Re: [PATCH v5] target/loongarch: fix vldi/xvldi raise wrong error

[Philippe Mathieu-Daudé]

On 4/6/25 10:40, Song Gao wrote:

on qemu we got an aborted error
**
ERROR:../target/loongarch/tcg/insn_trans/trans_vec.c.inc:3574:vldi_get_value: 
code should not be reached
Bail out! 
ERROR:../target/loongarch/tcg/insn_trans/trans_vec.c.inc:3574:vldi_get_value: 
code should not be reached
Aborted (core dumped)
but on 3A600/3A5000 we got a "Illegal instruction" error.

Resolves: https://gitlab.com/qemu-project/qemu/-/issues/2971

Fixes: 29bb5d727ff ("target/loongarch: Implement vldi")
Signed-off-by: Song Gao <gaos...@loongson.cn>
---
  target/loongarch/tcg/insn_trans/trans_vec.c.inc | 12 ++++++++++--
  1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/target/loongarch/tcg/insn_trans/trans_vec.c.inc 
b/target/loongarch/tcg/insn_trans/trans_vec.c.inc
index dff92772ad..9d82d162a9 100644
--- a/target/loongarch/tcg/insn_trans/trans_vec.c.inc
+++ b/target/loongarch/tcg/insn_trans/trans_vec.c.inc
@@ -3465,7 +3465,7 @@ TRANS(xvmsknz_b, LASX, gen_xx, gen_helper_vmsknz_b)
  static uint64_t vldi_get_value(DisasContext *ctx, uint32_t imm)
  {
      int mode;
-    uint64_t data, t;
+    uint64_t data = 0, t;

/*

       * imm bit [11:8] is mode, mode value is 0-12.
@@ -3570,17 +3570,25 @@ static uint64_t vldi_get_value(DisasContext *ctx, 
uint32_t imm)
          }
          break;
      default:
-        generate_exception(ctx, EXCCODE_INE);
          g_assert_not_reached();
      }
      return data;
  }

+static bool check_vldi_mode(arg_vldi *a)

+{
+   return (a->imm >>8 & 0xf) <= 12;

Preferably (as easier to review):

      return extract32(a->imm, 8, 4) <= 12;

Otherwise patch LGTM :)

+}
  static bool gen_vldi(DisasContext *ctx, arg_vldi *a, uint32_t oprsz)
  {
      int sel, vece;
      uint64_t value;

+ if (!check_vldi_mode(a)){

+        generate_exception(ctx, EXCCODE_INE);
+        return true;
+    }
+
      if (!check_vec(ctx, oprsz)) {
          return true;
      }