non trivial loop unrolling

I have the following non trivial loop that does 10 iterations and stops (computes n over k)

#include <stdio.h>#include <stdlib.h>int main(int argc,char **argv){    int d=1;    bool f = true;    unsigned int j  = 1;    unsigned int n  = 3;    unsigned int k  = 2;    unsigned int m0 = 0;    unsigned int I[2];    I[0]=m0;    while (j != -1)    {        if (j == k)             { f=false;               j--;      }        else if (f)             { f=true ; I[j]=I[j-1]+1;j++;      }        else if (I[j] >= n-k+j) { f=false;               j--;      }        else                    { f=true ; I[j]=I[j  ]+1;j++; d++; }    }    printf("num subsets = %d\n",d);    return 0;}

I'm trying to force llvm/clang to unroll the loop, but fail to do so:

$ clang++ -c -O3 -emit-llvm main.cpp -o main.bc$ llvm-dis main.bc -o main.ll$ sed -n '23,34p;35q' main.llwhile.cond:                                       ; preds = %while.cond.backedge, %while.cond.outer  %j.0 = phi i32 [ %j.0.ph, %while.cond.outer ], [ %j.0.be, %while.cond.backedge ]  %f.0 = phi i1 [ true, %while.cond.outer ], [ %f.0.be, %while.cond.backedge ]  switch i32 %j.0, label %if.else [    i32 -1, label %while.end    i32 2, label %while.cond.backedge  ]while.cond.backedge:                              ; preds = %while.cond, %if.then2, %if.then12  %j.0.be = phi i32 [ %inc, %if.then2 ], [ %dec13, %if.then12 ], [ 1, %while.cond ]  %f.0.be = phi i1 [ true, %if.then2 ], [ false, %if.then12 ], [ false, %while.cond ]  br label %while.cond

So it looks like the loop is still there. Actually, even I use n=2, and the loop does only 4 iterations, unrolling fails. Any way to force llvm/clang to unroll this? gcc?