public static IList <TreeStatement> BuildAST(this Subprogram src)
{
IList <BasicBlock> bblist = src.GetBasicBlocks();
Dictionary <BasicBlock, IEnumerable <BasicBlock> > pred = bblist.Select(bb =>
new KeyValuePair <BasicBlock, IEnumerable <BasicBlock> >(bb,
bblist.Where(bbel => bbel.Successor == bb || bbel.Target == bb))).
ToDictionary(kvp => kvp.Key, kvp => kvp.Value);
// Determine dominators.
Dictionary <BasicBlock, List <BasicBlock> > dom = bblist.Select(bb =>
new KeyValuePair <BasicBlock, List <BasicBlock> >(bb,
bb == src.CFGRoot ? new List <BasicBlock> {
src.CFGRoot
} : bblist.ToList())).
ToDictionary(kvp => kvp.Key, kvp => kvp.Value);
bool changes = true;
while (changes)
{
changes = false;
foreach (BasicBlock n in bblist)
{
if (n != src.CFGRoot)
{
IEnumerable <BasicBlock> doms = null;
foreach (BasicBlock p in pred[n])
{
doms = (doms == null) ? dom[p] : doms.Intersect(dom[p]);
}
doms = doms.Union(new [] { n });
if (!doms.SequenceEqual(dom[n]))
{
changes = true;
dom[n] = new List <BasicBlock>(doms);
}
}
}
}
// Perform depth-first enumeration.
Dictionary <BasicBlock, int> dfn = bblist.Select(bb =>
new KeyValuePair <BasicBlock, int>(bb, 0)).
ToDictionary(kvp => kvp.Key, kvp => kvp.Value);
int c = bblist.Count;
NumDepth(src.CFGRoot, dfn, ref c, new List <BasicBlock>());
// Test CFG reducibility: each retreating edge must be back edge.
foreach (BasicBlock sbb in bblist)
{
foreach (BasicBlock tbb in new [] { sbb.Successor, sbb.Target })
{
if (tbb != null && dfn[tbb] < dfn[sbb] && !dom[sbb].Contains(tbb))
{
throw new IrreducibleCFGException("There is non-back retreating edge");
}
}
}
if (bblist.Where(bb => bb.Trailer.OpCode == IROpCodes.RET).Count() != 1)
{
throw new IrreducibleCFGException("Control flow graph must have single node with RET ending");
}
List <TreeStatement> code = new List <TreeStatement>();
BasicBlock cur = src.CFGRoot;
GraphPathFinder path_finder = new GraphPathFinder(bblist);
while (cur != null)
{
cur = HandleStatement(cur, null, bblist, pred, dom, path_finder, code);
}
return(code.AsReadOnly());
}
