path: root/Analysis/ValueState.cpp

//= ValueState.cpp - Path-Sens. "State" for tracking valuues -----*- C++ -*--=//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
//  This files defines SymbolID, ExprBindKey, and ValueState.
//
//===----------------------------------------------------------------------===//

#include "ValueState.h"

using namespace clang;

bool ValueState::isNotEqual(SymbolID sym, const llvm::APSInt& V) const {
  // First, retrieve the NE-set associated with the given symbol.
  ConstantNotEqTy::TreeTy* T = Data->ConstantNotEq.SlimFind(sym);
  
  if (!T)
    return false;
  
  // Second, see if V is present in the NE-set.
  return T->getValue().second.contains(&V);
}

const llvm::APSInt* ValueState::getSymVal(SymbolID sym) const {
  ConstantEqTy::TreeTy* T = Data->ConstantEq.SlimFind(sym);
  return T ? T->getValue().second : NULL;  
}

ValueState
ValueStateManager::RemoveDeadBindings(ValueState St, Stmt* Loc,
                                      const LiveVariables& Liveness) {  
  
  // This code essentially performs a "mark-and-sweep" of the VariableBindings.
  // The roots are any Block-level exprs and Decls that our liveness algorithm
  // tells us are live.  We then see what Decls they may reference, and keep
  // those around.  This code more than likely can be made faster, and the
  // frequency of which this method is called should be experimented with
  // for optimum performance.
  
  llvm::SmallVector<ValueDecl*, 10> WList;
  
  ValueStateImpl NewSt = *St;
  
  // Drop bindings for subexpressions.
  NewSt.SubExprBindings = EXFactory.GetEmptyMap();
  
  // Iterate over the block-expr bindings.
  for (ValueState::beb_iterator I=St.beb_begin(), E=St.beb_end(); I!=E ; ++I) {
    
    Expr* BlkExpr = I.getKey();
    
    if (Liveness.isLive(Loc, BlkExpr)) {
      if (isa<lval::DeclVal>(I.getData())) {
        lval::DeclVal LV = cast<lval::DeclVal>(I.getData());
        WList.push_back(LV.getDecl());
      }
    }
    else
      NewSt.BlockExprBindings = Remove(NewSt, BlkExpr);
    
    continue;
  }

  // Iterate over the variable bindings.
  for (ValueState::vb_iterator I = St.vb_begin(), E = St.vb_end(); I!=E ; ++I)
    if (Liveness.isLive(Loc, I.getKey()))
      WList.push_back(I.getKey());
  
  llvm::SmallPtrSet<ValueDecl*, 10> Marked;  
  
  while (!WList.empty()) {
    ValueDecl* V = WList.back();
    WList.pop_back();
    
    if (Marked.count(V))
      continue;
    
    Marked.insert(V);
    
    if (V->getType()->isPointerType()) {
      const LValue& LV = cast<LValue>(GetValue(St, lval::DeclVal(V)));
      
      if (!isa<lval::DeclVal>(LV))
        continue;
      
      const lval::DeclVal& LVD = cast<lval::DeclVal>(LV);
      WList.push_back(LVD.getDecl());
    }    
  }
  
  for (ValueState::vb_iterator I = St.vb_begin(), E = St.vb_end(); I!=E ; ++I)
    if (!Marked.count(I.getKey()))
      NewSt.VarBindings = Remove(NewSt, I.getKey());
  
  return getPersistentState(NewSt);
}


RValue ValueStateManager::GetValue(ValueState St, const LValue& LV,
                                   QualType* T) {
  if (isa<UnknownVal>(LV))
    return UnknownVal();
  
  switch (LV.getSubKind()) {
    case lval::DeclValKind: {
      ValueState::VarBindingsTy::TreeTy* T =
      // FIXME: We should make lval::DeclVal only contain VarDecl
        St->VarBindings.SlimFind(
              cast<VarDecl>(cast<lval::DeclVal>(LV).getDecl()));
      
      return T ? T->getValue().second : UnknownVal();
    }
     
      // FIXME: We should bind how far a "ContentsOf" will go...
      
    case lval::SymbolValKind: {
      const lval::SymbolVal& SV = cast<lval::SymbolVal>(LV);
      assert (T);
      
      if (T->getTypePtr()->isPointerType())
        return lval::SymbolVal(SymMgr.getContentsOfSymbol(SV.getSymbol()));
      else
        return nonlval::SymbolVal(SymMgr.getContentsOfSymbol(SV.getSymbol()));
    }
      
    default:
      assert (false && "Invalid LValue.");
      break;
  }
  
  return UnknownVal();
}

ValueState
ValueStateManager::AddNE(ValueState St, SymbolID sym, const llvm::APSInt& V) {
  // First, retrieve the NE-set associated with the given symbol.
  ValueState::ConstantNotEqTy::TreeTy* T = St->ConstantNotEq.SlimFind(sym);    
  
  ValueState::IntSetTy S = T ? T->getValue().second : ISetFactory.GetEmptySet();
  
  // Now add V to the NE set.  
  S = ISetFactory.Add(S, &V);
  
  // Create a new state with the old binding replaced.
  ValueStateImpl NewSt = *St;
  NewSt.ConstantNotEq = CNEFactory.Add(NewSt.ConstantNotEq,
                                              sym, S);
    
  // Get the persistent copy.
  return getPersistentState(NewSt);
}

ValueState
ValueStateManager::AddEQ(ValueState St, SymbolID sym, const llvm::APSInt& V) {
  // Create a new state with the old binding replaced.
  ValueStateImpl NewSt = *St;
  NewSt.ConstantEq = CEFactory.Add(NewSt.ConstantEq, sym, &V);
  
  // Get the persistent copy.
  return getPersistentState(NewSt);
}

RValue ValueStateManager::GetValue(ValueState St, Expr* E, bool* hasVal) {
  for (;;) {
    switch (E->getStmtClass()) {

      case Stmt::AddrLabelExprClass:
        return LValue::GetValue(cast<AddrLabelExpr>(E));
        
        // ParenExprs are no-ops.
        
      case Stmt::ParenExprClass:
        E = cast<ParenExpr>(E)->getSubExpr();
        continue;
        
        // DeclRefExprs can either evaluate to an LValue or a Non-LValue
        // (assuming an implicit "load") depending on the context.  In this
        // context we assume that we are retrieving the value contained
        // within the referenced variables.
        
      case Stmt::DeclRefExprClass:
        return GetValue(St, lval::DeclVal(cast<DeclRefExpr>(E)->getDecl()));
        
        // Integer literals evaluate to an RValue.  Simply retrieve the
        // RValue for the literal.
        
      case Stmt::IntegerLiteralClass:
        return NonLValue::GetValue(ValMgr, cast<IntegerLiteral>(E));
        
      case Stmt::CharacterLiteralClass: {
        CharacterLiteral* C = cast<CharacterLiteral>(E);
        
        return NonLValue::GetValue(ValMgr, C->getValue(), C->getType(),
                                   C->getLoc());
      }

        // Casts where the source and target type are the same
        // are no-ops.  We blast through these to get the descendant
        // subexpression that has a value.
        
        
      case Stmt::ImplicitCastExprClass: {
        ImplicitCastExpr* C = cast<ImplicitCastExpr>(E);
        if (C->getType() == C->getSubExpr()->getType()) {
          E = C->getSubExpr();
          continue;
        }
        break;
      }
        
      case Stmt::CastExprClass: {
        CastExpr* C = cast<CastExpr>(E);
        if (C->getType() == C->getSubExpr()->getType()) {
          E = C->getSubExpr();
          continue;
        }
        break;
      }
        
        // Handle all other Stmt* using a lookup.
        
      default:
        break;
    };
    
    break;
  }
  
  ValueState::ExprBindingsTy::TreeTy* T = St->SubExprBindings.SlimFind(E);
  
  if (T) {
    if (hasVal) *hasVal = true;
    return T->getValue