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

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index a3cd478d5b783c571da2da5035e5b04c9ca1f251..18959f6eacb59dc11abaf916388d3dddccf9b908 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,10 @@
+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

diff --git a/gcc/fold-const.c b/gcc/fold-const.c
index 5c2bf256c2a9bee5607b96705ef25e3d1aca392b..65051a12c2ac089c14e61d98e712b5087e0e89f1 100644 (file)
--- a/gcc/fold-const.c
+++ b/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,

diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index ce105724f6960339343ac654723668285787741b..1c9d4d31c662b1d7aceb102e795c7ba4baf5f703 100644 (file)
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+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.

diff --git a/gcc/testsuite/gcc.dg/torture/pr61010.c b/gcc/testsuite/gcc.dg/torture/pr61010.c
new file mode 100644 (file)
index 0000000..ed56539
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/torture/pr61010.c
@@ -0,0 +1,8 @@
+/* { dg-do compile } */
+
+int main (void)
+{
+  int a = 0;
+  unsigned b = (a * 64 & 192) | 63U;
+  return 0;
+}