[Cryptech-Commits] [core/math/modexp] 04/05: Collapsing cycles for loop counter. Updating testbench to match removed cycles.

[git at cryptech.is]

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joachim at secworks.se pushed a commit to branch perfopt
in repository core/math/modexp.

commit aa58db8cf671c6abcbc8d918bac4345d2f22d809
Author: Joachim Strömbergson <joachim at secworks.se>
Date:   Tue Jun 16 15:57:14 2015 +0200

    Collapsing cycles for loop counter. Updating testbench to match removed cycles.
---
 src/rtl/montprod.v   | 76 ++++++++++++++++++++++++++++------------------------
 src/tb/tb_montprod.v |  8 ++----
 2 files changed, 43 insertions(+), 41 deletions(-)

diff --git a/src/rtl/montprod.v b/src/rtl/montprod.v
index 7102e6e..927356f 100644
--- a/src/rtl/montprod.v
+++ b/src/rtl/montprod.v
@@ -121,6 +121,8 @@ module montprod(
   reg [12 : 0] loop_counter_reg;
   reg [12 : 0] loop_counter_new;
   reg          loop_counter_we;
+  reg          loop_counter_set;
+  reg          loop_counter_dec;
 
   reg [07 : 0] B_word_index; //loop counter as a word index
   reg [04 : 0] B_bit_index; //loop counter as a bit index
@@ -155,6 +157,8 @@ module montprod(
   wire          shr_carry_out;
   wire [31 : 0] shr_adiv2;
 
+  reg           in_iter;
+
 
   //----------------------------------------------------------------
   // Concurrent connectivity for ports etc.
@@ -310,43 +314,39 @@ module montprod(
 
 
   //----------------------------------------------------------------
-  // loop_counter_logic
-  // Logic for the loop counter and setting related B indices.
+  // Process for iterating the loop counter and setting related B indexes
   //----------------------------------------------------------------
   always @*
-    begin : loop_counter_logic
-
-      loop_counter_new = 13'h000;
-      loop_counter_we  = 1'b0;
+   begin : loop_counter_process
+     loop_counter_new = loop_counter_reg;
+     loop_counter_we  = 1'b0;
+     length_m1        = length - 1'b1;
+     B_bit_index      = B_bit_index_reg;
 
-      length_m1        = length - 1'b1;
-      B_word_index     = loop_counter_reg[12:5];
-      B_bit_index      = B_bit_index_reg;
-
-      case (montprod_ctrl_reg)
-        CTRL_LOOP_INIT:
-          begin
-            loop_counter_new = {length, 5'b00000} - 1'b1;
-            loop_counter_we  = 1'b1;
-          end
+     if (loop_counter_set)
+         begin
+           loop_counter_new = {length, 5'b00000} - 1'b1;
+           loop_counter_we   = 1'b1;
+         end
 
-        CTRL_LOOP_ITER:
-          begin
-            B_word_index = loop_counter_reg[12:5];
-            B_bit_index  = 5'h1f - loop_counter_reg[4:0];
-          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];
+         end
 
-        CTRL_L_STALLPIPE_D2:
-          begin
-            loop_counter_new = loop_counter_reg - 1'b1;
-            loop_counter_we  = 1'b1;
-          end
+       CTRL_L_STALLPIPE_D2:
+         begin
+           loop_counter_new = loop_counter_reg - 1'b1;
+           loop_counter_we  = 1'b1;
+         end
 
-        default:
-          begin
-          end
-      endcase
-    end
+       default:
+         begin
+         end
+     endcase
+   end
 
 
   //----------------------------------------------------------------
@@ -472,6 +472,10 @@ module montprod(
       montprod_ctrl_new = CTRL_IDLE;
       montprod_ctrl_we  = 1'b0;
 
+      loop_counter_set = 1'b0;
+      loop_counter_dec = 1'b0;
+      in_iter          = 1'b0;
+
       reset_word_index_LSW = 1'b0;
       reset_word_index_MSW = 1'b0;
 
@@ -497,14 +501,14 @@ module montprod(
           begin
             if (word_index_reg == 8'h0)
               begin
-                 montprod_ctrl_new = CTRL_LOOP_INIT;
-                 montprod_ctrl_we = 1'b1;
+                montprod_ctrl_new = CTRL_LOOP_INIT;
+                montprod_ctrl_we  = 1'b1;
               end
           end
 
-
         CTRL_LOOP_INIT:
           begin
+            loop_counter_set  = 1'b1;
             montprod_ctrl_new = CTRL_LOOP_ITER;
             montprod_ctrl_we  = 1'b1;
           end
@@ -513,6 +517,7 @@ module montprod(
         // Also abort loop if done.
         CTRL_LOOP_ITER:
           begin
+            in_iter = 1'b1;
             reset_word_index_LSW = 1'b1;
             montprod_ctrl_new    = CTRL_LOOP_BQ;
             montprod_ctrl_we     = 1'b1;
@@ -570,7 +575,8 @@ module montprod(
 
         CTRL_L_STALLPIPE_D2:
           begin
-            montprod_ctrl_new    = CTRL_LOOP_ITER; //loop
+            loop_counter_dec     = 1'b1;
+            montprod_ctrl_new    = CTRL_LOOP_ITER;
             montprod_ctrl_we     = 1'b1;
             reset_word_index_LSW = 1'b1;
 
diff --git a/src/tb/tb_montprod.v b/src/tb/tb_montprod.v
index 2cadd78..bf9333e 100644
--- a/src/tb/tb_montprod.v
+++ b/src/tb/tb_montprod.v
@@ -212,8 +212,8 @@ module tb_montprod();
         begin
           $display("S[ 0 ]: %x", dut.s_mem.mem[0] );
 
-          if (dut.s_mem_we)
-            $display("Write to S[0x%02x]: 0x%08x", dut.s_mem_wr_addr, dut.s_mem_new);
+          if (dut.s_mem_we_reg)
+            $display("Write to S[0x%02x]: 0x%08x", dut.s_mem_wr_addr_reg, dut.s_mem_new);
         end
     end
 
@@ -243,8 +243,6 @@ module tb_montprod();
               $display("FSM: IDLE");
             dut.CTRL_INIT_S:
               $display("FSM: INIT_S");
-            dut.CTRL_LOOP_INIT:
-              $display("FSM: LOOP_INIT");
             dut.CTRL_LOOP_ITER:
               $display("FSM: LOOP_ITER");
             dut.CTRL_LOOP_BQ:
@@ -259,8 +257,6 @@ module tb_montprod();
               $display("FSM: LOOP_CALC_SDIV2");
             dut.CTRL_EMIT_S:
               $display("FSM: LOOP_EMIT_S");
-            dut.CTRL_DONE:
-              $display("FSM: DONE");
             default:
               $display("FSM: %x", dut.montprod_ctrl_new);
           endcase