[Bug target/48781] New: gcc generate movdqa instructions on unaligned memory address when using -mtune=native -march=native

["tanzhangxi at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48781

           Summary: gcc generate movdqa instructions on unaligned memory
                    address when using -mtune=native -march=native
           Product: gcc
           Version: 4.4.4
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: tanzhangxi@gmail.com


GCC generated the movdaq instructions (requires 16-byte aligned memory address)
on the following simple code.

__uint128_t *mem_pool;
void test(unsigned int addr, unsigned int* data) {
 *(__uint128_t *)data = mem_pool[addr];
}

Both 'mem_pool' and 'data' are not 128-bit aligned.

0000000000000000 <_Z4testjPj>:
   0:   89 ff                   mov    %edi,%edi
   2:   48 8b 05 00 00 00 00    mov    0(%rip),%rax        # 9 <_Z4testjPj+0x9>
   9:   48 c1 e7 04             shl    $0x4,%rdi
   d:   66 0f 6f 04 07          movdqa (%rdi,%rax,1),%xmm0
  12:   66 0f 7f 06             movdqa %xmm0,(%rsi)
  16:   c3                      retq   

I compiled this code with the following command:
g++44 -c test.cpp -O3 -mtune=native -march=native  -o test.o

My target machine is Intel Xeon 5150. It works if don't use  -mtune and -march.
The gcc is shipped with RHEL/Centos 5.6.

Using built-in specs.
Target: x86_64-redhat-linux6E

Configured with: ../configure --prefix=/usr --mandir=/usr/share/man
--infodir=/usr/share/info --with-bugurl=http://bugzilla.redhat.com/bugzilla
--enable-bootstrap --enable-shared --enable-threads=posix
--enable-checking=release --with-system-zlib --enable-__cxa_atexit
--disable-libunwind-exceptions --disable-gnu-unique-object
--enable-languages=c,c++,fortran --disable-libgcj
--with-mpfr=/builddir/build/BUILD/gcc-4.4.4-20100726/obj-x86_64-redhat-linux6E/mpfr-install/
--with-ppl=/builddir/build/BUILD/gcc-4.4.4-20100726/obj-x86_64-redhat-linux6E/ppl-install
--with-cloog=/builddir/build/BUILD/gcc-4.4.4-20100726/obj-x86_64-redhat-linux6E/cloog-install
--with-tune=generic --with-arch_32=i586 --build=x86_64-redhat-linux6E
Thread model: posix
gcc version 4.4.4 20100726 (Red Hat 4.4.4-13) (GCC) 

Btw, if this is not correct, what is the right attribute to decorate a
uint128_t pointer in order to make use of 16-bit aligned SSE2 instructions? The
__atrribute__((align(x))) only works for variables, but not the value pointed
by pointers?