Fix rvfi_bus_imem_check issue in #44 #46
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When a 32-bit instruction is fetched over the course of two bus accesses, and the first half of the instruction is the halfword-of-interest, the check assumes the fetch of the first halfword doesn't fault. However it still permits faults on the second halfword. When this happens, the core takes a trap and clears the entire instruction reported on rvfi_insn. This does not match the expected halfword-of-interest so fails the check. Fix by also preventing faults on imem_addr + 2 if imem_data is the first half of a 32-bit instruction. Note that imem_data can always be assumed to be the first half of an instruction as the assertions only fire when pc is equal to imem_addr.
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When a 32-bit instruction is fetched over the course of two bus accesses, and the first half of the instruction is the halfword-of-interest, the check assumes the fetch of the first halfword doesn't fault. However it still permits faults on the second halfword. When this happens, the core takes a trap and clears the entire instruction reported on rvfi_insn. This does not match the expected halfword-of-interest so fails the check.
Fix by also preventing faults on imem_addr + 2 if imem_data is the first half of a 32-bit instruction. Note that imem_data can always be assumed to be the first half of an instruction as the assertions only fire when pc is equal to imem_addr.
The
bus_imemcheck fails on Hazard3 without this change, and passes with it (depth=12). See discussion on #44