diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index e3380b50b8c..46ee450c5fd 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,9 @@
+2007-05-13  Daniel Berlin  <dberlin@dberlin.org>
+
+	Fix PR tree-optimization/31911
+	* tree-ssa-pre.c (phi_translate): Make sure to cache results even
+	if they didn't change the expression.
+
 2007-05-13  Zdenek Dvorak  <dvorakz@suse.cz>
 
 	* tree-scalar-evolution.c (resolve_mixers): Exported.
diff --git a/gcc/tree-ssa-pre.c b/gcc/tree-ssa-pre.c
index 7275acf07fb..46332112cda 100644
--- a/gcc/tree-ssa-pre.c
+++ b/gcc/tree-ssa-pre.c
@@ -1075,8 +1075,8 @@ phi_translate (tree expr, bitmap_set_t set1, bitmap_set_t set2,
 		newexpr->base.ann = NULL;
 		vn_lookup_or_add_with_vuses (newexpr, tvuses);
 		expr = newexpr;
-		phi_trans_add (oldexpr, newexpr, pred, tvuses);
 	      }
+	    phi_trans_add (oldexpr, expr, pred, tvuses);
 	  }
       }
       return expr;
@@ -1188,8 +1188,8 @@ phi_translate (tree expr, bitmap_set_t set1, bitmap_set_t set2,
 		vn_lookup_or_add_with_vuses (newexpr, newvuses);
 	      }
 	    expr = newexpr;
-	    phi_trans_add (oldexpr, newexpr, pred, newvuses);
 	  }
+	phi_trans_add (oldexpr, expr, pred, newvuses);
       }
       return expr;
       break;
@@ -1233,8 +1233,8 @@ phi_translate (tree expr, bitmap_set_t set1, bitmap_set_t set2,
 		vn_lookup_or_add (newexpr, NULL);
 	      }
 	    expr = newexpr;
-	    phi_trans_add (oldexpr, newexpr, pred, NULL);
 	  }
+	phi_trans_add (oldexpr, expr, pred, NULL);
       }
       return expr;
 
@@ -1266,8 +1266,8 @@ phi_translate (tree expr, bitmap_set_t set1, bitmap_set_t set2,
 		vn_lookup_or_add (newexpr, NULL);
 	      }
 	    expr = newexpr;
-	    phi_trans_add (oldexpr, newexpr, pred, NULL);
 	  }
+	phi_trans_add (oldexpr, expr, pred, NULL);
       }
       return expr;