From b3d3f82d4e38f2712d5ccf9c69051137ec5fca76 Mon Sep 17 00:00:00 2001
From: Andrew Waterman <waterman@eecs.berkeley.edu>
Date: Wed, 1 Aug 2012 22:55:02 -0700
Subject: [PATCH] new tohost/fromhost semantics

---
 riscv/insns/mtpcr.h | 3 ++-
 riscv/processor.cc  | 2 --
 2 files changed, 2 insertions(+), 3 deletions(-)

diff --git a/riscv/insns/mtpcr.h b/riscv/insns/mtpcr.h
index 5cd0134..9b0beba 100644
--- a/riscv/insns/mtpcr.h
+++ b/riscv/insns/mtpcr.h
@@ -1,4 +1,5 @@
 require_supervisor;
 reg_t val = get_pcr(insn.rtype.rs1);
-set_pcr(insn.rtype.rs1, RS2);
+if (val == 0 || insn.rtype.rs1 != PCR_TOHOST)
+  set_pcr(insn.rtype.rs1, RS2);
 RD = val;
diff --git a/riscv/processor.cc b/riscv/processor.cc
index c116575..070ec15 100644
--- a/riscv/processor.cc
+++ b/riscv/processor.cc
@@ -271,12 +271,10 @@ void processor_t::set_pcr(int which, reg_t val)
       vecbanks_count = __builtin_popcountll(vecbanks);
       break;
     case PCR_TOHOST:
-      fromhost = 0;
       tohost = val;
       break;
     case PCR_FROMHOST:
       fromhost = val;
-      tohost = 0;
       break;
   }
 }
-- 
2.30.2