public static void DoSplitBlocksIntoAssignmentsAndPredicates(ControlFlowGraph cfg)
{
cfg.Vertices.ForEach(v =>
{
if (v.BalancedCode.IsEmpty() || v.Residue.IsEmpty())
{
return;
}
var ass = (v.BalancedCode.Last() is Assign) ? v.BalancedCode.Last().AssertCast <Assign>() : null;
var lhs = ass == null ? null : ass.Lhs.AssertCast <Ref>().Sym;
var @ref = v.Residue.AssertSingle() is Ref ? v.Residue.AssertSingle().AssertCast <Ref>().Sym : null;
if (lhs != null && @ref != null && lhs.ProtoId == @ref.ProtoId)
{
// todo. this introduces a nasty bug if assigned variable is reused later
v.BalancedCode.RemoveLast();
v.Residue.SetElements(ass.Rhs);
}
if (v.BalancedCode.IsEmpty() || v.Residue.IsEmpty())
{
return;
}
var v_test = new ControlFlowBlock();
v_test.Residue.Add(v.Residue.AssertSingle());
v.Residue.RemoveElements();
var outEdges = cfg.Vedges(v, null);
cfg.RemoveEdges(outEdges);
cfg.AddVertex(v_test);
cfg.AddEdge(new ControlFlowEdge(v, v_test));
outEdges.ForEach(e => cfg.AddEdge(new ControlFlowEdge(v_test, e.Target, e.Tag)));
});
}
public static ControlFlowGraph DoCreateCarcass(IMethodBody cil, out ReadOnlyDictionary <ControlFlowBlock, ReadOnlyCollection <IILOp> > blocks2parts)
{
// create the control flow graph
var cfg = new ControlFlowGraph();
// partition the code into blocks with continuous control flow
// todo. support switches and protected regions
var targets = new HashSet <IILOp>(cil.OfType <Branch>().Select(br => br.Target));
var l_partitions = new List <ReadOnlyCollection <IILOp> >();
var l_partition = new List <IILOp>();
Action qualifyPartition = () => { if (l_partition.IsNotEmpty())
{
l_partitions.Add(l_partition.ToReadOnly()); l_partition = new List <IILOp>();
}
};
foreach (var op in cil)
{
if (op is Branch || op is Ret)
{
qualifyPartition();
}
else
{
if (targets.Contains(op))
{
qualifyPartition();
}
l_partition.Add(op);
if (op is Throw)
{
qualifyPartition();
}
}
}
qualifyPartition();
var partitions = l_partitions.ToReadOnly();
// create blocks and map those to ops and partitions
blocks2parts = partitions.ToDictionary(p => new ControlFlowBlock(), p => p).ToReadOnly();
blocks2parts.ForEach(kvp => cfg.AddVertex(kvp.Key));
var op2blocks = new Dictionary <IILOp, ControlFlowBlock>();
blocks2parts.ForEach(kvp => kvp.Value.ForEach(op => op2blocks.Add(op, kvp.Key)));
cil.ForEach(op => { if (!op2blocks.ContainsKey(op))
{
op2blocks.Add(op, null);
}
});
// prepare to link the blocks
Action <IILOp, IILOp, CilPredicateType?> link = (op1, op2, cil_pred) =>
{
var source = op1 == null ? cfg.Start : op2blocks[op1];
var target = op2 == null ? cfg.Finish : op2blocks[op2];
var hir_pred = cil_pred == null ? (HirPredicateType?)null :
(HirPredicateType)Enum.Parse(typeof(HirPredicateType), cil_pred.Value.ToString());
cfg.AddEdge(new ControlFlowEdge(source, target, hir_pred));
};
// link the blocks (down from 300+ LOC to this simple loop =))
if (cil.IsEmpty())
{
link(null, null, null);
}
foreach (var op in cil)
{
// todo. support switches here
if (op is Switch)
{
throw AssertionHelper.Fail();
}
// todo. support general case of control flow
// n0te. throw needs something on stack, so br > throw is impossible
Func <IILOp, bool> isJmp = op1 => op1 is Ret || op1 is Branch;
if (isJmp(op) && isJmp(op.Prev))
{
continue;
}
if (isJmp(op))
{
Func <IILOp, CilPredicateType?> pred = op1 => op1 is Ret ? null : op1 is Branch ? ((Branch)op1).PredicateType : ((Func <CilPredicateType?>)(() => { throw AssertionHelper.Fail(); }))();
Func <IILOp, bool> uncond = op1 => isJmp(op1) && pred(op1) == null;
Func <IILOp, bool> cond = op1 => isJmp(op1) && pred(op1) != null;
Func <IILOp, IILOp> target = null; target = op1 =>
op1 is Ret ? null : op1 is Branch?target(((Branch)op1).Target) : op1;
(target(op) is Branch).AssertFalse();
if (target(op) is Ret)
{
link(op.Prev, null, pred(op));
}
else
{
link(op.Prev, target(op), pred(op));
}
isJmp(op.Next).AssertImplies(uncond(op.Next));
if (cond(op))
{
link(op.Prev, target(op.Next), pred(op).Negate());
}
}
else if (op is Throw)
{
// do nothing - throw doesn't create links
}
else
{
if (op.Prev == null)
{
link(null, op, null);
}
if (isJmp(op.Next))
{
continue;
}
var blk = op2blocks.GetOrDefault(op);
var blk_next = op2blocks.GetOrDefault(op.Next);
if (blk != blk_next)
{
link(op, op.Next, null);
}
}
}
// yield control to the next step of the pipeline
return(cfg);
}
