1 //! See docs in `build/expr/mod.rs`.
3 use rustc_index
::vec
::Idx
;
5 use crate::build
::expr
::category
::{Category, RvalueFunc}
;
6 use crate::build
::{BlockAnd, BlockAndExtension, Builder}
;
8 use rustc
::middle
::region
;
9 use rustc
::mir
::interpret
::PanicInfo
;
11 use rustc
::ty
::{self, Ty, UpvarSubsts}
;
14 impl<'a
, 'tcx
> Builder
<'a
, 'tcx
> {
15 /// Returns an rvalue suitable for use until the end of the current
18 /// The operand returned from this function will *not be valid* after
19 /// an ExprKind::Scope is passed, so please do *not* return it from
20 /// functions to avoid bad miscompiles.
21 crate fn as_local_rvalue
<M
>(&mut self, block
: BasicBlock
, expr
: M
) -> BlockAnd
<Rvalue
<'tcx
>>
23 M
: Mirror
<'tcx
, Output
= Expr
<'tcx
>>,
25 let local_scope
= self.local_scope();
26 self.as_rvalue(block
, local_scope
, expr
)
29 /// Compile `expr`, yielding an rvalue.
33 scope
: Option
<region
::Scope
>,
35 ) -> BlockAnd
<Rvalue
<'tcx
>>
37 M
: Mirror
<'tcx
, Output
= Expr
<'tcx
>>,
39 let expr
= self.hir
.mirror(expr
);
40 self.expr_as_rvalue(block
, scope
, expr
)
45 mut block
: BasicBlock
,
46 scope
: Option
<region
::Scope
>,
48 ) -> BlockAnd
<Rvalue
<'tcx
>> {
49 debug
!("expr_as_rvalue(block={:?}, scope={:?}, expr={:?})", block
, scope
, expr
);
52 let expr_span
= expr
.span
;
53 let source_info
= this
.source_info(expr_span
);
56 ExprKind
::Scope { region_scope, lint_level, value }
=> {
57 let region_scope
= (region_scope
, source_info
);
58 this
.in_scope(region_scope
, lint_level
, |this
| this
.as_rvalue(block
, scope
, value
))
60 ExprKind
::Repeat { value, count }
=> {
61 let value_operand
= unpack
!(block
= this
.as_operand(block
, scope
, value
));
62 block
.and(Rvalue
::Repeat(value_operand
, count
))
64 ExprKind
::Binary { op, lhs, rhs }
=> {
65 let lhs
= unpack
!(block
= this
.as_operand(block
, scope
, lhs
));
66 let rhs
= unpack
!(block
= this
.as_operand(block
, scope
, rhs
));
67 this
.build_binary_op(block
, op
, expr_span
, expr
.ty
, lhs
, rhs
)
69 ExprKind
::Unary { op, arg }
=> {
70 let arg
= unpack
!(block
= this
.as_operand(block
, scope
, arg
));
71 // Check for -MIN on signed integers
72 if this
.hir
.check_overflow() && op
== UnOp
::Neg
&& expr
.ty
.is_signed() {
73 let bool_ty
= this
.hir
.bool_ty();
75 let minval
= this
.minval_literal(expr_span
, expr
.ty
);
76 let is_min
= this
.temp(bool_ty
, expr_span
);
82 Rvalue
::BinaryOp(BinOp
::Eq
, arg
.to_copy(), minval
),
87 Operand
::Move(is_min
),
89 PanicInfo
::OverflowNeg
,
93 block
.and(Rvalue
::UnaryOp(op
, arg
))
95 ExprKind
::Box { value }
=> {
96 let value
= this
.hir
.mirror(value
);
97 // The `Box<T>` temporary created here is not a part of the HIR,
98 // and therefore is not considered during generator OIBIT
99 // determination. See the comment about `box` at `yield_in_scope`.
100 let result
= this
.local_decls
.push(LocalDecl
::new_internal(expr
.ty
, expr_span
));
103 Statement { source_info, kind: StatementKind::StorageLive(result) }
,
105 if let Some(scope
) = scope
{
106 // schedule a shallow free of that memory, lest we unwind:
107 this
.schedule_drop_storage_and_value(expr_span
, scope
, result
);
110 // malloc some memory of suitable type (thus far, uninitialized):
111 let box_
= Rvalue
::NullaryOp(NullOp
::Box
, value
.ty
);
112 this
.cfg
.push_assign(block
, source_info
, &Place
::from(result
), box_
);
114 // initialize the box contents:
117 &this
.hir
.tcx().mk_place_deref(Place
::from(result
)),
122 block
.and(Rvalue
::Use(Operand
::Move(Place
::from(result
))))
124 ExprKind
::Cast { source }
=> {
125 let source
= unpack
!(block
= this
.as_operand(block
, scope
, source
));
126 block
.and(Rvalue
::Cast(CastKind
::Misc
, source
, expr
.ty
))
128 ExprKind
::Pointer { cast, source }
=> {
129 let source
= unpack
!(block
= this
.as_operand(block
, scope
, source
));
130 block
.and(Rvalue
::Cast(CastKind
::Pointer(cast
), source
, expr
.ty
))
132 ExprKind
::Array { fields }
=> {
133 // (*) We would (maybe) be closer to codegen if we
134 // handled this and other aggregate cases via
135 // `into()`, not `as_rvalue` -- in that case, instead
140 // dest = Rvalue::Aggregate(Foo, [tmp1, tmp2])
142 // we could just generate
147 // The problem is that then we would need to:
149 // (a) have a more complex mechanism for handling
151 // (b) distinguish the case where the type `Foo` has a
152 // destructor, in which case creating an instance
153 // as a whole "arms" the destructor, and you can't
154 // write individual fields; and,
155 // (c) handle the case where the type Foo has no
156 // fields. We don't want `let x: ();` to compile
157 // to the same MIR as `let x = ();`.
159 // first process the set of fields
160 let el_ty
= expr
.ty
.sequence_element_type(this
.hir
.tcx());
161 let fields
: Vec
<_
> = fields
163 .map(|f
| unpack
!(block
= this
.as_operand(block
, scope
, f
)))
166 block
.and(Rvalue
::Aggregate(box AggregateKind
::Array(el_ty
), fields
))
168 ExprKind
::Tuple { fields }
=> {
170 // first process the set of fields
171 let fields
: Vec
<_
> = fields
173 .map(|f
| unpack
!(block
= this
.as_operand(block
, scope
, f
)))
176 block
.and(Rvalue
::Aggregate(box AggregateKind
::Tuple
, fields
))
178 ExprKind
::Closure { closure_id, substs, upvars, movability }
=> {
180 let operands
: Vec
<_
> = upvars
183 let upvar
= this
.hir
.mirror(upvar
);
184 match Category
::of(&upvar
.kind
) {
185 // Use as_place to avoid creating a temporary when
186 // moving a variable into a closure, so that
187 // borrowck knows which variables to mark as being
188 // used as mut. This is OK here because the upvar
189 // expressions have no side effects and act on
191 // This occurs when capturing by copy/move, while
192 // by reference captures use as_operand
193 Some(Category
::Place
) => {
194 let place
= unpack
!(block
= this
.as_place(block
, upvar
));
195 this
.consume_by_copy_or_move(place
)
198 // Turn mutable borrow captures into unique
199 // borrow captures when capturing an immutable
200 // variable. This is sound because the mutation
201 // that caused the capture will cause an error.
205 BorrowKind
::Mut { allow_two_phase_borrow: false }
,
208 block
= this
.limit_capture_mutability(
209 upvar
.span
, upvar
.ty
, scope
, block
, arg
,
212 _
=> unpack
!(block
= this
.as_operand(block
, scope
, upvar
)),
218 let result
= match substs
{
219 UpvarSubsts
::Generator(substs
) => {
220 // We implicitly set the discriminant to 0. See
221 // librustc_mir/transform/deaggregator.rs for details.
222 let movability
= movability
.unwrap();
223 box AggregateKind
::Generator(closure_id
, substs
, movability
)
225 UpvarSubsts
::Closure(substs
) => box AggregateKind
::Closure(closure_id
, substs
),
227 block
.and(Rvalue
::Aggregate(result
, operands
))
229 ExprKind
::Assign { .. }
| ExprKind
::AssignOp { .. }
=> {
230 block
= unpack
!(this
.stmt_expr(block
, expr
, None
));
231 block
.and(this
.unit_rvalue())
233 ExprKind
::Yield { value }
=> {
234 let value
= unpack
!(block
= this
.as_operand(block
, scope
, value
));
235 let resume
= this
.cfg
.start_new_block();
236 let cleanup
= this
.generator_drop_cleanup();
240 TerminatorKind
::Yield { value: value, resume: resume, drop: cleanup }
,
242 resume
.and(this
.unit_rvalue())
244 ExprKind
::Literal { .. }
245 | ExprKind
::StaticRef { .. }
246 | ExprKind
::Block { .. }
247 | ExprKind
::Match { .. }
248 | ExprKind
::NeverToAny { .. }
249 | ExprKind
::Use { .. }
250 | ExprKind
::Borrow { .. }
251 | ExprKind
::AddressOf { .. }
252 | ExprKind
::Adt { .. }
253 | ExprKind
::Loop { .. }
254 | ExprKind
::LogicalOp { .. }
255 | ExprKind
::Call { .. }
256 | ExprKind
::Field { .. }
257 | ExprKind
::Deref { .. }
258 | ExprKind
::Index { .. }
259 | ExprKind
::VarRef { .. }
261 | ExprKind
::Break { .. }
262 | ExprKind
::Continue { .. }
263 | ExprKind
::Return { .. }
264 | ExprKind
::InlineAsm { .. }
265 | ExprKind
::PlaceTypeAscription { .. }
266 | ExprKind
::ValueTypeAscription { .. }
=> {
267 // these do not have corresponding `Rvalue` variants,
268 // so make an operand and then return that
269 debug_assert
!(match Category
::of(&expr
.kind
) {
270 Some(Category
::Rvalue(RvalueFunc
::AsRvalue
)) => false,
273 let operand
= unpack
!(block
= this
.as_operand(block
, scope
, expr
));
274 block
.and(Rvalue
::Use(operand
))
279 crate fn build_binary_op(
281 mut block
: BasicBlock
,
287 ) -> BlockAnd
<Rvalue
<'tcx
>> {
288 let source_info
= self.source_info(span
);
289 let bool_ty
= self.hir
.bool_ty();
290 if self.hir
.check_overflow() && op
.is_checkable() && ty
.is_integral() {
291 let result_tup
= self.hir
.tcx().intern_tup(&[ty
, bool_ty
]);
292 let result_value
= self.temp(result_tup
, span
);
294 self.cfg
.push_assign(
298 Rvalue
::CheckedBinaryOp(op
, lhs
, rhs
),
300 let val_fld
= Field
::new(0);
301 let of_fld
= Field
::new(1);
303 let tcx
= self.hir
.tcx();
304 let val
= tcx
.mk_place_field(result_value
.clone(), val_fld
, ty
);
305 let of
= tcx
.mk_place_field(result_value
, of_fld
, bool_ty
);
307 let err
= PanicInfo
::Overflow(op
);
309 block
= self.assert(block
, Operand
::Move(of
), false, err
, span
);
311 block
.and(Rvalue
::Use(Operand
::Move(val
)))
313 if ty
.is_integral() && (op
== BinOp
::Div
|| op
== BinOp
::Rem
) {
314 // Checking division and remainder is more complex, since we 1. always check
315 // and 2. there are two possible failure cases, divide-by-zero and overflow.
317 let zero_err
= if op
== BinOp
::Div
{
318 PanicInfo
::DivisionByZero
320 PanicInfo
::RemainderByZero
322 let overflow_err
= PanicInfo
::Overflow(op
);
325 let is_zero
= self.temp(bool_ty
, span
);
326 let zero
= self.zero_literal(span
, ty
);
327 self.cfg
.push_assign(
331 Rvalue
::BinaryOp(BinOp
::Eq
, rhs
.to_copy(), zero
),
334 block
= self.assert(block
, Operand
::Move(is_zero
), false, zero_err
, span
);
336 // We only need to check for the overflow in one case:
337 // MIN / -1, and only for signed values.
339 let neg_1
= self.neg_1_literal(span
, ty
);
340 let min
= self.minval_literal(span
, ty
);
342 let is_neg_1
= self.temp(bool_ty
, span
);
343 let is_min
= self.temp(bool_ty
, span
);
344 let of
= self.temp(bool_ty
, span
);
346 // this does (rhs == -1) & (lhs == MIN). It could short-circuit instead
348 self.cfg
.push_assign(
352 Rvalue
::BinaryOp(BinOp
::Eq
, rhs
.to_copy(), neg_1
),
354 self.cfg
.push_assign(
358 Rvalue
::BinaryOp(BinOp
::Eq
, lhs
.to_copy(), min
),
361 let is_neg_1
= Operand
::Move(is_neg_1
);
362 let is_min
= Operand
::Move(is_min
);
363 self.cfg
.push_assign(
367 Rvalue
::BinaryOp(BinOp
::BitAnd
, is_neg_1
, is_min
),
370 block
= self.assert(block
, Operand
::Move(of
), false, overflow_err
, span
);
374 block
.and(Rvalue
::BinaryOp(op
, lhs
, rhs
))
378 fn limit_capture_mutability(
382 temp_lifetime
: Option
<region
::Scope
>,
383 mut block
: BasicBlock
,
385 ) -> BlockAnd
<Operand
<'tcx
>> {
388 let source_info
= this
.source_info(upvar_span
);
389 let temp
= this
.local_decls
.push(LocalDecl
::new_temp(upvar_ty
, upvar_span
));
391 this
.cfg
.push(block
, Statement { source_info, kind: StatementKind::StorageLive(temp) }
);
393 let arg_place
= unpack
!(block
= this
.as_place(block
, arg
));
395 let mutability
= match arg_place
.as_ref() {
396 PlaceRef { local, projection: &[] }
=> this
.local_decls
[*local
].mutability
,
397 PlaceRef { local, projection: &[ProjectionElem::Deref] }
=> {
399 this
.local_decls
[*local
].is_ref_for_guard(),
400 "Unexpected capture place",
402 this
.local_decls
[*local
].mutability
406 projection
: &[ref proj_base @
.., ProjectionElem
::Field(upvar_index
, _
)],
411 &[ref proj_base @
.., ProjectionElem
::Field(upvar_index
, _
), ProjectionElem
::Deref
],
413 let place
= PlaceRef { local, projection: proj_base }
;
415 // Not projected from the implicit `self` in a closure.
417 match place
.local_or_deref_local() {
418 Some(local
) => local
== Local
::new(1),
421 "Unexpected capture place"
425 this
.upvar_mutbls
.len() > upvar_index
.index(),
426 "Unexpected capture place"
428 this
.upvar_mutbls
[upvar_index
.index()]
430 _
=> bug
!("Unexpected capture place"),
433 let borrow_kind
= match mutability
{
434 Mutability
::Not
=> BorrowKind
::Unique
,
435 Mutability
::Mut
=> BorrowKind
::Mut { allow_two_phase_borrow: false }
,
438 this
.cfg
.push_assign(
442 Rvalue
::Ref(this
.hir
.tcx().lifetimes
.re_erased
, borrow_kind
, arg_place
),
445 // In constants, temp_lifetime is None. We should not need to drop
446 // anything because no values with a destructor can be created in
447 // a constant at this time, even if the type may need dropping.
448 if let Some(temp_lifetime
) = temp_lifetime
{
449 this
.schedule_drop_storage_and_value(upvar_span
, temp_lifetime
, temp
);
452 block
.and(Operand
::Move(Place
::from(temp
)))
455 // Helper to get a `-1` value of the appropriate type
456 fn neg_1_literal(&mut self, span
: Span
, ty
: Ty
<'tcx
>) -> Operand
<'tcx
> {
457 let param_ty
= ty
::ParamEnv
::empty().and(ty
);
458 let bits
= self.hir
.tcx().layout_of(param_ty
).unwrap().size
.bits();
459 let n
= (!0u128) >> (128 - bits
);
460 let literal
= ty
::Const
::from_bits(self.hir
.tcx(), n
, param_ty
);
462 self.literal_operand(span
, literal
)
465 // Helper to get the minimum value of the appropriate type
466 fn minval_literal(&mut self, span
: Span
, ty
: Ty
<'tcx
>) -> Operand
<'tcx
> {
467 assert
!(ty
.is_signed());
468 let param_ty
= ty
::ParamEnv
::empty().and(ty
);
469 let bits
= self.hir
.tcx().layout_of(param_ty
).unwrap().size
.bits();
470 let n
= 1 << (bits
- 1);
471 let literal
= ty
::Const
::from_bits(self.hir
.tcx(), n
, param_ty
);
473 self.literal_operand(span
, literal
)