[Bug middle-end/61010] [4.8/4.9/4.10 Regression] Infinite recursion in fold

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=61010

--- Comment #7 from Richard Biener <rguenth at gcc dot gnu.org> ---
Like

Index: gcc/fold-const.c
===================================================================
--- gcc/fold-const.c    (revision 209928)
+++ gcc/fold-const.c    (working copy)
@@ -11426,7 +11426,6 @@ fold_binary_loc (location_t loc,
        {
          double_int c1, c2, c3, msk;
          int width = TYPE_PRECISION (type), w;
-         bool try_simplify = true;

          c1 = tree_to_double_int (TREE_OPERAND (arg0, 1));
          c2 = tree_to_double_int (arg1);
@@ -11463,20 +11462,7 @@ fold_binary_loc (location_t loc,
                }
            }

-         /* If X is a tree of the form (Y * K1) & K2, this might conflict
-            with that optimization from the BIT_AND_EXPR optimizations.
-            This could end up in an infinite recursion.  */
-         if (TREE_CODE (TREE_OPERAND (arg0, 0)) == MULT_EXPR
-             && TREE_CODE (TREE_OPERAND (TREE_OPERAND (arg0, 0), 1))
-                           == INTEGER_CST)
-         {
-           tree t = TREE_OPERAND (TREE_OPERAND (arg0, 0), 1);
-           double_int masked = mask_with_tz (type, c3, tree_to_double_int
(t));
-
-           try_simplify = (masked != c1);
-         }
-
-         if (try_simplify && c3 != c1)
+         if (c3 != c1)
            return fold_build2_loc (loc, BIT_IOR_EXPR, type,
                                    fold_build2_loc (loc, BIT_AND_EXPR, type,
                                                     TREE_OPERAND (arg0, 0),
@@ -11866,16 +11852,25 @@ fold_binary_loc (location_t loc,
          && TREE_CODE (arg0) == MULT_EXPR
          && TREE_CODE (TREE_OPERAND (arg0, 1)) == INTEGER_CST)
        {
+         double_int darg1 = tree_to_double_int (arg1);
          double_int masked
-           = mask_with_tz (type, tree_to_double_int (arg1),
+           = mask_with_tz (type, darg1,
                            tree_to_double_int (TREE_OPERAND (arg0, 1)));

          if (masked.is_zero ())
            return omit_two_operands_loc (loc, type, build_zero_cst (type),
                                          arg0, arg1);
-         else if (masked != tree_to_double_int (arg1))
-           return fold_build2_loc (loc, code, type, op0,
-                                   double_int_to_tree (type, masked));
+         else if (masked != darg1)
+           {
+             /* Avoid the transform if arg1 is a mask of some
+                mode which allows further optimizations.  */
+             int pop = darg1.popcount ();
+             if (!(pop >= BITS_PER_UNIT
+                 && exact_log2 (pop) != -1
+                 && double_int::mask (pop) == darg1))
+               return fold_build2_loc (loc, code, type, op0,
+                                       double_int_to_tree (type, masked));
+           }
        }

       /* For constants M and N, if M == (1LL << cst) - 1 && (N & M) == M,