The numbers are unsigned, the computation is wrong. "Each operand is
treated as an unsigned binary integer".
Let's implement as given in the PoP:

"A subtraction is performed by adding the contents of the second operand
 with the bitwise complement of the third operand along with a borrow
 indication from the rightmost bit of the fourth operand."

Reuse gen_accc2_i64().

Fixes: bc725e65152c ("s390x/tcg: Implement VECTOR SUBTRACT WITH BORROW COMPUTE BORROW INDICATION")
Signed-off-by: David Hildenbrand <david@redhat.com>
---
 target/s390x/translate_vx.inc.c | 13 +++----------
 1 file changed, 3 insertions(+), 10 deletions(-)

diff --git a/target/s390x/translate_vx.inc.c b/target/s390x/translate_vx.inc.c
index fd746ba35f..71059f9ca0 100644
--- a/target/s390x/translate_vx.inc.c
+++ b/target/s390x/translate_vx.inc.c
@@ -2214,20 +2214,13 @@ static void gen_sbcbi2_i64(TCGv_i64 dl, TCGv_i64 dh, TCGv_i64 al, TCGv_i64 ah,
 {
     TCGv_i64 th = tcg_temp_new_i64();
     TCGv_i64 tl = tcg_temp_new_i64();
-    TCGv_i64 zero = tcg_const_i64(0);
 
-    tcg_gen_andi_i64(tl, cl, 1);
-    tcg_gen_sub2_i64(tl, th, al, zero, tl, zero);
-    tcg_gen_sub2_i64(tl, th, tl, th, bl, zero);
-    tcg_gen_andi_i64(th, th, 1);
-    tcg_gen_sub2_i64(tl, th, ah, zero, th, zero);
-    tcg_gen_sub2_i64(tl, th, tl, th, bh, zero);
-    tcg_gen_andi_i64(dl, th, 1);
-    tcg_gen_mov_i64(dh, zero);
+    tcg_gen_not_i64(tl, bl);
+    tcg_gen_not_i64(th, bh);
+    gen_accc2_i64(dl, dh, al, ah, tl, th, cl, ch);
 
     tcg_temp_free_i64(tl);
     tcg_temp_free_i64(th);
-    tcg_temp_free_i64(zero);
 }
 
 static DisasJumpType op_vsbcbi(DisasContext *s, DisasOps *o)
-- 
2.21.0

On 10/21/19 1:57 AM, David Hildenbrand wrote:
> The numbers are unsigned, the computation is wrong. "Each operand is
> treated as an unsigned binary integer".
> Let's implement as given in the PoP:
> 
> "A subtraction is performed by adding the contents of the second operand
>  with the bitwise complement of the third operand along with a borrow
>  indication from the rightmost bit of the fourth operand."
> 
> Reuse gen_accc2_i64().
> 
> Fixes: bc725e65152c ("s390x/tcg: Implement VECTOR SUBTRACT WITH BORROW COMPUTE BORROW INDICATION")
> Signed-off-by: David Hildenbrand <david@redhat.com>
> ---
>  target/s390x/translate_vx.inc.c | 13 +++----------
>  1 file changed, 3 insertions(+), 10 deletions(-)

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>


r~