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 RemoveEmptyBlocks(AstBlock mainBlock)
{
Queue <AstBlock> pending = new Queue <AstBlock>();
pending.Enqueue(mainBlock);
while (pending.TryDequeue(out AstBlock block))
{
foreach (IAstNode node in block)
{
if (node is AstBlock childBlock)
{
pending.Enqueue(childBlock);
}
}
AstBlock parent = block.Parent;
if (parent == null)
{
continue;
}
AstBlock nextBlock = Next(block) as AstBlock;
bool hasElse = nextBlock != null && nextBlock.Type == AstBlockType.Else;
bool isIf = block.Type == AstBlockType.If;
if (block.Count == 0)
{
if (isIf)
{
if (hasElse)
{
nextBlock.TurnIntoIf(InverseCond(block.Condition));
}
parent.Remove(block);
}
else if (block.Type == AstBlockType.Else)
{
parent.Remove(block);
}
}
else if (isIf && parent.Type == AstBlockType.Else && parent.Count == (hasElse ? 2 : 1))
{
AstBlock parentOfParent = parent.Parent;
parent.Remove(block);
parentOfParent.AddAfter(parent, block);
if (hasElse)
{
parent.Remove(nextBlock);
parentOfParent.AddAfter(block, nextBlock);
}
parentOfParent.Remove(parent);
block.TurnIntoElseIf();
}
}
}
private static void MoveOutward(GotoStatement stmt, int gLevel, int lLevel)
{
AstBlock origin = ParentBlock(stmt.Goto);
AstBlock block = origin;
// Check if a loop is enclosing the goto, and the block that is
// directly related to the label is above the loop block.
// In that case, we need to introduce a break to get out of the loop.
AstBlock loopBlock = origin;
int loopLevel = gLevel;
while (loopLevel > lLevel)
{
AstBlock child = loopBlock;
loopBlock = loopBlock.Parent;
loopLevel--;
if (child.Type == AstBlockType.DoWhile)
{
EncloseSingleInst(stmt, Instruction.LoopBreak);
block.Remove(stmt.Goto);
loopBlock.AddAfter(child, stmt.Goto);
block = loopBlock;
gLevel = loopLevel;
}
}
// Insert ifs to skip the parts that shouldn't be executed due to the goto.
bool tryInsertElse = stmt.IsUnconditional && origin.Type == AstBlockType.If;
while (gLevel > lLevel)
{
Enclose(block, AstBlockType.If, stmt.Condition, Next(stmt.Goto));
block.Remove(stmt.Goto);
AstBlock child = block;
// We can't move the goto in the middle of a if and a else block, in
// this case we need to move it after the else.
// IsLoop may need to be updated if the label is inside the else, as
// introducing a loop is the only way to ensure the else will be executed.
if (Next(child) is AstBlock elseBlock && elseBlock.Type == AstBlockType.Else)
{
child = elseBlock;
}
block = block.Parent;
block.AddAfter(child, stmt.Goto);
gLevel--;
if (tryInsertElse && child == origin)
{
AstBlock lBlock = ParentBlock(stmt.Label);
IAstNode last = block == lBlock && !stmt.IsLoop ? stmt.Label : null;
AstBlock newBlock = Enclose(block, AstBlockType.Else, null, Next(stmt.Goto), last);
if (newBlock != null)
{
block.Remove(stmt.Goto);
block.AddAfter(newBlock, stmt.Goto);
}
}
}
}