From fe690528f7c3b8b2002e5d97081690d7cddbeac9 Mon Sep 17 00:00:00 2001
From: Dolu1990 <charles.papon.90@gmail.com>
Date: Tue, 16 Feb 2021 14:16:57 +0100
Subject: [PATCH] MulPlugin.outputBuffer feature added

---
 .../scala/vexriscv/plugin/MulPlugin.scala     | 46 +++++++++++++++----
 .../vexriscv/TestIndividualFeatures.scala     | 33 +++++++------
 2 files changed, 56 insertions(+), 23 deletions(-)

diff --git a/src/main/scala/vexriscv/plugin/MulPlugin.scala b/src/main/scala/vexriscv/plugin/MulPlugin.scala
index 31714e8..c1619d2 100644
--- a/src/main/scala/vexriscv/plugin/MulPlugin.scala
+++ b/src/main/scala/vexriscv/plugin/MulPlugin.scala
@@ -5,7 +5,8 @@ import spinal.core._
 import spinal.lib.KeepAttribute
 
 //Input buffer generaly avoid the FPGA synthesis to duplicate reg inside the DSP cell, which could stress timings quite much.
-class MulPlugin(inputBuffer : Boolean = false) extends Plugin[VexRiscv]{
+class MulPlugin(var inputBuffer : Boolean = false,
+                var outputBuffer : Boolean = false) extends Plugin[VexRiscv]{
   object MUL_LL extends Stageable(UInt(32 bits))
   object MUL_LH extends Stageable(SInt(34 bits))
   object MUL_HL extends Stageable(SInt(34 bits))
@@ -53,16 +54,26 @@ class MulPlugin(inputBuffer : Boolean = false) extends Plugin[VexRiscv]{
 //      a := input(SRC1)
 //      b := input(SRC2)
 
+      val delay = (if(inputBuffer) 1 else 0) + (if(outputBuffer) 1 else 0)
+
+      val delayLogic = (delay != 0) generate new Area{
+        val counter = Reg(UInt(log2Up(delay+1) bits))
+        when(arbitration.isValid && input(IS_MUL) && counter =/= delay){
+          arbitration.haltItself := True
+        }
+        when(!arbitration.isStuckByOthers){
+          counter := counter + 1
+        }
+        when(!arbitration.isStuck){
+          counter := 0
+        }
+      }
+
       val withInputBuffer = inputBuffer generate new Area{
         val rs1 = RegNext(input(RS1))
         val rs2 = RegNext(input(RS2))
         a := rs1
         b := rs2
-
-        val delay = RegNext(arbitration.isStuck)
-        when(arbitration.isValid && input(IS_MUL) && !delay){
-          arbitration.haltItself := True
-        }
       }
 
       val noInputBuffer = (!inputBuffer) generate new Area{
@@ -91,10 +102,25 @@ class MulPlugin(inputBuffer : Boolean = false) extends Plugin[VexRiscv]{
       val bSLow = (False ## b(15 downto 0)).asSInt
       val aHigh = (((aSigned && a.msb) ## a(31 downto 16))).asSInt
       val bHigh = (((bSigned && b.msb) ## b(31 downto 16))).asSInt
-      insert(MUL_LL) := aULow * bULow
-      insert(MUL_LH) := aSLow * bHigh
-      insert(MUL_HL) := aHigh * bSLow
-      insert(MUL_HH) := aHigh * bHigh
+
+      val withOuputBuffer = outputBuffer generate new Area{
+        val mul_ll = RegNext(aULow * bULow)
+        val mul_lh = RegNext(aSLow * bHigh)
+        val mul_hl = RegNext(aHigh * bSLow)
+        val mul_hh = RegNext(aHigh * bHigh)
+
+        insert(MUL_LL) := mul_ll
+        insert(MUL_LH) := mul_lh
+        insert(MUL_HL) := mul_hl
+        insert(MUL_HH) := mul_hh
+      }
+
+      val noOutputBuffer = (!outputBuffer) generate new Area{
+        insert(MUL_LL) := aULow * bULow
+        insert(MUL_LH) := aSLow * bHigh
+        insert(MUL_HL) := aHigh * bSLow
+        insert(MUL_HH) := aHigh * bHigh
+      }
 
       Component.current.afterElaboration{
         //Avoid synthesis tools to retime RS1 RS2 from execute stage to decode stage leading to bad timings (ex : Vivado, even if retiming is disabled)
diff --git a/src/test/scala/vexriscv/TestIndividualFeatures.scala b/src/test/scala/vexriscv/TestIndividualFeatures.scala
index 0cf5ce6..429ad3e 100644
--- a/src/test/scala/vexriscv/TestIndividualFeatures.scala
+++ b/src/test/scala/vexriscv/TestIndividualFeatures.scala
@@ -173,19 +173,26 @@ class MulDivDimension extends VexRiscvDimension("MulDiv") {
     } :: l
 
 
-    if(!noMemory && !noWriteBack) l =
-      new VexRiscvPosition("MulDivFpga") {
-        override def testParam = "MUL=yes DIV=yes"
-        override def applyOn(config: VexRiscvConfig): Unit = {
-          config.plugins += new MulPlugin
-          config.plugins += new MulDivIterativePlugin(
-            genMul = false,
-            genDiv = true,
-            mulUnrollFactor = 32,
-            divUnrollFactor = 1
-          )
-        }
-      } :: l
+    if(!noMemory && !noWriteBack) {
+      val inputBuffer = r.nextBoolean()
+      val outputBuffer = r.nextBoolean()
+      l = new VexRiscvPosition(s"MulDivFpga$inputBuffer$outputBuffer") {
+          override def testParam = "MUL=yes DIV=yes"
+
+          override def applyOn(config: VexRiscvConfig): Unit = {
+            config.plugins += new MulPlugin(
+              inputBuffer = inputBuffer,
+              outputBuffer = outputBuffer
+            )
+            config.plugins += new MulDivIterativePlugin(
+              genMul = false,
+              genDiv = true,
+              mulUnrollFactor = 32,
+              divUnrollFactor = 1
+            )
+          }
+        } :: l
+    }
 
     random(r, l)
   }