[Qemu-devel] [PATCH v1 35/41] s390x/tcg: Implement VECTOR SUBTRACT COMPUTE BORROW INDICATION

[David Hildenbrand]

Let's keep it simple for now and handle 8/16/128 bit elements via helpers.
Especially for 8/16, we could come up with some bit tricks.

Signed-off-by: David Hildenbrand <address@hidden>
---
 target/s390x/helper.h           |  3 +++
 target/s390x/insn-data.def      |  2 ++
 target/s390x/translate_vx.inc.c | 30 +++++++++++++++++++++
 target/s390x/vec_int_helper.c   | 47 +++++++++++++++++++++++++++++++++
 4 files changed, 82 insertions(+)

diff --git a/target/s390x/helper.h b/target/s390x/helper.h
index af7fb10f76..33e3e003f8 100644
--- a/target/s390x/helper.h
+++ b/target/s390x/helper.h
@@ -230,6 +230,9 @@ DEF_HELPER_FLAGS_4(gvec_vsl, TCG_CALL_NO_RWG, void, ptr, 
cptr, i64, i32)
 DEF_HELPER_FLAGS_4(gvec_vsldb, TCG_CALL_NO_RWG, void, ptr, cptr, cptr, 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_FLAGS_4(gvec_vscbi128, TCG_CALL_NO_RWG, void, ptr, cptr, cptr, i32)
 
 #ifndef CONFIG_USER_ONLY
 DEF_HELPER_3(servc, i32, env, i64, i64)
diff --git a/target/s390x/insn-data.def b/target/s390x/insn-data.def
index 58a61f41ef..94de3c9c7d 100644
--- a/target/s390x/insn-data.def
+++ b/target/s390x/insn-data.def
@@ -1176,6 +1176,8 @@
     F(0xe77d, VSRLB,   VRR_c, V,   0, 0, 0, 0, vsrl, 0, IF_VEC)
 /* VECTOR SUBTRACT */
     F(0xe7f7, VS,      VRR_c, V,   0, 0, 0, 0, vs, 0, IF_VEC)
+/* VECTOR SUBTRACT COMPUTE BORROW INDICATION */
+    F(0xe7f5, VSCBI,   VRR_c, V,   0, 0, 0, 0, vscbi, 0, IF_VEC)
 
 #ifndef CONFIG_USER_ONLY
 /* COMPARE AND SWAP AND PURGE */
diff --git a/target/s390x/translate_vx.inc.c b/target/s390x/translate_vx.inc.c
index 83463155f6..7770ca4101 100644
--- a/target/s390x/translate_vx.inc.c
+++ b/target/s390x/translate_vx.inc.c
@@ -2155,3 +2155,33 @@ static DisasJumpType op_vs(DisasContext *s, DisasOps *o)
                   get_field(s->fields, v3));
     return DISAS_NEXT;
 }
+
+static void gen_scbi_i32(TCGv_i32 d, TCGv_i32 a, TCGv_i32 b)
+{
+    tcg_gen_setcond_i32(TCG_COND_LTU, d, a, b);
+}
+
+static void gen_scbi_i64(TCGv_i64 d, TCGv_i64 a, TCGv_i64 b)
+{
+    tcg_gen_setcond_i64(TCG_COND_LTU, d, a, b);
+}
+
+static DisasJumpType op_vscbi(DisasContext *s, DisasOps *o)
+{
+    const uint8_t es = get_field(s->fields, m4);
+    static const GVecGen3 g[5] = {
+        { .fno = gen_helper_gvec_vscbi8, },
+        { .fno = gen_helper_gvec_vscbi16, },
+        { .fni4 = gen_scbi_i32, },
+        { .fni8 = gen_scbi_i64, },
+        { .fno = gen_helper_gvec_vscbi128, },
+    };
+
+    if (es > ES_128) {
+        gen_program_exception(s, PGM_SPECIFICATION);
+        return DISAS_NORETURN;
+    }
+    gen_gvec_3(get_field(s->fields, v1), get_field(s->fields, v2),
+               get_field(s->fields, v3), &g[es]);
+    return DISAS_NEXT;
+}
diff --git a/target/s390x/vec_int_helper.c b/target/s390x/vec_int_helper.c
index 12502b48e8..699b399a26 100644
--- a/target/s390x/vec_int_helper.c
+++ b/target/s390x/vec_int_helper.c
@@ -38,6 +38,27 @@ static bool s390_vec_add(S390Vector *d, const S390Vector *a,
     return high_carry;
 }
 
+/*
+ * Subtract two 128 bit vectors, returning the borrow.
+ */
+static bool s390_vec_sub(S390Vector *d, const S390Vector *a,
+                         const S390Vector *b)
+{
+    bool low_borrow = false, high_borrow = false;
+
+    if (a->doubleword[0] < b->doubleword[0]) {
+        high_borrow = true;
+    } else if (a->doubleword[1] < b->doubleword[0]) {
+        low_borrow = true;
+        if (a->doubleword[0] == b->doubleword[0]) {
+            high_borrow = true;
+        }
+    }
+    d->doubleword[0] = a->doubleword[0] - b->doubleword[0] - low_borrow;
+    d->doubleword[1] = a->doubleword[1] - b->doubleword[1];
+    return high_borrow;
+}
+
 static bool s390_vec_is_zero(const S390Vector *v)
 {
     return !v->doubleword[0] && !v->doubleword[1];
@@ -756,3 +777,29 @@ 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_vscbi128)(void *v1, const void *v2, const void *v3,
+                           uint32_t desc)
+{
+    S390Vector *dst = v1;
+    S390Vector tmp;
+
+    dst->doubleword[0] = 0;
+    dst->doubleword[1] = s390_vec_sub(&tmp, v2, v3);
+}
-- 
2.20.1