private static void Lift(GotoStatement stmt)
{
AstBlock block = ParentBlock(stmt.Goto);
AstBlock[] path = BackwardsPath(block, ParentBlock(stmt.Label));
AstBlock loopFirstStmt = path[path.Length - 1];
if (loopFirstStmt.Type == AstBlockType.Else)
{
loopFirstStmt = Previous(loopFirstStmt) as AstBlock;
if (loopFirstStmt == null || loopFirstStmt.Type != AstBlockType.If)
{
throw new InvalidOperationException("Found an else without a matching if.");
}
}
AstBlock newBlock = EncloseDoWhile(stmt, block, loopFirstStmt);
block.Remove(stmt.Goto);
newBlock.AddFirst(stmt.Goto);
stmt.IsLoop = false;
}
private static void EncloseSingleInst(GotoStatement stmt, Instruction inst)
{
AstBlock block = ParentBlock(stmt.Goto);
AstBlock newBlock = new AstBlock(AstBlockType.If, stmt.Condition);
block.AddAfter(stmt.Goto, newBlock);
newBlock.AddFirst(new AstOperation(inst));
}
private static void MoveInward(GotoStatement stmt)
{
AstBlock block = ParentBlock(stmt.Goto);
AstBlock[] path = BackwardsPath(block, ParentBlock(stmt.Label));
for (int index = path.Length - 1; index >= 0; index--)
{
AstBlock child = path[index];
AstBlock last = child;
if (child.Type == AstBlockType.If)
{
// Modify the if condition to allow it to be entered by the goto.
if (!ContainsCondComb(child.Condition, Instruction.LogicalOr, stmt.Condition))
{
child.OrCondition(stmt.Condition);
}
}
else if (child.Type == AstBlockType.Else)
{
// Modify the matching if condition to force the else to be entered by the goto.
if (!(Previous(child) is AstBlock ifBlock) || ifBlock.Type != AstBlockType.If)
{
throw new InvalidOperationException("Found an else without a matching if.");
}
IAstNode cond = InverseCond(stmt.Condition);
if (!ContainsCondComb(ifBlock.Condition, Instruction.LogicalAnd, cond))
{
ifBlock.AndCondition(cond);
}
last = ifBlock;
}
Enclose(block, AstBlockType.If, stmt.Condition, Next(stmt.Goto), last);
block.Remove(stmt.Goto);
child.AddFirst(stmt.Goto);
block = child;
}
}