x86emul: consolidate string insn address increments

Move the looking at EFLAGS.DF into the macro, rendering all call sites
more readable.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

--- a/xen/arch/x86/x86_emulate/x86_emulate.c
+++ b/xen/arch/x86/x86_emulate/x86_emulate.c
@@ -716,8 +716,10 @@ do {
         (reg) = ((reg) & ~((1UL << (_width << 3)) - 1)) |               \
                 (((reg) + _inc) & ((1UL << (_width << 3)) - 1));        \
 } while (0)
-#define register_address_increment(reg, inc) \
-    _register_address_increment((reg), (inc), ad_bytes)
+#define register_address_increment(reg, inc)                            \
+    _register_address_increment(reg,                                    \
+                                _regs.eflags & EFLG_DF ? -(inc) : (inc), \
+                                ad_bytes)
 
 #define sp_pre_dec(dec) ({                                              \
     _register_address_increment(_regs.esp, -(dec), ctxt->sp_size/8);    \
@@ -2942,9 +2944,7 @@ x86_emulate(
             dst.type = OP_MEM;
             nr_reps = 1;
         }
-        register_address_increment(
-            _regs.edi,
-            nr_reps * ((_regs.eflags & EFLG_DF) ? -dst.bytes : dst.bytes));
+        register_address_increment(_regs.edi, nr_reps * dst.bytes);
         put_rep_prefix(nr_reps);
         break;
     }
@@ -2973,9 +2973,7 @@ x86_emulate(
                 goto done;
             nr_reps = 1;
         }
-        register_address_increment(
-            _regs.esi,
-            nr_reps * ((_regs.eflags & EFLG_DF) ? -dst.bytes : dst.bytes));
+        register_address_increment(_regs.esi, nr_reps * dst.bytes);
         put_rep_prefix(nr_reps);
         break;
     }
@@ -3213,12 +3211,8 @@ x86_emulate(
             dst.type = OP_MEM;
             nr_reps = 1;
         }
-        register_address_increment(
-            _regs.esi,
-            nr_reps * ((_regs.eflags & EFLG_DF) ? -dst.bytes : dst.bytes));
-        register_address_increment(
-            _regs.edi,
-            nr_reps * ((_regs.eflags & EFLG_DF) ? -dst.bytes : dst.bytes));
+        register_address_increment(_regs.esi, nr_reps * dst.bytes);
+        register_address_increment(_regs.edi, nr_reps * dst.bytes);
         put_rep_prefix(nr_reps);
         break;
     }
@@ -3233,10 +3227,8 @@ x86_emulate(
              (rc = read_ulong(x86_seg_es, truncate_ea(_regs.edi),
                               &src.val, src.bytes, ctxt, ops)) )
             goto done;
-        register_address_increment(
-            _regs.esi, (_regs.eflags & EFLG_DF) ? -dst.bytes : dst.bytes);
-        register_address_increment(
-            _regs.edi, (_regs.eflags & EFLG_DF) ? -src.bytes : src.bytes);
+        register_address_increment(_regs.esi, dst.bytes);
+        register_address_increment(_regs.edi, src.bytes);
         put_rep_prefix(1);
         /* cmp: dst - src ==> src=*%%edi,dst=*%%esi ==> *%%esi - *%%edi */
         emulate_2op_SrcV("cmp", src, dst, _regs.eflags);
@@ -3263,9 +3255,7 @@ x86_emulate(
         }
         else if ( rc != X86EMUL_OKAY )
             goto done;
-        register_address_increment(
-            _regs.edi,
-            nr_reps * ((_regs.eflags & EFLG_DF) ? -dst.bytes : dst.bytes));
+        register_address_increment(_regs.edi, nr_reps * dst.bytes);
         put_rep_prefix(nr_reps);
         break;
     }
@@ -3275,8 +3265,7 @@ x86_emulate(
         if ( (rc = read_ulong(ea.mem.seg, truncate_ea(_regs.esi),
                               &dst.val, dst.bytes, ctxt, ops)) != 0 )
             goto done;
-        register_address_increment(
-            _regs.esi, (_regs.eflags & EFLG_DF) ? -dst.bytes : dst.bytes);
+        register_address_increment(_regs.esi, dst.bytes);
         put_rep_prefix(1);
         break;
 
@@ -3287,8 +3276,7 @@ x86_emulate(
         if ( (rc = read_ulong(x86_seg_es, truncate_ea(_regs.edi),
                               &dst.val, src.bytes, ctxt, ops)) != 0 )
             goto done;
-        register_address_increment(
-            _regs.edi, (_regs.eflags & EFLG_DF) ? -src.bytes : src.bytes);
+        register_address_increment(_regs.edi, src.bytes);
         put_rep_prefix(1);
         /* cmp: %%eax - *%%edi ==> src=%%eax,dst=*%%edi ==> src - dst */
         dst.bytes = src.bytes;