[Cryptech-Commits] [core/math/modexp] 02/03: Adding iteration flag to be used to remove zero fill of s_mem.

[git at cryptech.is]

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

commit 1e676b4c463e6a5e75a4d81578b139a51059a601
Author: Joachim Strömbergson <joachim at secworks.se>
Date:   Thu Jun 18 12:44:46 2015 +0200

    Adding iteration flag to be used to remove zero fill of s_mem.
---
 src/rtl/montprod.v | 55 +++++++++++++++++++++++++++++-------------------------
 1 file changed, 30 insertions(+), 25 deletions(-)

diff --git a/src/rtl/montprod.v b/src/rtl/montprod.v
index 465bd70..cd7d5a9 100644
--- a/src/rtl/montprod.v
+++ b/src/rtl/montprod.v
@@ -142,10 +142,9 @@ module montprod(
   reg          shr_carry_in_reg;
   reg          shr_carry_in_new;
 
-  reg          reset_word_index_lsw;
-  reg          reset_word_index_msw;
-
-  reg [31 : 0] sa_adder_data_in;
+  reg first_iteration_reg;
+  reg first_iteration_new;
+  reg first_iteration_we;
 
 
   //----------------------------------------------------------------
@@ -161,6 +160,11 @@ module montprod(
   wire          shr_carry_out;
   wire [31 : 0] shr_data_out;
 
+  reg          reset_word_index_lsw;
+  reg          reset_word_index_msw;
+
+  reg [31 : 0] sa_adder_data_in;
+
 
 
   //----------------------------------------------------------------
@@ -226,7 +230,7 @@ module montprod(
     begin : reg_update
       if (!reset_n)
         begin
-          ready_reg           <= 1'b0;
+          ready_reg           <= 1'b1;
           loop_ctr_reg        <= 13'h0;
           word_index_reg      <= 8'h0;
           word_index_prev_reg <= 8'h0;
@@ -239,6 +243,7 @@ module montprod(
           s_mem_we_reg        <= 1'b0;
           s_mem_wr_addr_reg   <= 8'h0;
           b_bit_index_reg     <= 5'h0;
+          first_iteration_reg <= 1'b0;
           montprod_ctrl_reg   <= CTRL_IDLE;
         end
       else
@@ -254,6 +259,9 @@ module montprod(
           add_carry_in_sa_reg <= add_carry_in_sa_new;
           add_carry_in_sm_reg <= add_carry_in_sm_new;
 
+          if (first_iteration_we)
+            first_iteration_reg <= first_iteration_new;
+
           if (b_bit_index_we)
             b_bit_index_reg <= b_bit_index_new;
 
@@ -445,21 +453,19 @@ module montprod(
   //----------------------------------------------------------------
   always @*
     begin : montprod_ctrl
-      ready_new         = 1'b0;
-      ready_we          = 1'b0;
-      montprod_ctrl_new = CTRL_IDLE;
-      montprod_ctrl_we  = 1'b0;
-
-      loop_ctr_set      = 1'b0;
-      loop_ctr_dec      = 1'b0;
-      b_bit_index_we    = 1'b0;
-      bq_we             = 1'b0;
-
-      s_mux_new        = SMUX_0;
-
+      ready_new            = 1'b0;
+      ready_we             = 1'b0;
+      loop_ctr_set         = 1'b0;
+      loop_ctr_dec         = 1'b0;
+      b_bit_index_we       = 1'b0;
+      bq_we                = 1'b0;
+      s_mux_new            = SMUX_0;
       reset_word_index_lsw = 1'b0;
       reset_word_index_msw = 1'b0;
-
+      first_iteration_new  = 1'b0;
+      first_iteration_we   = 1'b0;
+      montprod_ctrl_new    = CTRL_IDLE;
+      montprod_ctrl_we     = 1'b0;
 
       case (montprod_ctrl_reg)
         CTRL_IDLE:
@@ -468,14 +474,11 @@ module montprod(
               begin
                 ready_new = 1'b0;
                 ready_we  = 1'b1;
-                montprod_ctrl_new = CTRL_INIT_S;
-                montprod_ctrl_we = 1'b1;
                 reset_word_index_lsw = 1'b1;
-              end
-            else
-              begin
-                ready_new = 1'b1;
-                ready_we  = 1'b1;
+                first_iteration_new  = 1'b1;
+                first_iteration_we   = 1'b1;
+                montprod_ctrl_new    = CTRL_INIT_S;
+                montprod_ctrl_we     = 1'b1;
               end
           end
 
@@ -529,6 +532,8 @@ module montprod(
 
         CTRL_L_STALLPIPE_SA:
           begin
+            first_iteration_new  = 1'b0;
+            first_iteration_we   = 1'b1;
             montprod_ctrl_new    = CTRL_L_CALC_SDIV2;
             montprod_ctrl_we     = 1'b1;
             reset_word_index_msw = 1'b1;