private VCExpr create_let(Term t, VCExpr u)
{
var name = "$x" + let_ctr.ToString();
let_ctr++;
var sym = gen.Variable(name, u.Type);
memo.Remove(t);
memo.Add(t, sym);
lets.Add(gen.LetBinding(sym, u));
return(sym);
}
VCExpr LetVC(Block block,
Dictionary <int, Absy> label2absy,
Hashtable /*<Block, VCExprVar!>*/ blockVariables,
List <VCExprLetBinding> bindings,
ProverContext proverCtxt,
out int assertionCount)
{
Contract.Requires(label2absy != null);
Contract.Requires(blockVariables != null);
Contract.Requires(proverCtxt != null);
Contract.Requires(cce.NonNullElements(bindings));
Contract.Ensures(Contract.Result <VCExpr>() != null);
assertionCount = 0;
VCExpressionGenerator gen = proverCtxt.ExprGen;
Contract.Assert(gen != null);
VCExprVar v = (VCExprVar)blockVariables[block];
if (v == null)
{
/*
* For block A (= block), generate:
* LET_binding A_correct = wp(A_body, (/\ S \in Successors(A) :: S_correct))
* with the side effect of adding the let bindings to "bindings" for any
* successor not yet visited.
*/
VCExpr SuccCorrect;
GotoCmd gotocmd = block.TransferCmd as GotoCmd;
if (gotocmd == null)
{
if (CommandLineOptions.Clo.vcVariety == CommandLineOptions.VCVariety.Doomed)
{
SuccCorrect = VCExpressionGenerator.False;
}
else
{
SuccCorrect = VCExpressionGenerator.True;
}
}
else
{
Contract.Assert(gotocmd.labelTargets != null);
List <VCExpr> SuccCorrectVars = new List <VCExpr>(gotocmd.labelTargets.Count);
foreach (Block successor in gotocmd.labelTargets)
{
Contract.Assert(successor != null);
int ac;
VCExpr s = LetVC(successor, label2absy, blockVariables, bindings, proverCtxt, out ac);
assertionCount += ac;
SuccCorrectVars.Add(s);
}
SuccCorrect = gen.NAry(VCExpressionGenerator.AndOp, SuccCorrectVars);
}
VCContext context = new VCContext(label2absy, proverCtxt);
// m_Context = context;
VCExpr vc = Wlp.Block(block, SuccCorrect, context);
assertionCount += context.AssertionCount;
v = gen.Variable(block.Label + "_correct", Microsoft.Boogie.Type.Bool);
bindings.Add(gen.LetBinding(v, vc));
blockVariables.Add(block, v);
}
return(v);
}