[riscv-CMOs:master] new issue: encoding of prefetches impose minimum sensible granularity of cache blocks #github #risv #CMOs


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[riscv-CMOs:master] New Issue Created by jnk0le:
#40 encoding of prefetches impose minimum sensible granularity of cache blocks

as of 0.6 draft:

Prefetches are encoded in ori HINT space so the offset[4:0] at bits [11:7] is unusable as rd must always be zero.

offset[11:5] provides only 32 byte granularity. In case of 16 or 8 byte blocks, there will be gaps inaccessible by offset. Redoing S-type to I-type imm allows to take one or more bits for narrowing that gap at the cost of encoding space (the bottom of the offset will be discarded anyway)