It would be easy to have an "auto" clobber list option. The inline assembler would note which registers were touched (mostly trivial, a few instructions have implicit destinations) and would add them all to the clobber list. In about 99% of cases this would be sufficient. I am not aware of any code that conditionally uses a register _and_ conditionally preserves it.

So, 1% of assembly code would use the manual clobber list, but the other 99% would be guaranteed (barring bugs in the compiler) to not have this bug. It seems like the right tradeoff.

Or, instead of an "auto" clobber list the compiler could have a warning if a register is used without being in the clobber list. The programmer could silence that warning in the rare cases where they need to optimize register preservation, and the bugs would be greatly reduced.