Using an atomic write or read-write insn on ROM is basically
a happens-never case. Handle it via stop-the-world, which
will generate non-atomic serial code, where we can correctly
ignore the write while producing the correct read result.
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
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