fix known bugs

1 files changed, 26 insertions, 1 deletions

diff --git a/rv64cpu/rtl/core/id_ex_reg.sv b/rv64cpu/rtl/core/id_ex_reg.sv
index 7c780ee..e88ce17 100644
--- a/rv64cpu/rtl/core/id_ex_reg.sv
+++ b/rv64cpu/rtl/core/id_ex_reg.sv
@@ -113,7 +113,7 @@ module id_ex_reg
 );
 
     always_ff @(posedge clk) begin
-        if (rst || flush_en) begin
+        if (rst) begin
             ex_pc            <= '0;
             ex_rs1_rdata     <= '0;
             ex_rs2_rdata     <= '0;
@@ -144,6 +144,31 @@ module id_ex_reg
             ex_is_sfence_vma <= '0;
             ex_is_fence      <= '0;
             ex_is_fence_i    <= '0;
+        end else if (flush_en) begin
+            ex_alu_op        <= ALU_ADD; // NOP is effectively ADD x0, x0, 0
+            ex_alu_src1_sel  <= '0;
+            ex_alu_src2_sel  <= '0;
+            ex_is_word_op    <= '0;
+            ex_is_branch     <= '0;
+            ex_branch_op     <= BRANCH_EQ;
+            ex_is_jump       <= '0;
+            ex_is_load       <= '0;
+            ex_is_store      <= '0;
+            ex_mem_size      <= '0;
+            ex_reg_write_en  <= '0; // VERY IMPORTANT: Do not write to regfile on NOP
+            ex_rd_addr       <= '0;
+            ex_wb_sel        <= '0;
+            ex_is_csr        <= '0;
+            ex_csr_op        <= '0;
+            ex_illegal_instr <= '0;
+            ex_is_ecall      <= '0;
+            ex_is_ebreak     <= '0;
+            ex_is_mret       <= '0;
+            ex_is_sret       <= '0;
+            ex_is_wfi        <= '0;
+            ex_is_sfence_vma <= '0;
+            ex_is_fence      <= '0;
+            ex_is_fence_i    <= '0;
         end else if (~stall_en) begin
             ex_pc            <= id_pc;
             ex_rs1_rdata     <= id_rs1_rdata;