Minor type merging optimization

[Jan Hubicka]

Hi,
while looking at type merging code I noticed that type pairs can be managed
to be ordered by their UIDs.  This save some of hashing overhead in one of
most intensively querried hashes.

Also gimple_lookup_type_leader is hot function that is better to be inlined.

I also wonder, why unionfind algorithm is not used here to maintain the
positive answers?

Bootstrapped/regtested x86_64-linux, OK?

Honza

        * gimple.c (type_pair_hash, type_pair_eq, lookup_type_pair):
        Arrange type pairs to be UID ordered.
        (gimple_lookup_type_leader): Make inline.
Index: gimple.c
===================================================================
--- gimple.c    (revision 173506)
+++ gimple.c    (working copy)
@@ -3240,8 +3240,7 @@ type_pair_hash (const void *p)
   const struct type_pair_d *pair = (const struct type_pair_d *) p;
   hashval_t val1 = pair->uid1;
   hashval_t val2 = pair->uid2;
-  return (iterative_hash_hashval_t (val2, val1)
-         ^ iterative_hash_hashval_t (val1, val2));
+  return iterative_hash_hashval_t (val1, val2);
 }
 
 /* Compare two type pairs pointed-to by P1 and P2.  */
@@ -3251,8 +3250,7 @@ type_pair_eq (const void *p1, const void
 {
   const struct type_pair_d *pair1 = (const struct type_pair_d *) p1;
   const struct type_pair_d *pair2 = (const struct type_pair_d *) p2;
-  return ((pair1->uid1 == pair2->uid1 && pair1->uid2 == pair2->uid2)
-         || (pair1->uid1 == pair2->uid2 && pair1->uid2 == pair2->uid1));
+  return (pair1->uid1 == pair2->uid1 && pair1->uid2 == pair2->uid2);
 }
 
 /* Lookup the pair of types T1 and T2 in *VISITED_P.  Insert a new
@@ -3271,8 +3269,16 @@ lookup_type_pair (tree t1, tree t2, htab
       gcc_obstack_init (ob_p);
     }
 
-  pair.uid1 = TYPE_UID (t1);
-  pair.uid2 = TYPE_UID (t2);
+  if (TYPE_UID (t1) < TYPE_UID (t2))
+    {
+      pair.uid1 = TYPE_UID (t1);
+      pair.uid2 = TYPE_UID (t2);
+    }
+  else
+    {
+      pair.uid1 = TYPE_UID (t2);
+      pair.uid2 = TYPE_UID (t1);
+    }
   slot = htab_find_slot (*visited_p, &pair, INSERT);
 
   if (*slot)
@@ -3280,8 +3286,8 @@ lookup_type_pair (tree t1, tree t2, htab
   else
     {
       p = XOBNEW (ob_p, struct type_pair_d);
-      p->uid1 = TYPE_UID (t1);
-      p->uid2 = TYPE_UID (t2);
+      p->uid1 = pair.uid1;
+      p->uid2 = pair.uid2;
       p->same_p[0] = -2;
       p->same_p[1] = -2;
       *slot = (void *) p;
@@ -3324,7 +3330,7 @@ static GTY((deletable, length("GIMPLE_TY
 /* Lookup an existing leader for T and return it or NULL_TREE, if
    there is none in the cache.  */
 
-static tree
+static inline tree
 gimple_lookup_type_leader (tree t)
 {
   gimple_type_leader_entry *leader;