Scott Hanselman has a blog post that shows a few examples of what /optimize (which is enabled in Release Builds) does.
As a summary: /optimize does many things with no exact number or definition given, but one of the more visible are method inlining (If you have a Method A() which calls B() which calls C() which calls D(), the compiler may "skip" B and C and go from A to D directly), which may cause a "weird" callstack in the Release build.
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…