[6d6e829] | 1 | // |
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| 2 | // Cforall Version 1.0.0 Copyright (C) 2015 University of Waterloo |
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| 3 | // |
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| 4 | // The contents of this file are covered under the licence agreement in the |
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| 5 | // file "LICENCE" distributed with Cforall. |
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| 6 | // |
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| 7 | // ResolveAssertions.cc -- |
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| 8 | // |
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| 9 | // Author : Aaron B. Moss |
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| 10 | // Created On : Fri Oct 05 13:46:00 2018 |
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| 11 | // Last Modified By : Aaron B. Moss |
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| 12 | // Last Modified On : Fri Oct 05 13:46:00 2018 |
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| 13 | // Update Count : 1 |
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| 14 | // |
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| 15 | |
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| 16 | #include "ResolveAssertions.h" |
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| 17 | |
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[b3bd772] | 18 | #include <algorithm> // for sort |
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[83ab931] | 19 | #include <cassert> // for assertf |
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| 20 | #include <list> // for list |
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[b3bd772] | 21 | #include <memory> // for unique_ptr |
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[4d2d45f9] | 22 | #include <sstream> // for ostringstream |
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| 23 | #include <string> // for string |
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[83ab931] | 24 | #include <unordered_map> // for unordered_map, unordered_multimap |
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| 25 | #include <utility> // for move |
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| 26 | #include <vector> // for vector |
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| 27 | |
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| 28 | #include "Alternative.h" // for Alternative, AssertionItem, AssertionList |
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| 29 | #include "Common/FilterCombos.h" // for filterCombos |
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[4d2d45f9] | 30 | #include "Common/Indenter.h" // for Indenter |
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[83ab931] | 31 | #include "Common/utility.h" // for sort_mins |
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| 32 | #include "ResolvExpr/RenameVars.h" // for renameTyVars |
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| 33 | #include "SymTab/Indexer.h" // for Indexer |
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[b3bd772] | 34 | #include "SymTab/Mangler.h" // for Mangler |
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[83ab931] | 35 | #include "SynTree/Expression.h" // for InferredParams |
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| 36 | #include "TypeEnvironment.h" // for TypeEnvironment, etc. |
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[052cd71] | 37 | #include "typeops.h" // for adjustExprType, specCost |
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[83ab931] | 38 | #include "Unify.h" // for unify |
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[6d6e829] | 39 | |
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| 40 | namespace ResolvExpr { |
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| 41 | /// Unified assertion candidate |
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| 42 | struct AssnCandidate { |
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| 43 | SymTab::Indexer::IdData cdata; ///< Satisfying declaration |
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| 44 | Type* adjType; ///< Satisfying type |
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| 45 | TypeEnvironment env; ///< Post-unification environment |
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| 46 | AssertionSet have; ///< Post-unification have-set |
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| 47 | AssertionSet need; ///< Post-unification need-set |
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| 48 | OpenVarSet openVars; ///< Post-unification open-var set |
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[0b00df0] | 49 | UniqueId resnSlot; ///< Slot for any recursive assertion IDs |
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[6d6e829] | 50 | |
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| 51 | AssnCandidate( const SymTab::Indexer::IdData& cdata, Type* adjType, TypeEnvironment&& env, |
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[0b00df0] | 52 | AssertionSet&& have, AssertionSet&& need, OpenVarSet&& openVars, UniqueId resnSlot ) |
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[6d6e829] | 53 | : cdata(cdata), adjType(adjType), env(std::move(env)), have(std::move(have)), |
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[0b00df0] | 54 | need(std::move(need)), openVars(std::move(openVars)), resnSlot(resnSlot) {} |
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[6d6e829] | 55 | }; |
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| 56 | |
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| 57 | /// List of candidate assertion resolutions |
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| 58 | using CandidateList = std::vector<AssnCandidate>; |
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| 59 | |
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| 60 | /// Reference to single deferred item |
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| 61 | struct DeferRef { |
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[052cd71] | 62 | const DeclarationWithType* decl; |
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| 63 | const AssertionSetValue& info; |
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[6d6e829] | 64 | const AssnCandidate& match; |
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| 65 | }; |
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| 66 | |
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| 67 | /// Wrapper for the deferred items from a single assertion resolution. |
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| 68 | /// Acts like indexed list of DeferRef |
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| 69 | struct DeferItem { |
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[052cd71] | 70 | const DeclarationWithType* decl; |
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| 71 | const AssertionSetValue& info; |
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| 72 | CandidateList matches; |
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[6d6e829] | 73 | |
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[052cd71] | 74 | DeferItem( DeclarationWithType* decl, const AssertionSetValue& info, CandidateList&& matches ) |
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| 75 | : decl(decl), info(info), matches(std::move(matches)) {} |
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[6d6e829] | 76 | |
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[052cd71] | 77 | bool empty() const { return matches.empty(); } |
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[6d6e829] | 78 | |
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[052cd71] | 79 | CandidateList::size_type size() const { return matches.size(); } |
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[4d2d45f9] | 80 | |
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[052cd71] | 81 | DeferRef operator[] ( unsigned i ) const { return { decl, info, matches[i] }; } |
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[6d6e829] | 82 | }; |
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| 83 | |
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| 84 | /// List of deferred resolution items |
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| 85 | using DeferList = std::vector<DeferItem>; |
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| 86 | |
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| 87 | /// Combo iterator that combines candidates into an output list, merging their environments. |
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| 88 | /// Rejects an appended candidate if the environments cannot be merged. |
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| 89 | class CandidateEnvMerger { |
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| 90 | /// Current list of merged candidates |
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| 91 | std::vector<DeferRef> crnt; |
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| 92 | /// Stack of environments to support backtracking |
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| 93 | std::vector<TypeEnvironment> envs; |
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| 94 | /// Stack of open variables to support backtracking |
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| 95 | std::vector<OpenVarSet> varSets; |
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| 96 | /// Indexer to use for merges |
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| 97 | const SymTab::Indexer& indexer; |
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| 98 | |
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| 99 | public: |
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| 100 | /// The merged environment/open variables and the list of candidates |
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| 101 | struct OutType { |
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| 102 | TypeEnvironment env; |
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| 103 | OpenVarSet openVars; |
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| 104 | std::vector<DeferRef> assns; |
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| 105 | |
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| 106 | OutType( const TypeEnvironment& env, const OpenVarSet& openVars, |
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| 107 | const std::vector<DeferRef>& assns ) |
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| 108 | : env(env), openVars(openVars), assns(assns) {} |
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| 109 | }; |
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| 110 | |
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| 111 | CandidateEnvMerger( const TypeEnvironment& env, const OpenVarSet& openVars, |
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| 112 | const SymTab::Indexer& indexer ) |
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| 113 | : crnt(), envs{ env }, varSets{ openVars }, indexer(indexer) {} |
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| 114 | |
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| 115 | bool append( DeferRef i ) { |
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| 116 | TypeEnvironment env = envs.back(); |
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| 117 | OpenVarSet openVars = varSets.back(); |
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| 118 | mergeOpenVars( openVars, i.match.openVars ); |
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| 119 | |
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| 120 | if ( ! env.combine( i.match.env, openVars, indexer ) ) return false; |
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| 121 | |
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| 122 | crnt.emplace_back( i ); |
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| 123 | envs.emplace_back( env ); |
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| 124 | varSets.emplace_back( openVars ); |
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| 125 | return true; |
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| 126 | } |
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| 127 | |
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| 128 | void backtrack() { |
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| 129 | crnt.pop_back(); |
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| 130 | envs.pop_back(); |
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| 131 | varSets.pop_back(); |
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| 132 | } |
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| 133 | |
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| 134 | OutType finalize() { return { envs.back(), varSets.back(), crnt }; } |
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| 135 | }; |
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| 136 | |
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[fbecee5] | 137 | /// Comparator for CandidateEnvMerger outputs that sums their costs and caches the stored |
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| 138 | /// sums |
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| 139 | struct CandidateCost { |
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| 140 | using Element = CandidateEnvMerger::OutType; |
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| 141 | private: |
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| 142 | using Memo = std::unordered_map<const Element*, Cost>; |
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| 143 | mutable Memo cache; ///< cache of element costs |
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| 144 | const SymTab::Indexer& indexer; ///< Indexer for costing |
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| 145 | |
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| 146 | public: |
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| 147 | CandidateCost( const SymTab::Indexer& indexer ) : indexer(indexer) {} |
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| 148 | |
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| 149 | /// reports the cost of an element |
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| 150 | Cost get( const Element& x ) const { |
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| 151 | Memo::const_iterator it = cache.find( &x ); |
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| 152 | if ( it == cache.end() ) { |
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| 153 | Cost k = Cost::zero; |
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| 154 | for ( const auto& assn : x.assns ) { |
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| 155 | k += computeConversionCost( |
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[052cd71] | 156 | assn.match.adjType, assn.decl->get_type(), indexer, x.env ); |
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[493a992] | 157 | |
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| 158 | // mark vars+specialization cost on function-type assertions |
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| 159 | PointerType* ptr = dynamic_cast< PointerType* >( assn.decl->get_type() ); |
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| 160 | if ( ! ptr ) continue; |
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| 161 | FunctionType* func = dynamic_cast< FunctionType* >( ptr->base ); |
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| 162 | if ( ! func ) continue; |
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| 163 | |
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| 164 | for ( DeclarationWithType* formal : func->parameters ) { |
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| 165 | k.decSpec( specCost( formal->get_type() ) ); |
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| 166 | } |
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| 167 | k.incVar( func->forall.size() ); |
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| 168 | for ( TypeDecl* td : func->forall ) { |
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| 169 | k.decSpec( td->assertions.size() ); |
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| 170 | } |
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[fbecee5] | 171 | } |
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| 172 | it = cache.emplace_hint( it, &x, k ); |
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| 173 | } |
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| 174 | return it->second; |
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| 175 | } |
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| 176 | |
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| 177 | /// compares elements by cost |
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| 178 | bool operator() ( const Element& a, const Element& b ) const { |
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| 179 | return get( a ) < get( b ); |
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| 180 | } |
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| 181 | }; |
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| 182 | |
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[0b00df0] | 183 | /// Set of assertion resolutions, grouped by resolution ID |
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| 184 | using InferCache = std::unordered_map< UniqueId, InferredParams >; |
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| 185 | |
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[6d6e829] | 186 | /// Flag for state iteration |
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| 187 | enum IterateFlag { IterateState }; |
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| 188 | |
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| 189 | /// State needed to resolve a set of assertions |
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| 190 | struct ResnState { |
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[0b00df0] | 191 | Alternative alt; ///< Alternative assertion is rooted on |
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| 192 | AssertionList need; ///< Assertions to find |
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| 193 | AssertionSet newNeed; ///< New assertions for current resolutions |
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| 194 | DeferList deferred; ///< Deferred matches |
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| 195 | InferCache inferred; ///< Cache of already-inferred parameters |
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| 196 | SymTab::Indexer& indexer; ///< Name lookup (depends on previous assertions) |
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[6d6e829] | 197 | |
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| 198 | /// Initial resolution state for an alternative |
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| 199 | ResnState( Alternative& a, SymTab::Indexer& indexer ) |
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[0b00df0] | 200 | : alt(a), need(), newNeed(), deferred(), inferred(), indexer(indexer) { |
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[6d6e829] | 201 | need.swap( a.need ); |
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| 202 | } |
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| 203 | |
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| 204 | /// Updated resolution state with new need-list |
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| 205 | ResnState( ResnState&& o, IterateFlag ) |
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| 206 | : alt(std::move(o.alt)), need(o.newNeed.begin(), o.newNeed.end()), newNeed(), deferred(), |
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[0b00df0] | 207 | inferred(std::move(o.inferred)), indexer(o.indexer) {} |
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[6d6e829] | 208 | }; |
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| 209 | |
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| 210 | /// Binds a single assertion, updating resolution state |
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| 211 | void bindAssertion( const DeclarationWithType* decl, AssertionSetValue info, Alternative& alt, |
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[0b00df0] | 212 | AssnCandidate& match, InferCache& inferred ) { |
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[6d6e829] | 213 | |
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| 214 | DeclarationWithType* candidate = match.cdata.id; |
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| 215 | assertf( candidate->get_uniqueId(), "Assertion candidate does not have a unique ID: %s", toString( candidate ).c_str() ); |
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| 216 | |
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| 217 | Expression* varExpr = match.cdata.combine( alt.cvtCost ); |
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[2c187378] | 218 | delete varExpr->result; |
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| 219 | varExpr->result = match.adjType->clone(); |
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[0b00df0] | 220 | if ( match.resnSlot ) { varExpr->resnSlots.push_back( match.resnSlot ); } |
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[6d6e829] | 221 | |
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[0b00df0] | 222 | // place newly-inferred assertion in proper place in cache |
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| 223 | inferred[ info.resnSlot ][ decl->get_uniqueId() ] = ParamEntry{ |
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[9aaacc27] | 224 | candidate->get_uniqueId(), match.adjType->clone(), decl->get_type()->clone(), |
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| 225 | varExpr }; |
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[6d6e829] | 226 | } |
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| 227 | |
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| 228 | /// Adds a captured assertion to the symbol table |
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| 229 | void addToIndexer( AssertionSet &assertSet, SymTab::Indexer &indexer ) { |
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[e1f7eef] | 230 | for ( auto& i : assertSet ) { |
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| 231 | if ( i.second.isUsed ) { |
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| 232 | indexer.addId( i.first ); |
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[6d6e829] | 233 | } |
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| 234 | } |
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| 235 | } |
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| 236 | |
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[0b00df0] | 237 | // in AlternativeFinder.cc; unique ID for assertion resolutions |
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| 238 | extern UniqueId globalResnSlot; |
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| 239 | |
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[6d6e829] | 240 | /// Resolve a single assertion, in context |
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[052cd71] | 241 | bool resolveAssertion( AssertionItem& assn, ResnState& resn ) { |
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[6d6e829] | 242 | // skip unused assertions |
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| 243 | if ( ! assn.info.isUsed ) return true; |
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| 244 | |
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[052cd71] | 245 | // lookup candidates for this assertion |
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| 246 | std::list< SymTab::Indexer::IdData > candidates; |
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| 247 | resn.indexer.lookupId( assn.decl->name, candidates ); |
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| 248 | |
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| 249 | // find the candidates that unify with the desired type |
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| 250 | CandidateList matches; |
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| 251 | for ( const auto& cdata : candidates ) { |
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| 252 | DeclarationWithType* candidate = cdata.id; |
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| 253 | |
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| 254 | // build independent unification context for candidate |
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| 255 | AssertionSet have, newNeed; |
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| 256 | TypeEnvironment newEnv{ resn.alt.env }; |
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| 257 | OpenVarSet newOpenVars{ resn.alt.openVars }; |
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| 258 | Type* adjType = candidate->get_type()->clone(); |
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| 259 | adjustExprType( adjType, newEnv, resn.indexer ); |
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| 260 | renameTyVars( adjType ); |
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| 261 | |
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| 262 | // keep unifying candidates |
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| 263 | if ( unify( assn.decl->get_type(), adjType, newEnv, newNeed, have, newOpenVars, |
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| 264 | resn.indexer ) ) { |
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| 265 | // set up binding slot for recursive assertions |
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| 266 | UniqueId crntResnSlot = 0; |
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| 267 | if ( ! newNeed.empty() ) { |
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| 268 | crntResnSlot = ++globalResnSlot; |
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| 269 | for ( auto& a : newNeed ) { |
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| 270 | a.second.resnSlot = crntResnSlot; |
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[0b00df0] | 271 | } |
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[2fd9f24] | 272 | } |
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[e1f7eef] | 273 | |
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[052cd71] | 274 | matches.emplace_back( cdata, adjType, std::move(newEnv), std::move(have), |
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| 275 | std::move(newNeed), std::move(newOpenVars), crntResnSlot ); |
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| 276 | } else { |
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| 277 | delete adjType; |
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| 278 | } |
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[6d6e829] | 279 | } |
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| 280 | |
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| 281 | // break if no suitable assertion |
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| 282 | if ( matches.empty() ) return false; |
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| 283 | |
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| 284 | // defer if too many suitable assertions |
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| 285 | if ( matches.size() > 1 ) { |
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[052cd71] | 286 | resn.deferred.emplace_back( assn.decl, assn.info, std::move(matches) ); |
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[6d6e829] | 287 | return true; |
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| 288 | } |
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| 289 | |
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| 290 | // otherwise bind current match in ongoing scope |
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| 291 | AssnCandidate& match = matches.front(); |
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| 292 | addToIndexer( match.have, resn.indexer ); |
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| 293 | resn.newNeed.insert( match.need.begin(), match.need.end() ); |
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[052cd71] | 294 | resn.alt.env = std::move(match.env); |
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| 295 | resn.alt.openVars = std::move(match.openVars); |
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[6d6e829] | 296 | |
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[0b00df0] | 297 | bindAssertion( assn.decl, assn.info, resn.alt, match, resn.inferred ); |
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[6d6e829] | 298 | return true; |
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| 299 | } |
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| 300 | |
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[0b00df0] | 301 | /// Associates inferred parameters with an expression |
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| 302 | struct InferMatcher { |
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| 303 | InferCache& inferred; |
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| 304 | |
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| 305 | InferMatcher( InferCache& inferred ) : inferred( inferred ) {} |
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| 306 | |
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| 307 | Expression* postmutate( Expression* expr ) { |
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[40290497] | 308 | // defer missing inferred parameters until they are hopefully found later |
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| 309 | std::vector<UniqueId> missingSlots; |
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[0b00df0] | 310 | // place inferred parameters into resolution slots |
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| 311 | for ( UniqueId slot : expr->resnSlots ) { |
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| 312 | // fail if no matching parameters found |
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[40290497] | 313 | auto it = inferred.find( slot ); |
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| 314 | if ( it == inferred.end() ) { |
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| 315 | missingSlots.push_back( slot ); |
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| 316 | continue; |
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| 317 | } |
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| 318 | InferredParams& inferParams = it->second; |
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[0b00df0] | 319 | |
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| 320 | // place inferred parameters into proper place in expression |
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| 321 | for ( auto& entry : inferParams ) { |
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| 322 | // recurse on inferParams of resolved expressions |
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| 323 | entry.second.expr = postmutate( entry.second.expr ); |
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| 324 | // xxx - look at entry.second.inferParams? |
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| 325 | expr->inferParams[ entry.first ] = entry.second; |
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| 326 | } |
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| 327 | } |
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| 328 | |
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| 329 | // clear resolution slots and return |
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[40290497] | 330 | expr->resnSlots.swap( missingSlots ); |
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[0b00df0] | 331 | return expr; |
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| 332 | } |
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| 333 | }; |
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| 334 | |
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| 335 | void finalizeAssertions( Alternative& alt, InferCache& inferred, AltList& out ) { |
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| 336 | PassVisitor<InferMatcher> matcher{ inferred }; |
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| 337 | alt.expr = alt.expr->acceptMutator( matcher ); |
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| 338 | out.emplace_back( alt ); |
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| 339 | } |
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| 340 | |
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| 341 | /// Limit to depth of recursion of assertion satisfaction |
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[6d6e829] | 342 | static const int recursionLimit = /* 10 */ 4; |
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| 343 | |
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[4d2d45f9] | 344 | void resolveAssertions( Alternative& alt, const SymTab::Indexer& indexer, AltList& out, std::list<std::string>& errors ) { |
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[6d6e829] | 345 | // finish early if no assertions to resolve |
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| 346 | if ( alt.need.empty() ) { |
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| 347 | out.emplace_back( alt ); |
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| 348 | return; |
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| 349 | } |
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| 350 | |
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| 351 | // build list of possible resolutions |
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| 352 | using ResnList = std::vector<ResnState>; |
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| 353 | SymTab::Indexer root_indexer{ indexer }; |
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| 354 | ResnList resns{ ResnState{ alt, root_indexer } }; |
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| 355 | ResnList new_resns{}; |
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| 356 | |
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| 357 | // resolve assertions in breadth-first-order up to a limited number of levels deep |
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| 358 | for ( unsigned level = 0; level < recursionLimit; ++level ) { |
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| 359 | // scan over all mutually-compatible resolutions |
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| 360 | for ( auto& resn : resns ) { |
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| 361 | // make initial pass at matching assertions |
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| 362 | for ( auto& assn : resn.need ) { |
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| 363 | // fail early if any assertion is not resolvable |
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[052cd71] | 364 | if ( ! resolveAssertion( assn, resn ) ) { |
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[4d2d45f9] | 365 | Indenter tabs{ Indenter::tabsize, 3 }; |
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| 366 | std::ostringstream ss; |
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| 367 | ss << tabs << "Unsatisfiable alternative:\n"; |
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| 368 | resn.alt.print( ss, ++tabs ); |
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| 369 | ss << --tabs << "Could not satisfy assertion:\n"; |
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| 370 | assn.decl->print( ss, ++tabs ); |
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| 371 | |
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| 372 | errors.emplace_back( ss.str() ); |
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| 373 | goto nextResn; |
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| 374 | } |
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[6d6e829] | 375 | } |
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| 376 | |
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| 377 | if ( resn.deferred.empty() ) { |
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| 378 | // either add successful match or push back next state |
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| 379 | if ( resn.newNeed.empty() ) { |
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[0b00df0] | 380 | finalizeAssertions( resn.alt, resn.inferred, out ); |
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[6d6e829] | 381 | } else { |
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| 382 | new_resns.emplace_back( std::move(resn), IterateState ); |
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| 383 | } |
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| 384 | } else { |
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[b3bd772] | 385 | // resolve deferred assertions by mutual compatibility |
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[6d6e829] | 386 | std::vector<CandidateEnvMerger::OutType> compatible = filterCombos( |
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| 387 | resn.deferred, |
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| 388 | CandidateEnvMerger{ resn.alt.env, resn.alt.openVars, resn.indexer } ); |
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[4d2d45f9] | 389 | // fail early if no mutually-compatible assertion satisfaction |
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| 390 | if ( compatible.empty() ) { |
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| 391 | Indenter tabs{ Indenter::tabsize, 3 }; |
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| 392 | std::ostringstream ss; |
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| 393 | ss << tabs << "Unsatisfiable alternative:\n"; |
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| 394 | resn.alt.print( ss, ++tabs ); |
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| 395 | ss << --tabs << "No mutually-compatible satisfaction for assertions:\n"; |
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| 396 | ++tabs; |
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| 397 | for ( const auto& d : resn.deferred ) { |
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[052cd71] | 398 | d.decl->print( ss, tabs ); |
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[4d2d45f9] | 399 | } |
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| 400 | |
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| 401 | errors.emplace_back( ss.str() ); |
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| 402 | goto nextResn; |
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| 403 | } |
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[b3bd772] | 404 | // sort by cost |
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| 405 | CandidateCost coster{ resn.indexer }; |
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| 406 | std::sort( compatible.begin(), compatible.end(), coster ); |
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| 407 | |
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| 408 | // keep map of detected options |
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| 409 | std::unordered_map<std::string, Cost> found; |
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| 410 | for ( auto& compat : compatible ) { |
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| 411 | // filter by environment-adjusted result type, keep only cheapest option |
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| 412 | Type* resType = alt.expr->result->clone(); |
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| 413 | compat.env.apply( resType ); |
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| 414 | // skip if cheaper alternative already processed with same result type |
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| 415 | Cost resCost = coster.get( compat ); |
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| 416 | auto it = found.emplace( SymTab::Mangler::mangleType( resType ), resCost ); |
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[aeb8f70] | 417 | delete resType; |
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[b3bd772] | 418 | if ( it.second == false && it.first->second < resCost ) continue; |
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| 419 | |
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| 420 | // proceed with resolution step |
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[6d6e829] | 421 | ResnState new_resn = resn; |
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| 422 | |
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| 423 | // add compatible assertions to new resolution state |
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| 424 | for ( DeferRef r : compat.assns ) { |
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| 425 | AssnCandidate match = r.match; |
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| 426 | addToIndexer( match.have, new_resn.indexer ); |
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| 427 | new_resn.newNeed.insert( match.need.begin(), match.need.end() ); |
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| 428 | |
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[052cd71] | 429 | bindAssertion( r.decl, r.info, new_resn.alt, match, new_resn.inferred ); |
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[6d6e829] | 430 | } |
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| 431 | |
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| 432 | // set mutual environment into resolution state |
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| 433 | new_resn.alt.env = std::move(compat.env); |
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| 434 | new_resn.alt.openVars = std::move(compat.openVars); |
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| 435 | |
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| 436 | // either add sucessful match or push back next state |
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| 437 | if ( new_resn.newNeed.empty() ) { |
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[0b00df0] | 438 | finalizeAssertions( new_resn.alt, new_resn.inferred, out ); |
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[6d6e829] | 439 | } else { |
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| 440 | new_resns.emplace_back( std::move(new_resn), IterateState ); |
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| 441 | } |
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| 442 | } |
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| 443 | } |
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| 444 | nextResn:; } |
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| 445 | |
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| 446 | // finish or reset for next round |
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| 447 | if ( new_resns.empty() ) return; |
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| 448 | resns.swap( new_resns ); |
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| 449 | new_resns.clear(); |
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| 450 | } |
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| 451 | |
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| 452 | // exceeded recursion limit if reaches here |
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| 453 | if ( out.empty() ) { |
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| 454 | SemanticError( alt.expr->location, "Too many recursive assertions" ); |
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| 455 | } |
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| 456 | } |
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| 457 | } // namespace ResolvExpr |
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| 458 | |
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| 459 | // Local Variables: // |
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| 460 | // tab-width: 4 // |
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| 461 | // mode: c++ // |
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| 462 | // compile-command: "make install" // |
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| 463 | // End: // |
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