From fe22fd2db8cc6f66ee5021ae4095aa55b1cc80ed Mon Sep 17 00:00:00 2001
From: Ross Thompson <stephen.thompson.37@us.af.mil>
Date: Tue, 1 Jun 2021 13:46:21 -0500
Subject: [PATCH] added clock gater to floating point divider to speed up
 simulation time.

---
 wally-pipelined/src/fpu/fpu.sv            |  9 ++++-
 wally-pipelined/src/generic/clockgater.sv | 46 +++++++++++++++++++++++
 2 files changed, 54 insertions(+), 1 deletion(-)
 create mode 100644 wally-pipelined/src/generic/clockgater.sv

diff --git a/wally-pipelined/src/fpu/fpu.sv b/wally-pipelined/src/fpu/fpu.sv
index c876b313..8362dbe3 100755
--- a/wally-pipelined/src/fpu/fpu.sv
+++ b/wally-pipelined/src/fpu/fpu.sv
@@ -275,7 +275,14 @@ module fpu (
   fma1 fma1 (.*);
 
   //first and only instance of floating-point divider
-  fpdiv fpdivsqrt (.DivOpType(FOpCtrlE[0]), .*);
+  logic fpdivClk;
+  
+  clockgater fpdivclkg(.E(FDivStartE),
+		       .SE(DivBusyM),
+		       .CLK(clk),
+		       .ECLK(fpdivClk));
+  
+  fpdiv fpdivsqrt (.DivOpType(FOpCtrlE[0]), .clk(fpdivClk));
 
   //first of two-stage instance of floating-point add/cvt unit
   fpuaddcvt1 fpadd1 (.*);
diff --git a/wally-pipelined/src/generic/clockgater.sv b/wally-pipelined/src/generic/clockgater.sv
new file mode 100644
index 00000000..dc51829d
--- /dev/null
+++ b/wally-pipelined/src/generic/clockgater.sv
@@ -0,0 +1,46 @@
+///////////////////////////////////////////
+// clockgater.sv
+//
+// Written: Ross Thompson 9 January 2021
+// Modified: 
+//
+// Purpose: Clock gater model. Must use standard cell for synthesis.
+// 
+// A component of the Wally configurable RISC-V project.
+// 
+// Copyright (C) 2021 Harvey Mudd College & Oklahoma State University
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation
+// files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, 
+// modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software 
+// is furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES 
+// OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS 
+// BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT 
+// OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+///////////////////////////////////////////
+
+`include "wally-config.vh"
+
+module clockgater
+  (input logic 	E,
+   input logic 	SE,
+   input logic 	CLK,
+   output logic ECLK);
+
+  // VERY IMPORTANT.
+  // This part functionally models a clock gater, but does not necessarily meet the timing constrains a real standard cell would.
+  // Do not use this in synthesis!
+
+  logic 	enable_q;
+  
+
+  always @(E or SE) begin
+    enable_q <= E | SE;
+  end
+  assign ECLK = enable_q & CLK;
+
+endmodule