diff --git a/include/tcg/tcg.h b/include/tcg/tcg.h
index 3168315bb8..e8629b58c8 100644
--- a/include/tcg/tcg.h
+++ b/include/tcg/tcg.h
@@ -976,15 +976,15 @@ int64_t tcg_cpu_exec_time(void);
 void tcg_dump_info(void);
 void tcg_dump_op_count(void);
 
-#define TCG_CT_ALIAS  0x80
-#define TCG_CT_IALIAS 0x40
-#define TCG_CT_NEWREG 0x20 /* output requires a new register */
-#define TCG_CT_CONST  0x02 /* any constant of register size */
+#define TCG_CT_CONST  1 /* any constant of register size */
 
 typedef struct TCGArgConstraint {
-    uint16_t ct;
-    uint8_t alias_index;
-    uint8_t sort_index;
+    unsigned ct : 16;
+    unsigned alias_index : 4;
+    unsigned sort_index : 4;
+    bool oalias : 1;
+    bool ialias : 1;
+    bool newreg : 1;
     TCGRegSet regs;
 } TCGArgConstraint;
 
diff --git a/tcg/tcg.c b/tcg/tcg.c
index 55b2fc3ae3..a8c28440e2 100644
--- a/tcg/tcg.c
+++ b/tcg/tcg.c
@@ -958,7 +958,7 @@ void tcg_context_init(TCGContext *s)
         total_args += n;
     }
 
-    args_ct = g_malloc(sizeof(TCGArgConstraint) * total_args);
+    args_ct = g_new0(TCGArgConstraint, total_args);
 
     for(op = 0; op < NB_OPS; op++) {
         def = &tcg_op_defs[op];
@@ -2197,7 +2197,7 @@ static int get_constraint_priority(const TCGOpDef *def, int k)
     const TCGArgConstraint *arg_ct = &def->args_ct[k];
     int n;
 
-    if (arg_ct->ct & TCG_CT_ALIAS) {
+    if (arg_ct->oalias) {
         /* an alias is equivalent to a single register */
         n = 1;
     } else {
@@ -2260,8 +2260,6 @@ static void process_op_defs(TCGContext *s)
             /* Incomplete TCGTargetOpDef entry. */
             tcg_debug_assert(ct_str != NULL);
 
-            def->args_ct[i].regs = 0;
-            def->args_ct[i].ct = 0;
             while (*ct_str != '\0') {
                 switch(*ct_str) {
                 case '0' ... '9':
@@ -2270,18 +2268,18 @@ static void process_op_defs(TCGContext *s)
                         tcg_debug_assert(ct_str == tdefs->args_ct_str[i]);
                         tcg_debug_assert(oarg < def->nb_oargs);
                         tcg_debug_assert(def->args_ct[oarg].regs != 0);
-                        /* TCG_CT_ALIAS is for the output arguments.
-                           The input is tagged with TCG_CT_IALIAS. */
                         def->args_ct[i] = def->args_ct[oarg];
-                        def->args_ct[oarg].ct |= TCG_CT_ALIAS;
+                        /* The output sets oalias.  */
+                        def->args_ct[oarg].oalias = true;
                         def->args_ct[oarg].alias_index = i;
-                        def->args_ct[i].ct |= TCG_CT_IALIAS;
+                        /* The input sets ialias. */
+                        def->args_ct[i].ialias = true;
                         def->args_ct[i].alias_index = oarg;
                     }
                     ct_str++;
                     break;
                 case '&':
-                    def->args_ct[i].ct |= TCG_CT_NEWREG;
+                    def->args_ct[i].newreg = true;
                     ct_str++;
                     break;
                 case 'i':
@@ -2848,7 +2846,7 @@ static void liveness_pass_1(TCGContext *s)
                     set = *pset;
 
                     set &= ct->regs;
-                    if (ct->ct & TCG_CT_IALIAS) {
+                    if (ct->ialias) {
                         set &= op->output_pref[ct->alias_index];
                     }
                     /* If the combination is not possible, restart.  */
@@ -3665,7 +3663,7 @@ static void tcg_reg_alloc_op(TCGContext *s, const TCGOp *op)
         }
 
         i_preferred_regs = o_preferred_regs = 0;
-        if (arg_ct->ct & TCG_CT_IALIAS) {
+        if (arg_ct->ialias) {
             o_preferred_regs = op->output_pref[arg_ct->alias_index];
             if (ts->fixed_reg) {
                 /* if fixed register, we must allocate a new register
@@ -3688,8 +3686,7 @@ static void tcg_reg_alloc_op(TCGContext *s, const TCGOp *op)
                     reg = ts->reg;
                     for (k2 = 0 ; k2 < k ; k2++) {
                         i2 = def->args_ct[nb_oargs + k2].sort_index;
-                        if ((def->args_ct[i2].ct & TCG_CT_IALIAS) &&
-                            reg == new_args[i2]) {
+                        if (def->args_ct[i2].ialias && reg == new_args[i2]) {
                             goto allocate_in_reg;
                         }
                     }
@@ -3760,10 +3757,9 @@ static void tcg_reg_alloc_op(TCGContext *s, const TCGOp *op)
             /* ENV should not be modified.  */
             tcg_debug_assert(!ts->fixed_reg);
 
-            if ((arg_ct->ct & TCG_CT_ALIAS)
-                && !const_args[arg_ct->alias_index]) {
+            if (arg_ct->oalias && !const_args[arg_ct->alias_index]) {
                 reg = new_args[arg_ct->alias_index];
-            } else if (arg_ct->ct & TCG_CT_NEWREG) {
+            } else if (arg_ct->newreg) {
                 reg = tcg_reg_alloc(s, arg_ct->regs,
                                     i_allocated_regs | o_allocated_regs,
                                     op->output_pref[k], ts->indirect_base);