But for the most use you'd specifcially want them used for optimizations when they are NOT being evaluated as that's the build where perf matters.

...yup, looks like there's no way to get the optimisation benefit in "ignore" mode, which is the only mode that doesn't explicitly compile the runtime checks: https://godbolt.org/z/KTx1Pc3aa compare codegen for test3 (the pattern that would be useful) vs test4 (the best we actually have)