[gcc r13-3331] Don't set useless relations.

[Andrew Macleod <amacleod@gcc.gnu.org>]

https://gcc.gnu.org/g:fca529517484bf19098ca9efa77e95534086abdc

commit r13-3331-gfca529517484bf19098ca9efa77e95534086abdc
Author: Andrew MacLeod <amacleod@redhat.com>
Date:   Fri Oct 14 14:31:02 2022 -0400

    Don't set useless relations.
    
    The oracle will not register nonssense/useless relations, class
    value_relation shouldn't either.
    
            * value-relation.cc (value_relation::dump): Change message.
            * value-relation.h (value_relation::set_relation): If op1 is the
            same as op2 do not create a relation.

Diff:
---
 gcc/value-relation.cc | 2 +-
 gcc/value-relation.h  | 7 +++++++
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/gcc/value-relation.cc b/gcc/value-relation.cc
index 50fc190a36b..3fb7b96c9e0 100644
--- a/gcc/value-relation.cc
+++ b/gcc/value-relation.cc
@@ -891,7 +891,7 @@ value_relation::dump (FILE *f) const
 {
   if (!name1 || !name2)
     {
-      fprintf (f, "uninitialized");
+      fprintf (f, "no relation registered");
       return;
     }
   fputc ('(', f);
diff --git a/gcc/value-relation.h b/gcc/value-relation.h
index a3bbe1e8157..fa9097a8069 100644
--- a/gcc/value-relation.h
+++ b/gcc/value-relation.h
@@ -349,6 +349,13 @@ value_relation::set_relation (relation_kind r, tree n1, tree n2)
 {
   gcc_checking_assert (TREE_CODE (n1) == SSA_NAME
 		       && TREE_CODE (n2) == SSA_NAME);
+  if (n1 == n2)
+    {
+      related = VREL_VARYING;
+      name1 = NULL_TREE;
+      name2 = NULL_TREE;
+      return;
+    }
   related = r;
   name1 = n1;
   name2 = n2;