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Diffstat (limited to 'compiler/InterpreterProjectors.ml')
| -rw-r--r-- | compiler/InterpreterProjectors.ml | 543 |
1 files changed, 543 insertions, 0 deletions
diff --git a/compiler/InterpreterProjectors.ml b/compiler/InterpreterProjectors.ml new file mode 100644 index 00000000..064b8969 --- /dev/null +++ b/compiler/InterpreterProjectors.ml @@ -0,0 +1,543 @@ +module T = Types +module V = Values +module E = Expressions +module C = Contexts +module Subst = Substitute +module L = Logging +open TypesUtils +open InterpreterUtils +open InterpreterBorrowsCore + +(** Auxiliary function. + + Apply a proj_borrows on a shared borrow. + Note that when projecting over shared values, we generate + {!V.abstract_shared_borrows}, not {!V.avalue}s. +*) +let rec apply_proj_borrows_on_shared_borrow (ctx : C.eval_ctx) + (fresh_reborrow : V.BorrowId.id -> V.BorrowId.id) + (regions : T.RegionId.Set.t) (v : V.typed_value) (ty : T.rty) : + V.abstract_shared_borrows = + (* Sanity check - TODO: move this elsewhere (here we perform the check at every + * recursive call which is a bit overkill...) *) + let ety = Subst.erase_regions ty in + assert (ety = v.V.ty); + (* Project - if there are no regions from the abstraction in the type, return [_] *) + if not (ty_has_regions_in_set regions ty) then [] + else + match (v.V.value, ty) with + | V.Concrete _, (T.Bool | T.Char | T.Integer _ | T.Str) -> [] + | V.Adt adt, T.Adt (id, region_params, tys) -> + (* Retrieve the types of the fields *) + let field_types = + Subst.ctx_adt_value_get_instantiated_field_rtypes ctx adt id + region_params tys + in + (* Project over the field values *) + let fields_types = List.combine adt.V.field_values field_types in + let proj_fields = + List.map + (fun (fv, fty) -> + apply_proj_borrows_on_shared_borrow ctx fresh_reborrow regions fv + fty) + fields_types + in + List.concat proj_fields + | V.Bottom, _ -> failwith "Unreachable" + | V.Borrow bc, T.Ref (r, ref_ty, kind) -> + (* Retrieve the bid of the borrow and the asb of the projected borrowed value *) + let bid, asb = + (* Not in the set: dive *) + match (bc, kind) with + | V.MutBorrow (bid, bv), T.Mut -> + (* Apply the projection on the borrowed value *) + let asb = + apply_proj_borrows_on_shared_borrow ctx fresh_reborrow regions + bv ref_ty + in + (bid, asb) + | V.SharedBorrow (_, bid), T.Shared -> + (* Lookup the shared value *) + let ek = ek_all in + let sv = lookup_loan ek bid ctx in + let asb = + match sv with + | _, Concrete (V.SharedLoan (_, sv)) + | _, Abstract (V.ASharedLoan (_, sv, _)) -> + apply_proj_borrows_on_shared_borrow ctx fresh_reborrow + regions sv ref_ty + | _ -> failwith "Unexpected" + in + (bid, asb) + | V.InactivatedMutBorrow _, _ -> + failwith + "Can't apply a proj_borrow over an inactivated mutable borrow" + | _ -> failwith "Unreachable" + in + let asb = + (* Check if the region is in the set of projected regions (note that + * we never project over static regions) *) + if region_in_set r regions then + let bid' = fresh_reborrow bid in + V.AsbBorrow bid' :: asb + else asb + in + asb + | V.Loan _, _ -> failwith "Unreachable" + | V.Symbolic s, _ -> + (* Check that the projection doesn't contain ended regions *) + assert ( + not (projections_intersect s.V.sv_ty ctx.ended_regions ty regions)); + [ V.AsbProjReborrows (s, ty) ] + | _ -> failwith "Unreachable" + +(** Apply (and reduce) a projector over borrows to a value. + + - [regions]: the regions we project + - [v]: the value over which we project + - [ty]: the projection type (is used to map borrows to regions, or to + interpret the borrows as belonging to some regions...). Remember that + [v] doesn't contain region information. + For instance, if we have: + [v <: ty] where: + - [v = mut_borrow l ...] + - [ty = Ref (r, ...)] + then we interpret the borrow [l] as belonging to region [r] + + Also, when applying projections on shared values, we need to apply + reborrows. This is a bit annoying because, with the way we compute + the projection on borrows, we can't update the context immediately. + Instead, we remember the list of borrows we have to insert in the + context *afterwards*. + + [check_symbolic_no_ended] controls whether we check or not whether + symbolic values don't contain already ended regions. + This check is activated when applying projectors upon calling a function + (because we need to check that function arguments don't contain ⊥), + but deactivated when expanding symbolic values: + {[ + fn f<'a,'b>(x : &'a mut u32, y : &'b mut u32) -> (&'a mut u32, &'b mut u32); + + let p = f(&mut x, &mut y); // p -> @s0 + assert(x == ...); // end 'a + let z = p.1; // HERE: the symbolic expansion of @s0 contains ended regions + ]} +*) +let rec apply_proj_borrows (check_symbolic_no_ended : bool) (ctx : C.eval_ctx) + (fresh_reborrow : V.BorrowId.id -> V.BorrowId.id) + (regions : T.RegionId.Set.t) (ancestors_regions : T.RegionId.Set.t) + (v : V.typed_value) (ty : T.rty) : V.typed_avalue = + (* Sanity check - TODO: move this elsewhere (here we perform the check at every + * recursive call which is a bit overkill...) *) + let ety = Substitute.erase_regions ty in + assert (ety = v.V.ty); + (* Project - if there are no regions from the abstraction in the type, return [_] *) + if not (ty_has_regions_in_set regions ty) then { V.value = V.AIgnored; ty } + else + let value : V.avalue = + match (v.V.value, ty) with + | V.Concrete cv, (T.Bool | T.Char | T.Integer _ | T.Str) -> V.AConcrete cv + | V.Adt adt, T.Adt (id, region_params, tys) -> + (* Retrieve the types of the fields *) + let field_types = + Subst.ctx_adt_value_get_instantiated_field_rtypes ctx adt id + region_params tys + in + (* Project over the field values *) + let fields_types = List.combine adt.V.field_values field_types in + let proj_fields = + List.map + (fun (fv, fty) -> + apply_proj_borrows check_symbolic_no_ended ctx fresh_reborrow + regions ancestors_regions fv fty) + fields_types + in + V.AAdt { V.variant_id = adt.V.variant_id; field_values = proj_fields } + | V.Bottom, _ -> failwith "Unreachable" + | V.Borrow bc, T.Ref (r, ref_ty, kind) -> + if + (* Check if the region is in the set of projected regions (note that + * we never project over static regions) *) + region_in_set r regions + then + (* In the set *) + let bc = + match (bc, kind) with + | V.MutBorrow (bid, bv), T.Mut -> + (* Remember the borrowed value we are about to project as a meta-value *) + let mv = bv in + (* Apply the projection on the borrowed value *) + let bv = + apply_proj_borrows check_symbolic_no_ended ctx + fresh_reborrow regions ancestors_regions bv ref_ty + in + V.AMutBorrow (mv, bid, bv) + | V.SharedBorrow (_, bid), T.Shared -> V.ASharedBorrow bid + | V.InactivatedMutBorrow _, _ -> + failwith + "Can't apply a proj_borrow over an inactivated mutable \ + borrow" + | _ -> failwith "Unreachable" + in + V.ABorrow bc + else + (* Not in the set: ignore *) + let bc = + match (bc, kind) with + | V.MutBorrow (bid, bv), T.Mut -> + (* Apply the projection on the borrowed value *) + let bv = + apply_proj_borrows check_symbolic_no_ended ctx + fresh_reborrow regions ancestors_regions bv ref_ty + in + (* If the borrow id is in the ancestor's regions, we still need + * to remember it *) + let opt_bid = + if region_in_set r ancestors_regions then Some bid else None + in + (* Return *) + V.AIgnoredMutBorrow (opt_bid, bv) + | V.SharedBorrow (_, bid), T.Shared -> + (* Lookup the shared value *) + let ek = ek_all in + let sv = lookup_loan ek bid ctx in + let asb = + match sv with + | _, Concrete (V.SharedLoan (_, sv)) + | _, Abstract (V.ASharedLoan (_, sv, _)) -> + apply_proj_borrows_on_shared_borrow ctx fresh_reborrow + regions sv ref_ty + | _ -> failwith "Unexpected" + in + V.AProjSharedBorrow asb + | V.InactivatedMutBorrow _, _ -> + failwith + "Can't apply a proj_borrow over an inactivated mutable \ + borrow" + | _ -> failwith "Unreachable" + in + V.ABorrow bc + | V.Loan _, _ -> failwith "Unreachable" + | V.Symbolic s, _ -> + (* Check that the projection doesn't contain already ended regions, + * if necessary *) + if check_symbolic_no_ended then ( + let ty1 = s.V.sv_ty in + let rset1 = ctx.ended_regions in + let ty2 = ty in + let rset2 = regions in + log#ldebug + (lazy + ("projections_intersect:" ^ "\n- ty1: " ^ rty_to_string ctx ty1 + ^ "\n- rset1: " + ^ T.RegionId.Set.to_string None rset1 + ^ "\n- ty2: " ^ rty_to_string ctx ty2 ^ "\n- rset2: " + ^ T.RegionId.Set.to_string None rset2 + ^ "\n")); + assert (not (projections_intersect ty1 rset1 ty2 rset2))); + V.ASymbolic (V.AProjBorrows (s, ty)) + | _ -> + log#lerror + (lazy + ("apply_proj_borrows: unexpected inputs:\n- input value: " + ^ typed_value_to_string ctx v + ^ "\n- proj rty: " ^ rty_to_string ctx ty)); + failwith "Unreachable" + in + { V.value; V.ty } + +(** Convert a symbolic expansion *which is not a borrow* to a value *) +let symbolic_expansion_non_borrow_to_value (sv : V.symbolic_value) + (see : V.symbolic_expansion) : V.typed_value = + let ty = Subst.erase_regions sv.V.sv_ty in + let value = + match see with + | SeConcrete cv -> V.Concrete cv + | SeAdt (variant_id, field_values) -> + let field_values = + List.map mk_typed_value_from_symbolic_value field_values + in + V.Adt { V.variant_id; V.field_values } + | SeMutRef (_, _) | SeSharedRef (_, _) -> + failwith "Unexpected symbolic reference expansion" + in + { V.value; V.ty } + +(** Convert a symbolic expansion to a value. + + If the expansion is a mutable reference expansion, it converts it to a borrow. + This function is meant to be used when reducing projectors over borrows, + during a symbolic expansion. + *) +let symbolic_expansion_non_shared_borrow_to_value (sv : V.symbolic_value) + (see : V.symbolic_expansion) : V.typed_value = + match see with + | SeMutRef (bid, bv) -> + let ty = Subst.erase_regions sv.V.sv_ty in + let bv = mk_typed_value_from_symbolic_value bv in + let value = V.Borrow (V.MutBorrow (bid, bv)) in + { V.value; ty } + | SeSharedRef (_, _) -> + failwith "Unexpected symbolic shared reference expansion" + | _ -> symbolic_expansion_non_borrow_to_value sv see + +(** Apply (and reduce) a projector over loans to a value. + + TODO: detailed comments. See [apply_proj_borrows] +*) +let apply_proj_loans_on_symbolic_expansion (regions : T.RegionId.Set.t) + (see : V.symbolic_expansion) (original_sv_ty : T.rty) : V.typed_avalue = + (* Sanity check: if we have a proj_loans over a symbolic value, it should + * contain regions which we will project *) + assert (ty_has_regions_in_set regions original_sv_ty); + (* Match *) + let (value, ty) : V.avalue * T.rty = + match (see, original_sv_ty) with + | SeConcrete _, (T.Bool | T.Char | T.Integer _ | T.Str) -> + (V.AIgnored, original_sv_ty) + | SeAdt (variant_id, field_values), T.Adt (_id, _region_params, _tys) -> + (* Project over the field values *) + let field_values = + List.map + (mk_aproj_loans_value_from_symbolic_value regions) + field_values + in + (V.AAdt { V.variant_id; field_values }, original_sv_ty) + | SeMutRef (bid, spc), T.Ref (r, ref_ty, T.Mut) -> + (* Sanity check *) + assert (spc.V.sv_ty = ref_ty); + (* Apply the projector to the borrowed value *) + let child_av = mk_aproj_loans_value_from_symbolic_value regions spc in + (* Check if the region is in the set of projected regions (note that + * we never project over static regions) *) + if region_in_set r regions then + (* In the set: keep *) + (V.ALoan (V.AMutLoan (bid, child_av)), ref_ty) + else + (* Not in the set: ignore *) + (V.ALoan (V.AIgnoredMutLoan (bid, child_av)), ref_ty) + | SeSharedRef (bids, spc), T.Ref (r, ref_ty, T.Shared) -> + (* Sanity check *) + assert (spc.V.sv_ty = ref_ty); + (* Apply the projector to the borrowed value *) + let child_av = mk_aproj_loans_value_from_symbolic_value regions spc in + (* Check if the region is in the set of projected regions (note that + * we never project over static regions) *) + if region_in_set r regions then + (* In the set: keep *) + let shared_value = mk_typed_value_from_symbolic_value spc in + (V.ALoan (V.ASharedLoan (bids, shared_value, child_av)), ref_ty) + else + (* Not in the set: ignore *) + (V.ALoan (V.AIgnoredSharedLoan child_av), ref_ty) + | _ -> failwith "Unreachable" + in + { V.value; V.ty } + +(** Auxiliary function. See [give_back_value]. + + Apply reborrows to a context. + + The [reborrows] input is a list of pairs (shared loan id, id to insert + in the shared loan). + This function is used when applying projectors on shared borrows: when + doing so, we might need to reborrow subvalues from the shared value. + For instance: + {[ + fn f<'a,'b,'c>(x : &'a 'b 'c u32) + ]} + When introducing the abstractions for 'a, 'b and 'c, we apply a projector + on some value [shared_borrow l : &'a &'b &'c u32]. + In the 'a abstraction, this shared borrow gets projected. However, when + reducing the projectors for the 'b and 'c abstractions, we need to make + sure that the borrows living in regions 'b and 'c live as long as those + regions. This is done by looking up the shared value and applying reborrows + on the borrows we find there (note that those reborrows apply on shared + borrows - easy - and mutable borrows - in this case, we reborrow the whole + borrow: [mut_borrow ... ~~> shared_loan {...} (mut_borrow ...)]). +*) +let apply_reborrows (reborrows : (V.BorrowId.id * V.BorrowId.id) list) + (ctx : C.eval_ctx) : C.eval_ctx = + (* This is a bit brutal, but whenever we insert a reborrow, we remove + * it from the list. This allows us to check that all the reborrows were + * applied before returning. + * We might reimplement that in a more efficient manner by using maps. *) + let reborrows = ref reborrows in + + (* Check if a value is a mutable borrow, and return its identifier if + it is the case *) + let get_borrow_in_mut_borrow (v : V.typed_value) : V.BorrowId.id option = + match v.V.value with + | V.Borrow lc -> ( + match lc with + | V.SharedBorrow (_, _) | V.InactivatedMutBorrow _ -> None + | V.MutBorrow (id, _) -> Some id) + | _ -> None + in + + (* Add the proper reborrows to a set of borrow ids (for a shared loan) *) + let insert_reborrows bids = + (* Find the reborrows to apply *) + let insert, reborrows' = + List.partition (fun (bid, _) -> V.BorrowId.Set.mem bid bids) !reborrows + in + reborrows := reborrows'; + let insert = List.map snd insert in + (* Insert the borrows *) + List.fold_left (fun bids bid -> V.BorrowId.Set.add bid bids) bids insert + in + + (* Get the list of reborrows for a given borrow id *) + let get_reborrows_for_bid bid = + (* Find the reborrows to apply *) + let insert, reborrows' = + List.partition (fun (bid', _) -> bid' = bid) !reborrows + in + reborrows := reborrows'; + List.map snd insert + in + + let borrows_to_set bids = + List.fold_left + (fun bids bid -> V.BorrowId.Set.add bid bids) + V.BorrowId.Set.empty bids + in + + (* Insert reborrows for a given borrow id into a given set of borrows *) + let insert_reborrows_for_bid bids bid = + (* Find the reborrows to apply *) + let insert = get_reborrows_for_bid bid in + (* Insert the borrows *) + List.fold_left (fun bids bid -> V.BorrowId.Set.add bid bids) bids insert + in + + let obj = + object + inherit [_] C.map_eval_ctx as super + + (** We may need to reborrow mutable borrows. Note that this doesn't + happen for aborrows *) + method! visit_typed_value env v = + match v.V.value with + | V.Borrow (V.MutBorrow (bid, bv)) -> + let insert = get_reborrows_for_bid bid in + let nbc = super#visit_MutBorrow env bid bv in + let nbc = { v with V.value = V.Borrow nbc } in + if insert = [] then (* No reborrows: do nothing special *) + nbc + else + (* There are reborrows: insert a shared loan *) + let insert = borrows_to_set insert in + let value = V.Loan (V.SharedLoan (insert, nbc)) in + let ty = v.V.ty in + { V.value; ty } + | _ -> super#visit_typed_value env v + + (** We reimplement {!visit_loan_content} (rather than one of the sub- + functions) on purpose: exhaustive matches are good for maintenance *) + method! visit_loan_content env lc = + match lc with + | V.SharedLoan (bids, sv) -> + (* Insert the reborrows *) + let bids = insert_reborrows bids in + (* Check if the contained value is a mutable borrow, in which + * case we might need to reborrow it by adding more borrow ids + * to the current set of borrows - by doing this small + * manipulation here, we accumulate the borrow ids in the same + * shared loan, right above the mutable borrow, and avoid + * stacking shared loans (note that doing this is not a problem + * from a soundness point of view, but it is a bit ugly...) *) + let bids = + match get_borrow_in_mut_borrow sv with + | None -> bids + | Some bid -> insert_reborrows_for_bid bids bid + in + (* Update and explore *) + super#visit_SharedLoan env bids sv + | V.MutLoan bid -> + (* Nothing special to do *) + super#visit_MutLoan env bid + + method! visit_aloan_content env lc = + match lc with + | V.ASharedLoan (bids, sv, av) -> + (* Insert the reborrows *) + let bids = insert_reborrows bids in + (* Similarly to the non-abstraction case: check if the shared + * value is a mutable borrow, to eventually insert more reborrows *) + (* Update and explore *) + let bids = + match get_borrow_in_mut_borrow sv with + | None -> bids + | Some bid -> insert_reborrows_for_bid bids bid + in + (* Update and explore *) + super#visit_ASharedLoan env bids sv av + | V.AIgnoredSharedLoan _ + | V.AMutLoan (_, _) + | V.AEndedMutLoan { given_back = _; child = _; given_back_meta = _ } + | V.AEndedSharedLoan (_, _) + | V.AIgnoredMutLoan (_, _) + | V.AEndedIgnoredMutLoan + { given_back = _; child = _; given_back_meta = _ } -> + (* Nothing particular to do *) + super#visit_aloan_content env lc + end + in + + (* Visit *) + let ctx = obj#visit_eval_ctx () ctx in + (* Check that there are no reborrows remaining *) + assert (!reborrows = []); + (* Return *) + ctx + +(** Auxiliary function to prepare reborrowing operations (used when + applying projectors). + + Returns two functions: + - a function to generate fresh re-borrow ids, and register the reborrows + - a function to apply the reborrows in a context + Those functions are of course stateful. + *) +let prepare_reborrows (config : C.config) (allow_reborrows : bool) : + (V.BorrowId.id -> V.BorrowId.id) * (C.eval_ctx -> C.eval_ctx) = + let reborrows : (V.BorrowId.id * V.BorrowId.id) list ref = ref [] in + (* The function to generate and register fresh reborrows *) + let fresh_reborrow (bid : V.BorrowId.id) : V.BorrowId.id = + if allow_reborrows then ( + let bid' = C.fresh_borrow_id () in + reborrows := (bid, bid') :: !reborrows; + bid') + else failwith "Unexpected reborrow" + in + (* The function to apply the reborrows in a context *) + let apply_registered_reborrows (ctx : C.eval_ctx) : C.eval_ctx = + match config.C.mode with + | C.ConcreteMode -> + assert (!reborrows = []); + ctx + | C.SymbolicMode -> + (* Apply the reborrows *) + apply_reborrows !reborrows ctx + in + (fresh_reborrow, apply_registered_reborrows) + +let apply_proj_borrows_on_input_value (config : C.config) (ctx : C.eval_ctx) + (regions : T.RegionId.Set.t) (ancestors_regions : T.RegionId.Set.t) + (v : V.typed_value) (ty : T.rty) : C.eval_ctx * V.typed_avalue = + let check_symbolic_no_ended = true in + let allow_reborrows = true in + (* Prepare the reborrows *) + let fresh_reborrow, apply_registered_reborrows = + prepare_reborrows config allow_reborrows + in + (* Apply the projector *) + let av = + apply_proj_borrows check_symbolic_no_ended ctx fresh_reborrow regions + ancestors_regions v ty + in + (* Apply the reborrows *) + let ctx = apply_registered_reborrows ctx in + (* Return *) + (ctx, av) |