Avoid misaligned atomic operations

 Andrew Waterman <waterman@cs.berkeley.edu>

 * fop_n.c (libat_fetch_op): Align address to word boundary.
 (libat_op_fetch): Likewise.

From-SVN: r219954

libatomic/ChangeLog

+2015-01-21  Andrew Waterman <waterman@cs.berkeley.edu>
+
+	* fop_n.c (libat_fetch_op): Align address to word boundary.
+	(libat_op_fetch): Likewise.
+
 2015-01-16  Ilya Verbin  <ilya.verbin@intel.com>
 
 	PR testsuite/64605

libatomic/fop_n.c

@@ -112,9 +112,9 @@ SIZE(C2(libat_fetch_,NAME)) (UTYPE *mptr, UTYPE opval, int smodel)
 
   pre_barrier (smodel);
 
-  wptr = (UWORD *)mptr;
-  shift = 0;
-  mask = -1;
+  wptr = (UWORD *)((uintptr_t)mptr & -WORDSIZE);
+  shift = (((uintptr_t)mptr % WORDSIZE) * CHAR_BIT) ^ SIZE(INVERT_MASK);
+  mask = SIZE(MASK) << shift;
 
   wopval = (UWORD)opval << shift;
   woldval = __atomic_load_n (wptr, __ATOMIC_RELAXED);
@@ -136,9 +136,9 @@ SIZE(C3(libat_,NAME,_fetch)) (UTYPE *mptr, UTYPE opval, int smodel)
 
   pre_barrier (smodel);
 
-  wptr = (UWORD *)mptr;
-  shift = 0;
-  mask = -1;
+  wptr = (UWORD *)((uintptr_t)mptr & -WORDSIZE);
+  shift = (((uintptr_t)mptr % WORDSIZE) * CHAR_BIT) ^ SIZE(INVERT_MASK);
+  mask = SIZE(MASK) << shift;
 
   wopval = (UWORD)opval << shift;
   woldval = __atomic_load_n (wptr, __ATOMIC_RELAXED);