[PATCH v1 4/6] s390x/tcg: Fix VECTOR SUBTRACT COMPUTE BORROW INDICATION

[David Hildenbrand]

Looks like my idea of what a "borrow" is was wrong. We are dealing with
unsigned numbers. A subtraction is simply an addition with the bitwise
complement. If we get a carry during the addition, that's the borrow.
"The operands are treated as unsigned binary integers."

This is nice, as we can reuse the VECTOR ADD COMPUTE CARRY functions
and avoid helpers, all we have to do is compute the bitwise complement.

Fixes: 1ee2d7ba72f6 ("s390x/tcg: Implement VECTOR SUBTRACT COMPUTE BORROW 
INDICATION")
Signed-off-by: David Hildenbrand <address@hidden>
---
 target/s390x/helper.h           |  2 --
 target/s390x/translate_vx.inc.c | 45 ++++++++++++++++++++++++---------
 target/s390x/vec_int_helper.c   | 16 ------------
 3 files changed, 33 insertions(+), 30 deletions(-)

diff --git a/target/s390x/helper.h b/target/s390x/helper.h
index 56e8149866..ca1e08100a 100644
--- a/target/s390x/helper.h
+++ b/target/s390x/helper.h
@@ -207,8 +207,6 @@ DEF_HELPER_FLAGS_4(gvec_verim16, TCG_CALL_NO_RWG, void, 
ptr, cptr, cptr, i32)
 DEF_HELPER_FLAGS_4(gvec_vsl, TCG_CALL_NO_RWG, void, ptr, cptr, i64, i32)
 DEF_HELPER_FLAGS_4(gvec_vsra, TCG_CALL_NO_RWG, void, ptr, cptr, i64, i32)
 DEF_HELPER_FLAGS_4(gvec_vsrl, TCG_CALL_NO_RWG, void, ptr, cptr, i64, i32)
-DEF_HELPER_FLAGS_4(gvec_vscbi8, TCG_CALL_NO_RWG, void, ptr, cptr, cptr, i32)
-DEF_HELPER_FLAGS_4(gvec_vscbi16, TCG_CALL_NO_RWG, void, ptr, cptr, cptr, i32)
 DEF_HELPER_4(gvec_vtm, void, ptr, cptr, env, i32)
 
 /* === Vector String Instructions === */
diff --git a/target/s390x/translate_vx.inc.c b/target/s390x/translate_vx.inc.c
index 5ce7bfb0af..40bcc1604e 100644
--- a/target/s390x/translate_vx.inc.c
+++ b/target/s390x/translate_vx.inc.c
@@ -2130,14 +2130,40 @@ static DisasJumpType op_vs(DisasContext *s, DisasOps *o)
     return DISAS_NEXT;
 }
 
+static void gen_scbi8_i64(TCGv_i64 d, TCGv_i64 a, TCGv_i64 b)
+{
+    TCGv_i64 t = tcg_temp_new_i64();
+
+    tcg_gen_not_i64(t, b);
+    gen_acc(d, a, t, ES_8);
+    tcg_temp_free_i64(t);
+}
+
+static void gen_scbi16_i64(TCGv_i64 d, TCGv_i64 a, TCGv_i64 b)
+{
+    TCGv_i64 t = tcg_temp_new_i64();
+
+    tcg_gen_not_i64(t, b);
+    gen_acc(d, a, t, ES_16);
+    tcg_temp_free_i64(t);
+}
+
 static void gen_scbi_i32(TCGv_i32 d, TCGv_i32 a, TCGv_i32 b)
 {
-    tcg_gen_setcond_i32(TCG_COND_LTU, d, a, b);
+    TCGv_i32 t = tcg_temp_new_i32();
+
+    tcg_gen_not_i32(t, b);
+    gen_acc_i32(d, a, t);
+    tcg_temp_free_i32(t);
 }
 
 static void gen_scbi_i64(TCGv_i64 d, TCGv_i64 a, TCGv_i64 b)
 {
-    tcg_gen_setcond_i64(TCG_COND_LTU, d, a, b);
+    TCGv_i64 t = tcg_temp_new_i64();
+
+    tcg_gen_not_i64(t, b);
+    gen_acc_i64(d, a, t);
+    tcg_temp_free_i64(t);
 }
 
 static void gen_scbi2_i64(TCGv_i64 dl, TCGv_i64 dh, TCGv_i64 al,
@@ -2145,26 +2171,21 @@ static void gen_scbi2_i64(TCGv_i64 dl, TCGv_i64 dh, 
TCGv_i64 al,
 {
     TCGv_i64 th = tcg_temp_new_i64();
     TCGv_i64 tl = tcg_temp_new_i64();
-    TCGv_i64 zero = tcg_const_i64(0);
 
-    tcg_gen_sub2_i64(tl, th, al, zero, 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_acc2_i64(dl, dh, al, ah, tl, th);
 
     tcg_temp_free_i64(th);
     tcg_temp_free_i64(tl);
-    tcg_temp_free_i64(zero);
 }
 
 static DisasJumpType op_vscbi(DisasContext *s, DisasOps *o)
 {
     const uint8_t es = get_field(s->fields, m4);
     static const GVecGen3 g[4] = {
-        { .fno = gen_helper_gvec_vscbi8, },
-        { .fno = gen_helper_gvec_vscbi16, },
+        { .fni8 = gen_scbi8_i64, },
+        { .fni8 = gen_scbi16_i64, },
         { .fni4 = gen_scbi_i32, },
         { .fni8 = gen_scbi_i64, },
     };
diff --git a/target/s390x/vec_int_helper.c b/target/s390x/vec_int_helper.c
index d38405848f..e8fe7af496 100644
--- a/target/s390x/vec_int_helper.c
+++ b/target/s390x/vec_int_helper.c
@@ -583,22 +583,6 @@ void HELPER(gvec_vsrl)(void *v1, const void *v2, uint64_t 
count,
     s390_vec_shr(v1, v2, count);
 }
 
-#define DEF_VSCBI(BITS)                                                        
\
-void HELPER(gvec_vscbi##BITS)(void *v1, const void *v2, const void *v3,        
\
-                              uint32_t desc)                                   
\
-{                                                                              
\
-    int i;                                                                     
\
-                                                                               
\
-    for (i = 0; i < (128 / BITS); i++) {                                       
\
-        const uint##BITS##_t a = s390_vec_read_element##BITS(v2, i);           
\
-        const uint##BITS##_t b = s390_vec_read_element##BITS(v3, i);           
\
-                                                                               
\
-        s390_vec_write_element##BITS(v1, i, a < b);                            
\
-    }                                                                          
\
-}
-DEF_VSCBI(8)
-DEF_VSCBI(16)
-
 void HELPER(gvec_vtm)(void *v1, const void *v2, CPUS390XState *env,
                       uint32_t desc)
 {
-- 
2.21.0