[Bug c/30128] New: Strange code generated

[terra at gnome dot org]

The program...

/* ------------------------------------------- */
#define GSF_LE_SET_GUINT32(p, dat)                              \
        ((*((char *)(p) + 0) = (char) ((dat))       & 0xff),    \
         (*((char *)(p) + 1) = (char) ((dat) >>  8) & 0xff),    \
         (*((char *)(p) + 2) = (char) ((dat) >> 16) & 0xff),    \
         (*((char *)(p) + 3) = (char) ((dat) >> 24) & 0xff))

void bar (void *);

void
foo (unsigned i)
{
  char buffer[4];
  unsigned len = i + 1;

  GSF_LE_SET_GUINT32 (buffer, len + 1);

  bar (buffer);
}
/* ------------------------------------------- */

...generates the code below.  Note, that there are two additions in the
generated code and that an extra register is used.  It is as-if the least
significant byte is seen as unrelated to the three others.

foo:
        pushl   %ebp
        movl    %esp, %ebp
        subl    $24, %esp
        movl    8(%ebp), %eax
        leal    2(%eax), %edx          <-- one addition into edx
        addl    $2, %eax               <-- second one to eax
        shrl    $8, %eax
        movb    %al, -3(%ebp)
        shrl    $8, %eax
        movb    %al, -2(%ebp)
        shrl    $8, %eax
        movb    %al, -1(%ebp)
        leal    -4(%ebp), %eax
        movb    %dl, -4(%ebp)
        movl    %eax, (%esp)
        call    bar
        leave
        ret


-- 
           Summary: Strange code generated
           Product: gcc
           Version: 4.1.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: terra at gnome dot org
 GCC build triplet: i586-suse-linux
  GCC host triplet: i586-suse-linux
GCC target triplet: i586-suse-linux


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=30128