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 --git a/gcc/tree-ssa-scopedtables.cc b/gcc/tree-ssa-scopedtables.cc
index 6d203ef89ecef72cf2ebd15737ac07a6a8ca122a..3e6e129e7d5d380bb3ccde3406aaa89075366a06 100644 (file)
--- 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;
     }