The decode of FMOV (vector, immediate, half-precision) vs
invalid cases of MOVI are incorrect.

Fixes RISU mismatch for invalid insn 0x2f01fd31.

Fixes: 70b4e6a4457 ("arm/translate-a64: add FP16 FMOV to simd_mod_imm")
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 target/arm/tcg/translate-a64.c | 24 ++++++++++++++----------
 1 file changed, 14 insertions(+), 10 deletions(-)

diff --git a/target/arm/tcg/translate-a64.c b/target/arm/tcg/translate-a64.c
index d97acdbaf9..5455ae3685 100644
--- a/target/arm/tcg/translate-a64.c
+++ b/target/arm/tcg/translate-a64.c
@@ -7904,27 +7904,31 @@ static void disas_simd_mod_imm(DisasContext *s, uint32_t insn)
     bool is_q = extract32(insn, 30, 1);
     uint64_t imm = 0;
 
-    if (o2 != 0 || ((cmode == 0xf) && is_neg && !is_q)) {
-        /* Check for FMOV (vector, immediate) - half-precision */
-        if (!(dc_isar_feature(aa64_fp16, s) && o2 && cmode == 0xf)) {
+    if (o2) {
+        if (cmode != 0xf || is_neg) {
             unallocated_encoding(s);
             return;
         }
-    }
-
-    if (!fp_access_check(s)) {
-        return;
-    }
-
-    if (cmode == 15 && o2 && !is_neg) {
         /* FMOV (vector, immediate) - half-precision */
+        if (!dc_isar_feature(aa64_fp16, s)) {
+            unallocated_encoding(s);
+            return;
+        }
         imm = vfp_expand_imm(MO_16, abcdefgh);
         /* now duplicate across the lanes */
         imm = dup_const(MO_16, imm);
     } else {
+        if (cmode == 0xf && is_neg && !is_q) {
+            unallocated_encoding(s);
+            return;
+        }
         imm = asimd_imm_const(abcdefgh, cmode, is_neg);
     }
 
+    if (!fp_access_check(s)) {
+        return;
+    }
+
     if (!((cmode & 0x9) == 0x1 || (cmode & 0xd) == 0x9)) {
         /* MOVI or MVNI, with MVNI negation handled above.  */
         tcg_gen_gvec_dup_imm(MO_64, vec_full_reg_offset(s, rd), is_q ? 16 : 8,
-- 
2.34.1

On Sat, 25 May 2024 at 00:30, Richard Henderson
<richard.henderson@linaro.org> wrote:
>
> The decode of FMOV (vector, immediate, half-precision) vs
> invalid cases of MOVI are incorrect.
>
> Fixes RISU mismatch for invalid insn 0x2f01fd31.
>
> Fixes: 70b4e6a4457 ("arm/translate-a64: add FP16 FMOV to simd_mod_imm")
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>


Reviewed-by: Peter Maydell <peter.maydell@linaro.org>

thanks
-- PMM