[XIF] Forwarding of data from WB with X_EXT=1 is not working.

Placeholder github Source User
2022-08-25T13:31:21Z

Forwarding of results from the X-interface is currently not taken care of. Turning on X_EXT=1 will make several design assertions fail due to this.

The jalr forward path currently uses ex_wb_pipe.rf_wdata for forwarding of any ALU/MUL/DIV/CSR read data to the ID stage. If we want to enable forwarding from the XIF, this code must be adapted. Forwarding from XIF to the jump address logic may lead to bad timing though.

For operand_a and operand_b, the forwarding logic seems wrong in at least one scenario: When the XIF signals an exception, rf_we_wb is suppressed which fans into the bypass logic, and the ID stage is not killed (as it should be).