vector extension bug?

[David Mathog]

I tried to track down the bug mentioned previously in testing my
software SSE2 when compiled with -m64 and ended up removing all 
of the CHECK and my own includes without eliminating the bug.  The test
program works fine with -m32, or with -m64 -msse2, but it fails with
-m64 -mno-sse2.  Here is the greatly reduced gccprob2.c:

8<8<8<8<8<8<8<8<8<8<8<8<8<8<8<8<8<8<8<8<8<8<8<8<8<8<8<8<8<8<
#include <stdio.h> /* for printf */
typedef double    __m128d __attribute__ ((__vector_size__ (16),
__may_alias__));
typedef union
{
  __m128d x;
  double a[2];
} union128d;
#define EMM_FLT8(a)    ((double *)&(a))

void test ( __m128d s1, __m128d s2)
{
printf("test s1 %lf %lf\n",EMM_FLT8(s1)[0],EMM_FLT8(s1)[1]);
printf("test s2 %lf %lf\n",EMM_FLT8(s2)[0],EMM_FLT8(s2)[1]);
}

int main (void)
{
__attribute__ ((aligned (16)))  union128d s1;
  s1.a[0] = 1.0;
  s1.a[1] = 2.0;
printf("s1      %lf %lf\n",s1.a[0],s1.a[1]);
  test (s1.x, s1.x);
}
8<8<8<8<8<8<8<8<8<8<8<8<8<8<8<8<8<8<8<8<8<8<8<8<8<8<8<8<8<8<

Test runs:

% gcc -msse -mno-sse2 -m64   -o foo gccprob2.c
% ./foo  #first value in s2 is wrong
s1      1.000000 2.000000
test s1 1.000000 2.000000
test s2 2.000000 2.000000
% gcc -msse -msse2 -m64   -o foo gccprob2.c
% ./foo
s1      1.000000 2.000000
test s1 1.000000 2.000000
test s2 1.000000 2.000000
% gcc -msse -mno-sse2 -lm -m32   -o foo gccprob2.c
% ./foo
s1      1.000000 2.000000
test s1 1.000000 2.000000
test s2 1.000000 2.000000
% gcc --version
gcc (GCC) 4.4.1
% cat /etc/release
Mandriva Linux release 2010.0 (Official) for x86_64
% cat /proc/cpuinfo | head -10 
processor       : 0
vendor_id       : AuthenticAMD
cpu family      : 15
model           : 33
model name      : Dual Core AMD Opteron(tm) Processor 280
stepping        : 2
cpu MHz         : 1000.000
cache size      : 1024 KB
physical id     : 0
siblings        : 2

Is there something wrong with this program or is this a compiler bug?

Thanks,

David Mathog
mat...@caltech.edu
Manager, Sequence Analysis Facility, Biology Division, Caltech