From a1ebe6da4d16d77db173bcd76afa0f326c3dc7ed Mon Sep 17 00:00:00 2001
From: Andrew Waterman <andrew@sifive.com>
Date: Thu, 7 Dec 2017 18:56:06 -0800
Subject: [PATCH] Prevent frontend deadlock fetching from uncacheable memory

After detecting a corrupted BTB, don't speculatively update it until
the next non-speculative fetch.  This prevents the frontend from replaying
forever.
---
 src/main/scala/rocket/Frontend.scala | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/main/scala/rocket/Frontend.scala b/src/main/scala/rocket/Frontend.scala
index 85ecbb46..6321fe9e 100644
--- a/src/main/scala/rocket/Frontend.scala
+++ b/src/main/scala/rocket/Frontend.scala
@@ -207,6 +207,7 @@ class FrontendModule(outer: Frontend) extends LazyModuleImp(outer)
         // a branch! Flush the BTB and the pipeline.
         btb.io.flush := true
         fq.io.enq.bits.replay := true
+        wrong_path := true
       }
 
       when (!prevTaken) {