A question about loop-unroll

[Revital1 Eres]

Hello,

Is there a way to pass to the unroller the maximum number of iterations
of the loop such that it can decide to avoid unrolling if
the maximum number  is small.

To be more specific, I am referring to the following case:
After the vectorizer decides to peel for alignment
it creates three loops:
[1] scalar loop - the prologue to align
    memory access.
[2] the vecorized loop
[3] scalar loop - the remaining scalar computations.

If the unroller does not know the number of  iterations at compile time
it unrolls loops with run-time checks in the following way
(taken from loop-unroll.c):

   for (i = 0; i < n; i++)
     body;

   ==>

   i = 0;
   mod = n % 4;

   switch (mod)
     {
       case 3:
         body; i++;
       case 2:
         body; i++;
       case 1:
         body; i++;
       case 0: ;
     }

   while (i < n)
     {
       body; i++;
       body; i++;
       body; i++;
       body; i++;
     }


The vectorizer knowns at compile time the maximum number of iterations
that will be needed for the prologue and the epilogue. In some cases
seems there is no need to unroll and create redundant loops.

Thanks,
Revital