clock() is not a satisfactory timer for this benchmark. Whoever produced this modified version had to make it repeat far more than the original just to make it run long enough to be timed by clock(). Unfortunately, Standard C doesn't include a satisfactory timer function.
The point of s162() is to see whether the compiler recognizes the direction of data overlap, seeing that it will never be executed with a negative overlap. It's possible that when interprocedural optimization succeeds, the compiler sees that the overlap is a compile time constant and can eliminate the conditional as well as propagate the constant overlap into the code. There are other tests in this suite intended to concentrate on that.
In the original version of this benchmark http://www.netlib.org/benchmark/vectord loops of length 1000 are timed without extra repetitions. The shorter loops are repeated so as to process as much data as the longer one, but repeating over the same cached data, Many of these tests run around 100 microseconds on 2.6Ghz coreI7-2, so a timer with microsecond resolution is needed.
I ran some tests this week on linux with various timers and got reports of microsecond resolution with Intel Openmp omp_get_wtime(). I believe it's nearly that good on Windows. On linux, gettimeofday() is expected to work as well.