public Graph<Block> ProcessLoops(Implementation impl) {
while (true) {
impl.PruneUnreachableBlocks();
impl.ComputePredecessorsForBlocks();
Graph<Block/*!*/>/*!*/ g = GraphFromImpl(impl);
g.ComputeLoops();
if (g.Reducible) {
return g;
}
throw new IrreducibleLoopException();
#if USED_CODE
System.Diagnostics.Debug.Assert(g.SplitCandidates.Count > 0);
Block splitCandidate = null;
foreach (Block b in g.SplitCandidates) {
if (b.Predecessors.Length > 1) {
splitCandidate = b;
break;
}
}
System.Diagnostics.Debug.Assert(splitCandidate != null);
int count = 0;
foreach (Block b in splitCandidate.Predecessors) {
GotoCmd gotoCmd = (GotoCmd)b.TransferCmd;
gotoCmd.labelNames.Remove(splitCandidate.Label);
gotoCmd.labelTargets.Remove(splitCandidate);
CodeCopier codeCopier = new CodeCopier(new Hashtable(), new Hashtable());
List<Cmd> newCmdSeq = codeCopier.CopyCmdSeq(splitCandidate.Cmds);
TransferCmd newTransferCmd;
GotoCmd splitGotoCmd = splitCandidate.TransferCmd as GotoCmd;
if (splitGotoCmd == null) {
newTransferCmd = new ReturnCmd(splitCandidate.tok);
}
else {
List<String> newLabelNames = new List<String>();
newLabelNames.AddRange(splitGotoCmd.labelNames);
List<Block> newLabelTargets = new List<Block>();
newLabelTargets.AddRange(splitGotoCmd.labelTargets);
newTransferCmd = new GotoCmd(splitCandidate.tok, newLabelNames, newLabelTargets);
}
Block copy = new Block(splitCandidate.tok, splitCandidate.Label + count++, newCmdSeq, newTransferCmd);
impl.Blocks.Add(copy);
gotoCmd.AddTarget(copy);
}
#endif
}
}
// result[0] is the entry block
protected List<Block/*!*/>/*!*/ CreateInlinedBlocks(CallCmd callCmd, Implementation impl, string nextBlockLabel) {
Contract.Requires(nextBlockLabel != null);
Contract.Requires(impl != null);
Contract.Requires(impl.Proc != null);
Contract.Requires(callCmd != null);
Contract.Requires(codeCopier.Subst != null);
Contract.Requires(codeCopier.OldSubst != null);
Contract.Ensures(cce.NonNullElements(Contract.Result<List<Block>>()));
List<Block/*!*/>/*!*/ implBlocks = cce.NonNull(impl.OriginalBlocks);
Contract.Assert(implBlocks.Count > 0);
Procedure proc = impl.Proc;
string startLabel = implBlocks[0].Label;
List<Block/*!*/>/*!*/ inlinedBlocks = new List<Block/*!*/>();
// create in block
List<Cmd> inCmds = new List<Cmd>();
// assign in parameters
for (int i = 0; i < impl.InParams.Count; ++i) {
Cmd cmd = Cmd.SimpleAssign(impl.tok,
(IdentifierExpr)cce.NonNull(codeCopier.Subst)(cce.NonNull(impl.InParams[i])),
cce.NonNull(callCmd.Ins[i]));
inCmds.Add(cmd);
}
// inject requires
for (int i = 0; i < proc.Requires.Count; i++) {
Requires/*!*/ req = cce.NonNull(proc.Requires[i]);
inCmds.Add(InlinedRequires(callCmd, req));
}
List<Variable> locVars = cce.NonNull(impl.OriginalLocVars);
// havoc locals and out parameters in case procedure is invoked in a loop
List<IdentifierExpr> havocVars = new List<IdentifierExpr>();
foreach (Variable v in locVars)
{
havocVars.Add((IdentifierExpr)codeCopier.Subst(v));
}
foreach (Variable v in impl.OutParams)
{
havocVars.Add((IdentifierExpr)codeCopier.Subst(v));
}
if (havocVars.Count > 0)
{
inCmds.Add(new HavocCmd(Token.NoToken, havocVars));
}
// add where clauses of local vars as assume
for (int i = 0; i < locVars.Count; ++i) {
Expr whereExpr = (cce.NonNull(locVars[i])).TypedIdent.WhereExpr;
if (whereExpr != null) {
whereExpr = Substituter.Apply(codeCopier.Subst, whereExpr);
// FIXME we cannot overwrite it, can we?!
(cce.NonNull(locVars[i])).TypedIdent.WhereExpr = whereExpr;
AssumeCmd/*!*/ a = new AssumeCmd(Token.NoToken, whereExpr);
Contract.Assert(a != null);
inCmds.Add(a);
}
}
// add where clauses of output params as assume
for (int i = 0; i < impl.OutParams.Count; ++i) {
Expr whereExpr = (cce.NonNull(impl.OutParams[i])).TypedIdent.WhereExpr;
if (whereExpr != null) {
whereExpr = Substituter.Apply(codeCopier.Subst, whereExpr);
// FIXME likewise
(cce.NonNull(impl.OutParams[i])).TypedIdent.WhereExpr = whereExpr;
AssumeCmd/*!*/ a = new AssumeCmd(Token.NoToken, whereExpr);
Contract.Assert(a != null);
inCmds.Add(a);
}
}
// assign modifies old values
foreach (IdentifierExpr/*!*/ mie in proc.Modifies) {
Contract.Assert(mie != null);
Variable/*!*/ mvar = cce.NonNull(mie.Decl);
AssignCmd assign = Cmd.SimpleAssign(impl.tok, (IdentifierExpr)cce.NonNull(codeCopier.OldSubst(mvar)), mie);
inCmds.Add(assign);
}
GotoCmd inGotoCmd = new GotoCmd(callCmd.tok, new List<String> { GetInlinedProcLabel(proc.Name) + "$" + startLabel });
Block inBlock = new Block(impl.tok, GetInlinedProcLabel(proc.Name) + "$Entry", inCmds, inGotoCmd);
inlinedBlocks.Add(inBlock);
// inject the blocks of the implementation
Block intBlock;
foreach (Block block in implBlocks) {
List<Cmd> copyCmds = codeCopier.CopyCmdSeq(block.Cmds);
if (0 <= inlineDepth) {
copyCmds = RemoveAsserts(copyCmds);
}
TransferCmd transferCmd = CreateInlinedTransferCmd(cce.NonNull(block.TransferCmd), GetInlinedProcLabel(proc.Name));
intBlock = new Block(block.tok, GetInlinedProcLabel(proc.Name) + "$" + block.Label, copyCmds, transferCmd);
inlinedBlocks.Add(intBlock);
}
// create out block
List<Cmd> outCmds = new List<Cmd>();
// inject ensures
for (int i = 0; i < proc.Ensures.Count; i++) {
Ensures/*!*/ ens = cce.NonNull(proc.Ensures[i]);
outCmds.Add(InlinedEnsures(callCmd, ens));
}
// assign out params
for (int i = 0; i < impl.OutParams.Count; ++i) {
Expr/*!*/ cout_exp = (IdentifierExpr)cce.NonNull(codeCopier.Subst(cce.NonNull(impl.OutParams[i])));
Cmd cmd = Cmd.SimpleAssign(impl.tok, cce.NonNull(callCmd.Outs[i]), cout_exp);
outCmds.Add(cmd);
}
// create out block
GotoCmd outGotoCmd = new GotoCmd(Token.NoToken, new List<String> { nextBlockLabel });
Block outBlock = new Block(impl.tok, GetInlinedProcLabel(proc.Name) + "$Return", outCmds, outGotoCmd);
inlinedBlocks.Add(outBlock);
return inlinedBlocks;
}
void CreateProceduresForLoops(Implementation impl, Graph<Block/*!*/>/*!*/ g,
List<Implementation/*!*/>/*!*/ loopImpls,
Dictionary<string, Dictionary<string, Block>> fullMap) {
Contract.Requires(impl != null);
Contract.Requires(cce.NonNullElements(loopImpls));
// Enumerate the headers
// for each header h:
// create implementation p_h with
// inputs = inputs, outputs, and locals of impl
// outputs = outputs and locals of impl
// locals = empty set
// add call o := p_h(i) at the beginning of the header block
// break the back edges whose target is h
// Enumerate the headers again to create the bodies of p_h
// for each header h:
// compute the loop corresponding to h
// make copies of all blocks in the loop for h
// delete all target edges that do not go to a block in the loop
// create a new entry block and a new return block
// add edges from entry block to the loop header and the return block
// add calls o := p_h(i) at the end of the blocks that are sources of back edges
foreach (Block block in impl.Blocks)
{
AddToFullMap(fullMap, impl.Name, block.Label, block);
}
bool detLoopExtract = CommandLineOptions.Clo.DeterministicExtractLoops;
Dictionary<Block/*!*/, List<Variable>/*!*/>/*!*/ loopHeaderToInputs = new Dictionary<Block/*!*/, List<Variable>/*!*/>();
Dictionary<Block/*!*/, List<Variable>/*!*/>/*!*/ loopHeaderToOutputs = new Dictionary<Block/*!*/, List<Variable>/*!*/>();
Dictionary<Block/*!*/, Dictionary<Variable, Expr>/*!*/>/*!*/ loopHeaderToSubstMap = new Dictionary<Block/*!*/, Dictionary<Variable, Expr>/*!*/>();
Dictionary<Block/*!*/, LoopProcedure/*!*/>/*!*/ loopHeaderToLoopProc = new Dictionary<Block/*!*/, LoopProcedure/*!*/>();
Dictionary<Block/*!*/, CallCmd/*!*/>/*!*/ loopHeaderToCallCmd1 = new Dictionary<Block/*!*/, CallCmd/*!*/>();
Dictionary<Block, CallCmd> loopHeaderToCallCmd2 = new Dictionary<Block, CallCmd>();
Dictionary<Block, AssignCmd> loopHeaderToAssignCmd = new Dictionary<Block, AssignCmd>();
foreach (Block/*!*/ header in g.Headers) {
Contract.Assert(header != null);
Contract.Assert(header != null);
List<Variable> inputs = new List<Variable>();
List<Variable> outputs = new List<Variable>();
List<Expr> callInputs1 = new List<Expr>();
List<IdentifierExpr> callOutputs1 = new List<IdentifierExpr>();
List<Expr> callInputs2 = new List<Expr>();
List<IdentifierExpr> callOutputs2 = new List<IdentifierExpr>();
List<AssignLhs> lhss = new List<AssignLhs>();
List<Expr> rhss = new List<Expr>();
Dictionary<Variable, Expr> substMap = new Dictionary<Variable, Expr>(); // Variable -> IdentifierExpr
List<Variable>/*!*/ targets = new List<Variable>();
HashSet<Variable> footprint = new HashSet<Variable>();
foreach (Block/*!*/ b in g.BackEdgeNodes(header))
{
Contract.Assert(b != null);
foreach (Block/*!*/ block in g.NaturalLoops(header, b))
{
Contract.Assert(block != null);
foreach (Cmd/*!*/ cmd in block.Cmds)
{
Contract.Assert(cmd != null);
cmd.AddAssignedVariables(targets);
VariableCollector c = new VariableCollector();
c.Visit(cmd);
footprint.UnionWith(c.usedVars);
}
}
}
List<IdentifierExpr>/*!*/ globalMods = new List<IdentifierExpr>();
Set targetSet = new Set();
foreach (Variable/*!*/ v in targets)
{
Contract.Assert(v != null);
if (targetSet.Contains(v))
continue;
targetSet.Add(v);
if (v is GlobalVariable)
globalMods.Add(new IdentifierExpr(Token.NoToken, v));
}
foreach (Variable v in impl.InParams) {
Contract.Assert(v != null);
if (!footprint.Contains(v)) continue;
callInputs1.Add(new IdentifierExpr(Token.NoToken, v));
Formal f = new Formal(Token.NoToken, new TypedIdent(Token.NoToken, "in_" + v.Name, v.TypedIdent.Type), true);
inputs.Add(f);
callInputs2.Add(new IdentifierExpr(Token.NoToken, f));
substMap[v] = new IdentifierExpr(Token.NoToken, f);
}
foreach (Variable v in impl.OutParams) {
Contract.Assert(v != null);
if (!footprint.Contains(v)) continue;
callInputs1.Add(new IdentifierExpr(Token.NoToken, v));
Formal f1 = new Formal(Token.NoToken, new TypedIdent(Token.NoToken, "in_" + v.Name, v.TypedIdent.Type), true);
inputs.Add(f1);
if (targetSet.Contains(v))
{
callOutputs1.Add(new IdentifierExpr(Token.NoToken, v));
Formal f2 = new Formal(Token.NoToken, new TypedIdent(Token.NoToken, "out_" + v.Name, v.TypedIdent.Type), false);
outputs.Add(f2);
callInputs2.Add(new IdentifierExpr(Token.NoToken, f2));
callOutputs2.Add(new IdentifierExpr(Token.NoToken, f2));
lhss.Add(new SimpleAssignLhs(Token.NoToken, new IdentifierExpr(Token.NoToken, f2)));
rhss.Add(new IdentifierExpr(Token.NoToken, f1));
substMap[v] = new IdentifierExpr(Token.NoToken, f2);
}
else
{
callInputs2.Add(new IdentifierExpr(Token.NoToken, f1));
substMap[v] = new IdentifierExpr(Token.NoToken, f1);
}
}
foreach (Variable v in impl.LocVars) {
Contract.Assert(v != null);
if (!footprint.Contains(v)) continue;
callInputs1.Add(new IdentifierExpr(Token.NoToken, v));
Formal f1 = new Formal(Token.NoToken, new TypedIdent(Token.NoToken, "in_" + v.Name, v.TypedIdent.Type), true);
inputs.Add(f1);
if (targetSet.Contains(v))
{
callOutputs1.Add(new IdentifierExpr(Token.NoToken, v));
Formal f2 = new Formal(Token.NoToken, new TypedIdent(Token.NoToken, "out_" + v.Name, v.TypedIdent.Type), false);
outputs.Add(f2);
callInputs2.Add(new IdentifierExpr(Token.NoToken, f2));
callOutputs2.Add(new IdentifierExpr(Token.NoToken, f2));
lhss.Add(new SimpleAssignLhs(Token.NoToken, new IdentifierExpr(Token.NoToken, f2)));
rhss.Add(new IdentifierExpr(Token.NoToken, f1));
substMap[v] = new IdentifierExpr(Token.NoToken, f2);
}
else
{
callInputs2.Add(new IdentifierExpr(Token.NoToken, f1));
substMap[v] = new IdentifierExpr(Token.NoToken, f1);
}
}
loopHeaderToInputs[header] = inputs;
loopHeaderToOutputs[header] = outputs;
loopHeaderToSubstMap[header] = substMap;
LoopProcedure loopProc = new LoopProcedure(impl, header, inputs, outputs, globalMods);
loopHeaderToLoopProc[header] = loopProc;
CallCmd callCmd1 = new CallCmd(Token.NoToken, loopProc.Name, callInputs1, callOutputs1);
callCmd1.Proc = loopProc;
loopHeaderToCallCmd1[header] = callCmd1;
CallCmd callCmd2 = new CallCmd(Token.NoToken, loopProc.Name, callInputs2, callOutputs2);
callCmd2.Proc = loopProc;
loopHeaderToCallCmd2[header] = callCmd2;
Debug.Assert(lhss.Count == rhss.Count);
if (lhss.Count > 0)
{
AssignCmd assignCmd = new AssignCmd(Token.NoToken, lhss, rhss);
loopHeaderToAssignCmd[header] = assignCmd;
}
}
// Keep track of the new blocks created: maps a header node to the
// header_last block that was created because of splitting header.
Dictionary<Block, Block> newBlocksCreated = new Dictionary<Block, Block>();
bool headRecursion = false; // testing an option to put recursive call before loop body
IEnumerable<Block> sortedHeaders = g.SortHeadersByDominance();
foreach (Block/*!*/ header in sortedHeaders)
{
Contract.Assert(header != null);
LoopProcedure loopProc = loopHeaderToLoopProc[header];
Dictionary<Block, Block> blockMap = new Dictionary<Block, Block>();
HashSet<string> dummyBlocks = new HashSet<string>();
CodeCopier codeCopier = new CodeCopier(loopHeaderToSubstMap[header]); // fix me
List<Variable> inputs = loopHeaderToInputs[header];
List<Variable> outputs = loopHeaderToOutputs[header];
int si_unique_loc = 1; // Added by AL: to distinguish the back edges
foreach (Block/*!*/ source in g.BackEdgeNodes(header)) {
Contract.Assert(source != null);
foreach (Block/*!*/ block in g.NaturalLoops(header, source)) {
Contract.Assert(block != null);
if (blockMap.ContainsKey(block))
continue;
Block newBlock = new Block();
newBlock.Label = block.Label;
if (headRecursion && block == header)
{
CallCmd callCmd = (CallCmd)(loopHeaderToCallCmd2[header]).Clone();
addUniqueCallAttr(si_unique_loc, callCmd);
si_unique_loc++;
newBlock.Cmds.Add(callCmd); // add the recursive call at head of loop
var rest = codeCopier.CopyCmdSeq(block.Cmds);
newBlock.Cmds.AddRange(rest);
}
else
newBlock.Cmds = codeCopier.CopyCmdSeq(block.Cmds);
blockMap[block] = newBlock;
if (newBlocksCreated.ContainsKey(block))
{
Block newBlock2 = new Block();
newBlock2.Label = newBlocksCreated[block].Label;
newBlock2.Cmds = codeCopier.CopyCmdSeq(newBlocksCreated[block].Cmds);
blockMap[newBlocksCreated[block]] = newBlock2;
}
//for detLoopExtract, need the immediate successors even outside the loop
if (detLoopExtract) {
GotoCmd auxGotoCmd = block.TransferCmd as GotoCmd;
Contract.Assert(auxGotoCmd != null && auxGotoCmd.labelNames != null &&
auxGotoCmd.labelTargets != null && auxGotoCmd.labelTargets.Count >= 1);
foreach(var bl in auxGotoCmd.labelTargets) {
bool found = false;
foreach(var n in g.NaturalLoops(header, source)) { //very expensive, can we do a contains?
if (bl == n) { //clarify: is this the right comparison?
found = true;
break;
}
}
if (!found) {
Block auxNewBlock = new Block();
auxNewBlock.Label = ((Block)bl).Label;
auxNewBlock.Cmds = codeCopier.CopyCmdSeq(((Block)bl).Cmds);
//add restoration code for such blocks
if (loopHeaderToAssignCmd.ContainsKey(header))
{
AssignCmd assignCmd = loopHeaderToAssignCmd[header];
auxNewBlock.Cmds.Add(assignCmd);
}
List<AssignLhs> lhsg = new List<AssignLhs>();
List<IdentifierExpr>/*!*/ globalsMods = loopHeaderToLoopProc[header].Modifies;
foreach (IdentifierExpr gl in globalsMods)
lhsg.Add(new SimpleAssignLhs(Token.NoToken, gl));
List<Expr> rhsg = new List<Expr>();
foreach (IdentifierExpr gl in globalsMods)
rhsg.Add(new OldExpr(Token.NoToken, gl));
if (lhsg.Count != 0)
{
AssignCmd globalAssignCmd = new AssignCmd(Token.NoToken, lhsg, rhsg);
auxNewBlock.Cmds.Add(globalAssignCmd);
}
blockMap[(Block)bl] = auxNewBlock;
}
}
}
}
List<Cmd> cmdSeq;
if (headRecursion)
cmdSeq = new List<Cmd>();
else
{
CallCmd callCmd = (CallCmd)(loopHeaderToCallCmd2[header]).Clone();
addUniqueCallAttr(si_unique_loc, callCmd);
si_unique_loc++;
cmdSeq = new List<Cmd> { callCmd };
}
Block/*!*/ block1 = new Block(Token.NoToken, source.Label + "_dummy",
new List<Cmd>{ new AssumeCmd(Token.NoToken, Expr.False) }, new ReturnCmd(Token.NoToken));
Block/*!*/ block2 = new Block(Token.NoToken, block1.Label,
cmdSeq, new ReturnCmd(Token.NoToken));
impl.Blocks.Add(block1);
dummyBlocks.Add(block1.Label);
GotoCmd gotoCmd = source.TransferCmd as GotoCmd;
Contract.Assert(gotoCmd != null && gotoCmd.labelNames != null && gotoCmd.labelTargets != null && gotoCmd.labelTargets.Count >= 1);
List<String>/*!*/ newLabels = new List<String>();
List<Block>/*!*/ newTargets = new List<Block>();
for (int i = 0; i < gotoCmd.labelTargets.Count; i++) {
if (gotoCmd.labelTargets[i] == header)
continue;
newTargets.Add(gotoCmd.labelTargets[i]);
newLabels.Add(gotoCmd.labelNames[i]);
}
newTargets.Add(block1);
newLabels.Add(block1.Label);
gotoCmd.labelNames = newLabels;
gotoCmd.labelTargets = newTargets;
blockMap[block1] = block2;
}
List<Block/*!*/>/*!*/ blocks = new List<Block/*!*/>();
Block exit = new Block(Token.NoToken, "exit", new List<Cmd>(), new ReturnCmd(Token.NoToken));
GotoCmd cmd = new GotoCmd(Token.NoToken,
new List<String> { cce.NonNull(blockMap[header]).Label, exit.Label },
new List<Block> { blockMap[header], exit });
if (detLoopExtract) //cutting the non-determinism
cmd = new GotoCmd(Token.NoToken,
new List<String> { cce.NonNull(blockMap[header]).Label },
new List<Block> { blockMap[header] });
Block entry;
List<Cmd> initCmds = new List<Cmd>();
if (loopHeaderToAssignCmd.ContainsKey(header)) {
AssignCmd assignCmd = loopHeaderToAssignCmd[header];
initCmds.Add(assignCmd);
}
entry = new Block(Token.NoToken, "entry", initCmds, cmd);
blocks.Add(entry);
foreach (Block/*!*/ block in blockMap.Keys) {
Contract.Assert(block != null);
Block/*!*/ newBlock = cce.NonNull(blockMap[block]);
GotoCmd gotoCmd = block.TransferCmd as GotoCmd;
if (gotoCmd == null) {
newBlock.TransferCmd = new ReturnCmd(Token.NoToken);
} else {
Contract.Assume(gotoCmd.labelNames != null && gotoCmd.labelTargets != null);
List<String> newLabels = new List<String>();
List<Block> newTargets = new List<Block>();
for (int i = 0; i < gotoCmd.labelTargets.Count; i++) {
Block target = gotoCmd.labelTargets[i];
if (blockMap.ContainsKey(target)) {
newLabels.Add(gotoCmd.labelNames[i]);
newTargets.Add(blockMap[target]);
}
}
if (newTargets.Count == 0) {
if (!detLoopExtract)
newBlock.Cmds.Add(new AssumeCmd(Token.NoToken, Expr.False));
newBlock.TransferCmd = new ReturnCmd(Token.NoToken);
} else {
newBlock.TransferCmd = new GotoCmd(Token.NoToken, newLabels, newTargets);
}
}
blocks.Add(newBlock);
}
blocks.Add(exit);
Implementation loopImpl =
new Implementation(Token.NoToken, loopProc.Name,
new List<TypeVariable>(), inputs, outputs, new List<Variable>(), blocks);
loopImpl.Proc = loopProc;
loopImpls.Add(loopImpl);
// Make a (shallow) copy of the header before splitting it
Block origHeader = new Block(header.tok, header.Label, header.Cmds, header.TransferCmd);
// Finally, add call to the loop in the containing procedure
string lastIterBlockName = header.Label + "_last";
Block lastIterBlock = new Block(Token.NoToken, lastIterBlockName, header.Cmds, header.TransferCmd);
newBlocksCreated[header] = lastIterBlock;
header.Cmds = new List<Cmd> { loopHeaderToCallCmd1[header] };
header.TransferCmd = new GotoCmd(Token.NoToken, new List<String> { lastIterBlockName }, new List<Block> { lastIterBlock });
impl.Blocks.Add(lastIterBlock);
blockMap[origHeader] = blockMap[header];
blockMap.Remove(header);
Contract.Assert(fullMap[impl.Name][header.Label] == header);
fullMap[impl.Name][header.Label] = origHeader;
foreach (Block block in blockMap.Keys)
{
// Don't add dummy blocks to the map
if (dummyBlocks.Contains(blockMap[block].Label)) continue;
// Following two statements are for nested loops: compose map
if (!fullMap[impl.Name].ContainsKey(block.Label)) continue;
var target = fullMap[impl.Name][block.Label];
AddToFullMap(fullMap, loopProc.Name, blockMap[block].Label, target);
}
fullMap[impl.Name].Remove(header.Label);
fullMap[impl.Name][lastIterBlockName] = origHeader;
}
}