path: root/src/theory/rewriter.cpp

/******************************************************************************
 * Top contributors (to current version):
 *   Andrew Reynolds, Andres Noetzli, Dejan Jovanovic
 *
 * This file is part of the cvc5 project.
 *
 * Copyright (c) 2009-2021 by the authors listed in the file AUTHORS
 * in the top-level source directory and their institutional affiliations.
 * All rights reserved.  See the file COPYING in the top-level source
 * directory for licensing information.
 * ****************************************************************************
 *
 * The Rewriter class.
 */

#include "theory/rewriter.h"

#include "options/theory_options.h"
#include "proof/conv_proof_generator.h"
#include "smt/smt_statistics_registry.h"
#include "smt/solver_engine.h"
#include "smt/solver_engine_scope.h"
#include "theory/builtin/proof_checker.h"
#include "theory/evaluator.h"
#include "theory/quantifiers/extended_rewrite.h"
#include "theory/rewriter_tables.h"
#include "theory/theory.h"
#include "util/resource_manager.h"

using namespace std;

namespace cvc5 {
namespace theory {

/** Attribute true for nodes that have been rewritten with proofs enabled */
struct RewriteWithProofsAttributeId
{
};
typedef expr::Attribute<RewriteWithProofsAttributeId, bool>
    RewriteWithProofsAttribute;

// Note that this function is a simplified version of Theory::theoryOf for
// (type-based) theoryOfMode. We expand and simplify it here for the sake of
// efficiency.
static TheoryId theoryOf(TNode node) {
  if (node.getKind() == kind::EQUAL)
  {
    // Equality is owned by the theory that owns the domain
    return Theory::theoryOf(node[0].getType());
  }
  // Regular nodes are owned by the kind
  return kindToTheoryId(node.getKind());
}

/**
 * TheoryEngine::rewrite() keeps a stack of things that are being pre-
 * and post-rewritten.  Each element of the stack is a
 * RewriteStackElement.
 */
struct RewriteStackElement {
  /**
   * Construct a fresh stack element.
   */
  RewriteStackElement(TNode node, TheoryId theoryId)
      : d_node(node),
        d_original(node),
        d_theoryId(theoryId),
        d_originalTheoryId(theoryId),
        d_nextChild(0)
  {
  }

  TheoryId getTheoryId() { return static_cast<TheoryId>(d_theoryId); }

  TheoryId getOriginalTheoryId()
  {
    return static_cast<TheoryId>(d_originalTheoryId);
  }

  /** The node we're currently rewriting */
  Node d_node;
  /** Original node (either the unrewritten node or the node after prerewriting)
   */
  Node d_original;
  /** Id of the theory that's currently rewriting this node */
  unsigned d_theoryId : 8;
  /** Id of the original theory that started the rewrite */
  unsigned d_originalTheoryId : 8;
  /** Index of the child this node is done rewriting */
  unsigned d_nextChild : 32;
  /** Builder for this node */
  NodeBuilder d_builder;
};


Node Rewriter::rewrite(TNode node) {
  if (node.getNumChildren() == 0)
  {
    // Nodes with zero children should never change via rewriting. We return
    // eagerly for the sake of efficiency here.
    return node;
  }
  return getInstance()->rewriteTo(theoryOf(node), node);
}

Node Rewriter::callExtendedRewrite(TNode node, bool aggr)
{
  return getInstance()->extendedRewrite(node, aggr);
}

Node Rewriter::extendedRewrite(TNode node, bool aggr)
{
  quantifiers::ExtendedRewriter er(*this, aggr);
  return er.extendedRewrite(node);
}

TrustNode Rewriter::rewriteWithProof(TNode node,
                                     bool isExtEq)
{
  // must set the proof checker before calling this
  Assert(d_tpg != nullptr);
  if (isExtEq)
  {
    // theory rewriter is responsible for rewriting the equality
    TheoryRewriter* tr = getInstance()->d_theoryRewriters[theoryOf(node)];
    Assert(tr != nullptr);
    return tr->rewriteEqualityExtWithProof(node);
  }
  Node ret = getInstance()->rewriteTo(theoryOf(node), node, d_tpg.get());
  return TrustNode::mkTrustRewrite(node, ret, d_tpg.get());
}

void Rewriter::setProofNodeManager(ProofNodeManager* pnm)
{
  // if not already initialized with proof support
  if (d_tpg == nullptr)
  {
    Trace("rewriter") << "Rewriter::setProofNodeManager" << std::endl;
    // the rewriter is staticly determinstic, thus use static cache policy
    // for the term conversion proof generator
    d_tpg.reset(new TConvProofGenerator(pnm,
                                        nullptr,
                                        TConvPolicy::FIXPOINT,
                                        TConvCachePolicy::STATIC,
                                        "Rewriter::TConvProofGenerator"));
  }
}

Node Rewriter::rewriteEqualityExt(TNode node)
{
  Assert(node.getKind() == kind::EQUAL);
  // note we don't force caching of this method currently
  return d_theoryRewriters[theoryOf(node)]->rewriteEqualityExt(node);
}

void Rewriter::registerTheoryRewriter(theory::TheoryId tid,
                                      TheoryRewriter* trew)
{
  d_theoryRewriters[tid] = trew;
}

TheoryRewriter* Rewriter::getTheoryRewriter(theory::TheoryId theoryId)
{
  return d_theoryRewriters[theoryId];
}

Rewriter* Rewriter::getInstance()
{
  return smt::currentSolverEngine()->getRewriter();
}

Node Rewriter::rewriteTo(theory::TheoryId theoryId,
                         Node node,
                         TConvProofGenerator* tcpg)
{
  RewriteWithProofsAttribute rpfa;
#ifdef CVC5_ASSERTIONS
  bool isEquality = node.getKind() == kind::EQUAL && (!node[0].getType().isBoolean());

  if (d_rewriteStack == nullptr)
  {
    d_rewriteStack.reset(new std::unordered_set<Node>());
  }
#endif

  Trace("rewriter") << "Rewriter::rewriteTo(" << theoryId << "," << node << ")"<< std::endl;

  // Check if it's been cached already
  Node cached = getPostRewriteCache(theoryId, node);
  if (!cached.isNull() && (tcpg == nullptr || node.getAttribute(rpfa)))
  {
    return cached;
  }

  // Put the node on the stack in order to start the "recursive" rewrite
  vector<RewriteStackElement> rewriteStack;
  rewriteStack.push_back(RewriteStackElement(node, theoryId));

  // Rewrite until the stack is empty
  for (;;){
    if (d_resourceManager != nullptr)
    {
      d_resourceManager->spendResource(Resource::RewriteStep);
    }

    // Get the top of the recursion stack
    RewriteStackElement& rewriteStackTop = rewriteStack.back();

    Trace("rewriter") << "Rewriter::rewriting: "
                      << rewriteStackTop.getTheoryId() << ","
                      << rewriteStackTop.d_node << std::endl;

    // Before rewriting children we need to do a pre-rewrite of the node
    if (rewriteStackTop.d_nextChild == 0)
    {
      // Check if the pre-rewrite has already been done (it's in the cache)
      cached = getPreRewriteCache(rewriteStackTop.getTheoryId(),
                                  rewriteStackTop.d_node);
      if (cached.isNull()
          || (tcpg != nullptr && !rewriteStackTop.d_node.getAttribute(rpfa)))
      {
        // Rewrite until fix-point is reached
        for(;;) {
          // Perform the pre-rewrite
          RewriteResponse response = preRewrite(
              rewriteStackTop.getTheoryId(), rewriteStackTop.d_node, tcpg);

          // Put the rewritten node to the top of the stack
          rewriteStackTop.d_node = response.d_node;
          TheoryId newTheory = theoryOf(rewriteStackTop.d_node);
          // In the pre-rewrite, if changing theories, we just call the other theories pre-rewrite
          if (newTheory == rewriteStackTop.getTheoryId()
              && response.d_status == REWRITE_DONE)
          {
            break;
          }
          rewriteStackTop.d_theoryId = newTheory;
        }

        // Cache the rewrite
        setPreRewriteCache(rewriteStackTop.getOriginalTheoryId(),
                           rewriteStackTop.d_original,
                           rewriteStackTop.d_node);
      }
      // Otherwise we're have already been pre-rewritten (in pre-rewrite cache)
      else {
        // Continue with the cached version
        rewriteStackTop.d_node = cached;
        rewriteStackTop.d_theoryId = theoryOf(cached);
      }
    }

    rewriteStackTop.d_original = rewriteStackTop.d_node;
    // Now it's time to rewrite the children, check if this has already been done
    cached = getPostRewriteCache(rewriteStackTop.getTheoryId(),
                                 rewriteStackTop.d_node);
    // If not, go through the children
    if (cached.isNull()
        || (tcpg != nullptr && !rewriteStackTop.d_node.getAttribute(rpfa)))
    {
      // The child we need to rewrite
      unsigned child = rewriteStackTop.d_nextChild++;

      // To build the rewritten expression we set up the builder
      if(child == 0) {
        if (rewriteStackTop.d_node.getNumChildren() > 0)
        {
          // The children will add themselves to the builder once they're done
          rewriteStackTop.d_builder << rewriteStackTop.d_node.getKind();
          kind::MetaKind metaKind = rewriteStackTop.d_node.getMetaKind();
          if (metaKind == kind::metakind::PARAMETERIZED) {
            rewriteStackTop.d_builder << rewriteStackTop.d_node.getOperator();
          }
        }
      }

      // Process the next child
      if (child < rewriteStackTop.d_node.getNumChildren())
      {
        // The child node
        Node childNode = rewriteStackTop.d_node[child];
        // Push the rewrite request to the stack (NOTE: rewriteStackTop might be a bad reference now)
        rewriteStack.push_back(RewriteStackElement(childNode, theoryOf(childNode)));
        // Go on with the rewriting
        continue;
      }

      // Incorporate the children if necessary
      if (rewriteStackTop.d_node.getNumChildren() > 0)
      {
        Node rewritten = rewriteStackTop.d_builder;
        rewriteStackTop.d_node = rewritten;
        rewriteStackTop.d_theoryId = theoryOf(rewriteStackTop.d_node);
      }

      // Done with all pre-rewriting, so let's do the post rewrite
      for(;;) {
        // Do the post-rewrite
        RewriteResponse response = postRewrite(
            rewriteStackTop.getTheoryId(), rewriteStackTop.d_node, tcpg);

        // We continue with the response we got
        TheoryId newTheoryId = theoryOf(response.d_node);
        if (newTheoryId != rewriteStackTop.getTheoryId()
            || response.d_status == REWRITE_AGAIN_FULL)
        {
          // In the post rewrite if we've changed theories, we must do a full rewrite
          Assert(response.d_node != rewriteStackTop.d_node);
          //TODO: this is not thread-safe - should make this assertion dependent on sequential build
#ifdef CVC5_ASSERTIONS
          Assert(d_rewriteStack->find(response.d_node)
                 == d_rewriteStack->end());
          d_rewriteStack->insert(response.d_node);
#endif
          Node rewritten = rewriteTo(newTheoryId, response.d_node, tcpg);
          rewriteStackTop.d_node = rewritten;
#ifdef CVC5_ASSERTIONS
          d_rewriteStack->erase(response.d_node);
#endif
          break;
        }
        else if (response.d_status == REWRITE_DONE)
        {
#ifdef CVC5_ASSERTIONS
          RewriteResponse r2 =
              d_theoryRewriters[newTheoryId]->postRewrite(response.d_node);
          Assert(r2.d_node == response.d_node)
              << r2.d_node << " != " << response.d_node;
#endif
          rewriteStackTop.d_node = response.d_node;
          break;
        }
        // Check for trivial rewrite loops of size 1 or 2
        Assert(response.d_node != rewriteStackTop.d_node);
        Assert(d_theoryRewriters[rewriteStackTop.getTheoryId()]
                   ->postRewrite(response.d_node)
                   .d_node
               != rewriteStackTop.d_node);
        rewriteStackTop.d_node = response.d_node;
      }

      // We're done with the post rewrite, so we add to the cache
      if (tcpg != nullptr)
      {
        // if proofs are enabled, mark that we've rewritten with proofs
        rewriteStackTop.d_original.setAttribute(rpfa, true);
        if (!cached.isNull())
        {
          // We may have gotten a different node, due to non-determinism in
          // theory rewriters (e.g. quantifiers rewriter which introduces
          // fresh BOUND_VARIABLE). This can happen if we wrote once without
          // proofs and then rewrote again with proofs.
          if (rewriteStackTop.d_node != cached)
          {
            Trace("rewriter-proof") << "WARNING: Rewritten forms with and "
                                       "without proofs were not equivalent"
                                    << std::endl;
            Trace("rewriter-proof")
                << "   original: " << rewriteStackTop.d_original << std::endl;
            Trace("rewriter-proof")
                << "with proofs: " << rewriteStackTop.d_node << std::endl;
            Trace("rewriter-proof") << " w/o proofs: " << cached << std::endl;
            Node eq = rewriteStackTop.d_node.eqNode(cached);
            // we make this a post-rewrite, since we are processing a node that
            // has finished post-rewriting above
            tcpg->addRewriteStep(rewriteStackTop.d_node,
                                 cached,
                                 PfRule::TRUST_REWRITE,
                                 {},
                                 {eq},
                                 false);
            // don't overwrite the cache, should be the same
            rewriteStackTop.d_node = cached;
          }
        }
      }
      setPostRewriteCache(rewriteStackTop.getOriginalTheoryId(),
                          rewriteStackTop.d_original,
                          rewriteStackTop.d_node);
    }
    else
    {
      // We were already in cache, so just remember it
      rewriteStackTop.d_node = cached;
      rewriteStackTop.d_theoryId = theoryOf(cached);
    }

    // If this is the last node, just return
    if (rewriteStack.size() == 1) {
      Assert(!isEquality || rewriteStackTop.d_node.getKind() == kind::EQUAL
             || rewriteStackTop.d_node.isConst());
      return rewriteStackTop.d_node;
    }

    // We're done with this node, append it to the parent
    rewriteStack[rewriteStack.size() - 2].d_builder << rewriteStackTop.d_node;
    rewriteStack.pop_back();
  }

  Unreachable();
} /* Rewriter::rewriteTo() */

RewriteResponse Rewriter::preRewrite(theory::TheoryId theoryId,
                                     TNode n,
                                     TConvProofGenerator* tcpg)
{
  if (tcpg != nullptr)
  {
    // call the trust rewrite response interface
    TrustRewriteResponse tresponse =
        d_theoryRewriters[theoryId]->preRewriteWithProof(n);
    // process the trust rewrite response: store the proof step into
    // tcpg if necessary and then convert to rewrite response.
    return processTrustRewriteResponse(theoryId, tresponse, true, tcpg);
  }
  return d_theoryRewriters[theoryId]->preRewrite(n);
}

RewriteResponse Rewriter::postRewrite(theory::TheoryId theoryId,
                                      TNode n,
                                      TConvProofGenerator* tcpg)
{
  if (tcpg != nullptr)
  {
    // same as above, for post-rewrite
    TrustRewriteResponse tresponse =
        d_theoryRewriters[theoryId]->postRewriteWithProof(n);
    return processTrustRewriteResponse(theoryId, tresponse, false, tcpg);
  }
  return d_theoryRewriters[theoryId]->postRewrite(n);
}

RewriteResponse Rewriter::processTrustRewriteResponse(
    theory::TheoryId theoryId,
    const TrustRewriteResponse& tresponse,
    bool isPre,
    TConvProofGenerator* tcpg)
{
  Assert(tcpg != nullptr);
  TrustNode trn = tresponse.d_node;
  Assert(trn.getKind() == TrustNodeKind::REWRITE);
  Node proven = trn.getProven();
  if (proven[0] != proven[1])
  {
    ProofGenerator* pg = trn.getGenerator();
    if (pg == nullptr)
    {
      Node tidn = builtin::BuiltinProofRuleChecker::mkTheoryIdNode(theoryId);
      // add small step trusted rewrite
      Node rid = mkMethodId(isPre ? MethodId::RW_REWRITE_THEORY_PRE
                                  : MethodId::RW_REWRITE_THEORY_POST);
      tcpg->addRewriteStep(proven[0],
                           proven[1],
                           PfRule::THEORY_REWRITE,
                           {},
                           {proven, tidn, rid},
                           isPre);
    }
    else
    {
      // store proven rewrite step
      tcpg->addRewriteStep(proven[0], proven[1], pg, isPre);
    }
  }
  return RewriteResponse(tresponse.d_status, trn.getNode());
}

void Rewriter::clearCaches()
{
#ifdef CVC5_ASSERTIONS
  d_rewriteStack.reset(nullptr);
#endif

  clearCachesInternal();
}

}  // namespace theory
}  // namespace cvc5