr.ty))
279 ExprKind::Array { ref fields } => {
280 // (*) We would (maybe) be closer to codegen if we
281 // handled this and other aggregate cases via
282 // `into()`, not `as_rvalue` -- in that case, instead
287 // dest = Rvalue::Aggregate(Foo, [tmp1, tmp2])
289 // we could just generate
294 // The problem is that then we would need to:
296 // (a) have a more complex mechanism for handling
298 // (b) distinguish the case where the type `Foo` has a
299 // destructor, in which case creating an instance
300 // as a whole "arms" the destructor, and you can't
301 // write individual fields; and,
302 // (c) handle the case where the type Foo has no
303 // fields. We don't want `let x: ();` to compile
304 // to the same MIR as `let x = ();`.
306 // first process the set of fields
307 let el_ty = expr.ty.sequence_element_type(this.tcx);
308 let fields: Vec<_> = fields
313 block = this.as_operand(
318 NeedsTemporary::Maybe
324 block.and(Rvalue::Aggregate(Box::new(AggregateKind::Array(el_ty)), fields))
326 ExprKind::Tuple { ref fields } => {
328 // first process the set of fields
329 let fields: Vec<_> = fields
334 block = this.as_operand(
339 NeedsTemporary::Maybe
345 block.and(Rvalue::Aggregate(Box::new(AggregateKind::Tuple), fields))
347 ExprKind::Closure(box ClosureExpr {
354 // Convert the closure fake reads, if any, from `ExprRef` to mir `Place`
355 // and push the fake reads.
356 // This must come before creating the operands. This is required in case
357 // there is a fake read and a borrow of the same path, since otherwise the
358 // fake read might interfere with the borrow. Consider an example like this
363 // &mut x; // mutable borrow of `x`
364 // match x { _ => () } // fake read of `x`
368 for (thir_place, cause, hir_id) in fake_reads.into_iter() {
370 unpack!(block = this.as_place_builder(block, &this.thir[*thir_place]));
372 if let Ok(place_builder_resolved) = place_builder.try_upvars_resolved(this) {
373 let mir_place = place_builder_resolved.into_place(this);
374 this.cfg.push_fake_read(
376 this.source_info(this.tcx.hir().span(*hir_id)),
384 let operands: Vec<_> = upvars
388 let upvar = &this.thir[upvar];
389 match Category::of(&upvar.kind) {
390 // Use as_place to avoid creating a temporary when
391 // moving a variable into a closure, so that
392 // borrowck knows which variables to mark as being
393 // used as mut. This is OK here because the upvar
394 // expressions have no side effects and act on
396 // This occurs when capturing by copy/move, while
397 // by reference captures use as_operand
398 Some(Category::Place) => {
399 let place = unpack!(block = this.as_place(block, upvar));
400 this.consume_by_copy_or_move(place)
403 // Turn mutable borrow captures into unique
404 // borrow captures when capturing an immutable
405 // variable. This is sound because the mutation
406 // that caused the capture will cause an error.
410 BorrowKind::Mut { allow_two_phase_borrow: false },
413 block = this.limit_capture_mutability(
423 block = this.as_operand(
428 NeedsTemporary::Maybe
438 let result = match substs {
439 UpvarSubsts::Generator(substs) => {
440 // We implicitly set the discriminant to 0. See
441 // librustc_mir/transform/deaggregator.rs for details.
442 let movability = movability.unwrap();
443 Box::new(AggregateKind::Generator(closure_id, substs, movability))
445 UpvarSubsts::Closure(substs) => {
446 Box::new(AggregateKind::Closure(closure_id, substs))
449 block.and(Rvalue::Aggregate(result, operands))
451 ExprKind::Assign { .. } | ExprKind::AssignOp { .. } => {
452 block = unpack!(this.stmt_expr(block, expr, None));
453 block.and(Rvalue::Use(Operand::Constant(Box::new(Constant {
456 literal: ConstantKind::zero_sized(this.tcx.types.unit),
460 ExprKind::Literal { .. }
461 | ExprKind::NamedConst { .. }
462 | ExprKind::NonHirLiteral { .. }
463 | ExprKind::ZstLiteral { .. }
464 | ExprKind::ConstParam { .. }
465 | ExprKind::ConstBlock { .. }
466 | ExprKind::StaticRef { .. } => {
467 let constant = this.as_constant(expr);
468 block.and(Rvalue::Use(Operand::Constant(Box::new(constant))))
471 ExprKind::Yield { .. }
472 | ExprKind::Block { .. }
473 | ExprKind::Match { .. }
474 | ExprKind::If { .. }
475 | ExprKind::NeverToAny { .. }
476 | ExprKind::Use { .. }
477 | ExprKind::Borrow { .. }
478 | ExprKind::AddressOf { .. }
479 | ExprKind::Adt { .. }
480 | ExprKind::Loop { .. }
481 | ExprKind::LogicalOp { .. }
482 | ExprKind::Call { .. }
483 | ExprKind::Field { .. }
484 | ExprKind::Let { .. }
485 | ExprKind::Deref { .. }
486 | ExprKind::Index { .. }
487 | ExprKind::VarRef { .. }
488 | ExprKind::UpvarRef { .. }
489 | ExprKind::Break { .. }
490 | ExprKind::Continue { .. }
491 | ExprKind::Return { .. }
492 | ExprKind::InlineAsm { .. }
493 | ExprKind::PlaceTypeAscription { .. }
494 | ExprKind::ValueTypeAscription { .. } => {
495 // these do not have corresponding `Rvalue` variants,
496 // so make an operand and then return that
497 debug_assert!(!matches!(
498 Category::of(&expr.kind),
499 Some(Category::Rvalue(RvalueFunc::AsRvalue) | Category::Constant)
502 unpack!(block = this.as_operand(block, scope, expr, None, NeedsTemporary::No));
503 block.and(Rvalue::Use(operand))
508 pub(crate) fn build_binary_op(
510 mut block: BasicBlock,
516 ) -> BlockAnd<Rvalue<'tcx>> {
517 let source_info = self.source_info(span);
518 let bool_ty = self.tcx.types.bool;
519 if self.check_overflow && op.is_checkable() && ty.is_integral() {
520 let result_tup = self.tcx.intern_tup(&[ty, bool_ty]);
521 let result_value = self.temp(result_tup, span);
523 self.cfg.push_assign(
527 Rvalue::CheckedBinaryOp(op, Box::new((lhs.to_copy(), rhs.to_copy()))),
529 let val_fld = Field::new(0);
530 let of_fld = Field::new(1);
533 let val = tcx.mk_place_field(result_value, val_fld, ty);
534 let of = tcx.mk_place_field(result_value, of_fld, bool_ty);
536 let err = AssertKind::Overflow(op, lhs, rhs);
538 block = self.assert(block, Operand::Move(of), false, err, span);
540 block.and(Rvalue::Use(Operand::Move(val)))
542 if ty.is_integral() && (op == BinOp::Div || op == BinOp::Rem) {
543 // Checking division and remainder is more complex, since we 1. always check
544 // and 2. there are two possible failure cases, divide-by-zero and overflow.
546 let zero_err = if op == BinOp::Div {
547 AssertKind::DivisionByZero(lhs.to_copy())
549 AssertKind::RemainderByZero(lhs.to_copy())
551 let overflow_err = AssertKind::Overflow(op, lhs.to_copy(), rhs.to_copy());
554 let is_zero = self.temp(bool_ty, span);
555 let zero = self.zero_literal(span, ty);
556 self.cfg.push_assign(
560 Rvalue::BinaryOp(BinOp::Eq, Box::new((rhs.to_copy(), zero))),
563 block = self.assert(block, Operand::Move(is_zero), false, zero_err, span);
565 // We only need to check for the overflow in one case:
566 // MIN / -1, and only for signed values.
568 let neg_1 = self.neg_1_literal(span, ty);
569 let min = self.minval_literal(span, ty);
571 let is_neg_1 = self.temp(bool_ty, span);
572 let is_min = self.temp(bool_ty, span);
573 let of = self.temp(bool_ty, span);
575 // this does (rhs == -1) & (lhs == MIN). It could short-circuit instead
577 self.cfg.push_assign(
581 Rvalue::BinaryOp(BinOp::Eq, Box::new((rhs.to_copy(), neg_1))),
583 self.cfg.push_assign(
587 Rvalue::BinaryOp(BinOp::Eq, Box::new((lhs.to_copy(), min))),
590 let is_neg_1 = Operand::Move(is_neg_1);
591 let is_min = Operand::Move(is_min);
592 self.cfg.push_assign(
596 Rvalue::BinaryOp(BinOp::BitAnd, Box::new((is_neg_1, is_min))),
599 block = self.assert(block, Operand::Move(of), false, overflow_err, span);
603 block.and(Rvalue::BinaryOp(op, Box::new((lhs, rhs))))
607 fn build_zero_repeat(
609 mut block: BasicBlock,
611 scope: Option<region::Scope>,
612 outer_source_info: SourceInfo,
613 ) -> BlockAnd<Rvalue<'tcx>> {
615 let value = &this.thir[value];
616 let elem_ty = value.ty;
617 if let Some(Category::Constant) = Category::of(&value.kind) {
618 // Repeating a const does nothing
620 // For a non-const, we may need to generate an appropriate `Drop`
622 unpack!(block = this.as_operand(block, scope, value, None, NeedsTemporary::No));
623 if let Operand::Move(to_drop) = value_operand {
624 let success = this.cfg.start_new_block();
628 TerminatorKind::Drop { place: to_drop, target: success, unwind: None },
630 this.diverge_from(block);
633 this.record_operands_moved(&[value_operand]);
635 block.and(Rvalue::Aggregate(Box::new(AggregateKind::Array(elem_ty)), Vec::new()))
638 fn limit_capture_mutability(
642 temp_lifetime: Option<region::Scope>,
643 mut block: BasicBlock,
645 ) -> BlockAnd<Operand<'tcx>> {
648 let source_info = this.source_info(upvar_span);
649 let temp = this.local_decls.push(LocalDecl::new(upvar_ty, upvar_span));
651 this.cfg.push(block, Statement { source_info, kind: StatementKind::StorageLive(temp) });
653 let arg_place_builder = unpack!(block = this.as_place_builder(block, arg));
655 let mutability = match arg_place_builder.base() {
656 // We are capturing a path that starts off a local variable in the parent.
657 // The mutability of the current capture is same as the mutability
658 // of the local declaration in the parent.
659 PlaceBase::Local(local) => this.local_decls[local].mutability,
660 // Parent is a closure and we are capturing a path that is captured
661 // by the parent itself. The mutability of the current capture
662 // is same as that of the capture in the parent closure.
663 PlaceBase::Upvar { .. } => {
664 let enclosing_upvars_resolved = arg_place_builder.clone().into_place(this);
666 match enclosing_upvars_resolved.as_ref() {
669 projection: &[ProjectionElem::Field(upvar_index, _), ..],
674 &[ProjectionElem::Deref, ProjectionElem::Field(upvar_index, _), ..],
678 local == ty::CAPTURE_STRUCT_LOCAL,
679 "Expected local to be Local(1), found {:?}",
684 this.upvars.len() > upvar_index.index(),
685 "Unexpected capture place, upvars={:#?}, upvar_index={:?}",
689 this.upvars[upvar_index.index()].mutability
691 _ => bug!("Unexpected capture place"),
696 let borrow_kind = match mutability {
697 Mutability::Not => BorrowKind::Unique,
698 Mutability::Mut => BorrowKind::Mut { allow_two_phase_borrow: false },
701 let arg_place = arg_place_builder.into_place(this);
703 this.cfg.push_assign(
707 Rvalue::Ref(this.tcx.lifetimes.re_erased, borrow_kind, arg_place),
710 // See the comment in `expr_as_temp` and on the `rvalue_scopes` field for why
711 // this can be `None`.
712 if let Some(temp_lifetime) = temp_lifetime {
713 this.schedule_drop_storage_and_value(upvar_span, temp_lifetime, temp);
716 block.and(Operand::Move(Place::from(temp)))
719 // Helper to get a `-1` value of the appropriate type
720 fn neg_1_literal(&mut self, span: Span, ty: Ty<'tcx>) -> Operand<'tcx> {
721 let param_ty = ty::ParamEnv::empty().and(ty);
722 let size = self.tcx.layout_of(param_ty).unwrap().size;
723 let literal = ConstantKind::from_bits(self.tcx, size.unsigned_int_max(), param_ty);
725 self.literal_operand(span, literal)
728 // Helper to get the minimum value of the appropriate type
729 fn minval_literal(&mut self, span: Span, ty: Ty<'tcx>) -> Operand<'tcx> {
730 assert!(ty.is_signed());
731 let param_ty = ty::ParamEnv::empty().and(ty);
732 let bits = self.tcx.layout_of(param_ty).unwrap().size.bits();
733 let n = 1 << (bits - 1);
734 let literal = ConstantKind::from_bits(self.tcx, n, param_ty);
736 self.literal_operand(span, literal)