From ed586cfa46902ad2577aeb2c409dc2cc295c395d Mon Sep 17 00:00:00 2001
From: Fredrik Noring <noring@nocrew.org>
Date: Fri, 23 Nov 2018 18:39:35 -0500
Subject: [PATCH] target/mips: Guard check_insn with INSN_R5900 check

Explicitely mark handling of PREF instruction for R5900 as
treating the same as NOP.

Backports commit 992e8176d36882983bb04f0259f7151a36d003a1 from qemu
---
 qemu/target/mips/translate.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/qemu/target/mips/translate.c b/qemu/target/mips/translate.c
index 6cb2f881..0a80e526 100644
--- a/qemu/target/mips/translate.c
+++ b/qemu/target/mips/translate.c
@@ -28550,9 +28550,12 @@ static void decode_opc(CPUMIPSState *env, DisasContext *ctx, bool *insn_need_pat
         break;
     case OPC_PREF:
         check_insn_opc_removed(ctx, ISA_MIPS32R6);
-        check_insn(ctx, ISA_MIPS4 | ISA_MIPS32 |
-                   INSN_R5900);
-        /* Treat as NOP. */
+        if (ctx->insn_flags & INSN_R5900) {
+            /* Treat as NOP. */
+        } else {
+            check_insn(ctx, ISA_MIPS4 | ISA_MIPS32);
+            /* Treat as NOP. */
+        }
         break;
 
     /* Floating point (COP1). */