This is the mail archive of the
gcc-patches@gcc.gnu.org
mailing list for the GCC project.
Re: [google] Backport r171347 and r181549 from trunk (strict volatile bitfield) (issue5434084)
> On Tue, Dec 20, 2011 at 04:04:16PM -0800, Brendan Conoboy wrote:
> > On Tue, Dec 20, 2011 at 2:37 PM, Jakub Jelinek <jakub@redhat.com> wrote:
> > > This is ok for 4.6 if it has been sufficiently tested.
> >
> > Okay! Is there any testing you'd like to see beyond the
> > aforementioned success with arm and x86_64 linux?
>
> That is sufficient.
I have checked this in on Doug's behalf (after checking with him, of
course ;) after re-bootstrapping it on an arm host just to be
paranoid.
2011-12-22 Doug Kwan <dougkwan@google.com>
Backport from mainline
2011-03-23 Julian Brown <julian@codesourcery.com>
* expr.c (expand_expr_real_1): Only use BLKmode for volatile
accesses which are not naturally aligned.
2011-11-20 Joey Ye <joey.ye@arm.com>
* expr.c (expand_expr_real_1): Correctly handle strict volatile
bitfield loads smaller than mode size.
Index: testsuite/gcc.dg/volatile-bitfields-1.c
===================================================================
--- testsuite/gcc.dg/volatile-bitfields-1.c (revision 0)
+++ testsuite/gcc.dg/volatile-bitfields-1.c (revision 0)
@@ -0,0 +1,23 @@
+/* { dg-options "-fstrict-volatile-bitfields" } */
+/* { dg-do run } */
+
+extern int puts(const char *);
+extern void abort(void) __attribute__((noreturn));
+
+typedef struct {
+ volatile unsigned short a:8, b:8;
+} BitStruct;
+
+BitStruct bits = {1, 2};
+
+void check(int i, int j)
+{
+ if (i != 1 || j != 2) puts("FAIL"), abort();
+}
+
+int main ()
+{
+ check(bits.a, bits.b);
+
+ return 0;
+}
2011-12-22 Doug Kwan <dougkwan@google.com>
Backport from mainline
2011-11-20 Joey Ye <joey.ye@arm.com>
* gcc.dg/volatile-bitfields-1.c: New.
Index: expr.c
===================================================================
--- expr.c (revision 182634)
+++ expr.c (working copy)
@@ -9186,14 +9186,22 @@ expand_expr_real_1 (tree exp, rtx target
|| (mode1 != BLKmode && ! direct_load[(int) mode1]
&& GET_MODE_CLASS (mode) != MODE_COMPLEX_INT
&& GET_MODE_CLASS (mode) != MODE_COMPLEX_FLOAT
&& 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. Do this in following two situations:
+ 1. the access is not already naturally
+ aligned, otherwise "normal" (non-bitfield) volatile fields
+ become non-addressable.
+ 2. the bitsize is narrower than the access size. Need
+ to extract bitfields from the access. */
+ || (volatilep && flag_strict_volatile_bitfields > 0
+ && (bitpos % GET_MODE_ALIGNMENT (mode) != 0
+ || (mode1 != BLKmode
+ && bitsize < GET_MODE_SIZE (mode1) * BITS_PER_UNIT)))
/* If the field isn't aligned enough to fetch as a memref,
fetch it as a bit field. */
|| (mode1 != BLKmode
&& (((TYPE_ALIGN (TREE_TYPE (tem)) < GET_MODE_ALIGNMENT (mode)
|| (bitpos % GET_MODE_ALIGNMENT (mode) != 0)
|| (MEM_P (op0)