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using Graphing;
using Microsoft.Boogie;
using System;
using System.Collections.Generic;
using System.Diagnostics.Contracts;
using System.Linq;
namespace GPUVerify {
class BlockPredicator {
Program prog;
Implementation impl;
Graph<Block> blockGraph;
Expr returnBlockId;
LocalVariable curVar, pVar;
IdentifierExpr cur, p;
Expr pExpr;
Dictionary<Microsoft.Boogie.Type, IdentifierExpr> havocVars =
new Dictionary<Microsoft.Boogie.Type, IdentifierExpr>();
Dictionary<Block, Expr> blockIds = new Dictionary<Block, Expr>();
HashSet<Block> doneBlocks = new HashSet<Block>();
BlockPredicator(Program p, Implementation i) {
prog = p;
impl = i;
}
void PredicateCmd(CmdSeq cmdSeq, Cmd cmd) {
if (cmd is AssignCmd) {
var aCmd = (AssignCmd)cmd;
cmdSeq.Add(new AssignCmd(Token.NoToken, aCmd.Lhss,
new List<Expr>(aCmd.Lhss.Zip(aCmd.Rhss, (lhs, rhs) =>
new NAryExpr(Token.NoToken,
new IfThenElse(Token.NoToken),
new ExprSeq(p, rhs, lhs.AsExpr))))));
} else if (cmd is AssertCmd) {
var aCmd = (AssertCmd)cmd;
if (cmdSeq.Last() is AssignCmd &&
cmdSeq.Cast<Cmd>().SkipEnd(1).All(c => c is AssertCmd)) {
// This may be a loop invariant. Make sure it continues to appear as
// the first statement in the block.
var assign = cmdSeq.Last();
cmdSeq.Truncate(cmdSeq.Length-1);
cmdSeq.Add(new AssertCmd(Token.NoToken, Expr.Imp(pExpr, aCmd.Expr)));
cmdSeq.Add(assign);
} else {
cmdSeq.Add(new AssertCmd(Token.NoToken, Expr.Imp(p, aCmd.Expr)));
}
} else if (cmd is AssumeCmd) {
var aCmd = (AssumeCmd)cmd;
cmdSeq.Add(new AssumeCmd(Token.NoToken, Expr.Imp(p, aCmd.Expr)));
} else if (cmd is HavocCmd) {
var hCmd = (HavocCmd)cmd;
foreach (IdentifierExpr v in hCmd.Vars) {
Microsoft.Boogie.Type type = v.Decl.TypedIdent.Type;
Contract.Assert(type != null);
IdentifierExpr havocTempExpr;
if (havocVars.ContainsKey(type)) {
havocTempExpr = havocVars[type];
} else {
var havocVar = new LocalVariable(Token.NoToken,
new TypedIdent(Token.NoToken,
"_HAVOC_" + type.ToString(), type));
impl.LocVars.Add(havocVar);
havocVars[type] = havocTempExpr =
new IdentifierExpr(Token.NoToken, havocVar);
}
cmdSeq.Add(new HavocCmd(Token.NoToken,
new IdentifierExprSeq(havocTempExpr)));
cmdSeq.Add(Cmd.SimpleAssign(Token.NoToken, v,
new NAryExpr(Token.NoToken,
new IfThenElse(Token.NoToken),
new ExprSeq(p, havocTempExpr, v))));
}
} else if (cmd is CallCmd) {
var cCmd = (CallCmd)cmd;
cCmd.Ins.Insert(0, p);
cmdSeq.Add(cCmd);
} else {
Console.WriteLine("Unsupported cmd: " + cmd.GetType().ToString());
}
}
void PredicateTransferCmd(CmdSeq cmdSeq, TransferCmd cmd) {
if (cmd is GotoCmd) {
var gCmd = (GotoCmd)cmd;
var targets = new List<Expr>(
gCmd.labelTargets.Cast<Block>().Select(b => blockIds[b]));
if (targets.Count == 1) {
PredicateCmd(cmdSeq, Cmd.SimpleAssign(Token.NoToken, cur, targets[0]));
} else {
PredicateCmd(cmdSeq, new HavocCmd(Token.NoToken,
new IdentifierExprSeq(cur)));
PredicateCmd(cmdSeq, new AssumeCmd(Token.NoToken,
targets.Select(t => (Expr)Expr.Eq(cur, t)).Aggregate(Expr.Or)));
}
foreach (Block b in gCmd.labelTargets) {
if (blockGraph.Predecessors(b).Count() == 1) {
if (!doneBlocks.Contains(b)) {
var assumes = b.Cmds.Cast<Cmd>().TakeWhile(c => c is AssumeCmd);
if (assumes.Count() > 0) {
foreach (AssumeCmd aCmd in assumes) {
cmdSeq.Add(new AssumeCmd(Token.NoToken,
Expr.Imp(Expr.Eq(cur, blockIds[b]),
aCmd.Expr)));
}
b.Cmds =
new CmdSeq(b.Cmds.Cast<Cmd>().Skip(assumes.Count()).ToArray());
}
}
}
}
} else if (cmd is ReturnCmd) {
PredicateCmd(cmdSeq, Cmd.SimpleAssign(Token.NoToken, cur, returnBlockId));
} else {
Console.WriteLine("Unsupported cmd: " + cmd.GetType().ToString());
}
}
void PredicateImplementation() {
blockGraph = prog.ProcessLoops(impl);
var sortedBlocks = blockGraph.LoopyTopSort();
int blockId = 0;
foreach (var block in impl.Blocks)
blockIds[block] = Expr.Literal(blockId++);
returnBlockId = Expr.Literal(blockId++);
curVar = new LocalVariable(Token.NoToken,
new TypedIdent(Token.NoToken, "cur",
Microsoft.Boogie.Type.Int));
impl.LocVars.Add(curVar);
cur = Expr.Ident(curVar);
pVar = new LocalVariable(Token.NoToken,
new TypedIdent(Token.NoToken, "p",
Microsoft.Boogie.Type.Bool));
impl.LocVars.Add(pVar);
p = Expr.Ident(pVar);
var newBlocks = new List<Block>();
var fp = Expr.Ident(impl.InParams[0]);
Block entryBlock = new Block();
entryBlock.Label = "entry";
entryBlock.Cmds = new CmdSeq(Cmd.SimpleAssign(Token.NoToken, cur,
new NAryExpr(Token.NoToken,
new IfThenElse(Token.NoToken),
new ExprSeq(fp, blockIds[sortedBlocks[0].Item1],
returnBlockId))));
newBlocks.Add(entryBlock);
var prevBlock = entryBlock;
foreach (var n in sortedBlocks) {
if (n.Item2) {
var tailBlock = new Block();
newBlocks.Add(tailBlock);
tailBlock.Label = n.Item1.Label + ".tail";
tailBlock.Cmds = new CmdSeq(new AssumeCmd(Token.NoToken,
Expr.Neq(cur, blockIds[n.Item1])));
prevBlock.TransferCmd = new GotoCmd(Token.NoToken,
new BlockSeq(tailBlock, n.Item1));
prevBlock = tailBlock;
} else {
var runBlock = n.Item1;
newBlocks.Add(runBlock);
pExpr = Expr.Eq(cur, blockIds[runBlock]);
CmdSeq newCmdSeq = new CmdSeq();
newCmdSeq.Add(Cmd.SimpleAssign(Token.NoToken, p, pExpr));
foreach (Cmd cmd in runBlock.Cmds)
PredicateCmd(newCmdSeq, cmd);
PredicateTransferCmd(newCmdSeq, runBlock.TransferCmd);
runBlock.Cmds = newCmdSeq;
prevBlock.TransferCmd = new GotoCmd(Token.NoToken,
new BlockSeq(runBlock));
prevBlock = runBlock;
doneBlocks.Add(runBlock);
}
}
prevBlock.TransferCmd = new ReturnCmd(Token.NoToken);
impl.Blocks = newBlocks;
}
public static void Predicate(Program p) {
foreach (var decl in p.TopLevelDeclarations) {
if (decl is DeclWithFormals && !(decl is Function)) {
var dwf = (DeclWithFormals)decl;
var fpVar = new LocalVariable(Token.NoToken,
new TypedIdent(Token.NoToken, "fp",
Microsoft.Boogie.Type.Bool));
dwf.InParams = new VariableSeq((dwf.InParams + new VariableSeq(fpVar))
.Cast<Variable>().ToArray());
}
var impl = decl as Implementation;
if (impl != null)
new BlockPredicator(p, impl).PredicateImplementation();
}
}
}
}
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