HP-UX 11i Tuning and Performance

11.11. Code to Demonstrate Optimization Effects

The following simple code can be used to observe the effects of optimization at the different levels and for different architectures:

					main()
					{
					int i,j,k,l,m,n;
					for (i=0; i<2; i++)
					{
					j=i*5; /* constant multiplication */
					k=j*1000; /* constant multiplication */
					l=i+1;
					m=l*j; /* variable multiplication */
					printf("loop=%d, j=%d, k=%d, m=%d\n",i,j,k,m);
					}
					}
				

This code, when compiled with different options, results in quite a variety of performance characteristics. Some of this is revealed in the assembly language view of the compiled code. Using the command cc +DA1.0 -go intnoopt int.c, the code is compiled with no optimization. (The same output is obtained using +DA1.1.) The result is shown in the following ...