[Bug target/33774] New: Cygwin/mingw do not support 16 byte alignment of struct/union fields

[Bug target/33774] New: Cygwin/mingw do not support 16 byte alignment of struct/union fields

[dannysmith at users dot sourceforge dot net]

The following testcase fails on mingw32 
=======================================================================
typedef int __m128 __attribute__ ((__vector_size__ (16), __may_alias__));

typedef union 
{
   float f[4];
   __m128 m;
} foo;

int test1[__alignof(__m128) >= 16 ? 1 : -1 ];  // OK
int test2[__alignof(foo) >= 16 ? 1 : -1 ]; // Fails: alignof foo = 8
========================================================================

with:
> foo.c:11: error: size of array 'test2' is negative.



The problem is config/i386/cygming.h 

#define BIGGEST_FIELD_ALIGNMENT 64

which is a leftover from a time when this define was necessary and
sufficient to enable 8 byte alignment for doubles--consistent with the
target default MASK_ALIGN_DOUBLE--and when GNU ld could only handle 8
byte alignment.

Currently testing a patch.


-- 
           Summary: Cygwin/mingw do not support 16 byte alignment of
                    struct/union  fields
           Product: gcc
           Version: 4.3.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
        AssignedTo: dannysmith at users dot sourceforge dot net
        ReportedBy: dannysmith at users dot sourceforge dot net
 GCC build triplet: i686-pc-mingw32
  GCC host triplet: i686-pc-mingw32
GCC target triplet: i686-pc-mingw32


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33774

[Bug target/33774] Cygwin/mingw do not support 16 byte alignment of struct/union fields

[patchapp at dberlin dot org]

------- Comment #1 from patchapp at dberlin dot org  2007-10-15 02:15 -------
Subject: Bug number PR target/33774

A patch for this bug has been added to the patch tracker.
The mailing list url for the patch is
http://gcc.gnu.org/ml/gcc-patches/2007-10/msg00853.html


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33774

[Bug target/33774] Cygwin/mingw do not support 16 byte alignment of struct/union fields

[dannysmith at users dot sourceforge dot net]

------- Comment #2 from dannysmith at users dot sourceforge dot net  2007-10-18 21:04 -------
The native compiler MSVC++ does not limit field alignment to 64 bits, but as
documented here 
Windows Data Alignment on IPF, x86, and x64
http://msdn2.microsoft.com/en-us/library/Aa290049(VS.71).aspx

supports at least up to 256-bit field alignment  (see Listing 5 in above
article).


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33774

[Bug target/33774] Cygwin/mingw do not support 16 byte alignment of struct/union fields

[dannysmith at gcc dot gnu dot org]

------- Comment #3 from dannysmith at gcc dot gnu dot org  2007-11-08 20:20 -------
Subject: Bug 33774

Author: dannysmith
Date: Thu Nov  8 20:20:02 2007
New Revision: 130024

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=130024
Log:
        PR target/33774
        * config/i386/cygming.h (BIGGEST_FIELD_ALIGNMENT): Define only if
        IN_TARGET_LIBS.



Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/config/i386/cygming.h


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33774

[Bug target/33774] Cygwin/mingw do not support 16 byte alignment of struct/union fields

[dannysmith at users dot sourceforge dot net]

------- Comment #4 from dannysmith at users dot sourceforge dot net  2007-11-08 20:21 -------
Fixed on trunk.
Danny


-- 

dannysmith at users dot sourceforge dot net changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|                            |FIXED
   Target Milestone|---                         |4.3.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33774