How to insure range check elimination optimization is occurring

Question

I'm wondering if there is a way to tell whether or not the optimizer is employing the range check elimination optimization on a particular loop. Although I'd rather not, I can generate the assembly code via -XX:+PrintOptoAssembly, but I'm not exactly sure what I'm looking for. Any help is greatly appreciated.
I'm also wondering if the range check optimization only occurs for arrays, or if it is used when the object being accessed is a List for example, although once I have an answer to my first question, I can investigate this on my own.
Thanks!

Answer 1

I suspect it's left deliberately unspecified to allow flexibility among versions and platforms, and even within a given run on a given JVM. However, everything I've read strongly suggests that [url http://java.sun.com/developer/technicalArticles/Interviews/devinsight_1/]writing dumb code, such as your basic, standard array loop, will enable that optimization to be performed (as hotspot is specifically tuned to common idioms):
for (int i = 0; i < arr.length; i++) {
  // do stuff that does change the value of i or arr
}Alternatively, using a foreach loop should be expected to generate this kind of code.
As for the bottleneck, is what you're doing in one loop iteration so small that it's reasonable to expect that that operation, plus incrementing i will not dwarf the array bounds comparison? Or have you been able to determine that the check itself is the bottleneck?