tcg/optimize: Improve find_better_copy

Prefer TEMP_CONST over anything else.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

tcg/optimize.c

@@ -122,31 +122,28 @@ static void init_arg_info(TempOptInfo *infos,
 
 static TCGTemp *find_better_copy(TCGContext *s, TCGTemp *ts)
 {
-    TCGTemp *i;
+    TCGTemp *i, *g, *l;
 
-    /* If this is already a global, we can't do better. */
-    if (ts->kind >= TEMP_GLOBAL) {
+    /* If this is already readonly, we can't do better. */
+    if (temp_readonly(ts)) {
         return ts;
     }
 
-    /* Search for a global first. */
+    g = l = NULL;
     for (i = ts_info(ts)->next_copy; i != ts; i = ts_info(i)->next_copy) {
-        if (i->kind >= TEMP_GLOBAL) {
+        if (temp_readonly(i)) {
             return i;
-        }
-    }
-
-    /* If it is a temp, search for a temp local. */
-    if (ts->kind == TEMP_NORMAL) {
-        for (i = ts_info(ts)->next_copy; i != ts; i = ts_info(i)->next_copy) {
-            if (i->kind >= TEMP_LOCAL) {
-                return i;
+        } else if (i->kind > ts->kind) {
+            if (i->kind == TEMP_GLOBAL) {
+                g = i;
+            } else if (i->kind == TEMP_LOCAL) {
+                l = i;
             }
         }
     }
 
-    /* Failure to find a better representation, return the same temp. */
-    return ts;
+    /* If we didn't find a better representation, return the same temp. */
+    return g ? g : l ? l : ts;
 }
 
 static bool ts_are_copies(TCGTemp *ts1, TCGTemp *ts2)