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From: Michael Olbrich <m.olbrich@pengutronix.de>
Date: Wed, 23 Nov 2011 15:43:22 +0100
Subject: [PATCH] Volatile bitfields vs. inline asm memory constraints
taken from trunk.
http://gcc.gnu.org/ml/gcc-patches/2011-03/msg01477.html
gcc/
* expr.c (expand_expr_real_1): Only use BLKmode for volatile
accesses which are not naturally aligned.
Patch taken from Debian
Signed-off-by: Michael Olbrich <m.olbrich@pengutronix.de>
---
gcc/expr.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/gcc/expr.c b/gcc/expr.c
index c4a00aa..03f51f4 100644
--- a/gcc/expr.c
+++ b/gcc/expr.c
@@ -9189,8 +9189,11 @@ expand_expr_real_1 (tree exp, rtx target, enum machine_mode tmode,
&& 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
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