This patch backports the upstream fix in r171347 for a problem caused by
change in volatile bitfield access. This is tested by building the
x86 toolchain with tests and checking that volatile bitfield access worked
on ARM. This is a backport for 4.6 only.
2011-11-16 Doug Kwan <dougk...@google.com>
Backport r171347 from trunk.
2011-03-23 Julian Brown <jul...@codesourcery.com>
* expr.c (expand_expr_real_1): Only use BLKmode for volatile
accesses which are not naturally aligned.
Index: gcc/expr.c
===================================================================
--- gcc/expr.c (revision 181400)
+++ gcc/expr.c (working copy)
@@ -9200,8 +9200,11 @@
&& modifier != EXPAND_CONST_ADDRESS
&& modifier != EXPAND_INITIALIZER)
/* If the field is volatile, we always want an aligned
- access. */
- || (volatilep && flag_strict_volatile_bitfields > 0)
+ access. Only do this if the access is not already naturally
+ aligned, otherwise "normal" (non-bitfield) volatile fields
+ become non-addressable. */
+ || (volatilep && flag_strict_volatile_bitfields > 0
+ && (bitpos % GET_MODE_ALIGNMENT (mode) != 0))
/* If the field isn't aligned enough to fetch as a memref,
fetch it as a bit field. */
|| (mode1 != BLKmode
--
This patch is available for review at http://codereview.appspot.com/5396043
