From f86489b59e82c4ae4e39b6ba0caf9fd279d4aa16 Mon Sep 17 00:00:00 2001
From: Megan Wachs <megan@sifive.com>
Date: Tue, 31 Oct 2017 15:33:41 -0700
Subject: [PATCH] JTAG: Use sorted map for stability (#1073)

* JTAG: Use sorted map for stability

Otherwise the generated FIRRTL/Verilog is non deterministic

* jtag : parens for clarity

* jtag: Use deterministic ListMap and sort for stability

* JTAG: use slightly clearer SortedMap (clearer to me anyway)

* jtag: whitespace cleanup
---
 src/main/scala/devices/debug/DebugTransport.scala | 3 ++-
 src/main/scala/jtag/JtagTap.scala                 | 9 +++++++--
 2 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/src/main/scala/devices/debug/DebugTransport.scala b/src/main/scala/devices/debug/DebugTransport.scala
index 7a5dd8d2..e7e2363e 100644
--- a/src/main/scala/devices/debug/DebugTransport.scala
+++ b/src/main/scala/devices/debug/DebugTransport.scala
@@ -243,7 +243,8 @@ class DebugTransportModuleJTAG(debugAddrBits: Int, c: JtagDTMConfig)
   idcode.mfrId      := io.jtag_mfr_id
 
   val tapIO = JtagTapGenerator(irLength = 5,
-    instructions = Map(dtmJTAGAddrs.DMI_ACCESS -> dmiAccessChain,
+    instructions = Map(
+      dtmJTAGAddrs.DMI_ACCESS -> dmiAccessChain,
       dtmJTAGAddrs.DTM_INFO   -> dtmInfoChain),
     icode = Some(dtmJTAGAddrs.IDCODE)
   )
diff --git a/src/main/scala/jtag/JtagTap.scala b/src/main/scala/jtag/JtagTap.scala
index 44a55ef1..c935cd30 100644
--- a/src/main/scala/jtag/JtagTap.scala
+++ b/src/main/scala/jtag/JtagTap.scala
@@ -2,6 +2,8 @@
 
 package freechips.rocketchip.jtag
 
+import scala.collection.SortedMap
+
 import chisel3._
 import chisel3.util._
 import freechips.rocketchip.config.Parameters
@@ -203,9 +205,12 @@ object JtagTapGenerator {
     bypassChain.io.chainIn := controllerInternal.io.dataChainOut  // for simplicity, doesn't visibly affect anything else
     require(allInstructions.size > 0, "Seriously? JTAG TAP with no instructions?")
 
-    val chainToIcode = allInstructions groupBy { case (icode, chain) => chain } map {
+    // Need to ensure that this mapping is ordered to produce deterministic verilog,
+    // and neither Map nor groupBy are deterministic.
+    // Therefore, we first sort by IDCODE, then sort the groups by the first IDCODE in each group.
+    val chainToIcode = (SortedMap(allInstructions.toList:_*).groupBy { case (icode, chain) => chain } map {
       case (chain, icodeToChain) => chain -> icodeToChain.keys
-    }
+    }).toList.sortBy(_._2.head)
 
     val chainToSelect = chainToIcode map {
       case (chain, icodes) => {