[PATCH] Fix condition in is_aligning_offset (PR c/61271)

[Marek Polacek <polacek@redhat.com>]

This is one of the issues that -Wlogical-not-parentheses detected.
Interestingly, this code has been added in 2002 (!).  I believe the
logical not there should be just removed; the comment above it says
  /* We must now have a BIT_AND_EXPR with a constant that is one less than
     power of 2 and which is larger than BIGGEST_ALIGNMENT.  */
so if the constant is not one less than power of 2 (exact_log2 returns -1),
we should bail out.

Bootstrapped/regtested on x86_64-linux, ok for trunk?
Should I backport this to 4.9/4.8 after a while?

2014-08-21  Marek Polacek  <polacek@redhat.com>

	PR c/61271
	* expr.c (is_aligning_offset): Remove logical not.

diff --git gcc/expr.c gcc/expr.c
index 920d47b..05d81dc 100644
--- gcc/expr.c
+++ gcc/expr.c
@@ -10721,7 +10721,7 @@ is_aligning_offset (const_tree offset, const_tree exp)
       || !tree_fits_uhwi_p (TREE_OPERAND (offset, 1))
       || compare_tree_int (TREE_OPERAND (offset, 1),
 			   BIGGEST_ALIGNMENT / BITS_PER_UNIT) <= 0
-      || !exact_log2 (tree_to_uhwi (TREE_OPERAND (offset, 1)) + 1) < 0)
+      || exact_log2 (tree_to_uhwi (TREE_OPERAND (offset, 1)) + 1) < 0)
     return 0;
 
   /* Look at the first operand of BIT_AND_EXPR and strip any conversion.

	Marek