charon_driver/translate/
translate_bodies.rs

1//! Translate functions from the rust compiler MIR to our internal representation.
2//! Our internal representation is very close to MIR, but is more convenient for
3//! us to handle, and easier to maintain - rustc's representation can evolve
4//! independently.
5
6use std::collections::HashMap;
7use std::collections::VecDeque;
8use std::mem;
9use std::ops::Deref;
10use std::ops::DerefMut;
11use std::panic;
12
13use super::translate_crate::*;
14use super::translate_ctx::*;
15use charon_lib::ast::*;
16use charon_lib::formatter::FmtCtx;
17use charon_lib::formatter::IntoFormatter;
18use charon_lib::ids::Vector;
19use charon_lib::pretty::FmtWithCtx;
20use charon_lib::ullbc_ast::*;
21use hax_frontend_exporter as hax;
22use hax_frontend_exporter::UnwindAction;
23use itertools::Itertools;
24use rustc_middle::mir;
25
26/// A translation context for function bodies.
27pub(crate) struct BodyTransCtx<'tcx, 'tctx, 'ictx> {
28    /// The translation context for the item.
29    pub i_ctx: &'ictx mut ItemTransCtx<'tcx, 'tctx>,
30
31    /// The (regular) variables in the current function body.
32    pub locals: Locals,
33    /// The map from rust variable indices to translated variables indices.
34    pub locals_map: HashMap<usize, LocalId>,
35    /// The translated blocks.
36    pub blocks: Vector<BlockId, BlockData>,
37    /// The map from rust blocks to translated blocks.
38    /// Note that when translating terminators like DropAndReplace, we might have
39    /// to introduce new blocks which don't appear in the original MIR.
40    pub blocks_map: HashMap<hax::BasicBlock, BlockId>,
41    /// We register the blocks to translate in a stack, so as to avoid
42    /// writing the translation functions as recursive functions. We do
43    /// so because we had stack overflows in the past.
44    pub blocks_stack: VecDeque<hax::BasicBlock>,
45}
46
47impl<'tcx, 'tctx, 'ictx> BodyTransCtx<'tcx, 'tctx, 'ictx> {
48    pub(crate) fn new(i_ctx: &'ictx mut ItemTransCtx<'tcx, 'tctx>) -> Self {
49        BodyTransCtx {
50            i_ctx,
51            locals: Default::default(),
52            locals_map: Default::default(),
53            blocks: Default::default(),
54            blocks_map: Default::default(),
55            blocks_stack: Default::default(),
56        }
57    }
58}
59
60impl<'tcx, 'tctx, 'ictx> Deref for BodyTransCtx<'tcx, 'tctx, 'ictx> {
61    type Target = ItemTransCtx<'tcx, 'tctx>;
62    fn deref(&self) -> &Self::Target {
63        self.i_ctx
64    }
65}
66impl<'tcx, 'tctx, 'ictx> DerefMut for BodyTransCtx<'tcx, 'tctx, 'ictx> {
67    fn deref_mut(&mut self) -> &mut Self::Target {
68        self.i_ctx
69    }
70}
71
72fn translate_variant_id(id: hax::VariantIdx) -> VariantId {
73    VariantId::new(id)
74}
75
76fn translate_field_id(id: hax::FieldIdx) -> FieldId {
77    use rustc_index::Idx;
78    FieldId::new(id.index())
79}
80
81/// Translate a `BorrowKind`
82fn translate_borrow_kind(borrow_kind: hax::BorrowKind) -> BorrowKind {
83    match borrow_kind {
84        hax::BorrowKind::Shared => BorrowKind::Shared,
85        hax::BorrowKind::Mut { kind } => match kind {
86            hax::MutBorrowKind::Default => BorrowKind::Mut,
87            hax::MutBorrowKind::TwoPhaseBorrow => BorrowKind::TwoPhaseMut,
88            hax::MutBorrowKind::ClosureCapture => BorrowKind::UniqueImmutable,
89        },
90        hax::BorrowKind::Fake(hax::FakeBorrowKind::Shallow) => BorrowKind::Shallow,
91        // This one is used only in deref patterns.
92        hax::BorrowKind::Fake(hax::FakeBorrowKind::Deep) => unimplemented!(),
93    }
94}
95
96impl BodyTransCtx<'_, '_, '_> {
97    pub(crate) fn translate_local(&self, local: &hax::Local) -> Option<LocalId> {
98        use rustc_index::Idx;
99        self.locals_map.get(&local.index()).copied()
100    }
101
102    pub(crate) fn push_var(&mut self, rid: usize, ty: Ty, name: Option<String>) {
103        let local_id = self
104            .locals
105            .locals
106            .push_with(|index| Local { index, name, ty });
107        self.locals_map.insert(rid, local_id);
108    }
109
110    fn translate_binaryop_kind(&mut self, _span: Span, binop: hax::BinOp) -> Result<BinOp, Error> {
111        Ok(match binop {
112            hax::BinOp::BitXor => BinOp::BitXor,
113            hax::BinOp::BitAnd => BinOp::BitAnd,
114            hax::BinOp::BitOr => BinOp::BitOr,
115            hax::BinOp::Eq => BinOp::Eq,
116            hax::BinOp::Lt => BinOp::Lt,
117            hax::BinOp::Le => BinOp::Le,
118            hax::BinOp::Ne => BinOp::Ne,
119            hax::BinOp::Ge => BinOp::Ge,
120            hax::BinOp::Gt => BinOp::Gt,
121            hax::BinOp::Add => BinOp::Add(OverflowMode::Wrap),
122            hax::BinOp::AddUnchecked => BinOp::Add(OverflowMode::UB),
123            hax::BinOp::Sub => BinOp::Sub(OverflowMode::Wrap),
124            hax::BinOp::SubUnchecked => BinOp::Sub(OverflowMode::UB),
125            hax::BinOp::Mul => BinOp::Mul(OverflowMode::Wrap),
126            hax::BinOp::MulUnchecked => BinOp::Mul(OverflowMode::UB),
127            hax::BinOp::Div => BinOp::Div(OverflowMode::UB),
128            hax::BinOp::Rem => BinOp::Rem(OverflowMode::UB),
129            hax::BinOp::AddWithOverflow => BinOp::AddChecked,
130            hax::BinOp::SubWithOverflow => BinOp::SubChecked,
131            hax::BinOp::MulWithOverflow => BinOp::MulChecked,
132            hax::BinOp::Shl => BinOp::Shl(OverflowMode::Wrap),
133            hax::BinOp::ShlUnchecked => BinOp::Shl(OverflowMode::UB),
134            hax::BinOp::Shr => BinOp::Shr(OverflowMode::Wrap),
135            hax::BinOp::ShrUnchecked => BinOp::Shr(OverflowMode::UB),
136            hax::BinOp::Cmp => BinOp::Cmp,
137            hax::BinOp::Offset => BinOp::Offset,
138        })
139    }
140
141    /// Translate a function's local variables by adding them in the environment.
142    fn translate_body_locals(
143        &mut self,
144        body: &hax::MirBody<hax::mir_kinds::Unknown>,
145    ) -> Result<(), Error> {
146        // Translate the parameters
147        for (index, var) in body.local_decls.raw.iter().enumerate() {
148            trace!("Translating local of index {} and type {:?}", index, var.ty);
149
150            // Find the name of the variable
151            let name: Option<String> = var.name.clone();
152
153            // Translate the type
154            let span = self.translate_span_from_hax(&var.source_info.span);
155            let ty = self.translate_ty(span, &var.ty)?;
156
157            // Add the variable to the environment
158            self.push_var(index, ty, name);
159        }
160
161        Ok(())
162    }
163
164    /// Translate a basic block id and register it, if it hasn't been done.
165    fn translate_basic_block_id(&mut self, block_id: hax::BasicBlock) -> BlockId {
166        match self.blocks_map.get(&block_id) {
167            Some(id) => *id,
168            // Generate a fresh id - this also registers the block
169            None => {
170                // Push to the stack of blocks awaiting translation
171                self.blocks_stack.push_back(block_id);
172                let id = self.blocks.reserve_slot();
173                // Insert in the map
174                self.blocks_map.insert(block_id, id);
175                id
176            }
177        }
178    }
179
180    fn translate_basic_block(
181        &mut self,
182        body: &hax::MirBody<hax::mir_kinds::Unknown>,
183        block: &hax::BasicBlockData,
184    ) -> Result<BlockData, Error> {
185        // Translate the statements
186        let mut statements = Vec::new();
187        for statement in &block.statements {
188            trace!("statement: {:?}", statement);
189
190            // Some statements might be ignored, hence the optional returned value
191            let opt_statement = self.translate_statement(body, statement)?;
192            if let Some(statement) = opt_statement {
193                statements.push(statement)
194            }
195        }
196
197        // Translate the terminator
198        let terminator = block.terminator.as_ref().unwrap();
199        let terminator = self.translate_terminator(body, terminator, &mut statements)?;
200
201        Ok(BlockData {
202            statements,
203            terminator,
204        })
205    }
206
207    /// Translate a place
208    /// TODO: Hax represents places in a different manner than MIR. We should
209    /// update our representation of places to match the Hax representation.
210    fn translate_place(&mut self, span: Span, place: &hax::Place) -> Result<Place, Error> {
211        match &place.kind {
212            hax::PlaceKind::Local(local) => {
213                let var_id = self.translate_local(local).unwrap();
214                Ok(self.locals.place_for_var(var_id))
215            }
216            hax::PlaceKind::Projection {
217                place: hax_subplace,
218                kind,
219            } => {
220                let ty = self.translate_ty(span, &place.ty)?;
221                // Compute the type of the value *before* projection - we use this
222                // to disambiguate
223                let subplace = self.translate_place(span, hax_subplace)?;
224                let place = match kind {
225                    hax::ProjectionElem::Deref => subplace.project(ProjectionElem::Deref, ty),
226                    hax::ProjectionElem::Field(field_kind) => {
227                        use hax::ProjectionElemFieldKind::*;
228                        let proj_elem = match field_kind {
229                            Tuple(id) => {
230                                let tref = subplace.ty().kind().as_adt().unwrap();
231                                let field_id = translate_field_id(*id);
232                                let proj_kind =
233                                    FieldProjKind::Tuple(tref.generics.types.elem_count());
234                                ProjectionElem::Field(proj_kind, field_id)
235                            }
236                            Adt {
237                                typ: _,
238                                variant,
239                                index,
240                            } => {
241                                let field_id = translate_field_id(*index);
242                                let variant_id = variant.map(translate_variant_id);
243                                let tref = subplace.ty().kind().as_adt().unwrap();
244                                let generics = &tref.generics;
245                                match tref.id {
246                                    TypeId::Adt(type_id) => {
247                                        let proj_kind = FieldProjKind::Adt(type_id, variant_id);
248                                        ProjectionElem::Field(proj_kind, field_id)
249                                    }
250                                    TypeId::Tuple => {
251                                        assert!(generics.regions.is_empty());
252                                        assert!(variant.is_none());
253                                        assert!(generics.const_generics.is_empty());
254                                        let proj_kind =
255                                            FieldProjKind::Tuple(generics.types.elem_count());
256                                        ProjectionElem::Field(proj_kind, field_id)
257                                    }
258                                    TypeId::Builtin(BuiltinTy::Box) => {
259                                        // Some sanity checks
260                                        assert!(generics.regions.is_empty());
261                                        assert!(generics.types.elem_count() == 2);
262                                        assert!(generics.const_generics.is_empty());
263                                        assert!(field_id == FieldId::ZERO);
264                                        // We pretend this is a deref.
265                                        ProjectionElem::Deref
266                                    }
267                                    _ => raise_error!(self, span, "Unexpected field projection"),
268                                }
269                            }
270                            ClosureState(index) => {
271                                let field_id = translate_field_id(*index);
272                                let type_id = *subplace
273                                    .ty
274                                    .kind()
275                                    .as_adt()
276                                    .expect("ClosureState projection should apply to an Adt type")
277                                    .id
278                                    .as_adt()
279                                    .unwrap();
280                                ProjectionElem::Field(FieldProjKind::Adt(type_id, None), field_id)
281                            }
282                        };
283                        subplace.project(proj_elem, ty)
284                    }
285                    hax::ProjectionElem::Index(local) => {
286                        let var_id = self.translate_local(local).unwrap();
287                        let local = self.locals.place_for_var(var_id);
288                        let offset = Operand::Copy(local);
289                        subplace.project(
290                            ProjectionElem::Index {
291                                offset: Box::new(offset),
292                                from_end: false,
293                            },
294                            ty,
295                        )
296                    }
297                    hax::ProjectionElem::Downcast(..) => {
298                        // We view it as a nop (the information from the
299                        // downcast has been propagated to the other
300                        // projection elements by Hax)
301                        subplace
302                    }
303                    &hax::ProjectionElem::ConstantIndex {
304                        offset,
305                        from_end,
306                        min_length: _,
307                    } => {
308                        let offset =
309                            Operand::Const(Box::new(ScalarValue::Usize(offset).to_constant()));
310                        subplace.project(
311                            ProjectionElem::Index {
312                                offset: Box::new(offset),
313                                from_end,
314                            },
315                            ty,
316                        )
317                    }
318                    &hax::ProjectionElem::Subslice { from, to, from_end } => {
319                        let from = Operand::Const(Box::new(ScalarValue::Usize(from).to_constant()));
320                        let to = Operand::Const(Box::new(ScalarValue::Usize(to).to_constant()));
321                        subplace.project(
322                            ProjectionElem::Subslice {
323                                from: Box::new(from),
324                                to: Box::new(to),
325                                from_end,
326                            },
327                            ty,
328                        )
329                    }
330                    hax::ProjectionElem::OpaqueCast => {
331                        // Don't know what that is
332                        raise_error!(self, span, "Unexpected ProjectionElem::OpaqueCast");
333                    }
334                };
335
336                // Return
337                Ok(place)
338            }
339        }
340    }
341
342    /// Translate an operand with its type
343    fn translate_operand_with_type(
344        &mut self,
345        span: Span,
346        operand: &hax::Operand,
347    ) -> Result<(Operand, Ty), Error> {
348        trace!();
349        match operand {
350            hax::Operand::Copy(place) => {
351                let p = self.translate_place(span, place)?;
352                let ty = p.ty().clone();
353                Ok((Operand::Copy(p), ty))
354            }
355            hax::Operand::Move(place) => {
356                let p = self.translate_place(span, place)?;
357                let ty = p.ty().clone();
358                Ok((Operand::Move(p), ty))
359            }
360            hax::Operand::Constant(const_op) => match &const_op.kind {
361                hax::ConstOperandKind::Value(constant) => {
362                    let constant = self.translate_constant_expr_to_constant_expr(span, constant)?;
363                    let ty = constant.ty.clone();
364                    Ok((Operand::Const(Box::new(constant)), ty))
365                }
366                hax::ConstOperandKind::Promoted(item) => {
367                    let ty = self.translate_ty(span, &const_op.ty)?;
368                    // A promoted constant that could not be evaluated.
369                    let global_ref = self.translate_global_decl_ref(span, item)?;
370                    let constant = ConstantExpr {
371                        value: RawConstantExpr::Global(global_ref),
372                        ty: ty.clone(),
373                    };
374                    Ok((Operand::Const(Box::new(constant)), ty))
375                }
376            },
377        }
378    }
379
380    /// Translate an operand
381    fn translate_operand(&mut self, span: Span, operand: &hax::Operand) -> Result<Operand, Error> {
382        trace!();
383        Ok(self.translate_operand_with_type(span, operand)?.0)
384    }
385
386    /// Translate an rvalue
387    fn translate_rvalue(&mut self, span: Span, rvalue: &hax::Rvalue) -> Result<Rvalue, Error> {
388        match rvalue {
389            hax::Rvalue::Use(operand) => Ok(Rvalue::Use(self.translate_operand(span, operand)?)),
390            hax::Rvalue::CopyForDeref(place) => {
391                // According to the documentation, it seems to be an optimisation
392                // for drop elaboration. We treat it as a regular copy.
393                let place = self.translate_place(span, place)?;
394                Ok(Rvalue::Use(Operand::Copy(place)))
395            }
396            hax::Rvalue::Repeat(operand, cnst) => {
397                let c = self.translate_constant_expr_to_const_generic(span, cnst)?;
398                let (operand, t) = self.translate_operand_with_type(span, operand)?;
399                // Remark: we could desugar this into a function call later.
400                Ok(Rvalue::Repeat(operand, t, c))
401            }
402            hax::Rvalue::Ref(_region, borrow_kind, place) => {
403                let place = self.translate_place(span, place)?;
404                let borrow_kind = translate_borrow_kind(*borrow_kind);
405                Ok(Rvalue::Ref(place, borrow_kind))
406            }
407            hax::Rvalue::RawPtr(mtbl, place) => {
408                let mtbl = match mtbl {
409                    hax::RawPtrKind::Mut => RefKind::Mut,
410                    hax::RawPtrKind::Const => RefKind::Shared,
411                    hax::RawPtrKind::FakeForPtrMetadata => RefKind::Shared,
412                };
413                let place = self.translate_place(span, place)?;
414                Ok(Rvalue::RawPtr(place, mtbl))
415            }
416            hax::Rvalue::Len(place) => {
417                let place = self.translate_place(span, place)?;
418                let ty = place.ty().clone();
419                let tref = ty.as_adt().unwrap();
420                let cg = match tref.id {
421                    TypeId::Builtin(BuiltinTy::Array) => {
422                        Some(tref.generics.const_generics[0].clone())
423                    }
424                    TypeId::Builtin(BuiltinTy::Slice) => None,
425                    _ => unreachable!(),
426                };
427                Ok(Rvalue::Len(place, ty, cg))
428            }
429            hax::Rvalue::Cast(cast_kind, hax_operand, tgt_ty) => {
430                trace!("Rvalue::Cast: {:?}", rvalue);
431                // Translate the target type
432                let tgt_ty = self.translate_ty(span, tgt_ty)?;
433
434                // Translate the operand
435                let (operand, src_ty) = self.translate_operand_with_type(span, hax_operand)?;
436
437                match cast_kind {
438                    hax::CastKind::IntToInt
439                    | hax::CastKind::IntToFloat
440                    | hax::CastKind::FloatToInt
441                    | hax::CastKind::FloatToFloat => {
442                        let tgt_ty = *tgt_ty.kind().as_literal().unwrap();
443                        let src_ty = *src_ty.kind().as_literal().unwrap();
444                        Ok(Rvalue::UnaryOp(
445                            UnOp::Cast(CastKind::Scalar(src_ty, tgt_ty)),
446                            operand,
447                        ))
448                    }
449                    hax::CastKind::PtrToPtr
450                    | hax::CastKind::PointerCoercion(hax::PointerCoercion::MutToConstPointer, ..)
451                    | hax::CastKind::PointerCoercion(hax::PointerCoercion::ArrayToPointer, ..)
452                    | hax::CastKind::PointerCoercion(hax::PointerCoercion::DynStar, ..)
453                    | hax::CastKind::FnPtrToPtr
454                    | hax::CastKind::PointerExposeProvenance
455                    | hax::CastKind::PointerWithExposedProvenance => Ok(Rvalue::UnaryOp(
456                        UnOp::Cast(CastKind::RawPtr(src_ty, tgt_ty)),
457                        operand,
458                    )),
459                    hax::CastKind::PointerCoercion(
460                        hax::PointerCoercion::ClosureFnPointer(_),
461                        ..,
462                    ) => {
463                        // We model casts of closures to function pointers by generating a new
464                        // function item without the closure's state, that calls the actual closure.
465                        let op_ty = match hax_operand {
466                            hax::Operand::Move(p) | hax::Operand::Copy(p) => p.ty.kind(),
467                            hax::Operand::Constant(c) => c.ty.kind(),
468                        };
469                        let hax::TyKind::Closure(closure) = op_ty else {
470                            unreachable!("Non-closure type in PointerCoercion::ClosureFnPointer");
471                        };
472                        let fn_ref = self.translate_stateless_closure_as_fn_ref(span, closure)?;
473                        let fn_ptr_bound = fn_ref.map(FunDeclRef::into);
474                        let fn_ptr: FnPtr = fn_ptr_bound.clone().erase();
475                        let src_ty = TyKind::FnDef(fn_ptr_bound).into_ty();
476                        let operand = Operand::Const(Box::new(ConstantExpr {
477                            value: RawConstantExpr::FnPtr(fn_ptr),
478                            ty: src_ty.clone(),
479                        }));
480                        Ok(Rvalue::UnaryOp(
481                            UnOp::Cast(CastKind::FnPtr(src_ty, tgt_ty)),
482                            operand,
483                        ))
484                    }
485                    hax::CastKind::PointerCoercion(
486                        hax::PointerCoercion::UnsafeFnPointer
487                        | hax::PointerCoercion::ReifyFnPointer,
488                        ..,
489                    ) => Ok(Rvalue::UnaryOp(
490                        UnOp::Cast(CastKind::FnPtr(src_ty, tgt_ty)),
491                        operand,
492                    )),
493                    hax::CastKind::Transmute => Ok(Rvalue::UnaryOp(
494                        UnOp::Cast(CastKind::Transmute(src_ty, tgt_ty)),
495                        operand,
496                    )),
497                    hax::CastKind::PointerCoercion(hax::PointerCoercion::Unsize, ..) => {
498                        let unop = if let (
499                            TyKind::Ref(_, deref!(TyKind::Adt(tref1)), kind1),
500                            TyKind::Ref(_, deref!(TyKind::Adt(tref2)), kind2),
501                        ) = (src_ty.kind(), tgt_ty.kind())
502                            && matches!(tref1.id, TypeId::Builtin(BuiltinTy::Array))
503                            && matches!(tref2.id, TypeId::Builtin(BuiltinTy::Slice))
504                        {
505                            // In MIR terminology, we go from &[T; l] to &[T] which means we
506                            // effectively "unsize" the type, as `l` no longer appears in the
507                            // destination type. At runtime, the converse happens: the length
508                            // materializes into the fat pointer.
509                            assert!(
510                                tref1.generics.types.elem_count() == 1
511                                    && tref1.generics.const_generics.elem_count() == 1
512                            );
513                            assert!(tref1.generics.types[0] == tref2.generics.types[0]);
514                            assert!(kind1 == kind2);
515                            UnOp::ArrayToSlice(
516                                *kind1,
517                                tref1.generics.types[0].clone(),
518                                tref1.generics.const_generics[0].clone(),
519                            )
520                        } else {
521                            UnOp::Cast(CastKind::Unsize(src_ty.clone(), tgt_ty.clone()))
522                        };
523                        Ok(Rvalue::UnaryOp(unop, operand))
524                    }
525                }
526            }
527            hax::Rvalue::BinaryOp(binop, (left, right)) => Ok(Rvalue::BinaryOp(
528                self.translate_binaryop_kind(span, *binop)?,
529                self.translate_operand(span, left)?,
530                self.translate_operand(span, right)?,
531            )),
532            hax::Rvalue::NullaryOp(nullop, ty) => {
533                trace!("NullOp: {:?}", nullop);
534                let ty = self.translate_ty(span, ty)?;
535                let op = match nullop {
536                    hax::NullOp::SizeOf => NullOp::SizeOf,
537                    hax::NullOp::AlignOf => NullOp::AlignOf,
538                    hax::NullOp::OffsetOf(fields) => NullOp::OffsetOf(
539                        fields
540                            .iter()
541                            .copied()
542                            .map(|(n, idx)| (n, translate_field_id(idx)))
543                            .collect(),
544                    ),
545                    hax::NullOp::UbChecks => NullOp::UbChecks,
546                    hax::NullOp::ContractChecks => {
547                        raise_error!(self, span, "charon does not support contracts");
548                    }
549                };
550                Ok(Rvalue::NullaryOp(op, ty))
551            }
552            hax::Rvalue::UnaryOp(unop, operand) => {
553                let unop = match unop {
554                    hax::UnOp::Not => UnOp::Not,
555                    hax::UnOp::Neg => UnOp::Neg(OverflowMode::Wrap),
556                    hax::UnOp::PtrMetadata => UnOp::PtrMetadata,
557                };
558                Ok(Rvalue::UnaryOp(
559                    unop,
560                    self.translate_operand(span, operand)?,
561                ))
562            }
563            hax::Rvalue::Discriminant(place) => {
564                let place = self.translate_place(span, place)?;
565                if let TyKind::Adt(tref) = place.ty().kind()
566                    && let TypeId::Adt(adt_id) = tref.id
567                {
568                    Ok(Rvalue::Discriminant(place, adt_id))
569                } else {
570                    raise_error!(
571                        self,
572                        span,
573                        "Unexpected scrutinee type for ReadDiscriminant: {}",
574                        place.ty().with_ctx(&self.into_fmt())
575                    )
576                }
577            }
578            hax::Rvalue::Aggregate(aggregate_kind, operands) => {
579                // It seems this instruction is not present in certain passes:
580                // for example, it seems it is not used in optimized MIR, where
581                // ADT initialization is split into several instructions, for
582                // instance:
583                // ```
584                // p = Pair { x:xv, y:yv };
585                // ```
586                // Might become:
587                // ```
588                // p.x = x;
589                // p.y = yv;
590                // ```
591
592                // First translate the operands
593                let operands_t: Vec<Operand> = operands
594                    .raw
595                    .iter()
596                    .map(|op| self.translate_operand(span, op))
597                    .try_collect()?;
598
599                match aggregate_kind {
600                    hax::AggregateKind::Array(ty) => {
601                        let t_ty = self.translate_ty(span, ty)?;
602                        let cg = ConstGeneric::Value(Literal::Scalar(ScalarValue::Usize(
603                            operands_t.len() as u64,
604                        )));
605                        Ok(Rvalue::Aggregate(
606                            AggregateKind::Array(t_ty, cg),
607                            operands_t,
608                        ))
609                    }
610                    hax::AggregateKind::Tuple => {
611                        let tref = TypeDeclRef::new(TypeId::Tuple, GenericArgs::empty());
612                        Ok(Rvalue::Aggregate(
613                            AggregateKind::Adt(tref, None, None),
614                            operands_t,
615                        ))
616                    }
617                    hax::AggregateKind::Adt(
618                        item,
619                        variant_idx,
620                        kind,
621                        _user_annotation,
622                        field_index,
623                    ) => {
624                        use hax::AdtKind;
625                        trace!("{:?}", rvalue);
626
627                        let tref = self.translate_type_decl_ref(span, item)?;
628                        let variant_id = match kind {
629                            AdtKind::Struct | AdtKind::Union => None,
630                            AdtKind::Enum => Some(translate_variant_id(*variant_idx)),
631                        };
632                        let field_id = match kind {
633                            AdtKind::Struct | AdtKind::Enum => None,
634                            AdtKind::Union => Some(translate_field_id(field_index.unwrap())),
635                        };
636
637                        let akind = AggregateKind::Adt(tref, variant_id, field_id);
638                        Ok(Rvalue::Aggregate(akind, operands_t))
639                    }
640                    hax::AggregateKind::Closure(closure_args) => {
641                        trace!(
642                            "Closure:\n\n- def_id: {:?}\n\n- sig:\n{:?}",
643                            closure_args.item.def_id,
644                            closure_args.fn_sig
645                        );
646                        let tref = self.translate_closure_type_ref(span, closure_args)?;
647                        let akind = AggregateKind::Adt(tref, None, None);
648                        Ok(Rvalue::Aggregate(akind, operands_t))
649                    }
650                    hax::AggregateKind::RawPtr(ty, is_mut) => {
651                        // TODO: replace with a call to `ptr::from_raw_parts`.
652                        let t_ty = self.translate_ty(span, ty)?;
653                        let mutability = if *is_mut {
654                            RefKind::Mut
655                        } else {
656                            RefKind::Shared
657                        };
658
659                        let akind = AggregateKind::RawPtr(t_ty, mutability);
660
661                        Ok(Rvalue::Aggregate(akind, operands_t))
662                    }
663                    hax::AggregateKind::Coroutine(..)
664                    | hax::AggregateKind::CoroutineClosure(..) => {
665                        raise_error!(self, span, "Coroutines are not supported");
666                    }
667                }
668            }
669            hax::Rvalue::ShallowInitBox(op, ty) => {
670                let op = self.translate_operand(span, op)?;
671                let ty = self.translate_ty(span, ty)?;
672                Ok(Rvalue::ShallowInitBox(op, ty))
673            }
674            hax::Rvalue::ThreadLocalRef(_) => {
675                raise_error!(
676                    self,
677                    span,
678                    "charon does not support thread local references"
679                );
680            }
681            hax::Rvalue::WrapUnsafeBinder { .. } => {
682                raise_error!(
683                    self,
684                    span,
685                    "charon does not support unsafe lifetime binders"
686                );
687            }
688        }
689    }
690
691    /// Translate a statement
692    ///
693    /// We return an option, because we ignore some statements (`Nop`, `StorageLive`...)
694    fn translate_statement(
695        &mut self,
696        body: &hax::MirBody<hax::mir_kinds::Unknown>,
697        statement: &hax::Statement,
698    ) -> Result<Option<Statement>, Error> {
699        trace!("About to translate statement (MIR) {:?}", statement);
700        let span = self
701            .t_ctx
702            .translate_span_from_source_info(&body.source_scopes, &statement.source_info);
703
704        use hax::StatementKind;
705        let t_statement: Option<RawStatement> = match &*statement.kind {
706            StatementKind::Assign((place, rvalue)) => {
707                let t_place = self.translate_place(span, place)?;
708                let t_rvalue = self.translate_rvalue(span, rvalue)?;
709                Some(RawStatement::Assign(t_place, t_rvalue))
710            }
711            StatementKind::SetDiscriminant {
712                place,
713                variant_index,
714            } => {
715                let t_place = self.translate_place(span, place)?;
716                let variant_id = translate_variant_id(*variant_index);
717                Some(RawStatement::SetDiscriminant(t_place, variant_id))
718            }
719            StatementKind::StorageLive(local) => {
720                let var_id = self.translate_local(local).unwrap();
721                Some(RawStatement::StorageLive(var_id))
722            }
723            StatementKind::StorageDead(local) => {
724                let var_id = self.translate_local(local).unwrap();
725                Some(RawStatement::StorageDead(var_id))
726            }
727            StatementKind::Deinit(place) => {
728                let t_place = self.translate_place(span, place)?;
729                Some(RawStatement::Deinit(t_place))
730            }
731            // This asserts the operand true on pain of UB. We treat it like a normal assertion.
732            StatementKind::Intrinsic(hax::NonDivergingIntrinsic::Assume(op)) => {
733                let op = self.translate_operand(span, op)?;
734                Some(RawStatement::Assert(Assert {
735                    cond: op,
736                    expected: true,
737                    on_failure: AbortKind::UndefinedBehavior,
738                }))
739            }
740            StatementKind::Intrinsic(hax::NonDivergingIntrinsic::CopyNonOverlapping(
741                hax::CopyNonOverlapping { src, dst, count },
742            )) => {
743                let src = self.translate_operand(span, src)?;
744                let dst = self.translate_operand(span, dst)?;
745                let count = self.translate_operand(span, count)?;
746                Some(RawStatement::CopyNonOverlapping(Box::new(
747                    CopyNonOverlapping { src, dst, count },
748                )))
749            }
750            // This is for the stacked borrows memory model.
751            StatementKind::Retag(_, _) => None,
752            // These two are only there to make borrow-checking accept less code, and are removed
753            // in later MIRs.
754            StatementKind::FakeRead(..) | StatementKind::PlaceMention(..) => None,
755            // There are user-provided type annotations with no semantic effect (since we get a
756            // fully-typechecked MIR (TODO: this isn't quite true with opaque types, we should
757            // really use promoted MIR)).
758            StatementKind::AscribeUserType(_, _) => None,
759            // Used for coverage instrumentation.
760            StatementKind::Coverage(_) => None,
761            // Used in the interpreter to check that const code doesn't run for too long or even
762            // indefinitely.
763            StatementKind::ConstEvalCounter => None,
764            // Semantically equivalent to `Nop`, used only for rustc lints.
765            StatementKind::BackwardIncompatibleDropHint { .. } => None,
766            StatementKind::Nop => None,
767        };
768
769        // Add the span information
770        Ok(t_statement.map(|kind| Statement::new(span, kind)))
771    }
772
773    /// Translate a terminator
774    fn translate_terminator(
775        &mut self,
776        body: &hax::MirBody<hax::mir_kinds::Unknown>,
777        terminator: &hax::Terminator,
778        statements: &mut Vec<Statement>,
779    ) -> Result<Terminator, Error> {
780        trace!("About to translate terminator (MIR) {:?}", terminator);
781        // Compute the span information beforehand (we might need it to introduce
782        // intermediate statements - we desugar some terminators)
783        let span = self
784            .t_ctx
785            .translate_span_from_source_info(&body.source_scopes, &terminator.source_info);
786
787        // Translate the terminator
788        use hax::TerminatorKind;
789        let t_terminator: RawTerminator = match &terminator.kind {
790            TerminatorKind::Goto { target } => {
791                let target = self.translate_basic_block_id(*target);
792                RawTerminator::Goto { target }
793            }
794            TerminatorKind::SwitchInt {
795                discr,
796                targets,
797                otherwise,
798                ..
799            } => {
800                // Translate the operand which gives the discriminant
801                let (discr, discr_ty) = self.translate_operand_with_type(span, discr)?;
802
803                // Translate the switch targets
804                let targets = self.translate_switch_targets(span, &discr_ty, targets, otherwise)?;
805
806                RawTerminator::Switch { discr, targets }
807            }
808            TerminatorKind::UnwindResume => RawTerminator::UnwindResume,
809            TerminatorKind::UnwindTerminate { .. } => {
810                RawTerminator::Abort(AbortKind::UnwindTerminate)
811            }
812            TerminatorKind::Return => RawTerminator::Return,
813            // A MIR `Unreachable` terminator indicates undefined behavior of the rust abstract
814            // machine.
815            TerminatorKind::Unreachable => RawTerminator::Abort(AbortKind::UndefinedBehavior),
816            TerminatorKind::Drop {
817                place,
818                impl_expr,
819                target,
820                unwind: _, // We consider that panic is an error, and don't model unwinding
821                ..
822            } => {
823                let place = self.translate_place(span, place)?;
824                let tref = self.translate_trait_impl_expr(span, impl_expr)?;
825                statements.push(Statement::new(span, RawStatement::Drop(place, tref)));
826                let target = self.translate_basic_block_id(*target);
827                RawTerminator::Goto { target }
828            }
829            TerminatorKind::Call {
830                fun,
831                args,
832                destination,
833                target,
834                unwind,
835                fn_span: _,
836                ..
837            } => self.translate_function_call(span, fun, args, destination, target, unwind)?,
838            TerminatorKind::Assert {
839                cond,
840                expected,
841                msg: _,
842                target,
843                unwind: _, // We model unwinding as an effet, we don't represent it in control flow
844            } => {
845                let assert = Assert {
846                    cond: self.translate_operand(span, cond)?,
847                    expected: *expected,
848                    on_failure: AbortKind::Panic(None),
849                };
850                statements.push(Statement::new(span, RawStatement::Assert(assert)));
851                let target = self.translate_basic_block_id(*target);
852                RawTerminator::Goto { target }
853            }
854            TerminatorKind::FalseEdge {
855                real_target,
856                imaginary_target,
857            } => {
858                trace!(
859                    "False edge:\n- real target ({:?}):\n{:?}\n- imaginary target ({:?}):\n{:?}",
860                    real_target,
861                    body.basic_blocks.get(*real_target).unwrap(),
862                    imaginary_target,
863                    body.basic_blocks.get(*imaginary_target).unwrap(),
864                );
865
866                // False edges are used to make the borrow checker a bit conservative.
867                // We translate them as Gotos.
868                // Also note that they are used in some passes, and not in some others
869                // (they are present in mir_promoted, but not mir_optimized).
870                let target = self.translate_basic_block_id(*real_target);
871                RawTerminator::Goto { target }
872            }
873            TerminatorKind::FalseUnwind {
874                real_target,
875                unwind: _,
876            } => {
877                // We consider this to be a goto
878                let target = self.translate_basic_block_id(*real_target);
879                RawTerminator::Goto { target }
880            }
881            TerminatorKind::InlineAsm { .. } => {
882                raise_error!(self, span, "Inline assembly is not supported");
883            }
884            TerminatorKind::CoroutineDrop
885            | TerminatorKind::TailCall { .. }
886            | TerminatorKind::Yield { .. } => {
887                raise_error!(self, span, "Unsupported terminator: {:?}", terminator.kind);
888            }
889        };
890
891        // Add the span information
892        Ok(Terminator::new(span, t_terminator))
893    }
894
895    /// Translate switch targets
896    fn translate_switch_targets(
897        &mut self,
898        span: Span,
899        switch_ty: &Ty,
900        targets: &[(hax::ScalarInt, hax::BasicBlock)],
901        otherwise: &hax::BasicBlock,
902    ) -> Result<SwitchTargets, Error> {
903        trace!("targets: {:?}", targets);
904        let switch_ty = *switch_ty.kind().as_literal().unwrap();
905        match switch_ty {
906            LiteralTy::Bool => {
907                assert_eq!(targets.len(), 1);
908                let (val, target) = targets.first().unwrap();
909                // It seems the block targets are inverted
910                assert_eq!(val.data_le_bytes, [0; 16]);
911                let if_block = self.translate_basic_block_id(*otherwise);
912                let then_block = self.translate_basic_block_id(*target);
913                Ok(SwitchTargets::If(if_block, then_block))
914            }
915            LiteralTy::Integer(int_ty) => {
916                let targets: Vec<(ScalarValue, BlockId)> = targets
917                    .iter()
918                    .map(|(v, tgt)| {
919                        let v = ScalarValue::from_le_bytes(int_ty, v.data_le_bytes);
920                        let tgt = self.translate_basic_block_id(*tgt);
921                        Ok((v, tgt))
922                    })
923                    .try_collect()?;
924                let otherwise = self.translate_basic_block_id(*otherwise);
925                Ok(SwitchTargets::SwitchInt(int_ty, targets, otherwise))
926            }
927            _ => raise_error!(self, span, "Can't match on type {switch_ty}"),
928        }
929    }
930
931    /// Translate a function call statement.
932    /// Note that `body` is the body of the function being translated, not of the
933    /// function referenced in the function call: we need it in order to translate
934    /// the blocks we go to after the function call returns.
935    #[allow(clippy::too_many_arguments)]
936    fn translate_function_call(
937        &mut self,
938        span: Span,
939        fun: &hax::FunOperand,
940        args: &Vec<hax::Spanned<hax::Operand>>,
941        destination: &hax::Place,
942        target: &Option<hax::BasicBlock>,
943        unwind: &UnwindAction,
944    ) -> Result<RawTerminator, Error> {
945        trace!();
946        // There are two cases, depending on whether this is a "regular"
947        // call to a top-level function identified by its id, or if we
948        // are using a local function pointer (i.e., the operand is a "move").
949        let lval = self.translate_place(span, destination)?;
950        // Translate the function operand.
951        let fn_operand = match fun {
952            hax::FunOperand::Static(item) => {
953                trace!("func: {:?}", item.def_id);
954                let fun_def = self.hax_def(&item.def_id)?;
955                let fun_src = TransItemSource::new(item.def_id.clone(), TransItemSourceKind::Fun);
956                let name = self.t_ctx.translate_name(&fun_src)?;
957                let panic_lang_items = &["panic", "panic_fmt", "begin_panic"];
958                let panic_names = &[&["core", "panicking", "assert_failed"], EXPLICIT_PANIC_NAME];
959
960                if fun_def
961                    .lang_item
962                    .as_deref()
963                    .is_some_and(|lang_it| panic_lang_items.iter().contains(&lang_it))
964                    || panic_names.iter().any(|panic| name.equals_ref_name(panic))
965                {
966                    // If the call is `panic!`, then the target is `None`.
967                    // I don't know in which other cases it can be `None`.
968                    assert!(target.is_none());
969                    // We ignore the arguments
970                    return Ok(RawTerminator::Abort(AbortKind::Panic(Some(name))));
971                } else {
972                    let fn_ptr = self.translate_fn_ptr(span, item)?.erase();
973                    FnOperand::Regular(fn_ptr)
974                }
975            }
976            hax::FunOperand::DynamicMove(p) => {
977                // Call to a local function pointer
978                let p = self.translate_place(span, p)?;
979
980                // TODO: we may have a problem here because as we don't
981                // know which function is being called, we may not be
982                // able to filter the arguments properly... But maybe
983                // this is rather an issue for the statement which creates
984                // the function pointer, by refering to a top-level function
985                // for instance.
986                FnOperand::Move(p)
987            }
988        };
989        let args = self.translate_arguments(span, args)?;
990        let call = Call {
991            func: fn_operand,
992            args,
993            dest: lval,
994        };
995
996        let target = match target {
997            Some(target) => self.translate_basic_block_id(*target),
998            None => {
999                let abort =
1000                    Terminator::new(span, RawTerminator::Abort(AbortKind::UndefinedBehavior));
1001                self.blocks.push(abort.into_block())
1002            }
1003        };
1004        let on_unwind = match unwind {
1005            UnwindAction::Continue => {
1006                let unwind_continue = Terminator::new(span, RawTerminator::UnwindResume);
1007                self.blocks.push(unwind_continue.into_block())
1008            }
1009            UnwindAction::Unreachable => {
1010                let abort =
1011                    Terminator::new(span, RawTerminator::Abort(AbortKind::UndefinedBehavior));
1012                self.blocks.push(abort.into_block())
1013            }
1014            UnwindAction::Terminate(..) => {
1015                let abort = Terminator::new(span, RawTerminator::Abort(AbortKind::UnwindTerminate));
1016                self.blocks.push(abort.into_block())
1017            }
1018            UnwindAction::Cleanup(bb) => self.translate_basic_block_id(*bb),
1019        };
1020        Ok(RawTerminator::Call {
1021            call,
1022            target,
1023            on_unwind,
1024        })
1025    }
1026
1027    /// Evaluate function arguments in a context, and return the list of computed
1028    /// values.
1029    fn translate_arguments(
1030        &mut self,
1031        span: Span,
1032        args: &Vec<hax::Spanned<hax::Operand>>,
1033    ) -> Result<Vec<Operand>, Error> {
1034        let mut t_args: Vec<Operand> = Vec::new();
1035        for arg in args.iter().map(|x| &x.node) {
1036            // Translate
1037            let op = self.translate_operand(span, arg)?;
1038            t_args.push(op);
1039        }
1040        Ok(t_args)
1041    }
1042
1043    /// Gather all the lines that start with `//` inside the given span.
1044    fn translate_body_comments(
1045        &mut self,
1046        source_text: &Option<String>,
1047        charon_span: Span,
1048    ) -> Vec<(usize, Vec<String>)> {
1049        if let Some(body_text) = source_text {
1050            let mut comments = body_text
1051                .lines()
1052                // Iter through the lines of this body in reverse order.
1053                .rev()
1054                .enumerate()
1055                // Compute the absolute line number
1056                .map(|(i, line)| (charon_span.span.end.line - i, line))
1057                // Extract the comment if this line starts with `//`
1058                .map(|(line_nbr, line)| (line_nbr, line.trim_start().strip_prefix("//")))
1059                .peekable()
1060                .batching(|iter| {
1061                    // Get the next line. This is not a comment: it's either the last line of the
1062                    // body or a line that wasn't consumed by `peeking_take_while`.
1063                    let (line_nbr, _first) = iter.next()?;
1064                    // Collect all the comments before this line.
1065                    let mut comments = iter
1066                        // `peeking_take_while` ensures we don't consume a line that returns
1067                        // `false`. It will be consumed by the next round of `batching`.
1068                        .peeking_take_while(|(_, opt_comment)| opt_comment.is_some())
1069                        .map(|(_, opt_comment)| opt_comment.unwrap())
1070                        .map(|s| s.strip_prefix(" ").unwrap_or(s))
1071                        .map(str::to_owned)
1072                        .collect_vec();
1073                    comments.reverse();
1074                    Some((line_nbr, comments))
1075                })
1076                .filter(|(_, comments)| !comments.is_empty())
1077                .collect_vec();
1078            comments.reverse();
1079            comments
1080        } else {
1081            Vec::new()
1082        }
1083    }
1084
1085    /// Translate the MIR body of this definition if it has one.
1086    pub fn translate_def_body(
1087        &mut self,
1088        span: Span,
1089        def: &hax::FullDef,
1090    ) -> Result<Result<Body, Opaque>, Error> {
1091        // Retrieve the body
1092        let Some(body) = self.t_ctx.get_mir(&def.def_id, span)? else {
1093            return Ok(Err(Opaque));
1094        };
1095        self.translate_body(span, &body, &def.source_text)
1096    }
1097
1098    /// Translate a function body.
1099    pub fn translate_body(
1100        &mut self,
1101        span: Span,
1102        body: &hax::MirBody<hax::mir_kinds::Unknown>,
1103        source_text: &Option<String>,
1104    ) -> Result<Result<Body, Opaque>, Error> {
1105        // Stopgap measure because there are still many panics in charon and hax.
1106        let mut this = panic::AssertUnwindSafe(&mut *self);
1107        let res = panic::catch_unwind(move || this.translate_body_aux(body, source_text));
1108        match res {
1109            Ok(Ok(body)) => Ok(body),
1110            // Translation error
1111            Ok(Err(e)) => Err(e),
1112            Err(_) => {
1113                raise_error!(self, span, "Thread panicked when extracting body.");
1114            }
1115        }
1116    }
1117
1118    fn translate_body_aux(
1119        &mut self,
1120        body: &hax::MirBody<hax::mir_kinds::Unknown>,
1121        source_text: &Option<String>,
1122    ) -> Result<Result<Body, Opaque>, Error> {
1123        // Compute the span information
1124        let span = self.translate_span_from_hax(&body.span);
1125
1126        // Initialize the local variables
1127        trace!("Translating the body locals");
1128        self.locals.arg_count = body.arg_count;
1129        self.translate_body_locals(&body)?;
1130
1131        // Translate the expression body
1132        trace!("Translating the expression body");
1133
1134        // Register the start block
1135        let id = self.translate_basic_block_id(rustc_index::Idx::new(mir::START_BLOCK.as_usize()));
1136        assert!(id == START_BLOCK_ID);
1137
1138        // For as long as there are blocks in the stack, translate them
1139        while let Some(hax_block_id) = self.blocks_stack.pop_front() {
1140            let hax_block = body.basic_blocks.get(hax_block_id).unwrap();
1141            let block_id = self.translate_basic_block_id(hax_block_id);
1142            let block = self.translate_basic_block(&body, hax_block)?;
1143            self.blocks.set_slot(block_id, block);
1144        }
1145
1146        // Create the body
1147        Ok(Ok(Body::Unstructured(ExprBody {
1148            span,
1149            locals: mem::take(&mut self.locals),
1150            body: mem::take(&mut self.blocks),
1151            comments: self.translate_body_comments(source_text, span),
1152        })))
1153    }
1154}
1155
1156impl<'a> IntoFormatter for &'a BodyTransCtx<'_, '_, '_> {
1157    type C = FmtCtx<'a>;
1158    fn into_fmt(self) -> Self::C {
1159        FmtCtx {
1160            locals: Some(&self.locals),
1161            ..self.i_ctx.into_fmt()
1162        }
1163    }
1164}
charon_driver/translate/translate_bodies.rs

charon_driver/translate/
translate_bodies.rs
