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/****************************************************************************** |
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* Top contributors (to current version): |
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* Yoni Zohar, Andres Noetzli, Aina Niemetz |
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* |
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* This file is part of the cvc5 project. |
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* |
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* Copyright (c) 2009-2021 by the authors listed in the file AUTHORS |
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* in the top-level source directory and their institutional affiliations. |
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* All rights reserved. See the file COPYING in the top-level source |
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* directory for licensing information. |
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* **************************************************************************** |
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* |
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* The foreign_theory_rewrite preprocessing pass. |
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* |
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* Simplifies nodes of one theory using rewrites from another. |
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*/ |
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#include "preprocessing/passes/foreign_theory_rewrite.h" |
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#include "expr/node_traversal.h" |
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#include "preprocessing/assertion_pipeline.h" |
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#include "preprocessing/preprocessing_pass_context.h" |
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#include "theory/rewriter.h" |
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#include "theory/strings/arith_entail.h" |
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namespace cvc5 { |
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namespace preprocessing { |
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namespace passes { |
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using namespace cvc5::theory; |
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ForeignTheoryRewrite::ForeignTheoryRewrite(PreprocessingPassContext* preprocContext) |
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: PreprocessingPass(preprocContext, "foreign-theory-rewrite"), |
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d_cache(preprocContext->getUserContext()){}; |
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Node ForeignTheoryRewrite::simplify(Node n) |
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{ |
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std::vector<Node> toVisit; |
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n = Rewriter::rewrite(n); |
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toVisit.push_back(n); |
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// traverse n and rewrite until fixpoint |
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while (!toVisit.empty()) |
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{ |
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Node current = toVisit.back(); |
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// split according to three cases: |
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// 1. We have not visited this node |
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// 2. We visited it but did not process it |
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// 3. We already processed and cached the node |
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if (d_cache.find(current) == d_cache.end()) |
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{ |
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// current is seen for the first time. |
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// mark it by assigning a null node |
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// and add its children to toVisit |
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d_cache[current] = Node(); |
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toVisit.insert(toVisit.end(), current.begin(), current.end()); |
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} |
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else if (d_cache[current].get().isNull()) |
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{ |
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// current was seen but was not processed. |
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// (a) remove from toVisit |
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toVisit.pop_back(); |
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// (b) Reconstruct it with processed children |
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std::vector<Node> processedChildren; |
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for (Node child : current) |
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{ |
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Assert(d_cache.find(child) != d_cache.end()); |
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Assert(!d_cache[child].get().isNull()); |
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processedChildren.push_back(d_cache[child]); |
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} |
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Node reconstruction = reconstructNode(current, processedChildren); |
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// (c) process the node and store the result in the cache |
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Node result = foreignRewrite(reconstruction); |
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d_cache[current] = result; |
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// (d) add the result to toVisit, unless it is the same as current |
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if (current != result) |
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{ |
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toVisit.push_back(result); |
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} |
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} |
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else |
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{ |
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// current was already processed |
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// remove from toVisit and skip |
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toVisit.pop_back(); |
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} |
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} |
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return d_cache[n]; |
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} |
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Node ForeignTheoryRewrite::foreignRewrite(Node n) |
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{ |
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// n is a rewritten node, and so GT, LT, LEQ |
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// should have been eliminated |
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Assert(n.getKind() != kind::GT); |
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Assert(n.getKind() != kind::LT); |
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Assert(n.getKind() != kind::LEQ); |
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// apply rewrites according to the structure of n |
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if (n.getKind() == kind::GEQ) |
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{ |
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return rewriteStringsGeq(n); |
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} |
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return n; |
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} |
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Node ForeignTheoryRewrite::rewriteStringsGeq(Node n) |
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{ |
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// check if the node can be simplified to true |
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if (theory::strings::ArithEntail::check(n[0], n[1], false)) |
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{ |
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return NodeManager::currentNM()->mkConst(true); |
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} |
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return n; |
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} |
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Node ForeignTheoryRewrite::reconstructNode(Node originalNode, |
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std::vector<Node> newChildren) |
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{ |
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// Nodes with no children are reconstructed to themselves |
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if (originalNode.getNumChildren() == 0) |
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{ |
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Assert(newChildren.empty()); |
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return originalNode; |
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} |
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// re-build the node with the same kind and new children |
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kind::Kind_t k = originalNode.getKind(); |
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NodeBuilder builder(k); |
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// special case for parameterized nodes |
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if (originalNode.getMetaKind() == kind::metakind::PARAMETERIZED) |
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{ |
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builder << originalNode.getOperator(); |
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} |
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// reconstruction |
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for (Node child : newChildren) |
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{ |
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builder << child; |
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} |
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return builder.constructNode(); |
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} |
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PreprocessingPassResult ForeignTheoryRewrite::applyInternal( |
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AssertionPipeline* assertionsToPreprocess) |
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{ |
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for (unsigned i = 0; i < assertionsToPreprocess->size(); ++i) |
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{ |
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assertionsToPreprocess->replace( |
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i, Rewriter::rewrite(simplify((*assertionsToPreprocess)[i]))); |
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} |
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return PreprocessingPassResult::NO_CONFLICT; |
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} |
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} // namespace passes |
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} // namespace preprocessing |
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} // namespace cvc5 |