[Cryptech-Commits] [core/math/modexp] 01/01: Fused the s_mem init loop into the adder loop.

[git at cryptech.is]

This is an automated email from the git hooks/post-receive script.

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

commit d5115d8547df48e33af778eadc7cdaa07fddeb7e
Author: Joachim Strömbergson <joachim at secworks.se>
Date:   Wed Jun 24 19:47:45 2015 +0200

    Fused the s_mem init loop into the adder loop.
---
 src/rtl/montprod.v   | 49 ++++++++++++++-----------------------------------
 src/tb/tb_montprod.v |  2 --
 2 files changed, 14 insertions(+), 37 deletions(-)

diff --git a/src/rtl/montprod.v b/src/rtl/montprod.v
index ccf8341..189bb18 100644
--- a/src/rtl/montprod.v
+++ b/src/rtl/montprod.v
@@ -68,16 +68,14 @@ module montprod #(parameter OPW = 32, parameter ADW = 8)
   // Internal constant and parameter definitions.
   //----------------------------------------------------------------
   localparam CTRL_IDLE            = 4'h0;
-  localparam CTRL_INIT_S          = 4'h1;
-  localparam CTRL_WAIT            = 4'h2;
-  localparam CTRL_LOOP_ITER       = 4'h3;
-  localparam CTRL_LOOP_BQ         = 4'h4;
-  localparam CTRL_CALC_ADD        = 4'h5;
-  localparam CTRL_STALLPIPE_ADD   = 4'h6;
-  localparam CTRL_CALC_SDIV2      = 4'h7;
-  localparam CTRL_STALLPIPE_SDIV2 = 4'h8;
-  localparam CTRL_L_STALLPIPE_ES  = 4'h9;
-  localparam CTRL_EMIT_S          = 4'ha;
+  localparam CTRL_LOOP_ITER       = 4'h1;
+  localparam CTRL_LOOP_BQ         = 4'h2;
+  localparam CTRL_CALC_ADD        = 4'h3;
+  localparam CTRL_STALLPIPE_ADD   = 4'h4;
+  localparam CTRL_CALC_SDIV2      = 4'h5;
+  localparam CTRL_STALLPIPE_SDIV2 = 4'h6;
+  localparam CTRL_L_STALLPIPE_ES  = 4'h7;
+  localparam CTRL_EMIT_S          = 4'h8;
 
   localparam SMUX_ZERO            = 2'h0;
   localparam SMUX_ITER            = 2'h1;
@@ -317,11 +315,6 @@ module montprod #(parameter OPW = 32, parameter ADW = 8)
       s_mem_we              = 1'b0;
 
       case (montprod_ctrl_reg)
-        CTRL_INIT_S:
-          begin
-            s_mem_we_new = 1'b1;
-          end
-
         CTRL_LOOP_ITER:
           begin
             s_mem_read_addr = length_m1;
@@ -409,7 +402,11 @@ module montprod #(parameter OPW = 32, parameter ADW = 8)
   always @*
    begin : bq
      b_new = opb_data[b_bit_index_reg];
-     q_new = s_mem_read_data[0] ^ (opa_data[0] & b_new);
+
+     if (first_iteration_reg)
+       q_new = 1'b0 ^ (opa_data[0] & b_new);
+     else
+       q_new = s_mem_read_data[0] ^ (opa_data[0] & b_new);
 
      b_bit_index_new = (2**(13 - ADW) - 1) - loop_ctr_reg[(13 - ADW - 1) : 0];
      b_word_index    = loop_ctr_reg[12 : (13 - ADW)];
@@ -513,29 +510,11 @@ module montprod #(parameter OPW = 32, parameter ADW = 8)
                 ready_we             = 1'b1;
                 reset_word_index_lsw = 1'b1;
                 loop_ctr_set         = 1'b1;
-                montprod_ctrl_new    = CTRL_INIT_S;
+                montprod_ctrl_new    = CTRL_LOOP_ITER;
                 montprod_ctrl_we     = 1'b1;
               end
           end
 
-        CTRL_INIT_S:
-          begin
-            s_mux_new      = SMUX_ZERO;
-            dec_word_index = 1'b1;
-
-            if (word_index_reg == 0)
-              begin
-                montprod_ctrl_new = CTRL_WAIT;
-                montprod_ctrl_we  = 1'b1;
-              end
-          end
-
-        CTRL_WAIT:
-          begin
-            montprod_ctrl_new = CTRL_LOOP_ITER;
-            montprod_ctrl_we  = 1'b1;
-          end
-
         //calculate q = (s - b * A) & 1;.
         // Also abort loop if done.
         CTRL_LOOP_ITER:
diff --git a/src/tb/tb_montprod.v b/src/tb/tb_montprod.v
index c98e8a2..cd27949 100644
--- a/src/tb/tb_montprod.v
+++ b/src/tb/tb_montprod.v
@@ -241,8 +241,6 @@ module tb_montprod();
           case (dut.montprod_ctrl_new)
             dut.CTRL_IDLE:
               $display("FSM: IDLE");
-            dut.CTRL_INIT_S:
-              $display("FSM: INIT_S");
             dut.CTRL_LOOP_ITER:
               $display("FSM: LOOP_ITER");
             dut.CTRL_LOOP_BQ: