rentsch@unc.UUCP (04/16/87)
In article <2577@intelca.UUCP> clif@intelca.UUCP (Clif Purkiser) writes: > While, I agree that using a global optimizing compiler is not exactly > kosher for the dhrystone benchmark it sometimes neccessary. For > instance: the GreenHills C compiler is a globally optimizing compiler > which generates good Dhrystone numbers for many architectures including > the 80386 and 68020. Unfortunately, I can not find a compiler > switch to turn off the global optimizer. This leaves me with two choices: > post the numbers with the cavet that this a global optimizing compiler > or use the results of a medicore compiler like CC. I don't really > think that global optimization is a problem as long as it is clearly > labeled. I see this drawback as saying something not about the suitability of optimizing compilers but about the suitability of the Dhrystone program as a benchmark. If Dhrystone really is prone to sweeping global optimizations (with corresponding improvements in running time), then doesn't it seem to be pretty poor as a benchmark? I heard a similar about a program used to benchmark an early FORTRAN H compiler -- the global optimizer reduced the entire program to just a print statement (after having removed loop invariants, constant folding, and removing the now empty loop). The program took a long time to compiler, but it ran VERY fast. So, here is my vote for benchmark programs which are not prone to huge improvements through global optimization.