[gcc(refs/users/aoliva/heads/testme)] scoped tables: insert before further lookups

[gcc(refs/users/aoliva/heads/testme)] scoped tables: insert before further lookups

[Alexandre Oliva]

https://gcc.gnu.org/g:e57019a9b7edaeb050f5b2903c959d3010ecb3d1

commit e57019a9b7edaeb050f5b2903c959d3010ecb3d1
Author: Alexandre Oliva <oliva@adacore.com>
Date:   Wed Dec 28 02:21:28 2022 -0300

    scoped tables: insert before further lookups
    
    Avoid hash table lookups between requesting an insert and storing the
    inserted value in avail_exprs_stack.  Lookups before the insert is
    completed could fail to find double-hashed elements.
    
    
    for  gcc/ChangeLog
    
            * tree-ssa-scopedtables.cc
            (avail_exprs_stack::lookup_avail_expr): Finish hash table
            insertion before further lookups.

Diff:
---
 gcc/tree-ssa-scopedtables.cc | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/gcc/tree-ssa-scopedtables.cc b/gcc/tree-ssa-scopedtables.cc
index 6d203ef89ec..3e6e129e7d5 100644
--- a/gcc/tree-ssa-scopedtables.cc
+++ b/gcc/tree-ssa-scopedtables.cc
@@ -259,11 +259,6 @@ avail_exprs_stack::lookup_avail_expr (gimple *stmt, bool insert, bool tbaa_p,
     }
   else if (*slot == NULL)
     {
-      /* If we did not find the expression in the hash table, we may still
-	 be able to produce a result for some expressions.  */
-      tree retval = avail_exprs_stack::simplify_binary_operation (stmt,
-								  element);
-
       /* We have, in effect, allocated *SLOT for ELEMENT at this point.
 	 We must initialize *SLOT to a real entry, even if we found a
 	 way to prove ELEMENT was a constant after not finding ELEMENT
@@ -277,6 +272,11 @@ avail_exprs_stack::lookup_avail_expr (gimple *stmt, bool insert, bool tbaa_p,
       class expr_hash_elt *element2 = new expr_hash_elt (element);
       *slot = element2;
 
+      /* If we did not find the expression in the hash table, we may still
+	 be able to produce a result for some expressions.  */
+      tree retval = avail_exprs_stack::simplify_binary_operation (stmt,
+								  element);
+
       record_expr (element2, NULL, '2');
       return retval;
     }