Compiler intermittently fails with INTERNAL ERROR: optimizer experienced a segmentation fault

Compile at -o1 or less; the pass with the bug runs only at -o2 or greater. In this particular case, making m_register_address a regular field instead of a bitfield will also avoid the issue. There isn't a simple change to the source that might avoid it in the general case; avoidance requires that several aspects that combine for the error, don't combine.

If a struct contains a bitfield, and a function contains both a read and a write of that bitfield, and the expression written includes an operation (such as '&' with a constant) that truncates the value in the same way that the bitfield write does, then the optimiser may crash due to a bad memory access. The important detail is the write to the bitfield. Note that field writes in C++ don't look struct accesses, but are. Also note that the compiler can inline calls and rearrange code to create the problematic situation in ways that are not obvious.