re PR middle-end/61010 (Infinite recursion in fold)

2014-05-05  Richard Biener  <rguenther@suse.de>

	PR middle-end/61010
	* fold-const.c (fold_binary_loc): Consistently avoid
	canonicalizing X & CST away from a CST that is the mask
	of a mode.

	* gcc.dg/torture/pr61010.c: New testcase.

From-SVN: r210066

gcc/ChangeLog

+2014-05-05  Richard Biener  <rguenther@suse.de>
+
+	PR middle-end/61010
+	* fold-const.c (fold_binary_loc): Consistently avoid
+	canonicalizing X & CST away from a CST that is the mask
+	of a mode.
+
 2014-05-05  Jan-Benedict Glaw  <jbglaw@lug-owl.de>
 
 	* config/picochip/picochip-protos.h (picochip_regno_nregs): Change

gcc/fold-const.c

@@ -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,

gcc/testsuite/ChangeLog

+2014-05-05  Richard Biener  <rguenther@suse.de>
+
+	PR middle-end/61010
+	* gcc.dg/torture/pr61010.c: New testcase.
+
 2014-05-05  Andreas Krebbel  <Andreas.Krebbel@de.ibm.com>
 
 	* gcc.target/s390/leaf-profile.c: New testcase.

gcc/testsuite/gcc.dg/torture/pr61010.c

+/* { dg-do compile } */
+
+int main (void)
+{
+  int a = 0;
+  unsigned b = (a * 64 & 192) | 63U;
+  return 0;
+}