public static ControlFlowGraph Create(LingoCode code)
{
//TODO: Remove temp comment rambling
//TODO: For later tranforms, check BBs which are "pure" and only exist as a exit and as "a jumper". BB.Body.Count == 1
//TODO: Number the blocks topologically or nah? BB.Ordinal?
var builder = new ControlFlowGraphBuilder();
var forwardBranches = new Dictionary <Instruction, BasicBlock>(code.JumpExits.Count);
var backEdges = new Dictionary <Jumper, BasicBlock>();
Range currentBlockRange = default; //0..0
for (int i = 0; i < code.Count; i++)
{
Instruction instruction = code[i];
//We are hunting here for those dangling JumpExits. If we find one which is a back-edge exit, we break and leave that to be targeted for future.
if (code.JumpExits.ContainsValue(instruction)) //TODO: if the jumpExit OP = Return -> BBKind.Exit, or have another round for transformations like that? //TODO: Check how much ContainsValue slows this down
{
currentBlockRange = currentBlockRange.End..i;
if (!currentBlockRange.Equals(i..i))
{
builder.CurrentBlock.Body = code[currentBlockRange];
}
if (forwardBranches.TryGetValue(instruction, out var successor))
{
//Resolving the forward-edge
if (builder.CurrentBlock.FallThrough == null) //TODO: Doesn't feel right? Maybe abuse the shit out of CurrentBlock getter-setter?
{
builder.AppendBlock(successor); //If
}
else
{
builder.AddBlock(successor); //usually If-Else
}
}
else
{
//Back-edge target
var nextBlock = new BasicBlock();
backEdges.Add(code.GetJumperEntry(instruction), nextBlock);
builder.AppendBlock(nextBlock);
}
}
if (Jumper.IsValid(instruction.OP))
{
Jumper jumper = (Jumper)instruction;
currentBlockRange = currentBlockRange.End..(i + 1);
builder.CurrentBlock.Body = code[currentBlockRange];
if (code.IsBackwardsJump(jumper))
{
//Fallthrough back-edge jumper
builder.LinkBlocks(builder.CurrentBlock, backEdges[jumper]);
}
else
{
//Forward jump to successor
if (!forwardBranches.TryGetValue(code.JumpExits[jumper], out BasicBlock successor))
{
forwardBranches.Add(code.JumpExits[jumper], successor = new BasicBlock());
}
builder.LinkBlocks(builder.CurrentBlock, successor);
if (Jumper.IsConditional(instruction.OP))
{
builder.AppendBlock(new BasicBlock(), isConditionalBranch: true);
}
}
}
}
currentBlockRange = currentBlockRange.End..code.Count;
builder.CurrentBlock.Body = code[currentBlockRange];
builder.AppendBlock(new BasicBlock(BasicBlockKind.Exit)); //TODO:
return(new ControlFlowGraph()
{
Blocks = builder.Blocks
});
}