public static FlowGraph Create(MethodIL il)
{
HashSet <int> bbStarts = GetBasicBlockStarts(il);
List <BasicBlock> bbs = new List <BasicBlock>();
void AddBB(int start, int count)
{
if (count > 0)
{
bbs.Add(new BasicBlock(start, count));
}
}
int prevStart = 0;
foreach (int ofs in bbStarts.OrderBy(o => o))
{
AddBB(prevStart, ofs - prevStart);
prevStart = ofs;
}
AddBB(prevStart, il.GetILBytes().Length - prevStart);
FlowGraph fg = new FlowGraph(bbs);
// We know where each basic block starts now. Proceed by linking them together.
ILReader reader = new ILReader(il.GetILBytes());
foreach (BasicBlock bb in bbs)
{
reader.Seek(bb.Start);
while (reader.HasNext)
{
Debug.Assert(fg.Lookup(reader.Offset) == bb);
ILOpcode opc = reader.ReadILOpcode();
if (opc.IsBranch())
{
int tar = reader.ReadBranchDestination(opc);
bb.Targets.Add(fg.Lookup(tar));
if (!opc.IsUnconditionalBranch())
{
bb.Targets.Add(fg.Lookup(reader.Offset));
}
break;
}
if (opc == ILOpcode.switch_)
{
uint numCases = reader.ReadILUInt32();
int jmpBase = reader.Offset + checked ((int)(numCases * 4));
bb.Targets.Add(fg.Lookup(jmpBase));
for (uint i = 0; i < numCases; i++)
{
int caseOfs = jmpBase + (int)reader.ReadILUInt32();
bb.Targets.Add(fg.Lookup(caseOfs));
}
break;
}
if (opc == ILOpcode.ret || opc == ILOpcode.endfinally || opc == ILOpcode.endfilter || opc == ILOpcode.throw_ || opc == ILOpcode.rethrow)
{
break;
}
reader.Skip(opc);
// Check fall through
if (reader.HasNext)
{
BasicBlock nextBB = fg.Lookup(reader.Offset);
if (nextBB != bb)
{
// Falling through
bb.Targets.Add(nextBB);
break;
}
}
}
}
foreach (BasicBlock bb in bbs)
{
foreach (BasicBlock tar in bb.Targets)
{
tar.Sources.Add(bb);
}
}
return(fg);
}
