s390x/tcg: Fix VECTOR SUBTRACT WITH BORROW COMPUTE BORROW INDICATION

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>
Message-Id: <20191021085715.3797-7-david@redhat.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Cornelia Huck <cohuck@redhat.com>

diff --git a/target/s390x/translate_vx.inc.c b/target/s390x/translate_vx.inc.c
index fd746ba35fb61f16c6127979ea48ccbdf330eb02..71059f9ca0a0cc162bb1184c5e68cb86209e576b 100644 (file)
--- 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)