This conflict was introduced by 53aacff7c when compressed support was
added. Previously, doDecode could be scheduled in the same cycle as
doFetch3 (and only in that order), but the Reg reads added to doDecode
prevented this. Instead, use EHRs to allow a bypass path from doDecode
to doFetch3. This means we can issue every cycle again, rather than only
every other cycle.
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