[gcc r13-564] Check for equivalence after merging relations.

[gcc r13-564] Check for equivalence after merging relations.

[Andrew Macleod]

https://gcc.gnu.org/g:6101a276c34b94f692206739d98aa7faf2e7b2ad

commit r13-564-g6101a276c34b94f692206739d98aa7faf2e7b2ad
Author: Andrew MacLeod <amacleod@redhat.com>
Date:   Mon May 16 21:39:30 2022 -0400

    Check for equivalence after merging relations.
    
    When registering a relation, we need to merge with any existing relation
    before checking if it was an equivalence... otherwise it was not being
    handled properly.
    
            gcc/
            PR tree-optimization/105458
            * value-relation.cc (path_oracle::register_relation): Merge, then check
            for equivalence.
    
            gcc/testsuite/
            * gcc.dg/pr105458.c: New.

Diff:
---
 gcc/testsuite/gcc.dg/pr105458.c | 20 ++++++++++++++++++++
 gcc/value-relation.cc           |  8 ++++----
 2 files changed, 24 insertions(+), 4 deletions(-)

diff --git a/gcc/testsuite/gcc.dg/pr105458.c b/gcc/testsuite/gcc.dg/pr105458.c
new file mode 100644
index 00000000000..eb58bf21f32
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr105458.c
@@ -0,0 +1,20 @@
+/* PR tree-optimization/105458 */
+/* { dg-do compile } */
+/* { dg-options "-O1 -fexpensive-optimizations -fno-tree-dominator-opts " } */
+
+void
+yj (int j4)
+{
+  int t3;
+
+  for (t3 = 0; t3 < 6; ++t3)
+    {
+      short int v4 = t3;
+
+      if (v4 == j4 || v4 > t3)
+        for (;;)
+          {
+          }
+    }
+}
+
diff --git a/gcc/value-relation.cc b/gcc/value-relation.cc
index a93565109f9..85d159f5d96 100644
--- a/gcc/value-relation.cc
+++ b/gcc/value-relation.cc
@@ -1384,16 +1384,16 @@ path_oracle::register_relation (basic_block bb, relation_kind k, tree ssa1,
       fprintf (dump_file, " (root: bb%d)\n", bb->index);
     }
 
+  relation_kind curr = query_relation (bb, ssa1, ssa2);
+  if (curr != VREL_VARYING)
+    k = relation_intersect (curr, k);
+
   if (k == VREL_EQ)
     {
       register_equiv (bb, ssa1, ssa2);
       return;
     }
 
-  relation_kind curr = query_relation (bb, ssa1, ssa2);
-  if (curr != VREL_VARYING)
-    k = relation_intersect (curr, k);
-
   bitmap_set_bit (m_relations.m_names, SSA_NAME_VERSION (ssa1));
   bitmap_set_bit (m_relations.m_names, SSA_NAME_VERSION (ssa2));
   relation_chain *ptr = (relation_chain *) obstack_alloc (&m_chain_obstack,