target/nios2: Fix BRET instruction

We had failed to copy BSTATUS back to STATUS, and diagnose
supervisor-only.  The spec is light on the specifics of the
implementation of bret, but it is an easy assumption that
the restore into STATUS should work the same as eret.

Therefore, reuse the existing helper_eret.

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Reported-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20220421151735.31996-19-richard.henderson@linaro.org>

diff --git a/target/nios2/translate.c b/target/nios2/translate.c
index 53699ee0882399d8cb8e66375713d49dfbd41b2b..3694f2503b14d7cde06fe7fcb6d879c50dfbf8f1 100644 (file)
--- a/target/nios2/translate.c
+++ b/target/nios2/translate.c
@@ -407,12 +407,22 @@ static void ret(DisasContext *dc, uint32_t code, uint32_t flags)
     dc->base.is_jmp = DISAS_JUMP;
 }
 
-/* PC <- ba */
+/*
+ * status <- bstatus
+ * PC <- ba
+ */
 static void bret(DisasContext *dc, uint32_t code, uint32_t flags)
 {
-    tcg_gen_mov_tl(cpu_pc, cpu_R[R_BA]);
+    if (!gen_check_supervisor(dc)) {
+        return;
+    }
 
-    dc->base.is_jmp = DISAS_JUMP;
+#ifdef CONFIG_USER_ONLY
+    g_assert_not_reached();
+#else
+    gen_helper_eret(cpu_env, cpu_R[CR_BSTATUS], cpu_R[R_BA]);
+    dc->base.is_jmp = DISAS_NORETURN;
+#endif
 }
 
 /* PC <- rA */