Fix AXI_ADDR_BIT_OFFSET and AXIL_ADDR_BIT_OFFSET part select

[AlexLao512]

I think I fixed this correctly, the tests in your repo seem to pass.

[AlexLao512]

I misunderstood some stuff. Let me work on this a bit. I think there are some reasonable workarounds that are a bit annoying but seeing #28 I think they are worth doing.

I think we can get away with slightly more confusing code but avoid duplicating a lot of code with generate blocks.

For code paths we know are going to compile out, we use a different parameter or ternary operators to force the values to something the simulator is happy with.

I'll restrict this MR to axi_axil_adapter since that is what I have my testbenches for at the moment.

[AlexLao512]

I have something working, I forced pushed over the commit. Sorry for the confusion earlier.

@alexforencich. Do you mind checking? I don't know if I am running your cocotb stuff properly. Quick sanity check in my much smaller testbenches shows they compile fine and functionality looks OK but my testbenches are not very complete since I just use them for testing SystemVerilog wrappers around many of your modules.

[alexforencich]

Terribly ugly macros. I liked one of the other suggestions better that added an intermediate var, but IMO the proper solution is to fix the simulator so it doesn't throw an error if the code is unreachable by parameter value.

[AlexLao512]

I'll see if I can bypass the error or create intermediate parameters.

[AlexLao512]

@alexforencich I think I've found a more reasonable workaround. ModelSim seems happy with [A -: B] relative part selects even when they end up backwards. If you are ok with this change, I can make the same changes to the other adapters with similar issues.

[PedroAntunes178]

Hi, related to this issue, xcelium gives the following error:

xmelab: *E,RNGDIR (../src/axi_axil_adapter_rd.v,286|61): Reversed part-select index expression ordering.
                  s_axi_rdata_next = m_axil_rdata >> (addr_reg[AXIL_ADDR_BIT_OFFSET-1:AXI_ADDR_BIT_OFFSET] * AXI_DATA_WIDTH);

And Verilator gives a similar error.