According to the Zvfbfa ISA spec (v0.1), improperly NaN-boxed
f-register operands must substitute the BF16 canonical NaN instead of
the FP16 canonical NaN for some vector floating-point instructions.

Signed-off-by: Max Chou <max.chou@sifive.com>
---
 target/riscv/insn_trans/trans_rvv.c.inc | 18 +++++++++---------
 target/riscv/translate.c                |  8 ++++++++
 2 files changed, 17 insertions(+), 9 deletions(-)

diff --git a/target/riscv/insn_trans/trans_rvv.c.inc b/target/riscv/insn_trans/trans_rvv.c.inc
index 71f98fb350b..62cc03784cb 100644
--- a/target/riscv/insn_trans/trans_rvv.c.inc
+++ b/target/riscv/insn_trans/trans_rvv.c.inc
@@ -2347,17 +2347,17 @@ GEN_OPIWI_NARROW_TRANS(vnclip_wi, IMM_ZX, vnclip_wx)
  */
 static void do_nanbox(DisasContext *s, TCGv_i64 out, TCGv_i64 in)
 {
-    switch (s->sew) {
-    case 1:
-        gen_check_nanbox_h(out, in);
-        break;
-    case 2:
+    if (s->sew == MO_16) {
+        if (s->altfmt) {
+            gen_check_nanbox_h_bf16(out, in);
+        } else {
+            gen_check_nanbox_h(out, in);
+        }
+    } else if (s->sew == MO_32) {
         gen_check_nanbox_s(out, in);
-        break;
-    case 3:
+    } else if (s->sew == MO_64) {
         tcg_gen_mov_i64(out, in);
-        break;
-    default:
+    } else {
         g_assert_not_reached();
     }
 }
diff --git a/target/riscv/translate.c b/target/riscv/translate.c
index 8ad147946c9..d99b58629d0 100644
--- a/target/riscv/translate.c
+++ b/target/riscv/translate.c
@@ -201,6 +201,14 @@ static void gen_check_nanbox_h(TCGv_i64 out, TCGv_i64 in)
     tcg_gen_movcond_i64(TCG_COND_GEU, out, in, t_max, in, t_nan);
 }
 
+static void gen_check_nanbox_h_bf16(TCGv_i64 out, TCGv_i64 in)
+{
+    TCGv_i64 t_max = tcg_constant_i64(0xffffffffffff0000ull);
+    TCGv_i64 t_nan = tcg_constant_i64(0xffffffffffff7fc0ull);
+
+    tcg_gen_movcond_i64(TCG_COND_GEU, out, in, t_max, in, t_nan);
+}
+
 static void gen_check_nanbox_s(TCGv_i64 out, TCGv_i64 in)
 {
     TCGv_i64 t_max = tcg_constant_i64(0xffffffff00000000ull);
-- 
2.43.0