UnrollLoop

(twinBASIC) Asks the LLVM compiler to unroll the loop that contains it, for speed.

Syntax: UnrollLoop [ maxloopunrollcount ]

maxloopunrollcount: optional The greatest number of times the loop body may be repeated in one unrolled iteration. It must be a literal Integer or Long value from 0 to 2,147,483,647, or the name of a constant that has such a value. A variable, an expression such as 2 + 2, a negative number or a non-integer is compile error TB5023, expected a literal Integer or Long value.

Unrolling a loop repeats its body several times in each iteration, so that the loop tests its condition and jumps back less often. UnrollLoop is a hint to the LLVM compiler: it does not change what the loop does, only how the compiled code is laid out. Code that is not compiled with LLVM ignores it.

UnrollLoop must be the first statement in the body of a For…Next, Do While…Loop, Do Until…Loop or While…Wend loop. Comments, blank lines and Dim statements may come before it. Anywhere else — before or after the loop, after another statement in the body, inside an If block in the body, in a For Each…Next loop, or in a Do…Loop with its condition at the end or with none — it is compile error TB5023, UnrollLoop() must appear immediately inside the start of a For/While loop.

It can be written with or without parentheses and qualified or not: UnrollLoop 4, UnrollLoop(4) and Compilation.UnrollLoop 4 are the same.

Note

UnrollLoop is a twinBASIC extension. VBA and VB6 have no such statement.

Example

Function SumOfSquares(ByVal Count As Long) As Double
    Dim i As Long
    For i = 1 To Count
        UnrollLoop 4
        SumOfSquares = SumOfSquares + CDbl(i) * i
    Next
End Function

UnrollLoop

Example

See Also