I did once have a bizarre situation where removing a bounds check that always succeeded degraded performance by over 30%. The bounds check wasn't being elided

I did once have a bizarre situation where removing a bounds check that always succeeded degraded performance by over 30%. The bounds check wasn't being elided either. I checked and it was there in the assembly, so I figured that the function is so hot that an unchecked access might help things. Apparently not. The only thing I can think of is that the reduction in code-size for that function had an unintended effect elsewhere, either for the optimizer or that it resulted in a hot bit of code crossing a cache line?