[gcc r13-1813] Allow registering same SSA name relations in oracle.

[gcc r13-1813] Allow registering same SSA name relations in oracle.

[Aldy Hernandez]

https://gcc.gnu.org/g:4a36b4e1fe405fe347d57c39f8e23ac8a6c57263

commit r13-1813-g4a36b4e1fe405fe347d57c39f8e23ac8a6c57263
Author: Aldy Hernandez <aldyh@redhat.com>
Date:   Wed Jul 20 20:36:54 2022 +0200

    Allow registering same SSA name relations in oracle.
    
    Similarly to what we did for the relation oracle, but for the path
    oracle.  This was found while working on frange, where we can test for
    x == x while checking for NANness.
    
    Tested on x86-64 Linux.
    
    gcc/ChangeLog:
    
            * value-relation.cc (value_relation::set_relation): Remove assert.
            (path_oracle::register_relation): Exit when trying to register
            same SSA name relations.

Diff:
---
 gcc/value-relation.cc | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/gcc/value-relation.cc b/gcc/value-relation.cc
index bd344253af3..a447021214f 100644
--- a/gcc/value-relation.cc
+++ b/gcc/value-relation.cc
@@ -667,8 +667,6 @@ private:
 inline void
 value_relation::set_relation (relation_kind r, tree n1, tree n2)
 {
-  gcc_checking_assert (SSA_NAME_VERSION (n1) != SSA_NAME_VERSION (n2)
-		       || r == VREL_EQ);
   related = r;
   name1 = n1;
   name2 = n2;
@@ -1449,6 +1447,11 @@ void
 path_oracle::register_relation (basic_block bb, relation_kind k, tree ssa1,
 				tree ssa2)
 {
+  // If the 2 ssa_names are the same, do nothing.  An equivalence is implied,
+  // and no other relation makes sense.
+  if (ssa1 == ssa2)
+    return;
+
   if (dump_file && (dump_flags & TDF_DETAILS))
     {
       value_relation vr (k, ssa1, ssa2);