Re: [PATCH] Speed up qsort in IPA ICF

[Alexander Monakov]

On Thu, 19 Sep 2019, Richard Biener wrote:

> > Good point, there's a tested patch.
> 
> OK.

Hold on, is the new comparator really correct?


@@ -3384,20 +3372,11 @@ sort_congruence_classes_by_decl_uid (const void *a, 
const void *b)
 static int
 sort_congruence_class_groups_by_decl_uid (const void *a, const void *b)
 {
-  const congruence_class_group *g1
-    = *(const congruence_class_group * const *)a;
-  const congruence_class_group *g2
-    = *(const congruence_class_group * const *)b;
-
-  int uid1 = DECL_UID (g1->classes[0]->members[0]->decl);
-  int uid2 = DECL_UID (g2->classes[0]->members[0]->decl);
-
-  if (uid1 < uid2)
-    return -1;
-  else if (uid1 > uid2)
-    return 1;
-  else
-    return 0;
+  const std::pair<congruence_class_group *, int> *g1
+    = *(const std::pair<congruence_class_group *, int> *const *) a;
+  const std::pair<congruence_class_group *, int> *g2
+    = *(const std::pair<congruence_class_group *, int> *const *) b;
+  return g1->second - g2->second;
 }


AFAICT the vec holds pairs, not pointers to pairs, so why does the comparator
cast to a pointer-to-pointer-to-pair? Shouldn't it read

  const std::pair<congruence_class_group *, int> *g1
    = (const std::pair<congruence_class_group *, int> *) a;

Thanks.
Alexander