Merge of s_mux and s_write to allow cycle collapsing.

1 files changed, 49 insertions, 61 deletions

diff --git a/src/rtl/montprod.v b/src/rtl/montprod.v
index 927356f..06eca12 100644
--- a/src/rtl/montprod.v
+++ b/src/rtl/montprod.v
@@ -67,7 +67,7 @@ module montprod(
 
   localparam CTRL_IDLE           = 4'h0;
   localparam CTRL_INIT_S         = 4'h1;
-  localparam CTRL_LOOP_INIT      = 4'h2;
+  localparam CTRL_WAIT           = 4'h2;
   localparam CTRL_LOOP_ITER      = 4'h3;
   localparam CTRL_LOOP_BQ        = 4'h4;
   localparam CTRL_L_CALC_SM      = 4'h5;
@@ -157,7 +157,7 @@ module montprod(
   wire          shr_carry_out;
   wire [31 : 0] shr_adiv2;
 
-  reg           in_iter;
+  reg           set_B_bit_index;
 
 
   //----------------------------------------------------------------
@@ -271,27 +271,6 @@ module montprod(
 
 
   //----------------------------------------------------------------
-  // s_mux
-  //----------------------------------------------------------------
-  always @*
-    begin : s_mux
-      case (s_mux_reg)
-        SMUX_0:
-          s_mem_new = 32'b0;
-        SMUX_ADD_SA:
-          s_mem_new = add_result_sa;
-        SMUX_ADD_SM:
-          s_mem_new = add_result_sm;
-        SMUX_SHR:
-          s_mem_new = shr_adiv2;
-      endcase
-
-      if (DEBUG)
-        $display("S-MUX %x: %x", s_mux_reg, s_mem_new);
-    end
-
-
-  //----------------------------------------------------------------
   // bq
   //----------------------------------------------------------------
   always @*
@@ -314,7 +293,9 @@ module montprod(
 
 
   //----------------------------------------------------------------
-  // Process for iterating the loop counter and setting related B indexes
+  // loop_counter_process
+  // Process for iterating the loop counter and  setting
+  // related B indices.
   //----------------------------------------------------------------
   always @*
    begin : loop_counter_process
@@ -322,30 +303,24 @@ module montprod(
      loop_counter_we  = 1'b0;
      length_m1        = length - 1'b1;
      B_bit_index      = B_bit_index_reg;
+     B_word_index     = loop_counter_reg[12:5];
 
      if (loop_counter_set)
          begin
            loop_counter_new = {length, 5'b00000} - 1'b1;
-           loop_counter_we   = 1'b1;
-         end
-
-     case (montprod_ctrl_reg)
-       CTRL_LOOP_ITER:
-         begin
-           B_word_index = loop_counter_reg[12:5];
-           B_bit_index  = 5'h1f - loop_counter_reg[4:0];
+           loop_counter_we  = 1'b1;
          end
 
-       CTRL_L_STALLPIPE_D2:
-         begin
+     if (loop_counter_dec)
+       begin
            loop_counter_new = loop_counter_reg - 1'b1;
            loop_counter_we  = 1'b1;
-         end
+       end
 
-       default:
-         begin
-         end
-     endcase
+     if (set_B_bit_index)
+       begin
+           B_bit_index  = 5'h1f - loop_counter_reg[4:0];
+       end
    end
 
 
@@ -354,6 +329,11 @@ module montprod(
   //----------------------------------------------------------------
   always @*
     begin : prodcalc
+      opb_addr_reg = B_word_index;
+      opm_addr_reg = word_index_reg;
+
+      result_addr_reg  = word_index_prev_reg;
+      result_data_reg  = s_mem_read_data;
 
       case (montprod_ctrl_reg)
         CTRL_LOOP_ITER:
@@ -364,9 +344,6 @@ module montprod(
           opa_addr_reg = word_index_reg;
        endcase
 
-       opb_addr_reg = B_word_index;
-       opm_addr_reg = word_index_reg;
-
       case (montprod_ctrl_reg)
         CTRL_LOOP_ITER:
           s_mem_addr = length_m1;
@@ -374,11 +351,6 @@ module montprod(
           s_mem_addr = word_index_reg;
       endcase
 
-
-      result_addr_reg  = word_index_prev_reg;
-      result_data_reg  = s_mem_read_data;
-
-
       case (montprod_ctrl_reg)
         CTRL_EMIT_S:
            tmp_result_we = 1'b1;
@@ -389,23 +361,26 @@ module montprod(
 
       if (reset_word_index_LSW == 1'b1)
         word_index_new = length_m1;
+
       else if (reset_word_index_MSW == 1'b1)
         word_index_new = 8'h0;
+
       else if (montprod_ctrl_reg == CTRL_L_CALC_SDIV2)
         word_index_new = word_index_reg + 1'b1;
+
       else
         word_index_new = word_index_reg - 1'b1;
     end // prodcalc
 
 
   //----------------------------------------------------------------
-  // s_writer
+  // s_select_write
   //----------------------------------------------------------------
   always @*
-    begin : s_writer
-      shr_carry_in_new    = 1'b0;
-      s_mux_new     = SMUX_0;
-      s_mem_we_new  = 1'b0;
+    begin : s_select_write
+      shr_carry_in_new = 1'b0;
+      s_mux_new        = SMUX_0;
+      s_mem_we_new     = 1'b0;
 
       case (montprod_ctrl_reg)
         CTRL_INIT_S:
@@ -440,18 +415,31 @@ module montprod(
           end
       endcase
 
+      s_mem_new           = 32'h0;
       add_carry_in_sa_new = 1'b0;
       add_carry_in_sm_new = 1'b0;
 
       case (s_mux_reg)
-        SMUX_ADD_SM:
-          add_carry_in_sm_new = add_carry_out_sm;
+        SMUX_0:
+          s_mem_new = 32'h0;
 
         SMUX_ADD_SA:
-          add_carry_in_sa_new = add_carry_out_sa;
+          begin
+            s_mem_new           = add_result_sa;
+            add_carry_in_sa_new = add_carry_out_sa;
+          end
+
+        SMUX_ADD_SM:
+          begin
+            s_mem_new           = add_result_sm;
+            add_carry_in_sm_new = add_carry_out_sm;
+          end
 
         SMUX_SHR:
-          shr_carry_in_new = shr_carry_out;
+          begin
+            s_mem_new        = shr_adiv2;
+            shr_carry_in_new = shr_carry_out;
+          end
 
         default:
           begin
@@ -474,7 +462,7 @@ module montprod(
 
       loop_counter_set = 1'b0;
       loop_counter_dec = 1'b0;
-      in_iter          = 1'b0;
+      set_B_bit_index  = 1'b0;
 
       reset_word_index_LSW = 1'b0;
       reset_word_index_MSW = 1'b0;
@@ -501,14 +489,14 @@ module montprod(
           begin
             if (word_index_reg == 8'h0)
               begin
-                montprod_ctrl_new = CTRL_LOOP_INIT;
+                loop_counter_set  = 1'b1;
+                montprod_ctrl_new = CTRL_WAIT;
                 montprod_ctrl_we  = 1'b1;
               end
           end
 
-        CTRL_LOOP_INIT:
+        CTRL_WAIT:
           begin
-            loop_counter_set  = 1'b1;
             montprod_ctrl_new = CTRL_LOOP_ITER;
             montprod_ctrl_we  = 1'b1;
           end
@@ -517,7 +505,7 @@ module montprod(
         // Also abort loop if done.
         CTRL_LOOP_ITER:
           begin
-            in_iter = 1'b1;
+            set_B_bit_index      = 1'b1;
             reset_word_index_LSW = 1'b1;
             montprod_ctrl_new    = CTRL_LOOP_BQ;
             montprod_ctrl_we     = 1'b1;