ssa-chrec-09.c

来自「Mac OS X 10.4.9 for x86 Source Code gcc」· C语言 代码 · 共 43 行

/* APPLE LOCAL file lno */
/* { dg-do compile } */ 
/* { dg-options "-O1 -floop-test -fdump-tree-lptest-details" } */

int main(void)
{
  int a = -100;
  int b = 2;
  int c = 3;
  int d = 4;
  int e = 5;
  
  while (a)
    {
      /* Exercises the cycle detector: a -> b -> (c -> d -> e -> c)*.  */
      a += b;
      b += c;
      c += d;
      d += e;
      e += c;
    }
}

/* This is what is commonly called a "mixer".  It whirls the data in a
   strongly connected component.  We expect the following evolution
   functions:

   e  ->  {5, +, c_13}_1
   d  ->  {4, +, {5, +, c_13}_1}_1
   c  ->  {3, +, {4, +, {5, +, c_13}_1}_1}_1
   b  ->  {2, +, {3, +, {4, +, {5, +, c_13}_1}_1}_1}_1
   a  ->  {-100, +, {2, +, {3, +, {4, +, {5, +, c_13}_1}_1}_1}_1}_1
*/

/* FIXME:
   For the moment this testcase does not test for anything, but for
   not ICEing, and for documentation purposes (okay here is the
   definition of a mixer).  However, I'm considering testing something
   around the lines of ssa-chrec-08.c, ie.  build two mixers, and then
   compare their values.  But that is difficult, and low priority.  */