Fix remaining sec inconsistency regarding the X-IF addition (#291)

* Changes to make the X_if addition compatible with the golden version of the core, minus the rf_we line

* [rt][sec][xif] Made the length of the cve2_id_stage's rf_wdata_sel dependent on the whether the X-IF is present

* [rtl][sec][xif] Made the length of the cve2_id_stage's rf_wdata_sel dependent on the whether the X-IF is present

Author: cairo-caplan

rtl/cve2_decoder.sv

@@ -51,7 +51,7 @@ module cve2_decoder #(
   output logic [31:0]           zimm_rs1_type_o,
 
   // register file
-  output cve2_pkg::rf_wd_sel_e     rf_wdata_sel_o,   // RF write data selection
+  output logic [XInterface:0]      rf_wdata_sel_o,   // RF write data selection
   output logic                     rf_we_o,          // write enable for regfile
   output logic [4:0]               rf_raddr_a_o,
   output logic [4:0]               rf_raddr_b_o,
@@ -660,7 +660,7 @@ module cve2_decoder #(
     // insufficient privileges), or when accessing non-available registers in RV32E,
     // these cases are not handled here
     if (illegal_insn) begin
-      // rf_we           = 1'b0;
+      rf_we           &= XInterface;
       data_req_o      = 1'b0;
       data_we_o       = 1'b0;
       jump_in_dec_o   = 1'b0;

rtl/cve2_id_stage.sv

@@ -216,10 +216,10 @@ module cve2_id_stage #(
 
   // Register file interface
 
-  rf_wd_sel_e  rf_wdata_sel;
-  logic        rf_we_dec, rf_we_raw;
-  logic        rf_ren_a, rf_ren_b;
-  logic        rf_ren_a_dec, rf_ren_b_dec;
+  logic [XInterface:0] rf_wdata_sel;
+  logic                rf_we_dec, rf_we_raw;
+  logic                rf_ren_a, rf_ren_b;
+  logic                rf_ren_a_dec, rf_ren_b_dec;
 
   // Read enables should only be asserted for valid and legal instructions
   assign rf_ren_a = instr_valid_i & ~instr_fetch_err_i & ~illegal_insn_o & rf_ren_a_dec;
@@ -418,19 +418,12 @@ module cve2_id_stage #(
 
   // Register file write data mux
   always_comb begin : rf_wdata_id_mux
-    if (XInterface)
-      unique case (rf_wdata_sel)
-        RF_WD_EX:     rf_wdata_id_o   = result_ex_i;
-        RF_WD_CSR:    rf_wdata_id_o   = csr_rdata_i;
-        RF_WD_COPROC: rf_wdata_id_o   = x_result_i.data;
-        default:      rf_wdata_id_o   = result_ex_i;
-      endcase
-    else
-      unique case (rf_wdata_sel)
-        RF_WD_EX:     rf_wdata_id_o   = result_ex_i;
-        RF_WD_CSR:    rf_wdata_id_o   = csr_rdata_i;
-        default:      rf_wdata_id_o   = result_ex_i;
-      endcase
+    unique case (rf_wdata_sel)
+      RF_WD_EX:     rf_wdata_id_o   = result_ex_i;
+      RF_WD_CSR:    rf_wdata_id_o   = csr_rdata_i;
+      RF_WD_COPROC: rf_wdata_id_o   = XInterface? x_result_i.data : result_ex_i;
+      default:      rf_wdata_id_o   = result_ex_i;
+    endcase
   end
 
   /////////////
@@ -826,7 +819,7 @@ module cve2_id_stage #(
   // Stall ID/EX stage for reason that relates to instruction in ID/EX, update assertion below if
   // modifying this.
   assign stall_id = stall_mem | stall_multdiv | stall_jump | stall_branch |
-                      stall_alu | stall_coproc;
+                      stall_alu | (XInterface & stall_coproc);
 
   // Generally illegal instructions have no reason to stall, however they must still stall waiting
   // for outstanding memory requests so exceptions related to them take priority over the illegal
@@ -902,10 +895,17 @@ module cve2_id_stage #(
       OP_A_FWD,
       OP_A_CURRPC,
       OP_A_IMM})
-  `ASSERT(IbexRegfileWdataSelValid, instr_valid_i |-> rf_wdata_sel inside {
-      RF_WD_EX,
-      RF_WD_CSR,
-      RF_WD_COPROC})
+  if (XInterface) begin: gen_asserts_xif
+    `ASSERT(IbexRegfileWdataSelValid, instr_valid_i |-> rf_wdata_sel inside {
+        RF_WD_EX,
+        RF_WD_CSR,
+        RF_WD_COPROC})
+  end 
+  else begin : no_gen_asserts_xif
+    `ASSERT(IbexRegfileWdataSelValid, instr_valid_i |-> rf_wdata_sel inside {
+        RF_WD_EX,
+        RF_WD_CSR})
+  end
   `ASSERT_KNOWN(IbexWbStateKnown, id_fsm_q)
 
   // Branch decision must be valid when jumping.

rtl/cve2_pkg.sv

@@ -260,10 +260,10 @@ package cve2_pkg;
   } imm_b_sel_e;
 
   // Regfile write data selection
-  typedef enum logic[1:0] {
+  typedef enum {
     RF_WD_EX,
     RF_WD_CSR,
-    RF_WD_COPROC
+    RF_WD_COPROC // Only used when XInterface = 1
   } rf_wd_sel_e;
 
   //////////////