On Wed, Jan 7, 2009 at 8:30 AM, Ian Lance Taylor <i...@google.com> wrote:
> "H.J. Lu" <hjl.to...@gmail.com> writes:
>
>> Fixing BIGGEST_ALIGNMENT to 16 may require extensive changes.
>> I am thinking to add DEFAULT_ALIGNMENT with
>>
>> #ifndef DEFAULT_ALIGNMENT
>> #define DEFAULT_ALIGNMENT BIGGEST_ALIGNMENT
>> #endif
>>
>> and use it only for attribute((aligned)).
>
> This does need to be done, but DEFAULT_ALIGNMENT is a poorly chosen
> name. It should be something more like ATTRIBUTE_ALIGNED_VALUE.
>
> Ian
>
Here is a patch to implement ATTRIBUTE_ALIGNED_VALUE. OK for trunk?
Thanks.
--
H.J.
---
gcc/
2009-01-07 H.J. Lu <hongjiu...@intel.com>
PR target/38736
* c-common.c (handle_aligned_attribute): Use
ATTRIBUTE_ALIGNED_VALUE instead of ATTRIBUTE_ALIGNED_VALUE for
default alignment value.
* defaults.h (ATTRIBUTE_ALIGNED_VALUE): New.
* config/i386/i386.h (ATTRIBUTE_ALIGNED_VALUE): Likewise.
* doc/extend.texi: Update __attribute__ ((aligned)) with
ATTRIBUTE_ALIGNED_VALUE.
* doc/tm.texi: Document ATTRIBUTE_ALIGNED_VALUE.
gcc/testsuite/
2009-01-07 H.J. Lu <hongjiu...@intel.com>
PR target/38736
* g++.dg/other/pr38736-1.C: New.
* g++.dg/other/pr38736-2.C: Likewise.
* gcc.target/i386/pr38736-1.c: Likewise.
* gcc.target/i386/pr38736-2.c: Likewise.
gcc/
2009-01-07 H.J. Lu <hongjiu...@intel.com>
PR target/38736
* c-common.c (handle_aligned_attribute): Use
ATTRIBUTE_ALIGNED_VALUE instead of ATTRIBUTE_ALIGNED_VALUE for
default alignment value.
* defaults.h (ATTRIBUTE_ALIGNED_VALUE): New.
* config/i386/i386.h (ATTRIBUTE_ALIGNED_VALUE): Likewise.
* doc/extend.texi: Update __attribute__ ((aligned)) with
ATTRIBUTE_ALIGNED_VALUE.
* doc/tm.texi: Document ATTRIBUTE_ALIGNED_VALUE.
gcc/testsuite/
2009-01-07 H.J. Lu <hongjiu...@intel.com>
PR target/38736
* g++.dg/other/pr38736-1.C: New.
* g++.dg/other/pr38736-2.C: Likewise.
* gcc.target/i386/pr38736-1.c: Likewise.
* gcc.target/i386/pr38736-2.c: Likewise.
Index: gcc/doc/extend.texi
===================================================================
--- gcc/doc/extend.texi (revision 4884)
+++ gcc/doc/extend.texi (working copy)
@@ -3697,9 +3697,8 @@ that forces the union to be double-word
As in the preceding examples, you can explicitly specify the alignment
(in bytes) that you wish the compiler to use for a given variable or
structure field. Alternatively, you can leave out the alignment factor
-and just ask the compiler to align a variable or field to the maximum
-useful alignment for the target machine you are compiling for. For
-example, you could write:
+and use @code{ATTRIBUTE_ALIGNED_VALUE} for the target machine you are
+compiling for. For example, you could write:
@smallexample
short array[3] __attribute__ ((aligned));
@@ -3707,11 +3706,11 @@ short array[3] __attribute__ ((aligned))
Whenever you leave out the alignment factor in an @code{aligned} attribute
specification, the compiler automatically sets the alignment for the declared
-variable or field to the largest alignment which is ever used for any data
-type on the target machine you are compiling for. Doing this can often make
-copy operations more efficient, because the compiler can use whatever
-instructions copy the biggest chunks of memory when performing copies to
-or from the variables or fields that you have aligned this way.
+variable or field to @code{ATTRIBUTE_ALIGNED_VALUE}. Doing this can
+often make copy operations more efficient, because the compiler can use
+whatever instructions copy the biggest chunks of memory aligned at
+...@code{attribute_aligned_value} when performing copies to or from the
+variables or fields that you have aligned this way.
When used on a struct, or struct member, the @code{aligned} attribute can
only increase the alignment; in order to decrease it, the @code{packed}
Index: gcc/doc/tm.texi
===================================================================
--- gcc/doc/tm.texi (revision 4884)
+++ gcc/doc/tm.texi (working copy)
@@ -1105,6 +1105,11 @@ Alignment, in bits, a C conformant mallo
provide. If not defined, the default value is @code{BITS_PER_WORD}.
@end defmac
+...@defmac ATTRIBUTE_ALIGNED_VALUE
+Alignment used by the @code{__attribute__ ((aligned))} construct. If
+not defined, the default value is @code{BIGGEST_ALIGNMENT}.
+...@end defmac
+
@defmac MINIMUM_ATOMIC_ALIGNMENT
If defined, the smallest alignment, in bits, that can be given to an
object that can be referenced in one operation, without disturbing any
Index: gcc/defaults.h
===================================================================
--- gcc/defaults.h (revision 4884)
+++ gcc/defaults.h (working copy)
@@ -944,4 +944,9 @@ along with GCC; see the file COPYING3.
((TYPE) ? LOCAL_ALIGNMENT ((TYPE), (ALIGN)) : (ALIGN))
#endif
+/* Alignment value for attribute ((aligned)). */
+#ifndef ATTRIBUTE_ALIGNED_VALUE
+#define ATTRIBUTE_ALIGNED_VALUE BIGGEST_ALIGNMENT
+#endif
+
#endif /* ! GCC_DEFAULTS_H */
Index: gcc/testsuite/gcc.target/i386/pr38736-2.c
===================================================================
--- gcc/testsuite/gcc.target/i386/pr38736-2.c (revision 0)
+++ gcc/testsuite/gcc.target/i386/pr38736-2.c (revision 0)
@@ -0,0 +1,19 @@
+/* PR target/38736 */
+/* { dg-do run } */
+/* { dg-require-effective-target avx } */
+/* { dg-options "-O2 -mavx" } */
+
+extern void abort (void);
+
+struct alignment_test_struct
+{
+ char space[4] __attribute__((__aligned__));
+};
+
+int
+main ()
+{
+ if (__alignof__(struct alignment_test_struct) != 16)
+ abort ();
+ return 0;
+}
Index: gcc/testsuite/gcc.target/i386/pr38736-1.c
===================================================================
--- gcc/testsuite/gcc.target/i386/pr38736-1.c (revision 0)
+++ gcc/testsuite/gcc.target/i386/pr38736-1.c (revision 0)
@@ -0,0 +1,18 @@
+/* PR target/38736 */
+/* { dg-do run } */
+/* { dg-options "-O2" } */
+
+extern void abort (void);
+
+struct alignment_test_struct
+{
+ char space[4] __attribute__((__aligned__));
+};
+
+int
+main ()
+{
+ if (__alignof__(struct alignment_test_struct) != 16)
+ abort ();
+ return 0;
+}
Index: gcc/testsuite/g++.dg/other/pr38736-2.C
===================================================================
--- gcc/testsuite/g++.dg/other/pr38736-2.C (revision 0)
+++ gcc/testsuite/g++.dg/other/pr38736-2.C (revision 0)
@@ -0,0 +1,19 @@
+/* PR target/38736 */
+/* { dg-do run { target i?86-*-* x86_64-*-* } } */
+/* { dg-require-effective-target avx } */
+/* { dg-options "-O2 -mavx" } */
+
+extern void abort (void);
+
+struct alignment_test_struct
+{
+ char space[4] __attribute__((__aligned__));
+};
+
+int
+main ()
+{
+ if (__alignof__(struct alignment_test_struct) != 16)
+ abort ();
+ return 0;
+}
Index: gcc/testsuite/g++.dg/other/pr38736-1.C
===================================================================
--- gcc/testsuite/g++.dg/other/pr38736-1.C (revision 0)
+++ gcc/testsuite/g++.dg/other/pr38736-1.C (revision 0)
@@ -0,0 +1,18 @@
+/* PR target/38736 */
+/* { dg-do run { target i?86-*-* x86_64-*-* } } */
+/* { dg-options "-O2" } */
+
+extern void abort (void);
+
+struct alignment_test_struct
+{
+ char space[4] __attribute__((__aligned__));
+};
+
+int
+main ()
+{
+ if (__alignof__(struct alignment_test_struct) != 16)
+ abort ();
+ return 0;
+}
Index: gcc/c-common.c
===================================================================
--- gcc/c-common.c (revision 4884)
+++ gcc/c-common.c (working copy)
@@ -5906,7 +5906,7 @@ handle_aligned_attribute (tree *node, tr
tree *type = NULL;
int is_type = 0;
tree align_expr = (args ? TREE_VALUE (args)
- : size_int (BIGGEST_ALIGNMENT / BITS_PER_UNIT));
+ : size_int (ATTRIBUTE_ALIGNED_VALUE / BITS_PER_UNIT));
int i;
if (DECL_P (*node))
Index: gcc/config/i386/i386.h
===================================================================
--- gcc/config/i386/i386.h (revision 4884)
+++ gcc/config/i386/i386.h (working copy)
@@ -710,6 +710,10 @@ enum target_cpu_default
/* Maximum stack alignment. */
#define MAX_STACK_ALIGNMENT MAX_OFILE_ALIGNMENT
+/* Alignment value for attribute ((aligned)). It is a constant
+ since it is the part of the ABI. */
+#define ATTRIBUTE_ALIGNED_VALUE 128
+
/* Decide whether a variable of mode MODE should be 128 bit aligned. */
#define ALIGN_MODE_128(MODE) \
((MODE) == XFmode || SSE_REG_MODE_P (MODE))
