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using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Diagnostics;
using Microsoft.Boogie;
using Microsoft.Basetypes;
namespace GPUVerify
{
class MayBePowerOfTwoAnalyser
{
private GPUVerifier verifier;
private Dictionary<string, Dictionary<string, bool>> mayBePowerOfTwoInfo;
public MayBePowerOfTwoAnalyser(GPUVerifier verifier)
{
this.verifier = verifier;
mayBePowerOfTwoInfo = new Dictionary<string, Dictionary<string, bool>>();
}
internal void Analyse()
{
foreach (Declaration D in verifier.Program.TopLevelDeclarations)
{
if (D is Implementation)
{
Implementation Impl = D as Implementation;
mayBePowerOfTwoInfo.Add(Impl.Name, new Dictionary<string, bool>());
SetNotPowerOfTwo(Impl.Name, GPUVerifier._X.Name);
SetNotPowerOfTwo(Impl.Name, GPUVerifier._Y.Name);
SetNotPowerOfTwo(Impl.Name, GPUVerifier._Z.Name);
foreach (Variable v in Impl.LocVars)
{
SetNotPowerOfTwo(Impl.Name, v.Name);
}
foreach (Variable v in Impl.InParams)
{
SetNotPowerOfTwo(Impl.Name, v.Name);
}
foreach (Variable v in Impl.OutParams)
{
SetNotPowerOfTwo(Impl.Name, v.Name);
}
// Fixpoint not required - this is just syntactic
Analyse(Impl);
}
}
if (CommandLineOptions.ShowMayBePowerOfTwoAnalysis)
{
dump();
}
}
private void SetNotPowerOfTwo(string p, string v)
{
mayBePowerOfTwoInfo[p][v] = false;
}
private void Analyse(Implementation Impl)
{
Analyse(Impl, verifier.RootRegion(Impl));
}
private void Analyse(Implementation impl, IRegion region)
{
foreach (Cmd c in region.Cmds())
{
if (c is AssignCmd)
{
AssignCmd assign = c as AssignCmd;
for (int i = 0; i != assign.Lhss.Count; i++)
{
if (assign.Lhss[i] is SimpleAssignLhs)
{
Variable v = (assign.Lhss[i] as SimpleAssignLhs).AssignedVariable.Decl;
if (mayBePowerOfTwoInfo[impl.Name].ContainsKey(v.Name))
{
if (isPowerOfTwoOperation(v, assign.Rhss[i]))
{
mayBePowerOfTwoInfo[impl.Name][v.Name] = true;
}
}
}
}
}
}
}
private bool isPowerOfTwoOperation(Variable v, Expr expr)
{
if (!(
v.TypedIdent.Type.Equals(
Microsoft.Boogie.Type.GetBvType(8))
||
v.TypedIdent.Type.Equals(
Microsoft.Boogie.Type.GetBvType(16))
||
v.TypedIdent.Type.Equals(
Microsoft.Boogie.Type.GetBvType(32))
))
{
return false;
}
Microsoft.Boogie.Type bvType = v.TypedIdent.Type as BvType;
if (!(expr is NAryExpr))
{
return false;
}
NAryExpr nary = expr as NAryExpr;
string bvPrefix = "BV" + bvType.BvBits + "_";
if (nary.Fun.FunctionName.Equals(bvPrefix + "MUL"))
{
Debug.Assert(nary.Args.Length == 2);
return
(
(IsVariable(nary.Args[0], v) || IsVariable(nary.Args[1], v)) &&
(IsConstant(nary.Args[0], 2) || IsConstant(nary.Args[1], 2))
);
}
if (nary.Fun.FunctionName.Equals(bvPrefix + "DIV"))
{
Debug.Assert(nary.Args.Length == 2);
return
(
IsVariable(nary.Args[0], v) && IsConstant(nary.Args[1], 2)
);
}
if (nary.Fun.FunctionName.Equals(bvPrefix + "SHL"))
{
return
(
IsVariable(nary.Args[0], v) && IsConstant(nary.Args[1], 1)
);
}
if (nary.Fun.FunctionName.Equals(bvPrefix + "ASHR"))
{
return
(
IsVariable(nary.Args[0], v) && IsConstant(nary.Args[1], 1)
);
}
return false;
}
private bool IsConstant(Expr expr, int x)
{
if (!(expr is LiteralExpr))
{
return false;
}
LiteralExpr lit = expr as LiteralExpr;
if (!(lit.Val is BvConst))
{
return false;
}
return (lit.Val as BvConst).Value.ToInt == x;
}
private bool IsVariable(Expr expr, Variable v)
{
return expr is IdentifierExpr && ((expr as IdentifierExpr).Decl.Name.Equals(v.Name));
}
private void dump()
{
foreach (string p in mayBePowerOfTwoInfo.Keys)
{
Console.WriteLine("Procedure " + p);
foreach (string v in mayBePowerOfTwoInfo[p].Keys)
{
Console.WriteLine(" " + v + ": " +
(mayBePowerOfTwoInfo[p][v] ? "may be power of two" : "likely not power of two"));
}
}
}
internal bool MayBePowerOfTwo(string p, string v)
{
if (!mayBePowerOfTwoInfo.ContainsKey(p))
{
return false;
}
if (!mayBePowerOfTwoInfo[p].ContainsKey(v))
{
return false;
}
return mayBePowerOfTwoInfo[p][v];
}
}
}
|
