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//-----------------------------------------------------------------------------
//
// Copyright (C) Microsoft Corporation. All Rights Reserved.
//
//-----------------------------------------------------------------------------
using System;
using System.Collections;
using Microsoft.Boogie;
using Microsoft.Boogie.VCExprAST;
using System.Diagnostics.Contracts;
using System.Collections.Generic;
using Microsoft.Basetypes;
namespace VC {
public class VCContext
{
[ContractInvariantMethod]
void ObjectInvariant()
{
Contract.Invariant(Ctxt != null);
}
[Rep] public readonly Dictionary<int, Absy> Label2absy;
[Rep] public readonly ProverContext Ctxt;
public readonly VCExpr ControlFlowVariableExpr;
public int AssertionCount; // counts the number of assertions for which Wlp has been computed
public bool isPositiveContext;
public VCContext(Dictionary<int, Absy> label2absy, ProverContext ctxt, bool isPositiveContext = true)
{
Contract.Requires(ctxt != null);
this.Label2absy = label2absy;
this.Ctxt = ctxt;
this.isPositiveContext = isPositiveContext;
}
public VCContext(Dictionary<int, Absy> label2absy, ProverContext ctxt, VCExpr controlFlowVariableExpr, bool isPositiveContext = true)
{
Contract.Requires(ctxt != null);
this.Label2absy = label2absy;
this.Ctxt = ctxt;
this.ControlFlowVariableExpr = controlFlowVariableExpr;
this.isPositiveContext = isPositiveContext;
}
}
#region A class to compute wlp of a passive command program
public class Wlp
{
public static VCExpr Block(Block b, VCExpr N, VCContext ctxt)
//modifies ctxt.*;
{
Contract.Requires(b != null);
Contract.Requires(N != null);
Contract.Requires(ctxt != null);
Contract.Ensures(Contract.Result<VCExpr>() != null);
VCExpressionGenerator gen = ctxt.Ctxt.ExprGen;
Contract.Assert(gen != null);
VCExpr res = N;
for (int i = b.Cmds.Count; --i >= 0; )
{
res = Cmd(b, cce.NonNull( b.Cmds[i]), res, ctxt);
}
int id = b.UniqueId;
if (ctxt.Label2absy != null) {
ctxt.Label2absy[id] = b;
}
try {
cce.BeginExpose(ctxt);
if (ctxt.Label2absy == null) {
return res;
}
else {
return gen.Implies(gen.LabelPos(cce.NonNull(id.ToString()), VCExpressionGenerator.True), res);
}
} finally {
cce.EndExpose();
}
}
/// <summary>
/// Computes the wlp for an assert or assume command "cmd".
/// </summary>
public static VCExpr Cmd(Block b, Cmd cmd, VCExpr N, VCContext ctxt) {
Contract.Requires(cmd != null);
Contract.Requires(N != null);
Contract.Requires(ctxt != null);
Contract.Ensures(Contract.Result<VCExpr>() != null);
VCExpressionGenerator gen = ctxt.Ctxt.ExprGen;
Contract.Assert(gen != null);
if (cmd is AssertCmd) {
AssertCmd ac = (AssertCmd)cmd;
var isFullyVerified = false;
if (ac.VerifiedUnder != null)
{
var litExpr = ac.VerifiedUnder as LiteralExpr;
isFullyVerified = litExpr != null && litExpr.IsTrue;
}
if (!isFullyVerified)
{
ctxt.Ctxt.BoogieExprTranslator.isPositiveContext = !ctxt.Ctxt.BoogieExprTranslator.isPositiveContext;
}
VCExpr C = ctxt.Ctxt.BoogieExprTranslator.Translate(ac.Expr);
VCExpr VU = null;
if (!isFullyVerified)
{
if (ac.VerifiedUnder != null)
{
VU = ctxt.Ctxt.BoogieExprTranslator.Translate(ac.VerifiedUnder);
}
ctxt.Ctxt.BoogieExprTranslator.isPositiveContext = !ctxt.Ctxt.BoogieExprTranslator.isPositiveContext;
}
VCExpr R = null;
if (CommandLineOptions.Clo.vcVariety == CommandLineOptions.VCVariety.Doomed) {
R = gen.Implies(C, N);
} else {
var subsumption = Subsumption(ac);
if (subsumption == CommandLineOptions.SubsumptionOption.Always
|| (subsumption == CommandLineOptions.SubsumptionOption.NotForQuantifiers && !(C is VCExprQuantifier)))
{
N = gen.ImpliesSimp(C, N, false);
}
if (isFullyVerified)
{
return N;
}
else if (VU != null)
{
C = gen.OrSimp(VU, C);
}
int id = ac.UniqueId;
if (ctxt.Label2absy != null)
{
ctxt.Label2absy[id] = ac;
}
ctxt.AssertionCount++;
if (ctxt.ControlFlowVariableExpr == null) {
Contract.Assert(ctxt.Label2absy != null);
R = gen.AndSimp(gen.LabelNeg(cce.NonNull(id.ToString()), C), N);
} else {
VCExpr controlFlowFunctionAppl = gen.ControlFlowFunctionApplication(ctxt.ControlFlowVariableExpr, gen.Integer(BigNum.FromInt(b.UniqueId)));
Contract.Assert(controlFlowFunctionAppl != null);
VCExpr assertFailure = gen.Eq(controlFlowFunctionAppl, gen.Integer(BigNum.FromInt(-ac.UniqueId)));
if (ctxt.Label2absy == null) {
R = gen.AndSimp(gen.Implies(assertFailure, C), N);
} else {
R = gen.AndSimp(gen.LabelNeg(cce.NonNull(id.ToString()), gen.Implies(assertFailure, C)), N);
}
}
}
return R;
} else if (cmd is AssumeCmd) {
AssumeCmd ac = (AssumeCmd)cmd;
if (CommandLineOptions.Clo.StratifiedInlining > 0) {
// Label the assume if it is a procedure call
NAryExpr naryExpr = ac.Expr as NAryExpr;
if (naryExpr != null) {
if (naryExpr.Fun is FunctionCall) {
int id = ac.UniqueId;
ctxt.Label2absy[id] = ac;
return gen.ImpliesSimp(gen.LabelPos(cce.NonNull("si_fcall_" + id.ToString()), ctxt.Ctxt.BoogieExprTranslator.Translate(ac.Expr)), N);
}
}
}
return gen.ImpliesSimp(ctxt.Ctxt.BoogieExprTranslator.Translate(ac.Expr), N);
} else {
Console.WriteLine(cmd.ToString());
Contract.Assert(false); throw new cce.UnreachableException(); // unexpected command
}
}
public static CommandLineOptions.SubsumptionOption Subsumption(AssertCmd ac) {
Contract.Requires(ac != null);
int n = QKeyValue.FindIntAttribute(ac.Attributes, "subsumption", -1);
switch (n) {
case 0: return CommandLineOptions.SubsumptionOption.Never;
case 1: return CommandLineOptions.SubsumptionOption.NotForQuantifiers;
case 2: return CommandLineOptions.SubsumptionOption.Always;
default: return CommandLineOptions.Clo.UseSubsumption;
}
}
public static VCExpr RegExpr(RE r, VCExpr N, VCContext ctxt)
{
Contract.Requires(r != null);
Contract.Requires(N != null);
Contract.Requires(ctxt != null);
Contract.Ensures(Contract.Result<VCExpr>() != null);
if ( r is AtomicRE )
{
AtomicRE ar = (AtomicRE) r;
return Block(ar.b, N, ctxt);
}
else if ( r is Sequential )
{
Sequential s = (Sequential) r;
return RegExpr(s.first, RegExpr(s.second, N, ctxt), ctxt);
}
else if ( r is Choice )
{
Choice ch = (Choice) r;
VCExpr res;
if (ch.rs == null || ch.rs.Count==0)
{
res = N;
}
else
{
VCExpr currentWLP = RegExpr(cce.NonNull(ch.rs[0]), N, ctxt);
for (int i = 1, n = ch.rs.Count; i < n; i++)
{
currentWLP = ctxt.Ctxt.ExprGen.And(currentWLP, RegExpr(cce.NonNull(ch.rs[i]), N, ctxt));
}
res = currentWLP;
}
return res;
}
else
{
Contract.Assert(false);throw new cce.UnreachableException(); // unexpected RE subtype
}
}
}
#endregion
}
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