I am testing the following patch to fix PR51730.
Richard.
2012-01-02 Richard Guenther <rguent...@suse.de>
PR middle-end/51730
* fold-const.c (fold_comparison): Properly canonicalize
tree offset and HOST_WIDE_INT bit position.
* gcc.dg/fold-compare-6.c: New testcase.
Index: gcc/fold-const.c
===================================================================
--- gcc/fold-const.c (revision 182784)
+++ gcc/fold-const.c (working copy)
@@ -8886,6 +8886,14 @@ fold_comparison (location_t loc, enum tr
indirect_base0 = true;
}
offset0 = TREE_OPERAND (arg0, 1);
+ if (host_integerp (offset0, 0)
+ && ((HOST_WIDE_INT) (TREE_INT_CST_LOW (offset0) * BITS_PER_UNIT)
+ / BITS_PER_UNIT
+ == (HOST_WIDE_INT) TREE_INT_CST_LOW (offset0)))
+ {
+ bitpos0 = TREE_INT_CST_LOW (offset0) * BITS_PER_UNIT;
+ offset0 = NULL_TREE;
+ }
}
base1 = arg1;
@@ -8909,6 +8917,14 @@ fold_comparison (location_t loc, enum tr
indirect_base1 = true;
}
offset1 = TREE_OPERAND (arg1, 1);
+ if (host_integerp (offset1, 0)
+ && ((HOST_WIDE_INT) (TREE_INT_CST_LOW (offset1) * BITS_PER_UNIT)
+ / BITS_PER_UNIT
+ == (HOST_WIDE_INT) TREE_INT_CST_LOW (offset1)))
+ {
+ bitpos1 = TREE_INT_CST_LOW (offset1) * BITS_PER_UNIT;
+ offset1 = NULL_TREE;
+ }
}
/* A local variable can never be pointed to by
Index: gcc/testsuite/gcc.dg/fold-compare-6.c
===================================================================
--- gcc/testsuite/gcc.dg/fold-compare-6.c (revision 0)
+++ gcc/testsuite/gcc.dg/fold-compare-6.c (revision 0)
@@ -0,0 +1,12 @@
+/* { dg-do compile } */
+/* { dg-options "-fdump-tree-original" } */
+
+char digs[] = "0123456789";
+int foo (void)
+{
+ int xlcbug = 1 / (&(digs + 5)[-2 + (_Bool) 1] == &digs[4] ? 1 : -1);
+ return xlcbug;
+}
+
+/* { dg-final { scan-tree-dump "xlcbug = 1;" "original" } } */
+/* { dg-final { cleanup-tree-dump "original" } } */
