public bool SimplifyCustomShortCircuit(List <ILNode> body, ILBasicBlock head, int pos)
{
Debug.Assert(body.Contains(head));
// --- looking for the following pattern ---
// stloc(targetVar, leftVar)
// brtrue(exitLabel, call(op_False, leftVar)
// br(followingBlock)
//
// FollowingBlock:
// stloc(targetVar, call(op_BitwiseAnd, leftVar, rightExpression))
// br(exitLabel)
// ---
if (head.Body.Count < 3)
{
return(false);
}
// looking for:
// stloc(targetVar, leftVar)
ILVariable targetVar;
ILExpression targetVarInitExpr;
if (!head.Body[head.Body.Count - 3].Match(ILCode.Stloc, out targetVar, out targetVarInitExpr))
{
return(false);
}
ILVariable leftVar;
if (!targetVarInitExpr.Match(ILCode.Ldloc, out leftVar))
{
return(false);
}
// looking for:
// brtrue(exitLabel, call(op_False, leftVar)
// br(followingBlock)
ILExpression callExpr;
ILLabel exitLabel;
ILLabel followingBlock;
if (!head.MatchLastAndBr(ILCode.Brtrue, out exitLabel, out callExpr, out followingBlock))
{
return(false);
}
if (labelGlobalRefCount[followingBlock] > 1)
{
return(false);
}
IMethod opFalse;
ILExpression opFalseArg;
if (!callExpr.Match(ILCode.Call, out opFalse, out opFalseArg))
{
return(false);
}
// ignore operators other than op_False and op_True
if (opFalse.Name != "op_False" && opFalse.Name != "op_True")
{
return(false);
}
if (!opFalseArg.MatchLdloc(leftVar))
{
return(false);
}
ILBasicBlock followingBasicBlock = labelToBasicBlock[followingBlock];
// FollowingBlock:
// stloc(targetVar, call(op_BitwiseAnd, leftVar, rightExpression))
// br(exitLabel)
ILVariable _targetVar;
ILExpression opBitwiseCallExpr;
ILLabel _exitLabel;
if (!followingBasicBlock.MatchSingleAndBr(ILCode.Stloc, out _targetVar, out opBitwiseCallExpr, out _exitLabel))
{
return(false);
}
if (_targetVar != targetVar || exitLabel != _exitLabel)
{
return(false);
}
IMethod opBitwise;
ILExpression leftVarExpression;
ILExpression rightExpression;
if (!opBitwiseCallExpr.Match(ILCode.Call, out opBitwise, out leftVarExpression, out rightExpression))
{
return(false);
}
if (!leftVarExpression.MatchLdloc(leftVar))
{
return(false);
}
// ignore operators other than op_BitwiseAnd and op_BitwiseOr
if (opBitwise.Name != "op_BitwiseAnd" && opBitwise.Name != "op_BitwiseOr")
{
return(false);
}
// insert:
// stloc(targetVar, LogicAnd(C::op_BitwiseAnd, leftVar, rightExpression)
// br(exitLabel)
ILCode op = opBitwise.Name == "op_BitwiseAnd" ? ILCode.LogicAnd : ILCode.LogicOr;
if (op == ILCode.LogicAnd && opFalse.Name != "op_False")
{
return(false);
}
if (op == ILCode.LogicOr && opFalse.Name != "op_True")
{
return(false);
}
ILExpression shortCircuitExpr = MakeLeftAssociativeShortCircuit(op, opFalseArg, rightExpression);
shortCircuitExpr.Operand = opBitwise;
Debug.Fail("Preserve ILRanges"); //TODO: Could never trigger this code path. Tested many asms.
var tail = head.Body.RemoveTail(ILCode.Stloc, ILCode.Brtrue, ILCode.Br);
//TODO: Keep tail's ILRanges
//TODO: Keep ILRanges of other things that are removed by this method
head.Body.Add(new ILExpression(ILCode.Stloc, targetVar, shortCircuitExpr));
head.Body.Add(new ILExpression(ILCode.Br, exitLabel));
body.Remove(followingBasicBlock);
return(true);
}
List <ILNode> FindLoops(HashSet <ControlFlowNode> scope, ControlFlowNode entryPoint, bool excludeEntryPoint)
{
List <ILNode> result = new List <ILNode>();
// Do not modify entry data
scope = new HashSet <ControlFlowNode>(scope);
Queue <ControlFlowNode> agenda = new Queue <ControlFlowNode>();
agenda.Enqueue(entryPoint);
while (agenda.Count > 0)
{
ControlFlowNode node = agenda.Dequeue();
// If the node is a loop header
if (scope.Contains(node) &&
node.DominanceFrontier.Contains(node) &&
(node != entryPoint || !excludeEntryPoint))
{
HashSet <ControlFlowNode> loopContents = FindLoopContent(scope, node);
// If the first expression is a loop condition
ILBasicBlock basicBlock = (ILBasicBlock)node.UserData;
ILExpression condExpr;
ILLabel trueLabel;
ILLabel falseLabel;
// It has to be just brtrue - any preceding code would introduce goto
if (basicBlock.MatchSingleAndBr(ILCode.Brtrue, out trueLabel, out condExpr, out falseLabel))
{
ControlFlowNode trueTarget;
labelToCfNode.TryGetValue(trueLabel, out trueTarget);
ControlFlowNode falseTarget;
labelToCfNode.TryGetValue(falseLabel, out falseTarget);
// If one point inside the loop and the other outside
if ((!loopContents.Contains(trueTarget) && loopContents.Contains(falseTarget)) ||
(loopContents.Contains(trueTarget) && !loopContents.Contains(falseTarget)))
{
loopContents.RemoveOrThrow(node);
scope.RemoveOrThrow(node);
// If false means enter the loop
if (loopContents.Contains(falseTarget) || falseTarget == node)
{
// Negate the condition
condExpr = new ILExpression(ILCode.LogicNot, null, condExpr);
ILLabel tmp = trueLabel;
trueLabel = falseLabel;
falseLabel = tmp;
}
ControlFlowNode postLoopTarget;
labelToCfNode.TryGetValue(falseLabel, out postLoopTarget);
if (postLoopTarget != null)
{
// Pull more nodes into the loop
HashSet <ControlFlowNode> postLoopContents = FindDominatedNodes(scope, postLoopTarget);
var pullIn = scope.Except(postLoopContents).Where(n => node.Dominates(n));
loopContents.UnionWith(pullIn);
}
// Use loop to implement the brtrue
basicBlock.Body.RemoveTail(ILCode.Brtrue, ILCode.Br);
basicBlock.Body.Add(new ILWhileLoop()
{
Condition = condExpr,
BodyBlock = new ILBlock()
{
EntryGoto = new ILExpression(ILCode.Br, trueLabel),
Body = FindLoops(loopContents, node, false)
}
});
basicBlock.Body.Add(new ILExpression(ILCode.Br, falseLabel));
result.Add(basicBlock);
scope.ExceptWith(loopContents);
}
}
// Fallback method: while(true)
if (scope.Contains(node))
{
result.Add(new ILBasicBlock()
{
Body = new List <ILNode>()
{
new ILLabel()
{
Name = "Loop_" + (nextLabelIndex++)
},
new ILWhileLoop()
{
BodyBlock = new ILBlock()
{
EntryGoto = new ILExpression(ILCode.Br, (ILLabel)basicBlock.Body.First()),
Body = FindLoops(loopContents, node, true)
}
},
},
});
scope.ExceptWith(loopContents);
}
}
// Using the dominator tree should ensure we find the the widest loop first
foreach (var child in node.DominatorTreeChildren)
{
agenda.Enqueue(child);
}
}
// Add whatever is left
foreach (var node in scope)
{
result.Add((ILNode)node.UserData);
}
scope.Clear();
return(result);
}
