public override Value Visit(ForLoop node)
{
// store startval, id
// forloop:
// body
// idval = load id
// incr/decr idval
// store idval, id
// cmp idval, endval
// br slt/sgt forloop, forend
// forend:
// NOTE: it is invalid to modify the id var inside the loop
// func was set in Visit(RoutineDefinition node)
Function func = evalCtx.func;
Value id = traverse(node.var);
Value startval = traverse(node.start);
Value endval = traverse(node.end);
builder.BuildStore(startval, id);
Debug.Assert(!id.IsNull, "Invalid For var id");
Debug.Assert(!startval.IsNull, "Invalid For start value");
Debug.Assert(!endval.IsNull, "Invalid For end value");
BasicBlock forloop = func.AppendBasicBlock("forloop");
BasicBlock forend = func.AppendBasicBlock("forend");
evalCtx.EnterLoop(forloop, forend);
builder.BuildBr(forloop);
builder.ResetInsertPoint(func, forloop);
Value body = traverse(node.block);
Debug.Assert(!body.IsNull, "Invalid For loop body");
// emit the step and test
Value idval = builder.BuildLoad(id);
if (node.direction > 0) // incr
{
idval = builder.BuildAdd(idval, Value.CreateConstInt32(1));
}
else // decr
{
idval = builder.BuildSub(idval, Value.CreateConstInt32(1));
}
builder.BuildStore(idval, id); // persist the final value after the For
var op = (node.direction > 0) ? LLVMIntPredicate.IntULT : LLVMIntPredicate.IntUGT;
Value cmpres = builder.BuildICmp(idval, op, endval);
builder.BuildCondBr(cmpres, forloop, forend);
builder.ResetInsertPoint(func, forend);
evalCtx.LeaveLoop();
return(Value.NonNull);
}