-O0 doesn't necessarily change this. After all, optimizations aren't allowed to violate the spec (if they do, they're buggy). So any code that can be output by

-O0 doesn't necessarily change this. After all, optimizations aren't allowed to violate the spec (if they do, they're buggy). So any code that can be output by an optimizing compiler could (in principle) be output by a non-optimizing compiler.