The difference here is not so much in where you guess the bug is, as in whether you do the experiment.

A very effective experiment is to take your program and chop out everything irrelevant until you have a short piece of code which demonstrates the bug. At this point, if it is a compiler bug, you have dense information to hand the compiler author; if it isn't a compiler bug, you're in a much better position to understand what's wrong with your code.

However, one is often reluctant to apply this technique until one suspects a compiler bug, because it seems like a lot of work. And it is — but often less work than continuing to examine the bug with less radical tools, given that you're in the position where the notion of compiler bugs crosses your mind.