lib/Simplifier/PropagateEqualities.cpp - external/github.com/stp/stp - Git at Google

 /********************************************************************
  *
  * BEGIN DATE: November, 2005
  *
 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal
 in the Software without restriction, including without limitation the rights
 to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 copies of the Software, and to permit persons to whom the Software is
 furnished to do so, subject to the following conditions:

 The above copyright notice and this permission notice shall be included in
 all copies or substantial portions of the Software.

 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 THE SOFTWARE.
 ********************************************************************/

 #include "stp/Simplifier/PropagateEqualities.h"
 #include "stp/AbsRefineCounterExample/ArrayTransformer.h"
 #include "stp/Simplifier/Simplifier.h"
 #include <string>

 namespace stp
 {

 /* The search functions look for variables that can be expressed in terms of
  * variables.
  * The most obvious case it doesn't check for is NOT (OR (.. .. )).
  * I suspect this could take exponential time in the worst case, but on the
  * benchmarks I've tested,
  * it finishes in reasonable time.
  * The obvious way to speed it up (if required), is to create the RHS lazily.
  */

 // The old XOR code used to use updateSolverMap instead of
 // UpdateSubstitutionMap, I've no idea why.

 bool PropagateEqualities::searchXOR(const ASTNode& lhs, const ASTNode& rhs)
 {
   Kind k = lhs.GetKind();

   if (lhs == rhs)
     return true;

   if (k == SYMBOL)
     return simp->UpdateSubstitutionMap(
         lhs, rhs); // checks whether it's been solved for or loops.

   if (k == NOT)
     return searchXOR(lhs[0], nf->CreateNode(NOT, rhs));

   bool result = false;
   if (k == XOR)
     for (size_t i = 0; i < lhs.Degree(); i++)
     {
       ASTVec others;
       for (size_t j = 0; j < lhs.Degree(); j++)
         if (j != i)
           others.push_back(lhs[j]);

       others.push_back(rhs);
       assert(others.size() > 1);
       ASTNode new_rhs = nf->CreateNode(XOR, others);

       result = searchXOR(lhs[i], new_rhs);
       if (result)
         return result;
     }

   if (k == EQ && lhs[0].GetValueWidth() == 1)
   {
     bool result = searchTerm(
         lhs[0],
         nf->CreateTerm(ITE, 1, rhs, lhs[1], nf->CreateTerm(BVNOT, 1, lhs[1])));

     if (!result)
       result = searchTerm(lhs[1],
                           nf->CreateTerm(ITE, 1, rhs, lhs[0],
                                          nf->CreateTerm(BVNOT, 1, lhs[0])));
   }

   return result;
 }

 bool PropagateEqualities::searchTerm(const ASTNode& lhs, const ASTNode& rhs)
 {
   const unsigned width = lhs.GetValueWidth();

   if (lhs == rhs)
     return true;

   if (lhs.GetKind() == SYMBOL)
     return simp->UpdateSubstitutionMap(lhs, rhs); // checks whether it's been
                                                   // solved for, or if the RHS
                                                   // contains the LHS.

   if (lhs.GetKind() == BVUMINUS)
     return searchTerm(lhs[0], nf->CreateTerm(BVUMINUS, width, rhs));

   if (lhs.GetKind() == BVNOT)
     return searchTerm(lhs[0], nf->CreateTerm(BVNOT, width, rhs));

   if (lhs.GetKind() == BVXOR || lhs.GetKind() == BVPLUS)
     for (size_t i = 0; i < lhs.Degree(); i++)
     {
       ASTVec others;
       for (size_t j = 0; j < lhs.Degree(); j++)
         if (j != i)
           others.push_back(lhs[j]);

       ASTNode new_rhs;
       if (lhs.GetKind() == BVXOR)
       {
         others.push_back(rhs);
         assert(others.size() > 1);
         new_rhs = nf->CreateTerm(lhs.GetKind(), width, others);
       }
       else if (lhs.GetKind() == BVPLUS)
       {
         if (others.size() > 1)
           new_rhs = nf->CreateTerm(BVPLUS, width, others);
         else
           new_rhs = others[0];

         new_rhs = nf->CreateTerm(BVUMINUS, width, new_rhs);
         new_rhs = nf->CreateTerm(BVPLUS, width, new_rhs, rhs);
       }
       else
         FatalError("sdafasfsdf2q3234423");

       bool result = searchTerm(lhs[i], new_rhs);
       if (result)
         return true;
     }

   if (lhs.Degree() == 2 && lhs.GetKind() == BVMULT && lhs[0].isConstant() &&
       simp->BVConstIsOdd(lhs[0]))
     return searchTerm(lhs[1],
                       nf->CreateTerm(BVMULT, width,
                                      simp->MultiplicativeInverse(lhs[0]), rhs));

   return false;
 }

 // This doesn't rewrite changes through properly so needs to have a substitution
 // applied to its output.
 ASTNode PropagateEqualities::propagate(const ASTNode& a, ArrayTransformer* at)
 {
   ASTNode output;
   // if the variable has been solved for, then simply return it
   if (simp->InsideSubstitutionMap(a, output))
     return output;

   if (!alreadyVisited.insert(a.GetNodeNum()).second)
   {
     return a;
   }

   output = a;

   // traverse a and populate the SubstitutionMap
   const Kind k = a.GetKind();
   if (SYMBOL == k && BOOLEAN_TYPE == a.GetType())
   {
     bool updated = simp->UpdateSubstitutionMap(a, ASTTrue);
     output = updated ? ASTTrue : a;
   }
   else if (NOT == k)
   {
     bool updated = searchXOR(a[0], ASTFalse);
     output = updated ? ASTTrue : a;
   }
   else if (IFF == k || EQ == k)
   {
     const ASTVec& c = a.GetChildren();

     if (c[0] == c[1])
       return ASTTrue;

     bool updated = simp->UpdateSubstitutionMap(c[0], c[1]);

     if (updated)
     {
       // fill the arrayname readindices vector if e0 is a
       // READ(Arr,index) and index is a BVCONST
       int to;
       if ((to = TermOrder(c[0], c[1])) == 1 && c[0].GetKind() == READ)
         at->FillUp_ArrReadIndex_Vec(c[0], c[1]);
       else if (to == -1 && c[1].GetKind() == READ)
         at->FillUp_ArrReadIndex_Vec(c[1], c[0]);
     }

     if (!updated)
       updated = searchTerm(c[0], c[1]);

     if (!updated)
       updated = searchTerm(c[1], c[0]);

     output = updated ? ASTTrue : a;
   }
   else if (XOR == k)
   {
     bool updated = searchXOR(a, ASTTrue);
     output = updated ? ASTTrue : a;

     if (updated)
       return output;

 // The below block should be subsumed by the searchXOR function which
 // generalises it.
 // So the below block should never do anything..
 #ifndef NDEBUG
     if (a.Degree() != 2)
       return output;

     int to = TermOrder(a[0], a[1]);
     if (0 == to)
     {
       if (a[0].GetKind() == NOT && a[0][0].GetKind() == EQ &&
           a[0][0][0].GetValueWidth() == 1 && a[0][0][1].GetKind() == SYMBOL)
       {
         // (XOR (NOT(= (1 v)))  ... )
         const ASTNode& symbol = a[0][0][1];
         const ASTNode newN = nf->CreateTerm(
             ITE, 1, a[1], a[0][0][0], nf->CreateTerm(BVNOT, 1, a[0][0][0]));

         if (simp->UpdateSolverMap(symbol, newN))
         {
           assert(false);
           output = ASTTrue;
         }
       }
       else if (a[1].GetKind() == NOT && a[1][0].GetKind() == EQ &&
                a[1][0][0].GetValueWidth() == 1 &&
                a[1][0][1].GetKind() == SYMBOL)
       {
         const ASTNode& symbol = a[1][0][1];
         const ASTNode newN = nf->CreateTerm(
             ITE, 1, a[0], a[1][0][0], nf->CreateTerm(BVNOT, 1, a[1][0][0]));

         if (simp->UpdateSolverMap(symbol, newN))
         {
           assert(false);
           output = ASTTrue;
         }
       }
       else if (a[0].GetKind() == EQ && a[0][0].GetValueWidth() == 1 &&
                a[0][1].GetKind() == SYMBOL)
       {
         // XOR ((= 1 v) ... )

         const ASTNode& symbol = a[0][1];
         const ASTNode newN = nf->CreateTerm(
             ITE, 1, a[1], nf->CreateTerm(BVNOT, 1, a[0][0]), a[0][0]);

         if (simp->UpdateSolverMap(symbol, newN))
         {
           assert(false);
           output = ASTTrue;
         }
       }
       else if (a[1].GetKind() == EQ && a[1][0].GetValueWidth() == 1 &&
                a[1][1].GetKind() == SYMBOL)
       {
         const ASTNode& symbol = a[1][1];
         const ASTNode newN = nf->CreateTerm(
             ITE, 1, a[0], nf->CreateTerm(BVNOT, 1, a[1][0]), a[1][0]);

         if (simp->UpdateSolverMap(symbol, newN))
         {
           assert(false);
           output = ASTTrue;
         }
       }
       else
         return output;
     }
     else
     {
       ASTNode symbol, rhs;
       if (to == 1)
       {
         symbol = a[0];
         rhs = a[1];
       }
       else
       {
         symbol = a[1];
         rhs = a[0];
       }

       assert(symbol.GetKind() == SYMBOL);

       if (simp->UpdateSolverMap(symbol, nf->CreateNode(NOT, rhs)))
       {
         assert(false);
         output = ASTTrue;
       }
     }
 #endif
   }
   else if (AND == k)
   {
     const ASTVec& c = a.GetChildren();
     ASTVec o;
     o.reserve(c.size());

     for (ASTVec::const_iterator it = c.begin(), itend = c.end(); it != itend;
          it++)
     {
       if (always_true)
         simp->UpdateAlwaysTrueFormSet(*it);
       ASTNode aaa = propagate(*it, at);

       if (ASTTrue != aaa)
       {
         if (ASTFalse == aaa)
           return ASTFalse;
         else
           o.push_back(aaa);
       }
     }
     if (o.size() == 0)
       output = ASTTrue;
     else if (o.size() == 1)
       output = o[0];
     else if (o != c)
       output = nf->CreateNode(AND, o);
     else
       output = a;
   }

   return output;
 }
 }
	/********************************************************************
	*
	* BEGIN DATE: November, 2005
	*
	Permission is hereby granted, free of charge, to any person obtaining a copy
	of this software and associated documentation files (the "Software"), to deal
	in the Software without restriction, including without limitation the rights
	to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
	copies of the Software, and to permit persons to whom the Software is
	furnished to do so, subject to the following conditions:

	The above copyright notice and this permission notice shall be included in
	all copies or substantial portions of the Software.

	THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
	IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
	FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
	AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
	LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
	OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
	THE SOFTWARE.
	********************************************************************/

	#include "stp/Simplifier/PropagateEqualities.h"
	#include "stp/AbsRefineCounterExample/ArrayTransformer.h"
	#include "stp/Simplifier/Simplifier.h"
	#include <string>

	namespace stp
	{

	/* The search functions look for variables that can be expressed in terms of
	* variables.
	* The most obvious case it doesn't check for is NOT (OR (.. .. )).
	* I suspect this could take exponential time in the worst case, but on the
	* benchmarks I've tested,
	* it finishes in reasonable time.
	* The obvious way to speed it up (if required), is to create the RHS lazily.
	*/

	// The old XOR code used to use updateSolverMap instead of
	// UpdateSubstitutionMap, I've no idea why.

	bool PropagateEqualities::searchXOR(const ASTNode& lhs, const ASTNode& rhs)
	{
	Kind k = lhs.GetKind();

	if (lhs == rhs)
	return true;

	if (k == SYMBOL)
	return simp->UpdateSubstitutionMap(
	lhs, rhs); // checks whether it's been solved for or loops.

	if (k == NOT)
	return searchXOR(lhs[0], nf->CreateNode(NOT, rhs));

	bool result = false;
	if (k == XOR)
	for (size_t i = 0; i < lhs.Degree(); i++)
	{
	ASTVec others;
	for (size_t j = 0; j < lhs.Degree(); j++)
	if (j != i)
	others.push_back(lhs[j]);

	others.push_back(rhs);
	assert(others.size() > 1);
	ASTNode new_rhs = nf->CreateNode(XOR, others);

	result = searchXOR(lhs[i], new_rhs);
	if (result)
	return result;
	}

	if (k == EQ && lhs[0].GetValueWidth() == 1)
	{
	bool result = searchTerm(
	lhs[0],
	nf->CreateTerm(ITE, 1, rhs, lhs[1], nf->CreateTerm(BVNOT, 1, lhs[1])));

	if (!result)
	result = searchTerm(lhs[1],
	nf->CreateTerm(ITE, 1, rhs, lhs[0],
	nf->CreateTerm(BVNOT, 1, lhs[0])));
	}

	return result;
	}

	bool PropagateEqualities::searchTerm(const ASTNode& lhs, const ASTNode& rhs)
	{
	const unsigned width = lhs.GetValueWidth();

	if (lhs == rhs)
	return true;

	if (lhs.GetKind() == SYMBOL)
	return simp->UpdateSubstitutionMap(lhs, rhs); // checks whether it's been
	// solved for, or if the RHS
	// contains the LHS.

	if (lhs.GetKind() == BVUMINUS)
	return searchTerm(lhs[0], nf->CreateTerm(BVUMINUS, width, rhs));

	if (lhs.GetKind() == BVNOT)
	return searchTerm(lhs[0], nf->CreateTerm(BVNOT, width, rhs));

	if (lhs.GetKind() == BVXOR \|\| lhs.GetKind() == BVPLUS)
	for (size_t i = 0; i < lhs.Degree(); i++)
	{
	ASTVec others;
	for (size_t j = 0; j < lhs.Degree(); j++)
	if (j != i)
	others.push_back(lhs[j]);

	ASTNode new_rhs;
	if (lhs.GetKind() == BVXOR)
	{
	others.push_back(rhs);
	assert(others.size() > 1);
	new_rhs = nf->CreateTerm(lhs.GetKind(), width, others);
	}
	else if (lhs.GetKind() == BVPLUS)
	{
	if (others.size() > 1)
	new_rhs = nf->CreateTerm(BVPLUS, width, others);
	else
	new_rhs = others[0];

	new_rhs = nf->CreateTerm(BVUMINUS, width, new_rhs);
	new_rhs = nf->CreateTerm(BVPLUS, width, new_rhs, rhs);
	}
	else
	FatalError("sdafasfsdf2q3234423");

	bool result = searchTerm(lhs[i], new_rhs);
	if (result)
	return true;
	}

	if (lhs.Degree() == 2 && lhs.GetKind() == BVMULT && lhs[0].isConstant() &&
	simp->BVConstIsOdd(lhs[0]))
	return searchTerm(lhs[1],
	nf->CreateTerm(BVMULT, width,
	simp->MultiplicativeInverse(lhs[0]), rhs));

	return false;
	}

	// This doesn't rewrite changes through properly so needs to have a substitution
	// applied to its output.
	ASTNode PropagateEqualities::propagate(const ASTNode& a, ArrayTransformer* at)
	{
	ASTNode output;
	// if the variable has been solved for, then simply return it
	if (simp->InsideSubstitutionMap(a, output))
	return output;

	if (!alreadyVisited.insert(a.GetNodeNum()).second)
	{
	return a;
	}

	output = a;

	// traverse a and populate the SubstitutionMap
	const Kind k = a.GetKind();
	if (SYMBOL == k && BOOLEAN_TYPE == a.GetType())
	{
	bool updated = simp->UpdateSubstitutionMap(a, ASTTrue);
	output = updated ? ASTTrue : a;
	}
	else if (NOT == k)
	{
	bool updated = searchXOR(a[0], ASTFalse);
	output = updated ? ASTTrue : a;
	}
	else if (IFF == k \|\| EQ == k)
	{
	const ASTVec& c = a.GetChildren();

	if (c[0] == c[1])
	return ASTTrue;

	bool updated = simp->UpdateSubstitutionMap(c[0], c[1]);

	if (updated)
	{
	// fill the arrayname readindices vector if e0 is a
	// READ(Arr,index) and index is a BVCONST
	int to;
	if ((to = TermOrder(c[0], c[1])) == 1 && c[0].GetKind() == READ)
	at->FillUp_ArrReadIndex_Vec(c[0], c[1]);
	else if (to == -1 && c[1].GetKind() == READ)
	at->FillUp_ArrReadIndex_Vec(c[1], c[0]);
	}

	if (!updated)
	updated = searchTerm(c[0], c[1]);

	if (!updated)
	updated = searchTerm(c[1], c[0]);

	output = updated ? ASTTrue : a;
	}
	else if (XOR == k)
	{
	bool updated = searchXOR(a, ASTTrue);
	output = updated ? ASTTrue : a;

	if (updated)
	return output;

	// The below block should be subsumed by the searchXOR function which
	// generalises it.
	// So the below block should never do anything..
	#ifndef NDEBUG
	if (a.Degree() != 2)
	return output;

	int to = TermOrder(a[0], a[1]);
	if (0 == to)
	{
	if (a[0].GetKind() == NOT && a[0][0].GetKind() == EQ &&
	a[0][0][0].GetValueWidth() == 1 && a[0][0][1].GetKind() == SYMBOL)
	{
	// (XOR (NOT(= (1 v))) ... )
	const ASTNode& symbol = a[0][0][1];
	const ASTNode newN = nf->CreateTerm(
	ITE, 1, a[1], a[0][0][0], nf->CreateTerm(BVNOT, 1, a[0][0][0]));

	if (simp->UpdateSolverMap(symbol, newN))
	{
	assert(false);
	output = ASTTrue;
	}
	}
	else if (a[1].GetKind() == NOT && a[1][0].GetKind() == EQ &&
	a[1][0][0].GetValueWidth() == 1 &&
	a[1][0][1].GetKind() == SYMBOL)
	{
	const ASTNode& symbol = a[1][0][1];
	const ASTNode newN = nf->CreateTerm(
	ITE, 1, a[0], a[1][0][0], nf->CreateTerm(BVNOT, 1, a[1][0][0]));

	if (simp->UpdateSolverMap(symbol, newN))
	{
	assert(false);
	output = ASTTrue;
	}
	}
	else if (a[0].GetKind() == EQ && a[0][0].GetValueWidth() == 1 &&
	a[0][1].GetKind() == SYMBOL)
	{
	// XOR ((= 1 v) ... )

	const ASTNode& symbol = a[0][1];
	const ASTNode newN = nf->CreateTerm(
	ITE, 1, a[1], nf->CreateTerm(BVNOT, 1, a[0][0]), a[0][0]);

	if (simp->UpdateSolverMap(symbol, newN))
	{
	assert(false);
	output = ASTTrue;
	}
	}
	else if (a[1].GetKind() == EQ && a[1][0].GetValueWidth() == 1 &&
	a[1][1].GetKind() == SYMBOL)
	{
	const ASTNode& symbol = a[1][1];
	const ASTNode newN = nf->CreateTerm(
	ITE, 1, a[0], nf->CreateTerm(BVNOT, 1, a[1][0]), a[1][0]);

	if (simp->UpdateSolverMap(symbol, newN))
	{
	assert(false);
	output = ASTTrue;
	}
	}
	else
	return output;
	}
	else
	{
	ASTNode symbol, rhs;
	if (to == 1)
	{
	symbol = a[0];
	rhs = a[1];
	}
	else
	{
	symbol = a[1];
	rhs = a[0];
	}

	assert(symbol.GetKind() == SYMBOL);

	if (simp->UpdateSolverMap(symbol, nf->CreateNode(NOT, rhs)))
	{
	assert(false);
	output = ASTTrue;
	}
	}
	#endif
	}
	else if (AND == k)
	{
	const ASTVec& c = a.GetChildren();
	ASTVec o;
	o.reserve(c.size());

	for (ASTVec::const_iterator it = c.begin(), itend = c.end(); it != itend;
	it++)
	{
	if (always_true)
	simp->UpdateAlwaysTrueFormSet(*it);
	ASTNode aaa = propagate(*it, at);

	if (ASTTrue != aaa)
	{
	if (ASTFalse == aaa)
	return ASTFalse;
	else
	o.push_back(aaa);
	}
	}
	if (o.size() == 0)
	output = ASTTrue;
	else if (o.size() == 1)
	output = o[0];
	else if (o != c)
	output = nf->CreateNode(AND, o);
	else
	output = a;
	}

	return output;
	}
	}