target/s390x: Improve cc computation for SUBTRACT LOGICAL

The resulting cc is only dependent on the result and the carry-out.
Carry-out and borrow-out are inverses, so are trivially converted.
With tcg ops, it is easier to compute borrow-out than carry-out, so
save result and borrow-out rather than the inputs.

Borrow-out for 64-bit inputs is had via tcg_gen_sub2_i64 directly
into cc_src.  Borrow-out for 32-bit inputs is had via extraction
from a normal 64-bit sub (with zero-extended inputs).

Reviewed-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20201214221356.68039-4-richard.henderson@linaro.org>
Signed-off-by: Cornelia Huck <cohuck@redhat.com>

1 files changed, 8 insertions, 32 deletions

diff --git a/target/s390x/cc_helper.c b/target/s390x/cc_helper.c
index cd2c5c4b39..c7728d1225 100644
--- a/target/s390x/cc_helper.c
+++ b/target/s390x/cc_helper.c
@@ -129,6 +129,11 @@ static uint32_t cc_calc_addu(uint64_t carry_out, uint64_t result)
     return (result != 0) + 2 * carry_out;
 }
 
+static uint32_t cc_calc_subu(uint64_t borrow_out, uint64_t result)
+{
+    return cc_calc_addu(borrow_out + 1, result);
+}
+
 static uint32_t cc_calc_add_64(int64_t a1, int64_t a2, int64_t ar)
 {
     if ((a1 > 0 && a2 > 0 && ar < 0) || (a1 < 0 && a2 < 0 && ar > 0)) {
@@ -159,19 +164,6 @@ static uint32_t cc_calc_sub_64(int64_t a1, int64_t a2, int64_t ar)
     }
 }
 
-static uint32_t cc_calc_subu_64(uint64_t a1, uint64_t a2, uint64_t ar)
-{
-    if (ar == 0) {
-        return 2;
-    } else {
-        if (a2 > a1) {
-            return 1;
-        } else {
-            return 3;
-        }
-    }
-}
-
 static uint32_t cc_calc_subb_64(uint64_t a1, uint64_t a2, uint64_t ar)
 {
     int borrow_out;
@@ -245,19 +237,6 @@ static uint32_t cc_calc_sub_32(int32_t a1, int32_t a2, int32_t ar)
     }
 }
 
-static uint32_t cc_calc_subu_32(uint32_t a1, uint32_t a2, uint32_t ar)
-{
-    if (ar == 0) {
-        return 2;
-    } else {
-        if (a2 > a1) {
-            return 1;
-        } else {
-            return 3;
-        }
-    }
-}
-
 static uint32_t cc_calc_subb_32(uint32_t a1, uint32_t a2, uint32_t ar)
 {
     int borrow_out;
@@ -462,15 +441,15 @@ static uint32_t do_calc_cc(CPUS390XState *env, uint32_t cc_op,
     case CC_OP_ADDU:
         r = cc_calc_addu(src, dst);
         break;
+    case CC_OP_SUBU:
+        r = cc_calc_subu(src, dst);
+        break;
     case CC_OP_ADD_64:
         r =  cc_calc_add_64(src, dst, vr);
         break;
     case CC_OP_SUB_64:
         r =  cc_calc_sub_64(src, dst, vr);
         break;
-    case CC_OP_SUBU_64:
-        r =  cc_calc_subu_64(src, dst, vr);
-        break;
     case CC_OP_SUBB_64:
         r =  cc_calc_subb_64(src, dst, vr);
         break;
@@ -493,9 +472,6 @@ static uint32_t do_calc_cc(CPUS390XState *env, uint32_t cc_op,
     case CC_OP_SUB_32:
         r =  cc_calc_sub_32(src, dst, vr);
         break;
-    case CC_OP_SUBU_32:
-        r =  cc_calc_subu_32(src, dst, vr);
-        break;
     case CC_OP_SUBB_32:
         r =  cc_calc_subb_32(src, dst, vr);
         break;