[Bug target/14960] New: -maltivec affects vector return with -mabi=no-altivec

["janis187 at us dot ibm dot com" <gcc-bugzilla at gcc dot gnu dot org>]

The -maltivec instruction should enable the use of the AltiVec
instruction set without affecting how function values are returned.
The documentation in invoke.texi says for -maltivec, "you may also
need to set -mabi=altivec to adjust the current ABI with Altivec
ABI enhancements", but that doesn't appear to be required; two modules
that are both compiled with either -mabi=altivec or -mabi=no-altivec
should be intercallable, even if they pass vector arguments or have
vector return values.  Vector function return values are passed
differently, though, depending on whether -maltivec is specified
instead of which ABI is specified.
                                                                                
This test case fails when either of the two files is compiled with
-maltivec and the other is compiled without it, and both are compiled
with -mabi=no-altivec.  This is for either -m32 or -m64 for
powerpc64-linux, with current GCC 3.4 branch.  I'll try other branches
soon and report what I find.
                                                                                
--- bug.c --------------------------------------------------------------
/* Call a function whose return value is a vector.  Define the data that
   the function will use as input, and verify that it returned the
   correct values.  */
                                                                                
extern __attribute__((vector_size(16))) int foo (void);
                                                                                
__attribute__((vector_size(16))) int i = { 100, 200, 300, 400 };
__attribute__((vector_size(16))) int j = { 10, 20, 30, 40 };
__attribute__((vector_size(16))) int k;
                                                                                
extern void abort (void);
extern __attribute__((vector_size(16))) int foo (void);
                                                                                
void
check ()
{
    union {
        __attribute__((vector_size(16))) int v;
        int i[4];
    } u;
                                                                                
    u.v = k;
    if (u.i[0] != 110 || u.i[1] != 220 || u.i[2] != 330 || u.i[3] != 440)
        abort ();
}
                                                                                
int
main ()
{
    k = foo ();
    check ();
    return 0;
}
--- buga.c -------------------------------------------------------------
/* Return a vector.  */
                                                                                
extern __attribute__((vector_size(16))) int i, j;
                                                                                
__attribute__((vector_size(16))) int
foo (void)
{
    return i + j;
}
------------------------------------------------------------------------

-- 
           Summary: -maltivec affects vector return with -mabi=no-altivec
           Product: gcc
           Version: 3.4.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: target
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: janis187 at us dot ibm dot com
                CC: gcc-bugs at gcc dot gnu dot org
GCC target triplet: powerpc64-unknown-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=14960