target-arm: Implement sbc_cc inline

Use sub2 if available, otherwise use 64-bit arithmetic.

Cc: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>

target-arm/helper.h

@@ -140,8 +140,6 @@ DEF_HELPER_2(recpe_u32, i32, i32, env)
 DEF_HELPER_2(rsqrte_u32, i32, i32, env)
 DEF_HELPER_5(neon_tbl, i32, env, i32, i32, i32, i32)
 
-DEF_HELPER_3(sbc_cc, i32, env, i32, i32)
-
 DEF_HELPER_3(shl_cc, i32, env, i32, i32)
 DEF_HELPER_3(shr_cc, i32, env, i32, i32)
 DEF_HELPER_3(sar_cc, i32, env, i32, i32)

target-arm/op_helper.c

@@ -315,21 +315,6 @@ uint64_t HELPER(get_cp_reg64)(CPUARMState *env, void *rip)
    The only way to do that in TCG is a conditional branch, which clobbers
    all our temporaries.  For now implement these as helper functions.  */
 
-uint32_t HELPER(sbc_cc)(CPUARMState *env, uint32_t a, uint32_t b)
-{
-    uint32_t result;
-    if (!env->CF) {
-        result = a - b - 1;
-        env->CF = a > b;
-    } else {
-        result = a - b;
-        env->CF = a >= b;
-    }
-    env->VF = (a ^ b) & (a ^ result);
-    env->NF = env->ZF = result;
-    return result;
-}
-
 /* Similarly for variable shift instructions.  */
 
 uint32_t HELPER(shl_cc)(CPUARMState *env, uint32_t x, uint32_t i)

target-arm/translate.c

@@ -464,6 +464,35 @@ static void gen_sub_CC(TCGv dest, TCGv t0, TCGv t1)
     tcg_gen_mov_i32(dest, cpu_NF);
 }
 
+/* dest = T0 + ~T1 + CF = T0 - T1 + CF - 1.  Compute C, N, V and Z flags */
+static void gen_sbc_CC(TCGv dest, TCGv t0, TCGv t1)
+{
+    TCGv tmp = tcg_temp_new_i32();
+    tcg_gen_subi_i32(cpu_CF, cpu_CF, 1);
+    if (TCG_TARGET_HAS_add2_i32) {
+        tcg_gen_movi_i32(tmp, 0);
+        tcg_gen_add2_i32(cpu_NF, cpu_CF, t0, tmp, cpu_CF, tmp);
+        tcg_gen_sub2_i32(cpu_NF, cpu_CF, t0, cpu_CF, t1, tmp);
+    } else {
+        TCGv_i64 q0 = tcg_temp_new_i64();
+        TCGv_i64 q1 = tcg_temp_new_i64();
+        tcg_gen_extu_i32_i64(q0, t0);
+        tcg_gen_extu_i32_i64(q1, t1);
+        tcg_gen_sub_i64(q0, q0, q1);
+        tcg_gen_extu_i32_i64(q1, cpu_CF);
+        tcg_gen_add_i64(q0, q0, q1);
+        tcg_gen_extr_i64_i32(cpu_NF, cpu_CF, q0);
+        tcg_temp_free_i64(q0);
+        tcg_temp_free_i64(q1);
+    }
+    tcg_gen_mov_i32(cpu_ZF, cpu_NF);
+    tcg_gen_xor_i32(cpu_VF, cpu_NF, t0);
+    tcg_gen_xor_i32(tmp, t0, t1);
+    tcg_gen_and_i32(cpu_VF, cpu_VF, tmp);
+    tcg_temp_free_i32(tmp);
+    tcg_gen_mov_i32(dest, cpu_NF);
+}
+
 #define GEN_SHIFT(name)                                               \
 static void gen_##name(TCGv dest, TCGv t0, TCGv t1)                   \
 {                                                                     \
@@ -7109,7 +7138,7 @@ static void disas_arm_insn(CPUARMState * env, DisasContext *s)
             break;
         case 0x06:
             if (set_cc) {
-                gen_helper_sbc_cc(tmp, cpu_env, tmp, tmp2);
+                gen_sbc_CC(tmp, tmp, tmp2);
             } else {
                 gen_sub_carry(tmp, tmp, tmp2);
             }
@@ -7117,7 +7146,7 @@ static void disas_arm_insn(CPUARMState * env, DisasContext *s)
             break;
         case 0x07:
             if (set_cc) {
-                gen_helper_sbc_cc(tmp, cpu_env, tmp2, tmp);
+                gen_sbc_CC(tmp, tmp2, tmp);
             } else {
                 gen_sub_carry(tmp, tmp2, tmp);
             }
@@ -7947,10 +7976,11 @@ gen_thumb2_data_op(DisasContext *s, int op, int conds, uint32_t shifter_out, TCG
             gen_adc(t0, t1);
         break;
     case 11: /* sbc */
-        if (conds)
+        if (conds) {
-            gen_helper_sbc_cc(t0, cpu_env, t0, t1);
+            gen_sbc_CC(t0, t0, t1);
-        else
+        } else {
             gen_sub_carry(t0, t0, t1);
+        }
         break;
     case 13: /* sub */
         if (conds)
@@ -9267,10 +9297,11 @@ static void disas_thumb_insn(CPUARMState *env, DisasContext *s)
             }
             break;
         case 0x6: /* sbc */
-            if (s->condexec_mask)
+            if (s->condexec_mask) {
                 gen_sub_carry(tmp, tmp, tmp2);
-            else
+            } else {
-                gen_helper_sbc_cc(tmp, cpu_env, tmp, tmp2);
+                gen_sbc_CC(tmp, tmp, tmp2);
+            }
             break;
         case 0x7: /* ror */
             if (s->condexec_mask) {